Abstract:

Objective

To investigate the relationship between preoperative coronal alignment and postoperative alignment following Oxford unicompartmental knee arthroplasty (UKA), and to explore methods for predicting postoperative alignment.

Methods

This retrospective study enrolled 130 patients (156 knees) who underwent Oxford mobile-bearing UKA for anteromedial knee osteoarthritis at the Second Hospital of Shanxi Medical University between January 2021 and December 2022. Patients with incomplete imaging data or a history of trauma or fractures were excluded. Based on postoperative hip-knee-ankle (HKA) angles, the patients were categorized into three groups: neutral alignment group (-1°≤HKA<3°, n=68), moderate varus group (3°≤HKA≤7°, n=74), and excessive varus group (HKA>7°, n=14). Imaging data of the patients were retrospective analyzed for the intergroup differences in preoperative HKA (pre-HKA), lateral distal femoral angle (LDFA),medial proximal tibial angle (MPTA), and arithmetic HKA (aHKA) using the Kruskal-Wallis H test. Spearman correlation analysis was performed to identify associations between preoperative parameters and postoperative alignment.

Results

Statistically significant differences were observed among the three groups in pre-HKA(H=51.836, P<0.001), MPTA (H=39.764, P<0.001), LDFA (H=31.401, P<0.001), and aHKA (H=81.992,P<0.001). Spearman analysis revealed the strongest correlation between aHKA and postoperative HKA (r=-0.805,P<0.001), with the regression equation: post-HKA=-0.7×aHKA+0.5.

Conclusions

Preoperative coronal alignment significantly influences postoperative alignment in Oxford UKA. aHKA serves as a reliable predictor of postoperative HKA. Caution is warranted when aHKA approaches or exceeds 2.1°(risk of valgus alignment)or falls below -9.3° (risk of excessive postoperative varus deformity).

Key words: Arthroplasty,replacement, Knee, Osteoarthritis