Mobile-bearing total knee arthroplasty: a meta-analysis

Mid-term survivorship and clinical outcomes of revision knee arthroplasty using a mobile bearing tibial tray: A single-center registry review

BACKGROUND

Revision total knee arthroplasty can successfully restore function and relieve pain for patients with failed knee replacements. Mobile-bearing implants were designed to provide greater congruency between the implant and the polyethylene insert. The goal of this study was to review the clinical outcomes and survivorship for a revision mobile-bearing tibial design.

METHODS

A retrospective outcomes review was conducted to assess survivorship and clinical outcomes for a mobile bearing tibial tray, used with metaphyseal sleeves, in revision total knee arthroplasty.

RESULTS

At time of furthest follow-up, KM estimates (95% CI; n with further follow-up) for all-cause revision were 82.5% (75.8%; 87.5%; 42) at 7 years for the clinical assumption (CA), and 88.5% (84.4%,91.6%; 53) at 13 years for the registry assumption (RA). For revision of the tray as the endpoint, survivorship estimates were 93.4% (87.0%,96.7%; 42) at 7 years for CA, and 96.2% (93.2%,97.9%; 53) at 13 years for RA.

CONCLUSION

In this single-center registry evaluation, we found excellent mid-term survivorship and clinical outcomes for a mobile-bearing tibial tray used with metaphyseal sleeves in revision total knee arthroplasty.

Long-term clinical and radiological outcome of a cementless titanium-coated total knee arthroplasty system

INTRODUCTION

To ensure a high-quality standard, it is important to frequently evaluate different prostheses models to avoid prostheses with high failure rates. Thus, the aim of the study was to evaluate the long-term outcome of the uncemented titanium-coated total knee arthroplasty (TKA) system (Advanced Coated System (ACS) III, Implantcast, GERMANY). We hypothesized that the ACS III would have a similar performance as other cemented TKA systems.

MATERIALS AND METHODS

A total of 540 ACS III mobile-bearing knee joint prostheses were implanted in 495 patients. The visual analogue scale (VAS) score, Tegner activity score (TAS), knee society score (KSS), Western Ontario and McMaster (WOMAC) score, and the Short Form 12 (SF-12) score for the evaluation of quality of life (QoL) were taken after at least 9 years of follow-up. In addition, we measured range of motion (ROM) and assessed potential sex differences. In addition, the survival analysis was calculated at a median follow-up of 16.7 years.

RESULTS

At the final follow-up, 142 patients had died, and 38 had been lost to follow-up. The rate of revision-free implant survival at 16.7 years was 90.0% (95% CI 87.1-92.2%) and the rate of infection-free survival was 97.0% (IQR 95.2-98.2%). The reasons for revision surgery were aseptic loosening (32.9%), followed by infection (27.1%), inlay exchange (15.9%), and periprosthetic fractures (5.7%). At the clinical follow-up visit, the mean VAS score was 1.9 ± 1.9, the median TAS was 3 (IQR 2-4), and the mean KSS for pain and function were 83.5 ± 15.3 and 67.5 ± 25.2, respectively. The mean WOMAC score was 81.1 ± 14.9, and the median SF-12 scores for physical and mental health were 36.9 (IQR 29.8-45.1) and 55.8 (IQR 46.2-61.0), respectively. The mean knee flexion was 102.0° ± 15.4°. Male patients had better clinical outcome scores than female patients [SF-12 mental health score, p = 0.037; SF-12 physical health score, p = 0.032; KSS pain score (p < 0.001), and KSS functional score (p < 0.001)].

CONCLUSION

The ACS III TKA system is a suitable option for the treatment of end-stage osteoarthritis of the knee joint because of its adequate long-term survival. Our findings are in line with published data on similar TKA systems that have shown favourable clinical scores in males.

LEVEL OF EVIDENCE

Level III-Retrospective cohort study.

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.

The Outcome of Posterior-Stabilized, Rotating Platform Total Knee Arthroplasty at a Minimum Ten-Year Follow-Up, a Middle East Institution Experience

Posterior-stabilized, rotating platform knee prosthesis design was aimed to decrease polyethylene wear for the sake of improving implant survivorship. The purpose of the present prospective study was to evaluate the long-term clinical and radiographic results as well as the survival rate after using a rotating platform, posterior-stabilized knee prosthesis at a minimum of 10 years at a Middle East institution. We compared the results with reports in the literature on western populations. From January 2002 to June 2008, 96 patients (106 knees) underwent total knee arthroplasty (TKA) using a cemented rotating platform posterior-stabilized knee prosthesis. At a mean of 11.5 ± 1.3 years, 85 patients (95 TKAs) were available for clinical, radiographic, and implant survival analysis. At the final follow-up, 78.9% of the patients had excellent Knee Society Scoring system score, the average knee flexion was 110 ± 17 degrees, the average anatomical knee coronal alignment was 186 ± 2 degrees and 187 ± 3 degrees for varus and valgus knees, respectively. Five (5.2%) knees were revised of these: two for bearing dislocation, two for aseptic loosening, and one for infection. The Kaplan-Meier survival rate was 94.7% for all revisions and 97.8% when only revision for aseptic loosening considered as the end point. At a long-term follow-up, reasonable clinical and radiographic outcomes had been achieved after using a rotating platform, posterior-stabilized knee prosthesis in our population with acceptable survival rate reaching up to 95%, which is comparable to reports from the western population.

Trends in Polyethylene Design and Manufacturing Characteristics for Total Knee Arthroplasty: An Analysis From the American Joint Replacement Registry

BACKGROUND

Advances in polyethylene bearing characteristics have led to various options for total knee arthroplasty. We examine trends in use of polyethylene in the United States.

METHODS

An analysis of American Joint Replacement Registry data from 2012 to 2019 for primary total knee arthroplasty procedures was conducted. Design and manufacturing characteristics were obtained and validated in the American Joint Replacement Registry dataset. Polyethylene bearing design and manufacturing use characteristics were compared by year, gender, age group, and geographic region of the procedure. Descriptive analysis was performed.

RESULTS

We identified 993,292 cases over the study period. In total, 791,233 (80%) cases had complete device data available and were included in analysis. In addition, 366,280 (49.4%) cases utilized minimally stabilized bearings compared to 374,809 (50.6%) for posterior-stabilized bearings. Posterior-stabilized use was stable over the study period and highest in the Northeast (64.5%; P < .0001). Cruciate-retaining use decreased from 29.7% to 20.2% and anterior-stabilized use increased from 17.4% to 25.2%. Conventional polyethylene use decreased from 42.8% to 21.9%, and was highest in the 81+ age group (37.8%; P < .0001) and Northeast (43.0%; P < .0001). Highly cross-linked polyethylene (HXLPE) with antioxidant use increased from 9.08% to 31.8%, while HXLPE without antioxidant use remained constant.

CONCLUSION

There was an increase in use of anterior-stabilized and pivot bearings and an increase in use of HXLPE with antioxidant. Additionally, there were noted age group and regional differences in the use of various bearings. Further study should evaluate if these changing utilization trends are related to clinical outcomes, or due to regional training, preferences, or manufacturer pressures.

LEVEL OF EVIDENCE

Level III, retrospective.

Mobile-bearing versus fixed-bearing total knee arthroplasty: a meta-analysis of randomized controlled trials

Objective

The purpose of this study was to perform a meta-analysis comparing mobile-bearing with fixed-bearing total knee arthroplasty (TKA) in terms of all-cause revision rates, aspetic loosening, knee functional scores, range of motion and radiographic lucent lines and osteolysis.

Methods

PubMed, Cochrane Library, Google Scholar and Web of Science were searched up to January 2020. Randomized controlled trials that compared primary mobile-bearing with fixed-bearing TKA, reporting at least one of the outcomes of interest, at a minimum follow-up of 12 months were included. All outcomes of interest were pooled at short-term (< 5 years), mid-term (5 to 9 years) and long-term (> = 10 years) follow-up intervals.

Results

A total of 70 eligible articles were included in the qualitative and statistical analyses. There was no difference between mobile-bearing or fixed-bearing TKA at short-term, mid-term and long-term follow-ups in all outcome measures including all-cause revision rate, aseptic loosening, oxford knee score, knee society score, Hospital for Special Surgery score, maximum knee flexion, radiographic lucent lines and radiographic osteolysis.

Conclusion

The current level of evidence demonstrated that both mobile-bearing and fixed-bearing designs achieved excellent outcomes, yet it does not prove the theoretical advantages of the mobile-bearing insert over its fixed-bearing counterpart. The use of either design could therefore be supported based on the outcomes assessed in this study.

Level of Evidence: Level II, Therapeutic

Supplementary information

The online version contains supplementary material available at (10.1007/s00590-021-02999-x).

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.

Why are patients dissatisfied following a total knee replacement? A systematic review

BACKGROUND

Although total knee replacement (TKR) is an effective intervention for end-stage arthritis of the knee, a significant number of patients remain dissatisfied following this procedure. Our aim was to identify and assess the factors affecting patient satisfaction following a TKR.

MATERIALS AND METHODS

In accordance with the PRISMA guidelines, two reviewers searched the online databases for literature describing factors affecting patient satisfaction following a TKR. The research question and eligibility criteria were established a priori. Any clinical outcome study that described factors relating to overall satisfaction after primary TKR was included. Quality assessment for the included studies was performed by two accredited orthopaedic surgeons experienced in clinical research.

RESULTS

The systematic review identified 181 relevant articles in total. A history of mental health problems was the most frequently reported factor affecting patient satisfaction (13 reportings). When the results of the quality assessment were taken into consideration, a negative history of mental health problems, use of a mobile-bearing insert, patellar resurfacing, severe pre-operative radiological degenerative change, negative history of low back pain, no/less post-operative pain, good post-operative physical function and pre-operative expectations being met were considered to be important factors leading to better patient satisfaction following a TKR.

CONCLUSION

Surgeons performing a TKR should take these factors into consideration prior to deciding whether a patient is suitable for a TKR. Secondarily, a detailed explanation of these factors should form part of the process of informed consent to achieve better patient satisfaction following TKR. There is a great need for a unified approach to assessing satisfaction following a TKR and also the time at which satisfaction is assessed.

Minimum twelve-year follow-up of fixed- vs mobile-bearing total knee arthroplasty: Double blinded randomized trial

BACKGROUND

Total knee arthroplasty (TKA) with fixed-bearing (FB) implants have demonstrated impressive functional results and survival rates. Meanwhile, rotating-platform (RP) constructs have biomechanically shown to reduce polyethylene wear, lower the risk of component loosening, and better replicate anatomic knee motion. There is growing question of the clinical impact these design changes have long-term.Questions/purposes: The aim of this double-blinded prospective randomized trial was to compare function and implant survival in patients who received either FB or RP press-fit condylar Sigma (PFC Sigma, DePuy, Warsaw, IN) total knee replacements at a minimum follow-up of twelve years.

PATIENTS AND METHODS

Patient reported outcome measures used included the functional Knee Society Score, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) scores, Medical Outcomes Short Form-36 (SF-36) score, and satisfaction assessment on a four-point Likert scale. The data was collected from times preoperative, two-years, and final encounter (mean 13.95 years). A total of 28 RP and 19 FB knees (58.8%) were analyzed at the final follow-up.

RESULTS

Among all patients, KSS and WOMAC scores statistically improved from pre-op to 2-year, while KSS statistically worsened from 2-year to final follow-up. The RP group averaged better follow-up scores in all assessments at the final follow-up with exception of overall satisfaction. There was no statistically significant difference in the functional Knee Society Score, Short Form-36, WOMAC scores, patient satisfaction or implant survival between the two groups at any measured period.

CONCLUSIONS

The use of a fixed-bearing or rotating-platform design does not convey significant superiority in terms of function or implant longevity at a minimum twelve years after total knee arthroplasty.

LEVEL OF EVIDENCE

Level I, Experimental study, randomized controlled trial (RCT).

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.

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.

Posterior-stabilized inserts are preferable to cruciate-substituting ultracongruent inserts due to more favourable kinematics and stability

PURPOSE

It is unknown whether the conforming superiority of ultracongruent (UC) inserts over posterior stabilized (PS) inserts, due to an increased anterior lip for prevention of anterior displacement of the condyles during knee flexion, leads to better knee scores or greater knee stability in arthroplasty patients. This meta-analysis compared clinical outcomes, intraoperative kinematics, sagittal stability, and range of motion (ROM) between groups with either UC or PS inserts in primary total knee arthroplasty (TKA).

METHODS

Studies that recorded clinical outcomes, intraoperative kinematics, sagittal stability, and ROM in patients who underwent primary TKA with UC or PS inserts were included in the meta-analysis. Subgroup analyses based on differences in flexion angles were performed for intraoperative kinematics.

RESULTS

Thirteen studies met the criteria for inclusion in the meta-analysis. The UC and PS insert groups reported similar pain scores (95% CI - 0.15 to 0.16; n.s.) and function scores (95% CI - 0.30 to 0.14; n.s.). In contrast, femoral rotation during flexion (95% CI - 0.06 to 6.35; p = 0.05), posterior femoral translation during flexion (95% CI - 2.74 to - 0.15; p = 0.03), tibial sagittal laxity at 90° (95% CI 2.91 to 7.72; p < 0.0001), and ROM (95% CI - 4.84 to - 1.53; p = 0.0002) differed significantly between the groups. Subgroup analyses revealed that the pooled data for femoral rotation were significantly different between groups: 60°, 4.09 (p < 0.00001); 90°, 7.94 (p < 0.00001); and 120°, 8.16 (p < 0.00001). Furthermore, pooled data for posterior femoral translation were significantly different between groups: 90°, - 3.70 (p < 0.00001); and 120°, - 3.96 (p < 0.00001).

CONCLUSIONS

There were no significant differences in clinical outcomes between the groups with UC and PS inserts. However, the UC insert group showed significantly greater external femoral rotation, less posterior femoral translation, greater tibial laxity in the sagittal plane, and less ROM than the PS insert group. Based on the results of the current meta-analysis, in substituting the PCL, PS inserts are preferable to UC inserts due to more favourable kinematics and stability, even though both inserts have equivalent clinical outcomes.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

A randomized controlled trial of fixed- versus mobile-bearing total knee arthroplasty: a follow-up at a mean of ten years

Aims

It has been suggested that mobile-bearing total knee arthroplasty (TKA) might lead to better outcomes by accommodating some femorotibial rotational mismatch, thereby reducing contact stresses and polyethylene wear. The aim of this study was to determine whether there is a difference between fixed- and mobile-bearing versions of a contemporary TKA with respect to durability, range of movement (ROM) and function, ten years postoperatively.

Patients and Methods

A total of 240 patients who were enrolled in this randomized controlled trial (RCT) underwent a primary cemented TKA with one of three tibial components (all-polyethylene fixed-bearing, modular metal-backed fixed-bearing and mobile-bearing). Patients were reviewed at a median follow-up of ten years (IQR 9.2 to 10.4).

Results

There was no difference in durability, as measured by survivorship free of revision for any reason, nor in mean maximal ROM at ten years (p = 0.8). There was also no difference in function, as measured by Knee Society (KS) function scores (p = 0.63) or the prevalence of patellar tilt (p = 0.12).

Conclusion

In this clinical RCT, the mobile-bearing design of TKA was found to be reliable and durable, but did not provide better maximum knee flexion, function or durability ten years postoperatively compared with a posterior-stabilized, fixed-bearing design incorporating either an all-polyethylene or a modular-metal-backed tibial component. Cite this article: Bone Joint J 2018;100-B:925-9.

A prospective evaluation of a largely cementless total knee arthroplasty cohort without patellar resurfacing: 10-year outcomes and survivorship

BACKGROUND

The theoretical benefits of a mobile bearing design in Total Knee Arthroplasty (TKA) include increased articular surface conformity with a reduction in both polyethylene wear and implant interface shear. However, to date these theoretical advantages have not been translated into published evidence of superior survivorship. This paper presents the results of a prospective, non-comparative study evaluating the performance of the mobile bearing Low Contact Stress LCS Complete Rotating Platform TKA in a largely cementless cohort without patellar resurfacing.

METHODS

237 consecutive patients (240 knees) undergoing primary TKA were prospectively recruited. All received the LCS Complete Rotating Platform TKA (DePuy International, Leeds, UK). Clinical and radiographic assessments were performed at 3, 12, 60 and 120 months post-operatively. Radiographic evaluation was performed by an independent external surgeon.

RESULTS

The mean age was 70.3 years. 77.5% of cases were cementless. Radiographic assessment suggested excellent femoral component fixation. 22 tibial radiolucent lines (RLLs) > 1 mm were observed in 12 knees. No RLLs were progressive. There have been two revisions; one for late infection and one for aseptic loosening. No patients underwent secondary patellar resurfacing. The cumulative implant survivorship, using component revision for any reason as the endpoint, was 98.9% (95% CI, 95.6 to 99.7%) at 10 years.

CONCLUSIONS

The excellent survivorship at a minimum 10-year follow-up supports the use of uncemented porous coated fixation without patellar resurfacing with the non-posterior stabilized LCS Complete Rotating Platform TKA.

Superior long-term survival for fixed bearing compared with mobile bearing in ligament-balanced total knee arthroplasty

PURPOSE

Only few long-term data on ligament-balanced cruciate-retaining total knee arthroplasty (CR TKA) are currently available. Either a mobile- or fixed-bearing insert can be chosen, which showed good mid-term outcome and few complications and revisions. This multi-centre retrospective cross-sectional cohort study investigated the 12-year results of primary TKA using a balancing gap technique and compared survival and clinical outcome between fixed and mobile inserts.

METHODS

In this retrospective cross-sectional cohort study, 557 cases of three clinics (2 Swiss, 1 Dutch) operated between 1998 and 2003 with the first series of a TKA implanted with a balanced gap technique (433 (77.7%) fixed, 124 (22.3%) mobile (anterior-posterior gliding (7-9 mm) and rotational (15°) degrees of freedom) inserts) were included for survival analysis (Kaplan-Meier, by insert type). At the 12-year follow-up (FU) examination of 189 cases, range of motion, knee society score (KSS), numeric rating scale (NRS) for pain and satisfaction were determined and radiographs were evaluated by median tests, by insert type.

RESULTS

Of 521 cases available for analysis, 28 (5.4%; 11 fixed, 17 mobile bearing) were revised. Mean cumulative survival after 12.4 years was 97.0% (95% CI 94.7-98.4) for fixed bearings and 85.4% (95% CI 77.5-90.7) after 12.2 years for mobile bearings, p < 0.0001. Patients' mean age at 11.0 years FU (n = 189) was 78.0 (range 54.5-97.3) years. Mean total KSS was 157.8 (24-200) points, and mean passive flexion was 114° (45-150); no clinical score differed significantly between fixed and mobile bearings.

CONCLUSION

This study showed a superior survival for fixed bearing compared with mobile bearing in a CR TKA using a ligament-balanced technique after more than 12 years. Clinical outcomes are excellent to good after long-term follow-up, and similar for fixed and mobile bearing.

LEVEL OF EVIDENCE

Therapeutic studies-retrospective cohort study, Level III.

Spinout/Dislocation in Mobile-Bearing Total Knee Arthroplasty: A Report of 26 Cases

BACKGROUND

Excellent medium-term to long-term results for function and survivorship have been shown with mobile-bearing (MB) total knee arthroplasty (TKA). One of the key arguments against its use is the risk of "spinout" or dislocation of the MB. The aim of this study is to discuss the etiology, prevention, incidence, management, and outcome of spinout.

METHODS

Between October 1993 and February 2016, 8373 consecutive primary MB TKAs were performed irrespective of preoperative deformity. Before 2001, soft-tissue knee balancing was achieved by release of collateral ligaments and all spinouts were treated by open reduction. Thereafter, soft-tissue balancing was achieved without ligament release and with the use of a higher conformity MB and all spinouts were reduced closed, giving 2 comparative cohorts.

RESULTS

Twenty-six spinouts occurred in 8373 (0.31%) patients. In the first cohort up until May 2001, there were 14 spinouts of 2379 (0.58%) cases. There were 12 in cohort 2, in those patients having surgery after May 2001, thus giving an incidence of 12 of 5994 (0.2%), which was significantly lower than in cohort 1 (P < .01). Spinout was associated with the valgus knee (P < .01) and most (73%) occurred within the first 6 months. There was 1 arthrodesis in cohort 1 and 1 both-component revision in cohort 2.

CONCLUSION

The etiology of spinout is flexion gap instability. It can normally be reduced closed with recurrence being uncommon. Focus on soft-tissue balance necessary with an MB TKA can reduce the incidence of revision for instability as compared to a fixed-bearing TKA. Therefore, the risk of spinout should not be used as an argument against the MB TKA.

No difference in terms of radiostereometric analysis between fixed- and mobile-bearing total knee arthroplasty: a randomized, single-blind, controlled trial

PURPOSE

A concern that arises with any new prosthesis is whether it will achieve satisfactory long-term implant stability. The gold standard of assessing the quality of fixation in a new or relatively new implant is to undertake a randomized controlled trial using radiostereometric analysis. It was hypothesized that both mobile-bearing total knee arthroplasty and fixed-bearing total knee arthroplasty have comparable migration patterns at 2-year follow-up. This study investigated two types of cemented total knee arthroplasty, the mobile- or fixed-bearing variant from the same family with use of radiostereometric analysis.

METHODS

This prospective, patient-blinded, randomized, controlled trial was designed to investigate early migration of the tibia component after two years of follow-up with use of radiostereometric analysis. A total of 50 patients were randomized to receive a mobile- or fixed-bearing TKA from the same family. Patients were evaluated during 2-year follow-up, including radiostereometric analysis, physical and clinical examination and patient reported outcome measures (PROMs).

RESULTS

At two-year follow-up, the mean (±SD) maximum total point motion (MTPM) in the fixed-bearing group was 0.82 (±1.16) versus 0.92 mm (±0.64) in the mobile-bearing group (p = n.s) with the largest migration seen during the first 6 weeks (0.45 ± 0.32 vs. 0.54 ± 0.30). The clinical outcome and PROMs significantly improved within each group, not between both groups.

CONCLUSIONS

Measuring early micromotion is useful for predicting clinical loosening that can lead to revision. The results of this study demonstrate that early migration of the mobile-bearing is similar to that of the fixed-bearing component at two years and was mainly seen in the first weeks after implantation.

LEVEL OF EVIDENCE

Randomized, single-blind, controlled trial, Level I.

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.

Comparison of fixed and mobile-bearing total knee arthroplasty in terms of patellofemoral pain and function: a prospective, randomised, controlled trial

BACKGROUND

Despite growing evidence in the literature, there is still a lack of consensus regarding the use of the mobile-bearing (MB) design total knee arthroplasty (TKA).

METHODS

In a prospective, comparative, randomised, single centre trial, 106 patients with end-stage osteoarthritis of the knee were randomised to either an MB or fixed-bearing (FB) group to receive posterior stabilised (PS)-TKA using a standard medial parapatellar approach and patellar resurfacing with follow-up (FU) for 5 years. The primary outcome was anterior knee pain (AKP) during the chair rise test and the stair climb test 5 years after surgery. The secondary outcome was the ability to rise from a chair and to climb stairs, range of motion (ROM), Knee Society Score (KSS), RAND-36 scores and radiological analysis of the patellar tilt.

RESULTS

No statistically significant difference was found between the two groups at 5 years FU in terms of median AKP during the chair rise test and the stair climb test (p = 0.5 and p = 0.8, respectively). There was no significant difference in any of the other secondary outcome parameters between the groups at 5 years FU.

CONCLUSION

A mobile-bearing TKA does not decrease AKP compared to fixed bearings.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT02892838 .

LEVEL OF EVIDENCE

II.

Are Midterm Patient-Reported Outcome Measures Between Rotating-Platform Mobile-Bearing Prosthesis and Medial-Pivot Prosthesis Different? A Minimum of 5-Year Follow-Up Study

BACKGROUND

Both rotating-platform (RP) mobile-bearing and medial-pivot (MP) fixed-bearing prostheses allow axial femorotibial rotation using a highly conforming polyethylene insert. However, limited comparative data are available between the 2 designs. This study was performed to compare the midterm clinical outcomes and patient-reported outcome measures (PROMs) of RP and MP prostheses.

METHODS

We retrospectively reviewed the records of 52 total knee arthroplasties using RP mobile-bearing prosthesis and 49 total knee arthroplasties using MP fixed prosthesis with a minimum follow-up period of 5 years. Clinical and radiological outcomes, failure rates, and PROMs, including the Western Ontario and McMaster Universities Osteoarthritis Index score and satisfaction, were compared.

RESULTS

There was no difference in clinical or radiographic outcomes (P > .1 for all comparisons), with the exception of the larger flexion contracture (FC) in the MP group (0.3° in RP vs 2.3° in MP, P < .01). No failure in either group was recorded during the study period. PROMs were comparable (P > .1 in all comparisons), with the exception of higher satisfactions in the RP group while performing light household duties (P < .01) and leisure or recreational activities (P = .014) in patients without FC.

CONCLUSION

The midterm clinical results with both the RP mobile-bearing and MP fixed-bearing prostheses were satisfactory. Although both prostheses provided comparable PROMs, patients with an RP prosthesis were more satisfied than those with an MP prosthesis for highly demanding activities that are strongly associated with the presence of postoperative FC.

Medial Tibial Stress Shielding: A Limitation of Cobalt Chromium Tibial Baseplates

BACKGROUND

Stress shielding is a well-recognized complication associated with total knee arthroplasty. However, this phenomenon has not been thoroughly described. Specifically, no study to our knowledge has evaluated the radiographic impact of utilizing various tibial component compositions on tibial stress shielding.

METHODS

We retrospectively reviewed 3 cohorts of 50 patients that had a preoperative varus deformity and were implanted with a titanium, cobalt chromium (CoCr), or an all polyethylene tibial implant. A radiographic comparative analysis was performed to evaluate the amount of medial tibial bone loss in each cohort. In addition, a clinical outcomes analysis was performed on the 3 cohorts.

RESULTS

The CoCr was noted to have a statistically significant increase in medial tibial bone loss compared with the other 2 cohorts. The all polyethylene cohort had a statistically significantly higher final Knee Society Score and was associated with the least amount of stress shielding.

CONCLUSION

The CoCr tray is the most rigid of 3 implants that were compared in this study. Interestingly, this cohort had the highest amount of medial tibial bone loss. In addition, 1 patient in the CoCr cohort had medial soft tissue irritation which was attributed to a prominent medial tibial tray which required revision surgery to mitigate the symptoms.

Rotating platform versus fixed bearing total knee arthroplasty at mid-term follow-up

BACKGROUND

Rotating platform posterior stabilized (RP) total knee arthroplasty (TKA) was initially developed in part to decrease polyethylene wear and to improve patellar tracking. There have been limited studies evaluating the longevity and causes of reoperation or revision for this implant. The following study compares mid-term survival rates and causes for reoperation between fixed bearing (FB) TKAs.

METHODS

We identified 11,416 patients who underwent a primary posterior stabilized TKA between 2001 and 2013. This group was stratified to include patients with a RP (n=926) and FB (n=10,490) TKA design. Kaplan-Meier survival rates for each complication that led to reoperation were determined at five- and 10-years. Univariate hazard ratios were determined for the most common causes for reoperation and overall implant survival rates. A multivariate analysis was performed to account for the age, gender and preoperative diagnosis discrepancy between groups.

RESULTS

The reoperation data demonstrated statistically increased all-cause reoperation rate (p=<0.001) and reoperation rate for stiffness in the RP group (p=0.001). After adjusting for demographic variables we noted no statistically significant differences in reoperation rate and reoperation for stiffness. Additionally, a statistically significant decrease was noted in all-cause revision (p=0.024) and revision for aseptic loosening or osteolysis in the RP group (p=0.029).

CONCLUSION

After adjusting for patient demographic differences, we noted a statistically significant decrease in the overall revision and revision for aseptic loosening or osteolysis rates in the RP group.

Comparison of ultra-congruent mobile- and fixed-bearing navigation-assisted total knee arthroplasty with minimum 5-year follow-up

PURPOSE

The purpose of this study was to compare the midterm outcomes between fixed and mobile ultra-congruent (UC) bearings in total knee arthroplasty (TKA).

METHODS

This is a retrospective matched-pairs case-control study of patients who underwent primary navigation-assisted TKA with a minimum 5-year follow-up. A total of 182 cases involved the fixed UC bearing system as Group 1 and 101 cases involved mobile UC bearing system group as Group 2. After 1:1 matching, 73 knees in each group were enrolled. Clinical and radiographic outcomes were evaluated.

RESULTS

The overall survival was 143 of 146 cases (97.9 %) at final follow-up, and 72 of 73 cases (96.3 %) in Group 1 and 71 of 73 cases (95.8 %) in Group 2 at final follow-up based on an endpoint of revision surgery. The reasons of revision TKA were periprosthetic fracture in Group 1, infection and bearing dislocation in Group 2. There was no statistical difference in Hospital for Special Surgery (HSS) scores, Knee Society Scores (KSS), WOMAC index score evaluations between groups.

CONCLUSIONS

This study demonstrated that the fixed-bearing UC prosthesis could provide satisfactory performance compared with that of the mobile-bearing UC prosthesis with minimum 5-year follow-up. The fixed-bearing UC prosthesis could be considered in navigation-assisted TKA with theoretical advantages of UC design.

LEVEL OF EVIDENCE

IV.

Low-Contact-Stress Knee Arthroplasty: Past History or Ahead of Time?

Low-contact-stress mobile-bearing (MB) total knee arthroplasty (TKA) can rely on a long history. Its concept comprises a combination of high condylar congruency and compensatory bearing rotation to promote load sharing. However, other MB designs have become available, and critical points have been raised about the benefit of MB in general. Although there is kinematic and kinetic support for the low-contact-stress concept, there is no tribologic or clinical proof of its superiority over fixed-bearing concepts. Further study should be controlled for differences in polyethylene quality and need to provide a measure of condylar congruency to differentiate authentic low-contact-stress variants form others. [Orthopedics. 2016; 39(3):e402-e412.].

Micromotion at the tibial plateau in primary and revision total knee arthroplasty: fixed versus rotating platform designs

OBJECTIVES

Initial stability of tibial trays is crucial for long-term success of total knee arthroplasty (TKA) in both primary and revision settings. Rotating platform (RP) designs reduce torque transfer at the tibiofemoral interface. We asked if this reduced torque transfer in RP designs resulted in subsequently reduced micromotion at the cemented fixation interface between the prosthesis component and the adjacent bone.

METHODS

Composite tibias were implanted with fixed and RP primary and revision tibial trays and biomechanically tested under up to 2.5 kN of axial compression and 10° of external femoral component rotation. Relative micromotion between the implanted tibial tray and the neighbouring bone was quantified using high-precision digital image correlation techniques.

RESULTS

Rotational malalignment between femoral and tibial components generated 40% less overall tibial tray micromotion in RP designs than in standard fixed bearing tibial trays. RP trays reduced micromotion by up to 172 µm in axial compression and 84 µm in rotational malalignment models.

CONCLUSIONS

Reduced torque transfer at the tibiofemoral interface in RP tibial trays reduces relative component micromotion and may aid long-term stability in cases of revision TKA or poor bone quality.Cite this article: Mr S. R. Small. Micromotion at the tibial plateau in primary and revision total knee arthroplasty: fixed versus rotating platform designs. Bone Joint Res 2016;5:122-129. DOI: 10.1302/2046-3758.54.2000481.

Cruciate retaining and cruciate substituting ultra-congruent insert

The posterior cruciate ligament (PCL) conservation and the polyethylene insert constraint in total knee arthroplasty (TKA) are still debated. The PCL is one of the primary stabilizers of the joint, but cruciate retaining (CR) implants have the disadvantage of a difficult balancing of the PCL. Postero-stabilized (PS) implants were introduced to reduce this problem. However, also the PS implants have some disadvantages, due to the cam-mechanism, such as high risk of cam-mechanism polyethylene wear. To minimize the polyethylene wear of the cam-mechanism and the bone sacrifice due to the intercondylar box, different types of inserts were developed, trying to increase the implant conformity and to reduce stresses on the bone-implant interface. In this scenario ultra-congruent (UC) inserts were developed. Those inserts are characterized by a high anterior wall and a deep-dished plate. This conformation should guarantee a good stability without the posterior cam. Few studies on both kinematic and clinical outcomes of UC inserts are available. Clinical and radiological outcomes, as well as kinematic data are similar between UC mobile bearing (MB) and standard PS MB inserts at short to mid-term follow-up. In this manuscript biomechanics and clinical outcomes of UC inserts will be described, and they will be compared to standard PS or CR inserts.

Ten Year Follow-Up of Gap Balanced, Rotating Platform Total Knee Arthroplasty in Patients Under 60 Years of Age

68 patients (91 primary total knee arthroplasties) were evaluated at a mean 10-year, minimum 5 year follow up in patients younger than sixty years of age utilizing the gap balanced, rotating platform design. Follow up assessment included implant survivorship, adverse events, x-rays, Knee Society rating system and clinical evaluation. Three revisions were performed with only one for aseptic loosening at 45 months. Two manipulations were performed in the early postoperative period. Survivorship of the rotating platform, gap balanced knee was 96.7% using surgical revision for any reason and 98.9% using aseptic loosening as endpoints. The rotating platform design using the gap balancing technique in young patients had excellent survivorship at 10-year mean follow up.

What have we learned from 100% success of press fit condylar rotating platform posterior stabilized knees?: A 5-10 years followup by a nondesigner

BACKGROUND

Total joint arthroplasties of the hip and knee represent a remarkable feat of modern medicine in terms of reducing pain and restoring function to millions of patients afflicted with severe arthritis. Oftentimes, the performance and longevity of new implants and devices are based on limited data. This is the first study by a non-designer on the press fit condylar rotating platform posterior stabilized (PFC-RP-PS) design with 100' success. This has a relevance, vis-á -vis bias that one may have in terms of reproducibility of technique and funding from the manufacturer. We associate our excellent mid-term results to intra operative technical aspects and stringent intra operative exclusion criteria.

MATERIALS AND METHODS

Our study includes a cohort of 121 selected knees operated between January 2003 and October 2010. We used cemented, posterior stabilized (PS), mobile bearing (MB), and RP prosthesis from the same manufacturer in all these 121 knees. The patients were evaluated bi-annually with the calculation of their Knee Society Scores (KSS) and a radiological assessment for loosening/osteolysis.

RESULTS

120 knees were available for followup. The average Knee Society clinical and functional scores, respectively, were 27 points and 40 points preoperatively and 93 points and 95 points postoperatively. This indicates a mean increase of about 71' in the clinical score and about 58' in the functional score, which is statistically significant. The mean postoperative flexion was 124°, a mean increase of 23° from the preoperative flexion of 101°. There were no revisions (Kaplan--Meier survivorship of 100').

CONCLUSIONS

We feel durable and reproducible results of PFC-RP-PS design knees are very technique sensitive. The way ahead with the PFC-RP-PS knees looks promising when the exclusion criteria for this design are strictly met. Coming from a non-designer, this study acquires a higher degree of relevance without any designer's or manufacturer's bias.

Functional Results of the ROCC® Mobile Bearing Knee. 602 Cases at Midterm Follow-Up (5 to 14 Years)

We report midterm results of a prospective continuous cohort of ROCC® Total Knee Arthroplasties (TKA). Between 2001 and 2008, all primary TKA patients (n=500) received 602 ROCC saddle-shaped rotating platform TKAs. Mean follow-up was 7.5 years (5-13) (>10 years in 123 knees). 82 patients (93 knees) died; 20 patients (21 knees) were lost to follow-up. Active flexion improved from 119° (10°-150°) to 127° (90°-155°) and Knee Society knee score from 39±11 to 94±9. Two knees were reoperated for aseptic loosening: Kaplan-Meier 14-year survivorship with aseptic loosening as end-point was 99.4% (95% CI, 99.8-100). UCLA mean score increased from 3.8/10 at baseline to 7.3/10 at last FU, 91% recovering pre-disease activity, and 27% with UCLA score ≥8/10. ROCC TKA demonstrated solid midterm survivorship without activity-related complications.

LEVEL OF EVIDENCE

Therapeutic, Level IV.

Survival and functional results after a mean follow-up of 9 years with the Ceragyr® highly congruent mobile-bearing TKA

INTRODUCTION

Fixed-bearing total knee arthroplasty (TKA) implants have excellent long-term survival. Mobile-bearing implants were developed to reduce bone-implant interface stresses and polyethylene insert wear. The primary objective of this study was to analyze the survival rate of a highly congruent mobile-bearing TKA implant (Ceragyr(®)) in patients having a minimum follow-up of 7 years. We hypothesized that the survival rate would be 95-100% at that time point.

PATIENTS AND METHODS

A single-center prospective study included all the patients operated for a primary TKA procedure with a Ceragyr(®) implant between 2000 and 2003. All the implants were cemented. Patellar resurfacing was not carried out systematically, but could be carried out secondarily in cases of persistent anterior knee pain. Clinical and radiological data were collected before the surgery, at 3 months postoperative, at 1 year and then at a minimum follow-up of 7 years. The primary endpoint was the overall revision-free survival rate. Secondary endpoints were the survival without mechanical failure, IKS scores, knee range of motion and implant positioning.

RESULTS

One hundred and thirty-four patients (143 Ceragyr(®) TKA cases) were included; 9 patients (10 TKA) were lost to follow-up (6.7%) and the remaining 125 patients (133 TKA) were contacted. At the final review, 7 of the 133 TKA cases (5.3%) had been revised (6 men, 1 women; P = 0.002), 2 (1.5%) because of mechanical failure and 5 (3.8%) because of an infection. The overall revision-free survival rate was 94.8% [95% CI: 89.3-97.5]; survival was 98.4% [95% CI: 93.8-99.6] with mechanical failure as an endpoint. An in-person assessment was conducted on 76 patients (80 TKA cases) (49 women; 27 men) who had an average age of 70.3 ± 8.4 years at the time of the arthroplasty procedure. The patella had been resurfaced during the initial procedure in 49 cases, and was either not resurfaced or secondarily resurfaced in 31 cases. The average follow-up was 8.7 ± 1.1 years. The IKS score had significantly improved relative to the preoperative values (P < 0.00001). Knee flexion and the IKS knee score remained stable over time (P > 0.05). Patients who underwent patella resurfacing during the initial TKA procedure had better clinical results (P = 0.03).

CONCLUSION

After a minimum follow-up of 7years, the overall revision-free survival rate for the Ceragyr(®) was 94.8%; the survival was 98.4% with mechanical failure as an endpoint. The results were stable over time.

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.

International comparative evaluation of knee replacement with fixed or mobile non-posterior-stabilized implants

BACKGROUND

Mobile-bearing total knee prostheses were designed to reduce wear and improve implant survivorship following total knee arthroplasty. However, the benefit of mobile-bearing total knee arthroplasty remains unproven. Both mobile-bearing and fixed-bearing total knee arthroplasty implants are available in posterior-stabilized and non-posterior-stabilized designs. With the latter, the implant does not recreate the function of the posterior cruciate ligament (PCL) with a posterior-stabilizing cam mechanism. The purpose of the present study was to compare mobile-bearing, non-posterior-stabilized devices with fixed-bearing, non-posterior-stabilized devices used in total knee arthroplasty through a novel multinational study design.

METHODS

Through the use of a distributed health data network, primary total knee arthroplasties performed for osteoarthritis from 2001 to 2010 were identified from six national and regional total joint arthroplasty registries. Multivariate meta-analysis was performed with use of linear mixed models, with the primary outcome of interest being revision for any reason. Survival probabilities and their standard errors were extracted from each registry for each unique combination of the covariates.

RESULTS

A total of 319,616 patients (60% female) underwent non-posterior-stabilized total knee arthroplasty. A fixed-bearing, non-posterior-stabilized design was used in 258,190 (81%) of the knees and a mobile-bearing, non-posterior-stabilized design in 61,426 (19%) of the knees. Sixty-nine percent of the patients who received a fixed-bearing implant were over sixty-five years of age, compared with 63% of those who received a mobile-bearing implant. Mobile-bearing designs had a higher risk of revision, with a hazard ratio of 1.43 (95% confidence interval, 1.36 to 1.51; p < 0.001).

CONCLUSIONS

Previous comparisons of mobile-bearing and fixed-bearing total knee arthroplasty outcomes have been inconclusive. The current study utilized an advanced, harmonized distributed analysis of six national and regional joint-replacement registries. To our knowledge, it is the largest analysis of mobile-bearing total knee arthroplasty to date. Mobile-bearing, non-posterior-stabilized designs presented a greater risk of failure than was found for fixed-bearing, non-posterior-stabilized designs. Caution should be used in the selection of the mobile-bearing non-posterior-stabilized design for total knee replacement.

International comparative evaluation of knee replacement with fixed or mobile-bearing posterior-stabilized prostheses

BACKGROUND

Posterior-stabilized total knee prostheses were introduced to address instability secondary to loss of posterior cruciate ligament function, and they have either fixed or mobile bearings. Mobile bearings were developed to improve the function and longevity of total knee prostheses. In this study, the International Consortium of Orthopaedic Registries used a distributed health data network to study a large cohort of posterior-stabilized prostheses to determine if the outcome of a posterior-stabilized total knee prosthesis differs depending on whether it has a fixed or mobile-bearing design.

METHODS

Aggregated registry data were collected with a distributed health data network that was developed by the International Consortium of Orthopaedic Registries to reduce barriers to participation (e.g., security, proprietary, legal, and privacy issues) that have the potential to occur with the alternate centralized data warehouse approach. A distributed health data network is a decentralized model that allows secure storage and analysis of data from different registries. Each registry provided data on mobile and fixed-bearing posterior-stabilized prostheses implanted between 2001 and 2010. Only prostheses associated with primary total knee arthroplasties performed for the treatment of osteoarthritis were included. Prostheses with all types of fixation were included except for those with the rarely used reverse hybrid (cementless tibial and cemented femoral components) fixation. The use of patellar resurfacing was reported. The outcome of interest was time to first revision (for any reason). Multivariate meta-analysis was performed with linear mixed models with survival probability as the unit of analysis.

RESULTS

This study includes 137,616 posterior-stabilized knee prostheses; 62% were in female patients, and 17.6% had a mobile bearing. The results of the fixed-effects model indicate that in the first year the mobile-bearing posterior-stabilized prostheses had a significantly higher hazard ratio (1.86) than did the fixed-bearing posterior-stabilized prostheses (95% confidence interval, 1.28 to 2.7; p = 0.001). For all other time intervals, the mobile-bearing posterior-stabilized prostheses had higher hazard ratios; however, these differences were not significant.

CONCLUSIONS

Mobile-bearing posterior-stabilized prostheses had an increased rate of revision compared with fixed-bearing posterior-stabilized prostheses. This difference was evident in the first year.

Mobile-bearing total knee arthroplasty: More rotation is evident during more demanding tasks

BACKGROUND

Some reports showed few but significant more axial femorotibial rotation in favor of mobile-bearing (MB) versus fixed-bearing (FB) total knee arthroplasty (TKA), mostly during knee bend fluoroscopic studies. The goal of the current study was to submit MB and FB groups of TKA patients to a turning activity, in which additional rotation was to be expected.

METHODS

Two consecutive cohorts of patients after TKA (10 FB and 11 MB knees in a total of 18 patients) were assessed using motion analysis five year postoperatively, while performing gait and sit-to-walk (STW) movements with and without turning steps.

RESULTS

Mean range of rotation in the FB group increased from 9.7° during gait, to 11.7° during STW straight, and to 14.3° during STW turning. Mean range of rotation in the MB group increased from 13.4° during gait to 21.0° during STW straight, and stayed at 21.1° during STW turning.

CONCLUSIONS

Too many uncontrolled variables in the current study hinder a meaningful discrimination of MB from FB TKA rotation. However, the study does illustrate how more demanding task loads could be helpful in exploring the geometric constraints of TKA variants.

LEVEL OF EVIDENCE

Level III, therapeutic study.

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.

The effect of rotating platform TKA on strain distribution and torque transmission on the proximal tibia

Limited experimental data exist comparing the mechanical response of the tibial cortex between fixed and rotating platform (RP) total knee arthroplasty (TKA), particularly in the revision setting. We asked if RP-TKA significantly affects tibiofemoral torque and cortical stain response in both the primary and revision settings. Fixed and RP tibial trays were implanted into analogue tibias and biomechanically tested under axial and torsional loading. Torque and strain response were analyzed using digital image correlation. Fixed bearing designs exhibited 13.8 times greater torque (P<0.01), and 69% (P<0.01) higher cortical strain than RP designs. Strain response was similar in the primary and revision cohorts. The decrease in torque transfer could act as a safeguard to reduce stress, micromotion and torsional fatigue in scenario of poor bone stock.

Do refinements to original designs improve outcome of total knee replacement? A retrospective cohort study

Background

Long-term results of the 'classic’ low contact stress (LCS) total knee replacement (TKR) have been satisfactory; nonetheless, design changes have been made which resulted in the 'complete’ LCS TKR. The aim of this study is to compare the 5-year incidence of revision and midterm clinical performance before and after introduction of the 'complete’.

Methods

A retrospective cohort analysis was conducted on 100 primary uncemented TKRs of both designs. At 5-year follow-up, revision and reoperation rates were determined for these 200 TKRs. Knee Society score (KSS), the Oxford Knee score (OKS) and range of motion were determined for 143 TKRs.

Results

In the 'classic’ cohort, 3% of the TKRs were revised compared with 5% in the 'complete’ cohort (p = 0.72).The mean KSS was 134.1 (SD 38.3) in the 'classic’ cohort compared to 135.0 (SD 42.8) in the 'complete’ cohort (p = 0.89). Of the 'complete’ TKRs, 35.2% scored within the lowest quartile of the KSS knee compared to 16.7% of the 'classic’ TKRs (p = 0.01). The OKS was 23.3 (SD 9.3) in the 'classic’ cohort compared to 22.5 (SD 10.1) in the 'complete’ cohort (p = 0.45). More than 5° flexion contracture was only found in four patients in the 'complete’ cohort (p = 0.04).

Conclusions

No statistical difference in revision rate and average scores for midterm clinical performance was observed between the 'classic’ and the 'complete’. However, the 'complete’ cohort had a higher percentage of KSS Knee in the lowest quartile, which suggests a clinical relevant difference compared with the 'classic’. Further investigation in future studies with new designs is needed.

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.

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.

Outcomes of 447 SCORE® highly congruent mobile-bearing total knee arthroplasties after 5-10 years follow-up

INTRODUCTION

The goal of mobile-bearing total knee arthroplasties (TKA) with an anatomical trochlea is to reduce polyethylene wear, the risk of loosening, and patellofemoral complications. Rotating mobile-bearing SCORE(®) TKA was designed according to these principles with standard instrumentation for component placement and a specific computer navigation system, Amplivision(®).

HYPOTHESIS

We hypothesized that the results of SCORE(®) TKA would be satisfactory and better using computer navigation with or without patellar resurfacing and that there would be no specific patellofemoral complications associated with this trochlear design.

MATERIALS AND METHODS

Four hundred and forty-seven SCORE(®) TKA were performed. Outcome assessment was based on the IKS score, and component survival calculated by Kaplan-Meier analysis.

RESULTS

Mean follow-up was 6.6 years (maximum 10.6 years). Six percent of patients were lost to follow-up. Ninety-eight percent of the patients were satisfied or very satisfied. The IKS knee score was 89 points and the function score was 86. The mechanical axis was 180° (174-186), and it was significantly improved if the initial deformity was severe and TKA was computer navigated. There were nine revisions (one for fracture, two for pain, two for stiffness, four for infection).

DISCUSSION

This study confirmed our hypothesis: the results of SCORE(®) TKA were very satisfying after at least 5 years of follow-up because there was no mechanical loosening, no bearing dislocation and no patellofemoral complications with or without patellar resurfacing. Results were identical whether patellar resurfacing was performed or not. Although clinical results were not better for computer- navigated TKA, radiological results were. At 98 months of follow-up, component survival in relation to the risk of aseptic loosening or patellofemoral complications was 100%.

LEVEL OF EVIDENCE

Level IV continuous retrospective study.

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.

Acceleration-based joint stability parameters for total knee arthroplasty that correspond with patient-reported instability

There is no universally accepted definition of human joint stability, particularly in nonperiodic general activities of daily living. Instability has proven to be a difficult parameter to define and quantify, since both spatial and temporal measures need to be considered to fully characterize joint stability. In this preliminary study, acceleration-based parameters were proposed to characterize the joint stability. Several time-statistical parameters of acceleration and jerk were defined as potential stability measures, since anomalous acceleration or jerk could be a symptom of poor control or stability. An inertial measurement unit attached at the level of the tibial tubercle of controls and patients following total knee arthroplasty was used to determine linear acceleration of the knee joint during several activities of daily living. The resulting accelerations and jerks were compared with patient-reported instability as determined through a standard questionnaire. Several parameters based on accelerations and jerks in the anterior/posterior direction during the step-up/step-down activity were significantly different between patients and controls and correlated with patient reports of instability in that activity. The range of the positive to negative peak acceleration and infinity norm of acceleration, in the anterior/posterior direction during the step-up/step-down activity, proved to be the best indicators of instability. As time derivatives of displacement, these acceleration-based parameters represent spatial and temporal information and are an important step forward in developing a definition and objective quantification of human joint stability that can complement the subjective patient report.

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.

Functionality and Safety of an Ultra-Congruent Rotating Platform Knee Prosthesis at 5.6 Years: More than 5- Year Follow-Up of the e.motion ((®)) UC-TKA

Background:

Mobile bearing TKA prostheses were designed to minimize polyethylene wear by increasing implant conformity and reducing stresses between the articulating prosthesis components. It is the purpose of this study to assess the mid-term functionality and clinical outcome associated with a highly congruent mobile platform design, the e.motion^® UC total knee prosthesis.

Material and Methods:

Functional and clinical outcomes were assessed after an average of 5.6 years (5.1 – 6.0 years) after total knee arthroplasty in 28 patients (24 women), aged 77.8±7.5 years. The Knee injury and Osteoarthritis Outcome Score (KOOS) was assessed. Secondary outcomes included the Knee Society Score (KSS), radiological evaluation of radiolucent lines and recording of adverse events.

Results:

The average KOOS subscore for the activities of daily life was 77.8 points after 5.6 years. Both the clinical and functional KSS improved at 2.4 and 5.6 years. Two patients showed radiolucent lines at 5.6 years. Adverse events over 5.6 years included 3 subluxations, 1 tilting and 1 misalignment of the patella. None of the prostheses were revised.

Conclusion:

This pilot study shows promising outcomes for the e.motion^® UC prosthesis. In the small sample, the implant performed comparably to the LCS prosthesis (the gold standard). There were no loosenings or revisions observed at 5.6 years.

Poor short-term outcomes after computer-assisted rotating-platform total knee arthroplasty with a deep-trochlear-groove femoral component: analysis of 19 patients

BACKGROUND

Congruent rotating tibial plateaus are designed to minimise wear after total knee arthroplasty (TKA). The Score™ prosthesis has a congruent rotating tibial plateau, a deep trochlear groove, and uses a computer-assisted navigation system for ligament balancing. Although this prosthesis is widely utilized, no accurate data on outcomes are available.

HYPOTHESIS

The innovative features of the Score™ prosthesis, most notably patellar replacement with a highly constrained femoral component, do not jeopardize implant survival.

PATIENTS AND METHODS

In a pilot study, we retrospectively evaluated outcomes of 19 patients treated with Score™ knee replacement between February and October 2006 (mean age, 66.8 years; range, 58-82 years). The evaluation criteria were the International Knee Society (IKS) scores and prosthesis survival rate estimated using Kaplan-Meier plots with failure defined as revision need to change the prosthesis.

RESULTS

Mean follow-up was 35.3 months. The IKS knee score increased from 27.4 (5-60) preoperatively to 81.4 (45-99) at last follow-up (P<0.0001). Mean mechanical axis was 181.2° (180-186°), with 16 between 180° and 183°. Revision surgery was required in five cases (for patellar complications with combined motion-range limitation in flexion (<90°) and extension (5-20°) in three cases, isolated motion-range limitation in one case, and recurvatum deformity with instability in one case). Prosthesis survival was 82% (73-91%) after 24 months and 65% (51-78%) after 44 months.

DISCUSSION

The deep trochlear groove femoral component resulted in patellar complications, which were the most common reasons for revision surgery, together with motion-range limitation and instability possibly related to improper use of the navigation system. This small retrospective case-series study showed an unusually low prosthesis survival rate probably related to the implant design. We no longer use the Score™ prosthesis, despite the availability of a dedicated navigation system, and we recommend careful monitoring of patients who have this prosthesis.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Simultaneous bilateral total knee arthroplasty. A multicenter feasibility study

INTRODUCTION

The value and risk of simultaneous total knee arthroplasty (TKA) in patients with bilateral knee arthritis is a subject of debate.

HYPOTHESES

The risk of complications following simultaneous bilateral TKA will be increased compared to the rates published in the literature for unilateral TKA, and the clinical and functional outcomes will be poorer in this particular group.

MATERIALS AND METHODS

One hundred and twenty-three patients who underwent simultaneous bilateral TKA between 2005 and 2011 in five specialized, high volume centers were evaluated. The files were analyzed retrospectively after a mean 33 months of follow-up.

RESULTS

The mean hospital stay was 11 days. Mean blood loss was 4.1g/dL. A postoperative transfusion was performed in 68 patients (55%), with a mean 3.1 units of blood. The mean global IKS score increased from 90 to 150 points. Eighty patients would agree to undergo simultaneous bilateral TKA again (65%), and 70 would recommend this procedure to others (57%).

DISCUSSION

The hypothesis was not confirmed: the risk of complications was not increased compared to the generally accepted risk of a unilateral procedure. The risk of complications in this study was very similar to that published in the literature for the same therapeutic strategy. Therefore, there is no solid medical evidence to prevent recommending this strategy. The results of the participating centers suggest that this therapeutic approach should be continued in selected indications.

LEVEL OF EVIDENCE

IV, retrospective study.