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

Patellar resurfacing in knee arthroplasty: A comprehensive review and meta-analysis

BACKGROUND

Patellar resurfacing in knee arthroplasty remains a contentious issue, with various strategies including routine, selective, and non-resurfacing approaches. This review and meta-analysis aim to assess the incidence of patellar resurfacing, revision rates, patient satisfaction, and relevant knee scores associated with each method.

AIM

To determine the comparative effectiveness of routine, selective, and non-resurfacing strategies in patellar resurfacing within knee arthroplasty by evaluating incidence rates, revision rates, patient satisfaction, and knee function scores.

METHODS

A systematic review spanning from 1990 to 2024 was conducted using PubMed, Embase, and Cochrane Library databases. Studies reporting on the incidence of patellar resurfacing, revision rates, patient satisfaction, and relevant knee scores were included. Data from esteemed world registries such as the Australian Orthopaedic Association National Joint Replacement Registry, the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man and Danish Knee Arthroplasty Registry among others, were meticulously examined. Meta-analysis was employed to derive pooled estimates and 95% confidence intervals.

RESULTS

Analysis of data sourced from diverse world registries and literature sources unveiled significant disparities in the incidence of patellar resurfacing across different geographic regions and healthcare institutions. For instance, the incidence of routine patellar resurfacing ranged from 60% to 90% in some regions, while in others, it was as low as 30% to 50%. The meta-analysis indicated that routine resurfacing was associated with a lower revision rate of 3.5% (95%CI: 2.8%-4.2%) compared to non-resurfacing approaches, which exhibited a higher revision rate of 6.8% (95%CI: 5.5%-8.1%). Patient satisfaction outcomes showed variability, with routine resurfacing demonstrating higher mean satisfaction scores in functionality, pain relief, and stability categories.

CONCLUSION

The findings underscore the complexity of patellar resurfacing in knee arthroplasty and highlight the need for continued research to refine clinical practice. Future studies should prioritize prospective randomized controlled trials comparing different patellar resurfacing techniques using standardized outcome measures. Longitudinal studies with extended follow-up periods are necessary to evaluate the long-term outcomes and durability of various patellar resurfacing strategies. Collaborative efforts among multidisciplinary teams will be essential to conduct high-quality research that can provide actionable insights and improve patient outcomes.

Following the Anatomy of the Proximal Tibia With a Standard Anatomic Technique and the Use of an Asymmetrical Tibial Base Plate can Lead to a Mismatched Internal Components' Rotation in Mechanically Aligned Total Knee Arthroplasty

Background

Tibiofemoral components rotational congruency affects the total knee arthroplasty (TKA) success. The smart insert sensor (I-S) helps to establish tibial component rotation reciprocally to a fixed femoral rotation. We aimed (1) to validate the use of I-S as a possible tool to reach reproducible reciprocal femorotibial rotation (RftR) in TKA independently from anatomic landmarks, reducing outliers in combined and mismatched femorotibial rotation (CftR and MMftR, respectively) positioning and (2) to validate the "curve-on-curve" method for a specific type of asymmetrical tibial component.

Methods

From February 2018, we conducted a prospective case-control study including 106 patients undergoing TKA. Patients were divided into 2 groups based on the method used to establish tibial component rotation: with the I-S use (group A, n = 53) and with the standard "curve-on-curve" technique (group B, n = 53). Rotational alignment was calculated using the Berger protocol with postoperative computed tomography scanning. Alignment parameters measured were tibial and femoral component rotations (tR, fR), the CftR, the MMftR, and the RftR.

Results

Intraoperative rotation measured by I-S correlated the best with RftR (r = 0.84; P < .001) at the post-operative CT scanning. No significant differences were found between groups A and B regarding all types of rotation (fR: P = .774; tR: P = .467; CftR: P = .847) except for MMftR (P = .036) and RftR (P = .023). There were no outliers in group A but 27 and 12 outliers in group B for MMftR and CftR respectively (P < .001; P = .032).

Conclusions

The TKA components' rotation established using a smart I-S intraoperatively is ascribable to the RftR at postoperative computed tomography scan. The I-S helps reduce outliers in the CftR and MMftR. An asymmetrical tibial base plate implanted using the curve-on-curve technique does not create a neutral reciprocal femorotibial rotation significantly increasing the number of cases with mismatched femorotibial internal rotation.

The effect of different insert design congruencies on the kinematics of a mobile bearing TKA: A cadaveric study

Introduction

Total knee arthroplasty has proved to be a safe, effective and reproducible surgical treatment for patients with serious/advanced degenerative joint disease of the knee, but the optimal results after these implants can be achieved only if the joint kinematics and kinetics are carefully respected and not significantly altered after the replacement. In order to enhance the capability of matching the healthy configuration, therefore, different prosthesis models in terms of constraints and designs are available for the surgeons to choose among. As an example of this variety, mobile bearing models allow the surgeon to choose among different insert designs in terms of geometry and relative biomechanical approaches, with the relative performances depending on which one is adopted.This article aims to analyse the effect of different levels of congruency of mobile bearing inserts through an experimental activity performed on an ultra-congruent insert design, also referred as deep-dished.

Methods

The experimental activity followed the same protocol used in a previous study focused on the effect of symmetricity/asymmetricity (in order to allow a comparison among the results obtained), i.e. it analysed passive squat on 5 cadaveric knee specimens; internal-external rotations of femur and tibial insert respect to the tibia tray were thus measured via a motion capture system in order to compare the insert-femur relative rotation among the different congruency configurations.

Results

The overall knee kinematic (in terms of flexion-extension and internal-external rotation ranges of motion) with an ultra-congruent insert did not differ from the ones found for the other inserts; the insert-femur rotation values, instead, returned to be between the ones obtained with the other two inserts.

Conclusion

In terms of adaptability to tibio-femoral rotation, therefore, this insert represents a valid option for the surgeon seeking for an intermediate solution among the opposed approaches of the other two.

Experimental and clinical analysis of the use of asymmetric vs symmetric polyethylene inserts in a mobile bearing total knee arthroplasty

Purpose

This study compared the effects of symmetric and asymmetric designs for mobile bearing polyethylene insert for total knee arthroplasty (TKA), both clinically and biomechanically through experimental cadaver tests.

Methods

303 patients implanted with a mobile bearing TKA were retrospectively analyzed up to 2-year follow-up with relative scores. The same femoral and tibial components were used for all the patients; 151 patients received a Symmetric Design (SD) insert and 152 an Asymmetric Design (AD). A biomechanical experimental test was performed to improve the comprehension of the clinical results, analyzing passive squat on 5 cadaveric knee specimens: internal-external rotations of femur and tibial insert respect to the tibia tray were analyzed in native and implanted configurations (with both symmetrical and asymmetrical inserts for each specimen).

Results

After surgery, patients' average flexion improved from 105° (with preoperative extension deficit of 5°), to 115° (SD-group) and 120° (AD-group) at the 2-year follow-up. There was no postoperative extension deficit. AD-group presented better ability to perform certain routines and wasn't affected by any pain, while antero-lateral pain was reported in some SD-group patients. The experimental tests returned no statistically relevant difference in tibio-femoral flexion-extension and internal-external rotations among all the three configurations tested; a statistically significant difference is found for insert-tray internal-external rotations between SD and AD configurations; in details, the AD insert showed insert-tray angles comparable to the ones found for femoral component-tibial tray, while the SD insert returned lower angular values.

Conclusion

Clinically and biomechanically, an asymmetric mobile bearing insert could represent a valid alternative to symmetric mobile bearing insert.

Level of evidence

III, Case-control study Retrospective comparative study.

Asymmetric polyethylene inserts promote favorable kinematics and better clinical outcome compared to symmetric inserts in a mobile bearing total knee arthroplasty

PURPOSE

This study aims at comparing the effects of symmetric and asymmetric designs for the polyethylene insert currently available and also for mobile bearing total knee arthroplasty (TKA). The investigation was performed both clinically and biomechanically through finite element analysis.

METHODS

303 patients, with a mobile bearing TKA, were analyzed retrospectively. All patients received the same femoral and tibial components; for the insert, 151 patients received a symmetric design (SD) and 152 an asymmetric design (AD). Additionally, a 3D finite element model of a lower leg was developed, resurfaced with the same TKAs and analysed during gait and squat activities. TKA kinematics, and bone-stresses were investigated for the two insert solutions.

RESULTS

After surgery, patients' average flexion improved from 105°, with 5° of preoperative extension deficit, to 120° (AD-group) and 115° (SD-group) at the latest follow-up. There was no postoperative extension deficit. No pain affected the AD-group, while an antero-lateral pain was reported in some patients of the SD-group. Patients of the AD-group presented a better ability to perform certain physical routines. Biomechanically, the SD induced higher tibial-bone stresses than the AD. Both designs replicated similar kinematics, comparable to literature. However, SD rotates more on the tray, reducing the motion between femoral and polyethylene components, while AD permits greater insert rotation.

CONCLUSION

The biomechanical analysis justifies the clinical findings. TKA kinematics is similar for the two designs, although the asymmetric solution shows less bone stress, thus resulting as more suitable to be cemented, avoiding lift-off issues, inducing less pain. Clinically, and biomechanically, an asymmetric mobile bearing insert could be a valid alternative to symmetric mobile bearing insert.

LEVEL OF EVIDENCE

Case-control study retrospective comparative study, III.

Temporal patterns of commonly used clinical outcome scales during a 5-year period after total knee arthroplasty

Background

It is not established beyond doubt whether improvements in functional outcome after total knee arthroplasty (TKA) are maintained in the long term. We therefore investigated the temporal patterns of functional outcome [using range of motion (ROM), American Knee Society (AKS) score, Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and 36-Item Short Form Health Survey (SF-36) score] over a 5-year period after uncomplicated TKA, and whether these patterns differed by implant type and patient age.

Materials and methods

This prospective study evaluated 138 patients who underwent unilateral TKA with either a mobile-bearing (MB) or fixed-bearing (FB) posterior-stabilized prosthesis. An independent investigator evaluated the functional outcome at five time points: preoperatively and at 6-month, 1-year, 2-year, and 5-year follow-up. Differences in functional outcomes between adjacent time points were evaluated by mixed-effect model repeat measurement (MMRM).

Results

The different functional outcome scores showed improvement till 6 months–2 years, followed by a variable decline. In patients aged ≥ 68 years with an MB implant, most of the functional outcome scores declined between 2 and 5 years after variable initial improvement till 6 months–2 years, whereas the parameters plateaued after 2 years in those aged < 68 years and in older patients with an FB implant.

Conclusions

A decline in function and pain relief occurs 2 years after TKA. This decline is more evident in older patients with an MB prosthesis. Based on these findings, we believe that use of MB implants in older patients (≥ 68 years) requires further investigation.

Level of evidence

Level 3.

Mobility of the rotating platform in low contact stress knee arthroplasty is durable

PURPOSE

The mobile bearing or rotating platform (RP) in total knee arthroplasty (TKA) is originally part of a low contact stress (LCS) concept, with bearing undersurface mobility compensating higher bearing upper-surface congruency. The in vivo range of axial femorotibial rotation in RP knees has been the subject of many studies, but always involving the performance of relatively low demanding task conditions. Hardly any study has addressed the maintenance of this rotation over time.

METHODS

Two consecutive series of patients with LCS RP knees were studied in a cross-sectional study of 1- and 5-year follow-up. They were assessed using optoelectronic movement analysis during gait and the performance of a sit-to-walk (STW) task with and without turning steps.

RESULTS

A mean range of rotation (SD) was found in the 1-year group of 13.4° (3.7) during gait, 17.8° (6.8) during STW straight, and 17.9° (6.9) during STW with turning. The range in the 5-year group was 11.2° (6.0) during gait, 18.5° (8.7) during STW straight, and 18.3° (8.3) during STW with turning. A so-called paradoxical axial rotation pattern during gait and STW straight occurred in both groups in a normal prevalence.

CONCLUSION

The amount and pattern of rotation in a LCS RP knee does not become impaired between 1 and 5 years postoperatively. The theoretical benefit of RP TKA has not been proven in any clinical study so far, and studies with suitable long-term follow-up need to prove whether this mobility also leads to improved prosthesis survival. However, our findings support the functioning of the rotating platform at a basal science level and illustrate the need for the use of more complex tasks in kinematic studies.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

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.

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.

Mobile bearing and fixed bearing total knee arthroplasty

The mobile bearing (MB) concept in total knee arthroplasty (TKA) was developed as an alternative to fixed bearing (FB) implants in order to reduce wear and improve range of motion (ROM), especially focused on younger patients. Unfortunately, its theoretical advantages are still controversial. In this paper we exhibit a review of the more recent literature available comparing FB and MB designs in biomechanical and clinical aspects, including observational studies, clinical trials, national and international registries analyses, randomized controlled trials, meta-analyses and Cochrane reviews. Except for some minor aspects, none of the studies published so far has reported a significant improvement related to MBs regarding patient satisfaction, clinical, functional and radiological outcome or medium and long-term survivorship. Thus the presumed superiority of MBs over FBs appears largely inconsistent. The routine use of MB is not currently supported by adequate evidences; implant choice should be therefore made on the basis of other factors, including cost and surgeon experience.

Comparison of Tibial Insert Polyethylene Damage in Rotating Hinge and Highly Constrained Total Knee Arthroplasty: A Retrieval Analysis

This study compared the damage scores and damage patterns in 19 tibial inserts from rotating hinge (RH) implants with 19 inserts from highly constrained (HC) implants. Each insert was divided into 16 damage zones and each zone was subjectively graded from a scale of 0-3 for seven different damage modes. The overall damage scores were comparable for the two groups (RH: 64.1 ± 15.4; HC: 66.1 ± 29.0; P = 0.59). The HC group, however, had greater post damage (compared to the post-hole of RH) while the RH group had greater backside damage. The pattern of damage was also different, with burnishing and cold flow being more common in HC group while pitting, scratching and embedded debris were more common in the RH group.

Patient Reported Kneeling Ability in Fixed and Mobile Bearing Knee Arthroplasty

Kneeling is an important function of the knee joint required for many daily activities. Bearing type is thought to influence functional outcome following UKA and TKA. Self-reported kneeling ability was recorded in 471 UKA and 206 TKA patients with fixed or mobile bearing implants. Kneeling ability was recorded from the Oxford Knee Score question 7. The self-reported ability to kneel was similar in patients with fixed and mobile bearing UKA implants following surgery. In TKA, greater proportions of patients were able to kneel in the fixed compared to the mobile bearing groups up to two years after surgery indicating that self-reported kneeling ability is enhanced in fixed compared to mobile bearing TKA.

Mobile-bearing prosthesis and intraoperative gap balancing are not predictors of superior knee flexion: a prospective randomized study

PURPOSE

Range of motion is a crucial measure of the outcome of total knee arthroplasty. Gap balancing technique and mobile-bearing prosthesis can improve postoperative range of motion. The purpose of this study was to determine the factors that are predictive of the postoperative range of motion.

METHODS

A total of 94 knees with varus osteoarthritis were prospectively randomized to receive either a posterior-stabilized mobile-bearing or a posterior-stabilized fixed-bearing prosthesis. All preoperative and postoperative protocols and operative techniques were identical in the two groups. Extension and flexion joint gaps were measured using a tensor device during the operation. Multiple regression analysis was conducted to determine the best predictors of the knee flexion angle 2 years after the operation. The independent variables were type of prosthesis (mobile-bearing or fixed-bearing), difference between flexion and extension joint gaps (mm), age, gender, body mass index (BMI), preoperative and intraoperative knee flexion angles, change in posterior condylar offset, and posterior tilt of the tibial plateau.

RESULTS

The mean difference between flexion and extension joint gaps was 0.8 ± 1.3 (mean ± SD) mm for mobile-bearing and 0.8 ± 1.9 mm for fixed-bearing prosthesis. The mean flexion angle for mobile-bearing and fixed-bearing groups was 120 ± 16° and 116 ± 20° preoperatively (n.s.), 142 ± 9° and 141 ± 12° intraoperatively (n.s.), and 129 ± 10° and 128 ± 13° at 2 years postoperatively (p = 0.773), respectively. Predictors were identified in the following three categories: (1) preoperative flexion angle, (2) intraoperative radiographic flexion angle, and (3) BMI (R = 0.603, p < 0.001).

CONCLUSIONS

Mobile-bearing prosthesis and optimal gap balancing did not result in superior postoperative flexion angle. Better preoperative and intraoperative flexion angles and lower BMI were the significant predictors for better postoperative flexion angle.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Long-term data of gait characteristics and moment-knee angle relations in female total knee arthroplasty patients

BACKGROUND

Despite the clinical success of total knee arthroplasty, impaired gait patterns and quadriceps and hamstring maximal voluntary force production might persist years post-surgery. Long-term data of gait patterns and quadriceps and hamstring maximal force production are rarely published with total knee arthroplasty patients. This work examined gait characteristics and the moment-knee angle relations of the knee extensors and flexors about 10 years post-total knee arthroplasty.

METHODS

About a decade post-surgery, 10 female total knee arthroplasty patients (64 years, mobile-bearing inlay) and 10 age-matched female controls were examined. Sagittal plane kinematics in the hip and knee joint during treadmill walking at 2 kilometres per hour were recorded using motion analysis. Spatiotemporal gait parameters were analyzed at self-selected walking speeds with a pressure-platform. The unilateral isometric moment-knee angle relations of the knee extensors and flexors and the electromyographic knee angle relation of the quadriceps were studied using dynamometry. Due to group differences for body mass index values, univariate analysis of variance (main effect: group, secondary effect: body mass index) was used for statistical analysis.

FINDINGS

Total knee arthroplasty patients demonstrated significant (P<0.05) gait deficits during constant and self-selected walking speeds and lower average absolute values in the moment-knee angle relations of the knee extensors and flexors. Significant (P<0.05) lower body-mass-normalized knee extension moments were detected at all knee joint positions for the patients.

INTERPRETATION

Long-term impairments of gait characteristics and maximal voluntary force production, especially for the knee extensors, might persist after total knee arthroplasty.

No difference in clinical and radiologic outcomes after total knee arthroplasty with a new ultra-congruent mobile bearing system and rotating platform mobile bearing systems after minimum 5-year follow-up

We retrospectively compared the clinical and radiographic results between 76 primary total knee arthroplasties (TKAs) using the e.motion Ultra-Congruent prosthesis and 155 primary TKAs using the Low Contact Stress rotating platform. All patients had a minimum 5-year follow-up. Range of motion, Hospital for Special Surgery score, Knee Society Knee Score and Knee Society Functional Score significantly increased in both groups postoperatively, but there was no significant difference between the two groups. The mechanical femorotibial angle improved in both groups postoperatively. Coronal and sagittal component angles were well maintained at the final follow-up. This study demonstrates that a new mobile-bearing prosthesis, designed to be highly congruent with a rotating bearing, could be considered with theoretical advantages and comparable outcomes of established mobile-bearing prostheses.

The self-aligning knee prosthesis: clinical and radiological outcome and survival analysis of a cruciate retaining meniscal bearing knee at 10-year follow-up

PURPOSE

Previously, the clinical and radiological results of the self-aligning cruciate retaining total knee prosthesis at 5-years follow-up were described. The 10-year follow-up is now reported to determine the clinical and radiological results and the survival of the prosthesis.

METHODS

A 10-year follow-up was performed in this prospectively followed cohort of 246 (232 patients) self-aligning, cruciate retaining total knee arthroplasties performed between 1995 and 1998. Because patients had died and others suffered from comorbidities making them unable to attend a follow-up consultation, data could be obtained for 105 prostheses. Clinical results were evaluated by the Knee Society Score, and radiological follow-up was performed on standard AP and lateral X-rays. All radiographs were evaluated for the presence of radiolucencies, osteolysis and wear.

RESULTS

At the 10-year follow-up, there were no new cases of revision so that the cumulative survival rate at 10 years remains 95%. The 10-year follow-up shows good clinical results with an average Knee Society Score of 154 (SD 35.7) and an average range of motion of 109° (SD 13.7). After excluding 25 prostheses for comorbidities, the mean 10-year KSS score increased from 154 to 163 (SD 26.2). On the other hand, for the ROM, the exclusion of the 25 prostheses had no influence on the mean ROM value of 109°. At the 10-year follow-up, none of the 100 available radiographs showed any radiolucencies >2 mm on any component.

CONCLUSIONS

Long-term follow-up of the mobile bearing, cruciate retaining, SAL-II total knee arthroplasty shows excellent clinical and radiological results without bearing dislocation.

LEVEL OF EVIDENCE

Prospective cohort, Level IV.

The Rotaglide mobile-bearing total knee arthroplasty: no difference between cemented and hybrid implantation

PURPOSE

The optimal fixation of the Rotaglide total knee arthroplasty's (TKA) components is controversial. It is hypothesized that the hybrid fixation (cementless femoral component) in a mobile-bearing TKA system might cause increased rate of loosening--especially in the femoral part--and finally failure of the arthroplasty. Consequently, the aim of this study was to compare the survival and revision rates and also the clinical and radiological outcomes of the cemented and hybrid fixation of the Rotaglide TKA.

METHODS

One hundred patients, who underwent TKA with the Rotaglide prosthesis, were randomly placed in two groups. In the first group, the prosthesis was cemented, and in the second group, the hybrid technique was used. Revision and mortality rates were compared after 8-12 years of follow-up. Knee and Osteoarthritis Outcome Score (KOOS) questionnaire and the Knee Society Roentgenographic Evaluation and Scoring System were used to demonstrate clinical and radiographic differences.

RESULTS

There were no statistically significant differences in revision (n.s.) or mortality (n.s.) rates between the two treatment arms. The clinical outcome at the time of last follow-up (mean 9.5 years, SD ± 1.4) ranged from very good to excellent (77.8 ± 17.5 for the cemented group and 77.2 ± 20.4 for the hybrid group). No statistically significant differences in all KOOS subscales. Radiographs showed no significant difference in prosthesis alignment and no evidence of loosening between groups.

CONCLUSION

The hypothesis that the hybrid fixation in a mobile-bearing TKA system might cause increased rate of loosening and finally failure of the arthroplasty was not confirmed. The fixation technique (cemented or hybrid) had no influence on the prosthesis's survivorship, and also on mortality rates, clinical and radiographic outcomes in a mean follow-up time of 9.5 ± 1.4 years. The Rotaglide TKA is a safe and reliable prosthesis regardless the fixation technique.

Rotating-platform TKA no different from fixed-bearing TKA regarding survivorship or performance: a meta-analysis

BACKGROUND

Mobile bearings have been compared with fixed bearings used in TKA. However, rotating platforms, a specific type of mobile bearing, have not been compared with fixed-bearings using meta-analysis.

QUESTIONS/PURPOSES

We asked whether the performance of a rotating-platform bearing is superior to, comparable to, or worse than a fixed bearing. Four areas were investigated: clinical performance, component alignment, adverse event rates, and revision rates.

METHODS

Searches of Medline, EMBASE, Google Scholar, and the Cochrane databases, combined with reference lists from published meta-analyses and systematic reviews of mobile-bearing versus fixed-bearing prostheses used in TKAs, provided 17 nonlanguage-restricted studies consisting of 1910 TKAs (966 rotating platform versus 944 fixed bearing). Random-effect modeling was used for all meta-analyses, thereby mitigating possible effects of heterogeneity among studies. All meta-analyses were examined for publication bias using funnel plots; publication bias was not detected for any meta-analysis.

RESULTS

There were no statistically or clinically significant differences in clinical performance (clinical scores, ROM, and radiographic evaluation), component alignment, revision rates, or adverse event rates except for tibial component alignment in the AP plane, which favored TKA with fixed-bearings (p = 0.020; standardized mean difference, 0.229; 95% CI, 0.035-0.422), but the effect size was small enough that it was not considered clinically important.

CONCLUSIONS

Based on our findings, which agree substantially with those of prior systematic reviews of TKAs with mobile-bearing versus fixed-bearing prostheses, there is no compelling case for either rotating-platform or fixed-bearing implant design in terms of clinical performance, component alignment, adverse event frequencies, or survivorship. This dataset, which was limited to a maximum 6 years followup, is insufficient to address questions related to wear or late revisions. We therefore suggest that implant choice should be made on the basis of other factors, perhaps including cost or surgeon experience.

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.

The Advantage of a Total Knee Arthroplasty with Rotating Platform is Only Theoretical: Prospective Analysis of 1,152 Arthroplasties

Background:

The aim of total knee surgery is to provide patients with end-stage osteoarthritis of the knee with both pain relief and a functional range of motion with a securely fixed prosthesis for the long term. Many types of implants are designed to achieve these goals. Only clinical outcome studies are able to substantiate the superiority of one design over another. Our primary research question was to determine whether patients receiving a rotating platform implant had a better functional outcome.

Methods:

A total of 1,152 Performance Total Knee Arthroplastiesin 943 patients were studied prospectively. In 561 cases, the cruciate retaining model (CR) was used. In 591 cases the cruciate substituting with posterior-stabilized model (PS) was implanted (324 cases with a fixed bearing (PSFB) and 267 cases with a rotating platform (PSRP)).

Results:

The Clinical KSS score was similar for the three types at 1, 5, 10 and 15 years post-operatively. The Functional score also remained similar for all types until 10 years; at 15 years functional results of the CR group decreased.

Conclusions:

Neither clinically nor radiographically did the use of a rotating platform prove to be more advantageous than fixed bearing tibial components. Thus, the advantage of a Total Knee Arthroplasty with Rotating Platform remains theoretical.

Single-radius, multidirectional total knee replacement

PURPOSE

The present study was designed to evaluate the mid-term (5- to 8-year) survival rate of a new total knee replacement (TKR) with a single-radius femoral component and a multidirectional, highly congruent tibial component, in comparison with an historical group (TKR with multi-radius design and fixed bearing).

METHODS

Four hundred and thirty patients were included, of which 369 patients (86 %) completed the 5-year follow-up with Knee Society Score evaluation and radiograph examination (study group = 387, control group = 83).

RESULTS

There was a significant improvement for all analysed items between pre-operative status and late follow-up. Mean knee score was 93 ± 9 points in the study group and 88 ± 16 points in the control group (p < 0.001). Mean flexion angle was not different (118 ± 11 vs. 114 ± 13 degrees). Mean functional score was 87 ± 16 points in the study group and 71 ± 24 points in the control group (p < 0.001). Survival rate at 5-year follow-up was 98.8 % (vs. 98.0 %) for mechanical revisions only, and 96.4 % (vs. 98.1 %) for all revisions.

CONCLUSIONS

The new TKR allowed obtaining significantly better results than the fixed-bearing TKR. These results are in line with the best series published in the current literature, but there was no evidence of any superiority of this TKR against already published standards.

Femoro-tibial kinematics after TKA in fixed- and mobile-bearing knees in the sagittal plane

PURPOSE

Lack of the anterior cruciate ligament in total knee arthroplasty results in paradoxical movement of the femur as opposed to the tibia under deep flexion. Total knee arthroplasty with mobile-bearing inlays has been developed to provide increased physiological movement of the knee joint and to reduce polyethylene abrasion. The aim of this study was to perform an in vitro analysis of the kinematic movement in the sagittal plane in order to show differences between fixed- and mobile-bearing TKA in comparison with the natural knee joint.

METHODS

Seven knee joints of human cadaver material were used in a laboratory experiment. Fixed- and mobile-bearing inlays were tested in sequences under isokinetic extension in so-called kinemator for knee joints, which can simulate muscular traction power by the use of hydraulic cylinders, which crossover the knee joint. As a target parameter, the a.p. translation of the tibio-femoral relative movement was measured in the sagittal plane under ultrasound (Zebris) control.

RESULTS

The results show a reduced tibial a.p. translation in relation to the femur in the bearing group compared to the natural joint. In the Z-axis, between 110° and 50° of flexion, linear movement decreases towards caudal movement under extension. Admittedly, the study did not show differences in the movement pattern between "mobile-bearing" and "fixed-bearing" prostheses.

CONCLUSION

Results of this study cannot prove functional advantages of mobile-bearing prostheses for the knee joint kinematic after TKA. Both types of prostheses show typical kinematics of an anterior instability, hence they were incapable of performing physiological movement.

Survival rates and causes of revision in cemented primary total knee replacement: a report from the Norwegian Arthroplasty Register 1994-2009

We evaluated the rates of survival and cause of revision of seven different brands of cemented primary total knee replacement (TKR) in the Norwegian Arthroplasty Register during the years 1994 to 2009. Revision for any cause, including resurfacing of the patella, was the primary endpoint. Specific causes of revision were secondary outcomes. Three posterior cruciate-retaining (PCR) fixed modular-bearing TKRs, two fixed non-modular bearing PCR TKRs and two mobile-bearing posterior cruciate-sacrificing TKRs were investigated in a total of 17 782 primary TKRs. The median follow-up for the implants ranged from 1.8 to 6.9 years. Kaplan-Meier 10-year survival ranged from 89.5% to 95.3%. Cox's relative risk (RR) was calculated relative to the fixed modular-bearing Profix knee (the most frequently used TKR in Norway), and ranged from 1.1 to 2.6. The risk of revision for aseptic tibial loosening was higher in the mobile-bearing LCS Classic (RR 6.8 (95% confidence interval (CI) 3.8 to 12.1)), the LCS Complete (RR 7.7 (95% CI 4.1 to 14.4)), the fixed modular-bearing Duracon (RR 4.5 (95% CI 1.8 to 11.1)) and the fixed non-modular bearing AGC Universal TKR (RR 2.5 (95% CI 1.3 to 5.1)), compared with the Profix. These implants (except AGC Universal) also had an increased risk of revision for femoral loosening (RR 2.3 (95% CI 1.1 to 4.8), RR 3.7 (95% CI 1.6 to 8.9), and RR 3.4 (95% CI 1.1 to 11.0), respectively). These results suggest that aseptic loosening is related to design in TKR.

Comparison of fixed- and mobile-bearing total knee arthroplasty with a mean five-year follow-up: A meta-analysis

Controversy exists regarding the clinical and radiological differences in outcomes between fixed-bearing (FB) and mobile-bearing (MB) total knee arthroplasties (TKAs) at the mid- or long-term follow-up. We therefore conducted a meta-analysis and systematic review of randomized controlled trials (RCTs) that have evaluated FB and MB TKAs. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, Medline and Embase. The data, including demographic information, methodological quality, duration of follow-up, clinical and radiographical outcomes, patient preferences and complications, were extracted. The methodological quality of the studies was assessed in accordance with the guidelines presented in the Cochrane Handbook for Systematic Reviews of Interventions. Nine trials, studying 1,821 knees, were eligible for data extraction and meta-analysis. The Knee Society score and the maximum knee flexion demonstrated no difference between the FB and MB groups (P=0.47 and P=0.72, respectively). Similarly, no difference was revealed between the groups for radiological outcomes or general health results. An increased number of high-quality RCTs with long-term follow-ups are required to validate the results.

Rotating-platform has no surface damage advantage over fixed-bearing TKA

BACKGROUND

Rotating-platform TKA, although purported to have superior kinematics, has shown no clinical advantages over those of fixed-bearing TKA. Our design-matched retrieval study aimed to investigate if differences in bearing wear damage exist between fixed- and mobile-bearing TKAs with similar condylar geometry.

QUESTIONS/PURPOSES

We asked whether (1) the rotating platform's more conforming tibiofemoral articulation would be associated with less severe damage; (2) the location of damage and wear would be similar on the tibiofemoral or backside surfaces of two contemporary designs with similar condylar geometry; and (3) the combined damage and deformation measured as thickness would differ between the two designs.

METHODS

We performed damage grading and damage mapping on 25 rotating-platform and 17 fixed-bearing inserts. The patient demographic data from each of these cohorts were comparable. Inserts were also laser-scanned from which we obtained thicknesses, and inferior surface three-dimensional scans, from which we determined dimensional changes.

RESULTS

Rotating-platform and fixed-bearing inserts had similar tibiofemoral damage scores. However, the scores on the inferior surface of rotating platforms were greater, often as a result of third-body debris scratching observed on both damage mapping and three-dimensional scans. The extent of damage as a function of surface area was greater for rotating platforms, consistent with the greater tibiofemoral conformity. Dimensional changes on the inferior surfaces of the fixed bearing followed loading areas of the knee. However, no differences were seen in the thicknesses between fixed- and rotating-platform bearings.

CONCLUSIONS

The increased total damage score on the rotating platform, coupled with increased surface area damaged and the propensity for third-body debris, indicates no damage advantage to this mobile-bearing design.

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.

Tibial component designs in primary total knee arthroplasty: should we reconsider all-polyethylene component?

PURPOSE

Despite the frequency with which total knee arthroplasties (TKAs) are performed, whether they are best performed using all-polyethylene or metal-backed tibial components remains a controversy. The aim of the present study was to determine the advantages and disadvantages of metal-backed compared with all-polyethylene tibial components during TKAs through an evaluation of current literature.

METHODS

A meta-analysis and systematic review of randomized and non-randomized comparative studies comparing metal-backed with all-polyethylene tibial components during TKAs were performed. The focus of the analysis was on the outcomes of knee score, range of motion (ROM), quality of life, implant alignment, tibial migration, radiolucent line, complication, reoperation, and implant survivorship.

RESULTS

A total of 10 randomized/quasi-randomized controlled trials and 13 non-randomized comparative studies assessing 19,767 TKAs were eligible. On the basis of these studies, no significant differences were found between the 2 groups with regard to knee score, ROM, quality of life, complication, and reoperation. The findings indicated that using all-polyethylene tibial components is associated with lower continuous migration rate compared with metal-backed tibial components. Only 13 studies provided adequate data on implant survivorship during intermediate or long-term follow-up. Of these, 9 found that no statistical significance existed between the 2 groups. The other 3 studies found that using all-polyethylene components yielded a higher survival rate than using metal-backed components.

CONCLUSIONS

Metal-backed tibial components had no obvious advantages over all-polyethylene tibial components in TKAs. However, this finding should be interpreted with caution due to publication bias, low methodological quality of the included studies, and different surgical interventions.

LEVEL OF EVIDENCE

Therapeutic study (systematic review and meta-analysis), Level III.

Kinematics and early migration in single-radius mobile- and fixed-bearing total knee prostheses

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.

The outcome of rotating-platform total knee arthroplasty with cement at a minimum of ten years of follow-up

BACKGROUND

Durable, long-term results have been reported for patients managed with first-generation mobile-bearing total knee arthroplasty. Second-generation mobile-bearing total knee arthroplasty has been introduced to enhance instrumentation, to increase flexion, and to improve functional outcome, but, to our knowledge, no long-term results are available.

METHODS

From May 1999 to June 2000, 116 consecutive rotating-platform total knee arthroplasties were performed by the two senior authors in 112 patients with use of the LPS-Flex Mobile cemented prosthesis, which was implanted with a measured resection technique. The patella was resurfaced in every knee. The average age of the patients at the time of surgery was sixty-nine years (range, thirty-seven to eighty-five years), and seventy-seven patients (eighty knees) were women. The predominant diagnosis was osteoarthritis. The clinical and radiographic evaluation was performed with use of the Knee Society rating system. The level of activity and patient-reported functional outcome were evaluated with use of the University of California at Los Angeles (UCLA) score and the Knee injury and Osteoarthritis Outcome Score (KOOS), respectively.

RESULTS

The average duration of follow-up was 10.6 years (range, ten to 11.8 years). Three patients were lost to follow-up, and five patients died of causes unrelated to knee arthroplasty. Two knees were revised, one because of infection and one because of failure of the medial collateral ligament. Kaplan-Meier survivorship analysis showed an implant survival rate of 98.3% at ten years. For the 104 patients (108 knees) who were evaluated at a minimum of ten years, the average Knee Society knee and function scores improved from 34 to 94 points and from 55 to 88 points, respectively, at the time of the latest follow-up. There was no periprosthetic osteolysis and no evidence of implant loosening on follow-up radiographs. The average knee flexion was 117° preoperatively and 128° at the time of the latest follow-up evaluation. At the time of the latest follow-up, the KOOS quality-of-life score was significantly better for patients with >125° of flexion (p = 0.00034).

CONCLUSIONS

This study demonstrated durable clinical and radiographic results at a minimum of ten years after total knee replacement with a second-generation, cemented, rotating-platform, posterior-stabilized total knee prosthesis. According to the functional outcome results obtained in this study, we believe that this design is a valuable option for active patients undergoing total knee arthroplasty.

Early clinical results of a high-flexion, posterior-stabilized, mobile-bearing total knee arthroplasty: a US investigational device exemption trial

Between May 2001 and June 2004, 388 total knee arthroplasty cases were enrolled in a prospective, randomized, multicenter investigational device exemption trial. Patients received either the investigational high-flexion mobile-bearing knee or a fixed-bearing control. At 2 to 4 years of follow-up, results in 293 patients with degenerative joint disease were compared using Knee Society Assessment and Function scores, radiographic results, complications analysis, and survival estimates. The mobile-bearing and fixed-bearing groups demonstrated similar, significant improvement over preoperative assessments in Knee Scores, maximum flexion, and range of motion. One mobile-bearing arthroplasty required revision. Radiographic results were unremarkable, and implant-related complications were rare in both groups. At this early follow-up, the investigational high-flexion mobile-bearing knee and its fixed-bearing counterpart demonstrated comparable, effective performance.

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.

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.

Wear damage in mobile-bearing TKA is as severe as that in fixed-bearing TKA

BACKGROUND

Mobile-bearing TKAs reportedly have no clinical superiority over fixed-bearing TKAs, but a potential benefit is improved polyethylene wear behavior.

QUESTIONS/PURPOSES

We asked whether extent of damage and wear patterns would be less severe on retrieved mobile-bearing TKAs than on fixed-bearing TKAs and if correlations with patient demographics could explain differences in extent or locations of damage.

METHODS

We performed damage grading and mapping of 48 mobile-bearing TKAs retrieved due to osteolysis/loosening, infection, stiffness, instability or malpositioning. Visual grading used stereomicroscopy to identify damage, and a grade was assigned based on extent and severity. Each damage mode was then mapped onto a photograph of the implant surface, and the area affected was calculated.

RESULTS

Marked wear damage occurred on both surfaces, with burnishing, scratching, and pitting the dominant modes. Damage occurred over a large portion of both surfaces, exceeding the available articular borders in nearly 30% of implants. Wear of mobile-bearing surfaces included marked third-body debris. Damage on tibiofemoral and mobile-bearing surfaces was not correlated with patient BMI or component alignment. Damage on mobile-bearing surfaces was positively correlated with length of implantation and was greater in implants removed for osteolysis or instability than in those removed for stiffness or infection.

CONCLUSIONS

Each bearing surface in mobile-bearing implants was damaged to an extent similar to that in fixed-bearing implants, making the combined damage score higher than that for fixed-bearing implants. Mobile-bearing TKAs did not improve wear damage, providing another argument against the superiority of these implants over fixed-bearing implants.