Incidence and severity of radiological lateral osteoarthritis 15 years following medial unicompartmental knee arthroplasty

Journal article

Aims: To assess the incidence of radiological lateral osteoarthritis (OA) at 15 years after medial unicompartmental knee arthroplasty (UKA) and assess the relationship of lateral OA with symptoms and patient characteristics.

Methods: Cemented Phase 3 medial Oxford UKA implanted by two surgeons since 1998 for the recommended indications were prospectively followed. A 15-year cumulative revision rate for lateral OA of 5% for this series was previously reported. A total of 163 unrevised knees with 15-year (SD 1) anterior-posterior knee radiographs were studied. Lateral joint space width (JSW_L) was measured and severity of lateral OA was classified as: nil/mild, moderate, and severe. Preoperative and 15-year Oxford Knee Scores (OKS) and American Knee Society Scores were determined. The effect of age, sex, BMI, and intraoperative findings was analyzed. Statistical analysis included one-way analysis of variance and Kruskal-Wallis H test, with significance set at 5%.

Results: The mean age was 80.6 years (SD 8.3), with 84 females and 79 males. The mean JSW_L was 5.6 mm (SD 1.4), and was not significantly related to age, sex, or intraoperative findings. Those with BMI > 40 kg/m² had a smaller JSW_L than those with a ‘normal’ BMI (p = 0.039). The incidence of severe and moderate lateral OA were both 4.9%. Overall, 2/142 (1.4%) of those with nil/mild lateral OA, 1/8 (13%) with moderate, and 2/8 (25%) with severe subsequently had a revision. Those with severe (mean OKS 35.6 (SD 9.3)) and moderate OA (mean OKS 35.8 (SD 10.5)) tended to have worse outcome scores than those with nil/mild (mean OKS 39.5 (SD 9.2)) but the difference was only significant for OKS-Function (p = 0.044).

Conclusion: This study showed that the rate of having severe or moderate radiological lateral OA at 15 years after medial UKA was low (both 4.9%). Although patients with severe or moderate lateral OA had a lower OKS than those with nil/mild OA, their mean scores (OKS 36) would be classified as good.

Authors: Searle, HKC; Rahman, A; Desai, AP; Mellon, SJ; Murray, DW

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: British Editorial Society of Bone and Joint Surgery
• Journal: Bone and Joint Open
• Volume: 4
• Issue: 3
• Pages: 210-218
• Publication date: 2023-03-28
• Acceptance date: 2023-03-01
• DOI: 10.1302/2633-1462.43.bjo-2022-0153.r1
• EISSN: 2633-1462
• Pmid: 37051833
• Language: English
• Keywords: osteoarthritis (OA); medial Oxford UKA; lateral osteoarthritis; BMI; medial unicompartmental knee arthroplasty; radiography; American knee society scores; FFR; Oxford knee scores; knees; unicompartmental replacement; joint space width (JSW); variance