An unusual stress fracture in a multiple sport athlete.

Most overuse injuries are a direct result of repetitive stresses which may create a condition of maltraining. Young athletes are no exception to this rule. Swimming and baseball both create stresses to the humerus which may result in injuries to the shoulder and upper extremity. Stress fractures (fatigue fractures) are usually limited to the lower extremity (i.e., tibia or metatarsal). Upper extremity stress fractures, especially of the humerus, are very uncommon. Precipitating factors include repetitive stresses, low grade external forces, rapid application of muscular force to the bone, or an underlying disease or pathologic weakness of the bone. The majority of these fractures are primarily due to abnormal and repetitive stresses to bones. This case study examines the mechanism of injury, clinical presentation, and treatment of a clinically apparent stress fracture which ultimately converted to an overt humerus fracture in a 14-yr-old cross-trained athlete.