Clinical Outcomes of Atlantoaxial Dislocation Combined with High-Riding Vertebral Artery Using C2 Translaminar Screws

Atlantoaxial stabilization procedures in high-riding vertebral artery (HRVA) cases are challenging. C2 translaminar screws are rigid and pose no risk to the vertebral artery. The aim of this study was to present clinical outcomes of atlantoaxial dislocation combined with HRVA using C2 translaminar screws. Cases of atlantoaxial dislocation combined with HRVA surgically treated in our institution from 2007 to 2015 were retrospectively reviewed. Atlantodental interval and clivus-axial angle were measured. The Japanese Orthopaedic Association scale was used to evaluate neurologic status. There were 58 patients enrolled: 15 with instability and 43 with dislocation, 13 of which were irreducible. Incidence of bilateral HRVA was 5.2%. C1-C2 fixation was performed in 26 cases; atlantodental interval decreased from 9.9 ± 3.7 mm to 1.0 ± 1.7 mm (P < 0.05). C0-C2 fixation was performed in 32 cases; clivus-axial angle increased from 125° ± 13° to 150°± 15° (P < 0.05). Preoperative and postoperative Japanese Orthopaedic Association scores of 56 patients with myelopathy were 11.9 ± 2.8 and 14.6 ± 2.4, respectively (P < 0.05). Fusion rate was 93.1% (54/58) and at 4-month follow-up was 81% (47/58). In 14 cases of redislocation, final fusion was achieved; 3 of 14 required odontoidectomy. Four cases lacking bony fusion also required revision surgery. Redislocation rate was 31% (18/58), and reoperation rate was 12.1% (7/58). Surgical results of C2 translaminar screws are unsatisfactory, with high redislocation and reoperation rates in atlantoaxial dislocation cases. New treatment methods should be investigated to facilitate clinical outcomes. Extending fixed segments should be considered.