A common peroneal nerve (CPN) palsy has been reported to complicate knee dislocations in 5-40 % of patients. Patients who suffer from a persistent foot drop have significantly worse functional outcomes. Reports on prognostic factors for nerve recovery or treatment-specific functional outcomes remain sparse in the literature.
Two independent reviewers completed a search of Medline, Embase, PubMed and the Cochrane Library from 1946 to present. Motor strength was determined using the Medical Research Council (MRC) grading system or an equivalent description. A functional recovery was defined as an MRC ≥3/5.
The combined search of Medline, Embase, PubMed and the Cochrane Library identified 1528 abstracts. Thirteen articles met our inclusion/exclusion criteria. This included 214 CPN palsies. Functional recovery (MRC ≥3/5) following complete CPN palsy was 38.4 %. Full recovery (MRC = 5/5) following partial CPN palsy was 87.3 %. Younger age was predictive of neurologic recovery. Recovery following isolated neurologic interventions ranged from 0 to 30 %.
A vastly different prognosis can be expected for patients who suffer an incomplete versus a complete CPN palsy. The majority of patients with an incomplete palsy will achieve a full motor recovery while < 40 % of patients with a complete motor palsy will regain the ability to dorsiflex at the ankle. While neurologic interventions show promise for the future, the outcomes in knee dislocation patients remain poor. The most predictable means of reestablishing antigravity dorsiflexion in a persistent CPN palsy is a posterior tibial tendon transfer.