Long-term results of the anterior cervical spondylodesis.

From 1974 to 1992, anterior cervical spondylodesis was performed in 163 patients of cervical spondylotic myelopathy, cervical spondylotic radiculopathy, traumatic spinal injury, ossification of the posterior longitudinal ligament, or cervical spondylitis. Forty-five of these patients were followed for more than 4 years. To analyze the long-term results of anterior cervical spondylodesis, a radiological examination was performed in these 45 patients and magnetic resonance imaging was conducted in 41 of them. Postoperative spondylotic changes were observed radiologically in 23 (51.1%) of the 45 patients. Anterior bony spur was more frequently observed than posterior bony spur in these postoperative spondylotic changes. Postoperative canal stenosis caused by the bulging of the discs and the ligamentum flavum was frequently demonstrated with hypo- or isointense signal on T2-weighted images by magnetic resonance imaging in patients followed long term after surgery and in patients with malalignment of the cervical spine due to kyphosis of the fused vertebrae and multisegmental fusion. Neurological improvement was less in patients with bulge of the discs and the ligamentum flavum seen in magnetic resonance imaging than in patients without it. The bulge of the ligamentum flavum was histopathologically defined as hypertrophy of the ligament.