Impact of distal femoral morphology on short-term outcomes following high tibial osteotomy (HTO) in varus knees

Despite the availability of various osteotomies for varus knee osteoarthritis, including proximal tibial, distal femoral, and fibular osteotomies, HTO is the most prevalent in clinical practice. The primary focus of this study is to investigate how distal femoral morphology influences the outcomes of HTO. Demographic characteristics, radiographic parameters, and functional scores were collected preoperatively and at 2-year follow-up from patients undergoing HTO at our institution between January 2022 and July 2022. Patients were categorized into two cohorts based on the lateral distal femoral angle (LDFA): Group I (LDFA ≤ 89°) and Group II (LDFA > 89°). Each cohort was further stratified into three subgroups according to postoperative hip-knee-ankle angle (post-HKA): Subgroup A (HKA = 180° ± 0.5°), Subgroup B (HKA = 181° ± 0.5°), and Subgroup C (HKA = 182° ± 0.5°). Radiographic and functional outcomes were compared. The study included 191 patients distributed across six subgroups (IA: 33, IB:29, IC:29, IIA:37, IIB:30 and IIC:33). Significant inter-subgroup differences were observed in the change in joint line convergence angle (ΔJLCA) for both Group I (F = 11.876, P = 0.048) and Group II (F = 9.826, P = 0.042). ΔJLCA exhibited a positive correlation with the change in hip-knee-ankle angle (ΔHKA) in both groups (Group I: r = 0.323, P = 0.011; Group II: r = 0.522, P < 0.001). In Group I, postoperative joint line orientation angle (Post-JLOA) showed no significant differences. At 2-year follow-up, subgroup C demonstrated superiority in the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) and Oxford Knee Scores (OKS) compared to subgroup A(WOMAC:P = 0.006; OKS: P = 0.007). Changes in WOMAC and OKS (ΔWOMAC and ΔOKS) correlated positively with ΔHKA and ΔJLCA but showed no correlation with Post-JLOA. In Group II, Post-JLOA differed among the subgroups (F = 9.205, P = 0.035). At 2-year follow-up, Functional outcomes were comparable across subgroups. Both ΔWOMAC and ΔOKS positively correlated with ΔHKA and ΔJLCA but negatively with Post-JLOA. A mechanical axis of 182° optimizes clinical outcomes in patients with normal femoral anatomy, while 180° is preferable for cases with distal femoral varus to minimize joint line obliquity.