Three-Dimensional Spinal Cord Volume Mobility on Dynamic Cervical CT Myelography Is Associated With Postoperative Neurological Recovery in Cervical Spondylotic Myelopathy

<title>Abstract</title> <p>Purpose Dynamic cervical motion may aggravate spinal cord compression in cervical spondylotic myelopathy (CSM), whereas conventional measurements primarily characterize compression at a single axial level. This study introduced spinal cord volume mobility (SCVM), derived from three-dimensional reconstruction of dynamic CT myelography (CTM), and investigated its association with postoperative neurological recovery. Methods In this prospective observational study, 23 patients with CSM underwent preoperative CTM in flexion, neutral, and extension positions and were followed for 3 years after surgery. The spinal cord at the most compressed intervertebral segment was reconstructed using Mimics. SCVM was defined as δ = |2 × (V_flexion − V_extension)/(V_flexion + V_extension)|. Cross-sectional area (CSA), anteroposterior diameter, and reconstructed volume were compared across positions. Associations of imaging parameters with the 3-year Japanese Orthopaedic Association (JOA) recovery rate and postoperative JOA score were evaluated. Results CSA at the most compressed level decreased from 33.80 ± 10.57 mm² in flexion and 31.43 ± 8.88 mm² in neutral to 23.69 ± 9.91 mm² in extension (both comparisons with extension, P &lt; 0.001). Reconstructed segmental volume was lower in extension than in flexion (208.16 ± 87.99 vs 234.52 ± 85.61 mm³, P = 0.034). Patients with poor recovery had longer disease duration, smaller extension CSA, and greater SCVM. SCVM was negatively correlated with the 3-year JOA recovery rate (r = − 0.548, P = 0.0068), whereas extension CSA was positively correlated with recovery (r = 0.509, P = 0.0131). In multivariable analysis, SCVM remained negatively associated with the 3-year postoperative JOA score (B = − 8.071, β = −0.336, P = 0.010). Conclusion Three-dimensional SCVM quantifies posture-related spinal cord deformation on dynamic CTM. Greater SCVM was associated with less favorable neurological recovery and may provide complementary information beyond conventional single-slice CSA assessment.</p>