21 Feb The Evaluation and Management of Sacral Insufficiency Fractures
What is the sacrum and why does it fracture?
The pelvis is a ring of bones that provides structure and stability. The bony pelvis consists of the sacrum, coccyx, and three innominate bones: the ilium, ischium, and pubis. The sacrum sits along the back of the pelvic ring and articulates with the ilium forming the sacroiliac joint.
During gait, there is significant torsional movement of the sacrum and sacroiliac joints. With osteoporosis or low bone density, the stress transferred to the sacrum may overwhelm the bone and result in an insufficiency fracture—a fracture resulting from normal stresses on an abnormal bone.
While these fractures typically present atraumatically, about a third of fractures occur after a minor fall. Sacral fractures can be unilateral or bilateral and most commonly affect the lateral aspect of the sacrum or sacral ala.2
Who develops sacral insufficiency fractures?
One study determined the incidence of pelvic insufficiency fractures to be 92 per 100,000.1 Sacral insufficiency fractures occur twice as commonly in women compared to men, with increased risk associated with advanced age.3 These fractures most commonly occur in those over 70-80 years old.4
In addition to advanced age, risk factors include prior pelvic fracture, low body weight, long-term steroid use, smoking, and alcohol intake. Additional risk factors include a history of pelvic radiation, Paget’s disease, rheumatoid arthritis, multiple myeloma, chronic kidney disease, diabetes, osteoporosis, vitamin D deficiency, and prolonged immobilization.
How is a sacral insufficiency fracture diagnosed?
Most patients present with significant low back pain without a history of trauma, while some present after a minor fall. Symptoms will often be present in the low back, hip, buttock, or groin and are usually worse with weight-bearing and improved with rest.
An exam will often demonstrate antalgic gait, sacral tenderness, and painful hip range of motion and may show positive provocative maneuvers of the sacroiliac joint. An evaluation should also involve a neurological examination as rarely sacral insufficiency fractures can cause neurologic deficits.
Patients may also have pain in other areas of the pelvis. Disruption of one site of the pelvic ring may cause increased stress on other parts of the ring. One study found that 78% of patients with sacral stress fractures had a coexisting pubic rami fracture.5,6
What is the right test for a sacral insufficiency fracture?
X-rays are the first-line imaging modality to diagnose a sacral insufficiency fracture but are often inconclusive as these fractures can be missed. If there is a high suspicion of a fracture, an advanced image may be ordered.
MRI is the gold standard for detecting these fractures and reveals whether the fracture is new or old. If the patient cannot have an MRI, a CT or SPECT scan is an acceptable alternative and has great sensitivity in the evaluation of bone pathology.
How is a sacral insufficiency fracture treated?
After a sacral insufficiency fracture is diagnosed, further workup with a DEXA scan should be performed to evaluate bone mineral density, due to the high incidence of osteoporosis in this population. If low bone mineral density is found, calcium and vitamin D supplementation and pharmacological management may be utilized to maintain bone health.
Treatment for fractures is typically non-operative and includes medications such as acetaminophen and in some cases, short-term opioids for patients with severe pain that is limiting function. Anti-inflammatories (NSAIDs) should be avoided in the older patient population due to significant known risk factors. In addition, NSAIDs may also impair bone healing.
Early mobilization with weight bearing as tolerated, physical therapy, or aquatic therapy is helpful to maintain muscle mass and strength. Some patients with severe pain on ambulation may require an assistive device, for mobility. Typically with the above approach, clinical healing occurs over six to eight weeks.
See Us At Desert Spine & Sports Physicians
If you or your patient has low back pain that is concerning for a sacral fracture, please contact Desert Spine and Sports Physicians so that our team of highly trained specialists can help diagnose and treat the problem. Our goal is always to decrease pain and improve function for all of our patients.