Incomplete Periprosthetic Atypical Femoral Fracture With Concomitant Hip and Knee Arthroplasties: A Case Report

We present a case of an incomplete periprosthetic femoral fracture at the mid-distal third of the femoral stem after 11 months of bisphosphonate use. It is 1 of 4 cases of mid-distal periprosthetic atypical femoral fractures (PAFFs) found in our literature review. She was treated with protected weight-bearing, cessation of bisphosphonates, and teriparatide. Eighteen months after diagnosis, follow-up radiographs showed a bridging callus and reduction of a transverse fracture line.

The incomplete PAFF was contributed by both decreased bone turnover from bisphosphonate use and increased mechanical stress at the lateral femoral cortex. Her previous left bipolar hemiarthroplasty and subsequent Total Knee Arthroplasty shifted the mechanical alignment medially, hence increasing tensile stress.