Closed rupture of the extensor digitorum longus tendon: A case report and biomechanical analysis of rupture mechanism

Closed subcutaneous rupture of the extensor digitorum longus tendon (EDL) has been rarely documented. We present a case report of a patient with closed subcutaneous rupture of EDL. To identify the site of tendon rupture, three-dimensional computed tomography (3D-CT) was performed. The 3D-CT (volume rendering) images indicated tendon rupture of EDL on the dorsal region of the left foot. To identify the mechanisms of EDL rupture we also performed a biomechanical study using three cadavers. The patient granted permission for submission of personal data for publication. From biomechanical findings, pressure of the EDL on the inferior extensor retinaculum was 4.9–10.7 times higher in plantar flexion than in dorsal flexion of the ankle. Therefore, we believe that EDL rupture occurred with a passive flexion force pressing onto the toe tip in the plantar flexion position of the ankle joint.