CSEM2404 - CSEM Resident Oral Abstract Presentations - Atypically Typical: Incidental Atypical Femoral Fractures Found After Fragility Hip Fracture

Abstract:

Background: Atypical femoral fracture (AFF) is a rare side effect of anti-resorptive therapy. Risk of AFF increases with duration of continuous therapy. If an AFF is diagnosed, it is imperative to perform a contralateral femur x-ray, since AFFs are bilateral in up to 50% of cases.

Case presentation: After falling from standing height, an 81-year-old woman sustained a left-sided intertrochanteric hip fracture treated with a cephalomedullary nail. Pre-operative x-ray reported a subtle cortical bump involving the lateral proximal shaft. This was not actioned upon until seen by Endocrinology 1 year later, where we noted that she was on alendronate for 6 years followed by denosumab for 2 years. Radiograph of the right femur demonstrated focal cortical thickening along the lateral aspect of mid-shaft with a visible lucent line, consistent with impending AFF. She was admitted to Orthopedics for treatment with right femoral intramedullary nail.

Discussion: This is a unique presentation of incidental AFFs on imaging for typical hip fracture. It highlights gaps in management of AFF. In this case, contralateral femur x-ray was not obtained at the time the left-sided AFF was detected, increasing risk of complete right-sided AFF. There is presently no treatment guideline for AFF. Teriparatide is used to promote AFF healing. However, as teriparatide has theoretical risk of malignancy, and she had a history of lung cancer, she declined. After bilateral intramedullary nailing for AFFs, risk of AFF at other skeletal sites is weighed against risk of osteoporotic fractures. In this case, denosumab resumption was advised.