Common peroneal nerve injury in the setting of multi-ligament knee injury: incidence and recovery in a prospective cohort
Authors: Whelan Daniel , Hoit Ryan Khan CCRP Graeme 
Published: July 2020

Objectives: Multiligament knee injuries (MLKI’s) are rare, but life-altering injuries which can be made worse with the presence of a concomitant nerve palsy or drop foot. Common peroneal nerve (CPN) palsy has previously been reported to be present in 5-40% of MLKI patients. The purpose of this study was to identify factors that predict CPN palsy at the time of MLKI presentation as well as determine variables that impact likelihood of neurologic recovery. Methods: Between 2006-2017, adults with MLKIs were identified at an academic level 1-trauma center and those with CPN palsy symptoms at presentation were identified. Patients were enrolled in prospective data collection and followed routinely after surgery. The primary outcome was MRC score to analyze associations between age, gender, BMI, injury severity (Schenck classification), surgical timing and presence of fibular head fracture. Secondarily, those with CPN palsy were also compared to a matched cohort of MLKI patients without CPN palsy for demographic as well as functional outcome differences using multiligament quality of life scores (MLQoL). Results: 152 patients were identified with MLKIs, of which 57 presented with a CPN palsy (38%). When comparing those with CPN palsy to those without, there were significantly more males in the CPN palsy cohort (p=0.001), significantly more lateral sided injuries – 84% versus 36% (p<0.001), and significantly more fibular head fractures – 35% versus 12% (p=0.001). There was no difference in age, BMI or injury severity or sidedness. Percentage of full or near full recovery for patients with CPN palsy at presentation was 58% (MRC>/=4). In comparing those with permanent CPN palsies to those who recovered, there was a trend towards significance for those with fibula head fractures being more likely to recover (Chi-squared 3.21, p=0.07). There was no significant difference in age, sex, BMI, sidedness, laterality, or time from presentation to surgery in terms of nerve recovery. There was no significant difference in MLQoL scores between those without CPN palsy, those with CPN palsy which recovered (MRC>/=4) and those with permanent CPN palsy (MRC<4). Analysis of MRC grading and sensory grading at presentation and factors influencing the likelihood of recovery is pending. Conclusions: The rate of CPN palsy within MLKI identified in our study matches previously reported literature. Male gender, lateral sided injury and presence of a fibular head fracture were found to be risk factors for CPN palsy at the time of injury. We found no significant difference between demographic or injury mechanism between patients who developed permanent CPN palsy and those who recovered, though there was a trend towards better recovery in those with fibular head fracture. Additionally, we found no difference between patients with CPN palsy compared to those without with respect to MLQoL scores in any domain, which calls into question whether a MLKI patient report outcome measure should incorporate nerve specific questions given the high rate of nerve injuries. The authors intend to analyze the likelihood of recovery in partial versus complete CPN palsy at the time of presentation. To our knowledge this is the largest prospectively collected dataset on CPN palsies after MLKIs, and will provide important insight into neurologic prognostication, especially when combined with previously reported data elsewhere in the literature.