Peroneal Nerve Palsy Associated with Knee Luxation: Evaluation by Sonography--Initial Experiences

Traumatic knee dislocation needs immediate surgical repair to restore joint function. A concomitant traction injury of the peroneal nerve is reported to exist in up to 25% of cases and is often overlooked initially. In patients with major nerve lesions, immediate surgical nerve repair might be necessary to avoid irreversible loss of neural function. In the present study, we tried to evaluate whether sonography is a valuable tool for identification of nerve pathology that warrants surgical intervention. In this prospective study, both peroneal nerves in nine patients with one-sided peroneal nerve palsy after closed knee luxation and the peroneal nerves of 11 healthy volunteers were investigated with sonography. Using statistical analysis, we tried to define the comparability and significance of the findings. The mean cross-sectional area of healthy peroneal nerves in the genicular region was 0.18 cm2 (SD, 0.07 cm2). Impaired nerves were significantly discerned because of their increased cross-sectional area at the level of the injury (mean cross-sectional area, 0.7 cm2; SD, 0.46 cm2; p < 0.05). Identification of caliber changes and depiction of at least one nerve stump were found to be the most specific criteria for the definition of a major neural lesion. The ability of sonography to provide additional information about surrounding soft-tissue impairment (scar tissue and hematoma formation) proved helpful. Sonography allows radiologists to visualize neural and extraneural pathology and to define the exact level and extent of lesions. Thus, it may be a valuable adjunct in the decision of whether surgical intervention is necessary.