The influence of retaining osteophyte on the coronal alignment and joint line height following medial unicompartmental knee arthroplasty

BACKGROUND: The retention of osteophytes may influence the postoperative hip-knee-ankle (HKA) angle and joint line height (JLH) following unicompartmental knee arthroplasty (UKA); however, the specific impact remains poorly characterized. This study aimed to evaluate the effect of retaining the medial femoral condylar osteophyte on these parameters after medial UKA. METHODS: This sequential historical cohort study included patients who underwent medial UKA between January 1, 2025, and December 31, 2025. The patient cohort comprised an osteophyte removal group and an osteophyte retention group. Preoperative HKA, medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), osteophyte width, postoperative HKA, and the change in JLH were measured. The arithmetic HKA (aHKA) and the change in coronal alignment (ΔHKA) were calculated as follows: aHKA = MPTA - LDFA + 180°, and ΔHKA = aHKA - postoperative HKA. The postoperative outcomes of interest were the change in HKA and the change in JLH. Spearman's rank correlation coefficient was used to assess the relationships between osteophyte width and both ΔHKA and the change in JLH. RESULTS: This study included 141 patients (141 knees). The osteophyte removal group comprised 80 patients (mean age 65.5 ± 6.9 years), and the osteophyte retention group comprised 61 patients (mean age 65.9 ± 6.5 years). The postoperative HKA was significantly greater (176.11° ± 3.29° vs. 174.97° ± 2.73°, p = 0.032) and the ΔHKA was significantly smaller (0.57° ± 2.52° vs. 1.50° ± 1.99°, p = 0.041) in the removal group. Correlation analysis revealed a significant positive correlation between ΔHKA and osteophyte width (r = 0.527, p < 0.001). Radiographic assessment of JLH showed a distal migration of 2.67 ± 1.37 mm in the osteophyte removal group, compared with 1.79 ± 1.21 mm in the retention group (p = 0.001). Furthermore, the change in JLH demonstrated a significant negative correlation with osteophyte width (r = -0.484, p < 0.001). CONCLUSIONS: Retention of the medial femoral condylar osteophyte appears to be associated with a reduction in the postoperative HKA angle and elevation of the joint line; however, the decision to retain or excise the osteophyte warrants further research.