Awareness of Stress Concentration Points for Prevention and Management of Periprosthetic Fractures Following Plate Installation Reinforcement: A Case Report

INTRODUCTION: In an aging society, the incidence of periprosthetic fractures will increase owing to the increasing number of patients undergoing joint replacement surgery. We experienced a case of recurrent periprosthetic fracture in a patient who had undergone ipsilateral hip bipolar hemiarthroplasty (BHA) and total knee arthroplasty. Based on our experience, we discuss the treatment strategy for periprosthetic fractures in patients at a high risk of fall. CASE REPORT: An 84-year-old woman, who had undergone total knee arthroplasty 9 years ago and ipsilateral hip BHA 2 years ago, sustained a knee condylar fracture (Su classification type III) due to fall. This knee periprosthetic fracture posed a challenge for osteosynthesis; therefore, revision total knee arthroplasty was performed using a hinge-type prosthesis. During this surgery, we installed a reinforcement plate on the femoral shaft to prevent fractures because of the short stem tip distance between the hip and knee prosthesis (53 mm). The procedure was successful, and the patient regained her walking ability. However, 6 months after surgery, the patient sustained a hip periprosthetic fracture (Vancouver type B2) due to a fall, despite precautionary plate installation. In case of hip stem insertion, the stress caused by fall is concentrated on the infratrochanteric region, as reflected in her fracture site. From a mechanical perspective, this fracture was not accidental. The plate reinforcement procedure may have been inadequate because the top of the plate was located at the infratrochanteric region. CONCLUSION: Periprosthetic fractures may occur despite the installation of a plate for fracture prevention. With a total hip arthroplasty or hip BHA stem inserted, a fall could result in a subtrochanteric fracture.