PLANTAR FLEXION INJURIES OF THE ANKLE - AN EXPERIMENTAL-STUDY

A biomechanical study was designed to test the hypothesis that isolate d plantar flexion of the ankle can produce avulsion fractures of the m edial and lateral malleoli without fracture of the posterior articular surface of the tibia. Cadaver specimens were subjected to a standard plantar flexion force in the Burstein torsion testing machine. They sh owed the following typical patterns of injury in 26 of 32 ankles: (1) avulsion of the anterior ankle capsule; (2) a short oblique distal fib ular fracture or fibular avulsion of the anterior talofibular ligament ; and (3) an oblique medial malleolar fracture or a tear of the deep f ibers of the deltoid ligament. Of particular interest was the directio n and location of the medial malleolar fracture. This pattern, previou sly identified with supination-external rotation injuries, was also pr oduced by isolated plantar flexion, which may be attributed to the ana tomical attachments of the deltoid ligament on the medial malleolus, a s well as the position of the foot and direction of the injuring force .