title: A randomised RSA study of Peri-Apatite HA coating of a total knee prosthesis. Postoperative clodronate decreases prosthetic migration: 4–year follow-up of a randomized radiostereometric study of 50 total knee patients Kinematics and early migration in single-radius mobile- and fixed-bearing total knee prostheses. Influence of cement viscosity and cement mantle thickness on migration of the Exeter total hip prosthesis. Periprosthetic bone mineral density and fixation of the uncemented CLS stem related to different weight bearing regimes The effect of Palamed® G bone cement on early migration of tibial components in total knee arthroplasty Influence of polyethylene constraint on tibial component fixation in total knee arthroplasty: follow-up report after 5 years. Acetabular reconstruction in developmental hip dysplasia using reinforcement ring with a hook Immediate weight bearing after uncemented total hip arthroplasty with an anteverted stem: A prospective randomized comparison using radiostereometry Cemented tibial component fixation performs better than cementless fixation Highly Cross-Linked Polyethylene in Cemented THA: Randomized Study Of 61 Hips Factors associated with excessive migration in bone impaction hip revision surgery: a radiostereometric analysis study. Comparison of cementing techniques of the tibial component in total knee replacement Periapatite May Not Improve Micromotion of Knee Prostheses in Rheumatoid Arthritis Preoperative gait patterns and BMI are associated with tibial component migration Comparison of micromotion in mobile bearing and posterior stabilized total knee prostheses Celecoxib does not appear to affect prosthesis fixation in total knee replacement Increased bone turnover as reflected by biochemical markers in patients with potentially unstable fixation of the tibial component Computer assisted versus conventional cemented total knee prostheses alignment accuracy and micromotion of the tibial component Cemented versus uncemented fixation of the femoral component of the NexGen CR total knee replacement in patients younger than 60 years: a prospective randomised controlled RSA study. Early Migration Pattern of the Uncemented CLS Stem in Total Hip Arthroplasties A randomized study on migration of the Spectron EF and the Charnley flanged 40 cemented femoral components using radiostereometric analysis at 2 years No Increased Migration in Cups with Ceramic-on-Ceramic Bearing: An RSA Study Failure of the Uncoated Titanium ProxiLock Femoral Hip Prosthesis Influence of Design Variations on Early Migration of a Cemented Stem in THA Uncemented HA-coated Implant is the Optimum Fixation for TKA in the Young Patient Effect of bioactive coating of the tibial component on migration pattern in uncemented total knee arthroplasty: a randomized RSA study of 14 knees presented according to new RSA-guidelines Excessive distal migration of fiber-mesh coated femoral stems The effects of different weight-bearing regimes on press-fit cup stability: a randomised study with five years of follow-up using radiostereometry Migration Pattern of a Short Femoral Neck Preserving Stem The seven-year wear of highly cross-linked polyethylene in total hip arthroplasty: a double-blind, randomized controlled trial using radiostereometric analysis. Randomised controlled trial comparing early migration of two collarless polished cemented stems using radiostereometric analysis. Local peroperative treatment with a bisphosphonate improves the fixation of total knee prostheses: A randomized, double-blind radiostereometric study of 50 patients The effect of early weight bearing on migration pattern of the uncemented CLS stem in total hip arthroplasty. Early migration characteristics of a hydroxyapatite-coated femoral stem: an RSA study Bone morphology in relation to the migration of porous-coated anatomic knee arthroplasties : a roentgen stereophotogrammetric and histomorphometric study in 23 knees. Flat vs. concave tibial joint surface in total knee arthroplasty: Randomized evaluation of 39 cases using radiostereometry Migration of the acetabular component: Effect of cement pressurization and significance of early radiolucency Two-year migration results of the ReCap hip resurfacing system—a radiostereometric follow-up study of 23 hips Addition of Fluoride to Acrylic Bone Cement Does Not Improve Fixation of a Total Hip Arthroplasty Stem Cemented versus hydroxyapatite fixation of the femoral component of the Freeman-Samuelson total knee replacement: a radiostereometric analysis. Stepwise introduction of a bone-conserving osseointegrated hip arthroplasty using RSA and a randomized study: I. Preliminary investigations—52 patients followed for 3 years Fixation of Total Knee Arthroplasty Improved by Mobile-bearing Design Second-generation Highly Cross-linked X3™ Polyethylene Wear: A Preliminary Radiostereometric Analysis Study The next generation of acetabular shell design and bearing surfaces. Wear and migration of highly cross-linked and conventional cemented polyethylene cups with cobalt chrome or Oxinium femoral heads: a randomized radiostereometric study of 150 patients. Increase in early polyethylene wear after sterilization with ethylene oxideRadiostereometric analyses of 201 total hips Segment choice and cup stability influence wear measurements using radiostereometric analysis: a radiostereometric study comparing wear measured by markers in the polyethylene with markers in the periacetabular bone. The creep and wear of highly cross-linked polyethylene: a three-year randomised, controlled trial using radiostereometric analysis. Palamed G compared with Palacos R with gentamicin in Charnley total hip replacement. A randomised, radiostereometric study of 60 HIPS. The Influence of a Suction Device on Fixation of a Cemented Cup using RSA Bioactive cement or ceramic/porous coating vs. conventional cement to obtain early stability of the acetabular cup. Randomised study of 96 hips followed with radiostereometry. A new uncemented hydroxyapatite-coated femoral component for the treatment of femoral neck fractures: two-year radiostereometric and bone densitometric evaluation in 50 hips. Mobile vs. fixed meniscal bearing in total knee replacement: a randomised radiostereometric study. Migration of the femoral stem after impaction bone grafting. First results of an ongoing, randomised study of the exeter and elite plus femoral stems using radiostereometric analysis. Less wear with aluminium-oxide heads than cobalt-chrome heads with ultra high molecular weight cemented polyethylene cups: A ten-year follow-up with radiostereometry Comparison of the uncemented Cone and the cemented Bimetric hip prosthesis in young patients with osteoarthritis: An RSA, clinical and radiographic study Hydroxyapatite and tricalcium phosphate-coated cups with and without screw fixation: a randomized study of 64 hips. Tibial component fixation in porous- and hydroxyapatite-coated total knee arthroplasty: a radiostereo metric evaluation of migration and inducible displacement after 5 years. Effect of augmented cup fixation on stability, wear, and osteolysis: a 5-year follow-up of total hip arthroplasty with RSA. Minimally invasive surgery vs conventional exposure using the Miller-Galante unicompartmental knee arthroplasty: a randomized radiostereometric study. Concave versus posterior-stabilized tibial joint surface in total knee arthroplasty: randomized evaluation of 47 knees. Bone cement with reduced proportion of monomer in total hip arthroplasty: Preclinical evaluation and randomized study of 47 cases with 5 years' follow-up Fixation of the tibial component using CMW-1 or Palacos bone cement with gentamicin: Similar outcome in a randomized radiostereometric study of 51 total knee arthroplasties Mobile Bearings Do Not Improve Fixation in Cemented Total Knee Arthroplasty Stepwise introduction of a bone-conserving osseointegrated hip arthroplasty using RSA and a randomized study: II. Clinical proof of concept—40 patients followed for 2 years Is Removal of Subchondral Bone Plate Advantageous in Cemented Cup Fixation?: A Randomized RSA Study No difference in migration or wear between cemented low-profile cups and standard cups : A randomized radiostereographic study of 53 patients over 3 years Two-year radiostereometric analysis evaluation of femoral head penetration in a challenging population of young total hip arthroplasty patients. Evaluation of a Femoral Stem with Reduced Stiffness: A Randomized Study with Use of Radiostereometry and Bone Densitometry The introduction period of unicompartmental knee arthroplasty is critical: a clinical, clinical multicentered, and radiostereometric study of 251 Duracon unicompartmental knee arthroplasties. The migration patterns of two versions of the Furlong cementless femoral stem: a randomised, controlled trial using radiostereometric analysis. Clodronate prevents prosthetic migration: A randomized radiostereometric study of 50 total knee patients Randomized comparison between 3 surface treatments of a single anteverted stem design: 84 hips followed for 5 years. Differences in stability and bone remodeling between a customized uncemented hydroxyapatite coated and a standard cemented femoral stem A randomized study with use of radiostereometry and bone densitometry. Does highly cross-linked polyethylene wear less than conventional polyethylene in total hip arthroplasty? A double-blind, randomized, and controlled trial using roentgen stereophotogrammetric analysis. Evaluation of Boneloc. Chemical and mechanical properties, and a randomized clinical study of 30 total hip arthroplasties. VersaBond bone cement prospective randomized study of the clinical properties of a new bone cement in total knee replacement.
abstract: BACKGROUND In total knee replacement , sound early fixation of the prosthesis is crucial for achieving a good long-term result and for minimising the risk of loosening . Various types of prosthetic material , different surface textures and shapes and the incorporation of screws or pegs have been used to achieve good fixation , particularly in the uncemented knee . Hydroxyapatite ( HA ) coating of prosthetic joint components is another technique used to enhance early stability and so to improve the longevity of the prosthesis-bone fixation . HA ceramic coatings are mostly plasma sprayed onto the fixation surface of the implant . Plasma spraying is largely a ' line of sight ' technique and as such there are difficulties involved when covering three-dimensional planes , such as porous beaded fixation surfaces typically found on several knee prostheses . The objective of this study was to assess the clinical performance of the solution-deposited HA coating , Peri-Apatite , with regard to its ability to stimulate an endurable and stable implant fixation . PATIENTS AND METHODS We r and omised 60 patients into two groups ; one group received the porous coated prosthesis with solution-deposited HA  , and the other group received a prosthesis without HA . Radiostereometric examination was used as the primary tool for measuring migration in the prosthetic components . RESULTS There was a lower incidence of early subsidence in the Peri-Apatite group . At 24 months there were no differences in clinical scorings or maximal total point motion . CONCLUSION Addition of solution-deposited HA coating appears to provide better early stable fixation in a porous coated knee prosthesis Background We have previously reported that 6 months of oral treatment with clodronate reduced the migration of the NexGen total knee prosthesis during the first postoperative year , as measured by  radiostereometry ( RSA ) . We now report the 4-year results . Methods This was a double-blind r and omized study , using RSA with maximal total point motion ( MTPM ) . Results With analysis according to the “ intention to treat ” principle , the only remaining difference between the groups at 4 years was reduced rotation around the transverse axis ( a secondary variable ) in the clodronate group . However , 3 patients ( all clodronate )  did not take any tablet after surgery . If they are excluded , there was an almost statistically significant difference between the groups at 4 years regarding MTPM from baseline , with the clodronate group showing 25 % less migration . From 1 to 4 years , there was no difference in migration rate by MTPM , but there was a continuous increase in rotation around the transverse axis in the controls , which differed from the clodronate group . There were no cases of aseptic loosening . 2 patients had migration of more than 1.3 mm from baseline to 4 years ; neither of them had taken clodronate . The others had migration of less than 0.9 mm . Interpretation Because migration was clearly reduced by clodronate during the first postoperative year , and there was still a difference at 4 years when analyzed per protocol , it appears likely that this treatment can diminish the risk of loosening . The difference in the number of outliers also points in this direction , and may be more relevant than mean migration values BACKGROUND The mobile-bearing variant of a single-radius design is assumed to provide more freedom of motion compared to the fixed-bearing variant because the insert does not restrict the natural movements of the femoral component . This would reduce the contact stresses and wear which in turn may have a positive effect on the fixation of the prosthesis to the bone and thereby decreases the risk for loosening . The aim of this study was to evaluate early migration of the tibial component and kinematics of a mobile-bearing and fixed-bearing total knee prosthesis of the same single-radius design . METHODS Twenty Triathlon single-radius posterior-stabilized knee prostheses were implanted ( 9 mobile-bearing and 11 fixed-bearing ) .  Fluoroscopy and roentgen stereophotogrammetric analysis ( RSA ) were performed 6 and 12 months post-operatively . FINDINGS The 1 year post-operative RSA results showed considerable early migrations in 3 out of 9 mobile-bearing patients and 1 out of 11 fixed-bearing patients . The range of knee flexion was the same for the mobile-bearing and fixed-bearing group . The mobile insert was following the femoral component during motion . INTERPRETATION Despite the mobile insert following the femoral component during motion , and therefore performing as intended , no kinematic advantages of the mobile-bearing total knee prosthesis were seen . The fixed-bearing knee performed as good as the mobile-bearing knee and maybe even slightly better based on less irregular kinematics and less early migrations The effect of bone cement viscosity and cement mantle thickness on the migration of the Exeter  total hip prosthesis  was studied in a prospect i ve , r and omized , double-blind clinical Roentgen Stereophotogrammetric Analysis study . Forty-one cemented total hip arthroplasty in 39 patients were included and r and omized into a low/medium Simplex P cement group and a high-viscosity Simplex AF cement group . At time of stem introduction , 5 minutes after mixing , the Simplex AF was more viscous than Simplex P. No statistical difference existed between the 2 cement groups , for neither translation nor rotation migration data . Subsidence of the stem at 2-year follow-up was 1.1 + /- 0.56 mm for Simplex AF cement and 1.5 + /- 1.00 mm for Simplex P cement . The mean rotation of the acetabular components about the sagittal axis was 1.7 degrees + /- 3.8 degrees in the Simplex AF group and 0.7 degrees + /- 2.1 degrees for the Simplex P group . No effect of cement mantle thickness on migration of neither the acetabular cups nor the femoral stems was found . Although there were no differences in migration data for the cups and the stems , 2 acetabular cups in the Simplex AF group ( almost 10 % ) were revised because of mechanical loosening . Because of these findings , we suggest caution before using this new high-viscosity bone cement for fixation of acetabular components Background and purpose There is no consensus on the best rehabilitation regime after uncemented total hip arthroplasty . Theoretically , bone ingrowth into the implant should benefit from initial partial weight bearing . We investigated whether the degree of postoperative weight bearing influences the periprosthetic bone mineral density ( BMD ) and /or the stability of the CLS stem . Patients and methods 38 patients received an uncemented CLS stem  and were  r and omized  to either unrestricted postoperative weight bearing or to partial weight bearing for 3 months .  Periprosthetic BMD was measured in the 7 Gruen zones with DXA and the stability of the femoral stem was assessed by radiostereometric analysis ( RSA ) after surgery and at 3 , 12 , 24 , and 60 months . Results Periprosthetic BMD was not influenced by the type of postoperative weight bearing . BMD was reduced by 8–15 % in all Gruen zones at 3 months . Restoration toward initial BMD was observed in all zones except in zone 7 ( calcar region ) , where BMD was reduced by 22 % at 5 years . Immediate weight bearing after surgery had no influence on the stability of the CLS stem , as assessed by RSA . Interpretation Immediate full weight bearing after uncemented total hip arthroplasty is safe . There is no difference in the periprosthetic BMD or in stability of the stem as measured by RSA compared to partial weight bearing for 3 months . BMD is reduced by more than 20 % in the calcar region around a CLS stem after 5 years Abstract Objective : Migration of the tibial component in total knee arthroplasty ( TKA ) is subject of many studies using roentgen stereophotogrammetric analysis ( RSA ) . In previous studies of cemented and uncemented tibial components , high migration values were found . Improvements in cementing technique , prosthetic design and pre-coating techniques reduced these values as shown in more recent studies . Material and subjects : A total of 35 patients were initially included in the study and operated on between 12/1999 and 10/2000 . All patients received a NexGen ® TKA cemented into the proximal tibia using Palamed ® G bone cement . The implants and the tibial metaphysis were marked with st and ard tantalum markers . Radiostereometric analysis was performed post-operatively and after 3 , 6 and 12 months using a st and ard digital radiostereometric analysis . Functional parameters were assessed using the Knee Society Score ( KSS ) clinical rating system . Results : There were no complications and failures within the first year . After 1 year radiostereometric measurements of the translational parameters along and the rotational parameters around the x- , y- and z-axis revealed : X-Trans –0.19 mm , Y-Trans + 0.02 mm , Z-Trans + 0.08 mm , X-Rot + 0.26 ° , Y-Rot –0.35 ° , Z-Rot + 0.09 ° . The maximum total point motion was + 0.96 mm and the mean maximum subsidence was –0.23 mm . Except for anterior-posterior , medio-lateral stability and extension leg all endpoints of the KSS clinical rating system showed a significant improvement . Conclusions : After 12 months , the use of Palamed ® G bone cement in total knee arthroplasty was demonstrated to be safe . Both the clinical and radiostereometric results were good and comparable to the results reported in other RSA studies in cemented total knee arthroplasty The influence of articulating surface design of AMK total knee prosthesis ( DePuy , Johnson & Johnson ) on migration and radiographic outcome at 5 years was evaluated . The knees were r and omly allocated to receive a flat or a concave insert with retention of the posterior cruciate ligament when preoperative deformity was less severe and either a concave or a posterior-stabilized insert with resection of the posterior cruciate ligament when deformity was more pronounced . In 64 knees , migration was measured with radiostereometry . The posterior-stabilized component displayed more varus-valgus tilting than the concave insert . Other statistically significant differences in migration were not seen . Radiolucent lines were frequently seen without differences between prosthesis groups We followed prospect ively 27 patients with severe acetabular bone-stock deficiencies due to developmental dysplasia of the hip . Mean preoperative patient age was 56 ( 34–78 ) years , mean Harris hip score was 31 ( 16–66 ) points and pre-operative mean acetabular angle of Sharp was 47 ° ( 34 ° –61 ° ) . Operative acetabular reconstruction was performed in 28 hips using reinforcement ring with a hook placed in the true acetabulum and autologous bone grafting . A 2-year clinical and radiological follow-up was available in 27 hips . Mean Harris hip score improved to 91 ( 70–100 ) points . There were no clinical or radiological signs of aseptic loosening in 25 hips , and the bone graft was radiologically incorporated in all hips . In 24 hips , a radiostereometric analysis showed low rates of non-progressive translation and rotation in 21 reinforcement rings . Three rings showed progressive translation and /or rotation at the 2-year follow-up and were rated probably loose . RésuméNous avons suivi 27 malades avec des déficiences acétabulaires sévères dû à une dysplasie de développement de la hanche . L’âge moyen préopératoire des malades était de 56 ans ( 34–78 ) , le score moyen de Harris était de 31 points ( 16–66 ) et l’angle moyen de Sharp préopératoire était de 47 ° ( 34 ° –61 ° ) . La reconstruction acétabulaire a été exécutée dans 28 hanches en utilisent un anneau de renforcement avec crochet , placé dans le paléo-cotyle , avec greffe osseuse autologue . Un suivi clinique et radiologique de 2 années était disponible pour 27 hanches . Le score moyen de Harris a été amélioré à 91 points ( 70–100 ) . Il n’y avait pas de signe clinique ou radiologique de descellement aseptique dans 25 hanches et la greffe osseuse était incorporée dans toutes les hanches . Dans 24 hanches une analyse radiostéréométrique a montré un faible taux de translation et de rotation , non progressive , de 21 anneaux de renforcement . Trois anneaux ont montré une translation et/ou une rotation progressive au cours du suivi de 2 années et ont été considérés comme descellés Background In uncemented total hip arthroplasty with hydroxyapatite coating , early weight bearing is frequently practice d but there is still not much evidence to support this recommendation . Method In a prospect i ve r and omized study we evaluated the effect of partial and full weight bearing after  cementless total hip arthroplasty ( ABG ; Stryker-Howmedica ) using radiostereometric analysis ( RSA ) . Between February 1996 and February 2000 , 43 consecutive patients ( mean age 53 ( 41–63 ) years , 23 women ) with hip osteoarthrosis received an uncemented and hydroxyapatite-coated prosthesis with an anteverted stem . All patients were operated in a st and ardized way by three experienced surgeons and they were r and omized to partial ( P ) or full ( F ) weight bearing during the first 6 weeks after surgery . The patients in the partial weight bearing group were equipped with a pressuresensitive insole signaling when their load exceeded the prescribed weight limit . Results At 3-month follow-up , the mean proximal (+)/ distal ( - ) migration of the stem was -0.14 mm ( -1.93– 0.11 ) in group P and -0.31 mm ( -4.30–0.16 ) in group F ( p = 0.6 ) . At 1-year follow-up , the mean migration was –0.17 mm ( -2.18–0.21 ) and -0.28 mm ( -4.31–0.11 ) , respectively ( p = 0.9 ) . There was no significant difference in stem rotations either ( p < 0.2 ) . The cup translations , rotations , and femoral head penetration were similar in the two groups ( p < 0.1 ) . There were no re-operations during the first year . Interpretation We did not find any adverse effect of full weight bearing immediately after operation , which justifies use of this regimen after uncemented total hip arthroplasty of the ABG type Background The question whether the tibial component of a total knee arthroplasty  should be fixed to bone with or without bone cement has not yet been definitely answered . We studied movements between the tibial component and bone by radiostereometry ( RSA ) in total knee replacement ( TKR ) for 3 different types of fixation : cemented fixation ( C-F ) , uncemented porous fixation ( UC-F ) and uncemented porous hydroxyapatite fixation ( UCHA-F ) . Patients 116 patients with osteoarthrosis , who had 146 TKRs , were included in 2 r and omized series . The first series included 86 unilateral TKRs stratified into 1 of the 3 types of fixation . The second series included 30 patients who had simultaneous bilateral TKR surgery , and who were stratified into 3 subgroups of pairwise comparisons of the 3 types of fixation . Results After 5 years 2 knees had been revised , neither of which were due to loosening . 1 UCHA-F knee in the unilateral series showed a large and continuous migration and a poor clinical result , and is a pending failure . The C-F knees rotated and migrated less than UC-F and UCHA-F knees over 5 years . UCHA-F  migrated less than UC-F after 1 year . Interpretation Cementing of the tibial component offers more stable bone-implant contact for 5 years compared to uncemented fixation . When using uncemented components , however , there is evidence that augmenting a porous surface with hydroxyapatite may mean less motion between implant and bone after the initial postoperative year Highly cross-linked polyethylene ( PE ) has been introduced as an alternative bearing material in total hip arthroplasty ( THA ) because of high wear resistance in laboratory tests but the clinical experience of this material is limited . We evaluated a highly cross-linked PE ( warm irradiated adiabatic melting , absorbed dose , 95 kGy ) in a r and omized study of cemented THAs . Cups of the same design but made of conventionally gamma irradiated PE ( absorbed dose , 25–40 kGy ) constituted the control group . Sixty-one hips ( 30 women , 30 men ) with a median age of 55 years ( range , 35–70 years ) were included . All patients received a Spectron stem with 28-mm CoCr head . Radiostereometric examinations with the patient supine or st and ing were done at regular intervals . Wear was measured with the patient in the supine position from the first postoperative week , whereas examinations done with the patient st and ing were initiated 3 months after the operation . Dual xray absorptiometry and conventional radiography were used to evaluate the bone mineral density and the radiolucencies around the acetabular component .  Fifty-two patients ( 53 hips ; 25 highly cross-linked , 28 control ) have been followed up for 2 years . At the 2-year followup , the highly cross-linked cups showed 50 % reduction of proximal wear compared with the control group , when the patients were studied st and ing . When evaluated supine , the difference in proximal wear did not reach significance . The migration of the socket , the relative changes of periprosthetic bone mineral density , and the progression of radiolucencies between the immediately postoperative followup and 2-year followup did not differ . Highly cross-linked PE showed increase resistance to wear . Different mechanical properties of the two types of PE studied did not alter the performance of the cup in terms of fixation , periprosthetic bone loss , and radiographic appearance . However , the followup is short and these results are preliminary A prospect i ve radiostereometric analysis ( RSA ) study of 18 patients with cemented revision hip surgery and impaction grafting with an Exeter stem  was done with a follow-up of 2 years for all patients . All factors that could influence migration ( ie , micromotion ) of the stem were analyzed with a repeated measurements analysis of variance . Two groups could be identified : a stable group and a continuous migrating group . Two factors significantly influenced micromotion during the follow-up measurements . The first factor was the Paprosky classification ( the bigger the defect , the higher the micromotion ) . The second factor was cement mantle defects in > or = 1 Gruen zones . The migrating hip stems had more Gruen zones with cement mantle defects ( 45 % ) compared with the stable prostheses ( 21 % ) . The effect of the first factor on micromotion was limited and probably clinical ly less relevant . Because the cement mantle defects found in this study were caused by poor instrumentation , the second factor stresses the importance of good instrumentation , which is essential to make this technically dem and ing technique effective in creating a stable stem-allograft construct in the defective femoral canal A few studies have shown that cementing the stem enhances fixation of the tibial baseplate in total knee replacement ( TKR ) . Even the horizontal technique has been shown to provide good fixation . We used radiostereometry to study migration of the tibial component in 30 knees operated with Profix TKR . The knees were r and omised for either complete ( both under the baseplate and around the stem ) or horizontal ( only under the baseplate ) cementing of the tibial component . At two years the tibial baseplate rotated externally a median of 0.18 ° in the uncemented stem group and internally a median of 0.23 ° in the cemented stem group . The tibial baseplate subsided 0.14 mm in the cemented stem group , and no translation was seen in the uncemented stem group . The differences in migration were small and probably without clinical significance . The findings do not favour either of the cementing techniques in TKR.RésuméPeu d’études ont démontré que la fixation cimentée de la queue améliorait la fixation du plateau tibial dans les prothèses totales du genou . Par ailleurs , les fixations horizontales ont également montré une bonne fixation . Nous avons utilisé la radiostéréométrie pour étudier la migration du composant tibial dans 30 genoux de type Profix . Les genoux ont été r and omisés cimentation sous le plateau et autour de la queue ou cimentation horizontale uniquement sous le plateau . À 2 ans le plateau tibial présente une rotation externe de 0,18 ° dans les PTG avec une queue non cimentée et une rotation interne moyenne de 0,23 ° dans le groupe des queues cimentées . La base du plateau tibial s’enfonce de 0,14 mm dans le groupe des queues cimentées et il n’y a pas de translation dans le groupe des queues non cimentées . En conclusion , la différence au niveau de la migration est minime et sans signification clinique . Cette étude ne permet pas de choisir dans les prothèses totales du genou l’une des deux techniques de cimentation Prosthesis migration in bone inevitably occurs in cemented and uncemented total knee arthroplasty tibial components . Cemented design s as the gold st and ard give immediate fixation whereas cementless design s need a period of bone ingrowth onto the surface irregularities of the implants . The addition of bioactive coatings may enhance this process of ingrowth . A controlled r and omized prospect i ve RSA study was carried out on 26 Duracon implants in a rheumatoid arthritis patient group to evaluate the effect of a periapatite coating on the fixation of the tibial tray . The coated and the noncoated groups were matched for sex , age , body mass index , and HSS Knee Score . Stage of preoperative joint destruction and preoperative and postoperative mechanical leg axis showed no differences . We saw no differences in migration between the two groups , but a trend for lesser translations along and rotations about all three axes in the periapatite group . The periapatite-coated components showed a lower variance in subsidence than did the uncoated components . Both groups also showed a high variance in anterior tilting of the components . The cementless PA-coated Duracon prosthesis used in patients with RA may provide improved fixation of tibial components although we could not demonstrate improvement in this small controlled series . Level of Evidence : Therapeutic Level II . See the Guidelines for Authors for a complete description of levels of evidence Background and purpose There is no st and ard for patient triage in  total knee arthroplasty ( TKA ) based on joint functional characteristics . This is largely due to the lack of objective postoperative measurement of success in TKA in terms of function and longevity , and the lack of knowledge of preoperative metrics that influence outcome . We examined the association between the preoperative mechanical environment of the patients knee joint during gait and the post-TKA stability of the tibial component  as measured with  radiostereometric analysis ( RSA ) .  Methods 37 subjects were recruited out of a larger r and omized RSA trial .  3-dimensional gait analysis was performed in the preoperative week . Longitudinal RSA data were gathered postoperatively at 6 months and 1 year . Results We found a statistically significant association between the pattern of the knee adduction moment during gait preoperatively and the total migration of the implant at 6 months postoperatively . A substantial proportion of the variability in the total postoperative tibial component migration ( R2 = 0.45 ) was explained by a combination of implant type , preoperative knee joint loading patterns during gait , and body mass index at 6 months postoperatively . The relationships did not remain statistically significant at 1 year postoperatively . Interpretation Our findings support the hypothesis that preoperative functional characteristics of patients , and particularly joint loading patterns during activities of daily living , are important for outcome in TKA . This represents a first step in the development of predictive models of objective TKA outcome based on preoperative patient characteristics , which may lead to better treatment strategies . Clinical Trials.gov ( NCT00405379 Background On theoretical grounds mobile bearing total knees should reduce the micromotion of the tibial component relative to the bone . Patients and methods We used radiostereometric analysis to measure the three-dimensional micromotion in  42 tibial components  during 2 years of follow-up . The patients had been r and omized as to whether they would receive a mobile bearing ( MB ) or posterior stabilized ( PS ) design .  We expected that the MB knee would facilitate dissipation of forces from the prosthesis-bone interface by the motion of the bearing and by load sharing with the soft tissues , leading to less micromotion . In the PS design s , limited free rotation caused by the campost articulation might cause additional stress at the bone-prosthesis interface . Results We found no significant differences between the MB and PS group at the 2-year follow-up evaluation with respect to Knee Society scores and radiographic results . The PS group had a higher variability in subsidence and anterior-posterior tilting of the component than the MB group . Interpretation The low variability of the data in the MB knee prosthesis group suggests that this design is more predictable and forgiving with respect to micromotion of the tibial component Background and purpose After joint replacement , a repair process starts at the interface between bone and cement . If this process is disturbed , the prosthesis may never become rigidly fixed to the bone , leading to migration— and with time , loosening . Cox-2 inhibitors are widely used as postoperative analgesics , and have adverse effects on bone healing . This could tamper prosthesis fixation . We investigated whether celecoxib , a selective Cox-2 inhibitor , increases prosthesis migration in total knee replacement ( TKR ) . Methods 50 patients were r and omized to either placebo or celecoxib treatment , 200 mg twice daily , for 3 weeks after TKR  ( NexGen ; Zimmer ) . Maximum total point motion ( MTPM ) of the tibial component was measured after 2 years using radiostereometric analysis ( RSA ) . In addition , range of motion , pain , and , subjective outcome were evaluated . Results No differences in prosthesis migration , pain scores , range of motion , and subjective outcome were found after 2 years . Confidence intervals were narrow . Interpretation It is unlikely that Celecoxib increases the risk of loosening , and it may be used safely in conjunction with TKR Introduction Whether biochemical markers of bone metabolism can be used in assessing the conditions of implant fixation is unknown . In this study , the serum levels of three bone markers were measured prospect ively in patients undergoing total knee arthroplasty ( TKA ) to determine if patients with different fixation conditions of the tibial component showed any differences in the levels of the markers . Material s and methods The fixation of the tibial component in 40 knees ( 40 patients , 14 male and 26 female , average age 71 years ) was assessed by radiostereometric analysis ( RSA ) , and based upon the pattern of migration , implants with stable fixation ( n=25 ) and potentially unstable fixation ( n=15 ) were identified . Serum levels of carboxyterminal propeptide of type I procollagen ( PICP ) , osteocalcin ( OC ) and cross-linked carboxyterminal telopeptide of type I collagen ( ICTP ) were assessed and compared between the two fixation groups . Blood sample s were obtained preoperatively ( baseline ) and repeated postoperatively at 1 week , 3 , 6 , 12 , and 24 months . Results The baseline levels of the markers were statistically the same ( p>0.05 ) between the two fixation groups . Postoperatively , ICTP levels in the unstable group were significantly higher than in the stable group from 6 to 24 months ( p=0.02 ) . Levels of OC in the unstable group were higher at 12 and 24 months compared with the stable group , reaching statistical significance only at 12 months ( p=0.03 ) . No difference in the levels of PICP was found between the two groups . Conclusion The findings indicate a more active bone turnover probably at the bone-cement/implant interface in knees with potentially unstable fixation . It reveals the potential value for biochemical markers in monitoring implant fixation and aseptic loosening and suggests a possibility for improving implant fixation by drugs which inhibit osteolysis We evaluated the influence of CT-free or CT-based computer assisted orthopaedic surgery ( CAOS ) on the alignment of total knee prostheses ( TK ) and micromotion of tibial components . This r and omised study compared 19 CT-free , 17 CT-based CAOS TK , and a matched control group of 21 conventionally placed TK .  Using Roentgen stereophotogrammetric analysis ( RSA ) the migration was measured . The alignment and component positions were measured on radiographs . No significant difference in leg and tibial component alignment was present between the three groups . A significant difference was found for micromotion in subsidence , with the conventional group having a mean of 0.16 mm , compared to the CT-free group at 0.01 mm and the CT-based group at −0.05 mm . No clinical significant difference in alignment was found between CAOS and conventionally operated TK . More subsidence of the tibial component was seen in the conventional group compared to both CAOS groups at two year follow-up . RésuméBut de l'étude : Evaluer l'influence de la navigation avec ou sans scanner sur l'alignement des prothèses totales du genou et sur la micromobilité du composant tibial . Matériel et méthode : nous avons réalisé une étude r and omisée comparant 19 prothèses naviguées sans scanner , 17 prothèses naviguées avec scanner , croisées avec un groupe contrôle de 21 patients avec mise en place d'une prothèse par voie conventionnelle . Nous avons utilisé la méthode RSA pour mesurer la migration . L'alignement et les composants étaient mesurés sur les radiographies . Résultats : il n'y a pas de différence significative au niveau de l'alignement des composants pour les trois groupes , par contre il existe une différence significative en ce qui concerne la migration . Dans le groupe conventionnel celle-ci est d'environ 0,16 mm , 0,01 mm dans le groupe navigation sans scanner et 0,05 mm dans le groupe navigation avec scanner . Conclusion : il n'y a pas de différence significative dans l'alignement des prothèses totales du genou lors de la mise en place d'une prothèse totale avec ou sans navigation par contre , il existe une micromobilité avec petite migration du composant tibial si l'on compare le groupe conventionnel avec les groupes navigués The optimal mode of femoral fixation in total knee arthroplasty ( TKA ) remains controversial , especially for the young patient . In a prospect i ve r and omised study we compared the magnitude and pattern of the fixation of cemented versus uncemented femoral components during 2 years in patients younger than 60 years . Forty-one knees in 41 patients were r and omised to receive a NexGen ( Zimmer , Warsaw , USA  ) cruciate-retaining TKA with either a cemented or an uncemented non HA-coated femoral component . The patients were examined by radiostereometric analysis ( RSA ) , as well as clinical and radiological evaluation . The magnitude and pattern of migration as measured by RSA did not differ significantly between the cemented and uncemented fixation during the 2-year follow-up , nor were there any differences between the groups in clinical parameters . These findings suggest that an uncemented and non HA-coated femoral component may behave equally as well as a cemented one in the long-term We performed this investigation to determine the possible migration starting immediately after surgery and the effect of different weightbearing regimens on the migration pattern of an uncemented hip stem ( CLS ) . Stem migration was determined with radiostereometry analysis with baseline when the patients still were anesthetized . Subsequent examinations were done up to 1 year . Twenty-nine patients ( mean age , 55 years ; range , 26 - 63 years ) were r and omized to either unrestricted weightbearing combined with intensive physiotherapy  from the first day after surgery or to partial weightbearing and a conservative training regimen for the first 3 months after surgery . At 1 week , subsidence was −0.03 mm in the unrestricted weightbearing group and 0.01 mm in the partial weightbearing group . At 1 year , subsidence was 1.01 mm in the unrestricted weightbearing group and 0.51 mm in the partial weightbearing group . One patient in the unrestricted weightbearing group had revision surgery because of aseptic loosening at 1.5 years after surgery . The CLS stem did not have any migration from the end the surgery until 1 week , but there was small migration from 1 week to 3 months after which the stem remained stable . The degree of early weightbearing did not affect the migration pattern . Level of Evidence : Level I , therapeutic study ( r and omized study ) . See the Guidelines for Authors for a complete description of levels of evidence Background and purpose We performed a r and omized study to determine the migration patterns of the Spectron EF femoral stem and to compare them with those of the Charnley stem , which is regarded by many as the gold st and ard for comparison of implants due to its extensive documentation . Patients and methods 150 patients with a mean age of 70 years were r and omized , single-blinded , to receive either a cemented Charnley flanged 40 monoblock , stainless steel , vaquasheen surface femoral stem with a 22.2-mm head ( n = 30 ) or a cemented Spectron EF modular , matte , straight , collared , cobalt-chrome femoral stem with a 28-mm femoral head and a roughened proximal third of the stem ( n = 120 ) . The patients were followed with repeated radiostereometric analysis for 2 years to assess migration . Results At 2 years , stem retroversion was 2.3 ° and 0.7 ° ( p < 0.001 ) and posterior translation was 0.44 mm and 0.17 mm ( p = 0.002 ) for the Charnley group ( n = 26 ) and the Spectron EF group ( n = 74 ) , respectively . Subsidence was 0.26 mm for the Charnley and 0.20 mm for the Spectron EF ( p = 0.5 ) . Interpretation The Spectron EF femoral stem was more stable than the Charnley flanged 40 stem in our study when evaluated at 2 years . In a report from the Norwegian arthroplasty register , the Spectron EF stem had a higher revision rate due to aseptic loosening beyond 5 years than the Charnley . Initial stability is not invariably related to good long-term results . Our results emphasize the importance of prospect i ve long-term follow-up of prosthetic implants in clinical trials and national registries and a stepwise introduction of implants Ceramic-on-ceramic hip replacements might stress the bone interface more than a metal-polyethylene because of material stiffness , microseparation , and sensitivity to impingement . To ascertain whether this potentially increased stress caused an increased cup migration we compared a ceramic-on-ceramic with a metal-on-polyethylene implant for cup migration . Sixty one patients ( 61 hips ) undergoing THA for osteoarthritis were  r and omized to ceramic on ceramic ( Ce/Ce ) or cobalt-chromium on cross-linked polyethylene bearings ( PE ) in the same uncemented cup shell . Migration was followed with RSA . At 2 years we observed similar mean cup translations in the 3 directions ( 0.07 - 0.40 mm vs. 0.05 - 0.31 mm , Ce/Ce vs. PE ) , as well as similar rotations around the 3 axes ( 0.31 - 0.92 ° vs. 0.57 - 1.40 ° ) . WOMAC and SF-36 scores were also similar and no radiolucent lines or osteolysis found . The large migration seen in some cups in both implant groups will require close monitoring to ascertain the reasons . Mean proximal wear of the polyethylene liners measured 0.016 mm between 2 and 24 months . Our data suggest there is no increased cup migration in the ceramic-on-ceramic implant compared with the metal-on-polyethylene , and they seem an equally safe choice . However , the low wear measured with the more versatile and less expensive cross-linked polyethylene makes it a strong contender . Levels of Evidence : Therapeutic Level I. See the Guidelines for Authors for a complete description of levels of evidence New prostheses should be evaluated for stability and clinical performance . In a prospect i ve r and omized clinical trial , we implanted 22 titanium ( Ti ) and 20 hydroxyapatite-coated ( HA ) ProxiLock femoral hip prostheses during total hip arthroplasty in 42 patients . The patients were followed for 24 months with clinical , radiographic and radiostereometric analysis . Full weightbearing was allowed immediately postoperatively . One patient with a titanium stem was lost to followup . During the first two months , 34 of the 41 stems subsided and /or rotated towards retroversion , regardless of stem type . At the 24-month followup 35 of the 41 prostheses were either fully stabilized ( 16 HA and 11 Ti stems ) or had clinical irrelevant migration ( four HA and four Ti stems ) . Six Ti prostheses showed continuous migrations with maximums of 4.7 mm translation and 12.2 ° retroversion ; four of these were revised , the other two had no clinical complaints . Clinical relevance : The migration pattern we found indicates insufficient primary fixation of the ProxiLock stem in an immediate full weightbearing protocol . The HA coating improves the secondary stability of the prosthesis compared to the uncoated stem . Early migration is associated with an increased risk of possible future loosening and revision , and therefore we discontinued the use of this prosthesis . Level of Evidence : Therapeutic Level I. See Guidelines for Authors for a complete description of levels of evidence The clinical results of using different cemented stems in total hip arthroplasty may vary because of shape , surface finish , and choice of metal alloy . Less is known about the influence of size and offset using one and the same design . Data from 140 patients ( 140 hips ) of a cohort constituting 197 patients ( 231 hips ) implanted with cemented Spectron Primary stems were extracted from patients studied in four r and omized studies primarily design ed for other purpose s. Stem size ( 1 , 2 , 3 , or larger ) , normal/extra offset , neck length and true offset ( horizontal length between the stem and head center of the inserted modular implant ) were recorded in millimeters . The radiographic appearance of the cementing was grade d on the immediate postoperative radiograph according to Barrack . The patients were examined with  radiostereometric analysis  of  stem migration  for a 2-year followup period . Stem Size 1 ( the smallest ) showed an insignificant increase in subsidence compared with the bigger sizes . Using stepwise linear regression analysis , the quality of the cementing ( Barrack C2 ) was the only parameter that had any certain influence of the subsidence at 2 years . Stem size 2 tended to show minimum valgus alignment and sizes 1 and 3 and bigger showed minimum varus tilting . Our findings suggest that placement of the stem with the tip against the posterior cortex ( C2 ) and stem size influence the primary fixation in different ways . This effect is small , however , indicating that further confirmation with longer followup is necessary . Level of Evidence : Therapeutic Level II-1 ( prospect i ve cohort study ) . See the Guidelines for Authors for a complete description of levels of evidence Fixation of the tibial component in total knee arthroplasty in younger patients remains controversial . We evaluate the results of three different types of fixation of the Profix total knee arthroplasty  in a r and omized controlled trial of 97 consecutive knees ( 85 patients ) with osteoarthrosis or inflammatory arthritis with 2-year followup of all patients . We r and omized patients to three different types of fixation of the tibial component : cemented , uncemented ( HA coated ) with screws , or uncemented ( HA coated ) without screws . We performed clinical evaluations and radiostereometric analysis at 6 weeks , and 3 , 6 , 12 and 24 months postoperatively . The knees in the uncemented groups migrated more than those in the cemented group during the first 3 months , but at 2 years we observed no differences . The uncemented implants  displayed all migration within the first 3 months . The cemented implants did not stabilize but had continuously increasing migration during the followup . Cementless implants without screws  did not migrate more than implants with screws and displayed similar pattern of migration , indicating screws do not improve fixation .  Uncemented fixation using hydroxyapatite-coated implants without screws seems to be the best solution for the younger patient . Level of Evidence : Therapeutic Level I. See the Guidelines for Authors for a complete description of levels of evidence Background Bioactive coating of uncemented  total knee arthroplasty ( TKA ) is believed to increase bone ingrowth and enhance early fixation of the TKA . In a prospect i ve r and omized study using radiostereometric analysis ( RSA ) we examined migrations of the tibial implant , in an uncemented TKA with and without bioactive coating . The study was performed according to new RSA guidelines , and focus was put on some important method ological issues . Material s and methods Twenty-three patients with osteoarthrosis of the knee received an uncemented Duracon TKA either with bioactive ( hydroxyapatite or periapatite ) coating ( + HA ) or without bioactive coating ( −HA ) . Patients had RSA examinations postoperatively and at 3 , 6 and 12 months . Nine patients were excluded during the study result ing in 14 knees for final analysis . Results At 12 months follow-up we found no significant differences in migrations between the two groups . However , in general the −HA group migrated more than the + HA group , and we found a significant larger variation in migration pattern in the −HA group . In the + HA group the tibia component stabilized after 6 months , whereas the −HA group showed continuous migration . Subsidence and posterior tilt were the main migration patterns in both groups . Conclusions Bioactive coating of TKA seems to enhance early stabilization of the tibia component . Similar results are found in previous studies Background The surface texture , localization , and magnitude of the surface material applied to the femoral stem can facilitate bone ingrowth and influence the survival of total hip arthroplasties . Clinical and radiographic studies have shown superior bone ingrowth in proximally porous-coated stems with a diaphyseal grit-blasted surface in comparison to a smooth diaphyseal surface . Surface textures — especially porous surface material —have been suggested to have a sealing effect against migration of polyethylene debris along the implant-bone interface and to reduce the inflammatory response , leading to a prolonged implant survival . Patients and methods Between 2004 and 2006 , we conducted a r and omized , controlled trial ( RCT ) involving 50 patients with non-inflammatory arthritis . They received either a distally tapered , extended coated stem or a straight , proximally coated stem . During surgery , tantalum markers were inserted into the greater and lesser trochanter . Implant migration was evaluated at 3 , 12 , and 24 months postoperatively by radiostereometric analysis . The primary endpoint was stem migration 2 years after surgery . Results All femoral components in both groups showed pronounced distal translation , with the highest rate of translation occurring between 0 and 3 months . After 2 years , the mean distal translation was 2.67 ( 95 % CI : –3.93 to –1.42 ) mm for the tapered , extended coated stem and 1.80 ( –2.45 to –1.15 ) mm for the straight , proximally coated stem . Half of the tapered , extended coated stems and two-thirds of the straight , proximally coated stems had migrated more than 1 mm . No difference between the 2 stems could be seen with regard to translation or rotation at any time point . After 2 years , 2 hips have been reoperated due to mechanical loosening of the stem . Interpretation An excessive amount of migration of both stem types was seen 2 years postoperatively . It is of vital importance to follow this patient cohort since radiostereometric analysis is known to be predictive of late implant failure , especially in this study where pronounced early migration was observed . We recommend longer follow-up of both stem types Purpose There is little evidence to support immediate weight bearing after uncemented total hip arthroplasty ( THA ) . Methods Thirty-seven patients with unilateral osteoarthritis of the hip received a press-fit cup . Cup stability was assessed with radiostereometry ( RSA ) over five years . Patients were r and omised to immediate full weight bearing , or partial weight bearing for three months . Results At five years , we found no difference in micromotion as assessed with radiostereometry . Numerically , there was more proximal translation and increased inclination with immediate weight bearing , but these values barely exceeded the precision limit for the method . Pooled data for the two groups revealed translations of 0.1 - 0.3 mm and rotations of 0.2 - 0.3 ° over the five year follow-up period . Conclusions We found no adverse effects of immediate weight bearing after THA in relation to stability of these press-fit cups . Early mobilisation might have other advantages The CFP stem represents a short collared neck-retaining stem with very proximal metaphyseal anchoring along the calcar combined with up-to- date metallurgy . Despite theoretical advantages , the stability and clinical outcome are unknown . We prospect ively measured the migration pattern of this new stem and cup . Twenty-six patients ( 26 hips ) with a mean age of 54 years ( range , 40 - 66 years ) underwent THA  and were followed for 2 years with  radiostereometry , radiographs , and clinical scores . The stem showed some early retroversion ( mean , SEM 0.6 ° , 0.3 ) , but stabilized before 1 year . Subsidence ( 0.05 mm , 0.06 ) and varus-valgus tilting ( 0.03 ° , 0.01 ) were low . We observed no bone loss in the calcar region . Factors related to patients , implant design , and implantation did not predict migration patterns . The two-dimensional wear of the ceramic/conventional articulation was 0.09 mm at 2 - 24 months . The low migration of this short neck preserving stem suggests a favorable long-term outcome but longer followup is needed to substantiate this prediction . This design might become an alternative to st and ard stems and hip resurfacing . Level of Evidence : Therapeutic Level IV . See The Guidelines for Authors for a complete description of levels of evidence BACKGROUND The use of highly cross-linked polyethylene is now commonplace in total hip arthroplasty . Hip simulator studies and short-term in vivo measurements have suggested that the wear rate of highly cross-linked polyethylene is significantly less than that of conventional ultra-high molecular weight polyethylene . However , long-term data to support its use are limited . The aim of this study was to compare the intermediate-term steady-state wear of highly cross-linked polyethylene compared with that of conventional ultra-high molecular weight polyethylene acetabular liners in a prospect i ve , double-blind , r and omized controlled trial with use of radiostereometric analysis . METHODS Fifty-four patients were r and omized to receive hip replacements with either conventional ultra-high molecular weight polyethylene acetabular liners ( Zimmer ) or highly cross-linked polyethylene liners ( Longevity ; Zimmer ) . All patients received a cemented , collarless , polished , tapered femoral component ( CPT ; Zimmer ) and an uncemented acetabular component ( Trilogy ; Zimmer ) . Clinical outcomes were assessed and the three-dimensional penetration of the head into the socket was determined for a minimum of seven years . Linear regression was used to calculate the steady-state wear rate following the creep-dominated penetration seen during the first year . RESULTS At a minimum of seven years postoperatively , the mean total femoral head penetration was significantly lower in the highly cross-linked polyethylene group ( 0.33 mm ; 95 % confidence interval [ CI ] , ±0.10 mm ) than it was in the ultra-high molecular weight polyethylene group ( 0.55 mm ; 95 % CI , ±0.10 mm ) ( p = 0.005 ) . The mean steady-state wear rate  of highly cross-linked polyethylene was 0.005 mm/yr ( 95 % CI , ±0.015 mm/yr ) , compared with 0.037 mm/yr ( 95 % CI , ±0.019 mm/yr ) for conventional ultra-high molecular weight polyethylene ( p = 0.007 ) . No patient in the highly cross-linked polyethylene group had a wear rate above the osteolysis threshold of 0.1 mm/yr , compared with 9 % of patients in the ultra-high molecular weight polyethylene group . CONCLUSIONS This study demonstrates that highly cross-linked polyethylene has a significantly lower steady-state wear rate compared with that of conventional ultra-high molecular weight polyethylene . Longer-term follow-up is required to determine if this will translate into improved clinical performance and longevity of these implants This was a safety study where the hypothesis was that the newer- design CPCS femoral stem would demonstrate similar early clinical results and micromovement to the well-established Exeter stem . Both are collarless , tapered , polished cemented stems , the only difference being a slight lateral to medial taper with the CPCS stem . A total of 34 patients were enrolled in a single-blinded r and omised controlled trial in which 17 patients received a dedicated radiostereometric CPCS stem and 17 a radiostereometric Exeter stem .  No difference was found in any of the outcome measures pre-operatively or post-operatively between groups . At two years , the mean subsidence for the CPCS stem was nearly half that seen for the Exeter stem ( 0.77 mm ( -0.943 to 1.77 ) and 1.25 mm ( 0.719 to 1.625 ) , respectively ; p = 0.032 ) . In contrast , the mean internal rotation of the CPCS stem was approximately twice that of the Exeter ( 1.61 degrees ( -1.07 degrees to 4.33 degrees ) and 0.59 degrees ( 0.97 degrees to 1.64 degrees ) , respectively ; p = 0.048 ) . Other migration patterns were not significantly different between the stems . The subtle differences in design s may explain the different patterns of migration . Comparable migration with the Exeter stem suggests that the CPCS design will perform well in the long term Background Postoperative migration of a joint prosthesis is related to the risk of late loosening . We have previously reported that oral treatment with clodronate reduced migration of the cemented NexGen total knee prosthesis during the first postoperative year , as measured by radiostereometry ( RSA ) . Oral bisphosphonate treatment is sometimes unpleasant , and local treatment will enable higher local concentrations . We now report the results of local peroperative treatment with another bisphosphonate , ib and ronate , with the same prosthesis . Methods This is a double-blind , r and omized study of 50 patients using RSA with maximal total point motion ( MTPM ) as primary effect variable . 1 mg ib and ronate ( 1 mL ) or 1 mL saline was applied to the tibial bone surface 1 min before cementation . RSA examination was done on the first postoperative day , and at 6 , 12 , and 24 months . Results One ib and ronate-treated patient died of unrelated causes , and 1 control patient refused to come for follow-up , leaving 24 patients in each group for analysis . There were no cases of aseptic loosening . By repeated measures ANOVA , migration ( MTPM ) was reduced by local application of ib and ronate ( p = 0.006 ) . The effect was most pronounced at 6 months , with a reduction from 0.45 to 0.32 mm ( 95 % CI for reduction : 0.04–0.21 mm ) . At 12 months , the migration from the postoperative examination was reduced from 0.47 to 0.36 mm ( 95 % CI for reduction : 0.02–0.20 mm ) . At 24 months , the reduction was from 0.47 to 0.40 mm ( 95 % CI : -0.01–0.16 mm ) . Interpretation This is the first study to show improvement of prosthesis fixation by local pharmacological treatment in humans . The treatment appears to be safe , cheap , and easy to perform . However , the improvement in postoperative stability was not greater than with systemic clodronate treatment Forty-two patients ( younger than 65 years ) with osteoarthritis were operated on with an uncemented CLS stem and r and omized to early unrestricted weight bearing combined with intensive physiotherapy or to partial weight bearing combined with self-training . Radiostereometric analysis showed 1.2 ( + 0.11 to -6.76 ) mm subsidence of the stem at 24 months in both groups . There was no significant difference in the migration pattern between the unrestricted and partial weight bearing groups . Actual loading on the operated leg , measured with the F-scan system , did not influence the migration of the stem . There was a strong correlation between the average subsidence at 3 and 24 months ( r = 0.96 ) . Early full weight bearing and active rehabilitation can be used for the uncemented CLS stem without increased risk of early loosening Measurement of early stem subsidence can be used to predict the likelihood of long-term femoral component loosening and clinical failure . Data that examines the early migration pattern of clinical ly proven stems will provide clinicians with useful baseline data with which to compare new stem design s. This study was performed to evaluate the early migration pattern of a hydroxyapatite-coated press-fit femoral component that has been in use for over ten years . We enrolled 30 patients who underwent THA for osteoarthritis . The median age was 70 years ( range , 55–80 years ) . Patients were clinical ly assessed using the Harris hip score .  Radiostereometric analysis was used to evaluate stem migration at three to four days , six months , one year and two years . We observed a mean subsidence of 0.73 mm at six months , 0.62 mm at one year and 0.58 mm at two years and a mean retroversion of 1.82 ° at six months , 1.90 ° at one year and 1.59 ° at two years . This data suggests that subsidence is confined to the first six months after which there was no further subsidence . The results from this study can be compared with those from novel cementless stem design s to help predict the long-term outcome one may expect from new cementless stem design The quality of the subchondral bone in total knee arthroplasty ( TKA ) may be important for the outcome . We correlated a histomorphologic analysis of the prosthetic bone bed to micromotion as analyzed by  roentgen stereophotogrammetric analysis ( RSA ) .  Twenty-three knees , both osteo- and rheumatoid arthritic were studied . The mean migration after 1 year was 1 mm ( 0.21 - 2.68 ) , with no correlation to the bone variables or diagnosis . One patient underwent revision after 3 years because of pain . One patient underwent revision after 15 years because of aseptic loosening . This patient appeared stable according to changes in maximum total point motion ( MTPM ) , but the prosthesis migrated continuously according to segment motion . Prosthetic migration increased after 10 years , zones started to evolve , and the patient became symptomatic after 13 years . A biopsy of the bone bed was taken in all patients . A larger percentage of trabecular bone and a larger relative area of unmineralized osteoid surface were found in patients with rheumatoid arthritis compared with those with osteoarthritis . The latter finding is probably a result of increased bone turnover . In conclusion , no support currently exists for the idea that preoperative bone quality , evaluated as bone histomorphometry , has any impact on prosthetic micromotion in knee prostheses 40 patients with non-inflammatory arthrosis and minor preoperative deformity ( / 5 ° ) were operated on with an AMK type ( DePuy , Johnson & Johnson ) total knee arthroplasty ( TKA ) . The posterior cruciate ligament was retained . The patients were divided into those with a flat ( terminology of the manufacturer : st and ard ) or a concave ( terminology of the manufacturer : constrained ) polyethylene insert ( 20 in each group ) .  Radiostereometric ( RSA ) examinations were done postoperatively and after 3 , 12 and 24 months . The median absolute rotations of the tibial inserts varied between 0.12 and 0.24 ( range 0.00 - 1.54 ) degrees , with no differences between the 2 groups . The median maximum totalpoint motions ( flat/concave = 0.41/0.42 mm ) , the maximum subsidence or lift-off did not differ . The Hospital for Special Surgery knee score and the patients ' opinion about the operation , based on their preoperative expectations , showed little , if any , differences . At 2 years , 10 of 20 patients with flat and 13 of 19 with concave inserts regarded their knee function as normal or almost so Background Cementing technique is a crucial factor in prosthesis fixation . No r and omized studies have been published , however , comparing the outcome of conventional fingerpacking with the outcome of pressurization of the cement prior to cup insertion . Patients and methods We r and omized 50 THAs to either fingerpacking or sequential pressurization ( including individual pressurization of each anchorage hole ) and followed the patients with RSA for 5 years . The penetration of cement into the anchorage holes was measured on digital radiographs . Postoperative radiolucent lines around the cup were correlated to later RSA results . For clinical evaluation , we used SF-36 and HHS . Results The pressurized group of THAs was more stable regarding changes in inclination . We found no other difference in the migratory behavior . The cement penetration into the anchorage holes was deeper with the pressurization technique than with fingerpacking . For the whole group taken together , there was a strong relation between the presence of radiolucent lines as measured on the postoperative radiograph and later migration observed by RSA at 2 and 5 years . Interpretation Pressurization of the cement produced better cement penetration and increased the cup stability in terms of changes in inclination . Early findings of radiolucent lines can predict later unfavorable cup migration There has been renewed interest for metal-on-metal hip resurfacing due to improved design and manufacturing of implants , better material s , and enhanced implant fixation . In contrast to conventional total hip replacements , only a few clinical hip resurfacing trials using radiostereometry ( RSA ) have been reported , and solely for the Birmingham hip resurfacing arthroplasty . The purpose of this RSA trial was to describe the migration pattern of a  new hip resurfacing system ( ReCap ) within the first two years after primary surgery . Twenty-six patients underwent total hip replacement .  The patients were followed-up for up to 24 months and were evaluated with the use of radiostereometric measurements .  The prosthesis showed mean translations and rotation close to zero . Maximum translation was seen along the transverse axis in the medial direction ( 0.13 mm ) . No statistically significant translation or rotation was seen at two-years follow-up , ( t-test , p < 0.05 , translation or rotation ) Improved fixation to bone is vital for improving the long term success of cemented implants . Addition of fluoride to acrylic bone cement may be one way to improve the quality of the bone cement interface and thereby reduce the risk of loosening .  Ninety patients ( 97 hips ) with a median age of 70 years ( range , 31 - 81 years ) scheduled for total hip arthroplasty were r and omized to receive a stem fixed with fluoride-containing acrylic bone cement or conventional acrylic bone cement . Fixation and bone remodeling around the femoral component was studied with radiostereometry and dual-energy xray absorptiometry up to 5 years after the operation in 73 patients ( 77 hips ) . Radiostereometric evaluation at 5 years revealed no differences in stem migration ( subsidence/lift-off ) or rotations . The stem subsidence inside the mantle was similar in the two groups . At 5 years the study group had lost more bone mineral in Gruen regions 5 and 7 than the controls . The Harris hip and pain score did not differ . Use of fluoride containing bone cement did not improve the stem fixation compared with a conventional cement used up to 5 years , but result ed in more pronounced loss of bone mineral density in the medial cortex . Level of Evidence : Therapeutic Level I. See Guidelines for Authors for a complete description of levels of evidence We have carried out a radiostereometric study of 50 patients ( 54 knees ) with osteoarthritis of the knee who were r and omly allocated to receive a cemented or a hydroxyapatite-coated femoral component for total knee replacement . The patients were also stratified to receive one of three types of articulating surface ( st and ard , rotating platform , Freeman-Samuelson (FS)1000 ) all based on the Freeman-Samuelson design . The tibial components were cemented in all cases .  Radiostereometry  was performed post-operatively and at 3 , 12 and 24 months . The analysis was restricted to rotation of the femoral component over time . After two years , rotation of the femoral components in the transverse , longitudinal and sagittal planes did not differ between the cemented and the hydroxyapatite-coated implants ( p = 0.2 to 0.9 ) . In total knee replacements with a rotating platform , the femoral component tended to tilt more posteriorly than in the other two design s , regardless of the choice of fixation ( cemented or hydroxyapatite-coated , p = 0.04 ) . The st and ard version of the femoral component , whether cemented or hydroxyapatite-coated , rotated more into valgus than was observed with the rotating-platform and FS1000 design s ( p = 0.005 ) . The increased constraint provided by the FS1000 component did not appear to have any adverse effect on fixation of the femoral component Background We developed a total hip system using osseointegration guidelines , a metaphyseal-loading proximal femoral replacement in the retained neck and a dual-geometry titanium shell in the acetabulum . Patients and methods A r and omized controlled clinical trial was undertaken in 52 patients ( 53 hips ) , using the cemented Spectron stem and cementless Harris-Galante II cup as control implants  ( 24 patients in experimental group , 29 control patients ) . Clinical measures of Harris Hip Score ( HHS ) , pain score and radiostereometric analysis ( RSA ) at regular intervals for up to three years were used to monitor progress . Results No statistically significant differences were found in HHS and pain score ; the stability of the cementless experimental implant was also comparable to that of the cemented controls by RSA . 3 revisions were required for migration in the experimental group and 1 was required for component dislocation in the control group . Interpretation Our findings indicate the practicality of osseointegration of titanium implants , but suggest that current performance is inadequate for clinical introduction . However , the stable fixation achieved in the retained neck in the majority of patients is indicative of osseointegration . This finding will encourage technical and design improvements for enhancement of clinical osseointegration and should also encourage further study . Periprosthetic osteolysis might be avoided by the establishment and maintenance of direct implant-bone connection : “ osseointegration ” We examined the in vivo displacement of  mobile-bearing polyethylene  and its effect on prosthesis-bone fixation .  Thirty-five patients with the Interax ® ISA mobile platform total knee arthroplasties were examined by roentgen stereophotogrammetric analysis . Our protocol included weightbearing to measure the range of motion of the mobile platform in relation to the tibial component . We also studied the  micromotions of the tibial component in relation to the tibia during a 2-year followup . The analysis of micromotion ( maximum total motion mean , 0.5 mm ; subsidence mean , 0.15 mm ) showed this mobile platform design is stable and improves fixation at the prosthesis-bone interface . Longitudinal rotations of the mobile platform occurred in all patients and followed a homogeneous pattern of motion , depending on the examination . However , anteroposterior translations did not show any patterns with specific examination . This suggests the meniscal movement adapts itself to different weightbearing conditions . We measured the in vivo mobile-bearing displacement under static loading conditions . We also observed improved fixation at the bone-prosthesis interface Background First-generation highly cross-linked polyethylene liners have reduced the incidence of wear particle-induced osteolysis . However , failed acetabular liners have shown evidence of surface cracking , mechanical failure , and oxidative damage . This has led to the development of second-generation highly cross-linked polyethylene , which has improved wear and mechanical properties and resistance to oxidation in vitro . Owing to its recent introduction , there are no publications describing its clinical performance . Questions / purpose sWe assessed early clinical wear of a second-generation highly cross-linked polyethylene liner and compared its clinical performance with the published results of hip simulator tests and with first-generation highly cross-linked polyethylene annealed liners . Patients and Methods Twenty-one patients were enrolled in a prospect i ve cohort study .  Clinical outcome and femoral head penetration were measured for 19 patients at 6 months and 1 and 2 years postoperatively . Results The median proximal head penetration was 0.009 mm and 0.024 mm at 1 and 2 years , respectively . The median two-dimensional ( 2-D ) head penetration was 0.083 mm and 0.060 mm at 1 and 2 years , respectively . The median proximal wear rate between 1 and 2 years was 0.015 mm/year . Conclusions The wear rate calculated was similar to the in vitro wear rate reported for this material ; however , it was less than the detection threshold for this technique . Although longer followup is required for wear to reach a clinical ly quantifiable level , this low level of wear is encouraging for the future clinical performance of this material .Level of Evidence Level IV , therapeutic study . See the Guidelines for Authors for a complete description of levels of evidence The  R3 Acetabular component represents the next generation of acetabular shell with an enhanced porous ingrowth surface ( StikTite , Smith & Nephew , Memphis , Tenn ) to meet the needs of both primary and revision hip arthroplasty ; an optimized locking mechanism ; and the ability to accomo date polyethylene , metal , or ceramic liners . This prospect i ve clinical study reports on the safety and efficacy of the new StikTite porous ingrowth surface using radiostereometric analysis ( RSA ) . StikTite provides a superior " sctratch-fit " due to its greater coefficient of friction and less micromotion using RSA measurements This r and omized study was performed to compare wear and migration of five different cemented total hip joint articulations in 150 patients . The patients received either a Charnley femoral stem with a 22.2  mm head  or a Spectron EF femoral stem with a 28 mm head . The Charnley articulated with a γ-sterilized Charnley Ogee acetabular cup . The Spectron EF was used with either EtO-sterilized non-cross-linked polyethylene ( Reflection All-Poly ) or highly cross-linked ( Reflection All-Poly XLPE ) cups , combined with either cobalt chrome ( CoCr ) or Oxinium femoral heads . The patients were followed with repeated RSA measurements for 2 years . After 2 years , the EtO-sterilized non-cross-linked Reflection All-Poly cups had more than four times higher proximal penetration than its highly cross-linked counterpart . Use of Oxinium femoral heads did not affect penetration at 2 years compared to heads made of CoCr . Further follow-up is needed to evaluate the benefits , if any , of Oxinium femoral heads in the clinical setting . The Charnley Ogee was not outperformed by the more recently introduced implants in our study . We conclude that this prostheses still represents a st and ard against which new implants can be measured We evaluated polyethylene wear by measuring femoral head penetration in 201 THA ( median age 62 ( 31 - 81 ) years , 117 women ) extracted from 5 r and omized studies aim ed to assess various fixation principles . There were 30 cemented all-polyethylene Lubinus cups sterilized by gamma irradiation in a reduced oxygen environment , 65 porous-coated Trilogy cups with liners gamma-sterilized in inert gas . Moreover , 37 cemented cups were sterilized with ethylene oxide ( Reflection all-poly ) and 69 porous-coated cups had liners sterilized in ethylene oxide ( Reflection ) . 28 mm femoral heads were used in all cups . The patients were followed with repeated radiostereometric measurements ( RSA ) up to 2 years . The activity level of the patients was evaluated by a question naire . After 2 years , cups with polyethylene sterilized in EtO had almost twice the proximal and 3D penetration rates , as compared with gamma-sterilized polyethylene . The penetration did not differ between the gamma-irradiated design s. Using stepwise linear regression analysis , we found that the type of sterilization , age and weight were the most important predictors and that they determined the direction of the proximal penetration rate . Activity score , male gender and proximal migration of the cup had little effect . The accelerated wear observed with the EtO-sterilized polyethylene causes concerns about long-term problems and especially in younger patients BACKGROUND Radiostereometry is a well documented method to measure the polyethylene wear after total hip replacements . Wear is measured according to the point motion of the head center in relation to the polyethylene as the reference segment . Increasing head sizes and new cup material s may diminish visibility of markers deteriorating the segment and leading to study drop outs . Alternatively markers in the periacetabular bone may be easier to detect rendering this segment more stable . Our aim was to compare wear measurements against the cup , the acetabuluar bone and a calculated wear estimation including cup migration . METHODS A prospect i ve r and omized controlled trial comparing reverse hybrid with cemented total hip replacement was conducted . 31 patients had tantalum markers in the polyethylene and in the periacetabular bone  making it possible to measure wear using both as reference segments . We used a uniplanar radiostereometric technique . FINDINGS Wear in the y-axis was overestimated by 53 % when markers in the periacetabular bone were used ( P<0.001 ) . Proximal wear was 0.34 mm ( 95 % CI of mean : 0.29 - 0.38 ) when using the polyethylene as the reference and 0.52 mm ( 95 % CI of mean : 0.38 - 0.65 ) using the acetabular bone . Migration of the cup seemed to influence the wear calculations , overestimating wear when markers in the periacetabular bone were used as the reference segment . INTERPRETATION Wear measured with periacatebular bone markers is influenced by cup migration , overestimating wear measurements . We therefore recommend not using the acetabular bone as the reference segment The creep and wear behaviour of highly cross-linked polyethylene and st and ard polyethylene liners were examined in a prospect i ve , double-blind r and omised , controlled trial using radiostereometric analysis . We r and omised 54 patients to receive hip replacements with either highly cross-linked polyethylene or st and ard liners  and determined the three-dimensional penetration of the liners over three years . After three years the mean total penetration was 0.35 mm ( SD 0.14 ) for the highly cross-linked polyethylene group and 0.45 mm ( SD 0.19 ) for the st and ard group . The difference was statistically significant ( p = 0.0184 ) . From the pattern of penetration it was possible to discriminate creep from wear . Most ( 95 % ) of the creep occurred within six months of implantation and nearly all within the first year . There was no difference in the mean degree of creep between the two types of polyethylene ( highly cross-linked polyethylene 0.26 mm , SD 0.17 ; st and ard 0.27 mm , SD 0.2 ; p = 0.83 ) . There was , however , a significant difference ( p = 0.012 ) in the mean wear rate ( highly cross-linked polyethylene 0.03 mm/yr , SD 0.06 ; st and ard 0.07 mm/yr , SD 0.05 ) . Creep and wear occurred in significantly different directions ( p = 0.01 ) ; creep was predominantly proximal whereas wear was anterior , proximal and medial . We conclude that penetration in the first six months is creep-dominated , but after one year virtually all penetration is due to wear . Highly cross-linked polyethylene has a 60 % lower rate of wear than st and ard polyethylene and therefore will probably perform better in the long term We performed a r and omised , radiostereometric study comparing two different bone cements , one of which has been sparsely clinical ly documented . R and omisation of 60 total hip replacements ( 57 patients ) into two groups of 30 was undertaken . All the patients were operated on using a cemented Charnley total hip replacement  , the only difference between groups being the bone cement used to secure the femoral component . The two cements used were Palamed G and Palacos R with gentamicin . The patients were followed up with repeated clinical and radiostereometric examinations for two years to assess the micromovement of the femoral component and the clinical outcome . The mean subsidence was 0.18 mm and 0.21 mm , and the mean internal rotation was 1.7 degrees and 2.0 degrees at two years for the Palamed G and Palacos R with gentamicin bone cements , respectively . We found no statistically significant differences between the groups . Micromovement occurred between the femoral component and the cement , while the cement mantle was stable inside the bone . The Harris hip score improved from a mean of 38 points ( 14 to 54 ) and 36 ( 10 to 57 ) pre-operatively to a mean of 92 ( 77 to 100 ) and 91 ( 63 to 100 ) at two years in the Palamed G and Palacos R groups , respectively . No differences were found between the groups . Both bone cements provided good initial fixation of the femoral component and good clinical results at two years The quality of technique used at the time of socket cementation is crucial in ensuring a durable long-term result of the implant . We asked whether a new instrument , an aspirator retractor introduced into the wing of the ilium before socket preparation and cementation , would enhance cement fixation as defined by RSA and radiographic examination . We r and omized 38 patients into two groups . The surgical technique was identical between the groups with the exception of the use of the aspirator retractor .  Patients were followed clinical ly and with radiostereometry at a minimum of 2 years . We compared gross radiographic appearances , including the depth of penetration of cement and the incidence of postoperative and 2-year radiolucent lines . There was no difference in proximal migration between the two groups . No improvement of fixation was proven from the measured translations and rotations of the socket in the suction group . We found no difference in the number or extent of radiolucent lines or the depth of cement penetration when the iliac suction device was used in conjunction with contemporary cementing techniques . Although the data suggest no short-term advantage in this small study , we will continue to follow these patients presuming there will be improved outcomes in the longer term and since the device provides an easier method of obtaining adequate fixation , especially if technical difficulties are encountered during the pressurization procedure Ninety patients ( 96 hips ) scheduled for THA were stratified to fixation of the acetabular component in three main groups of about equal size . Fluoride cement , porous coated press-fit cup with ceramic coating or Palacos cum Gentamicin cement were used . All patients received Spectron EF stem .  The migration of the cups and the femoral head penetration into the socket were measured with radiostereometric analysis . At 2 years the choice of fixation did not influence the migration or rotation of the cup .  Patients with compromised bone quality showed increased three-dimensional ( 3D or total ) migration . Proximal and 3D penetration rates were increased in cemented compared with the uncemented cups ( p<0.001 ) , which probably not could be related to the choice of fixation . Appearance of radiolucent lines was almost equal in the two cemented groups . Uncemented cups had less radiolucent lines at 2 years . Fluoride containing cement or uncemented fixation did not improve the early postoperative stability of the socket Our aim in this pilot study was to evaluate the fixation of , the bone remodelling around , and the clinical outcome after surgery of a new , uncemented , fully hydroxyapatite-coated , collared and tapered femoral component , design ed specifically for elderly patients with a fracture of the femoral neck . We enrolled 50 patients , of at least 70 years of age , with an acute displaced fracture of the femoral neck in this prospect i ve single-series study . They received a total hip replacement using the new component and were followed up regularly for two years . Fixation was evaluated by radiostereometric analysis and bone remodelling by dual-energy x-ray absorptiometry .  Hip function and the health-related quality of life were assessed using the Harris hip score and the EuroQol-5D . Up to six weeks post-operatively there was a mean subsidence of 0.2 mm ( -2.1 to + 0.5 ) and a retroversion of a mean of 1.2 ° ( -8.2 ° to + 1.5 ° ) . No component migrated after three months . The patients had a continuous loss of peri-prosthetic bone which amounted to a mean of 16 % ( -49 % to + 10 % ) at two years . The mean Harris hip score was 82 ( 51 to 100 ) after two years . The two-year results from this pilot study indicate that this new , uncemented femoral component can be used for elderly patients with osteoporotic fractures of the femoral neck 52 knees scheduled for a total knee arthroplasty were r and omised to either a fixed or a mobile polyethylene bearing . The design was identical in all parts . The knee systems used were the Rotaglide Total Knee System ( RTK ) and the Nuffield Total Knee System ( NTK ) , both from the same manufacturer ( Corin Medical Ltd. , UK ) . All knees implanted were uncemented . The patients were followed for 2 years clinical ly and with radiostereometric analyses to assess migration over time and inducible displacement of the tibial component . Separate analysis of the mobility of the tibial insert in the knees with a mobile bearing was also made . The migration measured with RSA between the 1st and 2nd year expressed as maximum total point motion ( MTPM ) might predict the risk of loosening of the implant . There were no differences between the groups regarding clinical outcome ( HSS Knee score ) , migration or inducible displacement during the 2 years follow-up . The movement between the tibial tray and the mobile meniscal insert expressed as maximum total point motion ( MTPM ) was 6.8+/-3.3 mm at the 1st year follow-up We report the initial results of an ongoing r and omised , prospect i ve study on migration of the Exeter and Elite Plus femoral stems after impaction allografting  , as measured by radiostereometry . Clinical ly , the impaction technique gave good results for both stems . The mean subsidence in the first year was 1.30 mm and 0.20 mm for the Exeter and the Elite Plus stems , respectively . In the second year , the Exeter stem continued to subside further by a mean of 0.42 mm , while the Elite Plus stem did not do so . Subsidence of the Exeter stem correlated with deficiency of bone stock as grade d on the Gustilo and Pasternak scale . This correlation was not found for the Elite Plus stem . None of the other parameters which were studied predisposed to subsidence . There was no significant association between the amount of subsidence and the radiological appearance of the graft for either stem . Our findings do not support the theory that radial compression , due to subsidence of the Exeter stem , is the essential stimulus for remodelling in impaction allografting Purpose Wear is a major contributor to osteolysis and aseptic loosening of total hip replacements ( THR ) . Both alumina ( Al2O3 ) and cobalt-chrome ( CoCr ) femoral heads are commonly used . We investigated wear comparing alumina heads to cobalt-chrome heads against conventional cemented polyethylene ( PE ) cups for up to ten years . Methods Linear wear was measured with radiostereometry ( RSA ) . Our material was derived from two prospect i ve r and omised trials that investigated fixation of femoral stems , not wear , and was evaluated retrospectively ( Level III ) . Results The mean ( 95 % CI ) proximal head penetration was 0.96 mm ( 0.68–1.23 ) in the cobalt-chrome group and 0.42 mm ( 0.30–0.53 ) in the alumina group at ten years ( P = 0.001 ) . The mean ( 95 % CI ) 3D penetration was 1.07 mm ( 0.79–1.35 ) and 0.53 mm ( 0.38–0.63 ) , respectively , at ten years ( P = 0.001 ) . Conclusion Alumina heads performed better than cobalt-chrome heads in this study after ten-year follow-up Background There is no consensus as to whether uncemented or cemented femoral stems should be used in younger patients . We compared the uncemented Cone stem to the cemented Bimetric stem in young patients with osteoarthritis . Patients and methods We r and omized 45 relatively young patients ( < 65 years old , mean age 54 years ) with osteoarthritis to either an uncemented Cone stem or a cemented Bimetric stem . All patients were followed for 2 years . Outcome was assessed by the Merle d’Aubigné score , conventional radiography and repeated radio-stereometric analysis ( RSA ) . We also followed 81 Cone stems for 8 ( 7–12 ) years with revision as endpoint . Results The clinical outcome was excellent . No patient had postoperative thigh pain . The migration was small . The Bimetric stem was stable during the whole observation period , while the Cone stem  subsided and rotated to retroversion during the first 3 months post-operatively , and then remained stable . In the follow-up study of 81 Cone stems , 1 stem was revised . Interpretation We conclude that both the cemented Bimetric stem and the uncemented Cone stem are stable and give excellent clinical results after 2 years in relatively young patients with osteoarthritis . Although design ed for CDH hips , the Cone stem appears to be suitable also for patients with osteoarthitis . Sixty-two patients ( 64 hips ) were provided with porous press-fit cups ( Trilogy ) , plasma-sprayed with a coating consisting of 70 % hydroxyapatite and 30 % tricalcium phosphate . The patients were r and omized to a cup with cluster holes for adjunctive screw fixation ( n = 30 ) or to a cup without holes ( n = 34 ) .  Radiostereometry  was used to study migration and wear . Up to 2 years median translations and rotations < 0.2 mm and < 0.2 degrees were recorded in the 2 groups , without any difference . The median annual proximal wear ( 0.11 and 0.12 mm ) was within the expected range despite the use of a ceramic coating , and it did not differ between the 2 design s. Radiolucent lines were frequently seen postoperatively but diminished during the follow-up without any sign of migration into the gaps . At 2 years , the median Harris scores were 99 points ( range , 51 - 100 points ) in the group with and 98 points ( range , 69 - 100 points ) in the group without screws . The results indicate that early fixation can be achieved for ceramic-coated press-fit cups without using additional screw fixation A total of 51 knees ( 45 patients ) with osteoarthrosis were stratified in a r and omized study to receive a hydroxyapatite-coated Freeman-Samuelson ( FS HA ) or a porous-coated Miller-Galante II ( MG II ) uncemented total knee arthroplasty . Repeated clinical , radiographic  , and  radiostereometric analysis (  RSA ) evaluations of the tibial components were done for 5 years . The clinical outcome was equal at the 5-year follow-up ( mean Hospital for Special Surgery score , 93 ) . St and ard radiographs displayed more zones around the tibial stem in the MG II group . RSA revealed that the FS HA components migrated less ( smaller maximum total point motion and maximum subsidence ) after 5 years and showed less inducible displacements at the 1-year follow-up . The stability of the implants obtained is equal to or better than cemented implants after 5 years . Key words : knee prosthesis , cementless , hydroxyapatite , radiostereometry , inducible displacement To evaluate different modes of cementless fixation of hemispherical cups , we operated on 87 hips in 81 patients using 4 different means of cup fixation . The hips were r and omly assigned to fixation with press-fit technique only ( PF ) , or with augmentation with screws ( S ) , pegs ( P ) , or hydroxyapatite ( HA ) coating . The patients were evaluated with radiostereometric analysis ( RSA ) for cup migration and wear , conventional radiography for osteolysis , and Harris Hip Score for clinical outcome over 5 years . The fixation of the cups did not differ between the groups , but HA showed a tendency to decrease proximal migration . HA-coated cups displayed the best interface with hardly any signs of radiolucent lines , indicating a superior sealing effect of the HA coating . Cups with screws or pegs had more radiolucent lines and osteolytic lesions than the other groups . Radiolucent lines were correlated to higher proximal migration , young age , and female gender ( r2=.2 ) . The wear rate of the ethylene oxide-sterilized polyethylene liner was high ( 0.2 mm/y ) but did not differ between the groups . Two cups with a perioperative fracture of the acetabular rim showed large initial migration but stabilized thereafter Forty-one patients were  r and omized to a cemented Miller-Galante unicompartmental ( Zimmer , Warsaw , Ind ) knee arthroplasty inserted with either minimally invasive surgery or with a st and ard exposure . Clinical data and conventional radiographs were recorded and patients were followed with radiostereometric analysis to measure migration rate of the tibial component . The rehabilitation of patients operated through a small incision was faster , and there was a significant difference in days of hospitalization ( P = .03 ) . No statistical significant difference was found between the 2 groups regarding clinical or radiographic data . The Hospital for Special Surgery score was 96 and 92 , respectively , for the minimally invasive surgery and conventional group at 2 years . The limb alignment was equal in both groups with a mean femorotibial axis of 182 degrees after surgery . The rate of migration for tibial components was very small , with a maximal total point motion of 0.8 mm for both groups after 2 years follow-up Forty-seven knees in 43 patients with severe deformities r and omly received AMK total knee arthroplasty with concave ( C , n = 25 ) or posterior-stabilized ( PS , n = 22 ) polyethylene insert and with resection of the posterior cruciate ligament . Radiostereometric examinations were done postoperatively and after 3 , 12 , and 24 months . Two patients ( 1 C , 1 PS ) underwent revision surgery . At the 2-year follow-up , the median absolute rotations of the tibial inserts ranged from 0.13 degrees to 0.26 degrees ( C vs PS ; P = .1-.7 ) . The maximum total point motion was almost identical in the 2 groups ( C , 0.38 ; PS , 0.39 ; P = .9 ) . Maximum subsidence , lift-off , and Hospital for Special Surgery scores did not differ ( P = .1-.6 ) . Recipients of 20 of 24 knees with concave design and 14 of 19 knees with posterior-stabilized design reported that their knee could be regarded as normal or almost normal . Variations of the configuration of the polyethylene insert did not alter the outcome in the short term Bone  cement with reduced amount of monomer and low curing temperature may improve implant fixation due to reduced toxicity . We analyzed the mechanical , chemical and thermal properties of such a cement ( Cemex Rx ) using Palacos R as control . The in vivo performance of the 2 cements was also evaluated in a prospect i ve r and omized study of 47 hips , where either of the cement types was used to fixate Lubinus SP2 prostheses with the stem made of titanium alloy . Cemex Rx had a reduced tensile strength , probably because this cement was manually mixed , as recommended by the manufacturer . A st and ardized laboratory test showed lower curing temperature for Cemex , but measurements at 37 ° and with prechilled Palacos R and Cemex Rx , as in clinical work , showed no difference . In the clinical study radiostereometric measurements of cup and stem migration showed similar values in the 2 groups up to 5 years after the operation . The cement mantle was stable in both groups , but the stems migrated similarly inside the cement mantle regardless of the type of cement used . Proximal wear was low ( 0.04 - 0.05 mm/year ) and tended to be lower in the Cemex group ( p = 0.02 ) . Aluminum and vanadium levels in serum increased 5 years after the operation , but no difference was noted between the 2 groups . Collagen markers ( PICP , ICTP ) showed similar increases in bone turnover 6 weeks and 6 months after operation in both groups We studied CMW-1 bone cement with gentamicin in the laboratory and in a r and omized clinical study . Palacos bone cement containing gentamicin was used as the control . In the pre clinical evaluation , the CMW cement had slightly less mechanical strength . In the clinical study , 51 patients ( 51 knees ) operated on with total knee arthroplasty were studied for 2 years . We used radiostereometric analysis to measure migration of the tibial components , r and omized to fixation with either of the two types of cement . The extent and pattern of migration were similar in both groups , and we found no differences in the number , size and extent of radiolucent lines or clinical outcome . No complications occurred . Our findings suggest a need for more studies of CMW-1 bone cement containing gentamicin in a larger cohort of patients Mobile bearings were introduced to improve wear and knee kinematics . By uncoupling the forces generated at the articulation from the implant-bone interface this would , theoretically , also improve the fixation of the implant to bone . We did this study to evaluate whether mobile bearings  improve the fixation of the tibial component to bone .  Fifty-two consecutive knees in 47 patients ( average age , 72 years ; range , 62 - 84 years ) with primary osteoarthrosis were r and omized into two groups to receive a cemented total knee arthroplasty with either a fixed-bearing or mobile-bearing tibial component . The quality of fixation was analyzed with radiostereometric analysis for up to 2 years . Mobile bearings did not improve fixation . Both magnitudes and directions of component rotations were similar , and the number of implants with continuous migration was almost identical . Both implant types had a combination of subsidence and lift-off , but where the mobile bearing implants displayed more of subsidence , the fixed bearing knees showed more lift-off . It might be that the somewhat stiffer cobalt-chromium baseplate or the different joint conformity used in the mobile-bearing knees counteracts any potential effects of the mobile bearing . Level of Evidence : Therapeutic Level I. See the Guidelines for Authors for a complete description of levels of evidence Background We have developed a bone-conserving commercially pure titanium hip replacement system using osseointegration principles : a metaphyseal loading proximal femoral component affixing into the retained neck and metaphysis only , leaving the femoral canal untouched . The acetabular cup closely fits a dual-geometry cavity , avoiding stress protection at the dome . Patients and methods After extensive laboratory and clinical pilot trial investigations , the surface-engineered implants were su bmi tted to a prospect i ve r and omized controlled clinical trial involving 40 patients ( 40 hips ) , in which they were compared to the cemented Spectron femoral component and cementless Trilogy cup as control implant . The following clinical measures were used to monitor progress at regular intervals for the first 2 postoperative years : radiostereometric analysis ( RSA ) , Harris Hip Score , pain score , WOMAC , and SF-36 . Results After 2 years of follow-up , no statistically significant differences were seen between the groups concerning rotation or translation along the cardinal axes . The patients receiving the Gothenburg osseointegrated titanium ( GOT ) system had significantly higher Harris Hip Score at 6 months , suggesting more rapid recovery . WOMAC , SF-36 and pain analysis were similar for the first 2 postoperative years . Interpretation Our RSA data suggest that osseointegration was achieved for all patients receiving the GOT hip system . This bone-conserving prosthesis may provide a good alternative , especially for young and active patients There is uncertainty regarding whether and how the subchondral bone plate should be treated during acetabular preparation for cemented cup fixation in a total hip arthroplasty . We hypothesized that removing the bone plate would improve the cement-bone interface without jeopardizing the initial cup stability , and therefore , be advantageous to long-term cup survival . We r and omized 50 patients with primary osteoarthritis into two groups , one for removal and one for retention of the subchondral bone plate .  The patients were evaluated during 2 years followup using repeated radiostereometric examinations , analyses of radiolucent lines , and clinical followups . Patient scoring was done using the Western Ontario and McMaster Universities Osteoarthritis Index , the Short Form-12 , and the Harris hip score . Removal of the subchondral bone plate result ed in a superior cement-bone interface with less development of radiolucent lines . The radiostereometry results showed small migrations in both groups . We found no differences in cup stability between groups , although a difference was observed in rotational behavior with the removal group stabilizing in a slightly vertical position whereas the retention group showed slight but progressive rotation into a more horizontal position . No differences were found during clinical followups . Removing the subchondral bone plate , where possible , improves the cement-bone interface without jeopardizing the stability , implying better long-term cup survival . However , it is a more dem and ing surgical technique . Level of Evidence : Therapeutic study , Level I ( high quality r and omized controlled trial with statistically significant difference or no statistically significant difference but narrow confidence intervals ) . See the Guidelines for Authors for a complete description of levels of evidence Background Minor design changes may cause major changes in implant performance . Thus , as part of a stepwise introduction of a new low-profile cup , we performed a r and omized trial comparing it to a well-docu-mented st and ard cup . Patients and methods 60 patients , stratified according to sex , weight , and age , underwent cemented total hip arthroplasty using a Lubinus SP2 stem with ceramic head  and were r and omized to either the new low-profile Lubinus Flanged Anti-Luxation cup ( FAL ) or the Lubinus St and ard Eccentric cup ( St and ard ) .  7 patients were excluded and 53 ( 28 FAL ) were evaluated at 3 , 6 , 12 , and 36 months postoperatively . Primary outcome variables , cup migration ( MTPM ) , and wear ( total 3-dimensional femoral head penetration ) were measured with radiostereometry ( RSA ) . Clinical outcome was evaluated with the western Ontario and McMaster osteoarthritis index ( Womac ) and the visual analog pain score ( VAS ) . Results We found no difference in migration between the FAL and St and ard cups . There was no difference in wear between the two cups and there was no correlation between wear and migration . 3 cups ( 2 FAL and 1 St and ard ) showed continuous migration of a magnitude that indicated an increased risk of early loosening . Clinical outcome was excellent , without any difference between the 2 groups This prospect i ve , r and omized protocol evaluated femoral head penetration after total hip arthroplasty in a young population . Forty-five patients r and omly received either a cross-linked or conventional ultrahigh-molecular-weight polyethylene ( UHMWPE ) liner in a noncemented hemispheric cup ( Trilogy , Zimmer , Warsaw , Ind ) with a 28-mm femoral head . Radiostereometric analysis film pairs , Harris hip , UCLA , SF-12 , and Western Ontario and McMaster Universities scores were obtained through 2 years . Median femoral head penetration was less among cross-linked compared to conventional liners as follows : 0.06 mm ( 0.04 - 0.08 mm ) vs 0.08 mm ( 0.02 - 0.19 mm ) at 6 months , 0.07 mm ( -0.14 to 0.16 mm ) vs 0.11 mm ( 0.01 - 0.27 mm ) at 1 year , and 0.065 mm ( -0.04 to 0.193 mm ) vs 0.169 mm ( 0.09 - 0.22 mm ) at 2 years . Clinical outcomes were similar between the groups . Highly cross-linked UHMWPE demonstrated 55 % less femoral head penetration compared to conventional polyethylene at 2 years . Despite improvements in the manufacturing process and sterilization of conventional UHMWPE , the femoral head penetration rate is unchanged from historical st and ards Background : Femoral stems with reduced stiffness were introduced in total hip arthroplasty to facilitate proximal load transfer and thereby reduce periprosthetic bone loss . Poor fixation and unacceptably high revision rates turned out to be a major problem with these prostheses . The purpose of the present study was to evaluate the early performance of a low-modulus stem ( one that is less stiff ) with the potential to address the problem of fixation by the use of a surface coating . The coating consisted of a titanium porous mesh proximally covered with a mixture of hydroxyapatite and tricalcium phosphate . Methods : Thirty-nine men and twenty-six women ( sixty-eight hips ) with noninflammatory arthritis were studied . The patients were r and omized to receive either a porous-coated composite stem with reduced stiffness ( Epoch ) or a stiff stem with a porous coating ( Anatomic ) . Both stems were inserted without cement , had a ceramic coating on the proximal two-thirds , and were supplied with tantalum beads . At the time of the operation , tantalum markers were also placed into the proximal part of the femur . The patients were followed for up to two years after the operation and were evaluated with use of repeated radiostereometric measurements , measurements of bone-mineral density , conventional radiography , and Harris hip scores . Results : Both stems showed optimum fixation with median subsidence and stem rotations that were close to zero . Repeated measurements of bone-mineral density revealed early loss of bone mineral in all Gruen regions in both treatment groups . The loss of bone mineral around the Epoch stems was significantly reduced at two years in Gruen regions 1 , 2 , 6 , and 7 ( p < 0.0005 to 0.04 ) . Measurements on postoperative radiographs showed no difference in stem positioning or fill , but the Epoch stems had significantly more endocortical contact on both the anteroposterior ( p < 0.0005 ) and the lateral radiograph ( p = 0.02).At two years postoperatively , the Epoch stems had fewer sclerotic lines surrounding the stem ( p £ 0.002 ) and less sclerosis at the tip of the prosthesis ( p = 0.001 ) compared with the Anatomic stems . The clinical results in terms of the Harris hip score , which was determined in all hips , and pain or discomfort , which was evaluated in thirty-seven hips treated at the same hospital , were not found to be different , with the numbers available . Conclusions : Contrary to previous studies of other design s with reduced stiffness , the Epoch stem achieved excellent primary fixation . Despite this rigid fixation , the proximal loss of bone-mineral density was less than that associated with the stem with a stiffer design . These results should encourage additional long-term studies with a larger patient population One hundred twenty-eight consecutive knees were operated on with the Duracon unicompartmental knee arthroplasty . Of 111 knees , followed 3 years ( range , 1 - 6 years ) , 109 knees were satisfactory . Two knees were revised because of progression of osteoarthritis and inexplicable pain . Radiostereometric analysis in 49 knees showed a migration of 0.6 mm after 2 years . The magnitude of migration was lower in comparison with published series . In a multicenter study comprising 4 other hospitals , there were 8 revisions in 123 operated knees . The reasons were loosening , subsidence , or fracture . These revisions were within 1 year and mostly related to operative technique . Unicompartmental knee arthroplasty is a dem and ing procedure that needs special experience and includes a risk of early failures during the introduction of a system We have evaluated the difference in the migration patterns over two years of two  cementless stems  in a r and omised , controlled trial using radiostereophotogrammetric analysis ( RSA ) . The implants studied were the Furlong HAC stem , which has good long-term results and the Furlong Active stem , which is a modified version of the former design ed to minimise stress concentrations between the implant and bone , and thus to improve fixation . A total of 23 Furlong HAC and 20 Furlong Active stems were implanted in 43 patients .  RSA examinations were carried out immediately post-operatively and at six , 12 and 24 months post-operatively . The subsidence during the first year in the Furlong HAC stem , was approximately one-third that of the Furlong Active stem , the measured mean subsidence of the femoral head at six months being 0.27 mm ( 95 % confidence interval ( CI ) 0.03 to 0.51 ) and 0.99 mm ( 95 % CI 0.38 to 1.60 ) , respectively ( p = 0.03 ) . One Active stem continued to subside during the second year . All hips , regardless of the type of stem were clinical ly successful as judged by the Oxford hip score and a derived pain score without any distinction between the two types of stem . The initial stability of the Furlong Active stem was not as good as the established stem which might compromise osseo-integration to the detriment of long-term success . The changes in the geometry of the stem , to minimise stress have affected the attainment of initial stability In a double-blind study , we r and omized 50 patients to receive peroral clodronate medication or placebo from 3 weeks before until 6 months after a total knee replacement with a cemented NexGen implant .  Migration of the tibial components was measured by radiostereometry at 1 year . Clodronate reduced prosthetic migration , as measured by maximum total point motion , from 0.40 mm to 0.29 mm ( p = 0.01 ) . This confirms that the early postoperative migration is related to bone resorption and thus the biology of the bone bed . Since early migration is related to late loosening , 6 months of clodronate medication might reduce the risk of loosening Eighty patients ( 84 hips ) r and omly received an anteverted cobalt-chromium stem ( Lubinus SP2 ; Waldemar Link , Hamburg , Germany ) with matte , polymethyl methacrylate-coated , or polished surface ( uncollared ) . Radiostereometry  was used to study migration and wear ; and the bone mineral density was studied with dual-energy x-ray absorptiometry at 6 months , 1 year , 2 years , and 5 years . The polished stems had subsided 0.1 to 0.2 mm more at 6 months and 0.3 to 0.4 mm more at 5 years than the matte and precoated versions ( P < .0001 ) and subsided mainly inside the cement mantle . The rotations of the stem and the migration and wear of the cemented cup did not differ between the 3 groups . After 1 and 2 years , the polished stems had lost significantly less bone mineral in Gruen zones 1 , 2 , 6 , and 7 ( P = .004 to .03 ) ; but this difference had disappeared after 5 years . The period of improved bone remodeling around the polished version coincided with the early period of increased subsidence , suggesting that stem motions inside the mantle result ed in a favorable loading of the proximal femur . Our observations suggest that alternative shapes could be possible on future polished femoral stem design The custom made Unique stem is design ed to fit closely to the metaphyseal region of the femur in order to obtain maximum mechanical stability and optimal load transfer . Thirty-seven patients ( 38 hips ) with non-inflammatory arthritis were r and omized to the uncemented custom made Unique stem or the Elite Plus stem inserted with cement . The patients have been followed clinical ly as well as with radiostereometry ( RSA ) and Dual-energy X-ray Absorptiometry ( DXA ) for 2 years . After 2 years the RSA result showed minimal translation and rotation for the Unique stem while the Elite Plus rotated slightly ( mean 1.05 degrees ) into retroversion . Compared to previous studies the Elite Plus was as stable as the Charnley prosthesis . The DXA results showed a significantly higher proximal and total ( 10 % for the Unique versus 5 % for Elite ) bone loss for the Unique stem compared to the Elite Plus . Thus the optimal proximal press-fit of the custom made stem did secure a stable fixation , but did not decrease the proximal bone loss A prospect i ve double-blind , r and omized , and controlled trial was conducted using roentgen stereophotogrammetric analysis ; 54 total hip arthroplasty patients were r and omized to receive either highly cross-linked polyethylene ( HXLPE ) or st and ard ultra-high-molecular-weight polyethylene ( UHMWPE ) liners . The 3-dimensional penetration of the liner was determined over 2 years . For the first 3 months , both polyethylene types had a rapid penetration rate ( HXLPE : 0.22 mm , SD = 0.17 mm ; UHMWPE : 0.21 mm , SD = 0.15 mm ; P = .78 ) . After 3 months , the HXLPE penetration rate ( 0.06 mm/y , SD = 0.06 mm/y ) was significantly lower than the UHMWPE penetration rate ( 0.10 mm/y , SD = 0.07 mm/y ; P = .04 ) . The penetration in the first 3 months was probably caused by creep or bedding in ; from 3 months onward , much of the penetration was probably caused by wear . We conclude that HXLPE has a 40 % lower wear rate as compared with UHMWPE , suggesting that it will perform better in the long term We evaluated the mechanical , chemical and clinical properties of Boneloc cement using radiostereometry and a series of laboratory tests . Compared to a st and ard cement ( Palacos ) the new cement displayed reduced tensile strength , elastic modulus , curing and glass transition temperatures . The amount of MMA extracted during 3 weeks in methanol was smaller for the Boneloc , but the total amount of released monomers was larger . The adhesion to stainless steel and bone did not differ . Radiostereometric analysis during the first postoperative year in 30 patients r and omized to fixation of hip prostheses using either of the 2 cements displayed increased proximal migration of the cup and increased stem subsidence when Boneloc had been used . Part of the stem subsidence occurred inside the cement mantle . On the basis of these findings , we conclude that the inferior fixation in the Boneloc group is mainly caused by its mechanical properties . Other mechanisms , such as increased release of monomers , may also be important VersaBond is a newly developed bone cement . To investigate its clinical performance , VersaBond was compared to Palacos R in a prospect i ve r and omized study in total knee replacement . Fifty-nine patients ( 61 knees ) undergoing total knee replacement were r and omized to either VersaBond or Palacos R bone cement and followed for 24 months using radiostereometric analysis ( RSA ) . Up to 2 years there were no significant differences in clinical performance between the two cements . The mean/median values for implant migration were very similar for the two bone cements , as were the dispersion , and distribution of outliers . Also the proportion " stable " and " continuously migrating " implants was similar between the two cements . The result of this study indicates that VersaBond bone cement will perform at least equally as well as Palacos R in total knee replacement as regards as aseptic loosening
target: INTERPRETATION The guidelines have improved method ological reporting in RSA studies , but adherence to these guidelines is still relatively low .
background: BACKGROUND AND PURPOSE Guidelines for st and ardization of  radiostereometry ( RSA )  of implants were published in 2005 to facilitate comparison of outcomes between various research groups .
  In this systematic review , we determined how well studies have adhered to these guidelines .