Indications for lateral unicompartmental knee arthroplasty - A systematic review

Background: While evidence-based indications are established for medial UKA, the optimal indications for lateral UKA have not received as much attention. There exists significant anatomical, osteoarthritis phenotype, kinematic, and surgical technique differences between medial and lateral UKA. The indications for the two procedures may therefore not be identical. Hence, this review aims to access the indications and contraindications in published cohort studies on lateral UKA, to assess if consensus exists.

Methods: In May 2024, a systematic review was carried out following the Preferred Reporting Item for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Cohort studies on lateral UKA with a clear report of indications were included. Data on indications and contraindications were extracted to evaluate consensus. Furthermore, outcomes related to expanding or testing indications for lateral UKA were obtained.

Results: 38 studies were included. Lateral UKA was mostly performed for primary lateral osteoarthritis. The most reported indications were moderate to severe lateral osteoarthritis, with full-thickness cartilage in the medial compartment, intact ligaments, a correctable valgus deformity, and a flexion contracture < 10-15 degrees. The most reported contraindications were inflammatory arthritis and severe patellofemoral involvement. Eight studies investigated different indications on outcomes after lateral UKA; suggesting better outcomes for primary lateral osteoarthritis, no significant impact from the state of the patellofemoral joint, and conflicting results regarding age and weight.

Conclusion: While the literature suggests that some agreement does exist regarding indications for lateral UKA, a strong consensus was not found, indicating that well-defined and consensus-based indications for lateral UKA do not yet exist.