Effects of transverse connector on reduction and fixation of atlantoaxial dislocation and basilar invagination using posterior C1-C2 screw-rod technique

Abstract

Background context: The mechanical strength provided by internal fixation is crucial for maintaining reduction and facilitating bony fusion. Though satisfactory results with the C1-C2 technique have been acquired in most clinical reports, the related problems of fusion delay and pseudarthrosis still exist. To increase the chance of bony fusion, a transverse connector (TC) is frequently used to augment torsional stiffness of thoracolumbar screw/rod constructs. Nevertheless, the clinical implication of TC in the management of atlantoaxial dislocation (AAD) and basilar invagination (BI) remains largely unknown.

Purpose: To evaluate the effects of TC application on C1-C2 screw-rod constructs based on consecutive adult patients with AAD and BI in a single institution over a 10-year period.

Study design: A retrospective study.

Patient sample: Patients with AAD and BI, who were treated with posterior C1-C2 screw-rod technique with or without TC usage from June 2007 to June 2017 at a single institution.

Outcome measures: The radiological measurements included the anterior atlantodental interval (AADI), posterior atlantodental interval (PADI), height of odontoid process above Chamberlain line, and cervicomedullary angle (CMA). Patients' neurologic status was evaluated with the Japanese Orthopaedic Association (JOA) score. Fusion status was evaluated at different follow-up periods.

Methods: We compared the difference of clinical, radiological, and surgical outcomes between the TC and NTC groups postoperatively.

Results: In total, there were 149 consecutive patients in the TC group and 168 patients in the NTC group. On average, 1.2 TCs per patient were used in the TC group. No significant differences were identified for operative time and blood loss between groups. There was also no statistical difference in the radiological measurements of AADI, PADI, Chamberlain line, and CMA between the TC and NTC groups preoperatively and postoperatively. A significantly higher JOA score was obtained in the TC group than that in the NTC group postoperatively. The fusion rates were higher in the TC group than those in the NCT group at the early stage postoperatively (3 and 6 months; p<.01).

Conclusions: Use of TCs seems to improve bony fusion and neurologic outcomes in the treatment of AAD and BI with C1-C2 screw-rod technique.

Keywords: Atlantoaxial dislocation; Basilar invagination; Biomechanical stability; Bone fusion; C1–C2 fixation; Craniovertebral junction; Transverse connector.