Teaching Case

An elderly female with osteoporosis and a focus of increased activity in the sternum on scintigraphy.

A 61 years old female presented with a 2 month history of low- thoracic back pain and increasing thoracic kyphosis. Osteoporosis had been previously diagnosed on DEXA bone densitometry. There was no history of trauma , steroid use or concurrent illness . Radiographs of the thoracic spine show generalized osteopaenia and kyphosis with vertebral body collapse at T 8,10,12 and L 2 (Fig 1). Scintigraphy (Technecium 99) demonstrates multiple areas of increased activity in the thoracic and lumbar spine corresponding with the osteoporotic vertebral body insufficiency fractures (Fig 2). A focal area of increased uptake was also present in the sternum suggesting an insufficiency fracture here also. Radiographs (Fig 3) and MRI (Fig 4) of the sternum confirmed a displaced fracture through the manubrium sterni .There was no history of anterior chest pain but on examination there was localized tenderness over the manubrium.The patient was treated with intravenous biphosphonates.

Insufficiency fractures occur when normal stresses are applied to a pathological bone resulting in deficient elastic resistance (1).Although sternal fractures due to trauma are common , insufficiency fractures of the sternum are uncommon and usually associated with generalized osteoporosis .Accentuated thoracic kyphosis, due to vertebral body compression fracture (usually multiple), places a deforming stress on the sternum predisposing to fracture (2). Occasionally, however , sternal insufficiency fractures occur in the absence of a kyphosis, presumably due to acute flexion-compression stresses applied to the sternum during forward bending (3).Isolated fatigue fractures of the sternum have also been described (4).Clinically they have a wide spectrum of presentation; they may be asymptomatic and discovered incidentally on various imaging modalities or present with acute, severe chest pain and be confused with acute cardiopulmonary emergencies (5).The fracture may be displaced or non-displaced , and associated bone resorption at the fracture site with a soft tissue mass may simulate a pathological fracture due to ,for example ,metastasis (3).Insufficiency fractures of the sternum , and their association with osteoporosis , are important to recognize because their appearances on various imaging modalities may be confused with other pathological processes , for example , metastases and multiple myeloma.