Basilar invagination and atlantoaxial dislocation: Reduction, deformity correction and realignment using the DCER (distraction, compression, extension, and reduction) technique with customized instrumentation and implants

Abstract

Objective: The technique of distraction, compression, extension, and reduction (DCER) is effective to reduce, realign, and relieve cranio-spinal compression through posterior only approach. Methods: Study included all patients with atlantoaxial dislocation and basilar invagination (BI) with occipitalized C1 arch. Study techniques included Nurick grading, computed tomography scan to study atlanto-dental interval, BI, hyper-lordosis, and neck tilt. Sagittal inclination (SI), coronal inclination (CI), cranio-cervical tilt, presence of pseudo-joints, and anomalous vertebral artery were also noted. Patients underwent DCER with/without joint remodeling or extra-articular distraction (EAD) based on the SI being < 100°, 100°– 160°, or > 160° respectively. In cases with pseudo-joints, joint remodeling was performed in type I and EAD in type II. Customized ‘bullet shaped’ PSC spacers (n = 124) and prototype of the universal craniovertebral junction reducer (UCVJR, n = 36) were useful. Results: A total of 148 patients with average age 27. 25 ± 17. 43 years, ranging from 3 to 71 years (87 males) were operated. Nurick’s grading improved from 3.14 ± 1.872 to 1.22 ± 1.17 (p < 0. 0001). Fifty-two percent of total joints (n = 154/296 joints) were either type I (19%)/ type II (33%) pseudo-j oints. All traditional indices such as Chamberlein line, McRae line, atlanto-dental interval, and Ranawat line improved (p < at least 0. 001). BI, SI, and CI values correlated with type of pseudo-joints (p < 0. 0001). Side of neck tilt correlated with the type of pseudo-joint (p < 0.0001). Cervical hyperlordosis improved significantly (p < 0.0001). Conclusion: Occipito-C2 pseudo-joints are important in determining the severity of BI. Asymmetrical pseudo-joint causes coronal/neck tilt. Type of pseudo-joint can strategize by DCER. Customized instruments and implants make technique safe, effective and easier.