High-flexion vs conventional prostheses total knee arthroplasty: a meta-analysis

Different squatting positions after total knee arthroplasty: A retrospective study

BACKGROUND

Total knee arthroplasty (TKA) has been shown to improve quality of life and reduce pain. High-flexion activities such as squatting, kneeling, and floor transfers are mainly listed as demanding tasks. Among them, squatting is an important position.

AIM

To provide a new squat position classification and evaluate the different squatting positions of a series of patients after primary TKA.

METHODS

From May 2018 to October 2019, we retrospectively reviewed 154 video recordings of the squatting-related motions of patients after TKA. Among the included patients, 119 were women and 35 were men. Their mean age at the index surgery was 61.4 years (range, 30 to 77).

RESULTS

The median follow-up was 12 mo (range, 6 to 156 mo). We classified those squatting-related motions into three major variations according to squatting depth: Half squat, parallel squat, and deep squat. The angles of hip flexion, knee flexion, and ankle dorsiflexion were measured in the screenshots captured from the videos at the moment of squatting nadir. A total of 26 patients were classified as half squats, 75 as parallel squats, and 53 as deep squats. The angles of hip flexion, knee flexion, and ankle dorsiflexion all differed significantly among the three squatting positions (P < 0.001). In the parallel squat group, the mean knee flexion angle (°) was 116.5 (SD, 8.1; range, 97 to 137). In the deep squat group, the mean knee flexion angle (°) was 132.5 (SD, 9.3; range, 116 to 158).

CONCLUSION

Among the three squatting positions, deep squat showed the highest hip, knee, and ankle flexion angles, followed by the parallel squat. With the improvement of squatting ability, the patient's postoperative satisfaction rate was also significantly enhanced. However, the different squatting abilities of the patients cannot be effectively distinguished from the scoring results (P > 0.05). Our squatting position classification offers a pragmatic approach to evaluating patients’ squatting ability after TKA.

Ten-Year Follow-Up of High-Flexion Versus Conventional Total Knee Arthroplasty: A Matched-Control Study

BACKGROUND

High-flexion total knee arthroplasty (HF-TKA) prostheses were designed with hopes of improving knee function. Studies have suggested increased failure with HF-TKAs. The purpose is to compare clinical results of HF-TKA versus conventional TKA (C-TKA) from the same implant system with long-term follow-up.

METHODS

This review of prostheses implanted between 2004 and 2007 matched 145 of 179 possible HF-TKAs with 145 of 1347 possible C-TKAs. Mean follow-up was 121.5 ± 20.3 months. We were unable to match 12 HF-TKAs. HF-TKAs with less than 8-year follow-up were excluded. The primary outcome was failure requiring revision. Secondary outcomes included range of motion (ROM), Knee Society Scores (KSS), and radiolucent lines.

RESULTS

In the matched cohort, there were 15 HF-TKA reoperations, 8 of which involved component revisions. There were 12 reoperations in the C-TKA cohort but no component revisions (P = .001). The analysis of the unmatched cohorts revealed a higher revision rate for HF-TKAs (P = .039) (HF-TKA: 10/179 vs C-TKA: 27/1347). At final follow-up, HF-TKAs exhibited more prosthesis radiolucent lines without evidence of loosening. Particularly, HF-TKAs demonstrated more femoral zone IV radiolucencies (38.7%) at final follow-up compared with C-TKAs (13.8%) (P < .001). There were no differences found between cohorts in ROM or KSS.

CONCLUSION

This study found an increased incidence of failure requiring revision with the HF-TKA in the matched and unmatched analyses. Higher incidences of radiolucent lines were found with HF-TKA. With no observed differences in ROM or KSS and a higher rate of failure with HF-TKA, there appears to be no advantage for use of the HF-TKA.

[Effectiveness comparison of partial versus intact posterior cruciate ligament-retaining in total knee arthroplasty with cruciate-retaining prosthesis]

Objective

To compare the effectiveness of partial versus intact posterior cruciate ligament (PCL)-retaining in total knee arthroplasty (TKA) with cruciate-retaining (CR) prosthesis.

Methods

A total of 200 patients with osteoarthritis, who met the selection criteria and proposed unilateral TKA with CR prosthesis, were included in the study and randomly assigned into two groups ( n=100). The patients were treated with intact retention of the double bundles of PCL in intact group and with partial resection of the anterior lateral bundle of PCL and the anterior bone island at the time of intraoperative tibial osteotomy in partial group. Patients with lost follow-up and re-fracture were excluded, and 84 cases in partial group and 88 cases in intact group were included in the final study. There was no significant difference between the two groups ( P>0.05) in terms of gender, age, body mass index, course and grade of osteoarthritis, preoperative varus deformity of knee joint, flexion contracture, range of motion, clinical and functional scores of Knee Society Score (KSS). The operation time, wound drainage volume during 24 hours after operation, visual analogue scale (VAS) score at 24 hours after operation, range of motion of knee joint, clinical and functional scores of KSS, and the anteroposterior displacement of knee joint at 30° and 90° flexion positions were compared between the two groups.

Results

There was no significant difference between the two groups in operation time, wound drainage volume during 24 hours after operation, and VAS score at 24 hours after operation ( P>0.05). Patients in both groups were followed up after operation. The follow-up time was 25-40 months (mean, 30.2 months) in intact group and 24-40 months (mean, 31.8 months) in partial group. There was no significant difference in the range of motion and clinical scores of KSS between the two groups at 6, 12, and 24 months after operation ( P>0.05). The functional scores of KSS were significantly higher in intact group than in partial group ( P<0.05). There was no significant difference between the two groups in the anteroposterior displacement of knee joints at 30° flexion position at 6, 12, and 24 months after operation ( P>0.05). When the knee was at 90° flexion position, there was no significant difference between the two groups at 6 and 12 months after operation ( P>0.05), but the intact group was significantly smaller than partial group at 24 months after operation ( P<0.05). Postoperative incision continued exudation in 4 patients (2 cases of partial group and 2 cases of intact group), and incision debridement in 2 patients (1 case of partial group and 1 case of intact group). No prosthesis loosening, excessive wear, or dislocation of gasket was found during follow-up.

Conclusion

The double bundle of PCL plays an equally important role in maintaining the stability of the knee joint, and the integrity of PCL should be kept as much as possible when TKA is performed with CR prosthesis.

Total Knee Arthroplasty Using Bicruciate-Stabilized or Posterior-Stabilized Knee Implants Provided Comparable Outcomes at 2 Years: A Prospective, Multicenter, Randomized, Controlled, Clinical Trial of Patient Outcomes

BACKGROUND

The bicruciate-stabilized (BCS) knee arthroplasty was developed to replicate normal knee kinematics. We examined the hypothesis that patients with osteoarthritis requiring total knee arthroplasty (TKA) will have better functional outcome and satisfaction with the BCS implant compared with an established posterior cruciate-stabilized implant.

METHODS

This multicenter, randomized, controlled trial compared the clinical outcomes of a BCS implant against an established posterior cruciate-stabilized implant with 2-year follow-up. Of the patients awaiting primary knee arthroplasty for osteoarthritis, 228 were randomized to receive either a posterior-stabilized or BCS implant. Primary outcomes were knee flexion and Oxford Knee Score. Secondary outcomes were rate of complications and adverse events (AEs). Tertiary outcomes included Knee Society Score, University of California, Los Angeles, activity score, Patella scores, EQ-5D, 6-minute walk time, and patient satisfaction.

RESULTS

Complete data were recorded for 98 posterior-stabilized implants and 97 BCS implants. Twelve patients had bilateral knee implants. There was no difference between the groups for any of the measures at either 1 or 2 years. At 2 years, knee flexion was 119 ± 0.16 and 120 ± 1.21 degrees for the posterior-stabilized and BCS implants, respectively, (mean, standard error, P = .538) and Oxford Knee Scores were 40.4 ± 0.69 and 40.0 ± 0.67 (P = .828), respectively. There were similar device-related AEs and revisions in each group (AEs 18 vs 22; P = .732; revisions 3 vs 4; P = .618).

CONCLUSION

There was no evidence of clinical superiority of one implant over the other at 2 years.

Evolution of TKA design

The use of Total Knee Arthroplasty (TKA) in treatment of chronic degenerative pathologies of the knee boasts of an experience of 50 years. During this period the collaboration between surgeons and engineers produced many developments in the design of the prosthesis. Today this procedure is safe and established even if in continuous development. The progress in technologies and the use of new materials let researches try again old-fashioned techniques from the past in order to be improved. This enthusiasm for those discovers is not always going hand to hand with scientific validation: many open questions remains Every different concept of the design tries to answer to special needs as the reach of the highest ROM, the reduction of pain and debris, articular geometry, the type of fixation, the modularity of augments and stems, the types of constraints,  knee kinematic and of course costs.

Partial versus Intact Posterior Cruciate Ligament-retaining Total Knee Arthroplasty: A Comparative Study of Early Clinical Outcomes

OBJECTIVE

Whether the entire posterior cruciate ligament (PCL) should be retained during cruciate-retaining total knee arthroplasty (CR TKA) is controversial. The goal of this study was to compare the early clinical outcomes of partial versus intact PCL-retaining TKA.

METHODS

Ninety-two patients who had undergone unilateral CR TKA from March 2012 to June 2013 were enrolled in this study. Forty-six of these patients were randomly selected to undergo intact PCL-retaining TKA (intact group), whereas the remaining 46 patients underwent tibial osteotomy together with anterolateral bundle and bone island resection (partial group). All operations were performed by a senior orthopedic surgeon and the PCL was released to some extent in both groups. After TKA, active and passive flexion and extension exercises of the knee and lower limb strength exercises were maintained until at least 3 months after surgery. Before surgery and 6, 12, and 24 months after surgery, range of motion, Knee Society Clinical Rating System scores (including clinical and functional scores of the knee) and maximum anteroposterior (AP) displacement of the knee at 30° and 90° of knee flexion were evaluated in both groups.

RESULTS

Fourteen patients were rejected from the final analysis because of loss to follow-up or development of complications. Thus, 40 patients from the partial group and 38 from the intact group were followed up for 24-41 months (mean 32.8 months). Knee functional scores were significantly higher in the intact than in the partial group (88.1 vs. 84.8 points) 24 months after surgery There were no significant differences in range of motion or knee clinical scores between the two groups at any time point. However, 12 and 24 months after surgery, the mean maximum AP displacement of the knee in 90° knee flexion was significantly greater in the partial than in the intact group (12 months: 6.3 vs. 5.7 mm; 24 months: 7.0 vs. 6.2 mm).

CONCLUSION

Double-bundle PCL plays an important role in maintaining knee stability; the entire PCL should therefore be retained during CR TKA.

Does Achieving High Flexion Increase Polyethylene Damage in Posterior-Stabilized Knees? A Retrieval Study

BACKGROUND

Increased range of motion to higher degrees of flexion following total knee arthroplasty has been postulated to increase implant damage and revision rates, even in designs modified to accommodate high flexion.

METHODS

We examined posterior-stabilized and high-flexion retrieved tibial inserts to look for differences in polyethylene surface damage with light microscopy and 3D deviation with laser scanning between inserts from patients who achieved a high degree of flexion (≥120° postoperatively) and inserts from patients who did not reach a high degree of flexion.

RESULTS

No differences were found in damage scores on the articular and backside surfaces, except for abrasion in the posterior articular regions, or in 3D deviations between patients who reached a high degree of flexion and patients who did not. These results were independent of the reason for revision.

CONCLUSION

In our series, reaching a high degree of flexion did not influence surface damage or 3D deviation of the polyethylene inserts.

Are the Current Outcome Measurement Tools Appropriate for the Evaluation of the Knee Status in Deep Flexion Range?

We determined whether current outcome measurement tools are appropriate for the evaluation of the knee status in deep flexion range after TKA. Patients (n = 604) with more than 120° of knee flexion were evaluated by Knee Society score, WOMAC, and high flexion knee score (HFKS). The appropriateness of measurement tools was analyzed by correlation analyses and group comparisons (group 1: 120°-129°, group 2: 130°-139°, group 3: 140°-150°). HFKS showed stronger correlation with knee flexion compared with other scores. While other scores only differentiated between groups 2 and 3, HFKS could differentiate among groups 1, 2 and 3. These findings suggest that employment of proper outcome measurement tool is needed to evaluate and differentiate the knee status in deep flexion range after TKA.

Comparison of High-Flexion and Conventional Implants in Total Knee Arthroplasty: A Meta-Analysis

Background

The purpose of this study was to evaluate whether high-flexion prostheses are superior to conventional prostheses after total knee arthroplasty (TKA).

Material/Methods

We searched the PubMed and Embase databases for randomized trials and cohort studies comparing high-flexion with conventional knee implants. The heterogeneity across studies was examined by I² and Cochran’s Q-tests. Then the overall weighted mean differences of range of motion (ROM) and knee functional scores were evaluated.

Results

A total of 16 trials involving 2643 knees met our inclusion criteria. The results revealed that high-flexion implants were superior to conventional implants in the improvement of range of motion (weighted mean difference, 2.92; 95% CI, 1.63–4.22; p<0.0001). The clear advantage of high-flex PS (posterior stabilized) as well as high-flex CR (cruciate retaining) implants was found in ROM when compared to PS implants (2.73; 95% CI, 1.27–4.20; p=0.0003) and CR implants (3.24; 95% CI, 0.28–6.20; p=0.003), respectively. However, there was no difference in Knee Society Scores (0.42; 95% CI, −0.60–1.43; p=0.42), Knee Society function (0.37; 95% CI, −1.48–2.22; p=0.70) and Hospital for Special Surgery scores (0.26; 95% CI, −0.47–1.00; p=0.48) between high-flexion and conventional groups.

Conclusions

The current meta-analysis revealed that high-flexion implants were superior to conventional implants in the improvement of ROM but not in functional outcome scores.

No Superiority of High-Flexion vs Standard Total Knee Arthroplasty: An Update Meta-Analysis of Randomized Controlled Trials

This meta-analysis was performed using a Cochrane systematic review approach to examine published data with an aim to clarify whether standard or high flexion prostheses increase the range of knee motion and clinical outcomes. 1778 patients from 17 randomized controlled trials were identified. No significant differences in the range of motion, weight-bearing flexion and hip functions scores were found between treatment groups. We also found no significant differences in complications with regard to revision, component loosening, deep infection, anterior knee pain, stiffness, post-operative bone fracture and post-operative patella clunk syndrome, but the high flexion prostheses group had a higher incidence of deep venous thrombosis. The results do not support the proposition that high flexion knee prostheses provide substantial clinical advantages over standard knee prostheses.

Patients achieved greater range of movement when using high-flexion implants

PURPOSE

NexGen Legacy Posterior Stabilized high-flexion prostheses (LPS-Flex) have been popularized as an alternative to NexGen standard prostheses (LPS) in total knee arthroplasty (TKA). Advocates of this new generation prosthesis suggest improved postoperative knee flexion. The purpose of this study was to summarize the best evidence for comparing the range of motion (ROM) and functional outcomes of LPS-Flex prostheses and LPS in TKA.

METHODS

Electronic databases were systematically searched to identify relevant randomized controlled trials (RCTs). The last date for our research was July 2014. Our search strategy was followed the requirements of the Cochrane Library Handbook. The methodological quality was assessed, and the data were extracted independently by two authors.

RESULTS

Nine studies that included 978 knees met our inclusion criteria for review. The results showed that there was larger postoperative ROM (1.62, 95% CI 0.52-2.72) in the LPS-Flex group than in the LPS group. There was not a statistically significant difference in the clinical functional scores and complications between the LPS-Flex group and the LPS group in TKA. The pooled mean differences were as follows: total KSS, -0.64 (95% CI -1.41 to 0.13); functional KSS, -0.53 (95% CI -1.51 to 0.45); HSS, 0.23 (95% CI -0.87 to 1.33); complications, 0.49 (95% CI 0.20-1.24); and radiolucent lines, 1.56 (95% CI 0.68-3.55).

CONCLUSIONS

The preliminary results indicate that the NexGen LPS-Flex prosthesis provides an alternative to the NexGen LPS prosthesis, with greater range of motion and without severe complications or radiographic outcomes. The clinical advantages were not shown in the KSS or the HSS. Thus, the selection of a high-flexion prosthesis should depend on the characteristics of the patient, particularly high motivation and poor preoperative ROM. The potential benefits in the medium- and long-term outcomes require confirmation by larger, multicenter and well-conducted RCTs.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

No clinical benefit of high-flex total knee arthroplasty. A meta-analysis of randomized controlled trials

The application of high-flex prosthesis in total knee arthroplasty (TKA) is an area of continuing debate. Thus, we conducted a meta-analysis of randomized controlled trials (RCTs). A literature search was performed in PubMed, EMBASE and the Cochrane database. 10 trials involving 1230 knee joints were eligible for our meta-analysis. No significant difference was observed between the two designs regarding postoperative range of flexion, clinical scores, quality of life outcomes, or complication rate. Moreover, the advantage of high-flex implants for patients with high preoperative range remained not statistically significant and high-flex design in NexGen system showed a marginal improvement in the postoperative range of flexion. Based on current findings, high-flex prosthesis did not appear to confer any benefit as compared to standard prosthesis.

Do patients really gain outcome benefits when using the high-flex knee prostheses in total knee arthroplasty? A meta-analysis of randomized controlled trials

The purpose of this study was to undertake a meta-analysis to evaluate whether patients really gain outcome benefits when using the high-flex (HF) prostheses in total knee arthroplasty (TKA) compared with standard (STD) implants. Only randomized controlled trials were included in this meta-analysis. After searching PubMed, Embase, Wed of Science and Cochrane Library, 1042 papers were identified and 18 trials were finally eligible for meta-analysis including 2069 knees (1906 patients). We found no statistically significant difference between the two designs in terms of ROM, knee scores (KSS, HSS, WOMAC, and SF-36), patients' satisfaction and complications. Hence there is currently no evidence to confirm that the use of high-flex prostheses in short-term is superior to the standard prostheses after total knee arthroplasty.

Standard versus high-flexion posterior stabilized total knee prostheses

This meta-analysis compared clinical outcomes between standard and high-flexion posterior-stabilized total knee prostheses to evaluate which type of total knee prosthesis was superior. Randomized, controlled trials published until October 2013 comparing standard and high-flexion posterior-stabilized total knee prostheses were reviewed. Methodologic quality was assessed with the Physiotherapy Evidence Database scale. After data extraction, the authors compared results with fixed effects or random effects models, depending on the heterogeneity of the included studies. Eight randomized, controlled trials involving 660 patients met the predetermined inclusion criteria. No statistically significant differences between patients undergoing standard and high-flexion posterior-stabilized total knee prostheses were noted in postoperative range of motion (ROM) (weighted mean difference, -1.43; 95% confidence interval [CI], -4.52 to 1.67; P=.37); flexion angle (weighted mean difference, 0.54; 95% CI, -3.75 to 4.84; P=.80); Knee Society Score (weighted mean difference, 0.92; 95% CI, -0.64 to 2.48; P=.25); Hospital for Special Surgery knee score (weighted mean difference, 0.57; 95% CI, -0.42 to 1.55; P=.26); or Knee Society function score (weighted mean difference, 1.00; 95% CI, -1.49 to 3.49; P=.43). No statistical difference was found between the 2 prosthesis types in complications, involving 21 cases in the standard group and 14 cases in the high-flexion group. The current findings confirm that high-flexion posterior-stabilized total knee prostheses are not superior to standard prostheses in terms of ROM, flexion angle, knee scores, or complications with 5 years or less of follow-up.

High-flexion posterior-substituting versus cruciate-retaining prosthesis in total knee arthroplasty: functional outcome, range of motion and complication comparison

PURPOSE

Currently, a high-flexion cruciate-retaining knee prosthesis has been designed to allow greater advantage after total knee arthroplasty (TKA). The present study was conducted to compare functional outcome, range of motion (ROM) as well as complications in subjects who underwent either a high-flexion cruciate-retaining (HFCR, Group I) or a high-flexion posterior-substituting (HFPS, Group II) prosthesis TKA.

METHODS

Thirty-four subjects which had TKA with HFCR prosthesis and thirty-three subjects which had TKA with HFPS prosthesis were enrolled in our study and were assessed preoperatively and at 24 months postoperatively. For functional outcome comparison, Hospital for Special Surgery Score (HSSS), Knee Society Score (KSS, including the Mean Knee Score and the Mean Function Score) as well as SF12 Score (including Mental Health Score and Physical Health Score) were measured. For ROM comparison, the arcs of maximal non-weight-bearing passive flexion and weight-bearing flexion were detected, and the number of knees which allowed patients to kneel and sit cross-legged in comfort was determined. For complication comparison, wound necrosis/discharge, anterior knee pain, dislocation, radiolucent lines as well as osteolysis were investigated.

RESULTS

At 24-month follow-up, no significant difference in functional outcome between the two groups was detected. The average maximal non-weight-bearing flexion was 136.2° for the knees in Group I and 135.1° for the knees in Group II (P > 0.05). The average weight-bearing flexion was 123.2° for the knees in Group I and 129.8° for the knees in Group II (P > 0.05). No significant difference, with regard to the number of knees that allowed kneeling and sitting cross-legged, was detected. Comparisons of postoperative complications between the two groups did not yield a significant difference.

CONCLUSIONS

Our study demonstrated no advantage of the high-flexion cruciate- retaining TKA over high-flexion posterior-substituting TKA with regard to functional outcome, range of motion as well as complications at short-term follow-up. However, longer follow-up is necessary to confirm whether these results are sustained.

Patient satisfaction after posterior-stabilized total knee arthroplasty: a functional specific analysis

BACKGROUND

Despite the success of total knee arthroplasty (TKA) in treating end-stage knee arthritis, 11% to 19% of patients are dissatisfied with the outcome of their surgery. In this study we investigated how satisfied overall patients are with the outcome of posterior stabilized TKA and what particular functional deficits or residual symptoms cause the most dissatisfaction for patients after surgery.

METHODS

Using patient-completed validated questionnaires, we retrospectively analyzed data for 1013 posterior-stabilized TKAs performed in 748 Chinese patients regarding the overall satisfaction with surgery and the importance ranking of each of 15 specific functions and residual symptoms.

RESULTS

Our data demonstrate an overall satisfaction rate of 87.4%. Satisfaction percentages ranged from 45.0% to 89.0%. The top 6 dissatisfactory items were sitting with legs crossed (dissatisfaction rate of 55.0%), squatting (51.7%), walking fast or jogging (45.4%), knee clunking (34.5%), abnormal feeling in knee (31.2%), and climbing stairs (28.2%). The top 6 important functions or issues were pain relief, walking on flat ground, climbing stairs, ability to return to household work, decreased limping, and squatting.

CONCLUSIONS

Approximately 1 in 8 patients was dissatisfied with overall outcome. Patients were most dissatisfied with climbing stairs and squatting, functions that they considered most important.

Bicruciate substituting design does not improve maximal flexion in total knee arthroplasty: a randomized controlled trial

BACKGROUND

An important factor in the functional results after total knee arthroplasty is the achieved maximal flexion. The main purpose of this study was to compare the maximal knee flexion one year after surgery in patients who received either the bicruciate substituting knee system or the conventional posterior stabilized system.

METHODS

In a prospective randomized controlled trial, 124 patients presenting with osteoarthritis received the bicruciate substituting or the conventional posterior stabilized prosthesis. The primary outcome was the maximum flexion angle at one year postoperatively on a lateral radiograph made with the supine patient using manual force to bend the knee. Secondary outcomes were active flexion (lying and standing), the Knee Society Score, the Patella Scoring System score, the University of California Los Angeles score, the number and type of adverse device effects, and visual analog scale satisfaction up to two years postoperatively. The outcome measures of both groups were compared using one-sided t tests and non-parametric alternatives, with a significance level of p < 0.05.

RESULTS

No significant differences between the two groups were observed in maximal flexion on radiographs and in active flexion at baseline. The median maximal flexion on radiographs was 127° (range, 83° to 150°) for the bicruciate substituting group and 125° (range, 74° to 145°) for the conventional posterior stabilized group. The two groups showed comparable two-year results with respect to the Knee Society Score, the Patella Scoring System, the University of California Los Angeles score, and visual analog scale satisfaction. In the bicruciate substituting group, forty-one adverse device effects in twenty-six patients were reported, including three total system revisions and fourteen manipulations under anesthesia, compared with the conventional posterior stabilized group, in which sixteen adverse device effects were observed in thirteen patients, including six manipulations under anesthesia (p = 0.012).

CONCLUSIONS

Patients who receive a bicruciate substituting system compared with those who receive a conventional posterior stabilized system have comparable knee flexion characteristics and clinical and functional outcomes but more complications by two years after total knee arthroplasty.

LEVEL OF EVIDENCE

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

Is range of motion after cruciate-retaining total knee arthroplasty influenced by prosthesis design? A prospective randomized trial

Improvement in knee flexion is a major expectation for many patients undergoing total knee arthroplasty (TKA). One hundred and twenty two patients were randomized to receive a cruciate-retaining standard or high-flexion TKA. Range of motion (ROM) and functional outcomes were assessed. The high flexion implants had a greater intraoperative ROM than standard implants. The mean flexion preoperatively, intraoperatively and at the one year follow-up was 107.4°, 123.0° and 108.9° in the standard group and 109.9°, 129.1° and 109.7° in the high-flexion TKA group. These differences were not significant preoperatively and at follow-up, but intraoperatively (P < 0.001). In multivariate analysis preoperative knee flexion was the only significant factor influencing knee flexion at follow-up. No differences in the Knee Society Score or SF 36 were observed.

Current concepts in knee replacement: features and imaging assessment

OBJECTIVE

This article reviews current concepts of knee replacement. Features of traditional and new prosthetic designs, materials, and surgical techniques are discussed. Normal and abnormal postoperative imaging findings are illustrated. Complications are reviewed and related to the current understanding about how and why these failures occur.

CONCLUSION

It is well known that after knee replacement, patients with complications may be asymptomatic, and, for this reason, assessment of postoperative imaging is important. The foundation of radiologic interpretation of knee replacement is knowledge of the physiologic purpose, orthopedic trends, imaging findings, and complications.

Does flexion of the femoral implant in total knee arthroplasty increase knee flexion: a randomised controlled trial

INTRODUCTION

Prosthetic and operative modifications in total knee arthroplasty (TKA) have been proposed to maximise post-operative knee flexion as it is essential in routine functional activities.

METHODS

We performed a double blind randomised controlled trial to compare clinical outcomes of primary cruciate-retaining TKA for osteoarthritis with the femoral component implanted in either 4° flexion in the sagittal plane (F) or in a neutral position (C). The primary outcome of knee flexion and secondary outcomes knee extension, quadriceps strength, WOMAC, SF-12v2, timed stand test, stair climb test and satisfaction were assessed at 1 year. Knee flexion and extension were also assessed intra-operatively. Implant flexion was measured from true lateral radiographs.

RESULTS

Thirty-nine participants (40 knees) were recruited, 20 knees per group. Three subjects from the control group and two from the flexed group were lost to 1 year follow-up but numbers were sufficient to satisfy the sample size calculation. Significant differences were found between the groups in knee flexion (F: 113.6±8.8° pre-operative, 122.4±6.0° intra-operative, 110.2±7.5° 1 year, C: 117.4±11.7°, 117.4±7.6°, 103.5±10.7°. p=0.031) and mental component score of the SF12-v2 (F 53.3±13.2, C 61.1±7.3, p=0.009) but there were no significant differences in other outcomes and patients were equally satisfied.

CONCLUSION

Flexing the femoral implant in this cruciate retaining TKA system provided a significant difference in knee flexion compared to a neutral position. The improvement appears to occur predominantly at surgery and was not associated with a clinical or functional benefit at 1 year. (ACTRN12606000325505).

LEVEL OF EVIDENCE

Level 1; randomised controlled trial.

Brief followup report: Does high-flexion total knee arthroplasty allow deep flexion safely in Asian patients?

BACKGROUND

The long-term survivorship of TKA in Asian countries is comparable to that in Western countries. High-flexion TKA designs were introduced to improve flexion after TKA. However, several studies suggest high-flexion designs are at greater risk of femoral component loosening compared with conventional TKA designs. We previously reported a revision rate of 21% at 11 to 45 months; this report is intended as a followup to that study.

QUESTIONS/PURPOSES

Do implant survival and function decrease with time and do high-flexion activities increase the risk of premature failure?

METHODS

We prospectively followed 72 Nexgen LPS-flex fixed TKAs in 47 patients implanted by a single surgeon between March 2003 and September 2004. We determined the probability of survival using revision as an end point and compared survival between those who could and those who could not perform high-flexion activities. Minimum followup was 0.9 years (median, 6.5 years; range, 0.9-8.6 years).

RESULTS

Twenty-five patients (33 knees) underwent revision for aseptic loosening of the femoral component at a mean of 4 years (range, 1-8 years). The probability of revision-free survival for aseptic loosening was 67% and 52% at 5 and 8 years, respectively. Eight-year cumulative survivorship was lower in patients capable of squatting, kneeling, or sitting crosslegged (31% compared with 78%). There were no differences in the pre- and postoperative mean Hospital for Special Surgery scores and maximum knee flexion degrees whether or not high-flexion activities could be achieved.

CONCLUSIONS

Overall midterm high-flexion TKA survival in our Asian cohort was lower than that of conventional and other high-flexion designs. This unusually high rate of femoral component loosening was associated with postoperative high-flexion activities.

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.

The 2012 Mark Coventry award: a retrieval analysis of high flexion versus posterior-stabilized tibial inserts

BACKGROUND

High flexion (HF) implants were introduced to increase ROM and patient satisfaction, but design changes to the implant potentially have deleterious effects on polyethylene wear. It is unclear whether the HF implants affect wear.

QUESTIONS/PURPOSES

We therefore examined whether the design changes between HF and posterior-stabilized (PS) tibial inserts would affect overall damage or damage on their articular surface, backside, and tibial post and whether flexion angle achieved related to damage.

METHODS

We matched 20 retrieved HF inserts to 20 retrieved PS inserts from the same implant system on the basis of duration of implantation, body mass index, and age. Inserts were divided into 16 zones and a microscopic analysis of surface damage was carried out. Five inserts were scanned using micro-CT to further quantify instances of severe post notching. We determined overall damage with a scoring system.

RESULTS

We found greater backside and post damage in the HF group but no difference in the articular surface or overall damage scores. Backside and post damage scores correlated to flexion angle in the HF group. There was no flexion/damage correlation in the PS group. Notch depths around the post in both groups ranged from 0.6 to 1.9 mm.

CONCLUSIONS

HF inserts are more susceptible to post damage, possibly as a result of higher contact stresses from greater flexion. The increased backside damage was unexpected because the two groups have the same tibial component, locking mechanism, and sterilization method.

CLINICAL RELEVANCE

The introduction of a highly crosslinked HF insert will require close scrutiny as a result of the potential for post damage demonstrated in this series.

Factors affecting range of motion in total knee arthroplasty using high flexion prosthesis: A prospective study

BACKGROUND

High flexion implants have been reported to provide better range of motion (ROM). The few studies analyzing the factors affecting the ROM are scarce. This study aims to find the factors that affect ROM when using a high flex knee design (INDUS knee).

MATERIALS AND METHODS

Two hundred and fifty three consecutive patients of total knee arthroplasty (TKA) done by using INDUS knee prosthesis between Sept 2008 and Sept 2009 were included in the study. The cases with osteoarthritis (OA) and Rheumatoid arthritis (RA) were included in study. 5 patients were lost to followup and 248 patients (267 knees, 19 bilateral, 221 OA, and 46 RA) were analyzed for the following factors - sex, age, body mass index (BMI), preoperative ROM, flexion deformity, preoperative total knee score and functional score, time of tourniquet release and patella resurfacing. Subgroup classification using above factors was performed and statistical analysis of effect of all the above factors on final knee ROM was done. Assessment was done preoperatively and at 3 months, 6 months and 1 year postoperatively. The final outcome evaluation was done at one year followup.

RESULTS

The mean age was 68.2 years (range 40-89 years) with 79 males and 189 females. The mean knee range improved from 97.62 ± 11° to 132 ± 8°. Factors that positively affect ROM of INDUS knee prosthesis at the end of 1 year were preoperative ROM, total knee score and functional score, and diagnosis of osteoarthritis, whereas BMI, preoperative flexion deformity has a negative influence on final flexion at the end of 1 year. Age and gender of the patients, patella resurfacing, and use of two different tourniquet protocols did not affect the final outcome.

CONCLUSION

Preoperative ROM and preoperative functional status are the most important factors affecting final range. Patients should be counseled accordingly and made to understand these factors.

Does a mobile-bearing, high-flexion design increase knee flexion after total knee replacement?

This prospective randomised controlled double-blind trial compared two types of PFC Sigma total knee replacement (TKR), differing in three design features aimed at improving flexion. The outcome of a standard fixed-bearing posterior cruciate ligament-preserving design (FB-S) was compared with that of a high-flexion rotating-platform posterior-stabilised design (RP-F) at one year after TKR. The study group of 77 patients with osteoarthritis of the knee comprised 37 men and 40 women, with a mean age of 69 years (44.9 to 84.9). The patients were randomly allocated either to the FB-S or the RP-F group and assessed pre-operatively and at one year post-operatively. The mean post-operative non-weight-bearing flexion was 107° (95% confidence interval (CI) 104° to 110°)) for the FB-S group and 113° (95% CI 109° to 117°) for the RP-F group, and this difference was statistically significant (p = 0.032). However, weight-bearing range of movement during both level walking and ascending a slope as measured during flexible electrogoniometry was a mean of 4° lower in the RP-F group than in the FB-S group, with 58° (95% CI 56° to 60°) versus 54° (95% CI 51° to 57°) for level walking (p = 0.019) and 56° (95% CI 54° to 58°) versus 52° (95% CI 48° to 56°) for ascending a slope (p = 0.044). Further, the mean post-operative pain score of the Western Ontario and McMaster Universities Osteoarthritis Index was significantly higher in the RP-F group (2.5 (95% CI 1.5 to 3.5) versus 4.2 (95% CI 2.9 to 5.5), p = 0.043). Although the RP-F group achieved higher non-weight-bearing knee flexion, patients in this group did not use this during activities of daily living and reported more pain one year after surgery.

Wear of moderately cross-linked polyethylene in fixed-bearing total knee replacements

Cross-linked polyethylene has been introduced into total joint replacement to improve wear resistance. Although the performance of highly cross-linked polyethylene is well documented clinically and experimentally for total hip replacements, the reduction in mechanical properties with increasing irradiation is of concern for application to total knee replacement. The aim of this study was to investigate the wear performance of a moderately cross-linked polyethylene material in a fixed-bearing total knee replacement. The study was conducted using two femoral geometries, a conventional cruciate-retaining femoral and a high-flexion femoral geometry. The femoral geometry appeared to have no effect on the wear of the knee replacement under standard gait conditions. A significant reduction in wear volume was measured with the moderately cross-linked polyethylene compared with the conventional polyethylene over a six-million-cycle wear study. This study indicates the use of a moderately cross-linked polyethylene in a fixed-bearing total knee replacement may provide a low wearing option for total knee replacement.

[Total knee arthroplasty for rheumatoid arthritis]

A total of 150,000 primary total knee arthroplasties are performed in Germany each year. There is only a limited amount of evidence-based data available on possible surgery-related differences between osteoarthritis (OA) and rheumatoid arthritis (RA) of the knee joint. The following review summarizes the recent literature on total knee arthroplasty with a focus on special features of RA patients.