Preoperative coronal plane alignment of the knee phenotype does not predict patient-reported outcomes after medial opening-wedge high tibial osteotomy.

Abstract

Phenotype-based classification systems have been proposed to characterise coronal alignment and joint-line orientation and to support individualised correction strategies. Although developed primarily for arthroplasty, they are increasingly evaluated in osteotomy populations. This study assessed whether preoperative coronal plane alignment of the knee (CPAK) phenotype predicts patient-reported outcome measures (PROMs) after medial opening-wedge high tibial osteotomy (MOWHTO). This retrospective cohort study included 130 knees in 111 patients undergoing valgus-producing MOWHTO for medial compartment osteoarthritis. Full-length standing radiographs were independently assessed by two observers, and knees were classified preoperatively and postoperatively using both hip-knee-ankle angle (HKA) based and arithmetic CPAK methods. Knee injury and Osteoarthritis Outcome Score (KOOS) subscales, KOOS-12 Total, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Total, and Tegner activity score were collected preoperatively, at 1 year, 2 years, and final follow-up. Associations between preoperative CPAK phenotype and postoperative PROMs were evaluated using non-parametric group comparisons and multivariable regression. Mean age was 48.1 ± 7.0 years, and median follow-up was 28.6 months. Preoperative CPAK phenotype was associated with preoperative knee function but not with postoperative PROMs using either the HKA-based or arithmetic classification method. HKA-based Type 2 knees demonstrated higher KOOS Sports and Tegner scores at selected follow-up points; however, these differences were not statistically significant after correction for multiple comparisons and multivariable adjustment. No statistically significant differences in PROM improvement were observed across preoperative CPAK phenotypes with either method. Preoperative CPAK phenotype was not associated with PROMs after MOWHTO. Any observed differences were not statistically significant after adjustment, indicating limited prognostic value. These findings show that alignment-based phenotyping alone is insufficient to guide decision-making in MOWHTO, and that a more comprehensive assessment is required. Level III.