PURPOSE

To define the prevalence, characteristics, and treatment approach for proximal junction failure secondary to odontoid fractures in patients with prior C2-pelvis posterior instrumented fusions (PSF).

METHODS

A single institution's database was queried for multi-level fusions (6+ levels), including a cervical component. Posterior instrumentation from C2-pelvis and minimum 6-month follow-up was inclusion criteria. Patients who sustained dens fractures were identified; each fracture was subdivided based on Anderson & D'Alonzo and Grauer's classifications. Comparisons between the groups were performed using Chi-square and T tests.

RESULTS

80 patients (71.3% female; average age 68.1 ± 8.1 years; 45.0% osteoporosis) were included. Average follow-up was 59.8 ± 42.7 months. Six patients (7.5%) suffered an odontoid fracture post-operatively. Cause of fracture in all patients was a mechanical fall. Average time to fracture was 23 ± 23.1 months. Average follow-up after initiation of fracture management was 5.84 ± 4 years (minimum 1 year). Three patients sustained type IIA fractures one of which had a concomitant unilateral C2 pars fracture. Three patients sustained comminuted type III fractures with concomitant unilateral C2 pars fractures. Initial treatment included operative care in 2 patients, and an attempt at non-operative care in 4. Non-operative care failed in 75% of patients who ultimately required revision with proximal extension. All patients with a concomitant pars fracture had failure of non-operative care. Patients with an intact pars were more stable, but 50% required revision for pain.

CONCLUSIONS

In this 11-year experience at a single institution, the prevalence of odontoid fractures above a C2-pelvis PSF was 7.5%. Fracture morphology varied, but 50% were complex, comminuted C2 body fractures with concomitant pars fractures. While nonoperative management may be suitable for type II fractures with simple patterns, more complex and unstable fractures likely benefit from upfront surgical intervention to prevent fracture displacement and neural compression. As all fractures occurred secondary to a mechanical fall, inpatient and community measures aimed to minimize risk and prevent mechanical falls would be beneficial in this high-risk group.