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Radiograph-based intervertebral sagittal translation-to-canal diameter ratio as a quantitative imaging marker for
1Orthopaedics, Zigong Fourth People's Hospital, Zigong, China. 374648027@qq.com.
Objective:
To compare radiographic differences between clinically suspected symptomatic lower cervical instability segments and asymptomatic normal segments and to evaluate the value of the radiograph-based intervertebral sagittal translation-to-canal diameter ratio (TCDR) as a quantitative imaging marker for lower cervical instability.
Methods:
This single-center retrospective study screened 197 clinically suspected cases of lower cervical instability. Seventeen cases with multilevel abnormalities but without a clearly identifiable clinically dominant responsible segment were excluded, leaving 180 patients with one clinically prespecified responsible segment. The control group included 60 asymptomatic examinees, with four segments from C3/4 to C6/7 measured in each participant. Group differences in intervertebral sagittal translation, radiographic sagittal canal diameter, intervertebral angulation, TCDR, and related indices were compared. ROC analysis, patient-cluster bootstrap, segment-stratified analysis, patient-level sensitivity analysis, cluster-robust logistic regression, and interobserver reliability analysis were performed.
Results:
Age and sex did not differ between groups, but segment distribution differed significantly (P < 0.001). TCDR was higher in the study group than in controls (0.170 ± 0.066 vs. 0.067 ± 0.060, P < 0.001). The segment-level AUC of TCDR for lower cervical instability was 0.889 with an optimal cutoff of 0.087, 91.11% sensitivity, and 72.08% specificity. TCDR outperformed absolute intervertebral sagittal translation and intervertebral angulation, was positively correlated with instability (r = 0.631, P < 0.001), showed segment-specific AUCs of 0.811-0.929, and remained independently associated with lower cervical instability after adjustment (OR = 1.26, 95% CI 1.19-1.34, P < 0.001).
Conclusion:
Radiograph-based TCDR showed good segment-level discriminative ability for clinically suspected lower cervical instability and may serve as an adjunctive quantitative radiographic marker for assessing a responsible segment.