Atypical periprosthetic femoral fractures associated with bisphosphonates

Benefits for osteoporotic patients 'probably outweigh risk'

Atypical femoral fractures (AFFs) have been linked to bisphosphonate use, and atypical periprosthetic femoral fractures should be considered a subgroup of those fractures, researchers from Canada report.

X-ray of pelvis

The American Society of Bone and Mineral Research Task Force criteria for identifying AFFs currently exclude periprosthetic femoral fractures (PFFs), and the prevalence of atypical periprosthetic femoral fractures in patients with hip and knee arthroplasties is currently unknown.

Dr Etienne Belzile and colleagues from Centre Hospitalier Universitaire de Quebec-Universite Laval investigated the prevalence of atypical fractures near hip and knee prostheses in their retrospective study of 133 patients with PFFs.

Atypical PFFs accounted for 8.3% of all PFFs, the team reports in the Journal of Bone and Mineral Research.

Eight of the 11 patients with atypical PFFs (72.7%) had been exposed to bisphosphonates, compared with only 30.3% of patients with other PFFs.

The risk of atypical periprosthetic femoral fractures was significantly higher among alendronate users than among risedronate users.

Significantly associated with these atypical fractures were transverse fractures, periosteal thickening of the lateral cortex at the fracture, unicortical fractures and prodromal symptoms.

"Bisphosphonate exposure is a major risk factor (for atypical PFFs), but the benefits for osteoporotic patients probably outweigh the risk," the researchers conclude.

"Clinicians should be aware of this new entity in their approach to PFFs. Optimal medical and surgical management must still be clarified with further studies."

Dr Juan de Dios Robinson, from Queen Elizabeth II Health Sciences Center at Dalhousie University in Halifax, Canada, told Reuters Health, "AFFs as a whole are a relatively rare entity, and [atypical PFFs], being a subset of this presentation, by definition will be even a smaller number.

"However, clinicians must be alert to the possibility of this diagnosis when a patient with a history of bisphosphonate use presents with thigh pain and no signs of loosening.

"In our opinion, [atypical PFFs] are a subset of AFFs and should be included in the definition of the ABMR task force criteria," said Dr Robinson, who was not involved in the new study.

He added that a bone scan was a useful investigation in detecting developing atypical fractures.

“On several occasions, we realised that a bone scan elicited the precise site where subsequently the features of an atypical fracture developed.

"We also feel that when this pathology is elicited prior to a complete fracture, a serious conversation must be had with the patient regarding prophylactic fixation and other measures to prevent completion of the fracture, including stopping the bisphosphonates and considering teriparatide."

More information: Journal of Bone and Mineral Research 2018