[Molecular mechanism of residual lumbago and leg pain after transforaminal endoscopic treatment of lumbar disc herniation].

OBJECTIVE: To observe the residual of lumbago and leg pain with contained type （CT） and non-contained type （NCT） lumbar disc herniation （LDH） after transforaminal endoscopic treatment, and to explore the role of hypoxia-inducible factor-1α（HIF-1α） and transient receptor potential vanillate 1（TRPV1） pathway.

METHODS: A total of 68 single-segment LDH patients were selected from July 2021 to October 2022, including 44 males and 24 females；aged 26 to 67 years old with an average of（43.63±11.94） years old；course of disease was 4 to 36 （18.91±10.34） months；body mass index was （24.45±4.00） kg·m-2 ；there were 7 cases of L3,4 segments, 32 cases of L4,5 segments, and 29 cases of L5 S1 segments. All of them were performed with percutaneous intervertebral endoscopic extraction of nucleus pulposus and were divided into contained group（CT group） and non-contained group （NCT group） with 34 cases respectively according to the integrity of outer layer of fibrous annulus observed during operation. A total of 17 patients who underwent open surgery for scoliosis or vertebral fracture were selected as control group, including 12 males and 5 females；aged 21 to 65 years old with an average of （39.41±12.80） years old；body mass index was （24.86±4.11） kg·m-2 . The relative mRNA expression quantity of HIF-1α, TRPV1 in nucleus pulposus were measured by quantitative real-time PCR. The contents of neurokinin 1 receptor （NK1R）, nerve growth factor （NGF）, vascular endothelial growth factor （VEGF） in nucleus pulposus and the serum substance P （SP） and calcitonin gene-related peptide （CGRP） were detected by enzyme linked immunosorbent assay （ELISA）. The threshold of lumbar tenderness was detected by a pressure pain meter. The degree of lumbago and lumbar function were evaluated by visual analog scale （VAS） and Oswestry disability index （ODI） separately. The residual rate of postoperative lumbago and leg pain was assessed.

RESULTS: The mRNA relative expression quantity of HIF-1α and TRPV1, and the contents of NK1R, NGF and VEGF in nucleus pulposus, and the levels of serum SP and CGRP before surgery in the NCT group were higher than those in the CT group（ P <0.05）, and those in the CT group were higher than the control group（ P <0.05）. At day 7 after surgery, the serum SP and CGRP levels, lumbago and leg pain VAS scores and lumbar ODI index in two LDH groups were lower than before surgery （ P <0.05）, and those in the NCT group were higher than the CT group（ P <0.05）, and the threshold of lumbar tenderness in the NCT group was lower than the CT group（ P <0.05）. The differences of lumbago and leg pain VAS scores, lumbar ODI index and lumbar tenderness threshold between preoperative and postoperative 7 days in the NCT group were lower than those in the CT group（ P <0.05）. The residual rate of lumbago and leg pain at 7 days after surgery in the NCT group was higher than that in the CT group（ P <0.05）.

CONCLUSION: HIF-1α and TRPV1 pathway promoted the excessive production of NGF, VEGF, NK1R in nucleus pulposus and serum neuropeptides SP and CGRP, which may lead to the higher residual rate of lumbago and leg pain with non-contained lumbar disc herniation postoperative.