An in Vivo, Three-Dimensional (3D), Functional Centers of Rotation of the Healthy Cervical Spine

Abstract

ObjectiveThis study examined cervical center of rotation (COR) positions in seven postures using validated cone beam computed tomography (CBCT) combined with 3D-3D registration in healthy volunteers. MethodsCBCT scans were performed on twenty healthy volunteers in seven functional positions, constructing a three-dimensional model. Images were registered to the neutral position using 3D-3D registration, allowing analysis of kinematic differences and rotational axes. COR measurements were obtained for each segment (C2/3 to C6/7) in each posture. ResultsThe CORs of C2/3 to C6/7 were predominantly posterior (-5.3±3.8 ∼ -0.6±1.2mm) and superior (16.5±6.0 ∼ 23.6±3.2 mm) to the intervertebral disc's geometric center (GC) in flexion and extension. However, the C4/5 segment's COR was anterior to the GC (2.0±9.8 mm) during flexion and close to it in the right-left direction. During left-right twisting, the CORs of C2/3-C6/7 were posterior (-21.8±10.5 ∼-0.9±0.8 mm) and superior (3.1±7.5 ∼23.2±3.6 mm) to the GCs in anterior-posterior and superior-inferior directions, without consistent right-left directionality. During left-right bending, each segment's COR was predominantly posterior (-25.2±13.1 ∼-6.5±9.9 mm) and superior (0.3±12.5 ∼12.1±5.1 mm) to the GC in anterior-posterior and superior-inferior directions, except for the C2/3 segment, located inferiorly (-5.9 ±4.1 mm) in left bending. The right-left COR position varied across segments. ConclusionsOur findings reveal segment-specific and posture-dependent COR variations. Notably, the CORs of C3/4, C4/5, and C5/6 consistently align near the intervertebral disc's GC at different postures, supporting their suitability for total disc replacement surgery within the C3/4 to C5/6 segments.