High-flexion posterior-stabilized total knee prosthesis: is it worth the hype?

Patellar resurfacing and kneeling ability after total knee arthroplasty: a systematic review

BACKGROUND

Difficulty kneeling following total knee arthroplasty (TKA) remains highly prevalent, and has cultural, social, and occupational implications. With no clear evidence of superiority, whether or not to resurface the patella remains debatable. This systematic review examined whether resurfacing the patella (PR) or not (NPR) influences kneeling ability following TKA.

METHODS

This systematic review was conducted by following PRISMA guidelines. Three electronic databases were searched utilizing a search strategy developed with the aid of a department librarian. Study quality was assessed using MINROS criteria. Article screening, methodological quality assessment and data extraction were performed by two independent authors, and a third senior author was consulted if consensus was not reached.

RESULTS

A total of 459 records were identified, with eight studies included in the final analysis, and all deemed to be level III evidence. The average MINORS score was 16.5 for comparative studies and 10.5 for non-comparative studies. The total number of patients was 24,342, with a mean age of 67.6 years. Kneeling ability was predominantly measured as a patient-reported outcome measure (PROM), with two studies also including an objective assessment. Two studies demonstrated a statistically significant link between PR and kneeling, with one demonstrating improved kneeling ability with PR and the other reporting the opposite. Other potential factors associated with kneeling included gender, postoperative flexion, and body mass index (BMI). Re-operation rates were significantly higher in the NPR cohort whereas PR cohorts had higher Feller scores, patient-reported limp and patellar apprehension.

CONCLUSION

Despite its importance to patients, kneeling remains not only under-reported but also ill-defined in the literature, with no clear consensus regarding the optimum outcome assessment tool. Conflicting evidence remains as to whether PR influences kneeling ability, and to clarify the situation, large prospective randomized studies are required.

Surgery-related predictors of kneeling ability following total knee arthroplasty: a systematic review and meta-analysis

Purpose

Kneeling ability is among the poorest outcomes following total knee arthroplasty (TKA). The purpose of this meta-analysis was to: (1) quantify kneeling ability after TKA; (2) identify surgical approaches and prosthesis designs that improve kneeling ability following TKA; and (3) quantify the effectiveness of these approaches.

Methods

We performed a systematic review in accordance with the PRISMA guidelines of multiple medical databases. Data relating to demographics, TKA technique, prosthesis design, and kneeling-specific outcomes were extracted. Comparative outcomes data were pooled using a random effects model.

Results

Thirty-six studies met the eligibility criteria. The proportion of patients able to kneel increased with longer follow-up (36.8% at a minimum of 1 year follow-up versus 47.6% after a minimum of 3 years follow-up, p < 0.001). The odds of kneeling were greater for patients undergoing an anterolateral incision compared with an anteromedial incision (OR 3.0, 95% CI 1.3–6.9, p = 0.02); a transverse incision compared with a longitudinal incision (OR 3.5, 95% CI 1.4–8.7, p = 0.008); and a shorter incision compared with a longer incision (OR 8.5, 95% CI 2.3–30.9, p = 0.001). The odds of kneeling were worse for a mobile prosthesis compared with a fixed platform design (OR 0.3, 95% CI 0.1–0.7, p = 0.005).

Conclusion

A large majority of patients are unable to kneel following TKA, although the ability to kneel improves over time. This evidence may facilitate preoperative patient counseling. Variations in choice of incision location and length may affect ability to kneel; however, high-quality randomized trials are needed to corroborate our findings.

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.

Shape is only a weak predictor of deep knee flexion kinematics in healthy and osteoarthritic knees

Tibiofemoral shape influences knee kinematics but little is known about the effect of shape on deep knee flexion kinematics. The aim of this study was to examine the association between tibiofemoral joint shape and kinematics during deep kneeling in patients with and without osteoarthritis (OA). Sixty-one healthy participants and 58 patients with end-stage knee OA received a computed tomography (CT) of their knee. Participants completed full flexion kneeling while being imaged using single-plane fluoroscopy. Six-degree-of-freedom kinematics were measured by registering a three-dimensional (3D)-static CT onto 2D-dynamic fluoroscopic images. Statistical shape modeling and bivariate functional principal component analysis (bfPCA) were used to describe variability in knee shape and kinematics, respectively. Random-forest-regression models were created to test the ability of shape to predict kinematics controlling for body mass index, sex, and group. The first seven modes of the shape model up to three modes of the bfPCAs captured more than 90% of the variation. The ability of the random forest models to predict kinematics from shape was low, with no more than 50% of the variation being explained in any model. Furthermore, prediction errors were high, ranging between 24.2% and 29.4% of the data. Variations in the bony morphology of the tibiofemoral joint were weakly associated with the kinematics of deep knee flexion. The models only explained a small amount of variation in the data with high error rates indicating that additional predictors need to be identified. These results contribute to the clinical understanding of knee kinematics and potentially the expectations placed on high-flexion total knee replacement design.

Posterior-stabilized versus cruciate-retained implants for total knee arthroplasty: a meta-analysis of clinical trials

AIM

A meta-analysis comparing the outcomes of patients undergoing cruciate retaining (CR) versus posterior stabilized (PS) in primary total knee arthroplasty was performed. The outcomes of interest were the Knee Society Rating System, clinical (KSCS) and functional (KSFS) subscales, joint range of motion (ROM), surgical duration and further complications (anterior knee pain, instability and revision rate).

MATERIALS AND METHODS

The search was conducted in July 2018, accessing the following databases: Cochrane Systematic Reviews, Scopus, PubMed, EMBASE, CINAHL, AMED and Google Scholar. We included only clinical trials level of evidence I and II. During the statistical analysis, we excluded all the studies that affect negatively the I² test, in order to achieve more reliable results. For the methodological quality assessment we referred to the PEDro score. The risk of publication's bias was evaluated by the funnel plots across all the comparisons.

RESULTS

The PEDro score reported a good methodological quality assessment. The funnel plot detected a very low risk of publication's bias. We included in this study 36 articles, counting a total of 4052 patients and 4884 procedures. The mean follow-up term for both groups was 3.39 years. The ROM resulted in an overall estimate effect of 2.18° in favor of the PS group. The overall WOMAC showed a result in favor of the PS group. The overall estimate effect of the KSCS was 0.02% higher in the CR group. The KSFS showed an overall estimate effect of 2.09% in favor of the PS group. Concerning the surgical duration, the estimate effect resulted in 6.87 min shorter in the CR group. No differences were reported across the two groups regarding anterior knee pain, knee joint instability or revision rate.

CONCLUSION

Both the prosthetic implants provided to be a safety and feasible solution to treat end-stage knee joint degeneration. The PS implants reported improvements in the knee range of motion and a prolongation of the surgical time. No clinically relevant dissimilarities concerning the analyzed scores were evidenced. No statistically significant relevant differences in complications were detected.

Is Achieving High Flexion Necessary for Satisfaction after Total Knee Arthroplasty in Indian Patients?

BACKGROUND

Total knee arthroplasty (TKA) is a very successful operation for the treatment of end-stage arthritis of the knee joint. In spite of improvement in surgical technique, implant design, postoperative pain management, and rehabilitation, some patients are not satisfied with the outcome of the surgery. It is believed that high-flexion (H-F) activities such as cross-legged sitting and squatting are necessary for satisfaction after TKA in Indian patients due to cultural and social reasons. This has led to the development and marketing of implant designs allowing H-F after TKA without strong evidence in the literature.

MATERIALS AND METHODS

We carried out a retrospective study to determine the level of satisfaction in 74 patients operated for 120 TKA over a 5 year period. This was determined on the basis of a satisfaction questionnaire which included questions to assess satisfaction regarding pain relief and ability to perform routine daily activities and high knee flexion activities such as squatting and cross-legged sitting.

RESULTS

Out of a total of 74 patients, 69 patients were overall satisfied with their TKA. Out of these, only 5 patients could squat or sit in a cross-legged position. Majority of the patients were satisfied with the pain relief and improvement in their capacity to work provided by TKA.

CONCLUSIONS

Ability to perform H-F activities after TKA is not a necessary prerequisite for satisfaction in Indian patients. Implant designs allowing H-F should be used in a selected group of patients with good preoperative knee flexion and specific requirements.

Two- to Four-Year Follow-up Results of Total Knee Arthroplasty Using a New High-Flexion Prosthesis

Purpose

The purpose of this study was to evaluate minimum 2-year follow-up results of total knee arthroplasty (TKA) performed using a new high-flexion prosthesis design (LOSPA).

Materials and Methods

The 2- to 4-year results of 191 consecutive TKAs (177 patients) with the LOSPA posterior-stabilized prosthesis were evaluated. The patients were assessed clinically and radiographically using the Knee Society scoring system (KSS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

Results

The mean range of motion (ROM) increased significantly from 117.4° (range, 75° to 140°) preoperatively to 126.7° (range, 80° to 144°) postoperatively (p<0.001). The mean KSS and WOMAC scores improved significantly from 121.4 (range, 42 to 185) and 56.1 (range, 23 to 88) preoperatively to 174.0 (range, 130 to 200) and 16.4 (range, 0 to 85) postoperatively, respectively (both, p<0.001). One knee required revision for deep infection. No knee had aseptic loosening or osteolysis. Radiolucent lines were noted in 15 knees (7.9%).

Conclusions

The new high-flexion total knee prosthesis resulted in no early aseptic loosening of the component and improved postoperative ROM comparable to other high-flexion TKA prostheses at 2- to 4-year follow-ups.

Posterior Stabilized Polyethylene Inserts in Total Knee Arthroplasty: A Retrieval Study Comparing Conventional to High-Flexion Designs

BACKGROUND

High-flex (HF) total knee arthroplasties are modified posterior-stabilized (PS) implants designed to accommodate greater flexion.

METHODS

We examined differences between HF and PS retrieved tibial inserts with regard to polyethylene surface damage. Twenty HF inserts from each of 3 manufacturers were matched using patient demographics with 20 PS inserts from the same manufacturers. Ranges of motion between matched patients were not different.

RESULTS

Based on subjective damage scores, no differences were detected between HF and PS groups. Differences were found, however, among manufacturers, consistent with design approaches taken for PS and HF implants.

CONCLUSION

In our series, high flexion did not influence damage, although this was likely influenced by the fact that few HF patients in our study had larger range of motions than their PS counterparts.

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.

Performing high flexion activities does not seem to be crucial in developing early femoral component loosening after high-flexion TKA

Background

It is still unclear whether high flexion (HF) activities correlated with the early loosening of the femoral component and whether HF activities are possible. We investigated what is the capability for performing various HF activities, and whether high flexion activities increase the chance of aseptic loosening after HF-TKA.

Methods

We retrospectively analysed 260 patients who underwent HF-TKA using the NexGen LPS Flex between 2001 and 2009. The mean follow-up was 6.7 years (range, 5–13). We evaluated range of motion, Knee Society scores, WOMAC, and serial radiographs for aseptic loosening. Responses to questions on individual HF activities were recorded on 5-point Likert scales based on difficulty (0–4). Patients were divided two groups based on their responses to squatting and kneeling, which were important weight-bearing HF activities in Asian population (HF group vs. non-HF group) for comparisons of aseptic loosening and clinical outcomes.

Results

More than 80 % of patients positively responded for various HF activities. The capability of HF activities showed that cross-legged sitting, squatting, and kneeling were 97.7, 51.1 and 52.7 % at the latest follow-up, respectively. Aseptic loosening was identified in two tibial components (0.8 %) but none in femoral components in non-HF group. There was no significant difference of aseptic loosening based on HF activities (0.8% vs. 0%, p = 0.063).

Conclusions

The results of this study suggest that HF activities do not seem to be associated with aseptic loosening of femoral component after HF-TKA.

No difference between standard and high flexion cruciate retaining total knee arthroplasty: a prospective randomised controlled study

PURPOSE

The purpose of this prospective, randomised, double-blind study was to test the hypotheses that patients with high-flexion total knee arthroplasty (TKA) have (1) a wider/greater range of motion (ROM) post-operatively and (2) higher levels of knee society score (KSS) and WOMAC score post-operatively compared to standard TKA.

METHODS

In this study, 28 high flexion with 31 standard TKAs were compared. We measured ROM, pre-operatively, on day 3, 7, 28, and after 6 and 36 months post-operatively as well as KSS and WOMAC score pre-operatively, on day 28 and after 6 and 36 months post-operatively.

RESULTS

No statistically significant differences were found between both groups with regard to the target parameters. The mean ROM was 113° (range 80°-140°, SD 13.4°) in the control group (standard TKA) and 117° (range 90°-140°, SD 12.3) in the study group (high-flexion TKA) at 36 months follow-up [p = not significant (n.s.)]. The KSS pre-operatively was 38.2 (range 8-64, SD 15.8) in the control group and 45.9 (range 8-74, SD 16.0) in the study group (n.s.) increasing to 157.6 in the control group and 156.7 in the study group (p = n.s) at 36 months follow-up.

CONCLUSION

This study could not confirm significant benefits of high-flexion TKA compared to standard TKA with regard to ROM and higher levels of KSS and WOMAC score.

LEVEL OF EVIDENCE

I.

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.