Introduction: The Ames cervical deformity (CD) classification provides a paradigm for CD based on measurements taken from x-ray films. Whether these measurements of deformity correlate with the degree of stenosis and compression of the cervical spinal cord as found on MRI is unknown.
Methods: Inclusion: CD patients (C2-C7 Cobb>10°, CL>10°, cSVA>4cm, or CBVA>25°) with deformity apices below the C2 level and BL MRI images. Spinal canal and cord cross sectional area (CSA) were measured at each C2-C7 body and interspace. Stenotic levels (canal/body ratio <0.82) and a canal/disc ratio were measured via Pavlov’s method. Maximal cord compression (MCC) CSA was recorded, and normalized by MCC ratio (MCC/C2 cord CSA. Correlations between MRI metrics and patient reported outcome measures (PROMS) were gauged using spearman’s rho.
Results: 55 CD patients were included (Age: 57.1, Gender 61.8%F, 83.9% White, 9.7% Black, BMI 29.9, CCI: 0.37). BL radiographic presentation: TS-CL 29.3°, CL 3.0°, cSVA 28.8mm, PI-LL -0.9, PT 18.2, SVA 1.8. Ames deformity descriptors: 55% C, 35% CT, 10% T. Mean BL C2-C7 canal CSA was 258.2±56.6mm2, mean C2-C7 cord CSA was 70.2±11.3mm2, mean MCC was 58.0±14.6mm2, mean MCC Ratio was 0.77±0.16, mean Pavlov ratio was 0.78±15, mean canal/disc ratio was 0.56±0.12 and mean # of stenotic levels was 3.7±1.9. BL MRI metrics and BL sagittal radiographic parameters did not correlate. Lower BL C2-C7 canal CSA correlated with lower BL mJOA scores (Rs:.376, P=.018), while lower BL C2-C7 canal CSA (Rs:.485, P=.014) and cord CSA (Rs:.484, P=.049) correlated with BL gait impairment. Lower MCC was associated with a positive Hoffman’s test (Rs:0.474, P=.047).
Conclusions: Current CD x-ray measurements do not predict the degree of cord compression or canal compromise found on MRI. Increased mean C2-7 spinal canal stenosis correlates with increased cord dysfunction as assessed by mJOA and clinical examination. Smaller area of maximal cord compression on axial MRI correlates with a positive Hoffman’s sign.
Patient Care: Understanding the associations between spinal canal/cord compression and the occurrence of neurologic symptoms, will help physicians have a more complete understanding of a patient's presentation, etiology of neurologic symptoms, and improve treatment decision-making.
Learning Objectives: Investigate the predictability of current cervical deformity classification systems in regards to spinal canal/cord compression, as well as determine associations between canal/cord dimensions and neurologic clinical symptoms.