Common peroneal nerve injuries at the knee: outcomes of nerve repair

Background. Common peroneal nerve (CPn) lesion at the knee is one of the most frequent neurologic injury of the lower limb. Among the etiologies there are also open and closed trauma. If direct nerve repair is not possible, nerve grafting is indicated as a primary or delayed procedure. Nerve and tendon transfer are other possible therapeutic options. Material and methods. In this retrospective double center study, 35 patients with post-traumatic CPn lesion at the knee, that underwent surgical repair, were analyzed. Exclusion criteria were severe concomitant neurological pathologies, complex injury of the lower leg including major vessels lesion and or tibial nerve injury. The objective of the study is to demonstrate the degree of foot dorsiflexion recovery based on the type of trauma and the corresponding performed surgery: the Medical Research Council classification (M0-M5) was used as rating scale. Results. There were 23 closed and 12 open injuries. Time of surgery varied from 6 to 11 months after closed trauma, whereas 2 open traumas were explored at emergency and the remaining 10 patients were explored 3 to 9 months after injury. Neurolysis was performed in 12 cases. Neurorraphy was performed in 2 cases. Sural nerve grafting was performed in 21 patients, with a length range of 6-10,5 cm and 4-9 cm for closed and open trauma respectively. Conclusions. Our series confirms that repairs of traumatic CPn injuries have an unfavorable outcome. Motor recovery score ≥ M3 was obtained in only 10 cases (28,57%). Neurolysis and nerve suture show better results than nerve graft alone, although no statistically significant differences emerged; CPn reconstructions with grafts show unsatisfactory results, particularly if the length of the grafts exceeds 6 cm and when patients are treated over 6 months after the trauma. Patients with closed trauma achieve less satisfactory results than those with open injury (13 vs 58%) and this was statistically significant (p < 0.05), so palliative surgery may be indicated as the first surgical approach for these patients to achieve good foot dorsiflexion.