Atraumatic subtrochanteric femoral fracture nonunion with suspected impairment of bone quality despite preserved bone mineral density: a case report

Fracture nonunion is a multifactorial condition involving both mechanical and biological factors. We report a case of atraumatic subtrochanteric femoral fracture nonunion in a patient with relatively preserved bone mineral density (BMD) and biochemical findings suggestive of possible impairment of bone material properties. A 64-year-old man developed a subtrochanteric femoral fracture without an identifiable traumatic event and underwent intramedullary nailing. Despite dynamization, symptomatic nonunion persisted 11 months after surgery. Metabolic evaluation identified chronic kidney disease and vitamin D deficiency. Femoral BMD was 0.854 g/cm 2 and lumbar spine BMD was 1.599 g/cm 2 . Plasma homocysteine and urinary pentosidine were markedly elevated at 20.1 nmol/mL and 0.2101 μg/mg·Cre, respectively. These surrogate biomarkers raised suspicion of impaired bone material properties but did not directly demonstrate impaired bone quality. The local mechanical environment was not quantitatively assessed, and mechanical inadequacy could not be excluded. Revision surgery was considered; however, because of the patient’s comorbidities and the anticipated invasiveness of surgery, an initial individualized strategy using concurrent daily teriparatide and low-intensity pulsed ultrasound was selected with close monitoring. Radiographic union was observed approximately 5 months after treatment initiation and remained maintained at 13-year follow-up. Because both interventions were initiated concurrently, their individual and combined contributions to fracture healing could not be determined. This case highlights the importance of assessing both mechanical and biological factors in established nonunion, particularly when an atraumatic fracture occurs despite relatively preserved BMD. Revision surgery with mechanical optimization remains the standard of care. The observed union does not establish the efficacy of teriparatide, low-intensity pulsed ultrasound, or their combination, and the management used in this patient should be interpreted as an individualized strategy rather than a validated alternative to revision surgery.