Increased Medial Displacement of the Humeral Shaft of at Least 40% Correlates With an Increased Incidence of Nerve Injury in Proximal Humerus Fractures.

backgroundPeripheral nerve and infraclavicular brachial plexus injury following proximal humerus fractures are commonplace, but diagnosing a concomitant nerve injury in the acute setting is challenging. Fracture displacement has been identified as a qualitative risk factor for nerve injury, and additional attention should be paid to the neurologic exams of patients with proximal humerus fractures with significant medial shaft displacement. However, a quantitative relationship between the risk of nerve injury and medialization of the humeral shaft has not been shown, and additional risk factors for this complication have not been assessed. The aim of this study was to identify the risk factors for a neurologic deficit following a proximal humerus fracture, with particular interest in the utility of the magnitude of medial shaft displacement as a predictor of neurologic dysfunction.

methodsA retrospective chart review was performed on all proximal humerus fractures in a 3-year period (2012-2015) at a level one trauma center. Isolated greater tuberosity fractures (OTA 11-A1) were excluded. Fracture displacement was measured on initial injury AP shoulder radiograph and expressed as a percentage of humeral diaphyseal width. All orthopedic inpatient documentation was assessed to identify clinical neurologic deficits.

resultsWe identified 139 patients for inclusion. There were 22 patients (16%) with new neurologic deficits at presentation (8 axillary nerve, 2 radial nerve, 12 infraclavicular brachial plexus or multiple nerve injuries). The average shaft medial displacement in patients with neurologic injuries was 59% vs. 21% without nerve deficits (p=0.03). Using a 40% medial displacement threshold, the odds ratio for a nerve injury was 5.24 (95% CI 1.54 - 17.77, p=.008).

conclusionIncreased medial displacement of the humeral shaft following proximal humerus fracture is associated with an increased incidence of nerve injury at the time of initial presentation. This finding is not meant to be a surrogate for a high-quality neurologic exam in all patients with proximal humerus fractures. However, improved knowledge of the specific risk factors for an occult neurologic injury will improve the clinician's ability to accurately diagnose and properly treat proximal humerus fractures and their sequelae.