Lateral unicompartmental knee arthroplasty: sticking to the indications and applying a meticulous technique in order to guarantee excellent long-term outcomes

Background: Lateral unicompartmental knee arthroplasty (UKA) is performed significantly less frequently than medial UKA, often due to the lower prevalence of valgus deformities and historical concerns regarding implant survival and specific complications such as bearing dislocation. Despite these concerns, recent data suggest functional outcomes and long-term survival rates comparable to total knee arthroplasty (TKA) when treating isolated lateral compartment disease.

Objective: This article provides a technical update on lateral UKA, detailing patient selection criteria, surgical methodology, and long-term clinical outcomes based on a multicenter retrospective study.

Key Points: Indications include isolated lateral osteoarthritis or necrosis with reducible deformity and an intact anterior cruciate ligament. Surgical technique emphasizes a lateral parapatellar approach without ligamentous release to avoid overcorrection. A 1–2 mm laxity safety margin is recommended. Analysis of 268 lateral UKA procedures with a mean 9.1-year follow-up demonstrated a 10-year survival rate of 85.4% and a 20-year rate of 79.4%. The primary cause of failure was disease progression in other compartments (n=26). No statistically significant differences in survival were observed between resurfacing and cutting implants or between cemented and cementless fixation, although cemented implants showed superior postoperative IKS scores.

Conclusion: Lateral UKA is a reliable surgical option for isolated lateral compartment disease. Success depends on strict adherence to indications, preservation of the ligamentous envelope, and precise component positioning to accommodate the specific anatomy and biomechanics of the lateral tibiofemoral joint.