Robotic assisted fixed bearing medial UKA: can soft tissue balancing and restoration of alignment modify PFJ kinematics in the presence of chondral wear.

Abstract

The impact of patellofemoral chondral lesions on the outcomes following Unicondylar Knee Arthroplasty (UKA) remains an enigmatic topic among arthroplasty surgeons. We aim to compare the clinical outcomes of medial UKAs, with varying grades of patellofemoral wear and ACL quality, to help in decision making for suitability of UKA. A total of 195 robotic-assisted fixed-bearing UKAs performed between 2018 and 2024 were identified from our institutional database. Chondral lesions in the trochlea, both medial and lateral facets of the patella, and the lateral compartment were classified according to the International Cartilage Repair Society classification as low grade (0-2) and high grade (3/4). The Oxford Knee Score and Modified Kujala Score, a score specific for patellofemoral pain, were used for functional assessment. Intraclass correlation was used to compare the chondral damage and outcomes. The mean follow-up was 44 ± 10 months (11-56). There was no difference between the OKS and MKS compared across the ICRS grades for trochlea, medial/lateral patellar facet, or lateral compartment damage (p > 0.05). There was no significant difference in the varying grades of ACL damage (p > 0.05). No revisions are seen until last follow-up. Intactness of 3 'Ls' - 'L'ateral compartment cartilage including lateral meniscus, adequately tracking 'L'ateral facet of the patella and functional stability of the AC'L' are the most important caveats for determining the suitability of UKA. Restoration of the joint line, pre-arthritic soft tissue balance and alignment are crucial. The use of imageless robotics technology has helped produce consistent results with the optimisation of the surgical workflow.