Insufficiency Fracture of the Sternum Simulating Myocardial Infarction: Case Report and Review of the Literature

Abstract

Insufficiency fracture is a type of stress fracture that occurs when stress is applied to the bone with less than the normal elastic resistance, as in osteoporosis. Insufficiency fracture of the sternum is rare among all kinds of fractures. We describe two cases with insufficiency fractures of the sternum secondary to osteoporosis and thoracic kyphotic deformity. Both of the present cases, a 76-year-old woman and a 65-year-old woman, presented with severe anterior chest pain simulating myocardial infarction. However, cardiopulmonary examinations including chest radiographs, electrocardiograms, and laboratory tests were normal. Lateral radiographs of the sternum in both patients showed insufficiency fractures of the sternum. Conservative treatment with rib bandaging/bracing and analgesics relieved their symptoms. Clinical behavior, type of sternal insufficiency fractures, and mechanism of the fracture are reviewed from perusal of the literature. We emphasize that sternal insufficiency fracture should be considered in the differential diagnosis of acute chest pain in the elderly along with myocardial infarction or pulmonary embolism. insufficiency fracture; sternum; osteoporosis; myocardial infarction

Atraumatic sternum fracture

“…Most of the reported cases with sternum insufficiency fractures occurred in the sternal body, as in this case and rarely in the manubrium sterni 6. Stress fractures can be classified into fatigue fractures caused by repetitive subthreshold trauma, insufficiency fractures occurring in bones with decreased mechanical strength and pathological fractures, which occur in diseased bones 7…”

“…A buckling sternal fracture is defined as a sternal deformity in which the upper portion of the sternum is located posterior to the lower portion and in which there has been no cortical disruption, focal bone resorption or callus formation. All the other sternal fractures, excluding the buckling type, were classified as the non-buckling type 6 11…”

“…Fractures of the sternum have mainly been reported as resulting from trauma, secondary malignancy, myeloma and, rarely, secondary to osteoporosis 6 13. Sternum insufficiency fracture typically occurs in osteoporotic bone among the elderly.…”

“…This can partly be explained by Fowlers flexion—compression theory, where fractures occur secondary to bending and compression stresses from the thoracic kyphotic deformity with multiple osteoporotic thoracal vertebral compression fractures. The deforming stress on the sternum, combined with the loss of elasticity associated with the ossification of the costal cartilages in elderly patients increases the risk of sternal fracture, and these bones may not even have the elastic strength to withstand minimal stress from activities of daily living 6 7 13 14. Sternum insufficiency fractures also occur without thoracic kyphosis as emphasised by Chen et al 11…”

Sternal fractures

“…In the presence of a thoracic kyphosis normal flexion and extension of the spine can produce insufficiency fractures of the sternum (Fowler, 1937;Horikawa et al, 2007;Latzin et al, 2005, Robertson, 1955. The majority of insufficiency fractures occur in the body of the sternum, very few in the manubrium.…”