Working Diagnosis:
Left fibular head stress fracture in the setting of osteoporosis and vitamin D insufficiency

Treatment:
Our patient was started on calcium and vitamin D supplementations. Physical therapy and insoles were recommended to correct biomechanical forces possibly contributing to his stress fracture. He was unwilling to be non-weight bearing or partial weight bearing. Instead, he took an additional three weeks off from work with reported improvement in pain. He started denosumab injection therapy every 6 months for osteoporosis treatment.

Outcome:
Given the improvement in his pain with relative rest, our patient returned to work as a doorman and superintendent, although he continued to avoid heavy lifting and impact activities. He continued with denosumab therapy for osteoporosis.

Author's Comments:
Most fibular stress fractures occur in the distal 1/3 of the fibula. Proximal fibular stress fractures are uncommon. A 2009 study identified 10 proximal fibular stress fractures in 635 military recruits undergoing 6 weeks of training with repetitive walking/jumping in a squatting position (1). Our patient did not have this type of biomechanical stress. His healed right proximal fibular fracture was likely from his childhood trauma. No risk factors for osteoporosis were identified other than poor diet and geography, as he lives in the Northeast.

Editor's Comments:
Fibular stress fractures in general are uncommon, and when they do occur, most often involve the lateral cortex of the distal 1/3 of the fibula secondary to repetitive plantar flexion. (2) This case highlights a rare example of proximal fibular stress fractures secondary to osteoporosis. Risk factors for osteoporosis include low body weight, alcohol use, previous fractures, female gender, of 65 years old glucocorticoid use, and tobacco use (3). Treatment for osteoporosis is achieved through education, vitamin D and calcium supplementation and bisphosphonates or anti-RANKL agents such as denosumab.

References:
1. Hong SH, Chu IT. Stress fracture of the proximal fibula in military recruits. Clin Orthop Surg 2009; 1:161.
2. Mandell, JC, Khurana B. Stress fractures of the foot and ankle, part 2: site-specific etiology, imaging, and treatment, and differential diagnosis. Skeletal Radiology 2017,, 46: 9.
3. Ensrud, KE, Crandall, CJ. Osteoporosis. Annals of Internal Medicine 2017. 167 (3).

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