A prospective randomised study comparing rotating platform and fixed bearing total knee arthroplasty in a cruciate substituting design--outcomes at two year follow-up. Differences in long-term fixation between mobile-bearing and fixed-bearing knee prostheses at ten to 12 years' follow-up: a single-blinded randomised controlled radiostereometric trial. Mobile vs. fixed bearing unicondylar knee arthroplasty: A randomized study on short term clinical outcomes and knee kinematics. A comparison of fixed-bearing and mobile-bearing total knee arthroplasty at a minimum follow-up of 4.5 years. Fixed-bearing versus mobile-bearing total knee arthroplasty: a prospective randomised, clinical and radiological study with mid-term results at 7 years. [Fixed-bearing versus mobile-bearing total knee arthroplasty: a prospective randomized clinical and radiological study]. [Knee arthroplasty. Mobile- and fixed-bearing design]. Gait analysis of fixed bearing and mobile bearing total knee prostheses during walking: do mobile bearings offer functional advantages? Fixed versus mobile weight-bearing prosthesis in total knee arthroplasty Functional performance of mobile versus fixed bearing total knee prostheses: a randomised controlled trial Comparison of mobile-bearing and fixed-bearing total knee arthroplasty: a prospective randomized study. The John Insall Award: No Functional Advantage of a Mobile Bearing Posterior Stabilized TKA Staged bilateral mobile-bearing and fixed-bearing total knee arthroplasty in the same patients: a prospective comparison of a posterior-stabilized prosthesis Mobile- versus fixed-bearing total knee arthroplasty: a prospective randomized controlled trial featuring 6-10-year follow-up. Long-term comparison of mobile-bearing vs fixed-bearing total knee arthroplasty. Kinematics and early migration in single-radius mobile- and fixed-bearing total knee prostheses. Comparison of mobile- and fixed-bearing cemented total knee arthroplasty.
BACKGROUND Fixed bearing ( FB ) total knee replacement is a well established technique against which new techniques must be compared . Mobile bearing ( MB ) prostheses , in theory , reduce polyethylene wear but the literature is yet to provide evidence that they are superior in terms of function or long-term survivorship . In addition there has been no comparison of patella resurfacing on the outcome of either design . The aims of this r and omised prospect i ve study were firstly to determine whether a mobile bearing prosthesis produced better clinical outcome and range of motion at two year follow-up and secondly to assess the effect of patella resurfacing on the outcomes of both types of bearing design . METHODS Three hundred fifty-two patients were r and omised into receiving either a PFC Sigma © cruciate sacrificing total knee arthroplasty either with a mobile bearing or a fixed bearing  , with a sub-r and omisation to either patella resurfacing or patella retention . All patients participated with st and ard clinical outcome measures and had their range of motion measured both pre-operatively and at follow-up . RESULTS The mobile bearing TKR design had no impact on range of motion ; Oxford Knee Score and American Knee Society knee and function scores when compared to its fixed bearing equivalent . CONCLUSIONS At two year follow-up there was no difference between the PFC Sigma © fixed and mobile bearing design s. With no clinical difference between the cohorts , we can not recommend one design over the other . Long term benefits , particularly with regards to polyethylene wear , may yet be demonstrated . Level of evidence --1B This single-blinded r and omised controlled trial investigated whether one design of mobile-bearing ( MB ) total knee replacement ( TKR ) has any advantage over a fixed-bearing ( FB ) design on long-term fixation as measured by radiostereometry . The amount of wear underneath the mobile bearing was also evaluated . A series of 42 knees was r and omised to MB or FB tibial components with appropriate polyethylene inserts and followed for between ten and 12 years , or until the death of the patient . The polyethylene in the MB group was superior in that it was gamma-irradiated in inert gas and was calcium-stearate free ; the polyethylene in the FB group was gamma-irradiated in air and contained calcium stearate . In theory this should be advantageous to the wear rate of the MB group . At final follow-up the overall mean migration was 0.75 mm ( SD 0.76 ) in the MB group and 0.66 mm ( SD 0.4 ) in the FB group , with the FB group demonstrating more posterior tilt and the MB group more internal rotation . In the FB group there was one revision for aseptic loosening , but none in the MB group . There were no significant differences in clinical or radiological scores . For the MB group , the mean linear wear rate on the under-surface was 0.026 mm/year ( SD 0.014 ) . This was significantly smaller than the wear rate of 0.11 mm/year ( SD 0.06 ) in the MB between femur and polyethylene ( p < 0.001 ) . Nevertheless , even in a best-case setting the mobile bearings of this TKR design had no apparent advantage in terms of fixation over the FB knee prosthesis at ten to 12 years . The wear underneath the mobile bearing was small and is unlikely to be clinical ly relevant The literature contains limited yet controversial information regarding whether a fixed or a mobile bearing implant should be used in unicompartmental knee arthroplasty ( UKA ) . This r and omized study was to further document the performance and comparison of the two design s. Fifty-six knees in 48 patients ( mean age of 72 years ) undergoing medial UKA were r and omized into a fixed bearing ( Miller/Galante ) or a mobile bearing ( Oxford ) UKA . The 2 year clinical outcomes ( clinical scores ) , radiographic findings , and weight bearing knee kinematics ( assessed using RSA ) were compared between the two groups . The mobile bearing knees displayed a larger and an incrementally increased tibial internal rotation ( 4.3 degrees , 7.6 degrees , 9.5 degrees vs. 3.0 degrees , 3.0 degrees , 4.2 degrees respectively at 30 degrees , 60 degrees , 90 degrees of knee flexion ) compared to the fixed ones . The medial femoral condyle in the mobile bearing knees remained 2 mm from the initial position vs. a 4.2 mm anterior translation in the fixed bearing knees during knee flexion . The contact point in the mobile bearing implant moved 2 mm posteriorly vs. a 6 mm anterior movement in the other group . The mobile bearing knees had a lower incidence of radiolucency at the bone implant interface ( 8 % vs. 37 % , p < 0.05 ) . The incidence of lateral compartment OA and progression of OA at patello-femoral joint were equal . No differences were found regarding Knee Society Scores , WOMAC , and SF-36 scores ( p > 0.05 ) . This study indicates that mobile bearing knees had a better kinematics , a lower incidence of radiolucency but not yet a better knee function at 2 years BACKGROUND Durable long-term independent results with the Low Contact Stress rotating-platform ( mobile-bearing ) and the Insall Burstein-II ( fixed-bearing ) total knee prostheses have been reported , but no studies describing either the mid-term or long-term results and comparing the two prostheses are available , to our knowledge . METHODS Thirty-two patients who had bilateral arthritis of the knee with similar deformity and preoperative range of motion on both sides and who agreed to have one knee replaced with a mobile-bearing total knee design and the other with a fixed-bearing design were prospect ively evaluated . Comparative analysis of both design s was done at a mean follow-up period of six years , minimizing patient , surgeon , and observer-related bias . Clinical and radiographic outcome , survival , and complication rates were compared . RESULTS Patients with osteoarthritis had better function scores and range of motion compared with patients with rheumatoid arthritis . However , with the numbers available , no benefit of mobile-bearing over fixed-bearing design s could be demonstrated with respect to Knee Society scores , range of flexion , subject preference , or patellofemoral complication rates . Radiographs showed no difference in prosthetic alignment . Two knees with a mobile-bearing prosthesis required a reoperation : one had an early revision because of bearing dislocation and another required conversion to an arthrodesis to treat a deep infection . CONCLUSIONS We found no advantage of the mobile-bearing arthroplasty over the fixed-bearing arthroplasty with regard to the clinical results at mid-term follow-up . The risk of bearing subluxation and dislocation in knees with the mobile-bearing prosthesis is a cause for concern and may necessitate early revision . LEVEL OF EVIDENCE Therapeutic Level II Mobile-bearing ( MB ) total knee arthroplasty ( TKA ) was developed as an alternative to the established fixed-bearing ( FB ) design because of theoretical advantages . Short-term studies comparing these design s have not shown any differences in clinical and radiographic results . We compared the results at 7 years of a r and omised study of patients undergoing TKA using either a FB or a MB variant of the same prosthesis . Fifty-two patients ( 52 knees ) with an average age of 70 years received a FB posterior-stabilized prosthesis , and 50 patients ( 52 knees ) with an average age of 72 years , a MB prosthesis .  All implants were cemented and the patella was routinely resurfaced . Preoperatively , there were no differences between the two groups , and surgical procedure and postoperative protocol were the same for both . At an average follow-up of 7.1 years , no significant differences of FB over MB design could be demonstrated with respect to the American Knee Society score ( AKSS ) , pain score , a question naire of general health ( SF-12 score ) , range of motion ( ROM ) , or complication rates . Radiographs showed no significant difference in prosthetic alignment or evidence of loosening . Two knees with a MB design required reoperation , one for persistent joint stiffness and another to treat septic loosening . One patient with a MB prosthesis with signs of tibial component loosening was asymptomatic . We conclude that at mid-term follow-up there is no evidence to prove the superiority of MB over FB TKA with regard to the clinical and radiographic results PURPOSE OF THE STUDY Mobile-bearing total knee arthroplasty has become increasingly popular over the last few years since this option presents several theoretical advantages compared with the fixed-bearing models . The clinical advantage remains to be demonstrated . We therefore conducted a prospect i ve r and omized trial to ascertain the potential benefits . MATERIAL AND METHODS This study included patients treated by three senior orthopedic surgeons . Each group included 52 prostheses in 52 patients in the fixed-bearing group and 50 patients in the mobile-bearing group . The per- and postoperative protocol s were the same for both groups . Implants were cemented in all cases and patellae were resurfaced . The SF-12 , the Knee Society Score ( KSS ) , the Hospital of Special Surgery score ( HSS ) and pain and joint motion were noted before and after surgery . RESULTS Among the 104 prostheses implanted , 100 were review ed at mean follow-up of 36 months ( range 24 - 41 ) . One patient in the fixed-bearing group died six months after surgery from an unrelated cause . Three patients were lost to follow-up : one in the fixed-bearing group and two in the mobile-bearing group . There was no difference between groups for the SF-12 , KSS , HSS , pain and joint motion measured postoperatively . Postoperative femorotibial alignment was one degree varus on average in the fixed-bearing group and zero degree in the mobile-bearing group . At last follow-up , there were no radiological signs of prosthesis loosening . One patient in the fixed-bearing group developed a deep venous thrombosis , complicated by pulmonary embolism . Two of the mobile-bearing prostheses were revised , one for patellar fracture caused by a bicycle accident and one for prosthesis infection in a patient with endocarditis 1.5 years after implantation . DISCUSSION The clinical results were similar for the two groups in terms of function , pain , general status and complications . The outcome at 36 months was considered excellent or good in 90 % of the fixed-bearing group and 88 % in the mobile-bearing group . This study did not reveal any difference between the two groups regarding maximal flexion and anterior knee pain , two parameters which would theoretically show short-term improvement with the mobile bearing . Mid- and long-term follow will be required to confirm these findings and to determine the survival of these two types of implants After the introduction of  mobile-bearing knee arthroplasty  in the late 1970s , he benefits were discussed in comparison to the well-established modular fixed-bearing systems . The hypothetical advantages of mobile-bearing design s are the ability of axial rotation and a greater articular conformity , which reduces significantly fatigue failure of the polyethylene . Biomechanical analyses showed for each system characteristic features , which are not concordant with the aim of restoring normal knee kinematics . In both groups the long-term clinical results were excellent with 10-year survival rates of 95 - 98 % . Ligamentous stability and a perfect operative technique are key factors in mobile-bearing knee arthroplasty . Prospect i ve r and omized clinical trials are necessary to find answers concerning backside and volumetric polyethylene wear and the detrimental effects of wear particle size . Before this is accomplished , the indication for a  mobile-bearing knee arthroplasty  , especially in young patients , should be carefully considered in each case BACKGROUND Limited previous findings have detailed biomechanical advantages following implantation with mobile bearing ( MB ) prostheses after total knee replacement ( TKR ) surgery during walking . The aim of this study was to compare three dimensional spatiotemporal , kinematic , and kinetic parameters during walking to examine whether MBs offer functional advantages over fixed bearing ( FB ) design s. METHODS Sixteen patients undergoing primary unilateral TKR surgery were r and omised to receive either a FB ( n=8 ) or MB ( n=8 ) total knee prosthesis .  Eight age and gender matched controls underwent the same protocol on one occasion . A 12 camera Vicon system integrated with four force plates was used . Patients were tested pre-surgery and nine months post-surgery . RESULTS No significant differences between FB and MB groups were found at any time point in the spatiotemporal parameters . The MB group was found to have a significantly reduced frontal plane knee range of motion ( ROM ) at pre-surgery than the FB group ( FB=14.92±4.02 ° ; MB=8.87±4.82 ° ) , with the difference not observed post-surgery . No further significant kinematic or kinetic differences were observed between FB and MB groups . Fixed bearing and MB groups both displayed spatiotemporal , kinematic , and kinetic differences when compared to controls . Fixed bearing and MB groups differed from controls in six and five parameters at nine months post-surgery , respectively . CONCLUSIONS No functional advantages were found in knees implanted with MB prostheses during walking , with both groups indicative of similar differences when compared to normal knee biomechanics following prosthesis implantation . LEVEL OF EVIDENCE Level II Purpose This study was design ed to compare clinical , radiological , and general health results of two prostheses ( mobile vs. fixed weight-bearing devices ) that are used in total knee arthroplasty with a 5-year follow-up . Methods This r and omized controlled study was conducted from 2004 to 2010 in the Department of Orthopedic Surgery at two university hospitals in Isfahan , Iran . Three hundred patients with expected primary total knee arthroplasty ( TKA ) without severe deformity ( a fixed varus or valgus deformity greater than 20 ° ) received fixed weight-bearing ( n = 150 ) or mobile weight-bearing ( n = 150 ) devices . Clinical , radiological , and quality of life outcomes were compared between the two groups at six-month intervals for the first year , after which the comparisons were made annually for the next 4 years . Results Both groups had similar baseline characteristics . Although there was significant improvement in both groups , there was no significant difference between the groups with regard to the means of the Knee Society Scores , which were 92 ( SD : 12.1 ) for the fixed weight-bearing device and 93 ( SD : 14.2 ) for the mobile weight-bearing device ( n.s . ) at the final follow-up point . Radiographs showed that there was no significant difference in prosthetic alignment and no evidence of loosening . After TKA , the SF-36 score increased in both groups , but there was no statistical difference between the groups in quality of life at the final follow-up ( 62 ( 12.2 ) vs. 64 ( 14.3 ) , n.s . ) . There was no revision after 5 years . Conclusions In terms of clinical , radiological or general health outcomes for people who underwent TKA , the results of this study showed no clear advantage of mobile weight-bearing over the fixed weight-bearing prosthesis at the five-year follow-up . Level of evidence Purpose The primary goal of this study was to assess the difference in active flexion between patients with a mobile versus a fixed bearing , cruciate retaining , and total knee arthroplasty .  The study was design ed as a r and omised controlled multi-centre trial . Methods Participants were assigned to interventions by using block-stratified , r and om allocation . Outcome parameters were active flexion , passive flexion , and Knee Society Score ( KSS ) . Outcome parameters were assessed preoperatively and at 3 , 6 , and 12 months postoperatively by an independent nurse . Results Ninety-two patients from one centre were included , 46 in each group . Active flexion was comparable for the two groups , 99.9 ° for the mobile bearing group and 101 ° for the fixed bearing group with a baseline controlled difference of 1.0 ( 95 % CI −3.9 to 5.8 , n.s . ) . The Clinical KSS was comparable between the two bearing groups ( Mobile 90.0 vs. fixed 92.4 , n.s . ) . The functional KSS showed a difference that was attributable to the stair climbing subscore , which showed a difference in favour of the fixed bearing design between preoperative and 3 months ( 7.3 point difference ; 95 % CI 2.3–12.5 ; P = 0.005 ) as well as 12 months ( 4.8 point difference ; 95 % CI 0.1–9.6 ; P = 0.045 ) . Conclusions There were no short-term differences in active flexion  between fixed bearing and mobile bearing total knee arthroplasty . Level of evidence The purpose of this prospect i ve r and omized study was to compare the postoperative recovery and early results of 2 groups of patients undergoing total knee arthroplasty : 107 patients received an established fixed-bearing posterior-stabilized prosthesis ( Legacy Posterior Stabilized [ LPS ] ) , and 103 patients the meniscal-bearing prosthesis ( Meniscal Bearing Knee [ MBK ] ) .  Surgical procedures were the same for both groups except for posterior cruciate ligament management , which was sacrificed in the LPS group and spared but completely released from the tibia in the MBK group . At an average follow-up of 36 months , knee , function , and patellar scores were comparable in both groups . The LPS group showed a significantly higher maximum flexion than the MBK group ( 112 degrees vs 108 degrees ) . Using a fixed-bearing or a mobile-bearing design did not seem to influence the short-term recovery and early results after knee arthroplasty . Key words : total knee arthroplasty , mobile bearing , knee prosthesis , meniscal-bearing knee , posterior stabilized , prospect i ve r and omized Background Mobile bearing ( MB ) total knee design has been advocated as a means to enhance the functional characteristics and decrease the wear rates of condylar total knee arthroplasty ( TKA ) . However , it is unclear if these design s achieve these goals . Questions / purpose sWe asked whether function of patients or survivorship would be greater or complications would be lesser in groups of patients with MB compared with fixed bearing ( FB ) TKA .  We also sought to describe retrieval findings . Methods We r and omized 507 primary TKAs in 416 eligible patients to receive MB ( n = 252 ) or FB ( n = 255 ) devices from November 2001 to August 2007 ( Investigational Device Exemption G000180 , Clinical Trials.gov registration number NCT00946075 ) . Patients were blinded to treatment allocation . WOMAC Index , SF-12 Health Survey , knee range of motion , and Knee Society scores were collected and compared preoperatively and at 6 , 12 , and 24 months postoperatively . We recorded device failures and complications until October 2009 . Kaplan-Meier survivorship was compared using the log rank test . Twelve retrieved MB devices underwent pathologic analysis . The minimum postoperative time was 2.2 years ( mean , 5.9 years ; range , 2.2–7.9 years ) . Results We found no differences in mean clinical assessment scores or mean score changes from baseline at any postoperative interval through 2 postoperative years . Nineteen of the 252 MB and 13 of the 255 FB knees had undergone revision of any component . Estimated survival at 6 postoperative years was similar for the two devices : 90.1 % ( 95 % confidence interval [ CI ] , 84.1–93.9 ) for MB and 94.2 % ( 95 % CI , 90.1–96.6 ) for FB . Two MB and no FB tibial components were revised for loosening . There was one case of MB insert dislocation . Retrieved MB devices demonstrated no unexpected wear or mechanical device failures . Conclusion We found no evidence of functional advantage of the MB design . Survivorship was similar , although the study is limited by short duration of followup . Level of Evidence Level I , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence Mobile-bearing total knee arthroplasty ( TKA ) has several theoretical advantages over fixed-bearing TKA . We conducted a prospect i ve r and omized trial to compare the results of mobile-bearing and fixed-bearing posterior-stabilized TKA in the same patients using the same femoral component design of a mobile-bearing prosthesis in one knee and a fixed-bearing prosthesis in the other knee in 25 patients with osteoarthritis . The mean follow-up was 40 months . No significant differences were found in the mobile-bearing and fixed-bearing knees in terms of clinical and radiographic results . No osteolysis , loosening , or revision occurred . One knee with a mobile-bearing prosthesis had a dislocation of the rotating bearing ; however , spontaneous reduction occurred and the dislocation did not recur . Satisfactory early results can be achieved in both mobile-bearing and fixed-bearing knees . We could not demonstrate an advantage of a mobile-bearing 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 Few published reports have been published regarding a comparison of the long-term outcomes between mobile- ( MB ) and fixed-bearing component design s for knee arthroplasty . The minimum 10-year clinical and radiologic follow-up of an unselected consecutive series of 89 patients ( 107 knees ) who were r and omized to have one of these different design s for primary arthroplasty was done . Twenty-six patients ( 30 knees ) who had a fixed-bearing design and 24 patients ( 33 knees ) who had an MB prosthesis were available for follow-up . Two MB knees were revised for aseptic loosening of a tibial component in one and femoral component fracture in the other . In patients who did not have revision surgery , there were no differences between the groups with respect to mean Knee Society scores , knee flexion , or pain scores BACKGROUND The mobile-bearing variant of a single-radius design is assumed to provide more freedom of motion compared to the fixed-bearing variant because the insert does not restrict the natural movements of the femoral component . This would reduce the contact stresses and wear which in turn may have a positive effect on the fixation of the prosthesis to the bone and thereby decreases the risk for loosening . The aim of this study was to evaluate early migration of the tibial component and kinematics of a mobile-bearing and fixed-bearing total knee prosthesis of the same single-radius design . METHODS Twenty Triathlon single-radius posterior-stabilized knee prostheses were implanted ( 9 mobile-bearing and 11 fixed-bearing ) .  Fluoroscopy and roentgen stereophotogrammetric analysis ( RSA ) were performed 6 and 12 months post-operatively . FINDINGS The 1 year post-operative RSA results showed considerable early migrations in 3 out of 9 mobile-bearing patients and 1 out of 11 fixed-bearing patients . The range of knee flexion was the same for the mobile-bearing and fixed-bearing group . The mobile insert was following the femoral component during motion . INTERPRETATION Despite the mobile insert following the femoral component during motion , and therefore performing as intended , no kinematic advantages of the mobile-bearing total knee prosthesis were seen . The fixed-bearing knee performed as good as the mobile-bearing knee and maybe even slightly better based on less irregular kinematics and less early migrations Concern about polyethylene wear and related osteolysis after knee arthroplasty has developed in the last years . Mobile-bearing knee prostheses were design ed in order to reduce the influence of this critical factor on long-term success of total knee replacement . We present a prospect i ve study comparing clinical and radiological results with a mobile-bearing ( Ceragyr ) and a fixed-bearing knee prosthesis ( posterior stabilized Hermes ) . Clinical results did not show any significant differences in Knee Society scores . We found better results in the mobile-bearing group for pain scores and subjective preference , but the difference did not reach statistical significance . Within the time limits of this study , radiological analysis showed no osteolysis in either group , but longer follow-up will be needed to confirm this
After stratification on follow-up time and age , the revision rates were not substantially different , aside for younger patients in short term from studies with short-term follow-up .
Conclusion No essential differences between the two design s were observed .
MB and FB UKA design s have comparable revision rates .
Purpose Two design concepts are currently used for unicondylar knee arthroplasty ( UKA ) prostheses :  fixed bearing ( FB ) and mobile bearing ( MB ) .
While MB prostheses have theoretical advantages over their FB counterparts , it is not clear whether they are associated with better outcomes .