Pathomechanism of Lower-level Discogenic Groin Pain and Clinical Outcomes of Percutaneous Endoscopic Discectomy for the Treatment of Discogenic Groin Pain

Background: Groin pain can be induced by high-level (L1-L2 or L2-L3) lumbar disc herniation. However,4.1% of patients with lower-level (L4-L5 or L5-S1) lumbar disc herniation also complained of groin pain. Thepathomechanism of groin pain occurring due to lumbar disc herniation at and below the L4-5 levels is stillunclear.Objective: To investigate the afferent pathways of lower-level lumbar disc herniation induced groin pain.And evaluate the clinical results of transforaminal endoscopic discectomy treatment for discogenic groinpain.Study Design: This retrospective observational study used an experimental design (institutional reviewboard: HROH 201-C2-100).Setting: The research took place in the Laboratory Research Center and spine center at The First AffiliatedHospital of Harbin Medical University.Methods: Firstly, 14 adult Wistar rats were randomly divided into 2 groups: control group (the paravertebralsympathetic trunks were preserved) and experimental group (the paravertebral sympathetic trunks wereresected). All Wistar rats were intraperitoneally anesthetized, and then 1 μL of fast blue was injected intothe dorsal rami of L2 spinal nerves on the right side. Forty hours later, 2 μL of nuclear yellow was injectedinto the right posterior portion of the L5-L6 intervertebral disc. The L1 and L2 spinal ganglia were sectioned8 hours later to observe fluorescently double-labeled cells and the effect of paravertebral sympathetictrunk resection. Secondly, 14 adult Wistar rats were anesthetized, and the right posterior portion of the L5-L6 intervertebral disc was electrostimulated to observe potential changes in the genitocrural nerve in theipsilateral inguinal region. To evaluate the clinical outcomes of transforaminal endoscopic discectomy for thetreatment of discogenic groin pain, between September 2015 and May 2017, transforaminal endoscopicdiscectomy was performed on 30 patients with lower-level discogenic groin pain. Outcomes were analyzedutilizing the visual analog scale, Oswestry disability index, and MacNab Criteria.Results: The total proportion of cells in the right L1 and L2 spinal ganglia with fast blue/nuclear yellowdouble labeling was 3.33% and 3.41% (48 and 56), respectively. The number of fluorescently doublelabeledcells in the resected paravertebral sympathetic trunk group was significantly less (P < 0.01). Electricalstimulation of the right posterior portion of the L5-L6 intervertebral disc could elicit action potentials in theipsilateral genitofemoral nerve. All patients were followed for 12 months, and the visual analog scale scoreat 1 week, 1 month, 3 months, 6 months, and 12 months after the operation was 0.79 ± 0.55, 0.54 ± 0.55,0.47 ± 0.65, 0.51 ± 0.65, and 0.69 ± 0.55, respectively, showing a significant decrease compared with thepreoperative visual analog scale score (P < 0.01). Based on the MacNab scoring system, the effective ratewas 100%, and the rate of good and excellent results was 93.3%.Limitations: A relatively small number of patients and a short follow-up period.Conclusions: Discogenic groin pain is transmitted by sympathetic nerves and appears in the areasegmentally innervated by the anterior rami of the L1 and L2 spinal nerves. Posterolateral percutaneoustransforaminal endoscopic discectomy and radiofrequency thermal annuloplasty are effective minimallyinvasive alternative treatments for discogenic groin pain.Key Words: Discogenic groin pain, percutaneous transforaminal endoscopic discectomy, radiofrequencythermal annuloplasty