Periprosthetic fracture resembling atypical femoral fracture after fixation with retrograde intramedullary nail in elderly women: A report of two cases

Abstract

Background/Aim: The number of individuals diagnosed with and requiring medical treatment for osteoporosis continues to increase due to global population aging and the high awareness of osteoporosis. Bone-modifying agents (BMAs) including bisphosphonate and denosumab are widely used for osteoporosis, and atypical femoral fracture (AFF) is also gaining attention as a severe potential side effect of long-term BMA treatment. The definition of AFF excludes periprosthetic femoral fracture; here, we describe two cases of a periprosthetic femoral fracture that resembled AFF. Case Report: The fractures occurred at the proximal tip of the retrograde femoral nail after an internal fixation for a distal femoral shaft fracture in elderly Japanese women. Each woman had been treated with bisphosphonate therapy for >2 years and had continued the bisphosphonate after undergoing surgery for a distal femoral shaft fracture. Each patient had noticed thigh pain before falling down, and plain radiographs showed a short oblique or transverse fracture with medial spike and localized periosteal reaction of the lateral cortex in each case. The fractures were re-fixed with an antegrade intramedullary nail, and bone union was achieved at >1 year after the second operation. Although these two cases were classified as periprosthetic fractures, they fulfilled the characteristics of AFF. Conclusion: Physicians should conduct a thorough interview of patients with a history of BMA treatment in order to correctly diagnose periprosthetic fractures that resemble AFFs, and they should be aware that symptomatic fractures can be prevented by prophylactic fixation. The discontinuance of BMA therapy and the introduction of another drug such as teriparatide may lead to faster healing of surgically treated AFFs.