Snapshot A 72-year-old woman presents to the emergency room with left arm pain after tripping and falling on the sidewalk. She developed immediate pain throughout her arm. Radiographs of her left arm demonstrate a spiral midshaft humeral fracture. She is given appropriate analgesia and placed in a coaptation splint. Introduction Clinical definition fracture of the humeral shaft Epidemiology Incidence account for approximately 3% of all fractures increasing incidence in the elderly Demographics bimodal age distribution fragility fractures in the elderly high-energy traumatic fractures in younger patients Risk factors osteoporosis Etiology Low-energy injury in elderly patients High-energy injury in younger patients Pathoanatomy normal anatomy bony anatomy spiral groove (also known as the radial sulcus) is a shallow depression in the center of the lateral border of the humerus bone humeral shaft is cylindrical centrally and becomes triangular distally neurovascular anatomy radial nerve and deep brachial artery course along the spiral groove of the humerus Associated conditions radial nerve palsy forearm injuries combination of humeral shaft fracture and forearm fractures is termed floating elbow Presentation Symptoms arm pain weakness Physical exam deformity may or may not be appreciated depending on the location and severity of the fracture neurovascular examination before and after reduction is critical to identify radial nerve palsy or deep brachial artery injury radial nerve palsy (5-10%) results in loss of wrist extension (wrist drop) metacarpal phalangeal joint extension thumb abduction and extension Imaging Radiography indication always indicated if a humeral shaft fracture is suspected findings fracture patterns can vary spiral, transverse, and comminuted fracture locations can vary proximal, midshaft, and distal Differential Distal humerus fracture distinguishing factors radiographs will demonstrate a fracture in the supracondylar, lateral condylar, or medial condylar zones of the distal humerus Proximal humerus fracture distinguishing factors radiographs will demonstrate a fracture in the surgical neck or anatomic neck of the proximal humerus commonly injures the axillary nerve deltoid muscle function (i.e., arm abduction at shoulder) Treatment Nonoperative coaptation splint followed by functional bracing indication most humeral shaft fractures can be treated conservatively Operative open reduction and internal fixation (ORIF) indication severe fractures open fractures vascular injuries requiring repair brachial plexus injury concomitant ipsilateral forearm fracture (floating elbow) compartment syndrome Complications Nonunion or malunion Radial nerve palsy neuropraxia most resolve over 3 months of observation Prognosis Favorable low-energy injuries Unfavorable delay in rehabilitation high-energy injuries increased likelihood of neurotmesis (complete nerve transection)