title: Results of unicompartmental knee arthroplasty at a minimum of ten years of follow-up. Unicompartmental knee replacement provides early clinical and functional improvement stabilizing over time Minimally invasive Oxford medial unicompartmental knee arthroplasty. A note of caution! Flexion and extension laxity after medial, mobile-bearing unicompartmental knee arthroplasty: a comparison between a spacer- and a tension-guided technique Lateral unicompartmental knee replacement: fixed or mobile bearing? Unnecessary contraindications for mobile-bearing unicompartmental knee replacement. Mobile-bearing lateral unicompartmental knee replacement with the Oxford domed tibial component: an independent series. Does a high-flexion design affect early outcome of medial unicondylar knee arthroplasty? Clinical comparison at 2 years. Mobile bearing UKA compared to fixed bearing TKA: a randomized prospective study. Fixed or mobile bearing unicompartmental knee replacement? A comparative cohort study. Introduction of a new mobile-bearing total knee prosthesis: minimum three year follow-up of an RCT comparing it with a fixed-bearing device. Mobile vs. fixed bearing unicondylar knee arthroplasty: A randomized study on short term clinical outcomes and knee kinematics. No difference in quality-of-life outcomes after mobile and fixed-bearing medial unicompartmental knee replacement. Comparison of a mobile with a fixed tibial bearing unicompartimental knee prosthesis: a prospective randomized trial using a dedicated outcome score.
abstract: BACKGROUND There is a renewed interest in unicompartmental knee arthroplasty . The present report describes the minimum ten-year results associated with a unicompartmental knee arthroplasty design that is in current use . METHODS Sixty-two consecutive unicompartmental knee arthroplasties that were performed with cemented modular Miller-Galante implants in fifty-one patients were studied prospect ively both clinical ly and radiographically . All patients had isolated unicompartmental disease without patellofemoral symptoms . No patient was lost to follow-up . Thirteen patients ( thirteen knees ) died after less than ten years of follow-up , leaving thirty-eight patients ( forty-nine knees ) with a minimum of ten years of follow-up . The average duration of follow-up was twelve years . RESULTS The mean Hospital for Special Surgery knee score improved from 55 points preoperatively to 92 points at the time of the final follow-up . Thirty-nine knees ( 80 % ) had an excellent result , six ( 12 % ) had a good result , and four ( 8 % ) had a fair result . At the time of the final follow-up , thirty-nine knees ( 80 % ) had flexion to at least 120 degrees . Two patients ( two knees ) with well-fixed components underwent revision to total knee arthroplasty , at seven and eleven years , because of progression of patellofemoral arthritis . At the time of the final follow-up , no component was loose radiographically and there was no evidence of periprosthetic osteolysis . Radiographic evidence of progressive loss of joint space was observed in the opposite compartment of nine knees ( 18 % ) and in the patellofemoral space of seven knees ( 14 % ) . Kaplan-Meier analysis revealed a survival rate of 98.0 % + /- 2.0 % at ten years and of 95.7 % + /- 4.3 % at thirteen years , with revision or radiographic loosening as the end point . The survival rate was 100 % at thirteen years with aseptic loosening as the end point . CONCLUSIONS After a minimum duration of follow-up of ten years , this cemented modular unicompartmental knee design was associated with excellent clinical and radiographic results . Although the ten-year survival rate was excellent , radiographic signs of progression of osteoarthritis in the other compartments continued at a slow rate . With appropriate indications and technique , this unicompartmental knee design can yield excellent results into the beginning of the second decade of use Purpose Unicompartmental knee replacement preserves uninvolved osteocartilaginous and soft tissue structures , thereby allowing a more physiological and early clinical and functional recovery . The aim of this study was to report the results of  ZUK unicompartmental fixed metal-back prosthesis and how these results change over time . Methods Between 2005 and 2007 , 80 ZUK prostheses were implanted in 80 patients for unicompartmental osteoarthritis or osteonecrosis . Patients were clinical ly assessed using the International Knee Society scores . Postoperative values of mechanical axis were calculated 12 months after surgery and compared to the preoperative ones . Results The mean International Knee Society knee and function scores improved , respectively , from 46 ± 9 and 54 ± 8 preoperatively to 82 ± 5 and 94 ± 3 at the last follow-up ( P < 0.001 ) . Average flexion increased from 110 ° ± 9 ° to 127 ° ± 8 ° ( P < 0.01 ) . Patients with unicompartmental knee reached good clinical outcome very early and remained at the same level . Age did not significantly influence clinical and functional scores . Conclusions High success rates of the modern unicompartmental knee implants depend on the material s and design evolution , improvement of the surgical technique , and the strong restriction of indications . Level of evidence Prospect i ve non-r and omized case-series study , Level IV We present the peak outcome results of the Oxford medial unicompartmental arthroplasty through a minimally invasive surgical incision . This prospect i ve study included 78 Oxford medial unicompartmental knee replacements in 68 patients . At the 2 year review the patients achieved a mean Oxford Knee Score of 38.3 . This was not significantly different to the 2 year results of the phase 2 Oxford knee carried out using a st and ard parapatellar approach when patients achieved a mean OKS of 36.0 . Four unicompartmental knee replacements required revision for unexplained pain , deep infection , aseptic loosening and bearing dislocation .  Minimally invasive joint replacement is attractive to both patients and surgeons , but is technically dem and ing with complications inherent to limited access Purpose In a mobile-bearing unicompartmental knee arthroplasty ( UKA ) , stability is of utmost importance to promote knee function and to prevent dislocation of the insert . Gap balancing can be guided by the use of spacers or a tensioner . The goal of this study is to compare laxity of a tension-guided implantation technique versus a spacer-guided technique for medial UKA with a mobile bearing . Also clinical function was compared between the groups . Methods The tension-guided UKA system ( BalanSys ™ , Mathys Ltd , Bettlach , Switzerl and ) was compared with a retrospective group with a  spacer-guided system  ( Oxford , Biomet Ltd , Bridgend , UK ) . A total of 30 tension-guided medial UKAs were implanted and compared with 35 spacer-guided medial prostheses .  In both groups , valgus laxity was measured at least 4 months postoperatively in extension and 70 ° flexion using stress radiographs . Knee Society Scores ( KSS ) were obtained at the 6-month follow-up . Results Valgus laxity in flexion was significantly higher in the tension-guided group compared with the spacer-guided group : 3.9 ° ( SD 1.8 ° ) versus 2.4 ° ( SD 1.2 ° ) , respectively , P < 0.001 ) . In extension , valgus laxity was significantly different : 1.8 ° ( SD 1.0 ° ) in the tension-guided group compared with 2.7 ° ( SD 0.9 ° ) in the spacer-guided group ( P < 0.001 ) . There was no significant difference between the KSS for the two groups ( n.s . ) . Conclusions The tensor-guided system result ed in significantly more valgus laxity in flexion compared with the spacer-guided system . However , in extension , the situation was reversed : the tension-guided system result ed in less valgus laxity than the spacer-guided system . Clinical ly , there were no differences between the groups . The valgus laxity found with the spacer-guided system better approximates the valgus laxity values of the healthy elderly . Level of evidence Lower quality prospect i ve cohort study ( < 80 % follow-up , patients enrolled at different time points in disease ) , Level II Between May 2001 and May 2003 , 233 consecutive Preservation unicompartmental knee replacements ( UKR ) were performed . Of these , 30 were lateral UKRs ( 13 % ) performed in 12 men and 16 women ( 2 bilateral cases ) with a mean age of 67 years ( range 36–93 years ) . A metal-backed mobile bearing tibial component was used in 13 knees and an all-polyethylene fixed bearing tibial component in 17 knees . The patients were review ed prospect ively at 1 and 2 years . The 2 year results show no difference in range of motion or function between the mobile and fixed bearing versions of the Preservation knee when used on the lateral side . There were three early revisions , all in the mobile bearing group The contraindications for unicompartmental knee replacement  (  UKR ) remain controversial . The views of many surgeons are based on Kozinn and Scott 's 1989 publication which stated that patients who weighed more than 82 kg , were younger than 60 years , undertook heavy labour , had exposed bone in the patellofemoral joint or chondrocalcinosis , were not ideal c and i date s for UKR . Our aim was to determine whether these potential contraindications should apply to patients with a mobile-bearing UKR . In order to do this the outcome of patients with these potential contraindications was compared with that of patients without the contraindications in a prospect i ve series of 1000 UKRs . The outcome was assessed using the Oxford knee score , the American Knee Society score , the Tegner activity score , revision rate and survival . The clinical outcome of patients with each of the potential contraindications was similar to or better than those without each contraindication . Overall , 678 UKRs ( 68 % ) were performed in patients who had at least one potential contraindication and only 322 ( 32 % ) in patients deemed to be ideal . The survival at ten years was 97.0 % ( 95 % confidence interval 93.4 to 100.0 ) for those with potential contraindications and 93.6 % ( 95 % confidence interval 87.2 to 100.0 ) in the ideal patients . We conclude that the thresholds proposed by Kozinn and Scott using weight , age , activity , the state of the patellofemoral joint and chondrocalcinosis should not be considered to be contraindications for the use of the Oxford UKR The Oxford mobile-bearing unicompartmental knee replacement ( UKR )  is an effective and safe treatment for  osteoarthritis of the medial compartment . The results in the lateral compartment have been disappointing due to a high early rate of dislocation of the bearing . A series using a newly design ed domed tibial component is reported . The first 50 consecutive domed lateral Oxford UKRs in 50 patients with a mean follow-up of three years ( 2.0 to 4.3 ) were included .  Clinical scores were obtained prospect ively and Kaplan-Meier survival analysis was performed for different endpoints . Radiological variables related to the position and alignment of the components were measured . One patient died and none was lost to follow-up . The cumulative incidence of dislocation was 6.2 % ( 95 % confidence interval ( CI ) 2.0 to 17.9 ) at three years . Survival using revision for any reason and aseptic revision was 94 % ( 95 % CI 82 to 98 ) and 96 % ( 95 % CI 85 to 99 ) at three years , respectively . Outcome scores , visual analogue scale for pain and maximum knee flexion showed a significant improvement ( p < 0.001 ) . The mean Oxford knee score was 43 ( SD 5.3 ) , the mean Objective American Knee Society score was 91 ( SD 13.9 ) and the mean Functional American Knee Society score was 90 ( SD 17.5 ) . The mean maximum flexion was 127 ° ( 90 ° to 145 ° ) . Significant elevation of the lateral joint line as measured by the proximal tibial varus angle ( p = 0.04 ) was evident in the dislocation group when compared with the non-dislocation group . Clinical results are excellent and short-term survival has improved when compared with earlier series . The risk of dislocation remains higher using a mobile-bearing UKR in the lateral compartment when compared with the medial compartment . Patients should be informed about this complication . To avoid dislocations , care must be taken not to elevate the lateral joint line Recently , implant companies have sought to target a more active segment of the population with high-flex implants . Our aim was to compare a successful medial UKA implant with its newer high-flex version . Sixty-one patients ( nonflex , 33 ; high-flex [ HF ] , 28 ) were prospect ively followed after medial UKA  with a minimum of 2-year follow-up . Patients were evaluated using Short Form 12 , Western Ontario and McMaster Osteoarthritis ( WOMAC ) , Knee Society Scores , and range of motion ( ROM ) . The HF group exhibited significantly higher WOMAC Physical Function scores at 3-month follow-up and higher WOMAC Pain and SF-12 Mental Component scores at 2-year follow-up ; all other comparisons were not statistically different , including ROM . The HF cohort had significantly higher improvements in Knee Society Function and Knee score at 1- and 2-year follow-up , respectively ; all other comparisons yielded no significant differences in mean improvement from baseline , including ROM or survivorship We prospect ively evaluated a consecutive series of 56 patients with unicompartmental knee arthritis who underwent unicompartmental knee replacement or total knee arthroplasty and received an average of 52months of follow-up . These patients were enrolled in a prospect i ve r and omized clinical trial . There were no significant differences in the pre-operative parameters of both groups . All the patients were followed up and evaluated preoperatively and yearly , the data was collected and statistical analysis was performed . At an average of 52months after surgery the mean Knee Society score was 80.5 ( range : 70 - 100 ) and 78.9 ( range : 70 - 87 ) for Unicompartmental knee replacement and total knee arthroplasty , mean range of postoperative motion for TKA is 115(0)±4(0 ) and 117(0)±7(0 ) for the group of UKA , with the numbers available , the difference between the two groups could not be shown to be significant . The average operation time of UKA and TKA is 68.8min and 81.5min(p<0.01 ) . Blood drainage after operation had a significant difference between the two groups ( p<0.01 ) . Seven cases of UKA were converted to total knee arthroplasty - all of them within the first 2years of starting the procedure and all of them in relatively young patients . From the study we concluded that mobile bearing UKA can obtain similar clinical effect with TKA by surgeons who have the adequate training and experience . After the learning curve UKA should be considered the primary treatment option for unicompartmental knee arthritis Unicompartmental knee replacement ( UKR ) for anteromedial osteoarthritis is a well-established technique . Numerous clinical outcome studies demonstrate good medium and long-term results . The aim of this prospect i ve study was to compare the complications and short-term clinical outcome of the St. Georg Sled , a fixed bearing UKR , with the Oxford mobile bearing UKR . Outcome at 2 years was assessed using the Bristol knee score and the Oxford knee score ; in addition , complications occurring since formal scoring at 2-year follow-up were recorded . A total of 47 Oxford UKRs and 57 St. Georg Sled UKRs were performed in 91 patients , none of whom were lost to follow-up . At 2 years , both outcome measures were better for the St. Georg Sled Group . The pain component of the Bristol knee score was significantly better for this group ( p-value = 0.013 ) . Three patients in the Oxford group had bearing dislocations and a further four patients required revision ( mean time to revision 3.0 years ) . In the St. Georg Sled group , three patients required revisions ( mean time to revision 3.4 years ) . These results demonstrate that in the short-term , the Oxford mobile bearing prosthesis has a higher re-operation rate and that the St. Georg Sled achieves better pain relief . The functional scores of the two groups were similar As part of the step-wise validation of a new prosthesis ( TMK ) , we previously published the 1 year results of a r and omised controlled trial in patients undergoing bilateral knee replacement  [ Price A. , Rees J. , Beard D. , Juszczak E. et al. A mobile-bearing total knee prosthesis compared with a fixed-bearing prosthesis . JBJS B 2003;85-B-1:62 - 7 . ] . Forty patients had the new mobile-bearing prosthesis implanted in one knee and an established fixed-bearing device in the other ( AGC ) . We now report the 3 year status of these patients and , in addition , review a separate multi-centre cohort of 172 patients who had undergone unilateral arthroplasty with the TMK .  No significant differences were found in outcome ( American Knee Society Score and Oxford Knee Score ) between the two prostheses . The greater incidence of " clicking " in the mobile-bearing knee , reported in the previous review , persisted ( TMK=48 % , AGC=30 % ) . The presence of this mechanical noise was found to have no relationship with outcome in either of the prostheses . The unilateral cohort study showed an acceptable complication rate for the new prosthesis , although some patients reported subjective instability . The method of controlled introduction of the TMK , of which this constitutes a further step , has allowed us to assess the significance of a reported problem ( clicking ) and to provide scientific data from which other surgeons can decide about use of the implant The literature contains limited yet controversial information regarding whether a fixed or a mobile bearing implant should be used in unicompartmental knee arthroplasty ( UKA ) . This r and omized study was to further document the performance and comparison of the two design s. Fifty-six knees in 48 patients ( mean age of 72 years ) undergoing medial UKA were r and omized into a fixed bearing ( Miller/Galante ) or a mobile bearing ( Oxford ) UKA . The 2 year clinical outcomes ( clinical scores ) , radiographic findings , and weight bearing knee kinematics ( assessed using RSA ) were compared between the two groups . The mobile bearing knees displayed a larger and an incrementally increased tibial internal rotation ( 4.3 degrees , 7.6 degrees , 9.5 degrees vs. 3.0 degrees , 3.0 degrees , 4.2 degrees respectively at 30 degrees , 60 degrees , 90 degrees of knee flexion ) compared to the fixed ones . The medial femoral condyle in the mobile bearing knees remained 2 mm from the initial position vs. a 4.2 mm anterior translation in the fixed bearing knees during knee flexion . The contact point in the mobile bearing implant moved 2 mm posteriorly vs. a 6 mm anterior movement in the other group . The mobile bearing knees had a lower incidence of radiolucency at the bone implant interface ( 8 % vs. 37 % , p < 0.05 ) . The incidence of lateral compartment OA and progression of OA at patello-femoral joint were equal . No differences were found regarding Knee Society Scores , WOMAC , and SF-36 scores ( p > 0.05 ) . This study indicates that mobile bearing knees had a better kinematics , a lower incidence of radiolucency but not yet a better knee function at 2 years This is a retrospective study comparing the clinical outcomes of mobile vs fixed medial unicompartmental knee replacements . Patients were identified from a prospect ively collected data base .  Demographic data and pre- and postoperative outcomes ( Oxford , Western Ontario and McMaster Universities Osteoarthritis Index , Short Form Health Survey-12 , and satisfaction ) were collected-104 knees ( 90 patients ) with minimum 2-years of follow-up : 37 mobile and 67 fixed-bearing .  At baseline , the median age was 60 years ( mobile ) and 66 ( fixed ) ; body mass index  was significantly higher ( 32 ) for the mobile group than for the fixed ( 28 ) . At follow-up , the groups differed only in the Oxford score : median 83 ( mobile ) and 90 ( fixed ) . There is no difference in outcomes between mobile and fixed unicompartmental knee replacements Between February 1996 and December 1997 , forty consecutive patients with medial compartment knee arthritis were assigned r and omly into two groups . All underwent a unicompartimental knee replacement . The tibial prosthesis in group A ( 20 knees ) had a fixed bearing and in group B ( 20 knees ) a mobile bearing . The average age was 69 . Five in group A and 71 in group B. Pre-operatively , and at an average follow-up of 5.7 years , all the knees were assessed using both a dedicated UKR score specifically developed and adopted by the Italian Orthopaedic Unicompartimental Knee Replacement Users Group ( GIUM ) and the Knee Society Score . During surgery in group B we experienced a medial tibial plateau fracture fixed intra-operatively . One prosthesis in group A required an early revision to a TKR because of a continuous pain without any evident sign of loosening . There were no meniscal dislocations in group B. No statistically significant difference in outcome was observed between the two groups at the latest follow-up
target: After stratification on follow-up time and age , the revision rates were not substantially different , aside for younger patients in short term from studies with short-term follow-up .
  Conclusion No essential differences between the two design s were observed .
  MB and FB UKA design s have comparable revision rates .
background: Purpose Two design concepts are currently used for unicondylar knee arthroplasty ( UKA ) prostheses :  fixed bearing ( FB ) and mobile bearing ( MB ) .
  While MB prostheses have theoretical advantages over their FB counterparts , it is not clear whether they are associated with better outcomes .