The unicompartmental knee is the preferred side in individuals with both a unicompartmental and total knee arthroplasty

Conversion of UKA to TKA using identical standard implants-How does it compare to primary UKA, primary TKA and revision TKA?

BACKGROUND

UKA is a well-established treatment option for anteromedial osteoarthritis of the knee, resulting in superior functional outcomes but also higher revision rates than TKA. This study aimed to compare the outcomes of UKA, TKA, UKA converted to TKA using identical standard implants and revised TKA to support clinical decision-making.

METHODS

In this study, we retrospectively examined 116 patients who underwent UKA, 77 patients who received TKA, 28 patients whose UKA was converted to TKA using identical standard implants, and 21 patients who had a one-stage revision of TKA. The mean age at operation was 66.5 years (39-90 years), with a mean BMI of 28.8 kg/m2 (17.4-58.8) and a mean follow-up period of four years (0.9-9.9 years). We assessed various PROMs, including Oxford Knee Score, UCLA score, KSS score, and a modified WOMAC-Score as well as patient satisfaction and ability to resume daily activities, work, and sports.

RESULTS

The highest patient satisfaction was seen in the UKA. All scores were significantly higher for UKA than for TKA, converted UKA, and revised TKA. None of the scores showed a significant inferiority of converted UKA to TKA. In the case of revision, two scores showed significantly better results for converted UKA than for revised TKA.

CONCLUSIONS

Our results indicated that patients initially treated with UKA did not have significantly worse functional outcomes after conversion to TKA, given the use of identical standard implants. This highlights the effectiveness of UKA as a therapeutic option with outcomes superior to those of primary TKA and the importance of a bone-sparing procedure. Conversely, revision TKA is linked to poorer functional outcomes compared to both primary arthroplasties.

Cruciate-Retaining Total Knee Arthroplasty versus Unicompartmental Knee Arthroplasty in Medial Compartmental Osteoarthritis: A Propensity Score-Matched Analysis of Early Postoperative Recovery

Background

Cruciate-retaining (CR) total knee arthroplasty (TKA) may provide better physiological knee kinematics, proprioception, and quadricep recovery than posterior-stabilized (PS) TKA. Therefore, we hypothesized that CR TKA with multimodal pain control may provide comparable postoperative pain and recovery as unicompartmental knee arthroplasty (UKA).

Methods

This study included patients with isolated medial compartment knee osteoarthritis who underwent CR TKA and UKA. TKA and UKA patients were propensity score-matched with age and body mass index (BMI) and compared using visual analog scales (VAS) for pain scores, total amount of morphine use (TMU), knee flexion angle, straight leg raise (SLR), independent ambulation, length of hospital stay (LOS), and costs during hospitalization.

Results

After propensity score matching, 46 patients were included in the TKA and UKA groups, respectively, with no differences in demographic data. VAS at 6-72 h and TMU at 48 h after surgery were comparable between the groups. The knee flexion angle in the UKA group was significantly higher at 24 h (60.0° vs 46.6°; p<0.001) and 48 h (76.9° vs 69.1°; p = 0.021) than that in the TKA group. The SLR in the UKA group was significantly higher than that in the TKA group at 24-72 h. The UKA group ambulated significantly earlier (1.56 vs 2.13 days; p<0.001), had shorter LOS (3.68 vs 4.28 days; p<0.004) and incurred 12.43% lower costs when compared to the TKA group.

Conclusion

Patients who underwent CR TKA with multimodal pain management did not experience more postoperative pain or morphine use than those who underwent UKA. However, UKA patients seem to experienced faster recovery and shorter LOS than CR-TKA patients during the early postoperative course. Accordingly, UKA may be considered instead of TKA for patients who are good candidates for UKA and require expedited recovery.

What Role Does Patello-Femoral Joint Degeneration Have on Pain and Function After Unicompartmental Knee Arthroplasty? A Prospective Observational Cohort Study

BACKGROUND

Influences on anterior knee pain, stair climbing limitations, and function such as rising from sitting are poorly understood in unicompartmental knee arthroplasty (UKA). Original indications for UKA excluded patients who had patello-femoral disease, while more recent studies have expanded the indications to include these patients. This study examined the influence of the patello-femoral joint degeneration on patient-reported outcome measures relating to anterior knee pain and function after UKA.

METHODS

Between October 2017 and August 2021, Knee Injury and Osteoarthritis Outcome Score of Joint Replacement (KOOS, JR) patient-reported outcome measures were collected preoperatively and at 12 months of follow-up for 678 medial UKAs. Patello-femoral joint status was visually graded intraoperatively. Radiographic or intraoperative medial patellar facet and trochlear patello-femoral arthritis and preoperative anterior knee pain were not considered contraindications for UKA, while grade IV lateral patello-femoral arthritis was considered a contraindication for UKA. Multivariable ordinal logistic regressions were performed, using the KOOS, JR questionnaire assessing pain during stair climbing, standing upright, and function during rising from sitting. Independent regressions were performed for each targeted KOOS, JR question, with adjustments for age at surgery, sex, and baseline pain and function scores.

RESULTS

No association was observed between 12-month postoperative anterior knee pain (P = .575) and function (P = .854) with patellar osteoarthritis grading after UKA. When comparing fixed and mobile-bearing UKA designs, no association was observed between bearing type and pain (P = .663) or functional outcomes (P = .758).

CONCLUSION

Pain and function improved significantly following medial UKA and was independent of medial patellar and trochlear degenerative status.

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 accuracy for hip-knee-ankle (HKA) angle by X-ray and knee motion analysis system and the relationships between HKA and gait posture

BACKGROUND

The lower limb mechanical axis was used to assess the severity of knee osteoarthritis (KOA) with varus/valgus deformity and the accuracy of targeted lower limb alignment correction after operation by conventional X-rays. There are lots of parameters to assess the gait in elder patients such as velocity, stride length, step width and swing/stance ratio by knee joint movement analysis system. However, the correlation between the lower limb mechanical axis and gait parameters is not clear. This study is aimed at obtaining the accuracy of the lower limb mechanical axis by the knee joint movement analysis system and the correlation between the lower limb mechanical axis and gait parameters.

METHODS

We analysed 3D knee kinematics during ground gait of 99 patients with KOA and 80 patients 6 months after the operations with the vivo infrared navigation 3D portable knee joint movement analysis system (Opti-Knee®, Innomotion Inc, Shanghai, China). The HKA (Hip-Knee-Ankle) value was calculated and compared to X-ray findings.

RESULTS

HKA absolute variation after the operation was 0.83 ± 3.76°, which is lower than that before the operation (5.41 ± 6.20°, p = 0.001) and also lower than the entire cohort (3.36 ± 5.72). Throughout the cohort, a significant correlation with low coefficients (r = -0.19, p = 0.01) between HKA value and anterior-posterior displacement was found. In comparing the HKA values measured on the full-length alignment radiographs and 3D knee joint movement analysis system (Opti-Knee), there was a significant correlation with moderate to high coefficients (r = 0.784 to 0.976). The linear correlation analysis showed that there was a significant correlation between the values of HKA measured by X-ray and movement analysis system (R² = 0.90, p < 0.01).

CONCLUSIONS

Data with equivalent results as HKA, the 6DOF of the knee and ground gait data could be provided by infrared navigation based 3D portable knee joint movement analysis system comparing with the conventional X-rays. There is no significant effect of HKA on the kinematics of the partial knee joint.

A standardized technique for lateral unicompartmental knee arthroplasty

OBJECTIVES

We developed a new standardized procedure for lateral unicompartmental knee arthroplasty (UKA) to maximize the benefits and minimize the risks of surgery in patients with osteoarthritis (OA).

METHODS

This retrospective study recruited patients who underwent lateral UKA at our hospital between January 2014 and January 2016. Demographic characteristics and preoperative and postoperative American Knee Society (AKS) clinical scores (including pain, clinical, and knee mobility scores) were collected.

RESULTS

A total of 158 patients (35 male and 123 female) who underwent 160 lateral UKAs were analyzed. Their AKS clinical scores (0-100 points) improved from 53.1 ± 4.1 (range 45-62) preoperatively to 97.0 ± 1.7 (range 92-99) (p < 0.001) postoperatively with additional improvements of 9.1 ± 1.8 (range 3-14) to 47.3 ± 1.5 (range 45-49) (p < 0.001) for pain, 49.7 ± 9.7 (range 35-70) to 97.1 ± 4.1 (range 90-100) (p < 0.001) for function, and 105.0 ± 4.4° (equivalent to ∼100-115°) to 125.5 ± 5.3° (∼110-135°) (p < 0.001) for a range of motion (ROM). No patients required reoperations or revisions. Two patients were readmitted within 60 days due to severe knee swelling.

CONCLUSION

The lateral UKA protocol was reproducible and the patients had a good postoperative outcomes. Yet, large-scale, multi-center, prospective studies are needed to further confirm our findings.

The compartmental approach to revision of partial knee arthroplasty results in nearer-normal gait and improved patient reported outcomes compared to total knee arthroplasty

PURPOSE

This study investigated the gait and patient reported outcome measures of subjects converted from a partial knee arthroplasty to combined partial knee arthroplasty, using a compartmental approach. Healthy subjects and primary total knee arthroplasty patients were used as control groups.

METHODS

Twenty-three patients converted from partial to combined partial knee arthroplasty were measured on the instrumented treadmill at top walking speeds, using standard gait metrics. Data were compared to healthy controls (n = 22) and primary posterior cruciate-retaining total knee arthroplasty subjects (n = 23) where surgery were performed for one or two-compartment osteoarthritis. Groups were matched for age, sex and body mass index. At the time of gait analysis, combined partial knee arthroplasty subjects were median 17 months post-revision surgery (range 4-81 months) while the total knee arthroplasty group was median 16 months post-surgery (range 6-150 months). Oxford Knee Scores and EuroQol-5D 5L scores were recorded at the time of treadmill assessment, and results analysed by question and domain.

RESULTS

Subjects revised from partial to combined partial knee arthroplasty walked 16% faster than total knee arthroplasty (mean top walking speed 6.4 ± 0.8 km/h, vs. 5.5 ± 0.7 km/h p = 0.003), demonstrating nearer-normal weight-acceptance rate (p < 0.001), maximum weight-acceptance force (p < 0.006), mid-stance force (p < 0.03), contact time (p < 0.02), double support time (p < 0.009), step length (p = 0.003) and stride length (p = 0.051) compared to primary total knee arthroplasty. Combined partial knee arthroplasty subjects had a median Oxford Knee Score of 43 (interquartile range 39-47) vs. 38 (interquartile range 32-41, p < 0.02) and reported a median EQ-5D 0.94 (interquartile range 0.87-1.0) vs. 0.84 (interquartile range 0.80-0.89, p = 0.006).

CONCLUSION

This study finds that a compartmental approach to native compartment degeneration following partial knee arthroplasty results in nearer-normal gait and improved patient satisfaction compared to total knee arthroplasty.

LEVEL OF EVIDENCE

III.

Comparison of Functional Outcome of Total and Unicompartmental Knee Arthroplasty Using Computer-Assisted Patient-Specific Templating

Background

Knee arthroplasty surgeries are in ever-increasing demand. With unicompartmental knee arthroplasty (UKA), patients may benefit from a higher range of flexion and a better Knee Society Score (KSS).

Aim

In this study, we compared the short-term clinical outcomes of total knee arthroplasty (TKA) and UKA using the patient-specific templating (PST) technique.

Methods

Two groups of 20 knees each were divided into UKA and TKA groups depending on the Oxford criteria of UKA. Only patients with medial compartmental osteoarthritis were included. KSS, functional knee score (FKS), and ROF were assessed preoperatively and at 6 months postoperatively.

Results

The TKA group has shown a significant improvement compared to the UKA group in KSS (MD = 39.35 vs. 31.2, respectively, p=0.003). Both TKA and UKA have shown no significant difference concerning both the FKS (MD = 32 and 31.75, respectively, p=0.926) and ROF (MD = 10.25 and 7.25, respectively, p=0.072). Discussion. The higher improvement of KSS in the TKA group can be attributed to the fact that patients in the TKA had significantly worse KSS preoperatively. Also, the small improvement in ROF in the UKA group might be related to their wider preoperative ROF.

Conclusion

Preoperatively, the TKA group had lower KSS and ROF compared to UKA. The improvement of KSS from preoperative to postoperative was more significant in TKA. However, the TKA group has shown less range of flexion postoperatively.

The effect of tibial and femoral component coronal alignment on clinical outcomes and survivorship in unicompartmental knee arthroplasty

AIMS

This study aimed to identify the tibial component and femoral component coronal angles (TCCAs and FCCAs), which concomitantly are associated with the best outcomes and survivorship in a cohort of fixed-bearing, cemented, medial unicompartmental knee arthroplasties (UKAs). We also investigated the potential two-way interactions between the TCCA and FCCA.

METHODS

Prospectively collected registry data involving 264 UKAs from a single institution were analyzed. The TCCAs and FCCAs were measured on postoperative radiographs and absolute angles were analyzed. Clinical assessment at six months, two years, and ten years was undertaken using the Knee Society Knee score (KSKS) and Knee Society Function score (KSFS), the Oxford Knee Score (OKS), the 36-Item Short-Form Health Survey questionnaire (SF-36), and range of motion (ROM). Fulfilment of expectations and satisfaction was also recorded. Implant survivorship was reviewed at a mean follow-up of 14 years (12 to 16). Multivariate regression models included covariates, TCCA, FCCA, and two-way interactions between them. Partial residual graphs were generated to identify angles associated with the best outcomes. Kaplan-Meier analysis was used to compare implant survivorship between groups.

RESULTS

Significant two-way interaction effects between TCCA and FCCA were identified. Adjusted for each other and their interaction, a TCCA of between 2° and 4° and a FCCA of between 0° and 2° were found to be associated with the greatest improvements in knee scores and the probability of fulfilling expectations and satisfaction at ten years. Patients in the optimal group whose TCCA and FCCA were between 2° and 4°, and 0° and 2°, respectively, had a significant survival benefit at 15 years compared with the non-optimal group (optimal: survival = 100% vs non-optimal: survival = 92%, 95% confidence interval (CI) 88% to 96%).

CONCLUSION

Significant two-way interactions between the TCCA and FCCA demonstrate the importance of evaluating the alignment of the components concomitantly in future studies. By doing so, we found that patients who concomitantly had both a TCCA of between 2° and 4° and a FCCA of between 0° and 2° had the best patient-reported outcome measures at ten years and better survivorship at 15 years. Cite this article: Bone Joint J 2021;103-B(2):338-346.

The extensor efficiency of unicompartmental, bicompartmental, and total knee arthroplasty

Aims

Unicompartmental knee arthroplasty (UKA) and bicompartmental knee arthroplasty (BCA) have been associated with improved functional outcomes compared to total knee arthroplasty (TKA) in suitable patients, although the reason is poorly understood. The aim of this study was to measure how the different arthroplasties affect knee extensor function.

Methods

Extensor function was measured for 16 cadaveric knees and then retested following the different arthroplasties. Eight knees underwent medial UKA then BCA, then posterior-cruciate retaining TKA, and eight underwent the lateral equivalents then TKA. Extensor efficiency was calculated for ranges of knee flexion associated with common activities of daily living. Data were analyzed with repeated measures analysis of variance (α = 0.05).

Results

Compared to native, there were no reductions in either extension moment or efficiency following UKA. Conversion to BCA resulted in a small decrease in extension moment between 70° and 90° flexion (p < 0.05), but when examined in the context of daily activity ranges of flexion, extensor efficiency was largely unaffected. Following TKA, large decreases in extension moment were measured at low knee flexion angles (p < 0.05), resulting in 12% to 43% reductions in extensor efficiency for the daily activity ranges.

Conclusion

This cadaveric study found that TKA resulted in inferior extensor function compared to UKA and BCA. This may, in part, help explain the reported differences in function and satisfaction differences between partial and total knee arthroplasty.

Cite this article: Bone Joint Res 2021;10(1):1–9.

Unicompartmental knee arthroplasty has higher revisions than total knee arthroplasty at long term follow-up: a registry study on 6453 prostheses

PURPOSE

The purpose of this study is to analyse long-term unicompartmental knee arthroplasty (UKA) focusing on survivorship, causes of failure and revision strategy.

METHODS

This study is a retrospective analysis of data from a regional arthroplasty registry for cases performed between 2000 and 2017. A total of 6453 UKAs were identified and the following information was analysed: demographic data, diagnosis leading to primary implant, survivorship, complication rate, causes of failure, revision strategies. UKA registry data were compared with total knee arthroplasty (TKA) registry data of 54,012 prostheses, which were implanted in the same time period.

RESULTS

6453 UKAs were included in the study: the vast majority of them (84.4%) were implanted due to primary osteoarthritis followed by deformity (7.1%) and necrosis of the condyle (5.1%). When compared to TKA, UKA showed lower perioperative complication rate (0.3% compared to 0.6%) but higher revision rate (18.2% at 15 years, compared to 6.2% for TKA). No correlation was found between diagnosis leading to primary implant and prosthesis survival. The most frequent cause of failure was total aseptic loosening (37.4%), followed by pain without loosening (19.8%). Of the 620 UKAs requiring revision, 485 were revised with a TKA and 61 of them required a re-revision; on the other hand, of the 35 cases where another UKA was implanted, 16 required a re-revision.

CONCLUSION

UKA is associated with fewer perioperative complications but higher revision rates when compared to TKA. Its survivorship is not affected by the diagnosis leading to primary implant. Revision surgery of a failed UKA should be performed implanting a TKA, which is associated with a lower re-revision rate when compared to another UKA.

LEVEL OF EVIDENCE

Level 3, therapeutic study.

Robotic arm-assisted bi-unicompartmental knee arthroplasty maintains natural knee joint anatomy compared with total knee arthroplasty: a prospective randomized controlled trial

AIMS

The aim of this study was to compare robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) in order to determine the changes in the anatomy of the knee and alignment of the lower limb following surgery.

METHODS

An analysis of 38 patients who underwent TKA and 32 who underwent bi-UKA was performed as a secondary study from a prospective, single-centre, randomized controlled trial. CT imaging was used to measure coronal, sagittal, and axial alignment of the knee preoperatively and at three months postoperatively to determine changes in anatomy that had occurred as a result of the surgery. The hip-knee-ankle angle (HKAA) was also measured to identify any differences between the two groups.

RESULTS

The pre- to postoperative changes in joint anatomy were significantly less in patients undergoing bi-UKA in all three planes in both the femur and tibia, except for femoral sagittal component orientation in which there was no difference. Overall, for the six parameters of alignment (three femoral and three tibial), 47% of bi-UKAs and 24% TKAs had a change of < 2° (p = 0.045). The change in HKAA towards neutral in varus and valgus knees was significantly less in patients undergoing bi-UKA compared with those undergoing TKA (p < 0.001). Alignment was neutral in those undergoing TKA (mean 179.5° (SD 3.2°)) while those undergoing bi-UKA had mild residual varus or valgus alignment (mean 177.8° (SD 3.4°)) (p < 0.001).

CONCLUSION

Robotic-assisted, cruciate-sparing bi-UKA maintains the natural anatomy of the knee in the coronal, sagittal, and axial planes better, and may therefore preserve normal joint kinematics, compared with a mechanically aligned TKA. This includes preservation of coronal joint line obliquity. HKAA alignment was corrected towards neutral significantly less in patients undergoing bi-UKA, which may represent restoration of the pre-disease constitutional alignment (p < 0.001). Cite this article: Bone Joint J 2020;102-B(11):1511-1518.

Lower limb kinematics of unicompartmental knee arthroplasty individuals during stair ascent

Objective

Purpose of the study was to compare lower-limb kinematics and interlimb asymmetry during stair ascent in individuals post-medial or lateral unicompartmental knee arthroplasty (UKA).

Methods

60 patients (20 medial; 10 lateral) post-UKA and 30 matched healthy controls performed stair ascent. Spatio-temporal, lower-limb kinematics and interlimb asymmetries during stair ascent were compared.

Results

Medial-UKA group displayed 5° less knee extension of the UKA limb than controls (p = 0.005) and 2° less than the contralateral limb during stance phase. No interlimb asymmetries were found for lateral-UKA.

Conclusion

Patients post-UKA demonstrate satisfactory lower-limb kinematics and minimal interlimb asymmetry during stair ascent compared to healthy individuals.