Association Between Vertebral Endplate Defects and Patient-reported Symptoms: An Immunohistochemical Study Investigating the COX-2/PGE-2/EP-4 Axis.

BACKGROUND CONTEXT: Vertebral endplate defects are often implicated in degenerative disc disorders, yet their connection to patient-reported symptoms remains unclear. COX-2 and PGE-2 are known for their roles in inflammation and pain, with EP-4 receptor involvement in pain signaling. Examining their expression in vertebral endplate tissues may provide insights into pathomechanism of low back pain.

PURPOSE: To investigate the association between endplate defects and patient-reported symptoms and to further clarify the role of the COX-2/PGE-2/EP-4 axis in the pathogenesis of chronic low back pain.

STUDY DESIGN/SETTING: Retrospective study PATIENT SAMPLE: A total of 71 patients who had undergone single-level L4/5 or L5/S1 modified laminectomy decompression preserving proximal upper laminae and transforaminal lumbar interbody fusion surgery were included in this study, including 18 patients diagnosed with lumbar disc herniation, 19 with lumbar disc herniation accompanied by degenerative lumbar spinal stenosis, and 34 with degenerative spondylolisthesis.

OUTCOME MEASURES: Demographic data, Pfirrmann grade, Modic changes, endplate defect score, visual analog scale (VAS) for back and leg pain, and Oswestry Disability Index (ODI) before surgery, 3-month and 6-month follow-up, and the percentage of immune-positive cells (COX-2, PGE-2, and EP-4) in endplate tissue sections.

METHODS: Patients were divided into Defect and Non-defect groups according to endplate morphology on lumbar MR. All intraoperative endplate specimens were immediately fixed in 10% formaldehyde, and then embedded in paraffin 3 days later for tissue sections. The outcome measures were compared between the Defect group and Non-defect group. Data were analyzed using independent t-tests and χ² tests. Pearson's rank correlation test was used to assess correlations between patient-reported symptoms and the percentage of immune-positive cells in the groups. Multivariable logistic regression models using the forward stepwise likelihood ratio method were used to identify the factors that were independently associated with endplate defects.

RESULTS: The age of Defect group was significantly higher than that of Non-defect group (52.5±7.7 vs. 57.2±9.1. P=0.024). There were no significant differences in gender, diagnosis, BMI, comorbidities, or surgical level between the two groups. Modic changes (Type Ⅱ/Type Ⅲ) were more common in patients of Defect group than Non-defect group (38.5% vs. 11.1%, P<0.001), and so was disc degeneration (Pfirrmann grade Ⅳ/Ⅴ) (69.2% vs. 33.3%, P<0.001). Defect group had significantly higher VAS-Back (6.5±2.0 vs. 4.9±1.6, P<0.001) and ODI scores (62.9±10.7 vs. 45.2±14.8, P<0.001) than Non-defect group, while there was no significant differences between the two groups during the 3 and 6-month follow-up after surgery. Histologically, Defect group was characterized by upregulation of COX-2, PGE-2, and EP-4 in endplate tissue sections. Both in Defect and Non-defect groups, VAS-Back showed moderate positive correlations with the expressions of COX-2 (r=0.643; r=0.558, p both<0.001), PGE-2 (r=0.611; r=0.640, p both<0.001), and EP-4 (r=0.643; r=0.563, p both<0.001). Multivariate regression analyses reveled that percentage of COX-2-positive cells was associated with endplate defects (OR=1.509, 95%CI [1.048∼2.171], P=0.027), as well as percentage of PGE-2-positive (OR=1.291, 95%CI [1.106∼1.508], P=0.001) and EP-4-positive cells (OR=1.284, 95%CI [1.048∼2.171], P=0.003).

CONCLUSIONS: Patients with endplate defects had worse quality of life, more severe disc degeneration and Modic changes, and up-regulated COX-2/PGE-2/EP-4 axis expression in cartilage endplates in patients with defected endplates. Inflammatory factors may significantly contribute to the onset and progression of chronic low back pain in patients with endplate defects, consequently impacting patient-reported symptoms.