Mid-Term Evaluation of the Unicompartmental Knee Arthroplasty in Patients with BMI of 40 or Greater

Unicompartmental knee replacement: controversies and technical considerations

BACKGROUND

Unicompartmental knee replacement (UKR) is one of the effective interventions for the treatment of symptomatic knee osteoarthritis. Moreover, it has multiple advantages over total knee arthroplasty (TKA), including reduced intraoperative blood loss, decreased risk of transfusion, and faster recovery. This study aimed to discuss critical technical considerations regarding UKR and some of the controversies and updates.

METHODS

We conducted a review to provide an overview of the controversies and technical considerations about UKR in several aspects. Only peer-reviewed articles were included, up to December 2023 using PubMed, Google Scholar, ERIC, and Cochrane database for systematic reviews databases.

RESULT

UKR is associated with superior patient-reported clinical and functional outcomes, as well as shorter hospital stays, fewer postoperative complications, and revealed favorable outcomes in patients' return to sport. The choice between mobile- and fixed-bearing prostheses depends, in part, on the surgeon's preference. The mobile-bearing UKR is a less constrained prosthesis and can potentially result in less wear, but it is more technically demanding. While no significant difference between mobile-bearing versus fixed-bearing prostheses, cementless is superior to cemented design. Furthermore, UKR can be a good alternative for high tibial osteotomy (HTO) and still can be considered after a failed HTO. Lastly, recent reviews have shown a revision rate comparable to that of TKA. This is probably influenced by Improved comprehension of the best indications, patient selection criteria, as well as of the design, materials, and technological advances.

CONCLUSION

UKR treatment for unicompartmental knee osteoarthritis is secure and effective. Based on clinical and functional outcomes, decreased morbidity and mortality, and cost-effectiveness, long-term studies suggest that UKR is superior to TKA. Further investigation in this area is warranted.

Early Outcome Trends of Unicompartmental Knee Arthroplasty in Patients With Morbid Obesity: A Potential for Outpatient Surgery

BACKGROUND

Elevated body mass index (BMI) was previously considered a contraindication to unicompartmental knee arthroplasty (UKA). This study sought to determine if outcomes following UKA in patients with elevated BMI have improved over the years. We hypothesized that operative times and length of stay (LOS) following UKA would significantly decrease, while discharge to home rates would increase across all BMI cohorts, especially those with a BMI > 40.

METHODS

Using the National Surgical Quality Improvement Program registry, surgical cases categorized using the Current Procedural Terminology code 27446 for UKA with a recorded height and weight were included. Three BMI cohorts were created: BMI I (BMI < 30), BMI II (30 ≤ BMI ≤ 40), and BMI III (BMI > 40). Each BMI group was subclassified temporally by year of operation: Years A (2006-2009), Years B (2010-2014), and Years C (2015-2019).

RESULTS

A total of 14,114 patients were included. For BMI III, both operative time (P < .001) and LOS (P < .001) significantly decreased over the Years cohorts. Discharge home rates increased from 88.3% to 94.4% in BMI III (P = .001). All BMI cohorts saw similar changes in discharge patterns, 30-day readmissions, and reoperations within 30 days in recent years.

CONCLUSION

This study found that operative times and LOS have decreased significantly in patients with morbid obesity over the past 14 years, while more patients are being discharged home without being readmitted or reoperated on in the first month. As surgeons continue to improve their operative and reconstructive techniques, this study suggests that patients with elevated BMI should be considered candidates to undergo UKA procedures in ambulatory surgery centers or in hospitals with a rapid recovery unit.

Short-term outcomes of Oxford unicompartmental knee arthroplasty with coronal subluxation of the knee: a retrospective case–control study

Background

The goal of this study was to assess short-term outcomes in single compartment osteoarthritis patients associated with the coronal tibiofemoral subluxation (CTFS) of the knee joint after Oxford unicompartmental knee arthroplasty (OUKA), and to establish the potential impact of the degree of CTFS on operative outcomes.

Methods

Data pertaining to 183 patients with medial compartment osteoarthritis that underwent OUKA treatment between February 2016 and June 2019 were retrospectively analyzed. The presence and degree of severity of CTFS were assessed using preoperative weight-bearing anteroposterior X-ray images of the knee. Patients were stratified into three subgroups based upon the observed degree of subluxation: a normal group, a mild subluxation group (CTFS < 0.5 cm), and a severe subluxation group (CTFS ≥ 0.5 cm). Anterior and posterior X-ray examination of the knee was conducted at the time of most recent follow-up for each patient to assess the degree of CTFS correction following OUKA. Clinical function was assessed using Oxford knee score (OKS) and Hospital for Special Surgery score (HSS) values, while pain was rated using visual-analog scale (VAS) scores. The mechanical femoral tibial angle (mFTA), range of motion (ROM), and complication rates in these three groups were additionally compared.

Results

The average follow-up duration for patients in this study was 24.1 months (range: 17–32 months). There were no significant differences in patient age, sex, body mass index (BMI), follow-up duration, mFTA, ROM, OKS, HSS, or VAS scores among these three groups (P > 0.05). After surgery, OKS and HSS scores declined significantly, but no differences in these scores were observed among groups (P > 0.05). Of these patients, 135 (73.8%) were satisfied with the operation, of whom 80 (43.7%) were very satisfied. There were no significant differences in ROM or VAS scores among groups (P > 0.05). The degree of CTFS for patients in the mild and severe subluxation groups was significantly improved following OUKA relative to preoperative values such that the degree of postoperative CTFS did not differ significantly among these groups (P > 0.05). Postoperative mFTA was also significantly improved in these three patient subgroups (P < 0.05). No patients experienced operative complications over the follow-up period.

Conclusions

OUKA can successfully improve clinical symptoms in patients with single compartmental osteoarthritis. Moreover, OUKA can effectively correct CTFS of the knee in these patients, and the degree of preoperative CTFS has no impact on surgical efficacy.

Level of evidence

III.

Unicompartmental Knee Replacement in Obese Patients: A Systematic Review and Meta-Analysis

Thanks to modern surgical techniques and implants, traditional exclusion criteria for unicompartmental knee arthroplasty (UKA) are no longer considered contraindications. The aim of this study is to clarify the impact of obesity on functional outcomes and revision rates of UKA. We performed a comprehensive systematic review using PubMed–Medline, Google Scholar and Cochrane Central. Then, we extracted data related to body mass index (BMI), age and follow-up, functional outcome scores and rate of revisions (all-cause, aseptic and septic). Patients were stratified according to BMI into two groups: non-obese (BMI < 30) and obese (BMI ≥ 30). We identified 22 eligible studies, of which 13 were included in the meta-analysis. Patients with a BMI > 30 had a significantly higher likelihood for revision (p = 0.02), while the risk of septic revision was similar (p = 0.79). The clinical outcome measures showed a significant difference in favor of patients with a BMI < 30 (p < 0.0001). The improvements in Oxford Knee Score and Knee Society Score were significant in both obese and non-obese patients, although the latter showed inferior results. The results of this systematic review and meta-analysis show that BMI is not a contraindication to UKA. However, obese patients have a higher risk for aseptic failure and lower improvement in clinical scores compared to non-obese patients.

Obesity does not adversely impact the outcome of unicompartmental knee arthroplasty for osteoarthritis: a meta-analysis of 80,798 subjects

BACKGROUND

Patients with end-stage single compartment osteoarthritis benefit from the less invasive unicompartmental knee arthroplasty (UKA). With increasing financial restraints, some healthcare services have set specific BMI cut-offs when determining patient eligibility for knee arthroplasty due to perceived obesity-related complications. The aim of this systematic review is to determine the effect obesity has on outcomes following UKA, and thus elucidate whether obesity should be a contraindication for UKA.

METHODS

A PRISMA systematic review was conducted using five databases (MEDLINE, EMBASE, Cochrane, PubMed and Web of Science) to identify all clinical studies that examined the effect of obesity on outcomes following UKA. Quantitative meta-analysis was carried out using RevMan 5.3 software. Quality assessment was carried out using the Critical Appraisal Skills Programme (CASP) checklist.

RESULTS

Thirty studies, including a total of 80 798 patients were analysed. The mean follow- up duration was 5.42 years. Subgroup meta-analyses showed no statistically significant difference following UKA between patients cohorts with and without obesity in overall complication rates (95% CI, P = 0.52), infection rates (95% CI, P = 0.81), and revision surgeries (95% CI, P = 0.06). When further analysing complications, no differences were identified in minor (95% CI, P = 0.23) and major complications (95% CI, P = 0.68), or venous thromboembolism rates (95% CI, P = 0.06). When further analysing revision surgeries, no differences were identified for revisions specifically for infection (95% CI, P = 0.71) or aseptic loosening (95% CI, P = 0.75).

CONCLUSIONS

This meta-analysis shows that obesity does not result in poorer post-operative outcomes following UKA and should not be considered a contraindication for UKA. Future studies, including long-term follow-up RCTs and registry-level analyses, should examine factors associated with obesity and consider stratifying obesity to better delineate any potential differences in outcomes.