PMC4300897_01
Preoperative X-ray and CT scan in case 1. On plain radiographs, the cervical spine showed malalignment at the atlantoaxial level with torticollar deformity. Plain CT showed not only sagittal but also axial dislocation of the atlantoaxial joint with os odontoideum. (a-p, anteroposterior; 3D, 3-dimensional.)
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Plain computed tomography (CT) showed os odontoideum, and 3-dimensional CT clearly depicted not only sagittal but also axial dislocation of the atlantoaxial joint complex (Fig. 1).
Preoperative magnetic resonance image (T1WI: T1-weighted image, T2WI: T2-weighted image) in case 1. The spinal cord snaked through into the spinal canal, but high-intensity change of the spinal cord on the T2WI was not observed.
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The spinal cord snaked through into the spinal canal, but high-intensity change of the spinal cord on the T2-weighted image was not observed on magnetic resonance imaging (Fig. 2).
Morphologic analysis of C2 pedicles by CT imaging in case 1. Insertion of pedicle screws was judged dangerous on both sides by CT imaging. (lt, left; rt, right.)
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Morphologic analysis of the C2 pedicles by CT imaging techniques indicated that insertion of pedicle screws was judged dangerous on both sides (Fig. 3).
Postoperative X-ray (obtained 1 year 3 months after surgery) and CT scan (obtained 4 weeks after surgery) in case 1. Alignment of the cervical spine had improved, and the positions of the bilateral C2 laminar screws were correct. (a-p, anteroposterior.)
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Posterior occipito-axial fixation with bilateral C2 laminar screws (Vertex Max; Medtronic, Memphis, Tennessee) and a decompressive procedure by resection of the C1 posterior arch were then performed (Fig. 4).
PMC4300897_02
Preoperative X-ray and CT scan in case 2. On dynamic radiographs, marked instability at the atlantoaxial joint was observed. Plain CT showed atlantoaxial subluxation with os odontoideum. (3D, 3-dimensional.)
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Plain CT showed atlantoaxial subluxation with os odontoideum (Fig. 5).
Preoperative magnetic resonance image (T1WI: T1-weighted image, T2WI: T2-weighted image) in case 2. Severe spinal canal stenosis accompanied by high-intensity change of the spinal cord on the T2WI was clearly observed at the atlantoaxial level.
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The spinal canal had a severe stenosis at the atlantoaxial level, and high-intensity change of the spinal cord on the T2-weighted image was clearly observed on magnetic resonance imaging (Fig. 6).
Morphologic analysis of C2 pedicles by CT imaging in case 2. Insertion of pedicle screws was judged dangerous on the left side by CT imaging. (lt, left; rt, right.)
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Morphologic analysis of the C2 pedicles by CT imaging techniques indicated that insertion of pedicle screws was judged dangerous on the left side (Fig. 7).
Postoperative X-ray (obtained 1 year 6 months after surgery) and CT scan (obtained 1 week after surgery) in case 2. Alignment of the cervical spine had improved, and the accurate insertion of both right C2 pedicle and left C2 laminar screws was confirmed. (a-p, anteroposterior.)
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At 1 week after installation of a halo ring and vest, posterior occipitoaxial fixation with right C2 pedicle and left C2 laminar screws (Vertex Max) and a decompressive procedure by resection of the C1 posterior arch were carried out (Fig. 8).