Functional outcome after bicompartmental knee replacement for medial and patellofemoral osteoarthritis

Total knee arthroplasty (TKA) is used for tricompartmental knee osteoarthritis, while unicompartmental knee arthroplasty (UKA) is preferred for unicompartmental knee osteoarthritis. Bicompartmental knee arthroplasty (BKA) aims to address 2 knee compartments by combining 2 UKA's or 1 UKA with a patellofemoral replacement. This study examines the clinical outcomes of BKA, focusing on pain alleviation and knee function. The aim of this study is to report the functional outcome of BKA and see if this aligns with BKA outcomes from literature in terms of patient reported outcome measurements (PROMs) and range of motion (ROM) after a 2-year follow-up. Additionally, radiographic alignment, implant survivorship, adverse events and length of stay are secondary outcomes.

This is a cohort study of 21 patients who underwent BKA for medial and patellofemoral osteoarthritis. The patients had follow-up for at least 2 years postoperatively. PROMs were assessed using the Knee injury and Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS), Oxford Knee Score, Western Ontario and McMaster University Osteoarthritis index (WOMAC) and the Visual Analogue Scale (VAS). ROM was measured using a goniometer. Pre- and postoperative radiographic coronal alignment was measured using standard full leg radiographs. Patient demographics, implant survivorship, length of stay and adverse events were recorded.

Twenty-one patients (23 knees) were included, with a mean follow-up of 41 months (standard deviation [SD] 12 months; range 24-59 months). Patient-reported outcome measures (PROMs) demonstrated significant improvements, with 80% achieving good to excellent OKS and KSS scores. KOOS scores were similar to scores found in literature. The WOMAC score was higher in our results compared to other authors. Which indicates worse outcome. The mean preoperative hip-knee-ankle angle (HKAA) was 2.4 degrees varus (SD 1.9 degrees; range 1.2 degrees valgus - 6.1 degrees varus), while the mean postoperative HKAA was 0.3 degrees valgus (SD 2.8 degrees; range 4.6 degrees valgus - 5.6 degrees varus) (p < 0.001). Postoperative range of motion averaged 117 degrees (SD 10 degrees; range 98-132).

BKA shows promise in alleviating pain and improving knee function in patients with medial and patellofemoral osteoarthritis. Challenges include the risk of revision and technical difficulties during surgery. Comparative studies suggest similar outcomes between BKA and TKA, with potential advantages for younger, more active patients. Further research, particularly randomized trials with larger cohorts, is necessary to elucidate the long-term benefits and drawbacks of BKA compared to other knee arthroplasty options.