Bilateral Atypical Femoral Fracture in a Bisphosphonate-Naïve Patient with Prior Long-Term Denosumab Therapy: A Case Report of the Management Strategy and a Literature Review

Abstract

The benefits of denosumab as an antiresorptive therapy and in reducing fragility fractures are well documented. However, its association with atypical femur fractures (AFFs), especially in the absence of prior bisphosphonate use, remains poorly understood and warrants further investigation. This case report presents a rare instance of bilateral AFFs in a 78-year-old bisphosphonate-naïve patient with a history of long-term denosumab therapy for previous metastatic breast cancer. Management involved intramedullary nail fixation after initial presentation with a unilateral AFF and a recommendation to cease denosumab therapy. However, the patient subsequently experienced a contralateral periprosthetic AFF below a total hip implant 5 months thereafter and was treated with open reduction internal fixation. This case report highlights the critical need for orthopedic surgeons to maintain a high level of suspicion and vigilance in screening for impending AFFs, especially in patients with a prolonged history of denosumab therapy without prior bisphosphonate use. Furthermore, the growing report of such cases emphasizes the urgent need for comprehensive research aimed at refining treatment protocols that balance the therapeutic benefits of denosumab and its associated risks of AFFs.

Keywords: atypical femoral fracture; bisphosphonate; bone antiresorptive therapy; denosumab; subtrochanteric fracture.

Figure 1

Radiographs demonstrating a transverse left subtrochanteric femur fracture with a medial spike in a 78-year-old female patient.

Figure 2

Radiographs of contralateral right femur demonstrating lateral cortical thickening distal to stem of femoral implant in 78-year-old female patient.

Figure 3

(A)—Three-month postoperative radiographs of left femur demonstrating delayed healing of subtrochanteric fracture with stable intramedullary nail fixation (top). (B)—Radiographs of the contralateral femur demonstrating lateral cortical beaking and thickening distal to the previous hip prosthesis (bottom).

Figure 4

Radiographs demonstrating an acute atypical mid-shaft right periprosthetic femur fracture distal to the femoral stem (Vancouver Type C).

Figure 5

Immediate postoperative radiographs following open reduction and internal fixation with a lateral periprosthetic femoral plate.

Figure 6

Most recent follow-up radiographs demonstrating healing of both femur fractures with no evidence of hardware failure: (A)—approximately 10 months following left femur nonunion surgery (top) and (B)—2 years after right atypical periprosthetic femoral shaft fixation (bottom).