RESUMO
Stress fractures of the upper extremities are rare. Here we report the case of a 20-year old man who presented with left forearm pain for 6 weeks. He worked as a military cook and used a wok pot. Plain radiography showed periosteal reaction with cortical thickening at the midportion of the ulnar shaft without a transverse fracture line. Magnetic resonance imaging showed diffuse bone marrow edema along the ulnar shaft. Segmental cortical thickening with periosteal edema was observed on the volar side of the midshaft of the ulna. Although a typical transverse fracture line was not clearly visible, T2-hyperintense curvilinear foci were observed within the cortical thickening. Coronal T1-weighted enhanced imaging demonstrated an obliquely elongated abnormality within the cortical thickening. A longitudinal stress fracture of the ulna, of the intracortical subtype, was diagnosed. Follow-up plain radiography and computed tomography confirmed an ongoing solid union after plaster cast application. The non-neutral posture while using a straighthandled wok for flipping and repeated action likely caused cumulative trauma to the patient’s upper extremity. Clinical history taking and imaging studies using cross-sectional images may facilitate the early and accurate diagnosis of an unusual pattern of ulnar stress fracture.