A Recurrent Stress Fracture of the Humerus following Fixation: The Effect of Implant Stress Shielding

INTRODUCTION: Non-traumatic stress fractures of the humerus are often related to a throwing motion. This type of humeral fracture is often due to uncoordinated muscular activity on the humeral shaft. These forces over time may contribute to mid-shaft humeral stress fractures, an injury often referred to as a “throwers fracture.” The ultimate strength of bone is decreased when a screw hole is created, as in open reduction and internal fixation repairs (ORIF). CASE REPORT: This case study discusses a patient who underwent plate and screw fixation of a previous stress fracture of the humerus. He continued to remain active and competitive in collegiate baseball, playing the catcher position which leads to a recurrent stress fracture. A combination of low Vitamin D and stress-shielded bone likely resulted in the reinjury. Physicians treating patients with these injuries should be aware of the possibility of refracture if inciting factors are not modified. This case of a non-traumatic humeral shaft stress refracture, following ORIF, has not been described in the literature. CONCLUSION: The unusual case of a humeral stress refracture following ORIF is presented. A combination of low Vitamin D and stress-shielded bone likely resulted in the reinjury. Physicians treating patients with these injuries should be aware of the possibility of refracture if inciting factors are not modified.