Muscle activity around the knee and gait performance in unicompartmental knee arthroplasty patients: a comparative study on fixed- and mobile-bearing designs

In Vivo Kinematic Analysis of Mobile-Bearing Unicompartmental Knee Arthroplasty during High Flexion Activities

Mobile-bearing (MB) unicompartmental knee arthroplasty (UKA) has high conformity between the femoral articular surface and the meniscal bearing; therefore, the surface and subsurface contact stress is reduced. Additionally, the survival rate is high. However, the in vivo kinematics of MB UKA knees during high-flexion activities of daily living remain unknown. The aim of this study was to investigate in vivo the three-dimensional kinematics of MB UKA knees during high-flexion activities of daily living. A total of 17 knees of 17 patients who could achieve kneeling after MB UKA were examined. Under fluoroscopy, each patient performed squatting and kneeling motions. To estimate the spatial position and orientation of the knee, a two-dimensional/three-dimensional registration technique was used. We evaluated the femoral rotation and varus-valgus angle relative to the tibia and the anteroposterior translation of the medial sulcus (medial side) and lateral epicondyle (lateral side) of the femur on the plane perpendicular to the tibial mechanical axis in each flexion angle. From 130° to 140° of flexion, the femoral external rotation during squatting was significantly smaller than that during kneeling. Additionally, the medial side of the femur during squatting was significantly more posteriorly located compared with that during kneeling. There was no significant difference between squatting and kneeling in terms of the lateral side of the femur and the varus-valgus position in each flexion angle. At high flexion angle, the kinematics of MB UKA knees may differ depending on the performance.

Preservation of prearthritic coronal knee phenotype and prearthritic coronal alignment yielded improved Kujala scores following ligament-guided medial unicompartmental knee arthroplasty

PURPOSE

There is a lack of literature evaluating outcomes of the ligament-guided approach in medial unicompartmental knee arthroplasty (UKA). An improved comprehension of the distribution of coronal plane alignment of the knee (CPAK) phenotypes and sagittal tibial wear patterns and their associations with patient-reported outcome measures (PROMs) and implant survivorship could provide insights into its further application in daily practice.

METHODS

A registry was reviewed for patients with a minimal 2-year follow-up who underwent robotic-assisted, ligament-guided, medial UKA between 2008 and 2016. Survivorship and postoperative PROMs were collected. CPAK phenotypes and sagittal tibial wear patterns were determined. Survivorship, Knee Injury and Osteoarthritis Outcome Score (KOOS), Kujala and patient satisfaction were compared between phenotypes and sagittal tibial wear patterns.

RESULTS

A total of 618 knees were included at a mean follow-up of 4.1 [2.0-9.6] years. Four-year conversion to the TKA survival rate was 98.9% [98.4%-99.3%] and 94.3% [93.3%-95.3%] for all-cause revision. Patients with preservation of the CPAK phenotype (84.5 ± 14.9, 81.8 ± 15.5, p = 0.033) and restoration of prearthritic coronal alignment (84.1 ± 14.9, 81.7 ± 15.9, p = 0.045) had a significantly higher Kujala score. No other significant differences in survivorship or PROMs were observed between phenotypes or sagittal tibial wear patterns. Additionally, no difference in survival rates was observed between preserved or altered phenotypes.

CONCLUSION

This study demonstrated that preservation of CPAK phenotype and preservation of prearthritic coronal alignment yielded a significantly higher Kujala score. No other significant differences in PROMs or implant survivorship were observed, suggesting that robotic-assisted, ligament-guided medial UKA provides equal outcomes for all observed phenotypes and sagittal tibial wear patterns in medial compartment OA as long as preoperative CPAK phenotype is preserved postoperatively.

LEVEL OF EVIDENCE

Level III.

Comparison of spatiotemporal, kinematic, and kinetic gait characteristics in total and unicompartmental knee arthroplasty during level walking: A systematic review and meta-analysis

PURPOSE

This meta-analysis was performed to compare the spatiotemporal, kinematic, and kinetic gait characteristics during level walking between total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA).

METHODS

An electronic database literature search was performed to screen clinical trials which were included the studies evaluating not only spatiotemporal, kinematic, and kinetic gait parameters, but also knee range of motion and knee score (Knee Society Score and Oxford Knee Score, i.e., KSS and OKS). The data analysis was performed using statistical software Stata 14.0 and Review Manager 5.4.

RESULTS

Thirteen studies (369 knees) that met the criteria were eventually included in this meta-analysis. The results revealed significant differences between UKA and TKA with regard to walking speed (P = 0.04), stride length (P = 0.02), maximum knee flexion at loading (P = 0.001), the 1st peak of vert-GRF (P = 0.006), the 1st valley of vert-GRF (P = 0.007), knee internal rotational moment (P = 0.04), knee extension (P < 0.00001), and KSS Function score (P = 0.05). In contrast, there were no statistical differences in the remaining spatiotemporal, kinematic, and kinetic gait parameters.

CONCLUSION

Medial UKA design is superior to TKA design with regard to walking speed, stride length, maximum knee flexion at loading, the 1st peak and the 1st valley of vert-GRF, knee internal rotational moment, knee extension, and KSS Function score. And it could provide a stronger basis for physicians to make clinical decisions.

Comparison of Functional Recovery Between Unicompartmental and Total Knee Arthroplasty: A Randomized Controlled Trial

BACKGROUND

Comparisons of functional recovery between unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) using performance-based tests are lacking. Therefore, this study aimed to compare 2-minute walk test (2MWT) and Timed Up-and-Go test (TUG) results between UKA and TKA for isolated medial knee osteoarthritis (OA). We hypothesized that UKA yields faster functional recovery than TKA as measured with the 2MWT and TUG.

METHODS

We conducted a randomized controlled trial comparing medial UKA and TKA in patients with isolated medial knee OA. A total of 110 patients were enrolled; after 11 exclusions, 99 patients (50 UKA, 49 TKA) were included in the final analysis. The patients were tested using the 2MWT and TUG preoperatively and at 6 weeks, 3 and 6 months, and 1 and 2 years postoperatively. Patient-reported outcome measures (PROMs) were also evaluated. The mean 2MWT, TUG, and PROM results were compared between groups at each time point.

RESULTS

The mean 2MWT distance after UKA was significantly longer than that after TKA at 6 weeks (96.5 ± 22.6 m for UKA compared with 81.1 ± 19.1 m for TKA; difference, 18 m [95% confidence interval (CI),10.4 to 25.6 m]; p < 0.001), 3 months (102.1± 24.4 compared with 87.5 ± 22.3 m; difference, 14.7 m [95% CI, 5.4 to 24.0 m]; p = 0.002), and 6 months (102.8 ± 16.2 compared with 89.6 ± 15.3 m; difference, 13.2 m [95% CI, 6.9 to 19.5 m]; p < 0.001). The values at 1 and 2 years were similar after UKA and TKA. The mean TUG after UKA was also significantly shorter than that after TKA at 6 weeks and 3 months. The mean PROMs were similar after both treatments, with the exception of the Oxford Knee Score and subscales of the Knee injury and Osteoarthritis Outcome Score at 6 weeks and 3 months postoperatively.

CONCLUSIONS

The 2MWT indicated that UKA for isolated medial knee OA enabled faster recovery than TKA did at 6 weeks to 6 months, and earlier recovery was also seen with the TUG at 6 weeks to 3 months. The 2MWT and TUG results after UKA and TKA were similar to one another at 1 and 2 years.

LEVEL OF EVIDENCE

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

A Morphometric Fixed-Bearing Unicompartmental Knee Arthroplasty Can Reproduce Normal Knee Kinematics. An In Vitro Robotic Evaluation

Background

Methods

Results

Conclusion

Evaluation of Knee Kinematics and Moments during Active Deep Flexion Activity after Oxford Mobile-Bearing Medial UKA-A Two-Year Follow-Up Study

Few studies have assessed knee range of motion (ROM) and moments of patients with mobile-bearing unicompartmental knee arthroplasty (MB UKA) during active deep flexion activities. We analyze knee kinematic and kinetic parameters during postoperative squatting-standing activity, aiming to evaluate the efficacy of MB UKA and postoperative rehabilitation progress. This was a clinical cohort study. We followed up with 37 patients diagnosed with medial knee osteoarthritis (OA) with primary UKA. After screening 31 patients were recruited to take gait tests. Squatting-standing activities were performed under the test of 10-camera motion analysis system and force plates preoperatively at different stages after UKA (12, 18, and 24 months). The average duration of follow-up was 24.4 months (from 22.8 to 26.7 months). Hip-knee-ankle angle improved significantly compared with pre-UKA as well as scores of American Knee Society Score, numeric rating scale, ORS, and Western Ontario and McMasters. University Osteoarthritis Index. About 83.6% (31/37) of follow-up patients completed squatting-standing activity independently. At 1-year follow-up, peak varus angle (20.6 ± 2.8 degrees), internal rotation angle (13.6 ± 1.8 degrees), extensor moment (1.44 ± 0.04N*m/kg), and internal rotator moment (0.02 ± 0.005N*m/kg) of UKA knees were inferior to contralateral knees. Peak adductor moment (0.76 ± 0.05N*m/kg) was superior to contralateral knees. At 2-year follow-up, peak flexion angle (125.0 ± 2.8 degrees) showed a growing trend meanwhile extensor (1.70 ± 0.03N*m/kg) and adductor (0.68 ± 0.06 N*m/kg) moment closely resembled those of the contralateral knee. MB UKA could alleviate the affected knee mainly in flexion-extension ROM and moment meanwhile did not affect the biomechanical indicators of healthy limbs. OA knees in the early postoperative period showed decreased extensor moment and increased adductor moment during active deep flexion activity. Better ROM and relatively more natural extensor and adductor moment of UKA knee with rehabilitation time increasing may predict ideal rehabilitation outcome in the medium or longer term.

Mobile Bearing versus Fixed Bearing for Unicompartmental Arthroplasty in Monocompartmental Osteoarthritis of the Knee: A Meta-Analysis

Introduction: Whether mobile-bearing (MB) unicompartmental knee arthroplasty (UKA) performs better than fixed-bearing (FB) implants in patients with monocompartmental osteoarthritis (OA) still remains unclear. Therefore, a meta-analysis comparing MB versus FB for UKA was conducted to investigate the possible advantages of MB versus FB in patient-reported outcome measures (PROMs), range of motion (ROM), and complications. We hypothesised that the MB design performs better than FB. Methods: This systematic review was conducted according to the 2020 PRISMA guidelines. In December 2021, PubMed, Web of Science, Google Scholar, and Embase were accessed, with no time constraints. All the clinical investigations comparing MB versus FB bearing for UKA were accessed. Only studies published in peer-reviewed journals were considered. Studies reporting data on revision settings were excluded, as were those combining unicompartmental and total knee arthroplasty. Results: Data from 25 studies (4696 patients) were collected; 58% (2724 of 4696 patients) were women. The mean length of follow-up was 45.8 ± 43.2. The mean age of the patients was 65.0 ± 5.6 years. No difference was found in range of motion (p = 0.05), Knee Scoring System (p = 0.9), function subscale (p = 0.2), and Oxford Knee Score (p = 0.4). No difference was found in the rate of revision (p = 0.2), aseptic loosening (p = 0.9), deep infections (p = 0.99), fractures (p = 0.6), and further extension of OA to the contralateral joint compartment (p = 0.2). Conclusion: The present meta-analysis failed to identify the possible superiority of the MB implants over the FB for UKA in patients with monocompartmental knee osteoarthritis. Long observational investigations are required to evaluate possible long-term complications and implant survivorship. These results should be interpreted within the limitations of the present study.

Patient-specific musculoskeletal models as a framework for comparing ACL function in unicompartmental versus bicruciate retaining arthroplasty

Unicompartmental knee arthroplasty has been shown to provide superior functional outcomes compared to total knee arthroplasty and have motivated development of advanced implant designs including bicruciate retaining knee arthroplasty. However, few validated frameworks are available to directly compare the effect of implant design and surgical techniques on ligament function and joint kinematics. In the present study, the subject-specific lower extremity models were developed based on musculoskeletal modeling framework using force-dependent kinematics method, and validated against in vivo telemetric data. The experiment data of two subjects who underwent TKA were obtained from the SimTK "Grand Challenge Competition" repository, and integrated into the subject-specific lower extremity model. Five walking gait trials and three different knee implant models for each subject were used as partial inputs for the model to predict knee biomechanics for unicompartmental, bicruciate retaining, and total knee arthroplasty. The results showed no significant differences in the tibiofemoral contact forces or angular kinematic parameters between three groups. However, unicompartmental knee arthroplasty demonstrated significantly more posterior tibial location between 0% and 40% of the gait cycle (p < 0.017). Significant differences in range of tibiofemoral anterior/posterior translation and medial/lateral translation were also observed between unicompartmental and bicruciate retaining arthroplasty (p < 0.017). Peak values of anterior cruciate ligament forces differed between unicompartmental and bicruciate retaining arthroplasty from 10% to 30% of the gait cycle. Findings of this study indicate that unicompartmental and bicruciate retaining arthroplasty do not have identical biomechanics and point to the complementary role of anterior cruciate ligament and articular geometry in guiding knee function. Further, the patient-specific musculoskeletal model developed provides a reliable framework for assessing new implant designs, and effect of surgical techniques on knee biomechanics following arthroplasty.

[Analysis of gait and effectiveness after unicompartmental knee arthroplasty]

Objective

To explore the gait trajectory characteristics and effectiveness after unicompartmental knee arthroplasty (UKA).

Methods

Thirty patients (30 knees) with anterior medial compartment osteoarthritis who were treated with UKA between January 2017 and December 2018 were selected as subjects (UKA group). According to age, gender, and side, 30 patients (30 knees) with knee osteoarthritis treated with total knee arthroplasty (TKA) were selected as control (TKA group). In addition to the range of motion (ROM) before operation showing significant difference between the two groups ( t=4.25, P=0.00), there was no significant difference in gender, age, disease duration, sides, body mass index, and preoperative hip-knee-ankle angle (HKA), Western Ontario and McMaster University Osteoarthritis Index (WOMAC) score between the two groups ( P>0.05). The incision length, drainage volume within 24 hours after operation, and the changes of hemoglobin and albumin were recorded. The WOMAC score, ROM, and HKA before and after operation were compared between the two groups. At 1 year after operation, the gait trajectory characteristics of two groups were analyzed by Vicon three-dimensional gait capture system, and the absolute symmetry index (ASI) of the lower limbs of the two groups was calculated.

Results

The incisions of the two groups healed by first intention, with no complications. The incision length, drainage volume within 24 hours, and the changes of hemoglobin and albumin after operation in the UKA group were significantly smaller than those in the control group ( P<0.05). All patients were followed up completely, the follow-up time ranged from 13 to 20 months of UKA group (mean, 18 months) and 16 to 24 months of control group (mean, 20 months). The imaging review showed that the lower limb alignment of the two groups were restored to a neutral position, and the position of prosthesis was good. At 1 year after operation, the WOMAC score, HKA, and ROM of two groups were significantly improved when compared with those before operation ( P<0.05); the postoperative WOMAC score and ROM of the UKA group were significantly better than those of the control group ( P<0.05), and there was no significant difference in HKA between the two groups ( t=1.54， P=0.13). Gait analysis at 1 year after operation showed that the walking speed, stride length, knee extension at mid-stance, and flexion at swing in the UKA group were significantly better than those in the TKA group ( P<0.05); there was no significant difference in cadence, knee flexion at initial contact, and knee flexion at loading response between the two groups ( P>0.05). The ASI of bilateral knee flexion in the UKA group was significantly greater than that in the TKA group during the initial contact and loading response period ( P<0.05).

Conclusion

Compared with TKA, UKA has the advantages of small incision, less blood loss, and quicker functional recovery. The early gait after UKA is mainly manifested as the increase in walking speed, stride length, knee flexion at swing, and extension at mid-stance phase. From the analysis of gait symmetry, during the initial contact and loading response phase, the operation side after UKA undertakes more shock absorption and joint stabilization functions than the contralateral side.

Fixed- versus mobile-bearing unicompartmental knee arthroplasty: a meta-analysis

Unicompartmental knee arthroplasty (UKA) can be either a fixed bearing (FB) or a mobile bearing (MB) construct with controversy as to which design is superior. This question is addressed with a systematic review and meta-analysis. A literature search was performed using PubMed, Embase and the Cochrane Library. Studies were reviewed according to the inclusion and exclusion criteria developed in advance. We compared the differences in clinical and radiological outcomes between the FB and MB UKAs. Analyses were performed with the Review Manager and STATA software. A total of 17 studies involving 2612 knees were included. No significant differences were presented between the FB and MB prostheses in clinical and radiological outcomes. However, it was evident that there were differences in the modes and timing of the failures, bearing dislocation led to earlier failures in the MB prosthesis, while the FB prosthesis failed later due to polyethylene wear. There was no evidence of publication bias using the incidence of revisions. There is no significant difference between the FB and MB UKAs; however, there are differences in the modes and timing of failures.

A comparison of gait characteristics between posterior stabilized total knee and fixed bearing unicompartmental knee arthroplasties

Background/Objective

According to previous studies, physiological gait pattern was found in unicompartmental knee arthroplasty (UKA) as compared to total knee arthroplasty (TKA) concerning the gait parameters including gait speed, cadence, and step length. However, little attention had been paid to the detailed kinematic and kinetic differences during gait between TKAs and UKAs. The aim of the present study was to investigate and to clarify the biomechanical differences between posterior stabilized TKAs and fixed bearing UKAs during walking.

Methods

A total of 28 patients participated in the present study. Fifteen patients who underwent TKA and thirteen patients who underwent UKA were enrolled. Gait analysis was done at an average of 12.9 months after surgery. The subjects performed level walking at a preferred speed. For each subject, three-dimensional kinematic, kinetic and ground reaction force data were recorded as well as clinical data including range of motion at the knee joint and plain radiographs. Differences of knee kinematics or kinetics were compared between TKAs and UKAs using two-tailed Mann Whitney U-test.

Results

On physical examination, passive range motion was significantly smaller in TKAs than in UKAs, while femorotibial angle on plain radiographs was not significantly different on plain radiographs. In terms of kinematics, TKAs were more flexed at heel contact and less extended in mid-stance phase compared to UKAs in the sagittal plane, and total excursion of TKAs were also smaller than UKAs. Regarding knee kinetics, TKA patients had significantly less peak tibial internal rotation moment in terminal stance phase. In addition, peak knee adduction moment was significantly larger in UKAs than in TKAs, while peak knee flexion moment was not significantly different.

Conclusion

Posterior stabilized TKAs exhibited less peak tibial internal rotation moment, which is known as pivot shift avoidance gait, in the present study, compared to fixed bearing UKAs. TKAs had similar gait pattern to anterior cruciate ligament deficient knees, compared to UKAs even if patients with TKAs had no subjective pain during walking.

In vivo kinematic comparison before and after mobile-bearing unicompartmental knee arthroplasty during high-flexion activities

BACKGROUND

Many patients who undergo unicompartmental knee arthroplasty (UKA) have an expectation that their knee flexion would increase following its replacement. Additionally, the survival rate of mobile-bearing UKA (MB-UKA) is high. However, the effect on the patient's kinematics remains unknown. This study aimed to clarify the kinematic effect of MB-UKA knees during high-flexion activities by comparing the in vivo kinematics before and after surgery.

METHODS

A squatting motion was performed under fluoroscopic surveillance in the sagittal plane before and after MB-UKA. To estimate the spatial position and orientation of the knee, a two-dimensional/three-dimensional registration technique was used. The femoral rotation and varus-valgus angle relative to the tibia and anteroposterior (AP) translation of the medial and lateral side of the femur on the plane perpendicular to the tibial mechanical axis in each flexion angle were evaluated.

RESULTS

Regarding the varus-valgus angle, the preoperative knees indicated a significant varus alignment compared with the postoperative knees from 10° to 60° of flexion. There were no significant differences in the femoral rotation angle, AP translation, and kinematic pathway before and after MB-UKA in the mid-flexion of the range of motion.

CONCLUSION

There were differences between the varus-valgus knee kinematics before and after MB-UKA, from 10 to 60° of flexion, but no difference from midrange of flexion to deep flexion. In addition, the rotational knee kinematics before and after MB-UKA was not significantly different.

Anatomy-mimetic design preserves natural kinematics of knee joint in patient-specific mobile-bearing unicompartmental knee arthroplasty

PURPOSE

This study aims to evaluate whether different tibial-femoral conformities for patient-specific mobile-bearing unicompartmental knee arthroplasties (UKAs) preserve natural knee kinematics, using computational simulations.

METHODS

Different designs for patient-specific mobile-bearing UKAs were evaluated using finite element analysis. Three designs for the identical femoral component were considered: flat (non-conforming design), anatomy-mimetic, and conforming for the tibial insert.

RESULTS

The conforming design for the patient-specific mobile-bearing UKAs exhibited a 1.2 mm and 0.7° decrease in the translation and rotation, respectively, in the swing phase compared with those of the natural knee. In addition, the femoral rollback and internal rotation were 2.6 mm and 1.2° lower, respectively, than those of the natural knee, for the conforming design under the deep-knee-bend condition. The flat design for the patient-specific mobile-bearing UKAs exhibited a 2.2 mm and 1.4° increase in the femoral rollback and rotation compared with the natural knee under the deep-knee-bend condition. The anatomy-mimetic patient-specific mobile-bearing UKAs best preserved the natural knee kinematics under the gait and deep-knee-bend loading conditions.

CONCLUSIONS

The kinematics of the loading conditions in patient-specific mobile-bearing UKAs was determined to closely resemble those of a native knee. In additional, by replacing the anatomy-mimetic design with a mobile-bearing, natural knee kinematics during gait and deep-knee-bend motions is preserved. These results confirm the importance of tibiofemoral conformity in preserving native knee kinematics in patient-specific mobile-bearing UKA.

Greater activity, better range of motion and higher quality of life following unicompartmental knee arthroplasty: a comparative case-control study

PURPOSE

The purpose of this study was to provide a matched cohort comparison of clinical and functional outcome scores, range of motion and quality of life following unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA). The hypothesis was that patients receiving UKA report better results than comparable patients who receive conventional TKA.

METHODS

Clinical and functional results of 35 patients with medial end-stage osteoarthritis who had received a fixed-bearing UKA were compared with the results of 35 matched patients who had received a TKA from the same manufacturer by the same surgeon. Outcome scores were measured before surgery and at final follow-up using Tegner Activity Scale (TAS), range of motion (ROM) and Short Form 36 Health Survey (SF-36). The Knee Society Score (KSS) was assessed at final follow-up. The mean observation period was 2.3 years in both groups.

RESULTS

The preoperative knee scores had no statistically significant differences between the two groups. Postoperatively, however, UKAs performed significantly better regarding TAS and ROM (4 vs. 3 and 118.4 vs. 103.7, respectively). The results of the SF-36 showed significantly better results for the UKA group in the mental component summary score and in the subscale of social function.

CONCLUSIONS

The present study suggests that UKA is associated with higher activity level, higher quality of life, and greater ROM when compared with TKA on comparable patients. Prolonged clinical follow-up in a larger patient cohort with a randomised-controlled study design would be beneficial to confirm these findings.

LEVEL OF EVIDENCE

III.

TRENDS IN UNICOMPARTMENTAL KNEE ARTHROPLASTY

Objective:

To evaluate trends in publications on unicompartmental knee arthroplasty (UKA) from the past to the present.

Methods:

As a web-based analysis, all UKA research articles, editorial letters, case reports, reviews and meeting abstracts published on the Thomson Reuters’ Web of Knowledge were evaluated. The period from the first publication in 1980 to January 2019 was divided into four decades and publications were evaluated. Research articles were grouped into headings according to the subjects.

Results:

A total of 1,658 publications were evaluated in this study. The most frequent term used in the publications title was “outcome,” with 260 items, followed by “biomechanics and kinematics,” with 99 items. Most reports have been published in the last decade, and the most common type of publication was postoperative follow-up and results.

Conclusion:

In parallel with technological advancements, publications related to UKA-especially patient-specific instrumentation, navigation, and robotic surgery-will increase in number and become more specific. Level of Evidence V, Expert Opinion.

Comparison of Fixed-Bearing and Mobile-Bearing Unicompartmental Knee Arthroplasty: A Systematic Review and Meta-Analysis

BACKGROUND

Prior studies have compared fixed-bearing unicompartmental knee arthroplasty (FB-UKA) with mobile-bearing UKA (MB-UKA), suggesting that both procedures have good clinical outcomes. However, which treatment is more beneficial for patients is controversial. The purpose of our study is to evaluate the postoperative outcomes, including the revision rate, complications, functional results, range of motion, and femoral-tibial angle, between the 2 procedures.

METHODS

We searched the MEDLINE, EMBASE, Cochrane Library, and Web of Science databases starting from August 2017 to May 2018. The publication date of articles was not restricted. Before we submit our contribution, we have re-searched it again. Articles that directly compared the postoperative outcomes of the 2 prosthesis type were included.

RESULTS

A total of 15 comparative studies were included in our meta-analysis. The pooled data indicated no differences between the 2 operation modes in terms of revision rates, complications, and knee function, but earlier failure occurred more frequently with the MB design.

CONCLUSION

Both the arthroplasty types provided satisfactory clinical results for patients with classic indications. However, MB-UKA tended to fail in early postoperative years whereas fixed-bearing UKA in later postoperative years. Therefore treatment options should be carefully considered for each patient, and surgeons should still use their personal experience when deciding between these options.

Comparison of gait kinematics in total and unicondylar knee replacement surgery

INTRODUCTION

This study is aimed to compare kinematic gait data of patients who have undergone total and unicondylar knee replacement.

MATERIALS AND METHODS

This single-surgeon retrospective cohort study evaluated 13 patients with unilateral total knee arthroplasty (TKA) and 14 unicondylar knee arthroplasty (UKA). Gait analysis was carried out using a Vicon motion analysis system. The limits of knee flexion during stance phase, at heel strike and at loading response were measured.

RESULTS

The total range of motion of the UKA knees was significantly greater than the TKA knees. UKA knees exhibited significantly greater knee extension during the stance phase than the TKA knees. Unlike TKA, UKA knees demonstrated improved knee flexion during the gait cycle when compared to the contralateral non-operated knee. The hips also demonstrated near normal hip flexion in UKA patients. Predictably, UKA knees had significantly greater varus compared with TKA in the coronal plane. Spatiotemporal variables demonstrated similar walking speed and step length to aid a fair comparison between knee replacement groups.

CONCLUSIONS

The UKA knees moved more physiologically in the sagittal plane with a greater range of motion during gait. Despite having a stiff gait pattern, the patients undergoing TKA demonstrated a more neutral alignment in the coronal plane. Neither type of knee arthroplasty restored knee kinematics to those of the non-operated side.

Unicompartmental knee arthroplasty fails to completely restore normal gait patterns during level walking

PURPOSE

Gait analysis is a valuable instrument for measuring function objectively after unicompartmental knee arthroplasty (UKA). However, most gait analysis studies have reported conflicting results for functional assessment after UKA. This meta-analysis compared the gait patterns of UKA patients and healthy controls during level walking.

METHODS

Studies were included in the meta-analysis if they recorded vertical ground reaction force (GRF), flexion at initial contact, flexion at loading response, extension at mid-stance, flexion at swing, walking speed, cadence, and stride length in UKA patients or healthy controls.

RESULTS

Seven studies met the criteria for inclusion in the meta-analysis. The UKA patients and healthy controls were similar in terms of vertical GRF (95% CI - 0.54 to 0.23; ns), flexion at initial contact (95% CI - 0.47 to 4.96; ns), flexion at loading response (95% CI - 1.29 to 3.69; ns), and flexion at swing (95% CI - 8.85 to 0.40; ns). In contrast, extension at mid-stance (95% CI 0.53 to 4.88; P = 0.01), walking speed (95% CI - 2.13 to - 0.15; P = 0.02), cadence (95% CI - 1.02 to - 0.25; P = 0.001), and stride length (95% CI - 2.02 to - 0.22; P = 0.01) differed significantly between groups. Subgroup analyses revealed that the pooled data were similar between groups: 1st maximum (heel strike), - 0.43 BW (ns); 1st minimum (mid-stance), 0.61 BW (ns); and 2nd maximum (toe off), - 0.46 BW (ns).

CONCLUSIONS

There were no significant differences in vertical GRF or overall kinematics in the sagittal plane between UKA patients and healthy controls during level walking. However, the UKA group had a significantly slower walking speed and cadence and a shorter stride length than healthy controls. The current findings suggest that, clinically, UKA fails to completely restore normal gait patterns.

LEVEL OF EVIDENCE

Level II, therapeutic study.

How does the inclination of the tibial component matter? A three-dimensional finite element analysis of medial mobile-bearing unicompartmental arthroplasty

BACKGROUND

Medial unicompartmental knee arthroplasty (UKA) using Oxford mobile-bearing prosthesis is performed in the treatment of medial compartmental arthritis of the knee. However, little is known about the stress distributions for mobile-bearing UKA on the medial tibial plateau.

METHODS

In this study, the stresses on the coronal plane were calculated in a three-dimensional model of the proximal tibia. The features of the stress distribution were investigated when the tibial tray was placed in 15°, 10°, six degrees, and three degrees varus, neutral (0°), and in three degrees, six degrees, 10°, and 15° valgus on the coronal plane of the medial plateau.

RESULTS

The peak von Mises stress was found on the cortex below the medial plateau while the stresses of cortical bone increased gradually as the inclination of the tibial tray was changed from varus to valgus. The amount of peak stress was almost the same as that in the normal knee model when the tibial tray was placed in six degrees valgus and consistently lower in varus inclination than in the normal knee model. Conversely, the peak stress of soft bone was found at the bottom of the slot.

CONCLUSIONS

This study demonstrates that the inclination of the tibial component affects stress distribution in the proximal tibia after UKA. Slight varus inclination of the mobile-bearing tibial component is acceptable as it lowers the peak stress on the medial cortex. Additionally, placing the tibial tray in slight varus avoids a rise in stress between the tip of the keel and the medial tibial cortex.

Instrumented gait analysis in patients with medial osteoarthritis of the knee after mobile-bearing unicompartmental knee arthroplasty

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is an effective treatment for patients with medial osteoarthritis of the knee joint. Instrumented gait analysis provides an objective measure to quantify and qualify postoperative changes of gait. The purpose of this study was to evaluate standardized instrumented gait analysis for functional recovery and gait as an outcome of mobile-bearing UKA in patients with medial osteoarthritis of the knee.

METHODS

Twenty-one patients with isolated medial osteoarthritis of the knee joint received mobile-bearing UKA. They were examined by a gait analysis before surgery and after an average follow-up time of seven months. Gait analysis was performed on a treadmill with six infrared-cameras to identify changes of gait characteristics (e.g., velocity, stride time, stride length, knee adduction and hip abduction).

RESULTS

Mean velocity (chosen by individuals) increased from 0.61 to 0.76m/s and further significant advancements, particularly in the knee adduction and the hip abduction were detected. Time and length of strides improved significantly as well as the clinical scores American Knee Society Score (AKSS), Oxford-12, Hannover Functional Ability Questionnaire for Osteoarthritis (FFbH-OA) Score and Devane Score.

CONCLUSION

Mobile-bearing UKA can restore physiological axis of the leg and improve gait and function of the knee joint. The combination of instrumented gait analysis with clinical scores constitutes an eligible measuring instrument to quantify and qualify changes in patients' gait patterns.

Assessment of patient functional performance in different knee arthroplasty designs during unconstrained squat

Background

In this paper, squat named by Authors unconstrained because performed without constrains related to feet position, speed, knee maximum angle to be reached, was tested as motor task revealing differences in functional performance after knee arthroplasty. It involves large joints ranges of motion, does not compromise joint safety and requires accurate control strategies to maintain balance.

Methods

Motion capture techniques were used to study squat on a healthy control group (CTR) and on three groups, each characterised by a specific knee arthroplasty design: a Total Knee Arthroplasty (TKA), a Mobile Bearing and a Fixed Bearing Unicompartmental Knee Arthroplasty (respectively MBUA and FBUA). Squat was analysed during descent, maintenance and ascent phase and described by speed, angular kinematics of lower and upper body, the Center of Pressure (CoP) trajectory and muscle activation timing of quadriceps and biceps femoris.

Results

Compared to CTR, for TKA and MBUA knee maximum flexion was lower, vertical speed during descent and ascent reduced and the duration of whole movement was longer. CoP mean distance was higher for all arthroplasty groups during descent as higher was, CoP mean velocity for MBUA and TKA during ascent and descent.

Conclusions

Unconstrained squat is able to reveal differences in the functional performance among control and arthroplasty groups and between different arthroplasty designs. Considering the similarity index calculated for the variables showing statistically significance, FBUA performance appears to be closest to that of the CTR group.

Level of evidence

III a.

Kinematics of mobile-bearing unicompartmental knee arthroplasty compared to native: results from an in vitro study

INTRODUCTION

Fixed-bearing unicompartmental knee arthroplasty (UKA) closely replicates native knee kinematics. As few studies have assessed kinematics following mobile-bearing (MB) UKA, the current study aimed to investigate whether MB UKA preserves natural knee kinematics.

MATERIALS AND METHODS

Seven fresh-frozen full-leg cadaver specimens were prepared and mounted in a kinematic rig that allowed all degrees of freedom at the knee. Three motion patterns, passive flexion-extension (0°-110° flexion), open-chain extension (5°-70° flexion) and squatting (30°-100° flexion), were performed pre- and post-implantation of a medial MB UKA and compared in terms of rotational and translational knee joint kinematics in the different anatomical planes, respectively.

RESULTS

In terms of frontal plane rotational kinematics, MB UKA specimens were in a more valgus orientation for all motion patterns. In the axial plane, internal rotation of the tibia before and after UKA was consistent, regardless of motion task, with no significant differences. In terms of frontal plane, i.e., inferior-superior, translations, the FMCC was significantly higher in UKA knees in all flexion angles and motor tasks, except in early flexion during passive motion. In terms of axial plane, i.e., anteroposterior (AP), translations, during open-chain activities, the femoral medial condyle center (FMCC) tended to be more posterior following UKA relative to the native knee in mid-flexion and above. AP excursions of the FMCC were small in all tested motions, however. There was substantial AP translation of the femoral lateral condyle center during passive motion before and after UKA, which was significantly different for flexion angles > 38°.

CONCLUSIONS

Our study data demonstrate that the kinematics of the unloaded knee following MB UKA closely resemble those of the native knee while relative medial overstuffing with UKA will result in the joint being more valgus. However, replacing the conforming and rigidly fixed medial meniscus with a mobile inlay may successfully prevent aberrant posterior translation of the medial femoral compartment during passive motion and squatting motion.

Gait comparison of unicompartmental and total knee arthroplasties with healthy controls

Aims

To compare the gait of unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) patients with healthy controls, using a machine-learning approach.

Patients and Methods

145 participants (121 healthy controls, 12 patients with cruciate-retaining TKA, and 12 with mobile-bearing medial UKA) were recruited. The TKA and UKA patients were a minimum of 12 months post-operative, and matched for pattern and severity of arthrosis, age, and body mass index.

Participants walked on an instrumented treadmill until their maximum walking speed was reached. Temporospatial gait parameters, and vertical ground reaction force data, were captured at each speed. Oxford knee scores (OKS) were also collected. An ensemble of trees algorithm was used to analyse the data: 27 gait variables were used to train classification trees for each speed, with a binary output prediction of whether these variables were derived from a UKA or TKA patient. Healthy control gait data was then tested by the decision trees at each speed and a final classification (UKA or TKA) reached for each subject in a majority voting manner over all gait cycles and speeds. Top walking speed was also recorded.

Results

92% of the healthy controls were classified by the decision tree as a UKA, 5% as a TKA, and 3% were unclassified. There was no significant difference in OKS between the UKA and TKA patients (p = 0.077). Top walking speed in TKA patients (1.6 m/s; 1.3 to 2.1) was significantly lower than that of both the UKA group (2.2 m/s; 1.8 to 2.7) and healthy controls (2.2 m/s; 1.5 to 2.7; p < 0.001).

Conclusion

UKA results in a more physiological gait compared with TKA, and a higher top walking speed. This difference in function was not detected by the OKS.

Cite this article: Bone Joint J 2016;98-B(10 Suppl B):16–21.

A cost comparison of unicompartmental and total knee arthroplasty

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is an alternative to total knee arthroplasty (TKA) in appropriately selected patients. There is a paucity of data comparing hospital resource utilization and costs for UKA versus TKA.

METHODS

We retrospectively reviewed 128 patients who underwent UKA or TKA for osteoarthritis by a single surgeon in the 2011 Fiscal Year. Sixty-four patients in each group were matched based on sex, age, race, body mass index, Charlson Comorbidity Index, and insurance type. Clinical data were obtained from medical records while costs were obtained from hospital billing. Bivariate analyses were used to compare outcomes.

RESULTS

Both anesthesia and operative time (minutes) were significantly shorter for patients undergoing UKA (125.7 vs. 156.4; p<0.001, and 81.4 vs. 112.2; p<0.001). UKA patients required fewer transfusions (0% vs. 11.0%; p=0.007) and had a shorter hospital stay (2.2 vs. 3.8days; p<0.001). 96% of UKAs were discharged home compared with 75% of TKAs (p<0.001). Hospital direct costs were lower for UKA ($7893 vs. $11,156; p<0.001) as were total costs (hospital direct costs plus overhead; $11,397 vs. $16,243; p<0.001). Supply costs and implant costs were similarly lower for UKA ($701 vs. $781; p<0.001, and $3448 vs. $5006; p<0.001).

CONCLUSION

Our data suggest that UKA provides a cost-effective alternative to TKA in appropriately selected patients. As the number of patients with end-stage arthritis of the knee requiring surgical care continues to rise, the costs of caring for these patients must be considered.

LEVEL OF EVIDENCE

Level III, case control study.

The efficacy of early initiated, supervised, progressive resistance training compared to unsupervised, home-based exercise after unicompartmental knee arthroplasty: a single-blinded randomized controlled trial

Objective:

To examine if supervised progressive resistance training was superior to home-based exercise in rehabilitation after unicompartmental knee arthroplasty.

Design:

Single blinded, randomized clinical trial.

Setting:

Surgery, progressive resistance training and testing was carried out at Aarhus University Hospital and home-based exercise was carried out in the home of the patient.

Subjects:

Fifty five patients were randomized to either progressive resistance training or home-based exercise.

Intervention:

Patients were randomized to either progressive resistance training (home based exercise five days/week and progressive resistance training two days/week) or control group (home based exercise seven days/week).

Main measures:

Preoperative assessment, 10-week (primary endpoint) and one-year follow-up were performed for leg extension power, spatiotemporal gait parameters and knee injury and osteoarthritis outcome score (KOOS).

Results:

Forty patients (73%) completed 1-year follow-up. Patients in the progressive resistance training group participated in average 11 of 16 training sessions. Leg extension power increased from baseline to 10-week follow-up in progressive resistance training group (progressive resistance training: 0.28 W/kg, P= 0.01, control group: 0.01 W/kg, P=0.93) with no between-group difference. Walking speed and KOOS scores increased from baseline to 10-week follow-up in both groups with no between-group difference (six minutes walk test P=0.63, KOOS P>0.29).

Conclusions:

Progressive resistance training two days/week combined with home based exercise five days/week was not superior to home based exercise seven days/week in improving leg extension power of the operated leg.

Patient Reported Kneeling Ability in Fixed and Mobile Bearing Knee Arthroplasty

Kneeling is an important function of the knee joint required for many daily activities. Bearing type is thought to influence functional outcome following UKA and TKA. Self-reported kneeling ability was recorded in 471 UKA and 206 TKA patients with fixed or mobile bearing implants. Kneeling ability was recorded from the Oxford Knee Score question 7. The self-reported ability to kneel was similar in patients with fixed and mobile bearing UKA implants following surgery. In TKA, greater proportions of patients were able to kneel in the fixed compared to the mobile bearing groups up to two years after surgery indicating that self-reported kneeling ability is enhanced in fixed compared to mobile bearing TKA.

Fixed- versus mobile-bearing UKA: a systematic review and meta-analysis

PURPOSE

Two design concepts are currently used for unicondylar knee arthroplasty (UKA) prostheses: fixed bearing (FB) and mobile bearing (MB). While MB prostheses have theoretical advantages over their FB counterparts, it is not clear whether they are associated with better outcomes. A systematic review was conducted to examine survivorship differences and differences in failure modes of between FB and MB designs.

METHODS

PubMed, Scirus and Cochrane library databases were searched for medial UKA outcome studies. A total of 44 papers, involving 9,463 knees, were eligible. Outcomes examined included knee function, survivorship and the reasons for, and incidence of, revision for FB and MB prostheses. Random effects meta-analysis was employed to obtain pooled revision rate estimates. Where available, cause-specific time to revision was extracted.

RESULTS

Mean follow-up was 8.7 years for FB and 5.9 years for MB prostheses. There were no other relevant baseline differences. The overall crude revision rate for FB and for MB prostheses was 0.90 (95 % confidence interval (CI) 0.65-1.21) and 1.51 (95 % CI 1.11-1.93) per 100 component years, respectively. After stratification on follow-up time and age, the revision rates were not substantially different, aside for younger patients in short term from studies with short-term follow-up.

CONCLUSION

No essential differences between the two designs were observed. MB and FB UKA designs have comparable revision rates. As our study is based on predominantly observational data, with large variations in reporting standards, inferences should be drawn with caution.

LEVEL OF EVIDENCE

IV.

Outcome of Unicompartmental Knee Arthroplasty: A Systematic Review of Comparative Studies between Fixed and Mobile Bearings Focusing on Complications

The purpose of this systematic review is to collate results of studies comparing fixed and mobile bearing unicompartmental knee arthroplasty (UKA), focusing on complications and timing for reoperations. Out of 723 results derived from PubMed, EMBASE and Cochrane database search engines on bearings in arthroplasty, 10 studies comparing clinical results of fixed bearings to mobile bearings in UKA were found eligible for analysis. The reoperation rate was calculated using a novel method such as reoperations per hundred component years, and the causes of specific reoperations were investigated. The overall reoperation rate per hundred component years was similar between the mobile bearings (1.392) and fixed bearings (1.377); however, mobile bearings were more susceptible to reoperations in cases with aseptic loosening (0.393>0.255), progression of arthritis (0.428>0.357) and implant dislocation (0.286>0). The overall incidence of complications is similar for fixed and mobile bearing designs in UKA. The discussion on complications presented above may assist surgeons in their choice of bearing design.

Change of gait in patients with lateral osteoarthritis of the knee after mobile-bearing unicompartmental knee arthroplasty

PURPOSE

Patients with lateral osteoarthritis of the knee suffer not only from pain but also impaired gait and limited mobility. Common treatment options are total knee replacement and lateral unicompartmental knee arthroplasty (UKA). The domed lateral mobile-bearing Oxford Uni is a new treatment option for patients with isolated osteoarthritis of the lateral compartment of the knee joint. We used instrumented gait analysis and clinical scores to study patients before and after lateral UKA.

METHODS

Nineteen patients suffering from lateral osteoarthritis underwent implantation of a mobile-bearing lateral UKA. They were examined in a gait analysis before the operation and after an average follow-up time of 7 months. Gait analysis was performed on a treadmill with six infrared cameras to identify gait characteristics (e.g. velocity, stride time, stride length, knee abduction or hip adduction).

RESULTS

Mean velocity changed from 0.58 to 0.73 m/s. Significant advancements were also found in knee abduction and hip adduction. Time and length of strides improved significantly as well as the clinical scores American Knee Society Score, Oxford-12, FFb-H-OA and Devane Score.

CONCLUSION

Patients with lateral osteoarthritis of the knee showed an impaired gait with an increased knee abduction and hip adduction angle. Implantation of a lateral mobile UKA can restore normal axis of the leg and improve gait and function of the knee. Instrumented gait analysis is a suitable measuring instrument to quantify and qualify the post-operative change of gait.

LEVEL OF EVIDENCE

II.

Motion analysis of patients after knee arthroplasty during activities of daily living--a systematic review

BACKGROUND

Motion analysis with optoelectronic systems is a frequently used method to analyze the patient's gait as well as further relevant activities of daily living before and after knee arthroplasty. The aim of this systematic review was to identify the investigated activities of daily living and to show an extensive presentation of gait analysis studies with patients after knee arthroplasty surgery.

METHODS

The articles were searched in electronic databases: MEDPILOT, EMBASE. To identify articles that potentially met the inclusion criteria the titles and abstracts were screened. The level of evidence was analyzed for the included articles.

RESULTS

Overall 3989 abstracts were reviewed and 87 full text articles were included. Ten activities of daily living were identified. Level walking was the most frequently investigated activity (78.2%). In 94.6% the sagittal plane kinematics were analyzed and 5.3% presented the results in all three planes. Knee adduction moments were determined in 33.3% of the included articles. At least two joints were investigated in 40.2%, including the impaired knee and further body parts (ankle, hip, pelvis, trunk). Unicondylar knee arthroplasty was addressed in 14.1%.

CONCLUSIONS

Besides level walking, it is necessary to examine physical more demanding activities of daily living to detect potential kinematic and kinetic abnormalities. Further research should imply the evaluation of sagittal, frontal and transverse plane joint and muscle function based on accurate inverse-dynamic techniques. More motion analysis studies are necessary that address unicondylar knee arthroplasty in comparison to total knee arthroplasty and healthy controls.

Difference in knee rotation between total and unicompartmental knee arthroplasties during stair climbing

PURPOSE

The purpose of this study was to compare knee kinematics during stair walking in patients with simultaneous total knee arthroplasty (TKA) and unicompartmental knee arthroplasties (UKA). It was hypothesized that UKA would reproduce more normalized knee kinematics than TKA during stair ascent and descent.

METHODS

Six patients who received UKA in one knee and TKA in the other knee were included in the study. For this study, a four-step staircase was assembled with two force platforms being positioned at the centre of the second and third steps. Each patient was attached with 16 reflective markers at both lower extremities and was asked to perform five roundtrip trials of stair climbing. Kinematic parameters including stance duration, knee angle, vertical ground reaction force (GRF), joint reaction force, and moments were obtained and analysed using a10-camera motion system (VICON, Oxford, UK). Nonparametric Friedman test was used to compare the results between two arthroplasty methods and between stair ascent and descent.

RESULTS

Compared to TKA, UKA knees exhibited significantly greater degree of rotation in transverse planes (5.0 degrees during ascent and 6.0 degrees during descent on average), but showed no difference in terms of the other parameters. When comparing the results during stair ascent with descent, overall greater knee angle, vertical GRF, joint reaction force, and moment were observed during stair descent.

CONCLUSIONS

Both UKA and TKA knees have shown overall similar knee kinematics, though UKA knee may allow greater degree of rotation freedom, which resembles normal knee kinematics during stair walking.

UKA closely preserves natural knee kinematics in vitro

PURPOSE

It is assumed that unicondylar knee arthroplasty (UKA) features kinematics close to the natural knee. Clinical studies have also shown functional benefits for UKA. There is to date only little biomechanical data to support or explain these findings. The purpose of this study was to investigate whether UKA is able to preserve natural knee kinematics or not.

METHODS

Six fresh frozen full leg cadaver specimens were prepared to be mounted in a kinematic rig with six degrees of freedom for the knee joint. Three motion patterns were applied before and after medial UKA: passive flexion-extension, open chain extension, and squatting. During the loaded motions, quadriceps and hamstrings muscle forces were applied. Infrared cameras continuously recorded the trajectories of marker frames rigidly attached to femur, tibia, and patella. Prior computer tomography allowed identification of coordinate frames of the bones and calculations of anatomical rotations and translations.

RESULTS

Native kinematics was reproduced after UKA in all the specimens. In the unloaded knee and during open chain extension, femoral rollback patterns after UKA were very close to those in the native knee. During squatting, the medial femoral condyle after UKA tended to be more posterior and superior with flexion and there was less tibial internal rotation. The tibia was found to be more in valgus after UKA during all motion patterns.

CONCLUSION

As ligaments, lateral compartment and patellofemoral anatomy are preserved with UKA; the unloaded knee closely resembles native kinematics. The slight kinematic changes that were found under load are probably due to loss of the conforming medial meniscus and to the mismatch in geometry and stiffness introduced by UKA. These patterns resemble those found in knees with significant loss of function of the medial meniscus.

No clinical benefit of gender-specific total knee arthroplasty

BACKGROUND AND PURPOSE

There is no consensus regarding the clinical relevance of gender-specific prostheses in total knee arthroplasty (TKA). We summarize the current best evidence in a comparison of clinical and radiographic outcomes between gender-specific prostheses and standard unisex prostheses in female patients.

METHODS

We used the PubMed, Embase, Cochrane, Science Citation Index, and Scopus databases. We included randomized controlled trials published up to January 2013 that compared gender-specific prostheses with standard unisex prostheses in female patients who underwent primary TKAs.

RESULTS

6 trials involving 423 patients with 846 knee joints met the inclusion criteria. No statistically significant differences were observed between the 2 designs regarding pain, range of motion (ROM), knee scores, satisfaction, preference, complications, and radiographic results. The gender-specific design (Gender Solutions; Zimmer Inc, Warsaw, Indiana) reduced the prevalence of overhang. However, it had less overall coverage of the femoral condyles compared to the unisex group. In fact, the femoral prosthesis in the standard unisex group matched better than that in the gender-specific group.

INTERPRETATION

Gender-specific prostheses do not appear to confer any benefit in terms of clinician- and patient-reported outcomes for the female knee.

Fixed- versus mobile-bearing unicondylar knee arthroplasty: are failure modes different?

PURPOSE

An ongoing controversy exists on whether mobile-bearing design is superior over fixed-bearing design in unicondylar knee arthroplasties (UKAs). The present study conducted a systematic review to ascertain differences in performance between fixed- and mobile-bearing designs in UKAs.

METHODS

A literature search was performed in PubMed, Embase, Scopus and the Cochrane Library. A total of 9 comparative studies involving 915 knees comparing outcomes of mobile-bearing UKAs with fixed-bearing UKAs were included in the current analysis. Outcomes of interest included knee function, quality of life, radiographic outcomes, reasons and incidence of reoperation, timing of failures, and survivorship.

RESULTS

The results presented no significant differences between the two designs in terms of knee scores, range of motion, limb alignment, implant positioning, incidence of radiolucent lines and overall reoperation rates. However, their differences have been noted in their modes and timing of failures. Early failures are related to the risk of bearing dislocation in the mobile-bearing design. In contrast, later failures are related to the risk of polyethylene wear in the fixed-bearing design.

CONCLUSIONS

The available evidence has not confirmed the advantage of mobile-bearing UKAs over fixed-bearing UKAs but pointed out specific modes of failure.

Is bicompartmental knee arthroplasty more favourable to knee muscle strength and physical performance compared to total knee arthroplasty?

PURPOSE

Bicompartmental knee arthroplasty features bone and ligament sparing as unicompartmental knee arthroplasty and is presumably better in the recovery of muscle strength and function compared to total knee arthroplasty (TKA) though not previously reported in the literature. The aim of the study was to compare isokinetic knee muscle strength and physical performance in patients who underwent either bicompartmental knee arthroplasty or TKA.

METHODS

Each of 24 patients (31 knees) was prospectively examined preoperatively, at 6 and 12 months after each surgery. Isokinetic knee extensor and flexor strength as well as position sense were measured using the Biodex system. Timed up and go test, stair climbing test, and the 6-min walk test were used to assess physical performance. The results of each group were also compared with those from the corresponding healthy control, respectively.

RESULTS

Demography showed significant difference in the mean age between bicompartment (54.8 ± 5.6 years) and TKA groups (65.7 ± 6.7 years). Comparing between the two groups, knee extensor and flexor torque, hamstring/Quadriceps ratio, position sense, and physical performance were not significantly different preoperatively, at 6 and 12 months after surgery. In intra-group analysis, muscle strength and position sense at each time point were not different in both groups. In physical performance, both groups resulted in improvement in the 6-min walk test, and only TKA group showed enhancement in stair climbing test.

CONCLUSIONS

Although theoretically plausible, bicompartmental knee arthroplasty was not superior in knee muscle strength and physical performance at 1 year compared with total knee arthroplasty.

Unicompartmental knee arthroplasty enables near normal gait at higher speeds, unlike total knee arthroplasty

Top walking speed (TWS) was used to compare UKA with TKA. Two groups of 23 patients, well matched for age, gender, height and weight and radiological severity were recruited based on high functional scores, more than twelve months post UKA or TKA. These were compared with 14 preop patients and 14 normal controls. Their gait was measured at increasing speeds on a treadmill instrumented with force plates. Both arthroplasty groups were significantly faster than the preop OA group. TKA patients walked substantially faster than any previously reported series of knee arthroplasties. UKA patients walked 10% faster than TKA, although not as fast as the normal controls. Stride length was 5% greater and stance time 7% shorter following UKA - both much closer to normal than TKA. Unlike TKA, UKA enables a near normal gait one year after surgery.

Variability of gait parameters in patients with total knee arthroplasty

PURPOSE

Gait analysis has provided important information about the variability of gait for patients prior to and after total knee arthroplasty (TKA). The objective of this research was to clarify how the different surgical techniques influence gait variability.

METHODS

Gait analysis was performed at 0.8, 1.0, and 1.2 m/s in three groups of patients (operated on using the conventional technique, conventional technique combined with computer-assisted navigation, and the minimally invasive technique combined with computer-assisted navigation; n = 15 each) and a control group (n = 15; healthy, age, body mass, and body height matched). Gait analysis was performed preoperatively and 6 and 12 months after the surgery. Gait parameter variability was characterized by the coefficient of variance of spatio-temporal parameters and by the mean coefficient of variance of angular parameters.

RESULTS

One year after surgery, the variability of spatio-temporal parameters recovered to normal in patients operated on using the conventional technique; however, the variability of articular motion of the affected side decreased and the variability of articular motion of the non-affected side and pelvis increased compared to the control group. In patients operated on using the minimally invasive technique, the variability of spatio-temporal and angular parameters was similar to that of the control group.

CONCLUSION

The type of surgical technique significantly influences the variability and stability of gait. Difference in the variability of angular parameters predicts gait instability and increased risk of falling after TKA with the conventional surgical technique. The minimally invasive technique ensures a recovery of gait variability and stability. Thus, particular attention must be paid to improving gait stability during postoperative rehabilitation.

LEVEL OF EVIDENCE

II.