Mediolateral oversizing influences pain, function, and flexion after TKA The value of FDG-PET in patients with painful total knee arthroplasty Physical activity and risk of revision total knee arthroplasty in individuals with knee osteoarthritis: a matched case-control study. Reliability of templating with patient-specific instrumentation in total knee arthroplasty. Patellar Tracking and Anterior Knee Pain are Similar After Medial Parapatellar and Midvastus Approaches in Minimally Invasive TKA Navigation of total knee arthroplasty: rotation of components and clinical results in a prospectively randomized study Component Rotation and Anterior Knee Pain After Total Knee Arthroplasty Comparison of Early Postoperative Rehabilitation Outcome following Total Knee Arthroplasty Using Different Surgical Approaches and Instrumentation Patient-specific Total Knee Arthroplasty Required Frequent Surgeon-directed Changes Computer-assisted total knee arthroplasty using mini midvastus or medial parapatellar approach technique Changed gait pattern in patients with total knee arthroplasty but minimal influence of tibial insert design Are undesirable contact kinematics minimized after kinematically aligned total knee arthroplasty? An intersurgeon analysis of consecutive patients Quadriceps-sparing, minimal-incision total knee arthroplasty: a comparative study. Patellar complications after knee arthroplasty. A prospective study of 56 cases using the Kinematic prosthesis. Patient-Specific CT-Based Instrumentation versus Conventional Instrumentation in Total Knee Arthroplasty: A Prospective Randomized Controlled Study on Clinical Outcomes and In-Hospital Data Mobile- versus fixed-bearing total knee arthroplasty: a prospective randomized controlled trial featuring 6-10-year follow-up. Is TKA Using Patient-specific Instruments Comparable to Conventional TKA? A Randomized Controlled Study of One System
Purpose Manufacturers of total knee arthroplasty ( TKA )  have introduced narrower femurs to improve bone-implant fit . However , few studies have reported the clinical consequences of mediolateral oversizing . Our hypothesis was that component oversizing negatively influences the results after TKA . Methods One hundred and twelve prospect ively followed patients with 114 consecutive TKA ( 64 females and 50 males ) were retrospectively assessed . The mean age of the patients was 72 years ( range , 56 to 85 years ) . The dimensions of the femur and tibia were measured on a preoperative CT-scan and were compared with those of the implanted TKA . The influence of size variation on the clinical outcomes 1 year after surgery was assessed . Results Mediolateral overhang was observed in at least one area in 66 % of the femurs ( 84 % in females and 54 % in males ) and 61 % of the tibia ( 81 % in females and 40 % in males ) . Twenty-two patients presented no overhang in any area and 16 had overhang in all studied zones . The increase in the Pain and KOOS scores were 43 ± 21 and 36 ± 18 in the patients without overhang and 31 ± 19 and 25 ± 13 in patients with overhang ( p = 0.033 ; p = 0.032 ) . Knee flexion was 127 ° ± 7 and 121 ° ± 11 , respectively . Regression and latent class analysis showed a significant negative correlation between overall oversizing and overall outcome . Conclusions This study confirms that oversizing may lead to worse clinical results in TKA . The clinical consequences are that surgeons should pay attention not to oversize implants during implantation nd that oversizing should be ruled out in case of so called unexplained pain . Level of evidence IV Purpose The purpose of this study was to evaluate 18F-fluorodeoxyglucose ( FDG ) uptake in patients with painful total knee arthroplasty and to relate FDG uptake to the location of soft tissue pain . Methods Twenty-eight patients with painful total knee arthroplasty had a clinical examination , st and ard radiographs , CT measurement of rotation of the femoral component and FDG-PET ( 18 PET/CT , 10 PET ) .  The diagnosis of infection was based on microbiological examinations of surgical specimens ( n=12 ) or clinical follow-up for at least 6 months ( n=16 ) , 99mTc-labelled monoclonal antibody scintigraphy and joint aspiration . Results Twenty-seven of 28 patients presented with diffuse synovial FDG uptake . Additional focal extrasynovial FDG uptake was observed in 19 knees . Twenty-four of the 28 patients had a diagnosis of internal femoral malrotation . The remaining four patients showed no rotation ( 0 ° ) and 3 ° , 4 ° and 7 ° of external rotation , respectively . Three patients presented with the additional diagnosis of an infected total knee replacement . Pain was described as diffuse ( n=10 ) or focal ( n=18 ) . In two knees a relationship between pain location and FDG uptake was observed . Of ten patients with a severe internal femoral component rotation ( > 6 ° ) , seven had focal uptake , four in the femoral periosteum and three in the tibial periosteum . The difference between knees with severe malrotation and the remaining knees was not significant ( p=1.000 , Fisher 's Exact Test ) . Conclusion Diffuse synovial and focal extrasynovial FDG-PET uptake is commonly found in patients with malrotation of the femoral component and is not related to pain location . The information provided by FDG-PET does not contribute to the diagnosis and management of individual patients with persistent pain after total knee replacement OBJECTIVE To determine if physical activity was a risk factor for revision arthroplasty after primary total knee arthroplasty ( TKA ) due to osteoarthritis ( OA ) within the previous 15 years . METHODS This was a matched case-control study . The cases had primary TKA followed by revision arthroplasty . Controls had primary TKA and no revision arthroplasty .  Cases and controls were matched for age , sex , number of knees replaced , and date of primary TKA . St and ardized telephone interviews were conducted to assess historical leisure activity , occupational activity , and instrumental activities of daily living  after primary TKA in metabolic equivalent (MET)-hours per week . Conditional logistic regression was performed to identify the variables that predicted the need for revision arthroplasty . RESULTS Seventeen female and 9 male pairs , aged 47 to 85 years , participated . Most of the reported activity was of low impact and low or moderate intensity . Cases reported a median of 44.5 ( range 0 to 137 ) MET-hours of total historical physical activity  per week compared with controls ' 55.1 ( range 0 to 278 ) MET-hours . Total historical physical activity was not associated with the risk of revision arthroplasty ( OR 0.99 , 95 % CI 0.99 - 1.01 ) . Participants with primary TKA ( controls ) consistently reported more MET-hours of leisure and occupational activity than those with revision arthroplasty ( cases ) regardless of the number of knees replaced or whether or not walking was accounted for . CONCLUSION This study quantified and described patterns of physical activity in a population with TKA . Physical activity did not appear to be a risk factor for revision arthroplasty . Our results suggest that individuals undergoing primary TKA should be encouraged to remain active after surgery Magnetic resonance imaging ( MRI ) or computed tomography-based patient-specific instrumentation ( PSI ) may allow for reliable alignment and fewer outliers when compared with conventionally instrumented total knee arthroplasty ( TKA ) . However , some authors have suggested that frequent intraoperative surgeon-directed changes may still be required . This study evaluated the accuracy of  PSI  to predict component sizing and alignment during TKA . A total of 84 patients ( 89 knees ) who underwent a TKA using a PSI system were evaluated . An MRI-based preoperative plan of every knee was provided and approved by the surgeons . This demonstrated the proposed prosthetic component alignment , as well as the femoral , tibial , and bearing insert component size and position . Intraoperative changes to these components were prospect ively recorded and compared with the computerized preoperative plan . Major changes were defined as any changes in femoral or tibial resection , size , and position of the components . Minor changes were defined as any change in the size of the polyethylene bearing insert . The preoperative plan was able to correctly predict the size of the implanted tibial and femoral component in 93 and 95.5 % of the cases , respectively . Thirteen major intraoperative changes were made . In one knee , the proposed femoral resection was not acceptable ( because of the presence of significant amount of osteophytes ) and was ab and oned in favor of a manual extramedullary guide . In another patient , the proposed femoral and tibial components were upsized . In two other patients , the femoral components were downsized , in four patients , the tibial components were downsized , and in another patient , it was upsized . There were also 16 minor changes , which included 2-mm upsizing of the polyethylene liner in 13 knees and 4-mm upsizing in 3 knees . Surgical experience is necessary to recognize improper component size , incorrect surgical resection , or nonideal alignment when performing TKA using PSI . The authors believe that the design and manufacture of PSI combined with a comprehensive templating result ed in excellent intraoperative concordance of the preoperative plan at the default setting s with minimal changes Background Since the medial parapatellar ( MPP ) approach in conventional TKA can cause patellar maltracking and anterior knee pain , some orthopaedic surgeons use the midvastus ( MV ) approach instead of the MPP approach to reduce patellar maltracking . Minimally invasive surgical ( MIS ) TKA has been developed to limit the damage to the surrounding muscle and reduce the necessity of patellar eversion during surgery . Thus , MIS TKA might be associated with proper patellar tracking and a low incidence of anterior knee pain . However , this presumption has not been confirmed . Questions / purpose sWe asked whether the incidence of patellar maltracking and anterior knee pain differed with the MV and MPP in association with MIS TKA . Methods We prospect ively followed 59 patients ( 60 knees ) treated with 60 primary cemented MIS TKAs from August 2009 to September 2010 . We r and omized the patients into two groups : 30 who had a limited MPP approach and 30 who had a mini-MV approach . We recorded the occurrence of anterior knee pain , patellar tilting , and subluxation . The minimum followup was 12 months ( mean , 18.03 months ; range , 12.00–25.08 months ) . Results We found no differences in anterior knee pain ( two of 30 , 7 % versus two of 30 , 7 % ) , mean patellar tilt ( 3.4º ± 2.9º versus 3.0 ± 2.3º ) , and mean patellar subluxation ( 1.5 ± 1.1 mm versus 1.1 ± 0.7 mm ) between the limited MPP and mini-MV groups , respectively . Conclusions MIS TKA using either the MPP or MV approach has a low incidence of patellar maltracking and anterior knee pain . Level of Evidence Level I , therapeutic study . See the Guidelines for Authors for a complete description of the levels of evidence Background Navigation was introduced into  total knee arthroplasty ( TKA ) to improve accuracy of component position , function and survival of implants . This study was design ed to assess the outcome of navigated TKA in comparison with conventional implantation with the focus on rotational component position and clinical mid-term results . Methods In a prospect ively r and omized single-blinded approach , 90 patients with primary gonarthrosis were assigned to three different groups . Thirty patients each were assigned to NexGen LPS without and with navigation ( groups 1 and 2 ) , and 30 patients to navigation with the Stryker Scorpio PS ( group 3 ) . The navigation system used was the imageless Stryker KneeTrac , version 1.0 . Clinical outcome was assessed by a blinded observer applying the Knee Society Score ( KSS ) and a visual analogue scale ( VAS ) for pain . CT scans and radiographs were conducted prior to and 12 weeks after index surgery . Results Seventy-nine patients were available for clinical evaluation at 3 ± 0.4 years follow-up . Four implants had to be revised for early loosening or infection ( 4.4 % ) . Four patients had died and three patients were not able to follow the invitation for clinical assessment . Functional results in the KSS were significantly lower after navigated TKA . Operation time and incisions with navigation were significantly longer . Significantly less radiological outliers with navigation were found for coronal alignment of the femur , only . Conclusion In this series , no beneficial effect for navigation in TKA could be shown assessing clinical data , as functional results in the presented series seemed to be lower after first generation navigated TKA . The clinical mid- to long-term value of navigation remains to be evaluated in larger patient series or meta-analyses at longer follow-up . Trial registration numberDRKS All patients undergoing cruciate-retaining primary total knee arthroplasty for degenerative osteoarthritis at one center were studied prospect ively . Clinical and radiographic followup was obtained at a minimum 5 years in 102 knees in 73 patients . Patients were asked specifically about the presence of the pain in the anterior aspect of the knee in the vicinity of the patella and rated the severity of the pain on a visual analog scale . Significant anterior knee pain rating at least 3 of 10 on the visual analog scale was present in 16 knees ( 13 patients ) . Eleven patients with 14 symptomatic knees agreed to undergo computed tomography scanning to accurately determine the rotation of the tibial and femoral components . The epicondylar axis and tibial tubercle were used as references using a previously vali date d technique . A control group of 11 asymptomatic patients ( 14 knees ) , matched for age , gender , and length of followup also underwent computed tomography scanning . All patients in both groups had normal axial alignment . There was a highly significant difference in  tibial component rotation between the two groups with the patients with anterior knee pain averaging 6.2 ° internal rotation compared with 0.4 ° external rotation in the control group . There also was a significant difference in  combined component rotation  with the patients with anterior knee pain averaging 4.7 ° internal rotation compared with 2.6 ° external rotation in the control group . There was no significant difference in the degree of radiographic patellar tilt or patellar subluxation between the two groups . Patients with combined component internal rotation were more than five times as likely to experience anterior knee pain after total knee arthroplasty compared with those with combined component external rotation . Component malrotation is a significant factor in the development of anterior knee pain after total knee arthroplasty Purpose . To assess early postoperative rehabilitation outcome following  computer-assisted total knee arthroplasty ( TKA )  or st and ard instrumentation TKA using a medial parapatellar or subvastus approach . Methods . A prospect i ve controlled trial of 70 consecutive patients undergoing TKA with a low contact stress rotating platform prosthesis was conducted . Patients were r and omised to receive surgery with either computer navigation or st and ard instrumentation .  A medial parapatellar or subvastus approach was used according to the surgeons ' preference . Outcome measures included preoperative knee function , intra-operative factors , and postoperative rehabilitation . Results . Duration of surgery was significantly longer when using computer navigation ; however , operating time decreased with greater experience . A higher incidence and duration of early postoperative quadriceps dysfunction was associated with computer-assisted TKA through the medial parapatellar approach than through the subvastus approach or TKA performed with st and ard instrumentation . No patient who received surgery through the subvastus approach had a lag of more than 20 degrees , at 48 hours postoperatively , regardless of the instrumentation used . Conclusion . Computer-assisted TKA through a medial parapatellar approach was associated with delayed recovery of the quadriceps during early postoperative rehabilitation . This was due to the additional quadriceps dissection required to place the femoral tracking array . The subvastus approach is therefore recommended for computer-assisted TKA Background Patient-specific instrumentation potentially improves surgical precision and decreases operative time in total knee arthroplasty ( TKA ) but there is little supporting data to confirm this presumption . Questions / purpose sWe asked whether patient-specific instrumentation would require infrequent intraoperative changes to replicate a single surgeon ’s preferences during TKA and whether patient-specific instrumentation guides would fit securely . Methods We prospect ively evaluated the plan and surgery in 60 patients treated with 66 TKAs performed with patient-specific instrumentation and recorded any changes . A subset of six postoperative radiographic changes to the femoral and tibial components ( implant size , coronal and sagittal alignment ) was analyzed to determine if surgeon intervention was beneficial . Each guide was evaluated to determine fit . We compared patient demographics and implant sizing in the patient-specific instrumentation group with a control group in which traditional instrumentation was used . Results We recorded 161 intraoperative changes in 66 knee arthroplasties ( 2.4 changes/knee ) performed with patient-specific instrumentation . The predetermined implant size was changed intraoperatively in 77 % of femurs and 53 % of tibias . We identified a subset of 95 intraoperative changes that could be radiographically evaluated to determine if our changes were an improvement or detriment to reaching goal alignment . Eighty-two of the 95 changes ( 86 % ) made by the surgeon were an improvement to the recommended alignment or size of patient-specific instrumentation . The guide did not fit securely on eight femurs ( 12 % ) and three tibias ( 5 % ) . Tourniquet time and blood loss were not improved with patient-specific instrumentation . Conclusions We caution surgeons against blind acceptance of patient-specific instrumentation technology without supportive data .Level of Evidence Level III , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence Background Despite the growing evidence in the literature there is still a lack of consensus regarding the use of minimally invasive surgical technique ( MIS ) in total knee arthroplasty ( TKA ) . Methods A prospect i ve , r and omized , international multicentre trial including 69 patients was performed to compare computer-assisted TKA ( CAS-TKA ) using either mini-midvastus ( MIS group ) or st and ard medial parapatellar approach ( conventional group ) .  Patients from 3 centers ( Maastricht , Zwickau , Adelaide ) with end-stage osteoarthritis of the knee were r and omized to either an MIS group with dedicated instrumentation or a conventional group to receive cruciate retaining CAS-TKA without patella resurfacing .  The primary outcome was to compare post operative pain and range of motion ( ROM ) . The secondary outcome was to measure the duration of surgery , blood loss , chair rise test , quadriceps strength , anterior knee pain , Knee Society Score (KSS),WOMAC scores , mechanical leg axis and component alignment . Results Patients in the MIS group ( 3.97 ± 2.16 ) had significant more pain at 2 weeks than patients in the conventional group ( 2.77 ± 1.43 ) p = 0.003 . There was no significant difference in any of the other primary outcome parameters . Surgery time was significantly longer ( p < 0.001 ) and there were significantly higher blood loss ( p = 0.002 ) in the MIS group as compared to the conventional group . The difference of the mean mechanical leg alignment between the groups was not statistically significant ( –0.43 ° ( 95 % CI –1.50 – 0.64 ) ; p = 0.43).There was no significant difference of component alignment between the two surgical groups with respect to flexion/extension ( p = 0.269 ) , varus/valgus ( p = 0.653 ) or rotational alignment ( p = 0.485 ) of the femur component and varus valgus alignment ( p = 0.778 ) or posterior slope ( p = 0.164 ) of the tibial component . Conclusion There was no advantage of the MIS approach compared to a conventional approach CAS-TKA in any of the primary outcome measurements assessed , however the MIS approach was associated with longer surgical time and greater blood loss . MIS-TKA in combination with computer navigation is safe in terms of implant positioning . Trial registration number Clinical Trials.gov NCT02625311 8 December Introduction Previous radiostereometric studies have revealed abnormal anterior-posterior translation of the femur in patients operated with AMK ( DePuy , Johnson and Johnson , Leeds , UK ) total knee arthroplasty ( TKA ) . Based on these observations , we hypothesized that patients with TKA have an abnormal gait pattern , and that there are differences in kinematics depending on the design of the tibial joint area . Method We used a gait analysis system to evaluate the influence of joint area design on the kinematics of the hip and knee during level walking .  39 TKA patients ( 42 knees ) and 18 healthy age-matched controls were studied . Patients with 5 ° varus/valgus alignment or less were r and omized to receive either a relatively flat or a concave tibial insert with retention of the posterior cruciate ligament .  Patients who had more than 5 ° varus-valgus alignment and /or extension defect of 10 ° or more were r and omized to receive the concave or a posterior-stabilized tibial component with resection of the posterior cruciate ligament . Results Patients with TKA tended to have less hip and knee extension and decreased knee and hip extension moment than controls . They also tended to walk more slowly . TKA altered the gait pattern , but choice of implant design had little influence . Interpretation In patients with a similar degree of degenerative joint disease and within the limits of the constraints offered by the prostheses under study , the choice of joint area constraint has little influence on the gait pattern Purpose Tibiofemoral contact kinematics or knee implant motions have a direct influence on patient function and implant longevity and should be evaluated for any new alignment technique such as kinematically aligned total knee arthroplasty ( TKA ) . Edge loading of the tibial liner and external rotation ( reverse of normal ) and adduction of the tibial component on the femoral component are undesirable contact kinematics that should be minimized . Accordingly , this study determined whether the overall prevalence of undesirable contact kinematics during st and ing , mid kneeling near 90 degrees and full kneeling with kinematically aligned TKA are minimal and not different between groups of consecutive patients treated by different surgeons . Methods Three surgeons were asked to perform cemented , kinematically aligned TKA with patient-specific guides in a consecutive series of patients with their preferred cruciate-retaining ( CR ) implant .  In vivo tibiofemoral contact positions were obtained using a 3- to 2-dimensional image registration technique in 69 subjects ( Vanguard CR – TKA N = 22 , and Triathlon CR – TKA N = 47 ) . Results Anterior or posterior edge loading of the tibial liner was not observed . The overall prevalence of external rotation of the tibial component on the femoral component of 6 % was low and not different between surgeons ( n.s . ) . The overall prevalence of adduction of the tibial component on the femoral component of 4 % was low and not different between surgeons ( n.s . ) . Conclusions Kinematically aligned TKA minimized the undesirable contact kinematics of edge loading of the tibial liner , and external rotation and adduction of the tibial component on the femoral component during st and ing and kneeling , which suggests an optimistic prognosis for durable long-term function . Level of evidence III Our study was conducted to compare radiographic alignments and functional outcomes with 2 approaches to minimal-incision total knee arthroplasty ( TKA ) : the minimal-incision medial parapatellar ( MP ) approach and the quadriceps-sparing ( QS ) approach with side-cutting instruments . Sixty patients ( 80 knees ) with primary osteoarthritis were r and omly assigned to receive MP or QS TKA .  Postoperative alignment of the femoral component was significantly less valgus , and postoperative alignment of the tibial component was significantly more varus with the QS approach than with the MP approach . One tibial outlier and 3 femoral outliers were observed with QS TKA . The overall postoperative hip-knee-ankle axis was more varus , and surgical time was longer with QS TKA .  Short-term isokinetic peak muscle torque , postoperative pain , and functional outcomes did not differ between the approaches A prospect i ve study on 56 knees was performed to analyze the incidence and cause of  patellar complications following total knee arthroplasty with the Kinematic prosthesis inserted with the Universal Instrumentation system .  Patellar complications occurred in 23 cases : 15 had anterior knee pain .  There was 1 case of patellar fracture . Subluxation of the patella occurred in 13 cases , of which 6 were painful . Although the mechanical alignment was correctly reconstructed to neutral in all but 2 cases , the instrumentation tended to allow malpositioning of the components into excessive femoral valgus and compensatory excessive tibial varus that predisposed to patellar subluxation . With this prosthesis and instrumentation , patellar stability is hindered by a very short anterior femoral flange , a shallow patellar groove , and insertion of the components at 3 degrees to the mechanical axis . It should be ensured that the components are correctly positioned , that patellar stability is carefully checked before closing the capsule , and that lateral release is performed more often Total knee arthroplasty ( TKA ) is a frequently performed procedure in orthopaedic surgery . Recently , patient-specific instrumentation was introduced to facilitate correct positioning of implants . The aim of this study was to compare the early clinical results of TKA performed with patient-specific CT-based instrumentation and conventional technique . A prospect i ve , r and omized controlled trial on 112 patients was performed between January 2011 and December 2011 . A group of 112 patients who met the inclusion and exclusion criteria were enrolled in this study and r and omly assigned to an experimental or control group . The experimental group comprised 52 patients who received the Signature CT-based implant positioning system , and the control group consisted of 60 patients with conventional instrumentation .  Clinical outcomes were evaluated with the KSS scale , WOMAC scale , and VAS scales to assess knee pain severity and patient satisfaction with the surgery . Specified in-hospital data were recorded . Patients were followed up for 12 months . At one year after surgery , there were no statistically significant differences between groups with respect to clinical outcomes and in-hospital data , including operative time , blood loss , hospital length of stay , intraoperative observations , and postoperative complications . Further high- quality investigations of various patient-specific systems and longer follow-up may be helpful in assessing their utility for TKA OBJECTIVE The purpose of this study was to compare long-term clinical and radiographic outcomes of mobile- ( MB ) and fixed-bearing ( FB ) total knee arthroplasties ( TKA ) . METHODS A r and omized controlled study was conducted to compare the clinical and radiographic outcomes of MB and FB prostheses in 93 consecutive patients who underwent primary TKA for knee osteoarthritis . Mean follow-up of the patients was 100.9 months in the MB group ( range : 78 - 121 months ) and 93.7 months ( range : 78 - 120 months ) in the FB group . The clinical results were grade d according to the Knee Society Knee Score ( KSKS ) and the Knee Society Functional Score ( KSFS ) . Secondary outcomes included pain , patellofemoral joint function , quality of life ( QOL ) , and radiologic outcomes ( Knee Society 's roentgenographic evaluation system ) . RESULTS Although there was significant improvement in both groups , there were no significant differences between the groups with respect to mean KSFS and radiologic outcomes . However , mean pain score of the MB group was significantly higher than that of the FB group ( 48.83±0.62 vs 47.39±0.86 , respectively , p=0.011 ) , and mean KSKS was significantly higher than that of the FB group ( 93.5±6.2 vs 89.7±6.9 , respectively , p=0.007 ) . CONCLUSION TKA clinical results were satisfactory in both the MB and FB groups . KSKS and pain scores were significantly better in the MB than in the FB group . However , no differences were found in other assessment s. Thus , we conclude that the best design is the one with which the surgeon is most comfortable and most able to implant reproducibly Background Patient-specific CT-based instrumentation may reduce implant malpositioning and improve alignment in TKA . However , it is not known whether this innovation is an advance that benefits patients . Questions / purpose sWe evaluated ( 1 ) the precision of  patient-specific TKA by comparing the incidence of outliers in postoperative alignment between TKAs using  patient-specific instruments  and TKAs using conventional instruments , and ( 2 ) the reliability of patient-specific instruments by intraoperatively investigating whether the surgery could be completed with patient-specific instruments alone . Methods In this r and omized controlled trial , we compared  patient-specific TKA instruments from one manufacturer ( n = 50 ) with conventional TKA instruments ( n = 50 ) . Postoperative hip-knee-ankle angles , femoral component rotation , and coronal and sagittal alignments of each component were measured . The validity of the patient-specific instrument was examined using cross-checking procedures with conventional instruments during the surgeries . When the procedure could not be completed accurately with patient-specific instruments , the procedure was converted to TKA using conventional instruments , and the frequency of this occurrence was tallied . Results Outliers in the hip-knee-ankle angle were comparable between groups ( 12 % in the patient-specific instrument group and 10 % in the conventional instrument group ) . Other parameters such as sagittal alignment and femoral component rotation did not differ in terms of outliers . Patient-specific guides were ab and oned in eight knees ( 16 % ) during the surgery because of malrotation of the femoral components and decreased slope of the tibia . Conclusions Accuracy was comparable between TKAs done with patient-specific instruments and those done with conventional instruments . However , the patient-specific instrument procedures had to be aborted frequently , incurring expenses that did not benefit patients .Level of Evidence Level II , therapeutic study . See Instructions for Authors for a complete description of levels of evidence
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 .
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 .