Femoral Cortical Stress Lesions in Long-Term Bisphosphonate Therapy: A Herald of Impending Fracture?

OBJECTIVE: Lateral cortical stress reactions have been documented to precede femoral insufficiency fractures after long-term bisphosphonate therapy. We studied the natural history of femoral stress lesions associated with long-term bisphosphonate therapy. DESIGN AND SETTING: A retrospective clinical and radiologic review of all patients with radiologically documented femoral stress lesions associated with bisphosphonate therapy was carried out in a tertiary center involved with geriatric trauma care. PATIENTS: Of 1463 geriatric hip fractures occurring from May 1, 2004, to July 31, 2008, 33 were of a distinct metaphyseal-diaphyseal configuration. Thirty-two were on prior bisphosphonate therapy. Sixteen femurs showed a lateral cortical thickening either on prefracture radiographs (four femurs) or on radiographs of the contralateral femur (12 femurs). MAIN OUTCOME MEASURES: Features that predispose to complete stress fractures were determined. The intact femurs were followed up for symptomatic and radiologic progression and occurrence of new lesions. RESULTS: All four cases that fractured had a "dreaded black line" in the lesion, whereas only 1 of 12 patients had this fracture in femurs which remained intact (100% versus 8.3%, P = 0.003). All patients who fractured reported thigh discomfort over 1 month (range, 0.1-9.0 months; standard deviation, 4.0 months), whereas three of 12 patients who did not fracture reported thigh discomfort (100% versus 25%, P = 0.019). In the remaining patients, eight patients were asymptomatic, two patients had reduced symptoms, and one patient had persistent thigh pain at 23.0 months (range, 5-35 months; standard deviation, 10.2 months). One patient was too demented for symptomatic assessment. No patient developed a new lesion. Radiologic stabilization of the lateral cortical thickening was evident on follow-up radiographs. CONCLUSION: Cortical stress reactions associated with prolonged antiresorptive therapy, in the presence of pain and the "dreaded black line," have an increased risk for complete stress fractures.