Working Diagnosis:
Midshaft humerus fracture secondary to underlying stress fracture.

Treatment:
Initial treatment in the Emergency Department was a posterior long arm splint. He was placed in a hanging arm brace at the Sports Medicine Clinic one day later. He was switched to a Sarmiento brace (upper arm functional brace) at 4 weeks post injury Case Photo #2 . Functional bracing for the treatment of fractures of the humeral diaphysis is associated with a high rate of union (1). Bracing was continued until 8 weeks post injury. Interval imaging was obtained at 3 and 4 months post injury. Case Photo #3 Case Photo #4

Outcome:
Gradual return to sport related activities at 4 months post injury following physical therapy.

Author's Comments:
Our patient was ultimately diagnosed with a midshaft humerus fracture likely secondary to humeral stress fracture. Approximately 9% of stress fractures occur in the upper extremity and have been known to occur in athletes that perform repetitive overhead activities such as baseball, tennis, and CrossFit (2). The pediatric population is especially susceptible to overuse injuries secondary to improper technique, muscle imbalance, and varied skeletal maturity (3).
The insidious onset of mid humerus pain with increasing activity in this case certainly lends evidence to a stress fracture developing before the midshaft humerus fracture. Calcium deficiency could have also contributed to stress fracture formation. A systemic review and metanalysis showed that overall mean serum (25 (OH) D levels were significantly lower for stress fracture cases than controls in the military (4). Osteosarcoma and chronic multifocal osteomyelitis were considered due to the mechanism of injury, but no evidence of such processes were discovered. This case highlights the importance of the early recognition of humeral stress fractures in susceptible populations to prevent further injury.

Editor's Comments:
Though uncommon, this case reminds the clinician not to forget about stress fractures in the upper extremity. Upper extremity pain can easily be mistaken for a muscle strain. So in counseling a patient, especially when the pain does not fit the typical muscle pain pattern, proceed with further work up as needed. The key finding was mid-upper arm pain without shoulder pain or trauma. As for other uncommon causes of non-contact fracture, the team taking care of this patient made sure to rule out a malignancy via the MRI, another "pearl" when caring for unusual fractures.

References:
1. Kibler WB, Safran M. Tennis injuries. Med Sport Sci. 2005;48:120-137.
2. DiFiori Jp, Benjamin HJ, Brenner JS, et al. Overuse injuries and burnout in youth sports: a position statement from the American Medical Society for Sports Medicine. Br J Sports Med. 2014; 48 (4):287-288
3. Bell DR, Post EG, Biese K, et al. Sport specialization and risk of overuse injuries: a systematic review with meta-analysis. Pediatrics. 2018;142:e20180657.
4. Functional bracing for the treatment of fractures of the humeral diaphysis; A Sarmiento, J B Zagorski, G A Zych, L L Latta, C A Capps, J Bone Joint Surg Am; 2000 Apr;82(4):478-86.
5. Allen GJ. Longitudinal stress fractures of the tibia: diagnosis with CT. Radiology, 1998; 167(3):799-801
6. Tisano BK, Estes AR. Overuse injuries of the pediatric and adolescent throwing athlete. Med Sci Sports Exerc. 2016;48:1898-1905.
7. Dao D, Sodhi S, Tabasinejad R, et al. Serum 25-hydroxyvitamin D levels and stress fractures in military personnel: a systematic review and meta-analysis. Am J Sports Med. 2015;43:2064-2072.

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