Greater satisfaction in older patients with a mobile-bearing compared with fixed-bearing total knee arthroplasty

The influence of implant factors on patient outcomes in primary total knee arthroplasty

Background

The influence of implant factors on patient-reported outcome measures (PROMS) after total knee arthroplasty (TKA) has previously been studied but findings are often inconsistent, restricted in scope and biased by confounding factors. This study aims to determine the association between implant-related factors and early post-operative PROMs after TKA.

Methods

Using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) PROMs program, the study included 9487 primary TKA procedures performed in 43 hospitals from July 31, 2018 to December 31, 2020. Data included baseline demographic data, surgical details and PROMs collected pre- and 6 months post-operatively. Seven prosthesis characteristics were incorporated in the multivariable model, with proportional odds ordinal regression analysis used to assess their effects on post-operative Oxford knee score (OKS) and joint pain. Adjustments were made for pre-operative OKS and joint pain, as well as potential patient confounders.

Results

At six months, fixed bearing implants showed higher odds of better OKS compared to mobile bearing implants (odds ratio [OR] = 1.20, 95 % confidence interval [CI] 1.06-1.37. p < 0.004). Similar findings were found with the use of image derived instrumentation (IDI) (OR = 1.27, 95 % CI 1.11-1.46, p < 0.001), robotic assisted vs. non-navigated knees (OR = 1.21, 95 % CI 1.06-1.38, p < 0.005) and no patella resurfacing (OR = 1.10, 95 % CI 1.01-1.20, p < 0.032). For lower pain scores at six months, the use of highly crosslinked polyethylene (OR = 1.12, 95 % CI 1.02-1.22, p < 0.015), cemented femoral components (OR = 1.11, 95 % CI 1.01-1.22, p < 0.024), IDI (OR = 1.20, 95 % CI 1.05-1.37, p < 0.009) or no patella resurfacing (OR = 1.10, 95 % CI 1.01-1.20, p < 0.034) were associated.

Conclusion

Utilizing a fixed bearing or robotic assistance correlated with improved OKS scores, whereas highly crosslinked polyethylene or cemented femoral components were associated with improved pain scores. At six months, the use of IDI compared to non-navigated TKA, and patellar resurfacing showed both improved OKS and pain scores.

Fixed-Bearing and Higher Postoperative Knee Flexion Angle as Predictors of Satisfaction in Asian Patients Undergoing Posterior-Stabilized Total Knee Arthroplasty

Background

Patient-reported satisfaction following total knee arthroplasty (TKA) can be affected by various factors. This study aimed to assess patient satisfaction rates and identify factors related to patients, surgery, and postoperative knee motion associated with satisfaction in posterior-stabilized TKA among Asian patients.

Methods

A retrospective cross-sectional study was conducted in patients with primary osteoarthritis who underwent TKA and had a follow-up period of over 2 years. Patient satisfaction was measured using a 5-point Likert scale, and the patients were divided into satisfied and dissatisfied groups. The factors potentially affecting satisfaction were collected, including demographics, comorbidities, surgical options, and knee motion. Univariate and multivariate regression analyses were performed.

Results

Of the 858 patients included, 784 (91.4%) were satisfied and 74 (8.6%) were dissatisfied. Fixed-bearing implants and higher postoperative knee flexion angles were associated with satisfaction (odds ratio [OR], 2.366; p = 0.001 and OR, 1.045; p < 0.001, respectively), whereas cerebrovascular disease was related to dissatisfaction (OR, 0.403; p = 0.005). The regression model demonstrated moderate predictability (R 2 = 0.112).

Conclusions

Fixed-bearing implants and higher postoperative knee flexion angles were associated with patient satisfaction following TKA, whereas cerebrovascular disease was associated with dissatisfaction. The identification of these factors could help improve surgical outcomes and patient satisfaction following TKA.

Comprehensive evaluation of risk factors for aseptic loosening in cemented total knee arthroplasty: A systematic review and meta-analysis

Purpose

Aseptic loosening is the most common cause for revisions after total knee arthroplasty (TKA). Despite many studies exploring various risk factors associated with aseptic loosening, findings often present inconsistencies. To address this, we conducted a thorough review of the literature to identify and analyse these risk factors in cemented TKA. Additionally, we performed a meta-analysis to reconcile the divergent conclusions observed across studies.

Methods

We searched PubMed, Web of Science and Embase from 1996 up to 2024 and evaluated the quality of the included literature. Seventy-four studies were included to assess the association of BMI, diabetes, high physical activity (HPA), osteoporosis, rheumatoid arthritis (RA), cement material and implant design. Twenty-nine studies were used to calculate relative risk and CIs (using the random effects theory) and study heterogeneity for six different risk factors (BMI, diabetes, HPA level, cement material, polyethylene and implant design).

Results

Patients with diabetes are eight times more likely to experience aseptic loosening compared to those without diabetes (RR = 9.18, 95% CI: 1.80-46.77, p < 0.01). The use of tibial stem extension or highly crosslinked polyethylene can help reduce the incidence of aseptic loosening. However, we did not identify BMI, HPA, osteoporosis, RA, the use of high-viscosity cement and the utilization of mobile-bearing designs as risk factors for aseptic loosening post-cemented TKA.

Conclusions

Patients with diabetes undergoing TKA should be counselled regarding their potential increased risk of aseptic loosening. The use of tibial stem extensions and HXLPE can mitigate the incidence of aseptic loosening in cemented TKA. However, given a limited number of studies were included in the meta-analysis, we believe that higher-level studies are necessary to clearly identify other risk factors.

Level of Evidence

Level III.

Are Orthopaedic Clinical Trials Linguistically and Culturally Diverse? A Systematic Review

Purpose

Underrepresentation and misrepresentation of historically underrepresented populations in randomized controlled trials (RCTs) may have implications for the validity of research results and their application for diverse populations. To evaluate the representation of historically linguistically, racially, and ethnically underrepresented participants in orthopaedic randomized controlled trials (RCTs) and to assess the use of translated and culturally adapted patient reported outcome measures (PROMs).

Methods

Separate and comprehensive literature searches of PubMed, Web of Science, and Embase databases were performed to identify RCTs utilizing PROMs between the years 2012 - 2022 among the top five highest 5-year impact factor orthopaedic journals according to the 2021 Journal Citation Reports database. The primary outcomes of interest included reporting of linguistic, racial and ethnic demographic characteristics of trial participants and the utilization of translated PROMs. The methodological quality of each clinical trial was assessed using the Jadad Criteria.

Results

230 RCTs met inclusion criteria. The language of participants was reported in 14% of trials and in 17% of trials when searching both the published text and clinical trial registration information. In addition, race and/or ethnicity was reported in 11% of trials, and the use of translated PROMs was reported in 7% of trials. Among the six multinational studies, none reported the language of the study population nor the use of translated PROMs. Notably, four studies (2%) reported utilizing culturally adapted PROMs. The average Jadad score was 3.07.

Conclusion

Participant language, race, and ethnicity are infrequently reported in orthopaedic clinical trials, potentially limiting the application and interpretation of study results. Similarly, the linguistic and cultural adaptation of PROMs utilized are often not reported, which also limits interpretations of the validity and generalizability of orthopedic study results. Researchers and journals should promote standard reporting of demographic data and methods of PROM adaptation to ensure results are generalizable to diverse patient populations.

Level of Evidence

III.

Patient Selection in Randomized Controlled Trials of Total Knee Arthroplasty: A Systematic Review Assessing Inclusion Criteria

BACKGROUND

Patients undergo total knee arthroplasty (TKA) at widely disparate stages of osteoarthritis, raising the possibility of high heterogeneity among patients enrolled in TKA research studies. Obscuration of treatment effectiveness and other problems that may stem from cohort heterogeneity can be controlled in clinical studies by rigorously defining target patients. The purpose of this review was to determine the extent to which randomized controlled trials (RCTs) on TKA use osteoarthritis severity, as defined by radiographic grade or patient-reported outcome measures (PROMs), in their inclusion criteria, and to investigate potential impact on outcome.

METHODS

A search of PubMed, Embase, Scopus, Web of Science, and Cochrane databases used a combination of terms involving TKA, PROMs, and radiographic scoring. A total of 1,227 studies were independently reviewed by 2 screeners for the above terms. RCTs with ≥100 patients (236) and with <100 patients (325) undergoing TKA were analyzed with regard to the specific inclusion criteria and recruitment process.

RESULTS

Among the identified RCTs with ≥100 patients, 18 (<8%, with a total of 2,952 randomized patients) used specific radiographic scoring or PROM thresholds in their inclusion criteria. Eleven of the 18 studies used specific radiographic scoring, such as the Kellgren-Lawrence or Ahlbäck classifications. Three studies used preoperative PROM thresholds: Knee Society Knee Score of <60, Knee Society Function Score of <60, Oxford Knee Score of <20, and Hospital for Special Surgery Score of <60. Among studies with <100 patients, 48 (<15%) used specific inclusion criteria.

CONCLUSIONS

The vast majority of RCTs (>85%) did not enroll patients based on disease severity, as measured by PROM score thresholds or radiographic classifications, in their inclusion criteria. The lack of consistent inclusion criteria likely results in heterogeneous cohorts, potentially undermining the validity of RCTs on TKA.

LEVEL OF EVIDENCE

Prognostic Level I . See Instructions for Authors for a complete description of levels of evidence.

Comparison of Patient-Reported Outcomes and Functional Assessment Using a Marker-Less Image Capture System in End-Stage Knee Arthritis

BACKGROUND

Patient self-assessment of knee function in end-stage osteoarthritis (OA) and following total knee arthroplasty (TKA) using patient-reported outcome measures (PROMs) has become standard for defining disability. The relationship of PROMs to functional performance requires a continued investigation. The purpose of this study was to determine correlations between patient demographics, PROMs, and functional performances using a marker-less image capture system (MICS).

METHODS

Patients indicated for elective TKA completed the Knee Injury and Osteoarthritis Score for Joint Replacement (KOOS-JR) and an office-based functional assessment using a MICS. Patient age, body mass index (BMI), and gender were collected. A total of 112 patients were enrolled. Their mean age was 65.0 (±9.7) years, mean BMI was 32.5 (±6.6) kg/m², and mean KOOS-JR was 14.5 (±5.7). The relationships between patient characteristics, KOOS-JR, MICS Alignment (coronal), MICS Mobility (flexion), and composite Total Joint scores were described using Spearman's correlation coefficients.

RESULTS

BMI was weakly correlated with KOOS-JR (ρ = -0.22, P = .024), whereas age was not. Age and BMI were not correlated with performance scores. There were weak to no correlations between KOOS-JR and MICS Alignment (ρ = -0.01, P = .951), Mobility (ρ = 0.33, P < .001), and Total Joint scores (ρ = 0.06, P = .504).

CONCLUSION

This study found no strong correlation between KOOS-JR and functional performance using a validated MICS for patients with end-stage knee OA. Further study is warranted in determining the relationship between PROMs and performance to optimize outcomes of patients undergoing nonoperative or surgical interventions for knee OA. The use of high-fidelity functional assessment tools that can be integrated into clinical workflow, such as the MICS used in this study, should permit PROM/functional performance comparisons in large populations.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Level I.

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

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

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).

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.

Total knee arthroplasty in patients with Ranawat type-II valgus arthritic knee with a marked coronal femoral bowing deformity: comparison between computer-assisted surgery and intra-articular resection

Background

Proper limb and component alignments as well as soft tissue balance are vital for the longevity and optimal long-term outcomes of total knee arthroplasty (TKA). This procedure is technically demanding in patients with Ranawat type-II valgus arthritic knees with marked coronal femoral bowing. Computer-assisted surgery (CAS) and intra-articular bone resection with TKA are the treatments of choice for patients with ipsilateral extra-articular deformity. In theory, both CAS and intra-articular bone resection are beneficial in Ranawat type-II valgus arthritic knees with marked coronal femoral bowing deformity, but the literature on this topic is sparse. We compared the benefits of using these two techniques for TKA under this circumstance.

Methods

Patients who had Ranawat type-II valgus arthritic knees and marked coronal femoral bowing deformity and had undergone TKA at our hospital between 2005 and 2013 were enrolled in this retrospective study. Patients treated with CAS were assigned to the CAS-TKA group; patients treated with intra-articular bone resection were assigned to the Bone-Resect-TKA group. Radiographic parameters and clinical outcomes (International Knee Society (IKS) scores and patellar scores) in both groups were compared.

Results

Forty-seven patients (50 knees) met the inclusion criteria: 22 knees in the CAS-TKA group and 28 knees in the Bone-Resect-TKA group. Lateral retinaculum release was significantly (P = 0.008) higher in the Bone-Resect-TKA group. The joint-line was significantly properly restored in the CAS-TKA group (P = 0.011). The reconstructed mechanical axis was significantly (P = 0.012) closer to normal in the CAS-TKA group than in the Bone-Resect-TKA group. For component alignment, the femoral valgus and femoral flexion angles were significantly better in the CAS-TKA group (P = 0.002 and P = 0.006, respectively), but not the tibial valgus, tibial flexion, or patellar tilting angles. IKS scores and patellar scores were not significantly different between groups at a mean follow-up of 60.2 months.

Conclusions

CAS-TKA was effective for obtaining proper alignment and joint-line restoration in patients with Ranawat type-II valgus arthritic knees and marked coronal femoral bowing deformity, but not for yielding better clinical outcomes. Additional large-scale prospective randomized cohort studies with long-term follow-ups are necessary to make evidence-based recommendations.

Higher forgotten joint score for fixed-bearing than for mobile-bearing total knee arthroplasty

PURPOSE

To compare the postoperative subjective outcome for fixed- and mobile-bearing total knee arthroplasty (TKA) by using the forgotten joint score (FJS-12), a new patient-reported outcome score of 12 questions evaluating the potential of a patient to forget about his operated joint. The hypothesis of this study was that a mobile-bearing TKA would have a higher level of forgotten joint than a fixed-bearing model of the same design.

METHODS

A retrospective cohort study was conducted in 100 patients who underwent TKA at least 1 year [mean (SD) 18 (5) months] before with either a fixed-bearing (N = 50) or a mobile-bearing (N = 50) TKA from the same implant family. Clinical outcome was evaluated with the knee society score and patient-reported outcome with the forgotten joint score.

RESULTS

No difference was observed for demographics in between both study groups. The mean (SD) postoperative FJS-12 for the fixed-bearing TKA was 71 (28) compared to a mean (SD) of 56.5 (30) for the mobile-bearing TKA.

DISCUSSION

The clinical relevance of the present retrospective study is that it shows for the first time a significant difference between fixed- and mobile-bearing TKA by using a new patient-reported outcome score. The hypothesis that mobile-bearing TKA would have a higher degree of forgotten joint than a fixed-bearing TKA could not be confirmed. A level I prospective study should be set up to objectivise these findings.

LEVEL OF EVIDENCE

IV.

The Influence of Alignment on Midterm Outcome after Total Knee Arthroplasty in Patients With Marked Coronal Femoral Bowing

Whether the mechanical axis should be restored to neutral remains controversial when the patient has marked coronal femoral bowing. Eighty-four total knee arthroplasties were retrospectively reviewed. In the neutral-aligned group A the immediate postoperative mechanical axis of 179 ± 1° held stable (P = 0.841). The postoperative mechanical axis decreased from 176 ± 1° to 173 ± 1° (P = 0.024) in the outlier group. Progressive varus in the outlier group at follow-up was probably due implant instability and ligament imbalance as well as excessive polyethylene wear. At a mean follow-up of 75.8 months, no statistically significant difference was detected between the two groups. Long-term follow up will be needed to determine if the maintenance in radiographic results translates to better clinical outcomes.

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

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

The benefits of computer-assisted total knee arthroplasty on coronal alignment with marked femoral bowing in Asian patients

Background

Mechanical alignment guides are designed to compensate for variations in the valgus alignment angle; however, these guides may not be adequate when a patient has coronal alignment with marked bowing deformity. Previous study demonstrates better radiographic results, but the clinical benefits are a matter of speculation. The aim of this study was to investigate whether radiographic benefits of computer-assisted surgery total knee arthroplasty (CAS-TKA) would translate to clinical outcomes.

Methods

Patients with osteoarthritis and coronal alignment with marked bowing deformity who underwent total knee arthroplasty (TKA) at our institution between January 2005 and June 2012 were entered into this retrospective study. Patients were divided into three groups: patients with coronal alignment with marked bowing deformity treated with CAS-TKA; with coronal alignment with marked bowing deformity treated with conventional TKA; and without marked coronal bowing deformity treated with conventional TKA. The computer-assisted navigation and the conventional technique were then compared by radiographic parameters. The International Knee Society (IKS) scores and patellar score were obtained for all patients preoperatively and at the last follow-up visit.

Results

One hundred and thirty-seven patients (198 knees) met the inclusion criteria. For patients with osteoarthritic knees with marked femoral bowing deformity, the reconstructed mechanical axis (MA) was significantly closer to normal in the CAS-TKA group (P = 0.002) than in the conventional group. Significant differences in the reconstructed MA after conventional TKA were noted between patients without bowing and those with bowing (P = 0.003). Using the patellar score and IKS score, at a mean follow-up of 52.2 months, the differences did not achieve statistical significance among the three groups.

Conclusions

CAS-TKA was an effective alternative for obtaining proper alignment in patients with coronal alignment with marked bowing deformity. However, there was no statistically significant difference in clinical function between patients treated with CAS-TKA and conventional TKA. Long-term follow-up will be needed to determine if the improvement in radiographic results translates to better clinical outcomes.

Differences in component and limb alignment between computer-assisted and conventional surgery total knee arthroplasty

PURPOSE

Marked coronal femoral bowing may bear a risk for mal-alignment of femoral component and reconstructed mechanical axis (MA) by using conventional instrumentations. The aim of this study was to investigate the usefulness of computer-assisted surgery-total knee arthroplasty (CAS-TKA) under this circumstance.

METHODS

We retrospectively analyzed patients with osteoarthritic knee and marked coronal femoral bowing who underwent TKA at our institution. The CAS-TKA and the conventional techniques were compared by radiographic parameters in coronal and sagittal planes, and rotational alignment of femoral component was assessed by computed tomography (CT) scans. The Hospital for Special Surgery (HSS) and International Knee Society (IKS) scores were obtained for all patients preoperatively and at the last follow-up.

RESULTS

A total of 65 knees were enrolled in this study. Twenty-eight TKAs implanted using a CT-free navigation system, and the remaining 37 TKAs implanted using the conventional technique. CAS-TKAs were more consistent than conventional TKAs in aiding proper postoperative MA and ideal alignments of femoral component in the coronal and sagittal planes. However, CAS-TKA group was not obtained at significantly higher rates of femoral component in axial plane. At a mean follow-up of 43 months, there was no significant difference in HSS and IKS scores between the groups.

CONCLUSIONS

Although CAS-TKA did not have superior functional outcomes in the short-term follow-up, proper coronal and sagittal alignment of femoral component and postoperative MA were obtained in patients with marked coronal femoral bowing. The long-term follow-up will be needed to clarify the eventual benefits.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

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.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

II.

Comparison of functional performance after total knee arthroplasty using rotating platform and fixed-bearing prostheses with or without patellar resurfacing

OBJECTIVE

To retrospectively compare the functional performances of rotating platform and fixed-bearing total knee arthroplasties with or without patellar resurfacing.

METHODS

One hundred and ninety-seven patients (205 knees) of mean age 66.4 years were randomly assigned to receive different prostheses. One hundred ninety-five patients, including 97 fixed-bearing prostheses with 37 patellae resurfaced and 106 rotating platform prostheses with 76 patellae resurfaced, were followed up for a mean duration of 32 months.

RESULTS

Outcomes in the rotating platform with patellar resurfacing and fixed-bearing with patellar resurfacing groups did not differ significantly according to Hospital for Special Surgery (HSS) scores and flexion and extension angles. For total knee arthroplasties without patellar resurfacing, there were no significant differences in HSS score and flexion angle between the rotating platform and fixed-bearing subgroups. Although the extension angle of rotating platform prostheses was slightly better than that of the fixed-bearing in the patellar non-resurfacing group, this difference was not clinically significant.

CONCLUSIONS

Rotating platform and fixed-bearing prostheses have similar overall postoperative outcomes with regard to postoperative HSS scores and extension and flexion angles. Rotating platform prostheses are not superior to fixed bearing prostheses.

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

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

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

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

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