Case Report and Literature Review of Periprosthetic Atypical Femoral Fractures After Total Hip Arthroplasty.

: We describe a case of periprosthetic femoral fracture with 5 major features of an atypical femoral fracture (AFF) and localized cortical thickening at the fracture site, which is characteristic of an AFF. An 81-year-old female patient had undergone cementless total hip arthroplasty for a right femoral neck fracture at the age of 66, and had been taking oral alendronate since then. At the age of 79, she developed spontaneous right thigh pain. Radiographs showed lateral cortical thickening and pedestal formation around the end of the femoral component. She was advised to discontinue oral alendronate and change to eldecalcitol. At the age of 81, she developed sudden severe pain when standing up from a seated position and was not able to walk. Radiographs showed a periprosthetic femoral fracture with 5 major features of AFF at the site of localized cortical thickening. We diagnosed a Vancouver type B1 periprosthetic femoral fracture. She underwent open reduction and internal fixation (ORIF) with an NCB® Periprosthetic Femur Plate System with cable grips. Daily subcutaneous injection of teriparatide and low intensity pulsed ultrasound therapy were performed to stimulate bone healing. She was able to walk without assistance at 4 months after ORIF. Radiographs showed adequate bridging callus and a disappearing fracture line. This case was diagnosed as a periprosthetic atypical femoral fracture (PAFF), because a periprosthetic fracture is excluded from the definition of AFF. Similar to AFF, PAFF exhibits poor clinical outcomes. The approach to treating PAFF should be decided after considering the pathogenesis.