Risk factors of fracture stability and osseous union of Type II odontoid fractures

To evaluate fracture stability rates after conservative treatment and osseous union rates after surgery in patients with Type II odontoid fractures, and to identify clinical and radiologic risk factors associated with these outcomes. The medical records and radiologic data of patients admitted for odontoid fractures at two centers from January 2006 to December 2023 were retrospectively reviewed. Patients with transverse atlas ligament injury, chronic odontoid fractures, or infectious or pathologic fractures were excluded. A total of 111 patients were included. Age, sex, and bone mineral density (BMD) were evaluated as clinical factors. Sagittal tilt (ST), Sagittal displacement (SD), gap of the fracture line (GF), and coronal tilt (CoT) were studied as radiologic risk factors. Fracture stability after 6 weeks of conservative treatment and osseous union at one year were evaluated. Mean patient age was 61.1 years, and 78 of the 111 patients were men. Mean follow-up was 25.2 months. Osteoporosis accounted for 30% of cases. The rate of fracture stability after conservative treatment was 32%. Seventy-five patients underwent anterior odontoid screw fixation, and nine of these patients failed to achieve osseous union. The union rate of Type II odontoid fracture after surgery at 12 months was 88%. Osteoporosis was a significant risk factor for both fracture stability and osseous union of Type II odontoid fracture. An SD > 2 mm and ST > 6° were risk factors for fracture stability after conservative treatment. In addition, an age greater than 70 years was a risk factor for osseous union after surgery. Osteoporosis and radiologic measurements (ST and SD) were found to be significant risk factors for fracture stability after conservative treatment. Osteoporosis and old age were associated with osseous union after surgery. Level of evidence III. Retrospective cohort study.