Propagation of bisphosphonate-related femoral stress fractures despite femoral nailing: a cautionary tale from 2 cases.

We report 2 cases of atypical femoral fracture displacement despite treatment with intramedullary (IM) nailing. Both patients had received more than 3 years of bisphosphonates. One patient had prophylactic fixation of an atypical femur fracture due to intractable pain. The other had undergone nailing previously for a traumatic shaft fracture. The patient then received bisphosphonate later and sustained an atypical fracture with the nail in place. Both femoral nails were slotted, cannulated stainless steel piriformis entry designs. These 2 cases are among the first reported failures of IM fixation in preventing displacement of a bisphosphonate stress fracture. We advice caution when using slotted nails in prophylaxis of atypical femur fractures because of its significantly reduced torsional stiffness compared to modern nonopen sectioned nails.