Patient sex and race are associated with differences in coronal plane alignment classification in native arthritic knees

Purpose: The purpose of this study was to evaluate associations between demographics and Coronal Plane Alignment of the Knee (CPAK) classification in pre-surgical TKA patients. Methods: This is a retrospective study of 1167 patients with knee osteoarthritis who underwent TKA. CPAK categories I-IX were determined by arithmetic mechanical hip-knee-ankle angle and joint line obliquity measurements from pre-operative bone length radiographs. Patient age, sex, body mass index (BMI) and race were collected. Chi-square test of independence and adjusted Pearson’s residuals evaluated associations between CPAK classification and demographics. Results: There was a significant association between CPAK phenotypes I-IX and patient sex (X 2 = 5.8, p < 0.01). A positive association was found between both men and CPAK phenotype I, and women and CPAK phenotype VII. A positive association was found between African American patients and CPAK phenotype III and a negative association was found between African American patients and CPAK phenotype I (X 2 =14.8, p-value = 0.01). There was no association between age and BMI with CPAK phenotypes (n.s.). Conclusion: These results indicate that there are unidentified sex and race differences that exist in the CPAK classification of native arthritic knees. Patient characteristics play a significant role in determining patient knee phenotypes. Further research should investigate whether these characteristics warrant inclusion in pre-operative preparations, aiming to enhance the personalization of arthroplasty procedures.