Insufficiency fracture is a subgroup of stress fracture caused by the effect of normal or physiologic stress upon weakened bone.
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Insufficiency fracture is a subgroup of stress fracture. Unlike the other subtype (ie, fatigue fracture), insufficiency fracture is caused by the effect of normal or physiologic stress upon weakened bone. Loss of bone trabeculae decreases the bone's elastic resistance. These fractures are seen among older persons in spine, pelvis, tibia, fibula, and calcaneus. A strong association exists between fractures of the sacrum and those of the pubic bone (parasymphysis, pubic rami). Pubic fractures may develop as a result of increased anterior arch strain secondary to initial failure of the posterior arch (sacrum).
Insufficiency fractures are estimated to occur in 1-5% of persons, particularly in women older than 55.
Clinically, patients present with groin, low back, or buttock pain. One quarter of patients have multiple sites of pain. In most patients, pain is severe enough to render the patient nonambulatory. Usually, patients present with either no history of trauma or a history of low impact trauma.
The most common cause of insufficiency fracture is postmenopausal osteoporosis. Other important causes are senile osteoporosis, pelvic irradiation, corticosteroid therapy, and rheumatoid arthritis. Also reported are total hip replacement, Tarlov cyst, Paget disease, fibrous dysplasia, scurvy, osteopetrosis, primary biliary cirrhosis, lung transplantation, tabes dorsalis, vitamin D deficiency, and fluoride therapy.
Management is conservative and consists initially of bed rest, reduced weight bearing, and simple analgesics for pain relief. Prognosis is good; healing is expected within 4 months.
MR imaging and Bone scintigraphy are the imaging modalities of choice.
MRI shows decreased signal on T1-weighted images and increased signal on T2-weighted images. In the sacrum, signal changes are seen as linear bands within the sacral ala and body often parallel to the sacroiliac joints. On T2-weighted images, the fracture line may be seen if it is surrounded by adjacent marrow edema.
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