Introduction Humeral shaft fractures can lead to radial nerve injury and may require surgery and rehabilitation. We determined the causative events of humeral fracture, including arm wrestling, in young Korean soldiers and examined whether humeral fracture is related to demographic characteristics and the presence of radial nerve palsy.

Methods We reviewed 7.5 years (July 2012 to June 2019) of medical records covering patients who had experienced a humeral shaft fracture after entering military service and had received surgery for open reduction and internal fixation. Data were obtained on basic demographics, initial event provoking the fracture, presence of radial nerve palsy, initial and follow-up severity of the weakness, and any discharge from military service because of prolonged radial nerve palsy.

Results Of 123 cases, arm wrestling was the leading cause (52.8%). A high energy injury, such as falling from a height (11.4%), and sports related slips (10.6%) were other causes. All humeral shaft fractures caused by forceful contraction were spiral, while 40% of the fractures caused by external force related events were of a transverse type. The percentage of left-sided fractures was significantly higher for fractures arising from an external force than in those caused by forceful contraction related events. Radial nerve palsy was found in 34 patients (27.6%), and 16 were discharged from the military because of prolonged radial nerve palsy 6 months after the fracture. The causative events and other factors did not affect the presence of radial nerve palsy.

Conclusion Arm wrestling was the leading cause of humeral fracture in young Korean soldiers but the chance of developing comorbid radial nerve palsy did not differ from that of other causes. These epidemiologic findings in this young active group may help in understanding the causes of humeral shaft fracture in soldiers and in the wider young population.