Evaluation an altered neurophysiological functions of motor branches of deep peroneal nerve in lateral ankle sprain patients

Introduction: Inversion sprain is a result of abnormal forces of plantar flexion and inversion applied to the lateral side of the ankle. This injury recurs in 10% of non-athletes and 80% of athletes. It is believed that Changes in conduction of deep peroneal nerve following inversion sprain and instability occurred following it, to be a cause of recurrence of inversion sprain. Evaluation of the motor branches of deep peroneal nerve in inversion sprain in non-athletes persons is the base of this study. Material and Methods: Mechanical instability is assessed through anterior drawer test and talar tilt test and electrical assessment is done first and four weeks after injury in 11 patients in each mechanical instability group of the ankle. All patients had the first incidence of unilateral inversion sprain and normal side was considered as control in the same patient. Electrical assessment of deep peroneal nerve included following: (1) Deep peroneal nerve motor conduction studies in three levels of knee, leg and ankle, (2) Electrical evaluation of tibialis anterior muscle both at rest and minimal contraction. Results: Studies revealed significant changes in temporal dispersion in three levels of knee, below the head of fibula and ankle and motor latency in knee and ankle levels both at the first and second evaluation and motor nerve conduction velocity in leg at the first session in two extremities but no significant difference between mechanical instability was noticed. Also there was a significant difference in recruitment interval of tibialis anterior muscle in comparison of normal and involved extremity and mechanical instability at both sessions. Conclusion: Findings of this study indicated that in lateral ankle sprain deep peroneal nerve incurs is happened and its prognosis is dependent on severity of nerve involvement and grade of instability.