Ankle injuries are a common musculoskeletal affliction. One mode of ankle injury is due to extreme dorsiflexion. This phase of the ankle injury project addresses injuries to ankles involving dorsiflexion, in particular at high rates of loading such as might occur in automotive accidents. High rates of axial compression loading were also investigated. The types of injuries include malleolar fractures and ligament avulsions and ruptures.
Twelve pair of cadaver and two Hybrid III lower limbs were loaded on the bottom of the foot via a pneumatic cylinder. The rate of loading varied from pseudostatic to 7 m/s in dorsiflexion mode and in axial tests the load was applied for 50, 100 or 500 ms with a rate of loading of approximately 500 kN/sec. Standard range of motion tests were done before and after testing. Human volunteers were tested for maximum voluntary dorsiflexion in a separate fixture which recorded torque and dorsiflexion angle.
Dorsiflexion angles up to 80 degrees were recorded with injuries occurring between 35 and 59 degrees of dorsiflexion angle. Injuries were observed occurring from high speed films of the denuded ankle joint. Moment at the ankle joint of up to 200 Nm were calculated with injuries occurring at between 40 to l00 Nm. Angular deflection appears to be the best predictor of injury. Cadavers were able to sustain axial loads up to 7500 N for 100 ms without injury. Loads sufficient to cause injury in axial loading were not attained. Relaxed volunteers were Well able to tolerate 30 N m torque on the ankle joint at angles up to 45 degrees.