Medial Malleolar Fracture Risk by Supination Adduction After Arthroscopic Transmalleolar Portal Drilling: A Cadaveric Biomechanical Study.

Abstract

The medial transmalleolar portal (mTMP) can be used to access osteochondritis dissecans lesions of the medial talar dome. The purpose of this study was to determine if, for supination adduction injury mechanism, drilling an mTMP increases fracture risk about the medial malleolus when compared to intact ankles, utilizing a cadaveric model. Twenty-four matched ankles were cut midtibia and dissected down to the bone, sparing the tibiotalar joint capsule. The specimens were divided into 2 groups: intact control ankles and ankles with a 6-mm mTMP created by a senior orthopaedic surgeon (portal group). Each specimen was then secured in inversion against a steel baseplate and loaded until failure. Donor demographics, fracture characteristics, and failure loads were compared between groups. Continuous data were analyzed using 2-sample <i>t</i> tests with <i>P</i> = .05 as the cutoff for significance. In total, 24 ankles were used in this study, with 12 in each group. The mean failure loads were 8473 ± 5142 N and 7405 ± 4296 N for the control and portal groups, respectively, with no significant difference (<i>P</i> = .586). Comminuted fracture patterns occurred at similar rates between control (42%) and portal (50%) groups (<i>P</i> = .682). Using a midaxial 6-mm medial transmalleolar portal to access the medial talar dome appears to not increase the risk for subsequent vertical medial malleolar fractures in supination adduction style injuries.