Pelvic insufficiency fractures in patients with pelvic irradiation

Insufficiency fractures (IF) occur as a result of normal physiological stress on bones with deficient elastic resistance. Pelvic insufficiency fractures are a complication of osteoporosis due to postmenopausal status, high dose of corticosteroids, or local irradiation. They are important because differential diagnosis includes pelvic bone metastases. Diagnosis is based on both clinical manifestations and radiographic and scintigraphic findings.

We examined eight patients with pelvic cancer who had previously undergone external beam radiation therapy as part of their treatment. In the follow-up, they developed insufficiency fractures, and no factor other than pelvic irradiation was present. Diagnosis was confirmed by radionuclide bone scan followed by conventional radiography and computed tomography (CT) scan.

The average onset of symptoms was 13.7 months after radiation therapy was completed. The initial symptom in all cases was pain. In all of the patients, the bone scan showed abnormalities. One to four increased uptake foci were observed, in the sacroiliac joint in all cases, and in the pubis in three cases. The initial diagnosis was bone metastases in five patients. CT scan showed fractures in all of the patients, in sacrum and pubis, both endostic and cortical. Treatment, consisting of nonsteroidal anti-inflammatory drugs and rest, led to symptomatic relief in all cases.

Knowledge of pelvic insufficiency fractures is essential in order to rule out metastasic disease, and thus avoid inaccurate treatment. Although radionuclide bone scan is useful in early detection of pelvic IF, definitive diagnosis is provided by CT scan.