Abstract

An 81-year-old woman with osteoporosis presented in April 2024 with recurrent right thigh pain, 8 years after prophylactic intramedullary nailing for an incomplete atypical femoral fracture (AFF) in February 2016. She had a history of bisphosphonate use for approximately 10 years followed by a 5-year drug holiday and three ibandronate infusions before the index fracture in 2016; after a subsequent 4-year antiresorptive-free interval, bisphosphonate therapy was resumed in 2020–2021 following a new vertebral compression fracture. Plain radiographs in 2024 showed recurrent lateral cortical thickening and a transverse radiolucent line at the same site as the previous lesion, with intact hardware. Bone scintigraphy confirmed intense uptake consistent with a recurrent stress reaction. Laboratory testing showed markedly suppressed bone turnover markers, with a serum β-isomerized C-terminal telopeptide of type I collagen (β-CTX) level of 0.048 ng/mL, below the lower limit of the reference range (0.112 ng/mL). The lesion healed during conservative management consisting of bisphosphonate discontinuation, calcium and vitamin D supplementation, retained mechanical stabilization, and a 4-month course of off-label teriparatide. The independent contribution of teriparatide cannot be determined from this single case. This case highlights the rare phenomenon of same-site incomplete AFF recurrence long after prophylactic fixation in association with bisphosphonate resumption and describes successful conservative healing with short-term teriparatide in the presence of preexisting hardware. Level of evidence: V.

• Keywords: Femoral fractures; Diphosphonates; Stress fractures; Intramedullary fracture fixation; Case reports