Comparison between mobile-bearing and fixed-bearing knees in bilateral total knee replacements

Comparison of revision rates and epidemiological data of a single total knee arthroplasty system of different designs (cruciate retaining, posterior stabilized, mobile bearing, and fixed bearing): a meta-analysis and systematic review of clinical trials and national arthroplasty registries

BACKGROUND

This study aimed to meta-analyze epidemiological data, revision rates, and incidences of different designs of a single Total Knee Arthroplasty System and compare these factors across different countries.

METHODS

A systematic review was conducted on clinical studies and arthroplasty registries of ATTUNE TKA from 1999 to 2020. The main endpoints analyzed were revision rates and epidemiological data.

RESULTS

The average age of patients was 67.8 years, with a gender distribution of 60% female and 40% male. The pooled average BMI was 29.4 kg/m2. Eight clinical studies showed a pooled revision rate per 100 observed CY of 0.5 (n = 1343 cases). Cumulative revision rates after 1, 3, and 5 years varied among registries, with the Swiss registry having the highest revision data (after 5 years: 6.3%) and the American registry having the lowest revision data (after 5 years: 1.7%). A comparison of the revision rates of mobile bearing and fixed bearing (41,200 cases) as well as cruciate retaining and posterior stabilized (n = 123,361 cases) showed no significant advantage in the first 5 years after implantation.

CONCLUSION

In conclusion, pooled data from 41,200 cases of TKA with a single Total Knee Arthroplasty System in two arthroplasty registries revealed that there was no significant difference in revision rates between the mobile bearing and fixed bearing design within the first 5 years after implantation. In addition, a comparison of the revision rates in n = 123,361 cases showed no significant advantage for cruciate retaining or posterior stabilized in the first 5 years after implantation.

Ten-year follow-up of a total knee prosthesis combining multi-radius, ultra-congruency, posterior-stabilization and mobile-bearing insert shows long-lasting clinically relevant improvements in pain, stiffness, function and stability

PURPOSE

There is a paucity of data available on total knee prostheses combining dual-radius, ultra-congruency, posterior-stabilization and mobile-bearing insert. This prospective cohort study aimed to assess the clinical evolution of the FIRST^® prosthesis (Symbios Orthopédie, Yverdon, CH), the earliest prosthesis with this particular design. It was hypothesized that the primary outcomes, evaluating pain, stiffness, function and stability, would improve following arthroplasty and remain improved during the follow-up period of 10 years.

METHODS

All patients programmed for a total knee arthroplasty using a FIRST^® prosthesis at our university hospital between 2006 and 2008 were invited to participate. Study knees were evaluated pre-operatively as well as one, five and ten years post-operatively. Patients filled out questionnaires at each evaluation point and had a radiographic assessment at the five-year and ten-year follow-ups. Primary outcomes were the total, pain, stiffness and function measures of the Western Ontario and McMaster Universities Osteoarthritis questionnaire (WOMAC) and the knee and function measures of the Knee Society Score (KSS). Friedman and Wilcoxon's rank-sum tests were used to compare measures across time points.

RESULTS

Hundred and twenty four prostheses were included (baseline demographics: 69.9 ± 8.3 years old, 28.1 ± 4.3 kg/m², 54% male) and 68 could be followed during ten years. Five prostheses underwent a revision. All other prostheses lost at follow-up were lost for reasons unrelated to the prosthesis. All primary measures reported statistically and clinically significant improvements between baseline and the three follow-up evaluations. Statistically significant improvements at the three follow-up evaluations were also observed for most secondary measures. There was no implant loosening. At ten-year follow-up, radiolucent lines were observed in 2.9% femoral implants and 1.5% tibial implants.

CONCLUSION

The positive results observed in all domains of assessment and the small revision rate demonstrated an effective functioning of the FIRST^® prosthesis during the ten-year follow-up period. The results, globally similar to those previously published for other prosthesis designs, encourage the development of assistive methods to select the most appropriate designs on an individual basis.

LEVEL OF EVIDENCE

IV, prospective cohort study.

No difference between mobile and fixed bearing in primary total knee arthroplasty: a meta-analysis

PURPOSE

Both mobile (MB) and fixed (FB) bearing implants are routinely used for total knee arthroplasty (TKA). This meta-analysis compared MB versus FB for TKA in terms of implant positioning, joint function, patient reported outcome measures (PROMs), and complications. It was hypothesised that MB performs better than FB implants in primary TKA.

METHODS

This meta-analysis was conducted according to the 2020 PRISMA statement. In February 2022, the following databases were accessed: Pubmed, Web of Science, Google Scholar, Embase. All the randomized clinical trials (RCTs) comparing mobile versus fixed bearing for primary TKA were considered.

RESULTS

Data from 74 RCTs (11,116 procedures) were retrieved. The mean follow-up was 58.8 (7.5 to 315.6) months. The MB group demonstrated greater range of motion (ROM) (P = 0.02), Knee Society Score (KSS) score (P < 0.0001), and rate of deep infections (P = 0.02). No difference was found in implant positioning: tibial slope, delta angle, alpha femoral component angle, gamma femoral component angle, beta tibial component angle, tibiofemoral alignment angle, posterior condylar offset, radiolucent lines. No difference was found in duration of the surgical procedure. No difference was found in the following PROMs: Oxford Knee Score (OKS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), visual analogue scale (VAS), function and pain subscales of the KSS score. No difference was found in the rate of anterior knee pain, revision, aseptic loosening, fractures, and deep vein thrombosis.

CONCLUSION

There is no evidence in support that MB implants promote greater outcomes compared to FB implants in primary TKA.

LEVEL OF EVIDENCE

Level I.

Superior Mid- to Long-Term Clinical Outcomes of Mobile-Bearing Total Knee Arthroplasty Compared to Fixed-Bearing: A Meta-Analysis Based on a Minimum of 5 Years of Study

As more patients undergo total knee arthroplasty (TKA) each year, and the average age of patients gets younger, the patients are generally more active requiring a greater physiological demand and increasing range of motion on the prosthesis than the previous patients. However, there is no consensus on the optimal TKA tibial bearing design. We performed this systematic review to compare the clinical differences between mobile and fixed bearing constructs used in contemporary TKA. We searched PubMed, EMBASE, and Cochrane Library databases, identifying 515 total publications, including 17 randomized controlled trials (RCTs). A meta-analysis was performed, while the quality and bias of the evidence were rated according to the Grading of Recommendations Assessment Development and Evaluation (GRADE) guidelines and the Cochrane Database questionnaire. The meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Seventeen studies were included, with a total of 1505 knees receiving a mobile bearing TKA and 1550 knees receiving a fixed bearing TKA. The meta-analysis compared clinical outcomes between mobile bearing (MB)-TKA and fixed bearing (FB)-TKA using postoperative Knee Society Score, postoperative ROM, and survivorship and showed that there was a distinct difference in Knee Society Score between the mobile-bearing and fixed-bearing groups (overall standardized mean difference = 1.38; 95% confidence interval (CI): 0.50-2.25; p = 0.002; I² = 60%). Patients treated with mobile-bearing prostheses were more likely to report good or excellent range of motion results (overall standardized mean difference = 2.06; 95% CI: 0.65-3.47; p = 0.004). No difference in implant survivorship or reoperation rate were identified. The fixed-bearing and mobile-bearing TKA designs are both capable of producing excellent long-term results with excellent clinical outcomes if properly implanted; however, the mobile-bearing TKA have superiority in mid- to long-term clinical results. Trial registration number for PROSPERO was CRD42019126402.

Effect of insert material on forces on quadriceps, collateral ligament, and patellar tendon after rotating platform mobile-bearing total knee arthroplasty

BACKGROUND

There is a gradual increase in the number of patients for total knee arthroplasty (TKA), and TKA demonstrates reliable clinical outcomes. The orthopaedic biomaterials community continuously attempted over the past decades to improve the longevity of UHMWPE in TKA by using various improved technologies. Polyetheretherketone (PEEK) and carbon fiber reinforced-PEEK(CFR-PEEK) are suggested as potential tibial insert materials to replace UHMWPE in some applications. The aim of this study involves evaluating the biomechanical effects of UHMWPE and CFR-PEEK tibial materials on mobile-bearing TKA.

METHODS

The finite element (FE) model was obtained by conducting computed tomography and magnetic resonance imaging. The FE investigation included three types of loading conditions corresponding to the loads used in the experiments for FE model validation and model predictions under deep-knee bend loading conditions. We investigated forces on quadriceps, collateral ligament and patellar tendon with UHMWPE and CCFR-PEEK tibial insert materials under the deep-knee-bend condition.

RESULTS

Quadriceps force decreased with flexion for CFR-PEEK when compared to that for UHMWPE. A similar trend was observed in terms of the patellar tendon force. An opposite trend was observed in the collateral ligament. Medial collateral ligament force in the CFR-PEEK exceeded that in the UHMWPE, and lateral collateral ligament force in the UHMWPE exceeded that in the CFR-PEEK.

CONCLUSION

The CFR-PEEK represents an alternative insert material given its superior biomechanical effect after mobile-bearing total knee arthroplasty. However, a balance between the medial and lateral ligaments is considered as an important factor in the CFR-PEEK tibial insert due to its opposite biomechanical effect.

Short-term differences in anterior knee pain and clinical outcomes between rotating and fixed platform posterior stabilized total knee arthroplasty with a new femoral component design

AIM

To compare rotating versus fixed-bearing Press-Fit Condylar (PFC) Sigma posterior stabilized (PS) total knee arthroplasty (TKA) with the new “J curve” femoral design in terms of clinical outcomes and anterior knee pain.

METHODS

We retrospectively analyzed 39 patients who underwent primary total knee replacement surgery for knee osteoarthritis using the PFC Sigma PS TKA with either fixed (FP group, 20 cases) or rotating platform (RP group, 19 cases) treated between 2009 and 2013 by the same surgeon. The two groups were homogeneous for age, gender, weight, American Society of Anesthesiologists status, pre-operative clinical and functional scores, and prosthetic alignment at two years after surgery. We analyzed clinical outcomes score at two years follow-up using Knee Society Score (KSS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Knee Performance Score, Short Form (SF) 36, and anterior knee pain assessed by the Hospital for Special Surgery (HSS) patellar score.

RESULTS

No differences were found in KSS, Knee Performance Score, and SF-36 outcome scores. A statistically significant difference was found in the HSS Patella score objective (FP: 22.36; RP: 28.75; P < 0.05), HSS Patella score total (FP: 73.68; RP: 86.50; P < 0.05), and KOOS symptoms (FP: 73.49; RP: 86.44; P < 0.05).

CONCLUSION

Rotating platform in PFC Sigma PS TKA appears to reduce the short-term incidence of anterior knee pain compared to the fixed platform.

Unsatisfactory clinical outcomes of second-generation mobile bearing floating platform total knee arthroplasty: comparing outcomes with fixed bearing after five years minimum

BACKGROUND

The purpose of this retrospective study was to analyze and compare the clinical and radiologic outcomes of fixed bearing ultracongruent (UC) insert total knee arthroplasty (TKA) and mobile bearing (MB) floating platform TKA using the navigation-assisted gap balancing technique with a minimum follow-up of five years.

METHODS

The study retrospectively enrolled 105 patients who received the UC type fixed bearing insert (group 1) and 95 patients who received the floating platform MB insert (group 2) during the period from August 2009 to June 2012. All surgery was performed using the navigation-assisted gap balancing technique. For strict assessment of gap measurements, the offset-type-force-controlled-spreader-system was used. Radiologic and clinical outcomes were assessed before operation and at the most recent follow-up using the Knee Society Score (KSS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. For statistical analysis, paired sample t tests were used. A p value less than 0.05 was considered significant.

RESULTS

Although the radiologic alignments were satisfactory for both groups (99/105 [94%] cases were neutral for group 1 and 90/95 [94%] for group 2), the functional and total WOMAC scores were inferior in group 2 (p < 0.05). There were two cases of insert breakage in group 2 that required bearing exchange. The Kaplan-Meier survivorship rates for groups 1 and 2 at 77 months were 100.0 and 97.9%, respectively.

CONCLUSION

Second-generation MB floating platform TKA cases did not have satisfactory outcomes. There were two cases of insert breakage, which required bearing exchange. Other patients who underwent surgery with second-generation MB floating platform were encouraged to avoid high knee flexion activities, resulting in lower clinical performance.

Comparison of long-term clinical outcomes after bilateral mobile-bearing total knee arthroplasties using PCL-retaining and PCL-substituting implants in the same patients

PURPOSE

Whether the posterior cruciate ligament (PCL) should be retained or substituted in total knee arthroplasty (TKA) remains an issue of concern. The purpose of this study was to perform within-patient comparisons of mid- and long-term clinical outcomes after mobile-bearing TKA using PCL-retaining (PCLR) and PCL-substituting (PCLS) implant designs.

METHODS

Clinical outcomes were assessed in thirty-eight patients (76 knees) who underwent bilateral scheduled staged TKA with a PCLR design on one side and a PCLS design on the other. Median follow-up periods were 118 months (range 60-211) and 114 months (62-198) in knees with PCLR and PCLS implants, respectively. The preoperative diagnosis for all patients was osteoarthritis. The postoperative clinical results of mobile-bearing TKAs using PCLR and PCLS implant designs were evaluated.

RESULTS

The postoperative Hospital for Special Surgery and the new Knee Society Knee Scoring System scores revealed no differences between PCLR and PCLS implant designs. Postoperative flexion and extension also did not differ between designs. Postoperative median femorotibial alignment was 4° for PCLR and 5° for PCLS implants, respectively; this difference was not significant. Six of the knees with PCLR and three of the knees with PCLS implants had radiolucent lines around the tibial prostheses; these were less than 1 mm and nonprogressive.

CONCLUSIONS

Clinically good results were obtained at approximately 10 years after mobile-bearing TKA using both PCLR and PCLS implant designs bilaterally in the same patients. These results provide conclusive evidence that equivalent clinical results can be obtained with either implant design.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

Comparison of fixed-bearing and mobile-bearing total knee arthroplasty after high tibial osteotomy

PURPOSE

There is no information comparing the results of fixed-bearing total knee replacement and mobile-bearing total knee replacement in the same patients previously treated by high tibial osteotomy. The purpose was therefore to compare fixed-bearing and mobile-bearing total knee replacements in patients treated with previous high tibial osteotomy.

METHODS

We compared the results of 57 patients with osteoarthritis who had received a fixed-bearing prosthesis after high tibial osteotomy with the results of 41 matched patients who had received a rotating platform after high tibial osteotomy. The match was made for length of follow-up period. The mean follow-up was 17 years (range, 15-20 years). The patients were assessed clinically and radiographically.

RESULTS

The pre-operative knee scores had no statistically significant differences between the two groups. So was the case with the intra-operative releases, blood loss, thromboembolic complications and infection rates in either group. There was significant improvement in both groups of knees, and no significant difference was observed between the groups (i.e., fixed-bearing and mobile-bearing knees) for the mean Knee Society knee clinical score (95 and 92 points, respectively), or the Knee Society knee functional score (82 and 83 points, respectively) at the latest follow-up. However, the mean post-operative knee motion was higher for the fixed-bearing group (117° versus 110°). In the fixed-bearing group, one knee was revised because of periprosthetic fracture. In the rotating platform mobile-bearing group, one knee was revised because of aseptic loosening of the tibial component. The Kaplan-Meier survivorship for revision at ten years of follow-up was 95.2% for the fixed bearing prosthesis and 91.1% for the rotating platform mobile-bearing prosthesis.

CONCLUSIONS

Although we did manage to detect significant differences mainly in clinical and radiographic results between the two groups, we found no superiority or inferiority of the mobile-bearing total knee prosthesis over the fixed-bearing total knee prosthesis for patients previously operated by high tibial osteotomy.

Midterm Clinical and Radiographic Results of Mobile-Bearing Revision Total Knee Arthroplasty

BACKGROUND

Constrained implants are frequently required in revision total knee arthroplasty (TKA) and are associated with an increase in aseptic component loosening and damage or wear to the constraining mechanisms, compared with primary TKA. The purpose of the following study was to evaluate the midterm clinical and radiographic results including the incidence of bearing complications in a group of patients undergoing revision TKA using mobile-bearing revision TKA implants.

METHODS

We retrospectively reviewed 316 consecutive mobile-bearing revision TKAs performed at 2 centers between 2006 and 2010. There were 183 women and 133 men with a mean age of 66 years. The patients were evaluated clinically using the Knee Society scores. A radiographic analysis was performed. Bearing specific complications (ie, instability or dislocation) were recorded.

RESULTS

Patients were followed-up for a minimum of 24 months and a median of 59.88 months (range 24-121.2). The average Knee Society knee score and function scores increased from 40.8 and 47.9 points preoperatively to 80 points and 70.3 points, respectively (P < .01). The average knee flexion improved from 105.6° preoperatively to 117.4° postoperatively (P < .01). Eight patients required subsequent implant revision. No cases of bearing complications were observed.

CONCLUSION

Revision TKA using mobile-bearing revision components demonstrated favorable midterm clinical and radiographic results with no occurrence of bearing instability or dislocation. Longer follow-up is required to evaluate for potential advantages of mobile-bearings over fixed-bearing revision components in terms of polyethylene wear reduction, reduced stress transmission across fixation interfaces, and reduced stress on the polyethylene post.

No differences between fixed- and mobile-bearing total knee arthroplasty

PURPOSE

For years, numerous studies have been performed to determine whether mobile-bearing total knee arthroplasty (MB-TKA) or fixed-bearing total knee arthroplasty (FB-TKA) is the preferential design in total knee arthroplasty. Reviews and meta-analyses on this subject have focused on a relatively small number of randomised controlled trials, possibly missing important results of smaller studies. The goal of this review was to provide a comprehensive overview of all literature comparing MB-TKA and FB-TKA in the treatment of osteoarthritis of the knee.

METHODS

An extensive literature search was performed in the PubMed database. All studies that compared MB-TKA with FB-TKA and looked at one of four theorised advantages (insert wear, signs of loosening, survival rate of the prosthesis and clinical outcome) were included.

RESULTS

The initial search yielded 258 articles, of which 127 were included after the first screening. The included studies consisted of 9 meta-analyses, 3 systematic reviews, 48 RCT's, 44 comparative studies, 10 reviews and 13 studies that examined patients who received bilateral TKA (one MB-TKA and one FB-TKA). Combining the results of all studies showed that almost all studies found no difference between MB-TKA and FB-TKA.

CONCLUSIONS

Even when examining all different types of studies on MB-TKA and FB-TKA, the results of this review showed no difference in insert wear, risk of loosening, survivorship or clinical outcome. In daily practice, the choice between MB-TKA and FB-TKA should be based on the experience and judgment of the surgeon, since no clear differences are observed in the scientific literature.

LEVEL OF EVIDENCE

III.

No difference between fixed- and mobile-bearing total knee arthroplasty in activities of daily living and pain: a randomized clinical trial

PURPOSE

Until now, there are no definitive conclusions regarding functional differences related to middle- and long-term everyday activities and patient pain following implantation of mobile- and fixed-platform tibial prostheses. The aim of this study was to determine whether there are middle-term differences in knee function and pain in patients undergoing fixed- and mobile-bearing total knee arthroplasty (TKA).

METHODS

Eligible patients were randomized into two groups: the first group received TKA implantation with a fixed tibial platform (group A); the second group received TKA with a mobile tibial platform (group B). Patients were followed up (2 years), and their symptoms and limitations in daily living activities were evaluated using the Knee Outcome Survey-Activities of Daily Living Scale (ADLS), in addition to pain evaluation assessed using the pain visual analogue scale (VAS).

RESULTS

There were no significant differences in function and symptoms in the ADLS and VAS between the study groups.

CONCLUSION

The type of platform used in TKA (fixed vs. mobile) does not change the symptoms, function or pain of patients 2 years post-surgery. Although mobile TKAs may have better short-term results, at medium- and long-term follow-up they do not present important clinical differences compared with fixed-platform TKAs. This information is important so that surgeons can choose the most suitable implant for each patient.

LEVEL OF EVIDENCE

Randomized clinical trial, Level I.

A comparison of lateral release rates in fixed- versus mobile-bearing total knee arthroplasty

Background

With increasing functional demands of patients undergoing total knee arthroplasty, mobile-bearing (MB) implants were developed in an attempt to increase the functional outcome of such patients. In theory, with MB implants, the self-alignment should reduce the rate of lateral release of the patella, which is usually performed to optimise patellofemoral mechanics. This study reports on the lateral release rates for the P.F.C. Sigma® MB posterior-stabilised total knee replacement (TKR) implant compared with its fixed-bearing (FB) equivalent.

Materials and methods

A total of 352 patients undergoing TKR were randomly allocated to receive either MB (176 knees) or FB (176 knees) posterior-stabilised TKR. Further sub-randomisation into patellar resurfacing or retention was performed for both designs. The need for lateral patellar release was assessed during surgery using a ‘no thumb technique’, and after releasing the tourniquet if indicated.

Results

The lateral release rate was the same for FB (10 %) and MB implants (10 %) (p = 0.9). However, patellar resurfacing resulted in lower lateral release rates when compared to patellar retention (6 vs 14 %; p = 0.0179) especially in MB implants (3 %).

Conclusions

It has been previously reported that alterations to the design of the P.F.C. system with a more anatomical trochlea in the femoral component improved patellar tracking. The addition of a rotating platform tibial component to the P.F.C. Sigma system has, on its own, had no impact on the lateral release rate in this study. Optimising patellar geometry by patellar resurfacing appears more important than tibial-bearing design. Although MB implants appear to reduce the need for lateral release in the P.F.C. Sigma Rotating Platform, this only occurs when the patellar geometry has been optimised with patellar resurfacing.

Level of evidence

Level 2.

Mobile bearing vs fixed bearing prostheses for posterior cruciate retaining total knee arthroplasty for postoperative functional status in patients with osteoarthritis and rheumatoid arthritis

BACKGROUND

It is unclear whether there are differences in benefits and harms between mobile and fixed prostheses for total knee arthroplasty (TKA). The previous Cochrane review published in 2004 included two articles. Many more trials have been performed since then; therefore an update is needed.

OBJECTIVES

To assess the benefits and harms of mobile bearing compared with fixed bearing cruciate retaining total knee arthroplasty for functional and clinical outcomes in patients with osteoarthritis (OA) or rheumatoid arthritis (RA).

SEARCH METHODS

We searched The Cochrane Library, PubMed, EMBASE, CINAHL and Web of Science up to 27 February 2014, and the trial registers ClinicalTrials.gov, Multiregister, Current Controlled Trials and the World Health Organization (WHO) International Clinical Trials Registry Platform for data from unpublished trials, up to 11 February 2014. We also screened the reference lists of selected articles.

SELECTION CRITERIA

We selected randomised controlled trials comparing mobile bearing with fixed bearing prostheses in cruciate retaining TKA among patients with osteoarthritis or rheumatoid arthritis, using functional or clinical outcome measures and follow-up of at least six months.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by The Cochrane Collaboration.

MAIN RESULTS

We found 19 studies with 1641 participants (1616 with OA (98.5%) and 25 with RA (1.5%)) and 2247 knees. Seventeen new studies were included in this update.Quality of the evidence ranged from moderate (knee pain) to low (other outcomes). Most studies had unclear risk of bias for allocation concealment, blinding of participants and personnel, blinding of outcome assessment and selective reporting, and high risk of bias for incomplete outcome data and other bias. Knee painWe calculated the standardised mean difference (SMD) for pain, using the Knee Society Score (KSS) and visual analogue scale (VAS) in 11 studies (58%) and 1531 knees (68%). No statistically significant differences between groups were reported (SMD 0.09, 95% confidence interval (CI) -0.03 to 0.22, P value 0.15). This represents an absolute risk difference of 2.4% points higher (95% CI 0.8% lower to 5.9% higher) on the KSS pain scale and a relative percent change of 0.22% (95% CI 0.07% lower to 0.53% higher). The results were homogeneous. Clinical and functional scores The KSS clinical score did not differ statistically significantly between groups (14 studies (74%) and 1845 knees (82%)) with a mean difference (MD) of -1.06 points (95% CI -2.87 to 0.74, P value 0.25) and heterogeneous results. KSS function was reported in 14 studies (74%) with 1845 knees (82%) as an MD of -0.10 point (95% CI -1.93 to 1.73, P value 0.91) and homogeneous results. In two studies (11%), the KSS total score was favourable for mobile bearing (159 vs 132 for fixed bearing), with MD of -26.52 points (95% CI -45.03 to -8.01, P value 0.005), but with a wide 95% confidence interval indicating uncertainty about the estimate.Other reported scoring systems did not show statistically significant differences: Hospital for Special Surgery (HSS) score (seven studies (37%) in 1021 knees (45%)) with an MD of -1.36 (95% CI -4.18 to 1.46, P value 0.35); Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total score (two studies (11%), 167 knees (7%)) with an MD of -4.46 (95% CI -16.26 to 7.34, P value 0.46); and Oxford total (five studies (26%), 647 knees (29%) with an MD of -0.25 (95% CI -1.41 to 0.91, P value 0.67). Health-related quality of lifeThree studies (16%) with 498 knees (22%) reported on health-related quality of life, and no statistically significant differences were noted between the mobile bearing and fixed bearing groups. The Short Form (SF)-12 Physical Component Summary had an MD of -1.96 (95% CI -4.55 to 0.63, P value 0.14) and heterogeneous results. Revision surgeryTwenty seven revisions (1.3%) were performed in 17 studies (89%) with 2065 knees (92%). In all, 13 knees were revised in the fixed bearing group and 14 knees in the mobile bearing group. No statistically significant differences were found (risk difference 0.00, 95% CI -0.01 to 0.01, P value 0.58), and homogeneous results were reported. MortalityIn seven out of 19 studies, 13 participants (37%) died. Two of these participants had undergone bilateral surgery, and for seven participants, it was unclear which prosthesis they had received; therefore they were excluded from the analyses. Thus our analysis included four out of 191 participants (2.1%) who had died: one in the fixed bearing group and three in the mobile bearing group. No statistically significant differences were found. The risk difference was -0.02 (95% CI -0.06 to 0.03, P value 0.49) and results were homogeneous. Reoperation ratesThirty reoperations were performed in 17 studies (89%) with 2065 knees (92%): 18 knees in the fixed bearing group (of the 1031 knees) and 12 knees in the mobile group (of the 1034 knees). No statistically significant differences were found. The risk difference was -0.01 (95% CI -0.01 to 0.01, P value 0.99) with homogeneous results. Other serious adverse eventsSixteen studies (84%) reported nine other serious adverse events in 1735 knees (77%): four in the fixed bearing group (of the 862 knees) and five in the mobile bearing group (of the 873 knees). No statistically significant differences were found (risk difference 0.00, 95% CI -0.01 to 0.01, P value 0.88), and results were homogeneous.

AUTHORS' CONCLUSIONS

Moderate- to low-quality evidence suggests that mobile bearing prostheses may have similar effects on knee pain, clinical and functional scores, health-related quality of life, revision surgery, mortality, reoperation rate and other serious adverse events compared with fixed bearing prostheses in posterior cruciate retaining TKA. Therefore we cannot draw firm conclusions. Most (98.5%) participants had OA, so the findings primarily reflect results reported in participants with OA. Future studies should report in greater detail outcomes such as those presented in this systematic review, with sufficient follow-up time to allow gathering of high-quality evidence and to inform clinical practice. Large registry-based studies may have added value, but they are subject to treatment-by-indication bias. Therefore, this systematic review of RCTs can be viewed as the best available evidence.

Patellar clunk syndrome in fixed-bearing posterior-stabilised versus cruciate-substituting prostheses

PURPOSE

To compare the outcome of fixed-bearing posterior-stabilised versus cruciate-substituting prostheses in 46 patients who underwent primary bilateral total knee replacement (TKR).

METHODS

Records of 35 women and 11 men aged 54 to 78 (mean, 67) years who underwent primary bilateral TKR for osteoarthritis (n=44) and rheumatoid arthritis (n=2) were retrospectively reviewed. A fixed-bearing posterior-stabilised prosthesis (Zimmer NexGen Legacy flex [LPS-Flex]) was used in one knee, and a fixed-bearing cruciate-substituting prosthesis (Depuy Press Fit Condylar Sigma CS [PFC CS]) was used in the contralateral knee. The mean time interval between the 2 operations was 34 (range, 4-60) months. All operations were performed by the same group of surgeons using standardised techniques. The medial parapatellar approach was used, and the patella was resurfaced. Rehabilitation was also standardised. Outcome measures included the pre- and post-operative active range of movement and the American Knee Society Score. Postoperative complications were documented.

RESULTS

At one year, the mean fixed flexion contracture, maximum flexion, and American Knee Society scores in knees with PFC CS and LPS-Flex prostheses were comparable. Three knees with the PFC CS prosthesis developed the patellar clunk syndrome, compared to none with the LPS-Flex prosthesis (p=0.24). The onset of the patellar clunk syndrome was around one year after surgery. Despite this, the axial alignment and rotation of the femoral and tibial components were good.

CONCLUSION

Both prostheses produce good clinical outcome. The PFC CS prosthesis is more likely to be associated with the patellar clunk syndrome.

Mobile bearing or fixed bearing? A meta-analysis of outcomes comparing mobile bearing and fixed bearing bilateral total knee replacements

BACKGROUND

To compare outcomes between mobile-bearing (MB) and fixed-bearing (FB) in bilateral total knee replacements.

METHODS

The MEDLINE, EMBASE and Cochrane Library databases were searched. Randomized controlled trials of bilateral total knee arthroplasty with one of each design implanted were identified. Weighted mean differences (WMDs) and pooled risk ratios (RRs) were calculated using fixed- or random-effects models.

RESULTS

Twelve studies were identified with a total of 807 patients and 1614 knees. All RCTs were of high quality with a low risk of bias. No statistical difference was found between MB and FB at 2- to 5-year follow-up in terms of America Knee Society score (WMD: -1.29, 95% CI: -5.65 to 3.06), pain score (WMD: -3.26, 95% CI: -10.45 to 3.93), range of motion (WMD: -4.16, 95% CI: -9.97 to 1.66), reoperation (RR: 1.00, 95% CI: 0.28 to 3.60), and radiolucent lines (RR: 1.51, 95% CI: 0.70 to 3.24). The results were similar at 1-, 5- to 8-, or >8-year follow-up. Patient's satisfaction (RR: 0.85, 95% CI: 0.54 to 1.34), and complication (≤2-year, RR: 0.55, 95% CI: 0.29 to 1.04; >2-year, RR: 1.0, 95% CI=0.73 to 1.38) also showed no difference between two groups.

CONCLUSIONS

Based on this meta-analysis we are unable to detect the superiority of MB as compared to FB. More randomized trials with a larger sample size and longer follow-up are needed to evaluate these two kinds of prosthesis.

LEVEL OF EVIDENCE

Therapeutic Level II.

No difference in clinical outcome between fixed- and mobile-bearing TKA: a meta-analysis

PURPOSE

To compare the clinical and radiographic results of fixed-bearing and mobile-bearing total knee arthroplasty (TKA).

METHODS

We searched the PubMed, Medline, Embase, Cochrane Central Register of Controlled Trials, and Google Scholar databases from 1966 to January 2012. No language restriction was applied. Reference lists of all the selected articles were hand-searched for any additional trials. Trial quality was assessed using the modified Jadad scale. Two authors independently extracted data from all eligible studies, including study design, participants, interventions, and outcomes (Knee Society Score, range of movement, radiolucent line, patient preference, walking support, pain score, and complications). The data were using fixed-effects or random-effects models with mean differences and risk ratios for continuous and dichotomous variables, respectively.

RESULTS

A total of 24 studies involving 2,799 patients were identified in this analysis. Meta-analysis showed lower pain score (OR, 0.66, 95% CI 0.46, 0.94) in mobile-bearing TKA than fixed-bearing TKA. There was no significant difference between the two treatment groups regarding Knee Society Score (SMD, -0.17, 95% CI: -0.60, 0.26), range of movement (SMD, -0.05, 95% CI: -0.63, 0.53), radiolucent line (OR, 1.03, 95% CI 0.74, 1.44), patient preference (OR, 1.15, 95% CI 0.82, 1.61), walking support (OR, 1.07, 95% CI 0.68, 1.70), and complications (OR, 0.85, 95% CI 0.59, 1.21).

CONCLUSIONS

The available evidence suggested that there was no significant difference between clinical and radiographic results of fixed-bearing and mobile-bearing TKA except for pain score. Regarding clinical relevance, the less incidence of pain could be the advantage for selecting mobile-bearing TKA.

LEVEL OF EVIDENCE

II.

A prospective randomised study comparing rotating platform and fixed bearing total knee arthroplasty in a cruciate substituting design--outcomes at two year follow-up

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 randomised prospective 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 randomised into receiving either a PFC Sigma© cruciate sacrificing total knee arthroplasty either with a mobile bearing or a fixed bearing, with a sub-randomisation to either patella resurfacing or patella retention. All patients participated with standard 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 designs. With no clinical difference between the cohorts, we cannot recommend one design over the other. Long term benefits, particularly with regards to polyethylene wear, may yet be demonstrated. Level of evidence--1B.

A systematic review and meta-regression of mobile-bearing versus fixed-bearing total knee replacement in 41 studies

Mobile-bearing (MB) total knee replacement (TKR) was introduced to reduce the risk of aseptic loosening and wear of polyethylene inserts. However, no consistent clinical advantages of mobile- over fixed-bearing (FB) TKR have been found. In this study we evaluated whether mobile bearings have an advantage over fixed bearings with regard to revision rates and clinical outcome scores. Furthermore, we determined which modifying variables affected the outcome. A systematic search of the literature was conducted to collect clinical trials comparing MB and FB in primary TKR. The primary outcomes were revision rates for any reason, aseptic loosening and wear. Secondary outcomes included range of movement, Knee Society score (KSS), Oxford knee score (OKS), Short-Form 12 (SF-12) score and radiological parameters. Meta-regression techniques were used to explore factors modifying the observed effect. Our search yielded 1827 publications, of which 41 studies met our inclusion criteria, comprising over 6000 TKRs. Meta-analyses showed no clinically relevant differences in terms of revision rates, clinical outcome scores or patient-reported outcome measures between MB and FB TKRs. It appears that theoretical assumptions of superiority of MB over FB TKR are not borne out in clinical practice.

Is there reduced polyethylene wear and longer survival when using a mobile-bearing design in total knee replacement?

The purpose of this study was to undertake a meta-analysis to determine whether there is lower polyethylene wear and longer survival when using mobile-bearing implants in total knee replacement when compared with fixed-bearing implants. Of 975 papers identified, 34 trials were eligible for data extraction and meta-analysis comprising 4754 patients (6861 knees). We found no statistically significant differences between the two designs in terms of the incidence of radiolucent lines, osteolysis, aseptic loosening or survival. There is thus currently no evidence to suggest that the use of mobile-bearing designs reduce polyethylene wear and prolong survival after total knee replacement.

Cite this article: Bone Joint J 2013;95-B:1057–63.

Fixed versus mobile weight-bearing prosthesis in total knee arthroplasty

PURPOSE

This study was designed 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 randomized 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

I.

In vivo kinematics of high-flex mobile-bearing total knee arthroplasty, with a new post-cam design, in deep knee bending motion

PURPOSE

The objective of this study was to evaluate the in vivo knee kinematics to assess the available functional motion of the characteristic mobile-bearing prosthesis design and to examine whether the artificial joint would work in vivo according to its design concept.

METHODS

We studied 14 knees (11 patients) implanted with the Vanguard RP Hi-Flex prosthesis. This prosthesis has a highly original form of post-cam called a PS saddle design with high compatibility, and with a rotating plate mobile-bearing mechanism. The cylinder-type post-cam is designed to enable contact in early flexion ranges, and to prevent paradoxical anterior femoral component movement. Each patient performed weight-bearing deep knee bending under fluoroscopic surveillance. Motion between each component including the polyethylene insert was analyzed using the 2D/3D registration technique.

RESULTS

The mean range of motion was 122.0°. The mean femoral component rotation for the tibial tray was 5.0°. No paradoxical anterior movement of the nearest point was confirmed between the femoral component and the tibial tray in the early flexion ranges. Initial contact of the post-cam was confirmed at a knee flexion angle of 33.8°. Subsequently, the wide contact of the post-cam was maintained until flexion reached 120° in all knees, but disengagement of the post-cam was observed in two knees when flexion was ≥130°.

CONCLUSIONS

The results of this study demonstrated that the prosthesis design generally works in vivo as intended by its design concept. The present kinematic data may provide useful information for improvement of high-flex type prostheses.

Mid- term results of stryker® scorpio plus mobile bearing total knee arthroplasty

BACKGROUND

The mobile bearing knee system was introduced to lessen contact stress on the articular bearing surface and reduce polyethylene wear. The purpose of the current study was to investigate the mid-term results of patients undergoing total knee arthroplasties (TKAs) using Scorpio Plus Mobile Bearing Knee System (Stryker, Mahwah, NJ), and compare the outcomes between patients with osteoarthritis and osteonecrosis (OA·ON group) and patients with rheumatoid arthritis (RA group).

METHODS

Eight males and 58 females were followed up for a period of 4.4- 7.6 years from June 1, 2003 to December 31, 2005. There were 53 knees with osteoarthritis, 17 knees with rheumatoid arthritis, and 6 knees with osteonecrosis. Clinical and radiographic follow- up was done using The Japanese Orthopedic Association knee rating score (JOA score) and Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System.

RESULTS

With regard to the JOA score, there was significant improvement in both groups. The postoperative range of motion was between 0.8°and 116.8° in OA·ON group, and between 0.0° and 113.7° in RA group. There were no significant differences with the radiographic evaluation between two groups. Spontaneous dislocation of a polyethylene insert occurred in one patient, and deep infection was occurred in one patient.

CONCLUSION

There was significant improvement with regard to the clinical and radiographic results of patients undergoing TKAs using the model. The risk of polyethylene insert dislocation related to the mobile bearing TKA is a cause for concern.

Differences in long-term fixation between mobile-bearing and fixed-bearing knee prostheses at ten to 12 years’ follow-up

This single-blinded randomised 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 randomised 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 clinically relevant.

Functional performance of mobile versus fixed bearing total knee prostheses: a randomised controlled trial

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 designed as a randomised controlled multi-centre trial.

METHODS

Participants were assigned to interventions by using block-stratified, random 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

I.

Gait analysis and electromyography in fixed- and mobile-bearing total knee replacement: a prospective, comparative study

PURPOSE

The theoretical superiority of mobile-bearing total knee arthroplasties (TKAs) has not yet been proven in clinical studies. The aim of the current study was to compare and to analyse in a patient population that had received either a fixed or a mobile TKA differences in gait analysis electromyography and clinical scores.

METHODS

In a prospective, randomized, patient- and observer-blinded clinical study, 33 patients with primary osteoarthritis of the knee were included. All patients received a Genesis II total knee replacement. Sixteen patients received a mobile and 17 a fixed-bearing cruciate retaining Genesis II TKA. Clinical and quality-of-life scores, electromyography and gait analysis were applied preoperatively and postoperatively with a follow-up of 24 months.

RESULTS

In both groups, improvements from pre- to postoperative were detected. whereas the results of gait analysis and electromyography did not show any differences. The results from the clinical and the quality-of-life scores improved from pre- to postoperative, while the Knee Society Score showed a superiority of the mobile-bearing group (mean 159 ± 28) over the fixed-bearing group (mean 134 ± 41).

CONCLUSION

No functional advantage of mobile over fixed-bearing TKA was detected, although the mobile-bearing group had better clinical results for which a reason could not be found. These results only apply to cruciate retaining mobile-bearing TKA with a bearing which allows both rotation and anteroposterior translation.

Meta-analysis and systematic review of clinical outcomes comparing mobile bearing and fixed bearing total knee arthroplasty

Mobile bearing (MB) knee replacements were designed with the goal of increased conformity and decreased bearing wear. We conducted a meta-analysis and systematic review of randomized controlled trials comparing outcomes of MB and fixed bearing (FB) total knee arthroplasty (TKA). We identified 14 studies reporting our primary outcome of Knee Society Scores (KSS). We also pooled data for post-operative range of motion (ROM) and Hospital for Special Surgery scores (HSS). The standard difference in mean outcome scores for KSS and HSS demonstrated no difference between groups (P = .902, and P = .426 respectively). Similarly, the pooled data for ROM showed no difference between groups (P = .265). The results of this study found no significant differences between clinical outcomes of MB and FB TKA.

A meta-analysis of the fixed-bearing and mobile-bearing prostheses in total knee arthroplasty

INTRODUCTION

We asked whether the mobile-bearing knee prostheses could offer clinical and radiographic advantages over the fixed-bearing knee prostheses.

MATERIALS AND METHODS

We conducted a systematic review and meta-analysis to evaluate the validity of this theory. We searched PubMed, EMBASE, Ovid and the Cochrane Central Register of Controlled Trials from January 1979 to June 2010 for randomized controlled studies comparing the effect of fixed- and mobile-bearing prostheses in TKA. We assessed the methodological quality of the studies and abstracted the relevant data independently.

RESULTS

15 studies involving 1,950 knees were identified in this analysis. No statistically significant difference was present in terms of KSS, patient preference, radiolucent line around implant and prosthesis-related complications as compared to the fixed- and mobile-bearing knee design.

CONCLUSIONS

Theoretically, mobile-bearing implant design could improve clinical and radiographic outcomes as being compared to fixed-bearing implant design, but the anticipated effectiveness has not been implemented in the current clinical practice at mid-term follow up.

In vivo kinematics of mobile-bearing total knee arthroplasty during deep knee bending under weight-bearing conditions

PURPOSE

Little is known about the in vivo kinematics of mobile-bearing total knee arthroplasty, especially at deep knee flexion under weight-bearing conditions.

METHODS

In vivo knee kinematics was analyzed for 12 patients (13 knees) implanted with PFC-Sigma Rotating Platform-Flex (RP-F) prostheses. Under fluoroscopic surveillance, each patient performed weight-bearing deep knee bending. Motion between each component was analyzed using a two- to three-dimensional registration technique, which uses computer-assisted design models to reproduce the spatial positions of the femoral and tibial components and a polyethylene insert (implanted with four tantalum beads) from single-view fluoroscopic images.

RESULTS

External rotation of the femoral component on the tibial tray was mostly caused by rotation of the polyethylene insert on the tibial tray. The femoral component typically exhibited a central pivot pattern from extension to 80° relative to the tibial component. From 80° to 120°, bilateral condyles moved backward. In an upright standing position, the femoral component had already rotated externally relative to the tibial component by 7.8±7.5°, and the polyethylene insert had also rotated 8.2°±6.2° externally on the tibial tray.

CONCLUSION

The present results demonstrated that mobile-bearing mechanisms with this prosthesis might reduce articular contact stress in vivo.

Mobile-bearing total knee arthroplasty: a meta-analysis

An extensive database search was completed to perform a meta-analysis of outcomes of mobile-bearing total knee arthroplasty. Nineteen manuscripts encompassing 3506 total knee arthroplasty met criteria for analysis (average follow-up, 8.6 years). Data were subdivided based on design type and included rotating platform, meniscal bearing, and anterior-posterior glide-rotation subgroups. Fifteen-year survivorship of rotating platform designs (96.4%) was greater than meniscal bearing implants (86.5%). Mean component loosening (0.33%) and bearing instability (<1%) for all subgroups were uncommon. Implants placed prior to 1995 exhibited higher rates of bearing complications (1.6% vs 0.1%). Excellent results were obtained with mobile-bearing TKA over 2 decades. Loosening and bearing instability were uncommon. Bearing complications lessened after 1995, possibly secondary to improved surgical technique.

One year after navigated total knee replacement, no clinically relevant difference found between fixed bearing and mobile bearing knee replacement in a double-blind randomized controlled trial

Background:

The mobile bearing designs have not yet been shown to improve clinical outcome of total knee arthroplasty (TKA). In this prospective randomized study, we compared the short-term clinical results of a mobile bearing implant with those of the fixed bearing version of the same implant.

Methods:

We randomized 100 knees into two double-blind groups who received either the fixed (FB, 52 knees) or the mobile bearing (MB, 48 knees) version of the same implant. We used navigation to standardize the surgical technique. For up to one year, we recorded the Knee Society (KSS) and Oxford (OXF) scores. We performed an exploratory analysis of variance (ANOVA) to determine the influence of baseline scores as covariate and the extent of improvement in clinical outcome over time.

Results:

After one year, we did not detect any statistically significant difference between the two groups. The KSS scores differed by 2 points, the OXF scores by 1.1 points.

Conclusion:

Even with identical geometry of implant surfaces and a navigated surgical technique, first-year results do not support a preference for either a fixed or a mobile design.

Rotaglide total knee arthroplasty: a long-term follow-up study

BACKGROUND

Mobile-bearing knee designs represent an alternative to conventional fixed-bearing implants in total knee arthroplasty. The purpose of this study was to determine the clinical results of a mobile-bearing knee implant.

METHODS

From 1990 to 1998, 326 primary consecutive mobile-bearing total knee prostheses were implanted in 260 patients who had a mean age and standard deviation of 66.7 ± 6.9 years. Femoral and tibial components were cemented in all knees, and the patella was resurfaced in 199 knees (61%). Patients were evaluated with the use of the Knee Society clinical rating system and radiographic examinations. Complications were noted, and survivorship of the prostheses was determined.

RESULTS

The mean follow-up period was 156 ± 27.3 months, with maximum follow-up at eighteen years. The mean Knee Society knee score improved from 32.4 ± 21.2 preoperatively to 92.6 ± 10.0 at the time of the last follow-up (p = 0.00), and the mean Knee Society functional score improved from 39.3 ± 18.7 preoperatively to 66.7 ± 18.6 at the time of the last follow-up (p = 0.00). Mean knee flexion improved from 92.3° ± 14.5° preoperatively to 112.1° ± 13.4° at the time of the last follow-up (p = 0.00). There were twenty-four (7.4%) knees that required revision. In eighteen (5.5%) knees, worn out or broken polyethylene was found and a polyethylene-only exchange was done. Six knees (1.8%) were fully revised. The survival rate was 0.96 (95% confidence interval, 0.93 to 0.98) at ten years and 0.87 (95% confidence interval, 0.79 to 0.93) at eighteen years.

CONCLUSIONS

A fully congruent, mobile-bearing total knee prosthesis had excellent survivorship during the ten to eighteen-year follow-up interval.

Mobile-bearing prosthesis did not improve mid-term clinical results of total knee arthroplasty

A prospective study was performed to compare the clinical and radiological results of mobile- and fixed-bearing total knee arthroplasty with specific attention to rotational alignment and range of motion. Sixty-one knees were assigned to total knee arthroplasty with either the NexGen LPS Flex fixed-bearing or with the NexGen LPS Flex mobile-bearing prosthesis. Postoperatively, knees were compared with regard to range of motion, clinical score, and radiographic findings. Rotational alignment of the femoral and tibial components was evaluated by computed tomography. The median follow-up period was 5.9 years (range 2.1-8.8 years). Median postoperative Knee Society scores were 99 points (68-100) for the fixed-bearing group and 100 points (66-100) for the mobile-bearing group (n.s.). The median postoperative flexion angles of 120° (90°-150°) for the fixed-bearing group and 125° (90°-145°) for the mobile-bearing group were not significantly different from each other (n.s.). No knee required revision surgery due to wear of polyethylene or loosening of the component in either group. Computed tomography showed that 11 knees had rotational mismatches of more than 10° between the femoral and tibial components, but no significant difference was found in the postoperative extension and flexion angles or in the clinical score between the two treatment groups. Using the identical design for both fixed- and mobile-bearing prostheses, this prospective, randomized study did not show any clinical advantages of the mobile-bearing knee. Analysis of rotational alignment by CT scan did not reveal a particular advantage of the self-aligning mechanism of mobile-bearing implants.

Early clinical outcomes of floating platform mobile-bearing TKA: longitudinal comparison with fixed-bearing TKA

This study was conducted to longitudinally compare a new floating platform mobile-bearing (MB) prosthesis with an established fixed-bearing (FB) system with respect to early clinical outcomes in patients with bilateral TKAs using the MB prosthesis in one knee and the FB prosthesis in the other. Clinical outcomes (ROM, AKS and WOMAC scores, and side preference), evaluated at 6, 12 and 24 months postoperatively, were compared between knees fitted with the MB prosthesis (e.motion-FP) or the FB prosthesis (Genesis II) in 66 patients who underwent bilateral TKA. In addition, the same comparisons between the knees fitted with the MB prosthesis and the knees with the FB prosthesis were made separately in the subgroup of 33 patients implanted with a cruciate retaining FB (FB-CR) prosthesis and the other subgroup of 33 patients with a posteriorly stabilized FB (FB-PS) prosthesis in a knee. The floating platform MB prosthesis achieved comparable clinical outcomes to the FB prosthesis. No significant differences were found between the FB- and MB-implanted sides at any time with respect to the outcome scales, and temporal patterns were similar. However, comparisons of FB-CR and FB-PS patient groups revealed different temporal patterns. In the FB-CR group, most outcome scales were improved at 6 months, peaked at 12 months and then remained at this level at 24 months. In contrast, outcomes in the FB-PS group improved much faster to almost peak at 6 months, and then remained at this level. In the FB-CR group, more patients preferred the knee with fitted with a MB prosthesis at 6 months. In contrast, in the FB-PS group, no side preference for the MB prosthesis was observed, and more patients preferred knees implanted with the FB prosthesis at 12 and 24 months. This study demonstrates that this new mobile-bearing prosthesis, designed as a floating platform, provides satisfactory clinical performances that are comparable to those achieved using the established fixed-bearing prosthesis in terms of clinical outcomes.

Clinical and radiological outcomes of fixed- versus mobile-bearing total knee replacement: a meta-analysis

Controversy exists regarding the clinical and radiological differences in outcomes between fixed- and mobile-bearing total knee replacements (TKR). The aim of this study was to compare these two TKR designs using a meta-analysis of the electronic databases MEDLINE, EMBASE, CINAHL and AMED in addition to a review of unpublished material. All included papers were critically appraised using a modified PEDro critical appraisal tool. Thirty-three studies were eligible, assessing the outcomes of 3532 TKRs. Analysis suggested that there was no significant difference in clinical or radiological outcomes and complication rates between fixed- and mobile-bearing TKRs.

Mid-term results with a highly congruous mobile-bearing knee prosthesis

Two hundred and six consecutive total knee arthroplasties were performed in 180 patients with a highly congruous mobile-bearing knee prosthesis. At mean follow-up of 78 months (range: 60-102 months), the outcomes of 181 knees in 158 patients were evaluated using the American Knee Society's Knee and Functional scoring system and Radiological scoring system. Mean values for Knee and Function scores were 92.6 and 81.1, respectively versus 51.8 and 43.4 preoperatively; mean flexion range was 113.6 degrees versus 110.8 degrees preoperatively. There were no cases of bearing dislocation and no radiological signs of loosening or osteolysis. Secondary patella resurfacing was done in 7 of 52 knees in which the patella was not primarily resurfaced. Arthroplasty survival with revision for aseptic loosening as the endpoint was 100% (95% CI: 97.7-100) at 5 years and at 8 years (95% CI: 87.2-100); with revision of the arthroplasty for any reason including one revision for infection as the endpoint, survival was 99.5% (95% CI: 96.9-100) at 5 years and at 8 years (95% CI: 86.9-100). The overall results were satisfactory and compared with those of other mobile-bearing knee prostheses featuring full or partial congruence. No significant differences were noted for range of motion, knee scores and function scores between two subsets of knees that received a bearing allowing only rotation or rotation and 5 mm anteroposterior translation. Longer follow-up is needed to evaluate possible benefits of high congruence and of specific modes of bearing mobility with respect to wear and bony fixation.

Simultaneous bilateral total knee replacement: a persistent controversy

The benefits and risks of Simultaneous Bilateral Total Knee Replacement (SBTKR) remain controversial. A review of the English speaking literature was undertaken and found that many papers took staunch positions either for or against the procedure. It was also noted that earlier papers supporting SBTKR suggested cost benefits. There was a huge disparity in the incidence of mortality and morbidity and it was not possible to compare many papers, because in some medically frail patients were excluded from the SBTKR cohorts. In large published series the proportion of patients having a SBTKR varied between 3% and 70%. Many, but not all, series highlighted age and co-morbidity as risk factors. Overall there was no clear case for or against SBTKR. The evidence suggested that careful preoperative assessment and patient selection on a strict protocol were essential. The procedure should be confined to hospitals where high dependency nursing is readily available and the literature indicated that the risk is less in high through-put units. By refining preoperative assessment and preparation it can be a safe and effective procedure in an appropriate clinical setting for postoperative care.

Functional outcome of PFC Sigma fixed and rotating-platform total knee arthroplasty. A prospective randomised controlled trial

The aim of this study was to determine whether there is a difference in functional outcome between the PFC Sigma fixed-bearing and rotating-platform total knee replacement systems. One hundred twenty patients were randomised to receive either a fixed-bearing or rotating-platform PFC Sigma total knee replacement. Range of movement (ROM), Oxford knee score (OKS) and Knee Society score (KSS) were assessed independently before and one year after surgery. Weight-bearing X-rays were taken immediately and one year post surgery to determine the incidence of osteolysis and loosening. At a mean follow-up of 13.4 months there was no statistically significant difference in mean ROM, OKS and KSS between the two groups. There was no evidence of osteolysis or loosening in either of the groups and no revision for infection or implant failure. This study shows that there is no statistically significant difference in functional outcome between the two types of implants at short-term follow-up.

Meta-analysis comparing outcomes of fixed-bearing and mobile-bearing prostheses in total knee arthroplasty

Study findings have been inconsistent in confirming advantages for mobile-bearing compared with fixed-bearing prostheses for total knee arthroplasty. Therefore, we did meta-analysis of trials comparing outcomes from using the 2 different designs. Of 5670 citations identified for screening, 10 trials reporting 620 participants (906 knees) at final follow-up were eligible for data extraction and meta-analysis. The meta-analysis did not find a significant difference in the American Knee Society Knee Scores, Knee Society Functional and Pain Scores, range of motion, occurrence of radiolucent lines, prosthesis-related complications, and participant preference. The results suggest that the mobile-bearing prosthesis does not offer clinical or radiologic advantage over the fixed-bearing prosthesis.

Fixed- versus mobile-bearing total knee arthroplasty in Indian patients

PURPOSE

To compare the mid-term clinical outcomes in Indian patients after total knee arthroplasty (TKA) using a fixed- or mobile-bearing prosthesis.

METHODS

120 consecutive patients (50 men and 70 women) aged 55 to 76 (mean, 63) years who had arthritis of the knee with similar deformity and range of motion were randomised to undergo TKA using a fixed- or mobile-bearing prosthesis. Patients with mediolateral instability and infective arthritis were excluded. Knee Society knee and functional scores, range of motion, and the presence of flexion contracture were assessed.

RESULTS

The mean follow-up duration was 3.5 (range, 1-4.6) years. The mid-term outcome of the 2 groups was comparable. One patient with a mobile-bearing prosthesis had recurrent dislocation at postoperative week 2, owing to iatrogenic medial collateral ligament injury.

CONCLUSION

Long-term studies of both functional and radiological outcomes are needed to determine the indications for fixed- versus mobile-bearing prostheses.

Relationship between joint gap difference and range of motion in total knee arthroplasty: a prospective randomised study between different platforms

The objective of this study was to investigate the range of motion (ROM) of the knee before and four years after total knee arthroplasty (TKA) with a mobile or fixed type of platform and to prospectively evaluate whether there was a difference in ligament balance between the platform types. The subjects were 68 patients involving 76 joints. The mobile type was used in 31 joints and fixed type in 45 joints by employing a prospective randomised method. The passive maximum ROM was measured using a goniometer before and four years after surgery. Also, the intraoperative knee ligament balance was measured. The postoperative extension ROM was significantly improved after TKA using a mobile bearing type compared with that employing a fixed bearing type. In TKA using the former, the intraoperative gap difference was not related to the postoperative flexion angle of the knee. However, they were related in TKA using a fixed bearing type, with a positive correlation regarding the flexion gap.

A 5 to 8 year follow-up study of the Rotaglide mobile bearing total knee arthroplasty

We report the medium-term outcomes of the Rotaglide mobile bearing total knee arthroplasty (RTK). Between 1994 and 1999, 357 RTK prostheses were implanted at our institution. Of 150 knees attending for follow-up, none had needed revision. Mean American Knee Society Score (AKSS), Oxford knee score and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score at 8 years were 153.6, 23.1 and 16.5, respectively. Radiological analysis revealed no prosthesis with signs of impending failure requiring revision. Survivorship was 100% in those attending. However, we are aware of two failures requiring revision, both of which were due to infection. We have no reported failures requiring revision due to aseptic loosening. This may be a result of the implant design. Limitations of the study include loss to follow-up and radiological analysis. The RTK gives good to excellent medium-term results and we support its continued use.

[Fixed-bearing versus mobile-bearing total knee arthroplasty: a prospective randomized clinical and radiological study]

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 prospective randomized 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 protocols 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 reviewed 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.

Comparison of a new mobile-bearing total knee prosthesis with a fixed-bearing prosthesis: a matched pair analysis

BACKGROUND

New prosthesis designs should provide either superior function or durability. Before long time follow up studies are started it should at least prove its effectiveness in clinical outcomes. Therefore we have studied the early clinical results of a new mobile bearing total knee prosthesis (e.motion; Aesculap) in comparison with our established fixed-bearing device (PFC; DePuy) in a matched-pair analysis.

PATIENTS AND METHODS

About 30 consecutive patients received the new mobile bearing device and were matched with patients who received the PFC prosthesis according to age, gender, weight, axis and preoperative AKS-score. Outcomes were measured using the scores that are routinely documented in our arthroplasty register namely the American Knee Society Score (AKSS), the Oxford Knee Score (OKS), Functional Questionnaire of Hannover for Osteoarthritis (FFbH-OA), range of motion (ROM) and knee pain before and 2 years after the operation.

RESULTS

No statistical differences could be found neither preoperative nor postoperative. Nevertheless the mobile bearing device had a slightly better ROM and function score.

CONCLUSION

This new device proved to be at least as effective in early clinical outcome as the established fixed bearing prosthesis. It has to be awaited whether it is advantageous in the long run.

An 8- to 10-year review of the Rotaglide total knee replacement

Mobile-bearing knee arthroplasty (MBKA) is an alternative to fixed-bearing knee arthroplasty. This was a retrospective study of the Rotaglide Total Knee System. We present the results of the monitoring of 77 patients (85 knees) with a median duration to failure or end of follow up of 8.5 years (range 0.4 to 10.1 years). Patients were clinically and radiologically assessed at dedicated follow up clinics. The Hospital for Special Surgery (HSS) and Knee Society Score (KSS) systems were used to describe the clinical and radiological findings. The prosthesis had an estimated survival probability of 93.5% (standard error 3.4%) at 9 years. It is associated with good rates of patient satisfaction and high scores on the HSS and KSS systems. No knees were revised for aseptic loosening. This knee replacement has a survival rate equivalent to other prostheses. It is a safe and reliable prosthesis associated with good clinical outcome.

Fixed or mobile-bearing total knee arthroplasty

Fixed and mobile-bearing in total knee arthroplasty are still discussed controversially. In this article, biomechanical and clinical aspects in both fixed and mobile-bearing designs were reviewed. In biomechanical aspect, the mobile-bearing design has proved to provide less tibiofemoral contact stresses under tibiofemoral malalignment conditions. It also provides less wear rate in in-vitro simulator test. Patients with posterior stabilized mobile-bearing knees had more axial tibiofemoral rotation than patients with posterior stabilized fixed-bearing knees during gait as well as in a deep knee-bend activity. However, in clinical aspect, the mid-term or long-term survivorship of mobile-bearing knees has no superiority over that of fixed-bearing knees. The theoretical advantages for mobile-bearing design to provide a long-term durability have not been demonstrated by any outcome studies. Finally, the fixed-bearing design with all-polyethylene tibial component is suggested for relatively inactive, elder people. The mobile-bearing design is suggested for younger or higher-demand patients due to the potential for reduced polyethylene wear and more normal kinematics response after joint replacement. For younger surgeon, the fixed-bearing design is suggested due to less demand for surgical technique. For experienced surgeon, one familiar surgical protocol and instrumentation is suggested rather than implant design, either fixed-bearing or mobile-bearing.

Mobile-bearing total knee arthroplasty: design factors in minimizing wear

Premature polyethylene wear is a major cause of total knee arthroplasty (TKA) failure. It has been attributed to numerous factors including poor surgical technique, reduced polyethylene thickness, poor locking mechanisms of modular fixed bearing tibial components, gamma irradiation sterilization techniques in the presence of oxygen, and low conformity implant designs. The incidence of implantation of TKA into younger patients who have increased activity requirements and longevity expectations is increasing. This requires continued analysis of design features lessening polyethylene wear. The purpose of this manuscript is to review clinical and basic scientific studies of factors influencing polyethylene wear, focusing on the potential benefits of mobile bearing TKA which potentially reduce long-term polyethylene wear by providing increased implant conformity and reduced polyethylene contact stresses. In vivo kinematic studies have shown self-alignment of the polyethylene bearing with the femoral component typically occurs in rotating platform TKA designs which should hypothetically lessen polyethylene surface stresses, minimize stabilizing post impingement, and increase the potential for enhanced polyethylene longevity.