• Ken Ishii, Kazuhiro Chiba, Hirofumi Maruiwa, Masaya Nakamura, Morio Matsumoto, and Yoshiaki Toyama.
• Department of Orthopaedic Surgery, School of Medicine, Keio University, Tokyo, Japan. ishii-km@sc.itc.keio.ac.jp
• J Neurosurg Spine. 2006 Nov 1; 5 (5): 385-91.

ObjectThe authors conducted a study to assess the correlation between radiological features and clinical courses in patients with chronic atlantoaxial rotatory fixation (AARF) and to determine diagnostic imaging signs for predicting prognosis.MethodsThere were 24 patients (eight boys and 16 girls) whose mean age was 7.8 years (range 4-14 years) and in whom AARF was diagnosed. The mean follow-up duration was 3.7 years (range 5 weeks-12 years). There were two groups of patients: 15 patients who visited the hospital less than 8 weeks after symptom (torticollis) onset comprised the acute group, and nine patients in whom the diagnosis of AARF was established later than 3 months after symptom onset comprised the chronic group. The chronic group was divided into two subgroups: those in whom the closed reduction could be achieved and those in whom it could not. Clinical data and radiographic studies, including plain radiographs and plain and three-dimensional (3D) computed tomography (CT) reconstructions, were reviewed retrospectively. A deformity of the superior C-2 facet joint was frequently observed in the group of patients with chronic AARF (p < 0.0001). This sign represented a risk factor for recurrent dislocation (p = 0.0003, Fisher exact test). Prominent lateral inclination of C-1 was an impeding factor for reduction of chronic AARF (p < 0.0001, analysis of variance with Fisher post hoc test). Greater than 20 degrees of lateral inclination of the atlas indicated an irreducible subluxation (p = 0.0023, Fisher exact test).ConclusionsBoth facet joint deformity and lateral inclination observed on 3D CT reconstructions can be useful signs to predict the prognosis and the treatment of choice in patients with chronic AARFs.

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