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Purpose <p>To quantify in vivo six-degree-of-freedom (6DOF) kinematics of the upper cervical spine during active head rotation in patients with atlantoaxial dislocation (AAD) and to compare the motion patterns with healthy adults.</p> Methods <p>Fifty-one imaging-confirmed AAD patients (23 men, 28 women; mean age 52 ± 15 years) performed left- and right-head rotation under dynamic fluoroscopic imaging system (DFIS). Subject-specific 3-D models of the skull and C1–C3 were reconstructed from computed tomography (CT), registered frame-by-frame, and expressed with an extrinsic Y–X–Z Euler sequence. Intersegmental range of motion (ROM) were contrasted with published normative datasets.</p> Results <p>At C0–C1, flexion–extension (5.7 ± 3.6°) and lateral bending (4.6 ± 3.5°) were roughly 60% lower than controls (both <i>P</i> &lt; 0.001), whereas axial rotation was similar (5.9 ± 5.3°, <i>P</i> = 0.67). Primary C1–C2 rotation fell to 38.1 ± 22.8° (controls 61.9 ± 13.5°, <i>P</i> &lt; 0.001) accompanied by 3-fold increases in vertical and anteroposterior translations (both <i>P</i> &lt; 0.001). C2–C3 showed compensatory gains: axial rotation 6.2 ± 8.5° vs. 3.1 ± 1.6° (<i>P</i> = 0.004) and larger translations on all axes (all <i>P</i> &lt; 0.001). Motion was bilaterally symmetrical at C1–C2 and C2–C3, with only mild asymmetry in coupled lateral bending and mediolateral translation at C0–C1.</p> Conclusion <p>AAD markedly restricts C1–C2 rotation, stiffens occipito-atlantal nodding, and provokes hypermobility at C2–C3. These segment-specific 6DOF benchmarks enhance biomechanical insight into AAD pathomechanics and may refine surgical stability assessment.</p>

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In vivo three-dimensional kinematics of the upper cervical spine during upright head rotation in patients with atlantoaxial dislocation

  • 期刊论文

  • 发表日期：

    2025年10月22日

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  • Jian He,
  • Shilin Xue,
  • Yang Luo,
  • Zhirui Hu,
  • Cheng Zhang,
  • Shanshan Liu,
  • Xingyu Zhou,
  • Beining Zhao,
  • Fei Xu,
  • Hanyuan Guo,
  • Shenglin Wang,
  • Nanfang Xu

摘要

Purpose

To quantify in vivo six-degree-of-freedom (6DOF) kinematics of the upper cervical spine during active head rotation in patients with atlantoaxial dislocation (AAD) and to compare the motion patterns with healthy adults.

Methods

Fifty-one imaging-confirmed AAD patients (23 men, 28 women; mean age 52 ± 15 years) performed left- and right-head rotation under dynamic fluoroscopic imaging system (DFIS). Subject-specific 3-D models of the skull and C1–C3 were reconstructed from computed tomography (CT), registered frame-by-frame, and expressed with an extrinsic Y–X–Z Euler sequence. Intersegmental range of motion (ROM) were contrasted with published normative datasets.

Results

At C0–C1, flexion–extension (5.7 ± 3.6°) and lateral bending (4.6 ± 3.5°) were roughly 60% lower than controls (both P < 0.001), whereas axial rotation was similar (5.9 ± 5.3°, P = 0.67). Primary C1–C2 rotation fell to 38.1 ± 22.8° (controls 61.9 ± 13.5°, P < 0.001) accompanied by 3-fold increases in vertical and anteroposterior translations (both P < 0.001). C2–C3 showed compensatory gains: axial rotation 6.2 ± 8.5° vs. 3.1 ± 1.6° (P = 0.004) and larger translations on all axes (all P < 0.001). Motion was bilaterally symmetrical at C1–C2 and C2–C3, with only mild asymmetry in coupled lateral bending and mediolateral translation at C0–C1.

Conclusion

AAD markedly restricts C1–C2 rotation, stiffens occipito-atlantal nodding, and provokes hypermobility at C2–C3. These segment-specific 6DOF benchmarks enhance biomechanical insight into AAD pathomechanics and may refine surgical stability assessment.