A prospective randomised double-blind study of functional outcome and range of flexion following total knee replacement with the NexGen standard and high flexion components

Is Highly Cross-Linked Polyethylene Safe for Use in High-Flexion Posterior Stabilized Total Knee Arthroplasty?

BACKGROUND

Application of highly cross-linked polyethylene (HXLPE) to a posterior cruciate-substituting total knee arthroplasty (TKA) might add the risk of fracture and failure of the tibial polyethylene insert. The purpose of this study is to evaluate the long-term (up to 19 years) clinical and radiographic results of posterior cruciate-substituting TKAs with HXLPE or conventional polyethylene.

METHODS

This study analyzed the results of 1,217 patients (444 men and 773 women; mean age of 65 ± 7 years, range, 31-85) (2,434 knees) who had received a NexGen LPS-Flex prosthesis with a conventional tibial insert in one knee and the same prosthesis with an HXLPE tibial insert in the contralateral knee. The mean duration of follow-up was 17 years (range, 15-19).

RESULTS

The 2 groups did not differ significantly (P > .05) with regard to the clinical and radiographic results. No knee in either group had a fracture of the tibial polyethylene post or failure of the locking mechanism of the tibial polyethylene insert or osteolysis. Twenty-eight knees (2.3%) in the HXLPE group and 26 knees (2.1%) in the conventional polyethylene group were revised. The estimated survival rate at 17 years was 97.7% in the HXLPE group and 97.9% in the conventional polyethylene group.

CONCLUSION

The data suggest that clinical and radiographic findings at a mean of 17 years after posterior cruciate-substituting TKA are the same for patients treated with HXLPE and those treated with conventional polyethylene.

Effect of the knee replacement surgery on activity level based on ActivPAL: a systematic review and meta-analysis study

BACKGROUND

The knee replacement (KR) surgery aims to restore the activity level and reduce the risk of experiencing disabilities. The outcomes of this surgery are evaluated mainly with subjective tools or low validity objective tools. However, the effect of the surgery on activity level using high validity objective accelerometer is still in question.

METHODS

A systematic review and meta-analysis were conducted to evaluate the benefit of KR surgery alone to enhance physical activity recommendations based on high validity accelerometer. Two independent reviewers evaluated five electronic databases (Cochrane-Central-Register-of-Controlled Trials, EMBASE, PubMed, Web of Science, and Scopus) to find relative studies between January 2000 and October 2021. The quality assessments and risk of bias assessments were examined.

RESULTS

Three articles were included with 202 participants (86 males, 116 females), with an average age of 64 years and an average 32 kg/m2 body mass index. The results found that the number of steps was significantly improved up to 36.35 and 45.5% after 6-months and 1-year of the surgery, respectively. However, these changes did not meet the recommended activity level guideline and could be related to the patients' health status and their activity level before the surgery. No significant changes were seen in sedentary time, standing time, and upright time after 6-months and 1-year follow-ups. Heterogeneity among studies was low to moderate (0-63%).

CONCLUSION

Knee replacement surgery is an effective treatment for improving patients' quality of life with severe knee injuries. However, various factors impact the success of surgical and achieving maximum benefit of the surgery. One factor, sedentary time, can be reduced by implementing pre-and post-surgery exercise or physical activity recommendations. Further studies are needed to understand the benefit of surgery with or without rehabilitation assessed using high validity monitors.

The influence of alignment in long-term functional outcome of total knee arthroplasty

BACKGROUND

This study aimed to analyze long-term survival rate and clinical outcomes of a NexGen LPS knee system. The effect of component alignment parameters on clinical scores and patient satisfaction was also investigated.

METHODS

Between June 2002 and January 2010, 204 knees of 152 patients underwent total knee arthroplasty with NexGen LPS-Flex knee system with fix bearings. The mean follow-up was 13.2 (range, 10 to 18 years). The relationship between radiologic and clinical results was investigated with component angles. Outlier angles were determined according to cutoff values of alpha, beta, gamma, and delta angles on the radiographs taken immediately after the operation. Knees were classified based on existing outliers they have as "No Outliers" (Group 1), "Single Outliers" (Group 2), and "Multiple Outliers" (Group 3).

RESULTS

Revision surgery was required for ten patients, and the overall survival rate was 95.1% at the last follow-up. "Single Outliers" did not show a clinically significant difference in functional scores compared to the "No Outliers" group. However, KSKS and FJS-12 were significantly lower in "Multiple Outliers" knees (p: 0.039 and 0.019, respectively).

CONCLUSION

NexGen LPS-Flex knee system has satisfactory results with 95.1% implant survival in 13.2 years. FJS-12 measurements at the end of the follow-up demonstrate a favourable result of the fixed bearing design. On two plane X-ray evaluations, components malaligned with two or more outliers in the same knee deteriorate patient satisfaction and clinical results.

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.

A high degree of knee flexion after TKA promotes the ability to perform high-flexion activities and patient satisfaction in Asian population

Background

This study investigated whether achieving a higher degree of knee flexion after TKA promoted the ability to perform high-flexion activities, as well as patient satisfaction and quality of life.

Methods

Clinical data on 912 consecutive primary TKA cases involving a single high-flexion posterior stabilized fixed-bearing prosthesis were retrospectively analyzed. Demographic and clinical data were collected, including knee flexion angle, the ability to perform high-flexion activities, and patient satisfaction and quality of life.

Results

Of the cases, 619 (68%) achieved > 130° of knee flexion after TKA (high flexion group). Knee flexion angle and clinical scores showed significant annual changes, with the maximum improvement seen at 5 years and slight deterioration observed at 10 years postoperatively. In the high flexion group, more than 50% of the patients could not kneel or squat, and 35% could not stand up from on the floor. Multivariate analysis revealed that > 130° of knee flexion, the ability to perform high-flexion activities (sitting cross-legged and standing up from the floor), male gender, and bilateral TKA were significantly associated with patient satisfaction after TKA, while the ability to perform high-flexion activities (sitting cross-legged and standing up from the floor), male gender, and bilateral TKA were significantly associated with patient quality of life after TKA.

Conclusions

High knee flexion angle (> 130°) after TKA increased the ease of high-flexion activities and patient satisfaction. The ease of high-flexion activities also increased quality of life after TKA in our Asian patients, who frequently engage in these activities in daily life.

Influences of treadmill speed and incline angle on the kinematics of the normal, osteoarthritic and prosthetic human knee

The objective of this paper is to measure and to study the influence of the treadmill speed and incline angle on the kinematics of flexion-extension angles of the human knee joints during 23 tests of walking overground and on plane and inclined treadmill performed by a sample of 14 healthy subjects and during of seven tests performed by a sample of five patients suffering of knee osteoarthritis (KOA), before and three months after the total knee replacement (TKR) surgery. The medium cycles computed and plotted for all experimental tests performed by the healthy subjects' sample and for the osteoarthritic (OA) patients' sample before and after TKR surgery are compared and conclusions are formulated.

Is high flexion total knee arthroplasty a rewarding procedure? An updated meta-analysis of prospective randomized controlled trials

INTRODUCTION

The aim of this study is to provide an updated meta-analysis comparing the benefits and clinical outcomes between high flexion (HF)-TKA and standard (S)-TKA.

MATERIALS AND METHODS

A detailed database analysis was carried out using Web of Science, PubMed, EMBASE, Cochrane Library, MEDLINE and Clinicaltrial.gov, to identify eligible studies. The meta-analysis and sensitivity analysis were performed using Review Manager 5.3 software and STATA 12.0.

RESULTS

Twenty-two randomized control trials (RCTs), including 2841 patients and 4268 knees, were eligible for the meta-analysis. The pooled results of subgroup analysis reveal that there was significant difference between HF-TKA and S-TKA in each subgroup in terms of postoperative ROM, with a higher degree of knee flexion for HF-TKA than S-TKA. However, no statistical difference was identified between HF-TKA and S-TKA in other clinical outcomes including various functional scores and complications.

CONCLUSIONS

On the basis of this meta-analysis, we can recommended HF-TKA as an alternative choice to S-TKA for patients requiring higher knee flexion in their daily activities.

20-Year Minimum Outcomes and Survival Rate of High-Flexion Versus Standard Total Knee Arthroplasty

BACKGROUND

There are conflicting reports of early and mid-term results of the high-flexion total knee arthroplasties (TKAs). The purpose of the present long-term follow-up study was to determine the long-term (minimum 20 years) clinical and radiographic and CT scan results, and the survival rates of high-flexion versus standard TKAs.

METHODS

Ninety-five patients (190 knees) were included (mean age, 65 ± 6.5 years). The mean follow-up was 20.3 years (range, 20 to 20.6 years).

RESULTS

Revision of the TKA was performed in 5 knees (5.2%) with high-flexion TKA and in 3 knees (3.2%) with standard TKA. The rate of survival at 20 years was 94.8% (95% CI, 91%-98%) in the high-flexion TKA group and 96.8% (95% CI, 92%-100%) in the standard TKA group with reoperation for any reason. No knee had osteolysis in either group.

CONCLUSIONS

At this length of follow-up, high-flexion TKA has comparable outcomes and survivorship to standard TKA.

Clinical, Functional, and Midterm Survival Analysis on Sigma Curved Plus Ultracongruent Polyethylene Insert in Primary Total Knee Arthroplasty: A Retrospective Study

BACKGROUND

Posterior-stabilized (PS) total knee arthroplasty (TKA) poses problems such as the need for intercondylar notch bone resection as well as cam and post wear and patella clunk. Owing to its heightened anterior profile, an ultracongruent polyethylene insert prevents the excessive posterior translation of tibia in the case of a deficient or scarified posterior cruciate ligament (PCL). This study aimed to determine whether an ultracongruent insert provides satisfactory clinical and functional outcomes and midterm survival benefits.

METHODS

Based on the reviewed medical records of 200 patients, 240 primary TKA cases involving the use of Sigma Curved Plus (DePuy International, Ltd., Leeds, UK) ultracongruent insert were retrospectively enrolled in this study. Follow-up data were used to evaluate the clinical and radiological outcomes and to conduct a Kaplan-Meier survival analysis.

RESULTS

The mean follow-up duration for 224 knees was 5.8 years (range 5-6.5 years). A revision was made due to infection in two patients and due to periprosthetic fractures in two other patients. The mean knee flexion improved from 101.97° ± 9.43° (range 85°-125°) to 125.75° ± 9.58° (range 100°-140°) at the final follow-up. The mean Knee Society score improved from 43.1 ± 9.76 to 88.3 ± 3.2, and the function score improved from 44.95 ± 7.26 to 90.16 ± 3.71. None of the patients showed radiographic loosening of either insert component, but 22 (5%) patients showed radiolucent lines (<2 mm). The Kaplan-Meier analysis showed that the five-year survival of the insert with an endpoint of revision for any reason was 98.1% (confidence interval, CI, 95.7-99.6%).

CONCLUSION

The Sigma Curved Plus insert showed a low failure rate with good clinical, functional, and midterm survival outcomes in comparison to standard outcomes reported in earlier studies. Further follow-up studies are warranted to determine whether the insert's performance is maintained in the long term.

Comparison of Posterior Cruciate-Retaining and High-Flexion Cruciate-Retaining Total Knee Arthroplasty Design

BACKGROUND

High-flexion prostheses have been developed to achieve deep flexion after total knee arthroplasty. The purpose of this study is to compare standard NexGen (CR, cruciate-retaining) and high-flexion NexGen (CR-flex) total knee prostheses in terms of range of motion, clinical and radiologic outcomes, rates of complications, and survivorship in long-term follow-up.

METHODS

From January 2000 to December 2008, 423 consecutive knees underwent total knee arthroplasty using standard CR or CR-flex prostheses. Fifty-three patients were lost to follow-up or declined to participate and 54 died, leaving 290 knees. The minimum duration of follow-up was 8 years (mean 10.1 years). Physical examination and knee scoring of patients were assessed preoperatively, at 6 months and 1 year after surgery, and annually thereafter. Supine anteroposterior and lateral radiographs and standing anteroposterior hip-to-ankle radiographs were obtained preoperatively and at each follow-up.

RESULTS

Mean postoperative range of motions in the standard CR group and the CR-flex group were similar, showing no significant difference between the 2 groups (P = .853). At the time of the final follow-up, mean total Hospital for Special Surgery scores were similar between the 2 groups (P = .118). Mean Knee Society pain (P = .325) and function scores (P = .659) were also comparable between the 2 groups. Western Ontario and McMaster Universities Osteoarthritis Index score showed no intergroup difference either (P = .586). The mean hip-knee-ankle angle at the final follow-up was approximately the same (P = .940). Mean coronal angles of femoral and tibial component at final follow-up were also similar (P = .211 and P = .764, respectively). The prevalence of the radiolucent line was 0.6% in the standard CR group and 0.9% in the CR-flex group. Estimated survival rate according to Kaplan-Meier survival analysis was 97.2% in the standard CR group and 95.6% in the CR-flex group at mean follow-up of 10.1 years.

CONCLUSION

This study suggests that excellent clinical and radiographic outcomes could be achieved with both standard and high-flexion CR total knee designs. High-flexion CR prosthesis did not show any advantages over the standard design.

Fixed-bearing versus high-flexion RP total knee arthroplasty (TKA): midterm results of a randomized controlled trial

Background

We compared the midterm results after total knee arthroplasty (TKA) using PFC Sigma RP-F mobile model with PFC Sigma PS fixed model.

Materials and methods

In this randomized controlled trial, we analyzed 50 knees that underwent TKA with PFC Sigma RP-F and 60 knees with PFC Sigma PS fixed model. The follow-up period ranged from 76 to 104 months.

Results

The knee score, function score, and radiographic evaluation were significantly not different between the two groups at final follow-up. No revisions, subluxations, dislocations, or infections were seen. Also, no radiographic evidence of component loosening, osteolysis, or malalignment was observed in any knee. The results for both groups show good patient satisfaction.

Conclusions

The midterm clinical and radiographic results of the two prostheses did not show significant differences between the two groups.

Level of evidence

Level of evidence is level II.

Comparison of High-Flexion Fixed-Bearing and High-Flexion Mobile-Bearing Total Knee Arthroplasties-A Prospective Randomized Study

BACKGROUND

There is none, to our knowledge, about comparison of high-flexion fixed-bearing and high-flexion mobile-bearing total knee arthroplasties (TKAs) in the same patients. The purpose of this study was to determine whether clinical results; radiographic and computed tomographic scan results; and the survival rate of a high-flexion mobile-bearing TKA is better than that of a high-flexion fixed-bearing TKA.

METHODS

The present study consisted of 92 patients (184 knees) who underwent same-day bilateral TKA. Of those, 17 were men and 75 were women. The mean age at the time of index arthroplasty was 61.5 ± 8.3 years (range 52-65 years). The mean body mass index was 26.2 ± 3.3 kg/m² (range 23-34 kg/m²). The mean follow-up was 11.2 years (range 10-12 years).

RESULTS

The Knee Society knee scores (93 vs 92 points; P = .531) and function scores (80 vs 80 points; P = 1.000), WOMAC scores (14 vs 15 points; P = .972), and UCLA activity scores (6 vs 6 points; P = 1.000) were not different between the 2 groups at 12 years follow-up. There were no differences in any radiographic and CT scan parameters between the 2 groups. Kaplan-Meier survivorship of the TKA component was 98% (95% confidence interval, 93-100) in the high-flexion fixed-bearing TKA group and 99% (95% confidence interval, 94-100) in the high-flexion mobile-bearing TKA group 12 years after the operation.

CONCLUSION

We found no benefit to mobile-bearing TKA in terms of pain, function, radiographic and CT scan results, and survivorship. Longer-term follow-up is necessary to prove the benefit of the high-flexion mobile-bearing TKA over the high-flexion fixed-bearing TKA.

Kneeling and standing up from a chair as performance-based tests to evaluate knee function in the high-flexion range: a randomized controlled trial comparing a conventional and a high-flexion TKA design

Background

We compared the functional outcome between conventional and high-flexion total knee arthroplasty (TKA) using kneeling and sit-to-stand tests at 1 year post-operative. In addition, the patient’s daily functioning, pain and satisfaction were quantified using questionnaires.

Methods

We randomly assigned 56 patients to receive either a conventional or a high-flexion TKA. Primary outcomes were maximum flexion angle and maximum thigh-calf contact measured during kneeling at 1 year post operatively. Secondary outcomes were the angular knee velocity and ground reaction force ratio measured during sit-to-stand performance tests, and questionnaires.

Results

At one year post-operative, maximum knee flexion during kneeling was higher for the high-flexion TKA group (median 128.02° (range 108–146)) compared to the conventional TKA group (119.13° (range 72–135)) (p = 0.03). Maximum thigh-calf contact force was higher for the high flexion TKA group (median 17.82 N (range 2.98–114.64)) compared to the conventional TKA group (median 9.37 N (range 0.33–46.58))(p = 0.04). The sit-to-stand tests showed a significantly higher angular knee velocity in the conventional TKA group (12.12 rad/s (95%CI 0.34–23.91); p = 0.04). There were no significant differences between groups in ground reaction force ratios and patient-reported outcome scores.

Conclusion

Although no differences were found in patient-reported outcome scores, differences in performance-based tests were clearly apparent. Standing up from a chair at 90° of knee flexion appeared to be easier for the conventional group. The kneeling test revealed significantly higher weight-bearing knee flexion for the high-flex group. Hence, if kneeling is an important activity for a patient a high-flex design may be recommendable.

Trial registration

The study was retrospectively registered in ClinicalTrials.gov under identifier NCT00899041 (date of registration: May 11, 2009).

Do High-Flexion Total Knee Designs Increase the Risk of Femoral Component Loosening?

BACKGROUND

The purpose of our prospective, randomized, long-term investigation is to compare the aseptic loosening rate of the femoral component of the total knee prosthesis and clinical and radiographic results of high-flexion posterior cruciate-substituting knee prosthesis or standard posterior cruciate-substituting knee prosthesis in the same patients.

METHODS

There were 960 patients (mean age 71.3 years). The mean follow-up period was 13.2 years (range 10-14). The patients were assessed clinically and radiographically with rating systems of the Knee Society. Furthermore, Western Ontario and McMaster Universities Osteoarthritis questionnaire and ranges of knee motion were determined in both groups.

RESULTS

In the high-flexion knee group, 2 knees (0.2%) had aseptic loosening of both femoral and tibial components. In the standard knee group, 2 knees (0.2%) had aseptic loosening of the femoral component only. The mean postoperative knee scores (97 vs 97 points), Western Ontario and McMaster Universities Osteoarthritis scores (19 vs 19 points), and range of knee motion (128° vs 129°) were not significantly different between the 2 groups. Two knees (0.2%) in the high-flexion knee group underwent a revision of both femoral and tibial components and 2 knees (0.2%) in the standard knee group had a revision of the femoral component only.

CONCLUSION

After a mean of 13.2 years of follow-up, this study did not show increased incidence of femoral component loosening in the high-flexion knee group. Furthermore, we found no significant differences between the 2 groups with regard to clinical or radiographic parameters or range of knee motion.

Do outcomes reported in randomised controlled trials of joint replacement surgery fulfil the OMERACT 2.0 Filter? A review of the 2008 and 2013 literature

BACKGROUND

It is not known, whether outcome reporting in trials of total joint arthroplasty in the recent years is adequate or not. Our objective was to assess whether outcomes reported in total joint replacement (TJR) trials fulfil the Outcome Measures in Rheumatology (OMERACT) Filter 2.0.

METHODS

We systematically reviewed all TJR trials in adults, published in English in 2008 or 2013. Searches were conducted in the Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE. Two authors independently applied the inclusion criteria for the studies, and any disagreement was resolved with a third review author. All outcome measures were abstracted using a pre-piloted standardised data extraction form and assessed for whether they mapped to one of the three OMERACT Filter 2.0 core areas: pathophysiological, life impact, and death.

RESULTS

From 1635 trials identified, we included 70 trials (30 in 2008 and 40 in 2013) meeting the eligibility criteria. Twenty-two (31%) trials reported the three essential OMERACT core areas. Among the 27 hip replacement surgery trials and 39 knee replacement surgery trials included, 11 hip (41%) and nine knee (23%) trials reported all three essential OMERACT core areas. The most common outcome domains/measures were pain (20/27, 74%) and function (23/27, 85%) in hip trials and pain (26/39, 67%) and function (27/39, 69%) in knee trials. Results were similar for shoulder and hand joint replacement trials.

CONCLUSIONS

We identified significant gaps in the measurement of OMERACT core outcome areas in TJR trials, despite the majority reporting outcome domains of pain and function. An international consensus of key stakeholders is needed to develop a core domain set for reporting of TJR trials.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42014009216.

Outcome Measures Used in Arthroplasty Trials: Systematic Review of the 2008 and 2013 Literature

OBJECTIVE

Previously published literature assessing the reporting of outcome measures used in joint replacement randomized controlled trials (RCT) has revealed disappointing results. It remains unknown whether international initiatives have led to any improvement in the quality of reporting and/or a reduction in the heterogeneity of outcome measures used. Our objective was to systematically assess and compare primary outcome measures and the risk of bias in joint replacement RCT published in 2008 and 2013.

METHODS

We searched MEDLINE, EMBASE, and CENTRAL for RCT investigating adult patients undergoing joint replacement surgery. Two authors independently identified eligible trials, extracted data, and assessed risk of bias using the Cochrane tool.

RESULTS

Seventy RCT (30 in 2008, 40 in 2013) met the eligibility criteria. There was no significant difference in the number of trials judged to be at low overall risk of bias (n = 6, 20%) in 2008 compared with 2013 [6 (15%); chi-square = 0.302, p = 0.75]. Significantly more trials published in 2008 did not specify a primary outcome measure (n = 25, 83%) compared with 18 trials (45%) in 2013 (chi-square = 10.6316, p = 0.001). When specified, there was significant heterogeneity in the measures used to assess primary outcomes.

CONCLUSION

While less than a quarter of trials published in both 2008 and 2013 were judged to be at low overall risk of bias, significantly more trials published in 2013 specified a primary outcome. Although this might represent a temporal trend toward improvement, the overall frequency of primary outcome reporting and the wide heterogeneity in primary outcomes reported remain suboptimal.

Ten- to 13-Year Results of Mobile Bearing Posterior-Stabilized Rotating-Platform Knee Implants, Reported by Nondesigner Surgeon

BACKGROUND

Posterior-stabilized rotating-platform (PSRP) knee was designed with the purpose of improving postoperative flexion and stability. Its long-term performance has limited reports, which could show whether this purpose has been realized without deleterious effect. We report its long-term results at 10-13 years, of a previously studied cohort, evaluated longitudinally.

METHODS

A total of 133 consecutive PSRP implants, selected for 118 patients were studied. Twenty-one patients (24 knees) were deceased and 11 patients (12 knees) were lost to follow-up after 10 years. Eighty patients (97 knees) completed clinical evaluation, of whom 78 patients (88 knees) also completed radiological evaluation.

RESULTS

Mean flexion improved from 106.8° (30°-150°) to 127° (90°-155°). Forty-three percent patients could sit crosslegged, 32.5% could sit on floor, and 3.4% could squat. Mean knee subscore of Knee Society Score improved from 28 (1-59) to 96 (67-100). Mean function subscore improved from 53 (5-81) to 78 (-10 to 100). After 10 years, 5 patients had zero function score because of developing other debilitating medical illnesses. Twenty-one dead patients (24 knees), at their last follow-up (7.7 years), had satisfactory scores. No patient had spinout or revision. Radiologically, alignment was satisfactory and there was no osteolysis. Kaplan-Meier analysis showed 100% implant survival.

CONCLUSION

PSRP design, evaluated after 10 years of implantation in selected patients, had 100% survival with good flexion. Addition of post and cam to the original rotating platform design has provided good stability without untoward effects of wear or osteolysis at 10-13 years.

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.

Total knee arthroplasty using NexGen LPS-flex® improves clinical outcomes without early loosening: minimum 6-year follow-up results

Background

The authors analyzed clinical and radiological 6-year follow-up results after total knee arthroplasty (TKA) with NexGen LPS-flex® and implant survivorship.

Methods

The medical records of 80 patients that underwent 122 TKAs using NexGen LPS-flex® from February 2005 to November 2008 and followed up for at least 6 years were reviewed. The Internal Knee Documentation Committee (IKDC) subjective form, Western Ontario and McMaster Universities Arthritis Index (WOMAC), and Knee Injury and Osteoarthritis Outcome Score (KOOS) scores and preoperative and postoperative ranges of motion (ROMs) were recorded. Radiological assessments were performed by simple radiography preoperatively, immediately postoperatively, and at the final follow-up.

Results

At the last follow-up visits, average ROM improved from 115.0° (80°–135°) to 131.76° (80°–150°), average IKDC subjective score from 30.54 (13–48) to 53.53 (31–80), average WOMAC score from 59.81 (35–90) to 15.98 (1–47), and average KOOS score from 75.33 (38–115) to 115.0 (52–174). The clinical results of 66 knees that had >130° of postoperative flexion and 56 knees that had <130 of postoperative flexion were compared. Radiolucent lines were found in 7 knees in those with a flexion angle of >130° and in 6 knees in those with a flexion angle of <130°, but the lines did not progress and meaningful loosening was not observed. Similarly, the occurrences of radiolucent lines in those with a flexion angle of >130° or <130° were not significantly different (p > 0.05).

Conclusions

TKA with NexGen LPS-flex® showed satisfactory clinical improvements, including high flexion, and no early loosening was found at 6-year follow-up visits.

Range of movement correlates with the Oxford knee score after total knee replacement: A prediction model and validation

BACKGROUND

Patient reported outcome measures are widely used in the evaluation of outcomes after Total Knee Replacement (TKR) in joint registries and large studies. The aim of this study was to assess the relationship between the Oxford knee score (OKS) and range of motion (ROM) after TKR, and to construct and validate prediction models of ROM from the measured OKS.

METHODS

Eight hundred sixty patients reviewed five years postoperatively and 273 patients reviewed nine to 10 years postoperatively completed an OKS. Of these, 808 (94%) and 226 (83%) patients, respectively, had a complete dataset (knee extension and ROM) and formed the study cohort.

RESULTS

Regression analysis demonstrated a significant correlation between the OKS and ROM (r=0.38, p<0.001) after adjusting for other confounding variables (age, sex, body mass index, and knee extension). A prediction model was constructed and validated using a second cohort of 226 patients at nine to 10 years after their TKR. Intraclass correlation demonstrated good reliability (r=0.60, 95% CI 0.47 to 0.69) between predicted and actual measured ROM for this group. However, when the OKS is used in isolation the reliability of the predicted ROM is diminished (intraclass correlation r=0.41, 95% CI 0.24 to 0.55).

CONCLUSIONS

The OKS is an independent predictor of ROM after TKR. It is also possible to predict ROM from the OKS, but the reliability of this is improved when other independent predictors such as age, gender, body mass index (BMI) and degree of knee extension are also acknowledged.

Is High-Flexion Total Knee Arthroplasty a Valid Concept? Bilateral Comparison With Standard Total Knee Arthroplasty

BACKGROUND

The purpose of this study was to determine whether the high-flexion total knee prosthesis significantly improves knee flexion in vivo.

METHODS

Forty-four patients undergoing same-day bilateral total knee arthroplasty for primary osteoarthritis of both knees were randomized to receive a standard posterior-stabilized knee prosthesis (P.F.C. Sigma; DePuy Johnson & Johnson, Warsaw, IN) in one knee and a high-flexion concept posterior-stabilized knee prosthesis (LOSPA; Corentec, Inc, Seoul, Korea) in the other knee and were followed up for 2 years postoperatively.

RESULTS

The mean postoperative range of motion was 128.8° (range, 100°-144°) in the LOSPA group and 128.5° (range, 100°-142°) in the P.F.C. Sigma group (P = .744). There were no significant differences in the postoperative mean Knee Society score and Western Ontario and McMaster Universities Osteoarthritis Index score between the LOSPA and P.F.C. Sigma groups (P = .839 and P = .972, respectively).

CONCLUSION

Despite theoretical range of motion advantages of high-flexion prosthesis, there were no group differences with regard to range of motion, clinical outcomes, and the incidence of radiolucent lines at final follow-up assessment.

First clinical study of a novel complete metal-free ceramic total knee replacement system

Background

The aim of the study was to evaluate the safety and efficacy of a novel metal-free ceramic total knee replacement system.

Methods

Thirty-eight primary total knee arthroplasties (TKAs) were performed on 34 patients using the metal-free BPK-S ceramic total knee replacement system with both the femoral and tibial components of an alumina/zirconia ceramic composite. The clinical outcome was evaluated pre- and postoperatively at 3 (n = 32 TKA) and 12 months (n = 32 TKA) using the Knee Society Score (KSS), the Oxford Knee Score and the EQ-5D. Safety analysis was performed by radiological examination and assessment of adverse events.

Results

Postoperatively, the KSS, Oxford Knee Score and EQ-5D improved significantly at 3 and 12 months (p < 0.001). Non-progressive partial radiolucent lines were observed in six cases, but there was no osteolysis and no implant loosening. Induction or exacerbation of allergies did not occur during the follow-up.

Conclusions

The metal-free BPK-S ceramic total knee replacement system proved to be a safe and clinically efficient alternative to metal implants in this short-term follow-up study.

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.

Midterm survivorship and clinical outcome of INDUS knee prosthesis: 5 year followup study

BACKGROUND

INDUS knee implant has been designed as per the anatomical morphology of the Indian population and has shown good clinical outcome in short term studies. The purpose of the present study was to report the midterm survivorship and clinical outcome of this implant.

MATERIALS AND METHODS

Two hundred and twenty three primary total knee arthroplasties in 209 consecutive patients using the INDUS knee prosthesis were prospectively enrolled. There were 145 females (155 knees) and 64 males (68 knees) with a mean age of 69.95 years (range 42-86 years). Annual followup with clinical and radiological examination was conducted, and a survivorship analysis was done using the Kaplan-Meier analysis.

RESULTS

Mean followup was 5.8 years (range 5-6.5 years). Eleven patients died while eight were lost to followup and a total of 204 knees were available for followup. The mean knee flexion improved from preoperative 110.4° ± 11.24° (range 60°-130°) to 128.17° ± 8.32° (range 100°-140°) at the final followup. The mean knee score improved from 40.1 ± 10.7 to 90.3 ± 5.34 while the function score improved from 44.35 ± 12.9 to 89.58 ± 7.43. Two patient developed infection and required revision. The Kaplan-Meier analysis reported a survivorship of 98.6% (confidence interval 95.7-99.6%) at the end for 5 years for INDUS knee prosthesis.

CONCLUSION

INDUS knee prosthesis has excellent survivorship with a good clinical outcome and low failure rate.

Cruciate Retaining Implant With Biomimetic Articular Surface to Reproduce Activity Dependent Kinematics of the Normal Knee

Alterations in normal knee kinematics following total knee arthroplasty (TKA) arise in part from the non-anatomic articular geometry of contemporary implants. In this study, the kinematics of a novel posterior cruciate-retaining (CR) implant with anatomic (biomimetic) articular surface, were compared to that of contemporary CR implants during various simulated activities. Across different simulated activities the biomimetic-CR mimicked normal kinematic patterns more closely than contemporary CR implants. In particular, during deep knee bend and chair-sit, the biomimetic-CR showed medial pivot motion, while other CR implants showed abnormal motion including lateral pivot or no pivot, and paradoxical anterior sliding. Further in vivo and clinical studies are needed to determine whether such biomimetic implants can truly help to achieve a more normal feeling knee and improved patient satisfaction.

High-Flexion Total Knee Arthroplasty Using NexGen LPS-Flex System: Minimum 5-year Follow-up Results

PURPOSE

This study is to report clinical and radiological results of high-flexion total knee arthroplasty (TKA) using NexGen LPS-flex system at a minimum 5-year follow-up, and to analyze the implant survivorship based on the results.

MATERIALS AND METHODS

A total of 80 patients (118 knees) who underwent patellar preserving TKA using NexGen LPS-flex implant between February 2007 and February 2008 and could be followed for minimum 5 years were reviewed. The range of motion (ROM), hip-knee-ankle angle, Knee Society Knee score (KSKS), and Knee Society Function score (KSFS) were assessed preoperatively and at the last follow-up and analyzed. Implant position of the femoral and tibial components on the immediate postoperative and last follow-up X-rays were compared.

RESULTS

The mean ROM was 110.2°±14.5° (range, 60° to 140°) preoperatively and 132.4°±5.2° (range, 90° to 145°) at the last follow-up. KSKS was 36.9°±6.4° preoperatively and 94.2°±3.2° at the last follow-up. KSFS was 30.5°±5.7° preoperatively and 93.7°±4.1° at the last follow-up. There was no statistically significant change in the implant position measured as α, β, γ, and δ angles at the last follow-up compared to the immediate postoperative values. Radiolucent lines were observed in 13 knees (11%) on the last follow-up X-rays. Revision TKA was performed due to aseptic implant loosening in 1 knee (0.84%), and the survival rate at the 5th postoperative year was 99.2%.

CONCLUSIONS

The clinical and radiological outcomes of high-flexion TKA using NexGen LPS-Flex implant design were satisfactory with 99.2% implant survival rate after 5 years of protected activities of daily living.

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.

Clinical outcomes after high-flex versus conventional total knee arthroplasty

PURPOSE

To compare clinical outcomes after high-flex versus conventional total knee arthroplasty (TKA).

METHODS

A systematic review and meta-regression were performed to compare post-operative outcomes between the two types of prostheses. Relevant randomized controlled trials were identified from MEDLINE and Scopus up to November, 2014.

RESULTS

Fourteen of 369 studies were eligible; 14, 7, 6, 5, 3, 12 and 7 studies were included in the pooling of maximum knee flexion, Knee Society Knee Score (KS), Knee Society Function Score (FS), Hospital for Special Surgery score (HSS), short-form (SF) physical activity score, post-operative complications (DVT, fractures, infection) and revision TKA, respectively. The high-flex TKA had 1.97° [95% confidence interval (CI) 0.37, 3.57], -0.86 (95% CI -1.65, 0.07) and -1.34 (-2.57, -0.11) higher mean maximum knee flexion, KS and FS when compared to conventional TKA. However, there were non-significant differences in HSS, SF-36 (physical), complications and revision TKA.

CONCLUSION

This study suggests that there are improvements in post-operative knee range of motion and knee scores in high-flex TKA implants when compared to conventional TKA implants; however, the difference was very small and therefore might not have any clinical impact. Therefore, conventional TKA can be used as a substitute. However, cost-effective analysis should be performed to make appropriate selections in the future. There are no statistically significant differences in terms of HSS, quality of life, complications and revisions between the groups.

LEVEL OF EVIDENCE

I.

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.

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.

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.

Patellofemoral kinematics during deep knee flexion after total knee replacement: a computational simulation

PURPOSE

Actions requiring deep knee flexion, such as kneeling and squatting, are challenging to perform after total knee replacement (TKR), though many manufactures emphasize that their knee prostheses could safely achieve high flexion. Little is known about the patellofemoral kinematics during deep flexion. This study aimed to track the movement of the patella during kneeling and squatting through dynamic computational simulation.

METHODS

A validated knee model was used to analyse the patellar kinematics after TKR, including shifting, tilting and rotation. The data were captured from full extension to 135° of knee flexion. For kneeling, an anterior force of 500 N was applied perpendicularly on the tibial tubercle as the knee flexed from 90° to 135°. For squatting, a ground reaction force was applied through the tibia from full extension to 135° of flexion.

RESULTS

This study found that patellar shifting and rotation in kneeling were similar to those while squatting. However, during kneeling, the patella had a greater medial tilt and showed signs of abrupt patellar tilt owning to an external force being concentrated on the tibial tubercle.

CONCLUSIONS

In terms of squatting and kneeling movements, the latter is a more strenuous action for the patellofemoral joint after TKR due to the high forces acting on the tibial tubercle. It is suggested that overweight patients or those requiring high flexion should try to avoid kneeling to reduce the risk of the polyethylene wear. Further modification of trochlear geometry may be required to accommodate abrupt changes in patellar tilting.

LEVEL OF EVIDENCE

II.

Results of total knee arthroplasty with NexGen LPS-Flex for osteoarthritis in the valgus knee: a study of 26 patients followed for a minimum of 2 years

The present study aimed to examine the results of total knee arthroplasty (TKA) with the NexGen Legacy posterior-stabilized (LPS)-Flex system for osteoarthritis in the valgus knee. Between 2003 and 2011, 27 valgus knees in 26 patients who underwent TKA with the NexGen LPS-Flex implant were clinically and radiologically evaluated after a minimum follow-up of 2 years. The original diagnosis was osteoarthritis. Knee Society Knee Score (KSKS), Knee Society Function Score (KSFS), maximum flexion angle, maximum extension angle, and radiological femorotibial angle (FTA) were evaluated pre- and postoperatively. The mean KSKS improved from 42.6 before surgery to 82.2 by the final follow-up (p < 0.01), and the mean KSFS improved from 41.1 to 80.9 (p < 0.01). The mean maximum flexion angle changed from 109.1° to 117.3° (no statistical significance) and the maximum extension angle improved from -9.7° to -3.6° (p < 0.05) postoperatively. The postoperative radiological FTA was 172.4°, which was closer to a neutral angle (174°) than the preoperative FTA (166.4°) (p < 0.01). None of the patients had undergone revision surgery by the final follow-up. As a conclusion, TKA with the NexGen LPS-Flex implant for osteoarthritis in the valgus knee resulted in satisfactory improvement regarding objective outcomes, although a longer term follow-up with a greater number of cases is necessary to verify these results.

Biomechanical considerations in the design of high-flexion total knee replacements

Typically, joint arthroplasty is performed to relieve pain and improve functionality in a diseased or damaged joint. Total knee arthroplasty (TKA) involves replacing the entire knee joint, both femoral and tibial surfaces, with anatomically shaped artificial components in the hope of regaining normal joint function and permitting a full range of knee flexion. In spite of the design of the prosthesis itself, the degree of flexion attainable following TKA depends on a variety of factors, such as the joint's preoperative condition/flexion, muscle strength, and surgical technique. High-flexion knee prostheses have been developed to accommodate movements that require greater flexion than typically achievable with conventional TKA; such high flexion is especially prevalent in Asian cultures. Recently, computational techniques have been widely used for evaluating the functionality of knee prostheses and for improving biomechanical performance. To offer a better understanding of the development and evaluation techniques currently available, this paper aims to review some of the latest trends in the simulation of high-flexion knee prostheses.

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.

Quantified self and human movement: a review on the clinical impact of wearable sensing and feedback for gait analysis and intervention

The proliferation of miniaturized electronics has fueled a shift toward wearable sensors and feedback devices for the mass population. Quantified self and other similar movements involving wearable systems have gained recent interest. However, it is unclear what the clinical impact of these enabling technologies is on human gait. The purpose of this review is to assess clinical applications of wearable sensing and feedback for human gait and to identify areas of future research. Four electronic databases were searched to find articles employing wearable sensing or feedback for movements of the foot, ankle, shank, thigh, hip, pelvis, and trunk during gait. We retrieved 76 articles that met the inclusion criteria and identified four common clinical applications: (1) identifying movement disorders, (2) assessing surgical outcomes, (3) improving walking stability, and (4) reducing joint loading. Characteristics of knee and trunk motion were the most frequent gait parameters for both wearable sensing and wearable feedback. Most articles performed testing on healthy subjects, and the most prevalent patient populations were osteoarthritis, vestibular loss, Parkinson's disease, and post-stroke hemiplegia. The most widely used wearable sensors were inertial measurement units (accelerometer and gyroscope packaged together) and goniometers. Haptic (touch) and auditory were the most common feedback sensations. This review highlights the current state of the literature and demonstrates substantial potential clinical benefits of wearable sensing and feedback. Future research should focus on wearable sensing and feedback in patient populations, in natural human environments outside the laboratory such as at home or work, and on continuous, long-term monitoring and intervention.

Increased risk of revision for high flexion total knee replacement with thicker tibial liners

The outcome of total knee replacement (TKR) using components designed to increase the range of flexion is not fully understood. The short- to mid-term risk of aseptic revision in high flexion TKR was evaluated. The endpoint of the study was aseptic revision and the following variables were investigated: implant design (high flexion vs non-high flexion), the thickness of the tibial insert (≤ 14 mm vs > 14 mm), cruciate ligament (posterior stabilised (PS) vs cruciate retaining), mobility (fixed vs rotating), and the manufacturer (Zimmer, Smith & Nephew and DePuy). Covariates included patient, implant, surgeon and hospital factors. Marginal Cox proportional hazard models were used. In a cohort of 64 000 TKRs, high flexion components were used in 8035 (12.5%). The high flexion knees with tibial liners of thickness > 14 mm had a density of revision of 1.45/100 years of observation, compared with 0.37/100 in non-high flexion TKR with liners ≤ 14 mm thick. Relative to a standard fixed PS TKR, the NexGen (Zimmer, Warsaw, Indiana) Gender Specific Female high flexion fixed PS TKR had an increased risk of revision (hazard ratio (HR) 2.27 (95% confidence interval (CI) 1.48 to 3.50)), an effect that was magnified when a thicker tibial insert was used (HR 8.10 (95% CI 4.41 to 14.89)). Surgeons should be cautious when choosing high flexion TKRs, particularly when thicker tibial liners might be required.

Outcome and range of motion using a high-flexion cruciate-retaining TKA

Increased knee flexion after total knee arthroplasty (TKA) may contribute to patients' increased satisfaction and more active lifestyles. This study evaluated a TKA component designed for high flexion (more than 125°). The design features an anatomic sagittal femoral radius with short, flared femoral condyles to allow for femoral rollback. Fifty TKA procedures in 47 patients were evaluated prospectively regarding clinical outcomes using Knee Society knee and function scores, Short Form 12 physical component scores, and flexion measured clinically and by digital lateral supine active flexion radiographs. Preoperative and 1-year postoperative radiographs were analyzed by an independent observer. Mean maximum flexion measured clinically was 115° preoperatively and 120° one year postoperatively, with 76% of TKAs achieving more than 120° and 44% achieving more than 125°. Sex, body mass index, and preoperative flexion were not predictors of postoperative flexion. Mean flexion by radiograph was 108° preoperatively and 111° one year postoperatively, with 31% of knees achieving more than 120° and 14% more than 125°. Mean Knee Society knee and function scores and the Short Form 12 physical component scores were 52, 55, and 32 preoperatively, respectively, and 89, 77, and 40 one year postoperatively, respectively. Of the 50 knees, 84% had improvement in their Knee Society function scores, and 76% had improvement in their Short Form 12 physical component scores. The study revealed evidence of increased early postoperative flexion with the use of a cruciate-retaining high-flexion TKA design.

Risk factors for total knee arthroplasty aseptic revision

Using a Total Joint Replacement Registry, patient, operative, implant, surgeon, and hospital risk factors associated with aseptic revision after primary total knee arthroplasty (TKA) were evaluated. From 04/2001 to 12/31/2010 64,017 primary TKA cases, followed for a median time of 2.9 years, were registered and included in the analysis. Patients were predominantly female, white, with osteoarthritis, and obese. The crude aseptic revision rate is 1.3% (N=826). The cumulative survival for aseptic revision at 8 years is 97.6% (95% CI 97.3%-97.8%). Adjusted models revealed that age, race, body mass index, diabetic status, bilateral procedures, high-flex implants, and the LCS mobile bearing knee are associated with risk of revision. Gender, general health status, diagnosis, surgeon fellowship training, surgeon volume, hospital volume, fixation, and bearing surface material were not associated with risk of aseptic revision. Recognition of surgical factors associated with TKA failures can help the surgeons with their choices of surgical techniques and implants.

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

High-flexion knee prosthesis was introduced with the aim of obtaining higher degree of flexion and good survivorship in patients with high functional demands or those requiring squatting, kneeling, etc., which is more common in Asians. Based on all the research and experience with this prosthesis, it was concluded that high flexion designs meet the need of deeper degrees of flexion in selected sets of patients only. Results were equal and comparable to the traditional standard posterior-stabilized total knee arthroplasty design and superior to it in terms of gaining more flexion and fulfilling activities, such as squatting, kneeling, and sitting cross-legged.

High-flexion prosthesis improves function of TKA in Asian patients without decreasing early survivorship

BACKGROUND

Two previous studies recently raised the possibility of a high risk of early femoral components loosening with high-flexion (HF) prostheses in Asian populations and suggested that the high failure rate of HF TKAs was associated with HF ability. However, these findings are controversial given other studies reporting a low incidence of aseptic failures in HF prostheses.

QUESTIONS/PURPOSES

We therefore determined (1) the rate of achieving postoperative HF after HF TKA; (2) whether the aseptic loosening rate of HF prostheses is high; and (3) whether the survivorship was worsened in patients who achieved postoperative deep knee flexion in our cohort of Korean patients.

METHODS

We retrospectively reviewed 488 patients who had 698 primary TKAs using the NexGen(®) Legacy Posterior-Stabilized Flex system implanted from 2003 to 2010. There were 40 men and 448 women with a mean age of 68 years. We obtained Hospital for Special Surgery scores, maximal flexion, and radiographs. The minimum followup for functional and radiographic evaluations was 2 years (median, 4.8 years; range, 2-8.7 years). We performed a survival analysis on all patients for aseptic loosening.

RESULTS

Three hundred sixty knees (52%) could achieve ≥ 135° maximum flexion. Six of the 698 knees (0.9%) developed aseptic loosening (three femoral and three tibial). The survival at 5 years for aseptic loosening was 99.1%. The overall survival for aseptic failure did not differ between knees that achieved HF and those that did not.

CONCLUSIONS

We observed a low incidence of early aseptic loosening of HF designs in this series. Our findings suggest HF TKAs have high survival in Asian patients at 5 years although half of the patients attained maximum flexion more than 135° postoperatively.

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.

Effect of implant design on knee flexion

From March 2006 to August 2008, 93 subjects (186 knees) underwent simultaneous bilateral total knee arthroplasty performed by eight surgeons at North American centers. This randomized study was conducted to determine whether non-weight-bearing passive flexion was superior for knees receiving a posterior stabilized high flexion device compared to a posterior stabilized standard device in the contra-lateral knee. Weight-bearing single leg active flexion was one secondary endpoint. Follow-up compliance was 92.5%. Results show small, but significant superiority in the motion metrics for the high flexion device compared to the standard device 12 months after surgery, especially for a subgroup of patients with pre-operative flexion less than 120° in both knees. Thus, the ideal candidate for the high flexion device may be one with lesser pre-operative flexion.

The effect of electromagnetic navigation in total knee arthroplasty on knee kinematics during functional activities using flexible electrogoniometry

BACKGROUND

Navigated total knee arthroplasty has been shown to increase accuracy in post operative implant alignment. By contrast navigated total knee arthroplasty has not shown significant functional improvements to date, when compared with conventional surgery using subjective clinical questionnaire scores. The aim of this study was to compare the knee joint kinematics measured during functional activities using electrogoniometry 12 months after total knee arthroplasty in randomised navigated and conventional total knee arthroplasty groups.

METHODS

The study design was a double blinded, randomised, prospective, controlled trial. The patients were randomised into 2 surgical groups (n=102 navigated group, n=98 conventional group; mean age navigated=67, conventional=67). Flexible electrogoniometry was used to measure patient's knee kinematics with respect to time during 12 functional activities.

FINDINGS

No significant difference was found in terms of the maximum, minimum and excursion knee joint angle during any of the functional activities. However there was a statistically significant improvement in the level and slope gait cycle at the pre swing phase in the navigated group.

INTERPRETATION

There were minimal functional improvements in the navigated total knee arthroplasty group 12 months after surgery. However, these are unlikely to have a significant effect on daily activity for the navigated group.

Outcomes of the different types of total knee arthroplasty with the identical femoral geometry

Purpose

There are controversies around the role of the posterior cruciate ligament and the effect of design modifications for high flexion in total knee arthroplasty (TKA). So, we compared the clinical outcomes of the cruciate retaining (CR), posterior stabilized (PS), and high flexion posterior stabilized (F-PS) designs in TKA with identical femoral geometry.

Materials and Methods

One hundred seventy nine knees with 3 different types of prostheses after a minimum 5-year follow-up were enrolled in this retrospective study: 45 with CR, 40 with PS and 94 with F-PS. The mean ages of these groups were 65.7, 67.2, and 67.5, and the mean durations of follow-up were 8.1, 8.0, and 6.8 years, respectively. We compared the range of motion, functional outcomes, and radiographic measurements at the 2-year follow-up and last follow-up.

Results

The maximal flexion angle was significantly lower in the CR group than the F-PS group at the 2-year follow-up. However, there was no significant difference at the last follow-up. Functional outcomes and survival rate of the three groups were similar at the last follow-up.

Conclusions

Three different types of TKAs (CR, PS and F-PS) with identical femoral geometry showed similar mid-term outcomes with regard to the range of motion, functional outcomes and survival rate.

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.

Gender-specific high-flexion knee prosthesis in Indian women: a prospective randomised study

PURPOSE

To compare outcomes in Indian women who underwent total knee arthroplasty (TKA) using the standard Legacy Posterior Stabilised (LPS) versus the gender-specific LPS high-flexion knee prosthesis.

METHODS

100 women (200 knees) aged 60 to 80 years with an arc of flexion of ≥90º underwent simultaneous sequential TKA for primary osteoarthritis of both knees. They were randomised to receive the standard NexGen LPS prosthesis (n=50) or the gender-specific NexGen LPS High-Flex prosthesis (n=50). Both knees in each patient received the same prosthesis. The resected bone from the posterior femoral condyle was 2 mm greater when the gender-specific prosthesis was used. Patients were followed up at 3, 6, 12, and 24 months. Range of motion, Knee Society score, and Hospital for Special Surgery score were evaluated pre- and post-operatively by a single assessor.

RESULTS

The mean follow-up duration was 2.1 (range, 1.6-2.5) years. Respectively for the standard and gender-specific groups, the mean range of motion was 111º and 112º preoperatively and 120º and 123º at the latest follow-up. The gender-specific group gained approximately 3º more in range of motion (p=0.007). The Knee Society score and the Hospital for Special Surgery score between groups were not significantly different pre- and post-operatively.

CONCLUSION

The perceived advantage of a gender-specific prosthesis over a standard prosthesis did not translate into better clinical and functional outcome scores.