Introduction: Cervical spondylotic myelopathy (CSM) is the leading cause of spinal cord dysfunction. The relationship among cervical alignment, sagittal balance and myelopathy has not been well characterized. Our objective was to assess the association of myelopathy scores with cervical sagittal alignment and normalized spinal cord volume in patients with CSM.
Methods: This was a post-hoc analysis of the prospective, multicenter AOSpine North America CSM study. Inclusion for the present study required a preoperative cervical MRI and neutral sagittal cervical x-ray. Techniques for MRI assessment of spinal cord dimensions were developed. Correlations between imaging and HRQOL scores were assessed.
Results: 56 patients inclusion criteria (mean age=55.4 years). The modified Japanese Orthopedic Association (mJOA) scores correlated with C2-C7 SVA (r=-0.281, p<0.05). Spinal cord volume correlated with cord length (r=0.472, p<0.001) and cord average cross-sectional area (r=0.957, p<0.001). Based on all patients, no correlations were found between MRI measurements of spinal cord length, volume, mean cross-sectional area or surface area and outcomes. For patients with cervical lordosis, mJOA correlated positively with cord volume (r=0.366, p<0.05), external cord area (r=0.399, p<0.05), and mean cross-sectional cord area (r=0.345, p<0.05). In contrast, for patients with cervical kyphosis, mJOA correlated negatively with cord volume (r=-0.496, p<0.05) and mean cross-sectional cord area (r=-0.535, p<0.05).
Conclusions: This study is the first to correlate cervical sagittal balance (C2-C7 SVA) to myelopathy severity. We found a moderate negative correlation in kyphotic patients of cord volume and cross-sectional area to mJOA. The opposite (positive correlation) was found for lordotic patients, suggesting a relationship of cord volume to myelopathy that differs based on sagittal alignment. It is interesting that sagittal balance but not kyphosis is tied to myelopathy score. Future work will correlate alignment changes to cord morphology changes and myelopathy outcomes.
Patient Care: Enhancing our understanding of the relationships between cervical sagittal alignment and myelopathy.
Learning Objectives: By the conclusion of this session, participants should be able to: (1) appreciate that cervical spondylotic myelopathy is the most common cause of spinal cord dysfunction; (2) appreciate the novel techniques developed for in vivo assessment of spinal cord dimensions; and (3) recognize the negative impact of poor sagittal balance on myelopathy scores.