Peroneal Nerve Injury after Multiligament Knee Injury: a 12 Year Experience with a Focus on Outcomes after Posterior Tibial Tendon Transfer

OBJECTIVES: The incidence of neurologic injury with multi-ligament knee injuries (MLI) ranges from 10% - 40% and most commonly involves the peroneal nerve. Loss of active ankle dorsiflexion and/or eversion with persistent post-traumatic peroneal nerve palsy portends substantial morbidity as patients may require lifetime use of an ankle-foot orthosis (AFO). Neurolysis, nerve grafting, and nerve transfer have limited efficacy in restoring function. For selected patients with footdrop, posterior tibial tendon (PTT) transfer may restore active dorsiflexion and mitigate AFO dependency. The objectives of this study are: 1) to review all MLI over a 12 year period to help clarify the epidemiology of peroneal nerve injuries; and 2) to compare the outcomes of PTT transfer with non-operative management for these injuries. METHODS: Study Design: Retrospective cohort study. The charts of all patients with MLI over the past 12 years were reviewed. A cohort of MLI patients with peroneal nerve injury (n=18) was compared to the entire cohort of MLI patients (n=215). Patients with peroneal nerve injury managed non-operatively (n=11) were compared to those managed with PTT transfer (n=7). The clinical outcomes in patients who underwent PTT transfer were reviewed. Analysis: Means and ranges were calculated for continuous variables (age, BMI) and compared between cohorts using Student’s t test. Frequencies for categorical variables were compared using chi square tests. RESULTS: The peroneal nerve injury cohort had significantly higher BMI, greater prevalence of female gender, higher rate of posterolateral corner (PLC) injury, and lower rate of PCL injury (Table I). Within the peroneal nerve injury cohort, there were no significant demographic differences between patients who underwent non-operative treatment (n=11) and those who had PTT transfer (n=7) (Table II). At an average follow-up of 23.9 months, patients who underwent PTT transfer for peroneal nerve injury demonstrated significant improvement in active ankle dorsiflexion, strength in ankle dorsiflexion and eversion, and elimination of AFO use. (Table III) CONCLUSION: The management of peroneal nerve injury in the setting of multiligament knee injury remains challenging. Understanding the epidemiology of these injuries allows treating surgeons to identify and stratify at-risk patients preoperatively. In appropriately selected patients, posterior tibial tendon transfer is an option to improve ankle function, regain ankle active dorsiflexion and most importantly eliminate the need for a life-long orthosis.