Late-onset progressive myelopathy, years after odontoid fracture, is considered a rarity. Sixteen patients with diagnosis of their odontoid fractures delayed from four months to 45 years have been studied and treated. Three had forgotten about the injury and, in the rest, the significance had been minimized by their clinicians. Fifteen patients had characteristic C-2 nerve root pain and 10 had noted weak hands and walking difficulties. Fifteen patients had Type II fractures, which were mobile in 11; hypertrophic pseudoarthrosis was marked in two. In seven patients it was confirmed at surgery that all or part of the transverse ligament was interposed in the fracture. Transoral surgery, combined with a variety of posterior fusion techniques, has allowed cord decompression, an understanding of the pathomechanics, and sound posterior bone fusion with arrest of the myelopathic condition. Measurements of craniovertebral angles and cord cross-sectional area in this series revealed a rough correlation, but the most striking relationship was between length of delay in diagnosis and diminished cord area in both non-union and malunion, suggesting a progressive injury mechanism. It is proposed that late myelopathy following odontoid fracture may be more common than hitherto believed and should be considered in the evaluation of patients with cervical spondylosis. The condition may be progressive. Finally, non-union may be due to interposition of the transverse ligament.

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