Paul Klimo Jr., Valerie Coon and Douglas Brockmeyer
Os odontoideum was first described in the late 1880s and still remains a mystery in many respects. The genesis of os odontoideum is thought to be prior bone injury to the odontoid, but a developmental cause probably also exists. The spectrum of presentation is striking and ranges from patients who are asymptomatic or have only neck pain to those with acute quadriplegia, chronic myelopathy, or even sudden death. By definition, the presence of an os odontoideum renders the C1–2 region unstable, even under physiological loads in some patients. The consequences of this instability are exemplified by numerous cases in the literature in which a patient with os odontoideum has suffered a spinal cord injury after minor trauma. Although there is little debate that patients with os odontoideum and clinical or radiographic evidence of neurological injury or spinal cord compression should undergo surgery, the dispute continues regarding the care of asymptomatic patients whose os odontoideum is discovered incidentally. The authors' clinical experience leads them to believe that certain subgroups of asymptomatic patients should be strongly considered for surgery. These subgroups include those who are young, have anatomy favorable for surgical intervention, and show evidence of instability on flexion-extension cervical spine x-rays. This recommendation is bolstered by the fact that surgical fusion of the C1–2 region has evolved greatly and can now be done with considerable safety and success. When atlantoaxial instrumentation is used, fusion rates for os odontoideum should approach 100%.
Paul Klimo Jr., Peter Kan, Ganesh Rao, Ronald Apfelbaum and Douglas Brockmeyer
The most contentious issue in the management of os odontoideum surrounds the decision to attempt atlantoaxial fusion in patients with asymptomatic lesions. The authors examined the clinical presentation and outcome in patients with os odontoideum who underwent surgical stabilization, with an emphasis on 3 patients who initially received conservative treatment and suffered delayed neurological injury.
Seventy-eight patients (mean age 20.5 years; median 15 years) were identified in a 17-year retrospective review. The median follow-up period was 14 months (range 1–115 months). Neck pain was the most common symptom (64%), and 56% of patients presented after traumatic injury. Eighteen patients had neurological signs or symptoms at presentation, and an additional 15 had a history of intermittent or prior neurological symptoms. Fifteen patients had undergone ≥ 1 attempt at atlantoaxial fusion elsewhere.
Seventy-seven patients underwent posterior fusion and rigid screw fixation combined with a graft/wire construct: 75 had C1–2 fusion and 2 had occipitocervical fusion. One patient had an odontoid screw placed. Fusion was achieved in all patients at a median of 4.8 months (range 2–17 months). Approximately 90% of patients had resolution or improvement of their neck pain or neurological symptoms.
The authors believe that patients with os odontoideum are at risk for future spinal cord compromise. Forty-four percent of our patients had myelopathic symptoms at referral, and 3 had significant neurological deterioration when a known os odontoideum was left untreated. This risk of late neurological deterioration should be considered when counseling patients. Stabilization using internal screw fixation techniques resulted in 100% fusion, whereas 15% of patients had previously undergone unsuccessful wire and external bracing attempts.