Magnetic resonance imaging of occult fractures of the proximal femur

The evaluation of the painful hip in the elderly osteoporotic patient with normal plain radiographs can be difficult. We studied 15 osteopenic patients with normal plain radiographs and suspected hip fractures with magnetic resonance (MR) imaging and found MR to be an excellent aid in detecting occult fractures. A clear fracture was seen in 10 of the 15 patients, who then underwent surgical repair based on the MR study. The remaining patients had no MR-demonstrable fracture and were successfully treated nonoperatively. Some believe that a negative bone scan in this population of patients should be repeated within 3 days prior to a definitive "no fracture" decision being made. Unfortunately, bone scanning lacks spatial resolution, and increased osteoblastic activity may be caused by other pathologic processes besides fracture. Two of the 15 patients had MR-demonstrated bone infarcts near the fracture. One patient also had femoral head osteonecrosis on the side of the fracture. One patient with metastatic prostatic carcinoma had a hip fracture and one patient with metastatic breast carcinoma had no fracture. Not only is MR imaging an excellent technique for delineating occult fractures, but due to its spatial resolution, associated bone disorders adjacent to fractures can be detected in most instances. From a cost perspective, rapid diagnosis and early treatment of an occult femoral fracture is advisable. A reduced hospital stay pending diagnosis and the early institution of definitive therapy also decrease the chance that a simple non-displaced fracture will displace and require more complex management with resultant increased morbidity and cost. We propose that, especially in elderly, osteopenic patients with normal plain radiographs and a high index of suspicion for hip fracture, MR can serve as the sole additional imaging study in most instances.