Severity of osteogenesis imperfecta associated with atypical femur fractures

Bisphosphonate treatment history was not associated with atypical femur fractures among patients with osteogenesis imperfecta.

Frank Rauch

Occurrence of atypical femur fractures among patients with osteogenesis imperfecta was related to the severity of the patient’s disease and not to any bisphosphonate treatment the patient received, according to study results.

“We did not find an increased incidence of atypical femur fractures in children with [osteogenesis imperfecta] OI treated with bisphosphonates,” Frank Rauch, MD, professor of pediatrics at Shriners Hospital for Children in Montreal, told Orthopedics Today.

Rauch and his colleagues retrospectively analyzed 119 children with OI who had 166 femur fractures who did not undergo intramedullary rodding procedures. Of the fractures analyzed, researchers separately evaluated 90 children with 130 fractures that occurred in femurs that had pre-existing deformities, since bone deformity is a typical cause of fracture in patients with OI.

Results showed 11 of 36 fractures that occurred in non-deformed femurs occurred during bisphosphonate treatment, of which 27% resembled atypical femur fractures. In the study, researchers noted 22% of 25 femur fractures that occurred in the absence of prior bisphosphonate treatment resembled atypical femur fractures.

According to the logistic regression analysis, the occurrence of atypical femur fractures was not associated with bisphosphonate treatment history. It was, however, strongly associated with the presence of moderate to severe OI. Among patients with deformed femurs, researchers also found an association between a transverse fracture pattern and a moderate to severe OI phenotype, but this was not related to bisphosphonate treatment.

“The clinical implication is that atypical femur fractures are a theoretical side effect of bisphosphonate treatment and the fact that we did not find a side effect is basically one concern less,” Rauch said. “It just means that, from our point of view, you do not need to stop the treatment because you fear these atypical femur fractures,” he said.

First research effort

This is the first study to look at a large population of patients with OI and provide statistics on whether “this type of X-ray finding is more frequent,” according to Rauch. These results also contradict previous reports from case studies that identified peculiar fractures patterns in femurs of patients with OI as atypical femur fractures caused by bisphosphonate treatments, he noted.

“In children who have osteogenesis imperfecta there are a lot of fractures that look like atypical femur fractures in adults with osteoporosis, but the reason is probably their underlying genetic defect and it is not the bisphosphonate treatment,” he said. “So, that may also give some ideas about the causes of atypical femur fractures in adults with postmenopausal osteoporosis, in particular.”

The next step in research is to perform a prospective study using information from a NIH network that follows patients with OI at all major centers in North America, Rauch said,

“It will be easier to collect information on [OI] prospectively because we have way more patients that we are following systematically,” he said. “I think that will be the logical next step to confirm what we found with the retrospective study in a prospective study.” – by Casey Tingle

Reference:

Trejo P, et al. J Bone Miner Res. 2016;doi:10.1002/ jbmr.3071.

For more information:

Frank Rauch, MD, can be reached at Shriners Hospital for Children, 1003 Boulevard Decarie, Montreal, Quebec, Canada H4A 0A9; email: frauch@shriners.mcgill.ca.

Disclosure: Rauch reports no relevant financial disclosures.