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Posterior-Only Approach for Reduction of Occipitocervical Instability with Vertical Migration of the Dens

Introduction Occipitocervical instability with vertical odontoid migration is a rare but potentially debilitating anomaly. Anterior decompression followed by posterior stabilization is commonly used to address the pathology, but the former is associated with significant morbidity. More recently, posterior-only techniques have been described to obtain reduction and stabilization for nonfused cases of cranial settling. Patients and Methods Retrospective analysis of seven cases of patients (four males, three females, age range 34–73 years) who suffered from occipitocervical instability with reducible vertical dislocation of the odontoid in the setting of various underlying pathology. Six patients were myelopathic preoperatively. The neurological status was classified according to the Nurick scale. Pain was assessed according to the Visual Analog Scale. Radiological measurements included preoperative and postoperative evaluation of the position of the tip of the odontoid process in relation to Chamberlain, McGregor, McRae, and Wackenheim lines, and measurement of the Ranawat line, the clival angle, and the Klaus height index. Follow-up ranged from 8 to 42 months. Results Five patients improved neurologically, and one remained stable. Pain improved significantly in these patients, and was completely eliminated in three of them. Obvious reduction of the deformity was demonstrated by the postoperative radiological craniometric measurements. One patient did not improve neurologically. Postoperative imaging revealed a very small reduction with practically unchanged ventral compression of the cord. He underwent transoral decompression at a second stage. No patient suffered from severe complications. No screw pullout, loosening, or fracture of implant has been observed so far. Conclusion Modern screw–rod systems enable intraoperative correction of nonfused deformity and indirect decompression of the cervicomedullary junction obviating the need for ventral decompression or preoperative traction. Patient selection is critical to ensure successful application of the reduction maneuvers.