Effect of Coronal Plane Knee Alignment Classification on Clinical Outcomes After High Tibial Osteotomy

Background: Studies on the coronal plane alignment of the knee (CPAK) classification after high tibial osteotomy (HTO) are scarce. Purpose: To (1) clarify the distribution of the CPAK phenotype in patients who underwent HTO and (2) compare the clinical results according to the CPAK phenotypes. Study Design: Case Series; Level of evidence, 4. Methods: Overall, 171 knees of patients with HTO were retrospectively evaluated. The primary outcome was to investigate the serial changes in the CPAK preoperatively and 2 years postoperatively. The secondary outcome was to assess the subcategories of the knee injury and osteoarthritis outcome score (KOOS) and postoperative change of KOOS according to the CPAK. Results: The most common pre- and postoperative CPAK phenotype types were I (62%), II (22.8%), IV (8.8%), VI (36.7%), V (18.9%), and IX (13%). The distribution of preoperative CPAK significantly changed after HTO. KOOS subscales showed no significant differences according to the CPAK phenotypes. Conclusion: The most common pre- and postoperative CPAK phenotypes were I and VI. No significant differences in the KOOS subscales were observed according to CPAK phenotypes following HTO.