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. The pathomechanism of groin pain occurring due to lumbar disc herniation at and below the L4-5 levels is still unclear.

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 groin pain.

Study Design: This retrospective observational study used an experimental design (institutional review board: HROH 201-C2-100).

Setting: The research took place in the Laboratory Research Center and spine center at The First Affiliated Hospital of Harbin Medical University.

Methods: Firstly, 14 adult Wistar rats were randomly divided into 2 groups: control group (the paravertebral sympathetic trunks were preserved) and experimental group (the paravertebral sympathetic trunks were resected). All Wistar rats were intraperitoneally anesthetized, and then 1 (mu)L of fast blue was injected into the dorsal rami of L2 spinal nerves on the right side. Forty hours later, 2 (mu)L of nuclear yellow was injected into the right posterior portion of the L5-L6 intervertebral disc. The L1 and L2 spinal ganglia were sectioned 8 hours later to observe fluorescently double-labeled cells and the effect of paravertebral sympathetic trunk 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 the ipsilateral inguinal region. To evaluate the clinical outcomes of transforaminal endoscopic discectomy for the treatment of discogenic groin pain, between September 2015 and May 2017, transforaminal endoscopic discectomy was performed on 30 patients with lower-level discogenic groin pain. Outcomes were analyzed utilizing 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 yellow double labeling was 3.33% and 3.41% (48 and 56), respectively. The number of fluorescently double-labeled cells in the resected paravertebral sympathetic trunk group was significantly less (P < 0.01). Electrical stimulation of the right posterior portion of the L5-L6 intervertebral disc could elicit action potentials in the ipsilateral genitofemoral nerve. All patients were followed for 12 months, and the visual analog scale score at 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 the preoperative visual analog scale score (P < 0.01). Based on the MacNab scoring system, the effective rate was 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 area segmentally innervated by the anterior rami of the L1 and L2 spinal nerves. Posterolateral percutaneous transforaminal endoscopic discectomy and radiofrequency thermal annuloplasty are effective minimally invasive alternative treatments for discogenic groin pain.