To quantitatively compare the left-right asymmetry of the sacroiliac joints between postpartum women with low back pain and healthy postpartum women using multi-slice spiral CT (MSCT), and to investigate its imaging features and diagnostic value for postpartum sacroiliac joint subluxation.

35 postpartum women with low back pain treated in our hospital between January 2023 and December 2024 were selected as the study group (postpartum low back pain group), while 35 healthy postpartum women served as the control group (healthy postpartum group). 16-slice spiral CT was used to scan the sacroiliac joints, and multiplanar reconstruction was employed to for image processing. A total of 18 measurement points were selected in the anterior, middle, and posterior regions from S1 to S3 to calculate the degree of left-right asymmetry. Differences in asymmetry between the two groups at each measurement point were compared, and receiver operating characteristic (ROC) curve analysis was used to identify diagnostic cutoff values.

There was no significant difference in age, postpartum duration, or other baseline characteristics between the two groups. Significant left-right asymmetry was observed at 14 measurement points (P<0.05). The degree of asymmetry at all significant locations was greater in the postpartum low back pain group than in the control group, with the most pronounced difference observed in the posterior region of S2-2 measurement point [(0.860±0.608) mm vs. (0.491±0.205) mm, P=0.001 7)]. ROC curve analysis showed that the asymmetry in the anterior region of S1-1 level had the best diagnostic performance (AUC=0.738), with a cutoff value of 0.3 mm.

Postpartum women with low back pain exhibit significant left-right asymmetry in the sacroiliac joints, with increased asymmetry at multiple anatomical locations. A left-right asymmetry ≥0.3 mm in the anterior region of S1-1 level can serve as a key reference standard for evaluating postpartum sacroiliac joint subluxation.