Coronal plane alignment influences medial and lateral malleolus bone density in ankle patients with arthritis

Background: The effect of coronal plane deformity in ankle arthritis on the bone mineral density of the medial and lateral malleolus has not been previously studied. Purpose: We aimed to identify whether the coronal plane deformity has an influence on the medial and lateral malleolus bone mineral density in patients. Study Design: Retrospective cohort study. Methods: We performed a retrospective review at our institution from 2013 to 2023 to identify patients with end-stage ankle arthritis with a preoperative computer tomography (CT) scan undergoing either ankle arthroplasty or ankle arthrodesis. Patients were stratified into varus or valgus (tibiotalar angle > 5 degrees) and neutral ankle alignments. Bone mineral density measurements were taken of the medial and lateral malleolus on CT scan and the medial and lateral ratio was obtained and compared to the tibiotalar angle. Results: There was a statistically significant difference between the medial/lateral bone mineral density ratio in valgus vs neutral patients (P = 0.003) as well as between varus vs valgus patients (P < 0.001). There was no significant difference between medial/lateral malleolus bone mineral density ratio in varus vs neutral patients (P = 0.514). Conclusion: Valgus deformity in patients with ankle arthritis influences bone mineral density in the medial and lateral malleolus.