Body position alters kyphosis angle: comparison of supine MRI and prone full-length spine CT scout view in osteoporotic thoracolumbar fractures

Objective: To compare the degree of kyphosis among patients with old thoracolumbar fracture kyphosis (OTFK) in various positions and to assess kyphosis flexibility. Methods: , respectively. Kyphosis flexibility (KF) was calculated based on these measurements. Pairwise comparisons were performed using the Wilcoxon signed-rank test with Bonferroni correction after an overall Friedman test. Equivalence analysis between prone FLS-CT and supine MRI was performed using a prespecified margin of ±5°. Interobserver reliability was assessed using the intraclass correlation coefficient (ICC). Results: > 0.05). In equivalence analysis, all 95% confidence intervals of the paired mean differences between prone FLS-CT and supine MRI measurements were entirely within the prespecified equivalence margin of ±5°. Interobserver reliability was excellent across all imaging modalities, with ICC values ranging from 0.985 to 0.992. Conclusion: Kyphosis severity was significantly reduced in the preoperative recumbent position in patients with OTFK. Prone FLS-CT and supine MRI provided clinically comparable estimates of positional kyphosis correction, suggesting that both modalities may be useful for preoperative assessment of kyphosis flexibility in OTFK.