Clinical and Functional Outcomes after Multiligament Knee Injury with Associated Peroneal Nerve Palsy: Comparison with a Matched Control Group at 2-18 Years

OBJECTIVES: Peroneal nerve injuries are not uncommon with multiligament (ML) knee dislocations. However, there remains little information on outcome of these injuries. Therefore, the purpose of this study was to (1) report the clinical and functional outcomes after ML knee injury with concomitant peroneal nerve palsy, (2) compare recovery and outcome with partial versus complete peroneal nerve injury, (3) compare outcomes to a matched cohort of ML knee injuries without concomitant peroneal nerve palsy. METHODS: Patients that underwent surgical reconstruction of a ML knee injury from 1993 to 2010 were reviewed and concomitant nerve injuries were identified, forming the peroneal nerve injury group (PI). Patient demographics, injury mechanism, modified Schenck classification, and peroneal nerve function, treatment, and recovery were documented. Patients were divided into two sub-groups: complete peroneal nerve palsy (CNP) and partial peroneal nerve palsy (PNP). A second group of patients with ML knee injury without peroneal nerve injury were identified, forming the no nerve injury group (NI). The PI and NI groups were matched based on Modified Schenck Classification, age, and gender. Peroneal nerve motor grade was assessed at last clinical follow-up and outcome scores were obtained using the International Knee Documentation Committee (IKDC) and Lysholm forms at a minimum of 2 years post-op. Data was analyzed using univariate and multivariate models to assess for predictive factors between the groups. RESULTS: 27 patients (24 males, 3 females) met inclusion criteria for the PI group (9 CNP and 18 PNP). Treatment for CNP included an AFO for all patients, non-operative (1), neurolysis (2), tendon transfer (3), nerve transfer (1), and combined nerve/tendon transfer (1). One patient in the CNP group required additional surgery, undergoing below knee amputation. Treatment for PNP included non-op (12), neurolysis (4), nerve transfer (1), and combined nerve/tendon transfer (1). 2 patients with incomplete nerve palsy required additional surgery, undergoing an arthrodesis and a total knee arthroplasty. 3 CNP (37.5%) and 15 PNP (83.3%) regained 3/5 or greater tibialis anterior (TA) strength. PNP was associated with increased recovery of 3/5 extensor hallucis longus (EHL) strength (p=0.0093). Outcome scores were obtained for 17 of the remaining patients at a mean 6.6 (range 2-18) years. Univariate analysis revealed no difference between the CNP and PNP groups. Final motor grade of 3/5 did not predict improved outcomes. Not undergoing a tendon transfer procedure predicted better outcomes on the IKDC score (70.5 vs 45.0; p=0.027). All other peroneal nerve interventions were not associated with improved motor or functional outcome. 20 patients formed the NI group. The PI and NI groups were matched on gender (18 M, 2 F), age (mean 30.8 vs 29.5 years), and Modified Schenck Classification (2 KD-I, 10 KD-IIIL, 5 KD-IV, 3 KD-V vs 2, 7, 8, and 3 respectively). In univariate analysis, the PI group had inferior outcomes on both the IKDC (64.5 vs 77.3; p=0.036) and Lysholm (67.1 vs 83.0; p=0.023) scores. CONCLUSION: Patients with partial peroneal nerve palsy are more likely to regain antigravity EHL strength, but not antigravity TA strength. There is no significant difference in outcomes between partial and complete peroneal nerve palsy. In ML knee injuries, patients with peroneal nerve injury have significantly worse outcomes than similar patients without peroneal nerve injury.