Three-dimensional kinematic analysis of the cervical spine following posterior atlantoaxial fusion under physiological loading: An in vivo study.

BACKGROUND

This study aimed to analyze the three-dimensional cervical motion characteristics in patients who underwent posterior atlantoaxial fusion surgeries using cone beam computed tomography and 3D3D registration technology.

METHODS

The study selected 20 patients who underwent posterior atlantoaxial fusion surgery and 20 healthy people as the control group. All subjects underwent cone beam computed tomography scans of the occipital and cervical spine in 7 different functional positions, then 3D3D registration of Occipital-C7 was performed at each functional position to calculate the motion characteristics of each segment. The ranges of motion of the entire cervical spine and each segment were obtained in each functional position.

FINDINGS: In the experimental group, ranges of motion of C1-C7 in flexion-extension and left-right twisting were significantly lower compared to controls (41.9° ± 13.8° vs. 56.6° ± 11.6°, 29.3° ± 9.6° vs. 91.2° ± 13.7°, respectively, P < 0.05). In the occipital-atlas segment, range of motion in flexion-extension was significantly smaller in the experimental group than controls (10.7° ± 3.2° vs. 19.4° ± 4.2°, P < 0.001), but it was larger in twisting (5.3° ± 4.2° vs. 2.1° ± 1.8°, P < 0.05). The twisting range of motion of C2-C3 was 4.7° ± 2.0° in the experimental group and 3.1° ± 1.6° in the control group (P < 0.05). Additionally, the alteration in ranges of motion during flexion-extension was primarily characterized by less extension.

INTERPRETATION: The posterior atlantoaxial fusion surgery induced biomechanical changes in the cervical spine. Following the procedure, the movement of C1-C7 during flexion-extension and twisting was significantly lower, with varying degrees of impact on adjacent and lower cervical segments. Moreover, the surgery had a greater effect on cervical extension than flexion.