Mild Lateral Femoral Condyle Cartilage Damage Does Not Affect the Outcomes of Medial Unicompartmental Knee Arthroplasty

BACKGROUND: The aim of this study was to ascertain whether mild cartilage damage of the lateral condyle of the femur influences the mid-term clinical outcomes of medial unicompartmental knee arthroplasty (mUKA) and exacerbates the progression of osteoarthritis in the lateral compartment. METHODS: Patients with normal cartilage or mild cartilage damage of the lateral femoral condyle (Outerbridge grade, ≤II) who underwent mUKA between March 2016 and December 2020 were retrospectively divided into 4 groups: a normal cartilage group and a cartilage damage group that was subdivided on the basis of the damage location (weight-bearing area, posterior weight-bearing area, and medial side of the lateral condyle). Patients with postoperative overcorrection of limb alignment or preoperative lateral meniscal extrusion were excluded. Outcomes that were compared among the groups included the hip-knee-ankle angle (HKA), lateral compartment Kellgren-Lawrence (K-L) grade, Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Kujala score, patient satisfaction, and complications. RESULTS: The study included 203 knees in 177 patients (136 female patients; 177 East Asian; mean age, 68.3 ± 7.1 years) with a mean follow-up of 70.8 months (range, 48 to 106 months). The postoperative OKS, FJS, and Kujala score showed no significant differences among the groups. Mid-term full-length standing radiographs of the lower limbs were obtained for 99 of the 203 knees, with a mean follow-up of 54.1 months (range, 49 to 104 months). Of the 99 knees, 26 (26.3%) showed an increase of 1 K-L grade in the lateral compartment and 73 (73.7%) remained unchanged. Three knees (1.5%) from the normal group experienced complications, including 1 periprosthetic fracture, 1 bearing dislocation, and 1 bearing rotation, but none required conversion to TKA. CONCLUSIONS: In patients in whom postoperative alignment is not overcorrected and preoperative lateral meniscal function is intact, mild cartilage damage (Outerbridge grade I or II) of the lateral femoral condyle does not impact the mid-term clinical outcomes of mUKA and does not exacerbate the progression of osteoarthritis in the lateral compartment. LEVEL OF EVIDENCE: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.