Radial nerve palsy associated with humeral shaft fracture. Is the energy of trauma a prognostic factor?

BACKGROUND: Radial nerve palsy associated with humeral shaft fractures is the most common nerve lesion complicating fractures of long bones. The purpose of the study was to review the outcome of surgical management in patients with low energy and high energy radial nerve palsy after humeral shaft fractures.

METHODS: Eighteen patients were treated operatively for a humeral shaft fracture with radial nerve palsy. The mean age was 32.2 years and the mean follow up time was 66.1 months (range: 30-104). The surgical management included fracture fixation with early nerve exploration and repair if needed. The patients were divided in two groups based on the energy of trauma (low vs. high trauma energy). The prevalence of injured and unrecovered nerves and time to nerve recovery were analysed.

RESULTS: Five patients sustained low and 13 high energy trauma. All patients with low energy trauma had an intact (4) or entrapped (1) radial nerve and recovered completely. Full nerve recovery was also achieved in five of 13 patients with high energy trauma where the nerve was found intact or entrapped. Signs of initial recovery were present in a mean of 3.2 weeks (range: 1-8) for the low energy group and 12 weeks (range: 3-23) for the high energy group (p=0.036). In these patients, the average time to full recovery was 14 and 26 weeks for the low and high energy trauma group respectively. Eight patients with high energy trauma had severely damaged nerves and failed to recover, although microsurgical nerve reconstruction was performed in 4 cases. Patients with high energy trauma had a prolonged fracture healing time (18.7 weeks on average) compared to those with low energy fractures (10.4 weeks), (p=0.003).

CONCLUSIONS: The outcome of the radial nerve palsy following humeral fractures is associated to the initial trauma. Palsies that are part of a low energy fracture uniformly recover and therefore primary surgical exploration seems unnecessary. In high energy fractures, neurotmesis or severe contusion must be expected. In this case nerve recovery is unfavourable and the patients should be informed of the poor prognosis and the need of tendon transfers.