Assessment of Flexion-Extension Motion After Occipitocervical and Atlantoaxial Fusion in Children

BACKGROUND AND OBJECTIVES: Adult biomechanical studies suggest a significant reduction in flexion-extension motion after occipitocervical and atlantoaxial fusion. Anecdotal experience in children suggests a lower magnitude of reduction in motion after these procedures, but high-quality quantitative assessments of this motion have not yet been performed. As such, the aim of this study was to determine the magnitude of reduction in cervical spine flexion-extension after O-C2 and C1-2 fusion in pediatric patients. METHODS: The Pediatric Spine Study Group international registry was queried for patients aged 21 years or younger who underwent O-C2 or C1-2 instrumentation and fusion. Patients with cervical spine flexion-extension radiographs preoperatively and ≥6 months postoperatively were included. Flexion, extension, and overall range of motion (ROM) of the cervical spine were measured on radiographs using McGregor line and the inferior endplate of C7. RESULTS: In total, 34 patients were included, with 19 undergoing index O-C2 and 15 undergoing index C1-2 stabilization. The mean age was 9.3 ± 4.5 years with average follow-up of 3.5 ± 2.6 years. The most common etiologies were syndromic (n = 20) and congenital (n = 9). Patients undergoing O-C2 fusion had reduced neck extension (80° vs 69.6°, P = .003) and overall ROM (92.9° vs 80°, P = .002) after stabilization, but no significant reduction in flexion (−12.9° vs −10.4°, P = .324). After C1-2 fusion, there was no significant reduction in overall ROM (85.0° vs 77.5°, P = .079), extension (70.5° vs 63.4°, P = .120), or flexion (−14.6° vs −14.0°, P = .831). CONCLUSION: In this cohort, children undergoing O-C2 stabilization had a 13.9% reduction in flexion-extension motion of the cervical spine, primarily due to a reduction in extension. There may be a smaller reduction in flexion-extension motion after stabilization in children when compared with adult studies. Further studies with video analysis including axial rotation and lateral bending will be necessary to comprehensively quantify cervical spine motion after fusion across the occipitocervical and atlantoaxial junctions.