Abstract: BACKGROUND: According to different locations of lumbar disc herniation, it can be classified into many types. Among them, patients with intradural sac type lumbar disc herniation have severe clinical symptoms, which greatly affect their quality of life. Therefore, this article studies the risk factors for its onset, and improving the preoperative diagnostic rate is of great significance for the treatment and prevention of this disease. 
OBJECTIVE: To explore the risk factors for intradural lumbar disc herniation. 
METHODS: A retrospective analysis was conducted on 15 patients with intradural lumbar disc herniation (herniation group) admitted to three hospitals in Xuzhou city from May 2014 to November 2022. Propensity score matching was used to match patients with lumbar disc herniation who did not protrude into the dura mater in a ratio of 1:4. A total of 59 patients were selected and included in the non-herniation group. Clinical data were observed in the two groups. Univariate and binary logistic regression analysis, multiple linear regression, and PROBIT regression analysis were utilized to identify the relevant risk factors for intradural lumbar disc herniation.
RESULTS AND CONCLUSION: (1) The results of univariate analysis showed that the average disease course, proportion of segments, modified Pfiirmann grading, sacral tilt angle, proportion of previous lumbar spine surgery history, and proportion of heavy manual workers, proportion of lumbar spinal stenosis, redundancy of the cauda equina, and ossification of the posterior longitudinal ligament all showed statistical differences in the herniation and non-herniation groups (P < 0.05). (2) Multivariate regression analysis showed that duration of disease, protruding segment, history of lumbar surgery, modified Pfiirmann grading, cauda equina redundancy, and lumbar spinal stenosis were independent risk factors for intradural lumbar disc herniation. (3) Based on the influencing factors, an receiver operating characteristic curve was constructed, with an area under curve of 0.956 (95% CI: 0.913-0.998), indicating good discrimination. (4) There was a significant correlation between the duration of the disease, the protruded segment, the history of lumbar spine surgery, the modified Pfirmann classification, cauda equina redundancy, lumbar spinal canal stenosis, and the incidence rate of intradural lumbar disc herniation. 

Key words: intradural lumbar disc herniation, lumbar disc herniation, propensity score matching, risk factor, receiver operating characteristic curve