"Natural history of low velocity ballistic nerve injuries to the humerus".

OBJECTIVES

To assess ballistic humerus fractures with nerve injuries, their associated characteristics, and functional recovery.

DESIGN

Retrospective review

SETTING

Level 1 trauma center over 10-year period.

PATIENTS: 143 patients presenting with low-velocity ballistic humerus fractures.

INTERVENTION: Operative intervention and clinical examination of nerve function.

MAIN OUTCOME MEASUREMENTS: Nerve injury incidence and recovery.

RESULTS

The overall incidence of nerve injury was 21% (30 injuries/143 fractures) with 66.7% of fractures treated operatively. Nerve injury varied based on anatomic region: 28.6% (12/42) distal humerus; 20% (15/75) shaft and, 11.5% (3/26) proximal humerus. Arterial injury (p = 0.011) and bone loss (p = 0.0001) were significantly associated with nerve injury. The nerve was visualized during index surgery in 15 patients, with 4 transections. Multiple nerve injuries (n = 6) were most common around the distal humerus: 41.7% (5/12). The radial nerve comprised 52.9% (n = 9) of injuries in the distal humerus and 62.5% (n = 10) in the shaft with spontaneous recovery occurring in 75% (6/8) with distal fractures and 66.7% (6/9) with shaft fractures. The ulnar nerve accounted for 35.3% (n = 6) of injuries in the distal humerus and 25% (n = 4) in the shaft. Spontaneous recovery occurred in 60% (3/5) of ulnar nerve injuries around distal fractures but in only 25% (1/4) in the shaft. Half of ulnar nerve injuries were associated with additional nerve or vascular injury. The median nerve was the least likely to be injured: 40% (n = 2) distal humerus, 40% (n = 2) shaft, and 20% (n = 1) proximal humerus and 40% (2/5) spontaneously recovered.

CONCLUSION

In the setting of ballistic humerus fractures, arterial injury and bone loss were significantly associated with nerve injury. Multiple nerve injury occurred most commonly at the distal humerus. There was a 60-75% recovery rate of most nerve injuries however, ulnar nerve injuries around the shaft and median nerve injuries had lower rates of recovery.

LEVEL OF EVIDENCE: Level III.