Postpartum sacral stress fracture: an unusual case of low-back and buttock pain.

Low-back and buttock pain is a common complaint during pregnancy and the postpartum period and is usually attributable to mechanical lesions of the pelvis. Sacral stress fractures are unusual but important causes that should be considered in differential diagnosis. To date, only eight postpartum sacral stress fractures have been reported in the literature. A 32-yr-old woman presented with low-back and right buttock pain that started 15 days after uneventful cesarean section delivery. Imaging studies revealed a right sacral stress fracture. Lumbar spine and femoral neck bone mineral density were normal and, except for pregnancy and lactation, no risk factors for osteoporosis were identified. There was no history of trauma, excessive weight gain, strenuous physical activity, or contribution of mechanical factors. The question remains whether this is an insufficiency fracture or a fatigue fracture. Clinicians should consider sacral fracture during pregnancy and the postpartum period as a diagnostic possibility in patients with low-back and/or buttock pain.