Figure 1. Magnetic resonance imaging of the pelvis.
A 74-year-old woman presents to the office for evaluation of bilateral hip and buttock pain that started 1 month. She describes the pain as constant and stabbing (10/10 on a numeric rating scale). She denies a fall or known precipitating event. On physical examination, the patient has pain to palpation over the lower back and buttock but no hip pain with bilateral range of motion testing. She is having difficulty ambulating, even with the assistance of a walker. Prior to pain onset, she did not require an assistive device for ambulation. Radiographs of bilateral hips and pelvis are unremarkable for a fracture or arthritis. A pelvic MRI (Figure 1) shows extensive edema throughout the entire sacrum and bilateral sacral insufficiency fractures with no step-off of bone.
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Sacral insufficiency fractures are an often overlooked source of lower back and buttock pain in older adults, especially elderly women. Advanced age and female sex are risk factors for osteoporosis-related stress fractures such as insufficiency fractures.1,2
Sacral insufficiency fractures are usually bilateral and often result from little to no trauma. Normal repetitive stress placed on weakened osteoporotic bone can lead to a stress injury.1,2
The most common presenting symptoms include lower back and buttock pain with difficulty walking. Patients may also have leg symptoms that mimic lumbar radiculopathy. Lying supine is often the most comfortable position for patients. Plain radiographs are usually normal and an MRI is often required to see bone marrow edema associated with stress injury in the sacrum.1,2
Treatment involves early ambulation with a walking aid such as a walker or crutches. A sacral insufficiency fracture is a stable injury and patients can remain weight-bearing as tolerated without fear of fracture displacement. Patients may need a walking aid for 8 weeks or more depending on symptom resolution. Most importantly, patients with sacral insufficiency fractures should be worked up for osteoporosis.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopaedics for Physician Assistants.
1. Schindler OS, Watura R, Cobby M. Sacral insufficiency fractures. J Orthop Surg (Hong Kong). 2007;15(3):339-346. doi:10.1177/230949900701500320
2. Tsiridis E, Upadhyay N, Giannoudis PV. Sacral insufficiency fractures: current concepts of management. Osteoporos Int. 2006;17(12):1716-1725. doi:10.1007/s00198-006-0175-1