A randomised controlled trial of the clinical effectiveness and cost-effectiveness of different knee prostheses: the Knee Arthroplasty Trial (KAT). Randomized clinical trial of rotating-platform and fixed-bearing total knee arthroplasty: no clinically detectable differences at five years. Problems With Cementless Total Knee Arthroplasty at 11 Years Followup Should we reconsider all-polyethylene tibial implants in total knee replacement? Cement or Cementless Fixation in Total Knee Arthroplasty? Lateral unicompartmental knee replacement: fixed or mobile bearing? Proximally cemented versus uncemented Freeman-Samuelson knee arthroplasty. A prospective randomised study. The Knee Arthroplasty Trial (KAT) design features, baseline characteristics, and two-year functional outcomes after alternative approaches to knee replacement. Rotating Platform Knees Did Not Improve Patellar Tracking: A Prospective, Randomized Study of 240 Primary Total Knee Arthroplasties The Outcome of the Cementless Tibial Component: A Minimum 14-Year Clinical Evaluation Deep-Dish Congruent Tibial Component Use in Total Knee Arthroplasty: A Randomized Prospective Study Reliability of templating with patient-specific instrumentation in total knee arthroplasty. Inferior performance of Boneloc bone cement in total knee arthroplasty: a prospective randomized study comparing Boneloc with Palacos using radiostereometry (RSA) in 19 patients. Prosthesis alignment affects axial rotation motion after total knee replacement: a prospective in vivo study combining computed tomography and fluoroscopic evaluations Prospective results of uncemented tantalum monoblock tibia in total knee arthroplasty: minimum 5-year follow-up in patients younger than 55 years. Mobile-bearing insert translational and rotational kinematics in a PCL-retaining total knee arthroplasty. Are undesirable contact kinematics minimized after kinematically aligned total knee arthroplasty? An intersurgeon analysis of consecutive patients Mobile vs. fixed meniscal bearing in total knee replacement: a randomised radiostereometric study. Mobile and fixed-bearing (all-polyethylene tibial component) total knee arthroplasty designs. A prospective randomized trial. Cemented tibial component fixation performs better than cementless fixation Hydroxyapatite coating versus cemented fixation of the tibial component in total knee arthroplasty: prospective randomized comparison of hydroxyapatite-coated and cemented tibial components with 5-year follow-up using radiostereometry. Cemented versus cementless Oxford unicompartmental knee arthroplasty using radiostereometric analysis: a randomised controlled trial. The Effect of Hydroxyapatite on the Micromotion of Total Knee Prostheses. A Prospective, Randomized, Double-Blind Study*
BACKGROUND In the late 1990s , new developments in knee replacement were identified as a priority for research within the NHS . The newer forms of arthroplasty were more expensive and information was needed on their safety and cost-effectiveness . OBJECTIVES The Knee Arthroplasty Trial examined the clinical effectiveness and cost-effectiveness of four aspects of knee replacement surgery : patellar resurfacing , mobile bearings , all-polyethylene tibial components and unicompartmental replacement . DESIGN This study comprised a partial factorial , pragmatic , multicentre r and omised controlled trial with a trial-based cost-utility analysis which was conducted from the perspective of the NHS and the patients treated . Allocation was computer generated in a 1 : 1 ratio using a central system , stratified by eligible comparisons and surgeon , minimised by participant age , gender and site of disease . Surgeons were not blinded to allocated procedures . Participants were unblinded if they requested to know the prosthesis they received . SETTING The setting for the trial was UK secondary care . PARTICIPANTS Patients were eligible for inclusion if a decision had been made for them to have primary knee replacement surgery . Patients were recruited to comparisons for which the surgeon was in equipoise about which type of operation was most suitable . INTERVENTIONS Patients were r and omised to receive a knee replacement  with the following : patellar resurfacing or no patellar resurfacing irrespective of the design of the prosthesis used ; a mobile bearing between the tibial and femoral components or a bearing fixed to the tibial component ; a tibial component made of either only high-density polyethylene ( ' all polyethylene ' ) or a polyethylene bearing fixed to a metal backing plate with attached stem ; or unicompartmental or total knee replacement . MAIN OUTCOME MEASURES The primary outcome was the Oxford Knee Score ( OKS ) . Other outcomes were Short Form 12 ; EuroQol 5D ; intraoperative and postoperative complications ; additional surgery ; cost ; and cost-effectiveness . Patients were followed up for a median of 10 years ; the economic evaluation took a 10-year time horizon , discounting costs and quality -adjusted life-years ( QALYs ) at 3.5 % per annum . RESULTS A total of 116 surgeons in 34 centres participated and 2352 participants were r and omised : 1715 in patellar resurfacing ; 539 in mobile bearing ; 409 in all-polyethylene tibial component ; and 34 in the unicompartmental comparisons . Of those r and omised , 345 were r and omised to two comparisons . We can be more than 95 % confident that patellar resurfacing is cost-effective , despite there being no significant difference in clinical outcomes , because of increased QALYs [ 0.187 ; 95 % confidence interval ( CI ) -0.025 to 0.399 ] and reduced costs ( -£104 ; 95 % CI -£630 to £ 423 ) . We found no definite advantage or disadvantage of mobile bearings in OKS , quality of life , reoperation and revision rates or cost-effectiveness . We found improved functional results for metal-backed tibias : complication , reoperation and revision rates were similar . The metal-backed tibia was cost-effective ( particularly in the elderly ) , costing £ 35 per QALY gained . CONCLUSIONS The results provide evidence to support the routine resurfacing of the patella and the use of metal-backed tibial components even in the elderly . Further follow-up is required to assess the stability of these findings over time and to inform the decision between mobile and fixed bearings . TRIAL REGISTRATION Current Controlled Trials IS RCT N45837371 . FUNDING This project was funded by the NIHR Health Technology Assessment programme and the orthopaedic industry . It will be published in full in Health Technology Assessment ; Vol . 18 , No. 19 . See the NIHR Journals Library website for further project information BACKGROUND For some surgeons , rotating-platform total knee design s are an intellectually appealing option to use for total knee arthroplasty because of the contention that they can self-align and accommo date small mismatches in the rotational position of the tibial and femoral components . We carried out a r and omized clinical trial to determine if a posterior-stabilized , rotating-platform knee design provided better maximum knee flexion , better function , or better durability at five years of follow-up when compared with a fixed-bearing design . METHODS This r and omized clinical trial of 240 primary total knee arthroplasties involved a single type of distal femoral implant ( posterior-stabilized ) and three different types of tibial implant ( all-polyethylene fixed-bearing , modular-metal-backed fixed-bearing , and rotating-platform ) . The three tibial implant groups were balanced dynamically with a computerized r and omization process that accounted for patient age , sex , and body mass index ; surgeon ; and implant type . Patients returned for examination and radiographs at three months , one year , two years , and five years postoperatively . RESULTS Knee range of motion was not significantly different among the all-polyethylene , modular-metal-backed , and rotating-platform tibial component groups at two years ( mean , 111 ° , 111 ° , and 110 ° , respectively ) or five years ( mean , 110 ° , 109 ° , and 109 ° , respectively ) . Function , as measured with Knee Society scores , was not significantly different among the all-polyethylene , modular-metal-backed , and rotating-platform groups at two years ( mean , 90 , 91 , and 91 points , respectively ) or five years ( mean , 88 , 89 , and 88 points , respectively ) . Stair-climbing scores were not significantly different among the three groups at two years ( mean , 39 , 40 , and 39 points , respectively ) or five years ( mean , 37 , 40 , and 36 points , respectively ) . There were four revisions : one in the all-polyethylene group ( patellar fracture ) , two in the modular-metal-backed group ( aseptic loosening ) , and one in the rotating-platform group ( deep infection ) . CONCLUSIONS In this r and omized clinical trial , the rotating-platform total knee design was reliable and durable but did not provide better maximum knee flexion , better function , or better durability at five years postoperatively when compared with a posterior-stabilized , fixed-bearing design incorporating either an all-polyethylene or a modular-metal-backed tibial component One hundred two patients with 131 consecutive cementless total knee arthroplasties that retained the posterior cruciate ligament were followed up prospect ively . The average age of the patients was 58 years ( range , 32–75 years ) . The mean followup on the surviving knee arthroplasties was 11 years ( range , 7–16 years ) . The patellar component was metal-backed in the first 112 ( 85 % ) knees , cementless all-polyethylene in the last 17 ( 13 % ) knees , and two knees had a prior patellectomy . Forty-four metal-backed patellar components ( 48 % ) were revised ; nine were loose , and 35 had polyethylene wear through . Thirteen femoral components ( 12 % ) were revised because of femoral abrasion from a failed metal-backed patellar component . No other femoral component was revised , loose , or had osteolysis develop . Nine ( 8 % ) tibial components had failure of ingrowth ; eight have been revised . Partial radiolucencies occurred in 53 % of the tibias . Thirteen ( 12 % ) small osteolytic lesions developed , all around screws or screw holes in the tibial components . At an average of 11 years followup , cementless fixation yielded mixed results : cementless femoral fixation was excellent and metal-backed patellar components had a 48 % patellar revision rate . Cementless tibial components had an 8 % aseptic loosening rate and a 12 % incidence of small osteolytic lesions . Based on these results , the authors have ab and oned cementless fixation in total knee arthroplasty The role of modular tibial implants in total knee replacement is not fully defined . We performed a prospect i ve r and omised controlled clinical trial using radiostereophotogrammetric analysis to compare the performance of an all-polyethylene tibia with a metal-backed cruciate-retaining condylar design , PFC-Sigma total knee replacement for up to 24 months . There were 51 patients who were r and omised into two treatment groups . There were 10 subsequent withdrawals , leaving 21 all-polyethylene and 20 metal-backed tibial implants . No patient was lost to follow-up . There were no significant demographic differences between the groups . At two years one metal-backed implant showed migration > 1 mm , but no polyethylene implant reached this level . There was a significant increase in the SF-12 and Oxford knee scores after operation in both groups . In an uncomplicated primary total knee replacement the all-polyethylene PFC-Sigma tibial prosthesis showed no statistical difference in migration from that of the metal-backed counterpart . There was no difference in the clinical results as assessed by the SF-12 , the Oxford knee score , alignment or range of movement at 24 months , although these assessment measures were not statistically powered in this study A prospect ively studied group of 59 knees with cementless fixation were compared to a retrospectively studied but matched group of 59 knees with cement fixation using a Press Fit Condylar prosthesis .  The only significant preoperative difference between the patient groups was mean age ; the cemented group was on average nine years older than the cementless group ( p < 0.0001 ) . At an average of 2.8 years after surgery , there were no significant differences in knee scores between the two groups . Radiolucent lines adjacent to the tibial component were similar in both groups . The complication rate of 20 % in the cementless knees was higher than the 12 % rate in the cemented knees ; this was primarily related to polyethylene wear of metal-backed patellar components . Cement or cementless fixation of this prosthesis appears to provide equivalent early results 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 We studied the effect of a layer of cement placed under the tibial component of Freeman-Samuelson total knee prostheses  with a metal back and an 80 mm intramedullary stem , using roentgen stereophotogrammetry to measure the migration of the tibial component during one year in 13 uncemented and 16 cemented knees . The addition of cement produced a significant reduction in migration at one year , from a mean of 1.5 mm to one of 0.5 mm ( p less than 0.01 ) , including a significant reduction in pure subsidence . One year postoperatively the clinical results were similar between the groups , but , at three years , one uncemented knee had required revision BACKGROUND The aim of continued development of total knee replacement systems has been the further improvement of the quality of life and increasing the duration of prosthetic survival . Our goal was to evaluate the effects of several design features , including metal backing of the tibial component , patellar resurfacing , and a mobile bearing between the tibial and femoral components , on the function and survival of the implant . METHODS A pragmatic , multicenter , r and omized , controlled trial involving 116 surgeons in thirty-four centers in the United Kingdom was performed ; 2352 participants were r and omly allocated to be treated  with or without a metal backing of the tibial component ( 409 ) , with or without patellar resurfacing ( 1715 ) , and /or with or without a mobile bearing ( 539 ) . R and omization to more than one comparison was allowed . The primary outcome measures were the Oxford Knee Score ( OKS ) , Short Form-12 , EuroQol-5D , and the need for additional surgery . The results up to two years postoperatively are reported . RESULTS Functional status and quality -of-life scores were low at baseline but improved markedly across all trial groups following knee replacement ( mean overall OKS , 17.98 points at baseline and 34.82 points at two years ) . Most of the change was observed at three months after the surgery . Six percent of the patients had additional knee surgery within two years . There was no evidence of differences in clinical , functional , or quality -of-life measures between the r and omized groups at two years . CONCLUSIONS Patients have substantial improvement following total knee replacement . This is the first adequately powered r and omized controlled trial , of which we are aware , in which the effects of metal backing , patellar resurfacing , and a mobile bearing were investigated . We found no evidence of an effect of these variants on the rate of early complications or on functional recovery up to two years after total knee replacement Renewed interest in mobile-bearing total knee replacement design s has been generated by the concept of self alignment and the suggestion that those design s can accommo date small mismatches in the rotational position of the tibial and femoral components . Self alignment might improve patellar tracking , decrease the prevalence of lateral retinacular release and postoperative patellar tilt or subluxation , improve knee flexion , and improve patellofemoral function during daily activities such as stair climbing . This prospect i ve r and omized study of 240 patients used a single posterior-stabilized femoral component  and included three groups of 80 patients : an  all-polyethylene group , a modular metal-backed group , and a rotating platform tibia group . The prevalence of lateral retinacular release was 3.8 % in each group . The prevalence of patellar tilt was 5 % ( all-polyethylene group ) , 7 % ( modular metal-backed group ) , and 11 % ( rotating platform group ) . Preoperative motion was not significantly different and both the 3-month flexion ( 112 ° , 110 ° , and 108 ° ) and 1-year flexion ( 116 ° , 117 ° , and 115 ° ) were not significantly different among the all-polyethylene , modular metal-backed , and rotating platform groups , respectively . Preoperative stair climbing scores were not significantly different and both the 3-month ( 38 , 41 , and 35 points ) and 1-year ( 44 , 46 , and 42 points ) scores were not significantly different . In this prospect i ve r and omized study , the rotating platform knee design did not decrease the prevalence of lateral retinacular release or patellar tilt or subluxation and did not increase knee flexion or improve stair climbing ability at 3 months or at 1 year postoperatively when compared with a posterior-stabilized , fixed-bearing knee The long term survival of the Miller-Galante I cementless total knee arthroplasty  was evaluated by study ing prospect ively for a minimum of 14 years ( range , 14–17 years ) , 124 consecutive cementless total knee arthroplasties using a Miller-Galante I prosthesis in 99 patients with a mean age of 62 years who had primary or secondary osteoarthritis .  Knee function and roentgenograms were evaluated using the Knee Society criteria . Kaplan-Meier survivorship analysis was conducted . Five patients ( five knees ) were lost to followup ; six patients died with six knees in place . Fifteen knees ( 15 patients ) failed and were revised . Thirteen metal-backed patellas were revised . Eight of these revisions also required exchange of the femoral component , but only one tibial tray was revised . One knee ( one patient ) was revised for an infection . Of the 98 knees not revised ( 73 patients ) observed throughout this study , the average preoperative knee score was 31 ( range , 0–47 ) ; postoperatively , the average knee score was 91 ( range , 72–100 ) . The average function score improved from 28 ( range , 10–45 ) to 84 ( range , 50–100 ) . Twenty-four tibial trays ( 21 % ) and twenty femoral components ( 17 % ) of the 113 knees studied showed osteolysis . This study indicates that osteointegration of cementless tibial components can be successful with screw fixation , although there is a worrisome incidence of tibial and femoral osteolysis . The overall knee survival rate was 87 % ; however , the tibial component had a survival of 99 % One hundred seventy-six patients with osteoarthritis of the knee were r and omized prospect ively into two groups . In both groups the posterior cruciate ligament was released from its femoral attachment . In one group a posterior stabilized tibial component was used whereas in the other group a deep-dish tibial polyethylene component was inserted ( Genesis II ) . The surgical and perioperative technique was identical in both groups and all the implants were cemented to their respective bones . Patients began range of motion exercises within the first few hours after surgery and were allowed weightbearing to tolerance beginning on the first postoperative day . At followup there was no statistical difference in the mean range of flexion ( approximately 116 ° ) , ability to ascend and descend stairs in a bipedal manner ( 80 % ) , pain scores , knee scores ( 94 points ) , stability , or the lack of anterior knee pain . Postoperative implant alignment in the sagittal and coronal planes and on Merchant skyline views was excellent in both groups . There was only one lateral release required and that was in one patient who received a deep-dish component . Using deep-dish implant obviates the need to resect intercondylar femoral bone , decreasing the potential for fracture and maximizing bone volume should revision be necessary in the future 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 We compared Boneloc bone cement with conventional cement ( Palacos ) in fixating the tibial component during 2 - 5 years in 19 patients with gonarthrosis undergoing total knee arthroplasty in a prospect i ve r and omized study .  Boneloc displayed significantly larger migration , subsidence and lift-off than Palacos . The difference was identifiable already within 3 months postoperatively , but became significant at 12 months . In the Boneloc group , all components showed subsidence of the posterior part and lift-off of the anterior part of the tibial component , whereas in the Palacos group , the locations of subsidence and lift-off were evenly distributed about the edge of the implant . At 5 years , both Boneloc knees so far investigated were clinical failures with high migration rates . We conclude that , even in total knee arthroplasty , there is a substantial risk that Boneloc leads to inferior clinical results , but later than in hip replacements Background Clinical consequences of alignment errors in  total knee replacement ( TKR ) have led to the rigorous evaluation of surgical alignment techniques . Rotational alignment in the transverse plane has proven particularly problematic , with errors due to component malalignment relative to bone anatomic l and marks and an overall mismatch between the femoral and tibial components ’ relative positions . Ranges of nominal rotational alignment are not well defined , especially for the tibial component and for relative rotational mismatch , and some studies advocate the use of mobile-bearing TKR to accommo date the result ing small rotation errors . However , the relationships between prosthesis rotational alignment and mobile-bearing polyethylene insert motion are poorly understood . This prospect i ve , in vivo study evaluates whether component malalignment and mismatch affect axial rotation motions during passive knee flexion after TKR . Methods Eighty patients were implanted with mobile-bearing TKR .  Rotational alignment of the femoral and tibial components was measured from postoperative CT scans . All TKR were categorized into nominal or outlier groups based on defined norms for surgical rotational alignment relative to bone anatomic l and marks and relative rotational mismatch between the femoral and tibial components . Axial rotation motion of the femoral , tibial and polyethylene bearing components was measured from fluoroscopic images acquired during passive knee flexion . Results Axial rotation motion was generally accomplished in two phases , dominated by polyethylene bearing rotation on the tibial component in early to mid-flexion and then femoral component rotation on the polyethylene articular surface in later flexion . Opposite rotations of the femur-bearing and bearing-baseplate articulations were evident at flexion greater than 80 ° . Knees with outlier alignment had lower magnitudes of axial rotation and distinct transitions from external to internal rotation during mid-flexion . Knees with femoral-tibial rotational mismatch had significantly lower total axial rotation compared to knees with nominal alignment . Conclusions Maintaining relative rotational mismatch within ±5 ° during TKR provided for controlled knee axial rotation during flexion . TKR with rotational alignment outside of defined surgical norms , with either positive or negative mismatch , experienced measurable kinematic differences and presented different patterns of axial rotation motions during passive knee flexion compared to TKR with nominal mismatch . These findings support previous studies linking prosthesis rotational alignment with inferior clinical and functional outcomes .Trial Registration Clinical Trials A significant increase in younger patients undergoing total knee arthroplasty raises the theoretical concern for revision secondary to micromotion and fixation failure with cemented components . We prospect ively studied 100 consecutive tantalum monoblock uncemented tibial components and 312 concurrent cemented controls . Patients younger than 55 years with adequate bone stock were enrolled . This cementless patient group was younger and had higher preoperative functional status . Prostheses were posterior-substituting uncemented femoral and tibial components with a cemented patellar button .  Knee Society pain and function scores and radiographs were obtained , and a cost analysis was performed . Knee Society scores were excellent and equivalent beyond 6 months . There was no significant difference in perioperative blood loss , complication rates , or cost . There was a significant decrease in operative time in the uncemented group . Radiographs revealed no failures of ingrowth at last follow-up . There were 3 uncemented group failures , but none were due to failure of fixation . The use of a porous tantalum tibia at minimum 5 years has yielded promising clinical and radiographic results in a younger patient population INTRODUCTION  Total knee prostheses  with a mobile-bearing insert were developed to provide nonconstrained joint range of motion while reducing friction forces . The purpose of this study was , based on weightbearing X-rays , to evaluate the mobility of the polyethylene tibial insert in relation to the femoral and tibial components . We studied the results of a cementless total knee arthroplasty ( TKA ) retaining the posterior cruciate ligament ( PCL ) , with a mobile-bearing platform in rotation and anteroposterior translation ( Innex Anterior-Posterior Glide , Zimmer ) with a mean 23-month follow-up duration after surgery . HYPOTHESIS Both anterior-posterior tibiofemoral translation and intraprosthetic axial rotation occur between the mobile polyethylene insert and the tibial endplate . MATERIAL AND METHOD In a series of 51 primary TKA , the three-dimensional ( 3D ) kinematics of the femoral , tibial , and mobile insert components were determined using a computerized matching system between the prosthetic 3D models and the radiographic images of the implants on three lateral follow-up weightbearing knee X-rays : films were taken in full extension , at 45 degrees flexion , and at maximum flexion . RESULTS There was a statistically significant increase in the internal rotation of the mobile tray with flexion , ( up to a mean -3+/-3 degrees between the femoral box and the mobile tray [ p<0.0001 ] and up to a mean -5+/-7 degrees between the tibial tray and the mobile tray [ p<0.0001 ] ) . The mobile tray did not translate in relation to the tibial endplate from extension to 45 degrees flexion ( 0+/-2 mm [ range : -5 to 6 mm ] ) . However , from 45 degrees to maximum flexion , a statistically significant mean 1+/-2 mm ( range : -2 to 9 mm ) of anterior translation ( p<0.0001 ) was found . DISCUSSION The extent of insert mobility varies from one study to another . Some have reported relatively limited mobility stemming from a superior surface that is not highly congruent , ( thus allowing anterior-posterior and mediolateral translation through gliding of the femur in contact with the insert ) . Other studies have reported mobile-bearing tray mobility in relation to the tibial endplate and minimal rotation at the femoral component level . In this series of PCL retaining TKA with a mobile-bearing platform , the mobile-bearing platform showed a progressive increase in internal rotation during flexion . Most of this rotational mobility occurred between the mobile platform and the tibial endplate , confirming our hypothesis . However , with flexion , the femoral component increased its mobility relatively to the platform . During flexion , an anterior-posterior translation occurred between the femoral implant and the tibial insert , and between the tibial insert and the tibial endplate , but the direction of the mobile tibial insert translation remained unpredictable with this nonconstrained implant design used . LEVEL OF EVIDENCE Level IV . Prospect i ve non-controlled therapeutic study 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 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 BACKGROUND Proponents of mobile-bearing total knee arthroplasty believe that it has potential advantages over a fixed-bearing design in terms of diminished wear and improved motion and /or function , but these advantages have not been demonstrated in a r and omized clinical comparison to our knowledge . We conducted a patient-blinded , prospect i ve , r and omized clinical trial to compare mobile-bearing and fixed-bearing cruciate-substituting total knee arthroplasties of the same design . METHODS Patients between the ages of sixty and eighty-five years were prospect ively r and omized to receive a cruciate-substituting rotating-platform design or a fixed-bearing design with an all-polyethylene tibial component . There were no significant differences in the demographic characteristics ( mean age , 72.2 years ; mean American Society of Anesthesiologists score , 2.7 ; mean body mass index , 31.8 kg/m(2 ) ) or preoperative clinical or radiographic measures between the groups . Routine clinical and radiographic follow-up measures included the Knee Society score ( KSS ) , Western Ontario and McMaster Universities Osteoarthritis Index ( WOMAC ) , and Short Form-36 ( SF-36 ) outcome measures . RESULTS The results of 312 arthroplasties ( 136 with an all-polyethylene tibial component  and 176 rotating-platform design s ) in 273 patients were analyzed at a minimum of two years ( mean , forty-two months ) postoperatively . Although there was significant improvement in both groups , there was no significant difference between the groups with regard to the mean postoperative range of motion ( 110.9 degrees and 109.1 degrees , respectively ; p = 0.21 ) , the mean KSS clinical score ( 90.4 and 88.2 points ; p = 0.168 ) , or the mean KSS pain score ( 44.9 and 43.1 points ; p = 0.108 ) at this follow-up point . There were ten revisions : seven because of infection , one because of patellar fracture , one because of instability , and one because of aseptic loosening . CONCLUSIONS The two design s functioned equivalently at the time of early follow-up in this low-to-moderate-dem and patient group . The rotating-platform design had no significant clinical advantage over the design with the all-polyethylene tibial component 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 Fifty-three consecutive patients ( 57 knees ; mean age , 69 years ) entered a prospect i ve r and omized study to compare the fixation of hydroxyapatite (HA)-coated ( 29 knees ) with cemented ( 28 knees ) tibial components in the Tricon II total knee arthroplasty . The quality of the fixation during 5 years postoperatively was evaluated with radiostereometric analysis ( RSA ) . Three HA-coated implants were revised : 2 owing to infection , and 1 owing to early delamination of the coating and clinical loosening . Eight patients ( 9 knees ) died , 1 patient sustained a stroke  , and 1 patient refused investigations after 1 year . In the 40 patients ( 19 HA-coated , 21 cemented ) remaining at 5 years , the magnitude of the micromotion between the HA-coated and cemented groups did not differ . The HA-coated implants displayed most of the migration within the initial 3 months then stabilized , whereas the cemented implants showed an initially lower , but over time continuously increasing migration . Between 1 and 2 years , 4 of 24 HA-coated and 10 of 23 cemented implants  migrated > 0.2 mm and were categorized unstable , which has been shown to have a prognostic value as regards future aseptic loosening . Progressive radiolucent lines developed in 2 cemented knees , which both were categorized unstable . If HA-coated implants can sustain the forces that threaten the fixation in the early period after implantation , a strong and enduring fixation may be obtained The most common reasons for revision of unicompartmental knee arthroplasty ( UKA ) are loosening and pain . Cementless components may reduce the revision rate . The aim of this study was to compare the fixation and clinical outcome of cementless and cemented Oxford UKAs .  A total of 43 patients were r and omised to receive either a cemented or a cementless Oxford UKA and were followed for two years with radiostereometric analysis ( RSA ) , radiographs aligned with the bone-implant interfaces and clinical scores . The femoral components migrated significantly during the first year ( mean 0.2 mm ) but not during the second . There was no significant difference in the extent of migration between cemented and cementless femoral components in either the first or the second year . In the first year the cementless tibial components  subsided significantly more than the cemented components ( mean 0.28 mm ( sd 0.17 ) vs. 0.09 mm ( sd 0.19 mm ) ) . In the second year , although there was a small amount of subsidence ( mean 0.05 mm ) there was no significant difference ( p = 0.92 ) between cemented and cementless tibial components . There were no femoral radiolucencies . Tibial radiolucencies were narrow ( < 1 mm ) and were significantly ( p = 0.02 ) less common with cementless ( 6 of 21 ) than cemented ( 13 of 21 ) components at two years . There were no complete radiolucencies with cementless components , whereas five of 21 ( 24 % ) cemented components had complete radiolucencies . The clinical scores at two years were not significantly different ( p = 0.20 ) . As second-year migration is predictive of subsequent loosening , and as radiolucency is suggestive of reduced implant-bone contact , these data suggest that fixation of the cementless components is at least as good as , if not better than , that of cemented devices A prospect i ve , r and omized , double-blind study was performed to evaluate three different means of fixing tibial components  during total knee arthroplasty . Eleven components fixed with cement , ten hydroxyapatite-coated components fixed without cement  , and ten noncoated components fixed without cement were studied . A posterior cruciate ligament-retaining total condylar implant was used . Micromotion of the components was assessed with roentgen stereophotogrammetric analysis during the two-year follow-up period . There were no significant differences among the patients with regard to age ( mean [ and st and ard deviation ] , 68 ± 11.6 years ) , body-mass index ( mean , 23 ± 2.8 kilograms per square meter ) , or stage of osteoarthrosis ( mean , 4 ± 2.4 according to the classification system of Ahlbäck and 5 ± 0.6 according to that of Larsen et al. ) . The diagnosis was osteoarthrosis in five knees , and it was rheumatoid arthritis in twenty-six .  The clinical scores were similar among the study groups . According to the system of the Knee Society , the mean preoperative functional score was 10 ± 2.9 points and the mean preoperative knee score was 24 ± 3.2 points . At the two-year follow-up evaluation , these scores were 41 ± 8.3 and 79 ± 3.2 points , respectively . A significant difference with regard to micromotion was found between the noncoated components fixed without cement and the hydroxyapatite-coated components fixed without cement as well as between the noncoated components fixed without cement and the components fixed with cement ( p < 0.001 , analysis of variance ) . The hydroxyapatite-coated components fixed without cement and the components fixed with cement both had far less micromotion along the longitudinal axis ( subsidence ) throughout the follow-up period than did the noncoated components fixed without cement . At the two-year follow-up evaluation , the subsidence of the noncoated components was -0.73 ± 0.924 millimeter , the subsidence of the cemented components was -0.05 ± 0.109 millimeter , and the subsidence of the hydroxyapatite-coated components was -0.06 ± 0.169 millimeter . The cemented components as well as the hydroxyapatite-coated components also had less translation along the transverse axis ( p < 0.001 , analysis of variance ) and the sagittal axis ( p < 0.001 , analysis of variance ) compared with the noncoated components . In conclusion , micromotion of hydroxyapatite-coated tibial components fixed without cement was similar to that of tibial components fixed with cement . Therefore , hydroxyapatite , a biological mediator , may be necessary for the adequate fixation of tibial components when cement is not used
Finally , with use of a variety of vali date d measures , there was no difference between the two groups in terms of functional status at two , eight , and ten years , regardless of the measure used .
A less expensive all-polyethylene component as part of a total knee arthroplasty has results equivalent to those obtained with a cemented metal-backed tibial component .
BACKGROUND The cost of the implant as part of a total knee arthroplasty accounts for a substantial portion of the costs for the overall procedure : all-polyethylene tibial components cost considerably less than cemented metal-backed tibial components .
We performed a systematic review of the literature to determine whether the clinical results of lower-cost all-polyethylene tibial components were comparable with the results of a more expensive metal-backed tibial component .