Atypical Femoral Fractures

Introduction We posted our first “Case Connections” article about bisphosphonate-related atypical femoral fractures (AFFs) one year ago. Since then, JBJS Case Connector has published three additional case reports on the same topic, suggesting that it’s time for a revisit. These three recent cases demonstrate that AFFs can occur despite prophylactic intramedullary (IM) nailing of an at-risk femur, that AFFs can present as periprosthetic fractures, and that men taking bisphosphonates—not just women—can experience AFFs. Prophylactic Nailing: No Guarantee Patients who develop one AFF have a 28% to 65% chance of developing a similar fracture on the other side1-3, and prophylactic intramedullary nailing of the contralateral femur has proven to be an effective preventive measure. However, in the July 8, 2015, JBJS Case Connector,Schemitsch et al. described the case of a forty-three-year-old woman who sustained a complete fracture of a prophylactically nailed femur seven months after the preventive procedure. The patient had a history of premature idiopathic menopause and was taking bisphosphonates when she initially presented with a painful left thigh. Radiographs made at that time revealed lateral cortical hypertrophy of both femora and a cortical defect in the left femur. She declined prophylactic surgical intervention but was taken off bisphosphonates and switched to hormone replacement therapy. Ten months later, she presented after falling from a standing height and was found to have a left-side AFF. After closed reduction, surgeons inserted a locked reconstruction-type nail in the left femur, which healed uneventfully. Radiographs of the right femur revealed a cortical breach in the distal third of the bone. This time, the patient agreed to and subsequently underwent prophylactic nailing of the right femur (Fig. 1). Two weeks after the prophylactic procedure, she reported minimal pain and gradually increasing activity.Fig. 1: Lateral radiograph of the right femur, made immediately after uncomplicated prophylactic intramedullary nailing.The right-side recovery continued uneventfully for seven months, at which point the patient felt a sudden snap in the right thigh while standing. Radiographs revealed a complete fracture around the intramedullary nail at the site of the previously observed cortical stress lesion (Fig. 2). Surgeons treated that fracture with a 4.5-mm compression plate with screws placed around the nail, adding iliac-crest bone graft to the fracture site. Recovery after this procedure was uneventful, and the patient returned to work and normal activities six months postoperatively. Radiographs made two years after surgery revealed osseous union of the right femoral fracture.Fig. 2: Lateral radiograph made seven months after prophylactic nailing, revealing a complete fracture of the femur at the site of the previously seen radiolucent line.Schemitsch et al. noted that this case “emphasizes that careful attention to the technical details of nail insertion is critical to success, even with prophylactic nailing.” Observing that their patient’s femoral stress reaction was more distal than is typically seen, the authors surmised that using a larger nail, inserting it more distally, and/or using two locking screws rather than one might have prevented this rare complication. However, they also noted that medullary canals in patients with bisphosphonate-induced bone abnormalities are often narrow and that the use of a larger-diameter nail could have resulted in iatrogenic injury. The authors also commented that while full weight-bearing is their standard postoperative regimen following locked IM nailing, “it is possible that a period of limited weight-bearing may be advantageous in patients with impending or completed atypical femoral fractures.” Delayed Diagnosis of Vancouver Type-C Fracture In the May 27, 2015, JBJS Case Connector,Chen et al. reported on an AFF that occurred about halfway between the distal end of a prosthetic femoral stem and the knee joint. The patient, a sixty-nine-year-old woman with a history of total hip arthroplasty (THA) and bisphosphonate use, initially presented with pain in the right thigh and knee. Hip and knee imaging revealed that the previously implanted hip components were well fixed and that there was moderate medial and patellofemoral arthritis. The patient underwent physical therapy following a diagnosis of knee osteoarthritis and lumbar spondylosis. Several months later, the patient sustained a low-energy fall, and radiographs made at that time revealed an incomplete Vancouver type-C transverse fracture with medial oblique propagation. Three months after undergoing open reduction and internal fixation with a ten-hole femoral plate, she continued to experience deep thigh pain, and radiographs divulged no notable callus formation. By seven months, continued fracture propagation had led to a procurvatum deformity. Bisphosphonates were discontinued at nine months, but radiographs at eleven months showed further deformity and persistent fracture nonunion, indicating the need for revision. During revision, surgeons noted gross motion at the fracture site and only medial evidence of union. The revision construct consisted of a sixteen-hole contoured condylar locking plate applied using a compression technique. Surgeons supplemented the fixation with demineralized bone-matrix putty and rhBMP-2. Twelve months after revision, the patient was walking with full weight-bearing and radiographs showed fracture union. Based on this case, Chen et al. recommended that surgeons obtain images of the entire femur in THA patients who have been receiving long-term bisphosphonate therapy to avoid missing fractures distal to the prosthetic stem. They also encouraged surgeons with patients in similar situations to discuss the benefits of discontinuing bisphosphonates earlier than was done in this case. Finally, the authors reminded orthopaedists about the likelihood of a longer time to fracture union and an increased risk of prosthetic failure in patients taking bisphosphonates. AFFs Happen in Men, Too Because the vast majority of people taking bisphosphonates are women, most of the people who experience an AFF are also women. But in the April 22, 2015, JBJS Case Connector,Román et al. described the case of a seventy-two-year-old man with multiple comorbidities who sustained two AFFs (one on each side) within a twenty-two-month period, both associated with low-energy trauma. The patient had been taking alendronate weekly for eleven years to treat osteoporosis induced by long-term use of inhaled corticosteroids, but surprisingly he reported no prodromal symptoms prior to either fracture, nor had any femoral radiographs been made before the incidents. The first fracture consolidated five months after IM nailing, and, with the help of teriparatide, the slower-to-heal second fracture consolidated seven months after similar surgical treatment. The case described by Román et al. reminds us that prodromal thigh pain is not always reported by individuals who are ultimately diagnosed with an AFF. Diagnostically, the authors recommended MRI “when radiographic results are normal or inconclusive for patients treated with bisphosphonates who present with an ache in the upper thigh.” Their indications for prophylactic nailing of incomplete fractures included moderate to severe thigh pain, pain or a fracture line that persists after three months of conservative treatment, or fracture progression that is identified by serial monitoring. Finally, they cited a “consensus” for a “drug holiday” from bisphosphonates after five years in patients who demonstrate adequate bone mineral density. Conclusion While prophylactic nailing of an at-risk femur is not an ironclad guarantee against AFFs, surgeons can reduce the chance of such fractures by paying extra attention to the technical details of nail insertion and recommending a modified rehab protocol that initially limits weight-bearing. In symptomatic patients who have been on long-term bisphosphonate therapy, imaging studies should include the entire femur, and consideration should be given to imaging the contralateral femur. Discontinuation of bisphosphonates should be considered if the patient’s bone mineral density is adequate. In addition, the femora of men on long-term bisphosphonate therapy should be as closely monitored as those of women taking osteoclast-inhibiting drugs. It is estimated that one AFF occurs for every 100 osteoporotic hip fractures that are prevented by bisphosphonates. Despite these new cases, the benefits of bisphosphonates clearly continue to far outweigh the risks. We will continue to monitor the progress in diagnosis, treatment, and prevention of atypical femoral fractures as our JBJS Case Connector database expands.

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