The first anatomical description of extreme lateral protrusions dates back to 1944, and with the development of spinal surgery, their clinical application has received increasing attention[1, 13]. Because the dorsal root ganglia are accompanied by motor and sensory components, LBP can be accompanied by severe nerve root pain. Most FLLDH occur at the L3-4 or L4-5 level; therefore, most patients have substantial thigh symptoms[14, 15]. Straight leg elevation tests are negative, and symptoms of scoliosis are exacerbated; therefore, this helps distinguish FLLDHs from other common disc herniations. In recent years, various surgical methods have emerged to treat FLLDH[7, 11, 16]. However, these surgical methods have changed over the years, including traditional open surgery, surgery using an operating microscope, microsurgery through a tubular channel, and percutaneous endoscopic surgery. With the advancement of minimally invasive spine technology and patients’ expectations, percutaneous endoscopic surgery and microsurgery through a tubular channel have been reported more frequently, the best treatment for FLLDH, however, remains controversial. Nellensteijnin reported 214 cases of FLLDH treated with transforaminal endoscopy; the median recurrence rate was 2.6%, the median complication rate was 5.1%, and the median was 8.0%. Porchet reported long-term prognosis in 202 patients with FLLDH; they used a 5–7-cm midline incision and transmuscular approach. The authors reported that the probability of postoperative complications was 5%. However, only 3 patients (1.5%) had complications that were directly related to the surgical procedure. According to Macnab's criteria, the results of surgical treatment were excellent or good, and the average VAS of radical leg pain before surgery to final follow-up was 8.5 to 2.2. The incidence of reoperation was significantly lower than that of the percutaneous endoscope. A study by Yoon found that, compared with lumbar discectomy, postoperative VAS and ODI scores following tubular microsurgery were significantly better than those of percutaneous endoscopic surgery. Our follow-up data were the similar.
Using endoscopic technology, the working sleeve is first inserted into the intervertebral foramen to identify the nerve root, and then the working sleeve is retracted along the nerve root to locate the protruding intervertebral disc. A group of 47 patients reported their experience with transforaminal endoscope technology for the treatment of distant lateral and foraminal protrusions . Their technique was similar to the Yeung technique, with the selected entry point of 8–12 cm from the midline. They advocated removing the central disc first and the final step was the removal of the extraforaminal disc. PELD procedure has some advantages compared with MD procedures. First, PELD can be performed under local anesthesia, and the second PELD is less invasive in incision length. In China, many surgeons use various methods to treat FLLDH using the in-outside method, which contradicts the currently accepted principle of removing only protruding discs and loose fragments located in the posterior annulus. Furthermore, this technique extends the operation time, and removal of the central disc increases the possibility of loss of long-term intervertebral disc height. For FLLDH, the protrusion disc is often located in the anterior medial aspect of the exiting nerve root, occupying part of the space of the intervertebral foramen, and causing “soft stenosis” in the intervertebral foramen. When the working sleeve is set through the narrow intervertebral foramen into the intervertebral disc, it squeezes the soft intervertebral disc nucleus tissue, leading to more severe compression of the exiting nerve root. Due to the presence of dorsal root ganglion (DRG), severe pain often occurs. We made appropriate adjustments and improvements to the puncture approach. The intervertebral disc nucleus pulposus protruding outside the intervertebral foramen tends to shift to the cranial and lateral side, and the exiting nerve root is squeezed towards the “outer side.” However, the “inside and below” space is relatively abundant, and this is the ideal position to place the puncture needle and the working sleeve slightly below the protrusion, which is beneficial in removing the protruding nucleus pulposus tissue (properly rotating the working cannula) and reducing nerve root injuries and irritation of the DRG. The puncture target was placed at the intersection of the slight inner side of the protruding position and the upper endplate of the caudal vertebra, wherein the lateral position of the puncture needle was located at the posterior horn of the caudal vertebral body and the anteroposterior position was located at the outer edge of the midpoint of the pedicle (Figs. 2a and 2b). Many studies have emphasized the need to educate and protect everyone in the room during fluoroscopy[24, 25]. The mean duration of radiation exposure was 2.87 ± 1.19 min in our PELD group. It is believed that the surgeon and patients need to limit their radiation exposure.
There are minimally invasive surgical treatments for FLLDH, including microendoscopic decompression of the endoscopic to minimize the damage to facet joints, muscles, and ligaments. Less muscle trauma and fewer osteotomies reduce lumbar back pain and adjacent disc degeneration, reducing lumbar instability and fusion. Furthermore, trans-tubular microsurgery helps reduce hospital stay and promotes rapid recovery. In this study, the average duration of hospitalization was 98.64 ± 15.65 hours, which is longer than the PELD group due to intratracheal anesthesia. Compared with conventional paramedian muscle-splitting approaches, trans-tubular microsurgery has the advantage of using a sequential dilator and finally a tubular retractor, which allows procedures in obese patients fast and simple compared to thin patients. In our department, the surgeons separate the paraspinal muscles using fingers. They are familiar with using microscopes, reducing the operation time. Choi et al. used the percutaneous endoscopic “targeted fragmentectomy” technique to treat 41 cases of FLLDH; 2 patients developed symptoms of relapse after the early symptoms improved (4.8%), 3 (7.3%) developed dysesthesia on the legs, 1 (2%) experienced persistent lower extremity pain after surgery and underwent microdiscectomy revision via paraspinal approach. In the MD group, intratracheal anesthesia helped the patient cooperate, the intraoperative vision was clear, and there was less nerve stimulation, which reduced the risk of lower limb numbness and recurrence after surgery. Nevertheless, regardless of the surgical method, to achieve adequate decompression, a certain number of bone resections and treatment of nerve roots and dorsal root ganglia are sometimes required. This may cause paresthesia, reflex sympathetic dystrophy, or chronic back pain in some patients at a 3-month follow-up.
There are several limitations to this study. First, it was a single-center study, and therefore may be subjected to selection bias. Hence, we instituted strict inclusion and exclusion criteria. Second, our sample size was small and it was a short-term follow-up. Multicenter studies and large samples prospective study, long-term clinical follow-ups are needed to validate our findings.