title: Comparison between two computer-assisted total knee arthroplasty: gap-balancing versus measured resection technique Gap balancing sacrifices joint-line maintenance to improve gap symmetry: a randomized controlled trial comparing gap balancing and measured resection. Neutral alignment leads to higher knee society scores after total knee arthroplasty in preoperatively non-varus patients: a prospective clinical study using 3D-CT Rotational alignment of femoral component with different methods in total knee arthroplasty: a randomized, controlled trial Coronal femoral TKA position significantly influences in vivo patellar loading in unresurfaced patellae after primary total knee arthroplasty Intraoperative Comparison of Measured Resection and Gap Balancing Using a Force Sensor: A Prospective, Randomized Controlled Trial. Kinematic femoral alignment with gap balancing and patient-specific instrumentation in total knee arthroplasty: a randomized clinical trial Contact Kinematic Differences Between Gap Balanced vs Measured Resection Techniques for Single Radius Posterior-Stabilized Total Knee Arthroplasty. Alignment in total knee arthroplasty. A comparison of computer-assisted surgery with the conventional technique. Measured Resection versus Gap Balancing Technique for Femoral Rotational Alignment: A Prospective Study Gap Balancing Sacrifices Joint-Line Maintenance to Improve Gap Symmetry: 5-Year Follow-Up of a Randomized Controlled Trial. Gap balancing versus measured resection technique using a mobile-bearing prosthesis in computer-assisted surgery Clinical value of SPECT/CT in the painful total knee arthroplasty (TKA): a prospective study in a consecutive series of 100 TKA Comparison of joint line position changes after primary bilateral total knee arthroplasty performed using the navigation-assisted measured gap resection or gap balancing techniques 4D-SPECT/CT in orthopaedics: a new method of combined quantitative volumetric 3D analysis of SPECT/CT tracer uptake and component position measurements in patients after total knee arthroplasty No difference between tibia-first and femur-first techniques in TKA using computer-assisted surgery Computer-assisted gap balancing technique improves outcome in total knee arthroplasty, compared with conventional measured resection technique Small Improvements in Postoperative Outcome with Gap Balancing Technique Compared with Measured Resection in Total Knee Arthroplasty Functional Outcome after Computer-Assisted Total Knee Arthroplasty Using Measured Resection versus Gap Balancing Techniques: A Randomised Controlled Study Is radiographic measurement of distal femoral torsion reliable?
abstract: Two surgical strategies are possible in total knee arthroplasty ( TKA ) : a measured resection technique , in which bone l and marks are used to guide resections equal to the distal and posterior thickness of the femoral component , or a gap-balancing approach , in which equal collateral ligament tension in flexion and extension is sought before and as a guide to final bone cuts . In this study performed with computer assisted system , we compared the 2 different methods in 126 patients followed prospect ively in order to analyze the effect of both the techniques on joint-line ( JL ) maintenance , axial limb restoration and components position . The gap technique showed a statistical increase in the post-operative value when compared with the measured resection technique , ( P = 0.008 ) . When comparing the two groups regarding to the pre-operative deformity , we have found a statistical difference ( P = 0.001 ) in case of moderate pre-operative deformity ( less than 10 ° ) , and the measured resection technique showed a slight superiority in preserving a joint line more faithful to the pre-operative . We found an ideal alignment for the mechanical axis ( 180 ° ± 3 ° ) ( 95 % of cases ) . In six cases ( 5 % ) , the mean post-operative value exceeded ( varus or valgus ) the ideal value by more than 3 ° . In the frontal plane , a good alignment was observed for both femoral and tibial components without a significant difference between the two techniques . In the sagittal plane was found more alignment variability due to the different implants used and their ideal starting slope , from 7 ° to 3 ° . Finally , the surgeon can use the approach with which he has more confidence ; however , as the measured resection technique causes less reduction in the post-operative joint-line position , in case of shortening of patellar tendon or patella infera , this technique is preferable A total knee arthroplasty can be completed using two techniques ; measured resection or gap balancing . A prospect i ve blinded r and omized controlled trial was completed with 103 patients r and omized to measured resection ( n = 52 ) or gap balancing ( n = 51 ) . Primary outcome measure was femoral component rotation . Secondary outcome measures were joint-line change , gap symmetry and function and quality -of-life outcomes .  Gap balancing result ed in a significantly raised joint-line compared to measured resection .  Gap symmetry was significantly better using gap balancing .  Functional outcomes and quality -of-life were not significantly different at 24 months . Using computer navigation , gap balancing significantly raises the joint-line in order to improve gap symmetry . This does not result in a clinical difference in function or quality of life at 24 months Purpose The optimal coronal alignment is still under debate . However , in most of the studies , alignment was only assessed using radiographs , which are not accurate enough for assessment of tibial and femoral TKA position . The primary purpose of this study was to assess the relationship between coronal TKA alignment using 3D-reconstructed CTs and clinical outcome in patients with preoperative varus in comparison with patients with natural or valgus deformity . It was the hypothesis that neutral limb alignment shows a better outcome after TKA . Methods Prospect ively collected data of 38 patients were included . The clinical and radiological follow-up was 24 months . The patients were grouped into two groups with regard to their preoperative limb alignment . Group A ( varus ) consisted of 21 patients with preoperative varus of 3 ° or more , while group B ( non-varus ) consisted of 17 patients with  neutral  ( − 3 < 0 > + 3 ) or valgus alignment ( > + 3 ) . For assessment of TKA component position and orientation , 3D-reconstructed CT was used . The measurements of the deviation from the whole limb mechanical axis ( HKA angle ) and the joint line alignment in the femoral ( mLDFA ) and the tibial side ( MPTA ) were assessed in the preoperative leg as well as during follow-up after TKA . For clinical outcome assessment , the Knee Society Score ( KSS ) was used at 1 and 2 years postoperatively . Correlation between KSS score and each variable was done using a linear and quadratic regression model ( p < 0.05 ) . Results The mean postoperative HKA angle was − 1.3 ( varus ) in the varus group and + 1.4 ( valgus ) in the non-varus group . Overall , significant correlations between the preoperative and postoperative alignments were found . In the preoperatively non-varus group , a highly significant correlation was found between neutral limb alignment ( HKA = 0 ° ± 3 ° ) and higher KSS ( r2 = 0.74 , p = 0.00 ) . In the varus group , no correlation was found between the postoperative whole limb alignment and the components ’ position in the coronal plane to KSS score . Conclusion A significant correlation was found between neutral limb alignment and higher KSS only in patients with preoperative non-varus alignment . The concept of constitutional varus alignment is still under debate . Moreover , it appears that one should aim for a more individualized , alignment target based on the individual knee morphotype . Level of evidence Diagnostic study , Level II Background Femoral component rotation ( FCR ) is one of the most important factors in total knee arthroplasty . In this prospect i ve study , we used three different techniques for FCR and analyzed their accuracy with postoperative axial computed tomography ( CT ) images . We also evaluated effect of FCR to clinical outcome . Methods One hundred sixty-five patients were r and omly allocated into three groups . In the measured resection group , FCR was set by externally rotating the axis 3 ° off the posterior femoral condylar axis . In the tensor group , a gap-tensioning device set at 20 lbf was used . In the block group , spacer blocks of various thicknesses were used . The FCR angle ( FCRa ) was measured on postoperative axial CT as an angle between the clinical transepicondylar and posterior condylar axes of the femoral component . Outliers were defined as FCRas deviated more than 3 ° either internally or externally . Postoperative 2 year clinical scores and knee range of motion were checked . Results The tensor group had significantly better positioning of the femoral component to the neutral position compared with the measured resection group and the block group ( mean FCRa : internal rotation 1.79 , 0.43 and 2.63 ° , respectively , p < 0.001 ) . The outliers were also least frequent in the tensor group ( 35 , 16 and 40 % , respectively , p = 0.02 ) . There were no significant differences in postoperative 2 year clinical results among groups . Conclusions Gap technique with a 20-lbf tensor device was the most accurate and precise method for obtaining adequate FCR . Measured resection with 3 ° external rotation and gap technique with blocks could lead to internal rotation of the femoral component . Postoperative 2 year clinical results were not significantly different among groups with different techniques for FCR.Trial registration The study was registered in the Clinical Research information Service ( trial number : KCT0000129 ) in Korea . Registration date is 23rd of June , 2011 Purpose As patellar tracking and loading is influenced by tibial tuberosity and trochlear groove ( TT – TG ) distance , patellar height , thickness and tilt as well as TKA component position , it was our hypothesis that these parameters significantly correlate with patellar BTU intensity and localization in SPECT/CT . The purpose of the study was to investigate whether TKA component position as well as the height , thickness and tilt of the unresurfaced patella influences the intensity and the distribution pattern of BTU in SPECT/CT . Methods A total of 62 consecutive patients who underwent primary TKA without patellar resurfacing were prospect ively included . Demographic data such as age , gender , side and type of primary TKA were noted . All patients underwent clinical and radiological examination  in a specialized knee clinic , including st and ardized radiographs ( anterior – posterior and lateral weight bearing , patellar skyline view ) and Tc-99m-HDP-SPECT/CT before , 12 and 24 months after TKA . SPECT/CT images were analysed on 3D reconstructed images . Rotational , sagittal and coronal position of the tibial and femoral TKA components was assessed using a previously vali date d analysis software . Measurements of BTU including intensity and anatomical distribution pattern were also performed from 3D data . The patellar height , thickness and tilt were measured , and the distance between TT and TG was measured using axial CT images . Univariate analysis was performed to identify any correlations between BTU and TKA component position and patellar measurements ( p < 0.05 ) . Results The highest median BTU was measured in the superior posterior parts of the patella . A statistically significant correlation was found between valgus alignment of the femoral TKA and increased BTU at the lateral patellar regions ( p < 0.05 ) . External rotation of the tibial TKA correlated with increased BTU at the lateral superior joint adjacent part ( p < 0.05 ) . No correlation was found between the tibial TKA  position ( varus – valgus , anterior and posterior slope ) , TT – TG distance , patellar height and patellar BTU values . Conclusions A significant correlation of increased patellar BTU was found with femoral valgus TKA alignment . These findings highlight the importance of femoral TKA position in coronal plane with regard to post-operative patellar tracking . Moreover , these facts might explain anterior knee pain in unhappy TKA with femoral valgus alignment . Level of evidence Diagnostic study , Level II BACKGROUND For establishing femoral component position , gap-balancing ( GB ) and measured resection ( MR ) techniques were compared using a force sensor . METHODS Ninety-one patients were r and omized to undergo primary total knee arthroplasty using either MR ( n = 43 ) or GB ( n = 48 ) technique using a single total knee arthroplasty design .  GB was performed with an instrumented tensioner . Force sensor data were obtained before the final implantation . RESULTS GB result ed in greater range of femoral component rotation vs MR ( 1.5 ° ± 2.9 ° vs 3.1 ° ± 0.5 ° , P < .05 ) and posterior condylar cut thickness medially ( 10.2 ± 2.0 mm vs 9.0 ± 1.3 mm ) and laterally ( 8.5 ± 1.9 mm vs 6.4 ± 1.0 mm ) . Force sensor data showed a decreased intercompartmental force difference at full flexion in GB ( .8 ± 2.3 vs 2.0 ± 3.3u , 1u ≈ 15 N , P < .05 ) . CONCLUSION GB result ed in a greater range of femoral component rotation and thicker posterior condylar cuts result ing in an increased flexion space relative to MR . Intercompartmental force difference trended toward a more uniform distribution between full extension and full flexion in the GB vs MR group While patient-specific instrumentation ( PSI ) in total knee arthroplasty ( TKA ) allows for transfer of the preoperative plan onto bony l and marks , the soft tissue balancing is not affected . The goals of this r and omized clinical trial were to compare PSI and the measured resection technique ( conventional ) with PSI and the gap balancing technique .  Fifty patients were r and omized to TKA with conventional PSI ( PSI-S ) ( n = 25 ) or to PSI with additional gap balancing ( PSI-GB ) ( n = 25 ) . All patients were clinical ly examined at 3 and 12 months postoperatively . Data on the range of motion , the Knee Society Score , the Western Ontario and McMasters Universities Osteoarthritis Index , the High-Flexion Knee Score ( HFKS ) , and the Forgotten Joint Score ( FJS ) were compiled at follow-up . Statistically significant improvements were found for all clinical parameters in the PSI-GB group compared to the PSI-S group at 3 months postoperatively and for FS , FJS , and HFKS at 12 months . However , the relevance of these differences , as well as their effect on long-term outcomes , needs to be evaluated further . In conclusion , patient-specific instrumentation combined with gap balancing yielded good early clinical outcomes BACKGROUND Measured resection ( MR ) and gap balancing ( GB ) are common surgical techniques for total knee arthroplasty ( TKA ) . Controversy has arisen as each conceptually differs in how the knee is balanced through bone and soft tissue management . The objective of the present study was to compare both the frequency of condylar liftoff and the location of femorotibial contact from extension through midflexion between patients undergoing GB or MR TKA . METHODS A total of 24 knees ( 23 patients ) were r and omly assigned at referral to either a surgeon performing MR or GB TKA  with the same single radius , posterior-stabilized implant ( 12 per cohort ) . At 1-year postoperation , patients underwent biplanar radiographic imaging at 0 ° , 20 ° , 40 ° , and 60 ° of flexion  . Condylar liftoff , contact location , and magnitude of excursion on each condyle were measured . Preoperative and postoperative clinical outcome scores were also collected . RESULTS There was no difference ( P = .41 ) in the frequency of liftoff between cohorts . The MR cohort had more posterior contact on the medial condyle ( P < .01 ) and more anterior contact on the lateral condyle ( P < .01 ) throughout flexion . Motion patterns were similar between cohorts , with similar medial ( P = .48 ) and lateral ( P = .44 ) excursion , which was equal in magnitude between condyles for both MR ( P = .48 ) and GB ( P = .73 ) . There was no difference in clinical outcome scores between groups . CONCLUSION For this particular implant system , GB and MR appear to produce similar kinematic and patient-reported outcome results Restoration of neutral alignment of the leg is an important factor affecting the long-term results of total knee arthroplasty ( TKA ) . Recent developments in computer-assisted surgery have focused on systems for improving TKA . In a prospect i ve study two groups of 80 patients undergoing TKA had operations using either a computer-assisted navigation system or a conventional technique .  Alignment of the leg and the orientation of components were determined on post-operative long-leg coronal and lateral films . The mechanical axis of the leg was significantly better in the computer-assisted group ( 96 % , within + /- 3 degrees varus/valgus ) compared with the conventional group ( 78 % , within + /- 3 degrees varus/valgus ) . The coronal alignment of the femoral component was also more accurate in the computer-assisted group . Computer-assisted TKA gives a better correction of alignment of the leg and orientation of the components compared with the conventional technique . Potential benefits in the long-term outcome and functional improvement require further investigation Purpose . To compare the measured resection technique and the gap balancing technique for correction of the femoral rotational alignment . Methods . 57 women and 6 men ( mean age , 70 years ) with end-stage osteoarthritis and ±15 ° malalignment and ±10 ° flexion contracture of the knee underwent primary total knee arthroplasty through the medial approach using the measured resection technique ( n=34 ) or the gap balancing technique ( n=29 ) . Femoral rotational alignment was evaluated before and 7 days after surgery using computed tomography by referencing the 2 posterior condyles to the transepicondylar axis . Results . The 2 groups did not differ significantly in terms of correction of the femoral rotational alignment ( 3.4 ° ±1.4 ° vs. 3.5 ° ±3.1 ° , p=0.817 ) . Conclusion . The measured resection and the gap balancing techniques  achieved comparable correction of femoral rotational alignment BACKGROUND Gap balancing ( GB ) has been noted to sacrifice joint-line maintenance to improve gap symmetry . This study aims to determine whether this change affects function or quality of life in the midterm . METHODS A prospect i ve blinded r and omized controlled trial was completed with 103 patients r and omized to measured resection ( n = 52 ) or GB ( n = 51 ) . Primary outcome measured was femoral component rotation . Secondary outcomes measured were joint-line change , gap symmetry , and function and quality -of-life outcomes . RESULTS At 5 years , 83 of 103 patients ( 85 % ) were assessed . There was no significant difference between groups in terms of functional or quality of life outcomes . A subgroup analysis revealed that there was no significant association between those with asymmetrical flexion and /or extension or medial and /or lateral gaps during knee replacement and subsequent functional outcomes . No significant difference was detected with those with an elevated joint line and postoperative function . CONCLUSION In the midterm , the result ant change in joint-line and maintained gap symmetry noted with GB does not result in significant change to function or quality of life Navigation has been developed to help surgeons install implants more accurately and reproducibly ; at the same time , this tool is able to record quantitative information such as joint range of motion , laxity and kinematics intra-operatively . As for st and ard surgery , two strategies are possible to achieve either femoral component rotation or overall prosthetic alignment : a measured gap resection approach , in which bone l and marks are used to guide resections equal to the distal and posterior thickness of the femoral component , or a gap-balancing technique , in which equal collateral ligament tension in flexion and extension is tried to find before as a guide to final bone cuts . The purpose of this paper is to compare the two different methods in a 67 patients group su bmi tted to the same procedure using mobile-bearing ( MB ) prosthesis  in order to analyse the effect of both techniques on joint line maintenance , axial limb restoration and components position . The gap group ( GG ) consists of 31 patients in whom the arthroplasty was performed using a navigated gap-balancing technique . The measured group ( MG ) consists of 36 patients in whom a computer-assisted measured resection technique was used . The results of imaging and the number of outliers were not statistically different ( P = 0.56 ) for the mechanical axis and prosthetic positioning between the two groups . The gap technique showed a statistically significant alteration of the post-operative value when compared with the measured resection technique , ( P = 0.036 ) . The mean elevation of the joint line was 4.09 mm for the GG and 3.50 mm in the MG Purpose Bone single photon emission computed tomography (SPECT)/CT is considered as beneficial in unhappy patients with pain , stiffness or swelling after total knee arthroplasty ( TKA ) . The purpose of this study was to identify typical patterns of bone tracer uptake ( BTU ) , distribution and intensity values in patients after TKA . The above findings were correlated with the type and fixation of TKA , the time from TKA and intraoperative findings at revision surgery . Methods A total of 100 knees of 84 consecutive patients ( mean age ± SD 70 ± 11 years ) after TKA with persistent knee pain were prospect ively included . All patients underwent clinical examination , st and ardized radiographs and 99mTc-hydroxymethane diphosphonate ( HDP ) SPECT/CT as part of a routine diagnostic algorithm . The diagnosis before and after SPECT/CT and final treatment were recorded . TKA component position was determined on 3-D reconstructed images . Intensity and anatomical distribution of BTU was determined . Maximum intensity values were recorded as well as ratios in relation to the proximal midshaft of the femur . Univariate analyses ( chi-square test , Pearson ’s correlation and t test for independent sample s ) were performed ( p < 0.05 ) . Results SPECT/CT changed the clinical diagnosis and final treatment in 85/100 ( 85 % ) knees . Intraoperative findings confirmed the preoperative SPECT/CT diagnosis in 32/33 knees ( 97 % ) . TKA loosening as well as progression of patellofemoral osteoarthritis ( OA ) was correctly diagnosed in 100 % of knees . Typical patterns of BTU for specific pathologies were identified . Loose femoral TKA components significantly correlated with increased BTU at the lateral femoral regions ( p < 0.05 ) . Loose tibial TKA components significantly correlated with increased BTU at all tibial regions ( p < 0.05 ) and around the tibial peg ( p > 0.01 ) . Conclusion The diagnostic benefits of SPECT/CT in patients after TKA have been proven . Typical pathology-related BTU patterns were identified , which will improve reporting quality . Due to the benefits in establishing the correct diagnosis , SPECT/CT should be part of the routine diagnostic algorithm for patients with pain after TKA Purpose This study aim ed to compare the clinical and radiological results of navigation-assisted TKAs performed using the measured gap resection or the gap balancing technique in thirty patients who underwent bilateral primary TKAs . Methods Sixty cases of navigation-assisted TKAs [ 30 TKAs performed using the measured gap resection technique  ( Group A ) and 30 TKAs performed using the gap balancing technique ( Group B ) ] were analyzed prospect ively with minimum follow-up of 2 years . The joint line positions were measured using preoperative and postoperative weight-bearing anteroposterior and lateral radiographs . Clinical results were evaluated using knee scores and functional scores . Results No significant differences in knee scores or functional scores were observed . Polyethylene thickness and flexion/extension gaps were significantly larger in Group B ( P < 0.05 ) . The meaningful proximal shift of the joint line was shown in Group B ( P < 0.05 ) . Conclusion The navigation-assisted TKA with measured gap resection technique could be a useful technique with regard to restoration of the joint line . Level of evidence II Objective The purpose was to evaluate the intra- and inter-observer reliability of combined quantitative 3D-volumetric single-photon emission computed tomography (SPECT)/CT analysis including size , intensity and localisation of tracer uptake regions and total knee arthroplasty ( TKA ) position . Material s and methods Tc-99m-HDP-SPECT/CT of 100 knees after TKA were prospect ively analysed . The anatomical areas represented by a previously vali date d localisation scheme were 3D-volumetrically analysed . The maximum intensity was recorded for each anatomical area . Ratios between the respective value and the mid-shaft of the femur as the reference were calculated . Femoral and tibial TKA position ( varus – valgus , flexion – extension , internal rotation– external rotation ) were determined on 3D-CT . Two consultant radiologists/nuclear medicine physicians interpreted the SPECT/CTs twice with a 2-week interval . The inter- and intra-observer reliability was determined ( ICCs ) . Kappa values were calculated for the area with the highest tracer uptake between the observers . Results The measurements of tracer uptake intensity showed excellent inter- and intra-observer reliabilities for all regions ( tibia , femur and patella ) . Only the tibial shaft area showed ICCs < 0.89 . The kappa values were almost perfect ( 0.856 , p < 0.001 ; 95 % CI 0.778 , 0.922 ) . For measurements of the TKA position , there was strong agreement within and between the readings of the two observers ; the ICCs for the orientation of TKA components for inter- and intra-observer reliability were nearly perfect ( ICCs > 0.84 ) . Conclusion This combined 3D-volumetric st and ardised method of analysing the location , size and the intensity of SPECT/CT tracer uptake regions ( “ hotspots ” ) and the determination of the TKA position was highly reliable and represents a novel promising approach to biomechanics Purpose The measured resection technique and the gap-balancing technique are two philosophies used in total knee surgery . It is still unknown whether one or the other technique provides superior results when computer-assisted surgery is performed . We hypothesized that the gap-balancing technique improves joint stability because the technique relies primarily on the soft tissue . Methods A prospect i ve controlled study was performed in 116 patients using the tibia-first or femur-first technique .  The ColumbusTM total knee system and the Orthopilot ® ( Aesculap ® AG , Tuttlingen , Germany ) navigation system were used in all cases . Sixty-three patients were allocated to the femur-first technique ( group F ) and 53 patients to the tibial first technique ( group T ) . The mean follow-up time was 11.4 ± 1.1 months . The KSS , KOOS and SF-36 were taken prior to surgery and at the time of follow-up for clinical assessment . Long-leg weight-bearing radiographs were performed to assess ligament alignment . Radiographs in varus and valgus stress were performed using the Telos ® -Instrument ( Telos ® GmbH , Greisheim , Germany ) under a force of 15 N at the time of follow-up for the assessment of medial – lateral stability . The nonparametric t test ( Mann – Whitney U-test ) was used in order to compare the ligament stability and the scores between group F and group T. Results The lateral joint space opening for groups F and T was 3.4 ° ± 1.4 ° and 3.9 ° ± 1.7 ° , respectively ( n.s . ) , and the medial joint space opening for groups F and T was 4 ° ± 1.4 ° and 4.1 ° ± 1.7 ° , respectively ( n.s . ) . The femorotibial mechanical axis for groups F and T revealed 1.4 ° ± 1.2 ° and 0.7 ° ± 2.0 ° of varus , respectively ( p = 0.138 ) . The clinical assessment showed significant improvement according to KSS , KOOS and SF-36 in all subscales . Neither of the sores showed significant differences between the two groups . Conclusion The surgeon should use his/her preferred surgical technique providing the implantation is performed with computer assistance . It remains unclear whether the same findings will occur after conventional surgery . Level of evidence II Purpose The objective of this prospect i ve study was to compare the functional outcome of conventional measured resection technique and computer-assisted gap balancing technique in TKA . Methods 140 patients were r and omized into two groups . The conventional measured resection technique without computer navigation was performed in Group 1 and the computer-assisted gap balancing technique in Group 2 . Range of motion , clinical laxity assessment with KT-1000 arthrometer , postoperative radiological films and various functional knee scores were documented at 6 months and 2 years . Results At 2 years , there were significantly more patients ( five patients , 7 % ) in the Group 1 with flexion contractures of more than 5 ° ( P = 0.05 ) . There were significantly more outliers in the Group 1 ( eight patients , 11 % ) , who demonstrated anterior tibial translation > 5 mm , than Group 2 ( two patients , 3 % ) ( P = 0.041 ) . The total excursion at 20 ° was significantly higher in Group 1 at 6 months ( P = 0.012 ) and after 2 years ( P = 0.031 ) . Group 2 was able to demonstrate significantly better limb alignment with fewer outliers ( more than 3 ° varus/valgus ) than Group 1 . At 6-month follow-up , Group 2 demonstrated better outcomes in Function Score ( P = 0.040 ) and Total Oxford Score ( P = 0.031 ) . At 2-year review , Group 2 had better outcome in the Total Oxford Score ( 0.030 ) . Conclusion Computer-assisted gap balancing technique was able to achieve more precise soft tissue balance and restoration of limb alignment with better knee scores as compared to the conventional measured resection technique in total knee arthroplasty . Level of evidence Background : There is ongoing debate about how to obtain correct rotational alignment in total knee arthroplasty ( TKA ) . Two commonly used techniques are the measured resection ( MR ) and the gap balancing ( GB ) technique . Objective : The objective of the present study was to analyze which of these two techniques confers a clinical advantage up to 10 years postoperatively . Methods : Two hundred patients were r and omized to either MR or GB .  The primary outcome was the Knee Society Knee Score ( KS ) 10 years postoperatively . Secondary outcomes were passive range of motion , the Knee Society Function Score ( FS ) , and the Western Ontario and McMasters Universities Osteoarthritis Index ( WOMAC ) , along with implant survival . We employed a two one-sided test ( TOST ) and linear mixed models to assess clinical outcomes . Results : Mean KS was 82 ( 95 % confidence interval ( CI ) , 80 – 83 ) and 77 ( 95 % CI , 76 – 79 ) in the GB and MR group , respectively . The TOST test and linear mixed model both revealed statistical significance ( p < 0.001 ) . In addition , GB yielded better postoperative FS and WOMAC . However , between-group differences were consistently small . Implant survival rates at 10 years , with survival for any reason as the endpoint of interest , were 93.7 % ( 95 % CI , 86.4 % and 97.1 % ) and 89.8 % ( 95 % CI , 81.9 % - 94.4 % ) for the GB group and the MR group , respectively ( p = 0.302 ) . Conclusion : Gap-balancing is a safe and reliable technique . KS for the two study groups at 10 years can be considered equivalent , and the small postoperative advantages may not extend beyond clinical relevance Purpose . To compare the 2-year outcome of  total knee arthroplasty ( TKA ) using the measured resection versus the gap balancing techniques . Methods . 21 men and 31 women aged 41 to 89 ( mean , 73 ) years who underwent primary TKA by a single surgeon for osteoarthritis and had an American Society of Anesthesiologists I or II physical status were prospect ively studied . Patients were r and omised to undergo computer-assisted TKA using the measured resection technique ( n=26 ) or the gap balancing technique ( n=26 ) . At the 2-year followup , patients were assessed by a single orthopaedic registrar blinded to the type of surgery using the Knee Society score ( KSS ) , functional Knee Society score ( FKSS ) , and revised Oxford Knee score ( ROKS ) . Results . In the measured resection group , the mean KSS , FKSS , and ROKS increased from 34.3 , 48 , and 21 to 85.9 , 89.6 , and 36.5 , respectively . In the gap balancing group , the respective scores increased from 35.4 , 50 , and 22.5 to 89.1 , 92.4 , and 40.6 . Postoperative with the gap balancing technique ; the respective p values were 0.46 , 0.44 , and 0.12 . Conclusion . Improvements in the knee scores were comparable with the 2 techniques BACKGROUND Distal femur torsion ( DFT ) is a crucial parameter in knee replacement surgery . The reference st and ard for measuring DFT is posterior condylar angle ( PCA ) measurement using computed tomography ( CT ) . The objective of this study was to assess the feasibility and reliability of a radiographic PCA measurement method . MATERIAL S AND METHODS We studied 125 osteoarthritic knees in 79 patients ( 42 women and 37 men ) with a mean age of 71.6 ± 8.8 years ( range 47 to 86 years ) ; 32 knees were aligned , 85 in varus , and eight in valgus .  DFT was measured on an antero-posterior ( AP ) radiograph of the knee in 90 ° of flexion ( known as the seated AP view ) . The PCA was defined as the angle subtended by the tangent to the posterior condyles and the transepicondylar axis ( anatomic PCA [ aPCA ] ) or the line connecting the lateral epicondyle to the medial sulcus ( surgical PCA [ sPCA ] ) . The PCA was conventionally recorded as positive in the event of external torsion and negative in the event of internal torsion . PCA measurements were performed three times by each of five observers to allow assessment s of inter-observer and test-retest reliabilities . RESULTS aPCA was consistently negative ( mean , -6.1 ± 1.6 ° ) ( range , 0 to -10 ° ) ; inter-observer and test-retest reliability were satisfactory ( 0.54<rw 0.80 ) . sPCA was positive in 41 knees and negative in 84 knees ) ( mean , -0.3 ± 1.4 ° ) ( range , -5 ° to + 2 ° ) ; inter-observer and test-retest reliabilities were poor ( 0.28<r<0.69 ) . A weak but significant correlation was found between aPCA and coronal alignment , with a trend towards greater internal torsion in the group of valgus knees . CONCLUSION Radiographic measurement of DFT is simple and non-invasive . Measurement reproducibility was satisfactory for aPCA but not for sPCA . aPCA showed marked inter-individual variability and tended to increase when the knee was in valgus . Mean aPCA values were comparable to those reported using CT . In contrast to CT , radiographic DFT measurement can easily be incorporated into the pre- and postoperative work-ups for knee replacement surgery , provided the patient can achieve 90 ° of knee flexion . LEVEL OF EVIDENCE Level IV , prospect i ve cohort study
target: The EKA Femoral Rotation Focus Group has not identified a single best reference method to determine femoral component rotation , but surgeons mostly prefer the measured resection technique using at least two l and marks for cross-checking the rotation .
background: Malrotation of the femoral component after primary total knee arthroplasty ( TKA ) is one of the most important problems leading to painful TKA requiring revision surgery .
  A comprehensive systematic review of the literature was performed to present current evidence on how to optimally place the femoral component in TKA .