Stress fractures in a patient with polyostotic fibrous dysplasia receiving long term intravenous pamidronate (#317)
Fibrous dysplasia (FD) is a benign skeletal lesion, resulting in recurrent childhood fractures and can be associated with McCune-Albright syndrome and one or more hyperfunctioning endocrinopathies.
We present a case of a 20-year-old gentleman presenting with multiple fractures during childhood due to polyostotic FD. He was stabilized with intravenous pamidronate for 7 years and then suddenly complained of right thigh pains due to the diagnosis of new spontaneous stress fractures.
He was diagnosed aged 8 years with a right femur fracture requiring open reduction internal fixation. Refracturing occurred in 1996, 1997 and 1999. Physical examination showed no bony deformities. Leg length was normal bilaterally. He did not have any underlying endocrinopathies. A head CT scan demonstrated FD involving the base of the skull. X-rays demonstrated FD, an intra-medullary nail and areas of lucency affecting the mid and supra-lateral aspect of the right femur. Technetium bone scan (TBS) demonstrated polyostotic involvement of the right half of the skeleton. Bone turnover markers were elevated. Intravenous pamidronate (90 mg) was administered monthly for 6 months due to high-risk lesions (skull and long bones) and thereafter yearly. His bone turnover markers normalised. In January 2013, he complained of right thigh pains. TBS and MRI confirmed two new cortical stress fractures along the lateral aspect of the proximal femoral shaft.
This case raises the differential diagnosis of a new fracture in a man with FD who had remained fracture-free for 7 years. The possibilities include (a) active FD, (b) atypical femoral shaft fractures due to over-suppression of bone turnover from prolonged bisphosphonate administration and (c) the rare possibility of fracture through malignant bone. Newer anti-resorptive agents such as Denosumab and Odanactib which do not suppress bone formation to the same intensity as bisphosphonates warrant further study in FD.