High lumbar disc herniation refers to L3/4 and higher lumbar disc herniation, which is reported in the literature to account for about 1% to 10% of lumbar disc herniation [1, 2], with heavy and complex clinical manifestations that are easily missed and misdiagnosed. Surgical nucleus pulposus removal is the main treatment method. Posterior microendoscopic discectomy (MED) has become an important treatment for lumbar disc herniation. 35 cases of high lumbar disc herniation were treated by MED from February 2005 to December 2008 with good results. The operation method, technique and efficacy evaluation of this procedure are summarized and analyzed, and reported as follows. Li Shuwen, Department of Cervical Spine Surgery, Second Affiliated Hospital of Inner Mongolia Medical University 1 Data and methods 1.1 General data 35 cases in this group, 19 males and 16 females, aged 35 to 65 years old, average 42 years old. The duration of the disease was 1-6 months, with an average of 3 months. The protrusion gap: L3/4 24 cases, L2/3 6 cases, L1/3 5 cases. The main symptom of the patients was low back pain with unilateral lower limb radiating pain in 9 cases and bilateral in 26 cases, and the CT or MRI manifestations were consistent with the clinical symptoms and signs. The cases in this group did not include those with combined lumbar instability, spinal stenosis and low lumbar disc herniation at the same time. 1.2 Surgical method 1.2.1 Preoperative preparation Routine examination of heart, lung, liver and kidney functions, all patients took X-ray frontal and lateral and hyperextension and hyperflexion lateral films, and lumbar spine CT scan or MRI examination. 1.2.2 Surgical equipment MED discoscopy system (Shandong Longguan Company), including: camera system: endoscope mainframe, fiber optic and lens, hernia lamp mainframe, TV monitor; tube system: surgical access tube, dilator, free fixation arm; instrumentation system: gun forceps, nucleus pulposus forceps, curved scraping spoon, etc. 1.2.3 Surgical procedure The two types of surgical approaches were selected: translaminar approach and intervertebral foraminal approach. 1.2.3.1 Transpedicular approach Continuous epidural anesthesia, placement of catheter, prone position, flexion of hip and knee at 45° each, abdominal suspension position with pillow, so that the lumbar spine is straight. A sterile sheet was routinely disinfected, and the needle was punctured at 0.8 cm from the affected side of the spinous process, and positioned under a C-arm X-ray machine, i.e., the tip of the needle in the lateral position was positioned directly over the intervertebral space. With the skin needle eye as the center, a longitudinal incision of about 1.6 cm long was made, and the dilating cannula was inserted step by step, pushing away the soft tissue, and the free arm was connected to fix the working cannula and connected to the endoscope head, light source, imaging line, and host, and the focus was adjusted to a clear state. The remnant soft tissue of the articular eminence was cleared with a microscopic nucleus pulposus clamp, and bipolar electrocoagulation was used to stop bleeding, and the inferior edge of the vertebral plate of the superior vertebra, the medial edge of the articular eminence, and the attached ligamentum flavum were clearly displayed through the monitor. The herniated intervertebral disc can be seen by biting off part of the inferior edge of the superior vertebral plate and the superior edge of the inferior vertebral plate with a lamina clamp, removing the hypertrophic ligamentum flavum, distancing the dural sac and nerve roots, and probing with an L-shaped hook to be sure that the nerve roots have been distanced, cutting the fibrous ring with a myelomeningocele knife, and removing the nucleus pulposus until the dural sac swells and resumes pulsation. After the operation, a large amount of Qingda saline was flushed to remove inflammatory mediators and reduce the inflammatory response. Drainage strips are placed and deep fascia and skin are sutured. 1.2.3.2 Transvertebral foraminal approach Anesthesia and position are the same as for the transvertebral interlaminar approach, with a Kirschner needle puncture 2.5 cm from the affected side of the spinous process and positioned under a C-arm X-ray machine, i.e., the tip of the needle is located at the outer edge of the articular eminence on the symptomatic side of the diseased intervertebral disc in the frontal view, and the tip of the needle is located in the intervertebral foramen and parallel to the vertebral space in the lateral view. With the skin needle eye as the center, a longitudinal incision of about 1.6 cm in length is made, the dilating cannula is inserted step by step, the soft tissue is pushed away, the working cannula is fixed by the free arm, the endoscope head, light source and imaging system are connected, and the focus is adjusted to a clear state. The working channel tube is located 1/2 for the synovial joint and 1/2 for the intertransverse soft tissue (Figure 1). The residual soft tissue of the articular eminence is cleared with a microscopic pulpal forceps, and the articular eminence is revealed by bipolar electrocoagulation to stop bleeding. After the outlet of the intervertebral foramen was identified by anatomical detachment, an angled scraper was used to push and peel the bone along the wall of the outlet, and an oblique biting forceps was used to bite away part of the bone at the outer edge of the articular eminence, and a nerve stripper and a pulling hook were used to peel and pull away the soft tissue to reveal the nerve roots and the intervertebral disc, with the nerve roots on the outer top of the disc (Figure 2). After protecting the nerve roots, the disc tissue was routinely removed, and the disc window and the nerve roots were flushed with large amounts of gentamic saline to remove inflammatory mediators and reduce the inflammatory response. 1.2.4 Postoperative treatment Postoperative antibiotics were applied for 3 days and neurotrophic drugs for 7 days. On the postoperative day, double ankle flexion and extension training was performed, straight leg raising training was performed on the next day, lumbar back muscle training was performed after 5 days, and the patient left the bed after 7 days under the protection of lumbar circumference. 1.2.5 Evaluation of efficacy The visual analogue scale (VAS) was used to evaluate the degree of back pain and lower limb pain before and after surgery; the Oswestry Disability Index (ODI) was used to evaluate the overall quality of life, including somatic function and walking ability, before and after surgery. The scores were statistically processed using the SPSS 11.5 software package, and the t-test for paired data was used to test the significance of the means, and a statistical difference was considered when P<0.01. Comprehensive efficacy evaluation [3]: excellent: no treatment needed (drug or physiotherapy), ODI < 20, VAS ≤ 3; good: no treatment needed (drug or physiotherapy), ODI < 20, VAS > 3; acceptable: drug or physiotherapy needed, ODI 20-40; poor: drug or physiotherapy needed, ODI > 40. 2 Results Operative time: 35 min to 45 min, mean 40 min Minutes, mean 40 minutes; bleeding volume 40 ml to 100 ml, mean 70 ml; no postoperative complications such as infection, nerve root injury, or dural tear. 33 patients were followed up for a mean of 18 months (3 to 26 months). Patients were evaluated preoperatively, 3 weeks postoperatively, and 12 weeks postoperatively by VAS and ODI. The results showed statistically significant changes in VAS and ODI scores before and after surgery (p<0.01), Table 1; no statistically significant changes in VAS and ODI scores at 3 weeks and 12 weeks postoperatively (p>0.05), Table 2. Overall efficacy evaluation: excellent in 27 cases, good in 6 cases, poor in 2 cases. Some patients were reviewed with CT or MRI to observe the imaging changes before and after surgery. Table 1. Comparison of patients’ self-rating results before and after surgery (`x ± s, n = 35) Preoperative 3 weeks postoperative t-value P VAS 7.62 ± 0.15 2.14 ± 0.69 37. 12 <0.01 ODI 41.96 ± 4.67 15.02 ± 4.77 26.18 <0.01 Table 2. Comparison of patients' self-rating results at 3 weeks postoperative and 12 weeks postoperative (`x ± s, n = 35) (`x ± s, n = 35) 3 weeks postoperative 12 weeks postoperative t-value P VAS 2.14 ± 0.69 2.22 ± 0.56 1.44 >0.05 ODI 15.02 ± 4.77 16.15 ± 3.52 1.54 >0.05 3 Discussion 3.1 Clinical characteristics of high lumbar disc herniation Some foreign scholars have classified T12/L1, L1/2, L2/3 and L3/4 disc herniations as Some scholars abroad have defined high lumbar disc herniation as T12/L1, L1/2, L2/3 and L3/4 disc herniation [4], while others have defined only L1/2 and L2/3 as high lumbar disc herniation [5, 6, 7], and most authors believe that high lumbar disc herniation includes L1/2, L2/3 and L3/4 [8-11]. In the present study, L1/2, L2/3 and L3/4 disc herniations were included. The anatomy of high lumbar discs differs from that of low lumbar discs, and their clinical manifestations also differ greatly from those of low lumbar disc herniations. The upper lumbar spinal canal is mostly oval or sub-triangular in shape, with little epidural fat, a small epidural space, a thin posterior fibrous ring and posterior longitudinal ligament of the disc, short nerve roots, and a nucleus pulposus that can easily break into the spinal canal or even into the dural sac, causing more extensive and severe neurological damage [12]. The clinical manifestations of high lumbar disc herniation are more complex, unlike low lumbar disc herniation which produces more typical symptoms of lumbar and leg pain and body surface localization. Symptoms can manifest as sciatica symptoms, and can also manifest as anterior or medial thigh pain, decreased knee reflexes and knee extension muscle strength, or as pain or even paralysis of the entire lower extremity, with varying degrees of severity and urgency [13]. Sometimes high lumbar disc herniation is combined with low lumbar disc herniation, and its manifestation becomes more complicated, and it is easy to misdiagnose and miss the diagnosis at the early stage of clinical development. Some cases in our group have been misdiagnosed by outside hospitals as low lumbar disc herniation, hip, knee joint or even pelvic and genitourinary system diseases. The diagnosis of high-grade lumbar disc herniation depends on careful physical examination and perfect imaging examination. High lumbar disc herniation should be highly suspected when the symptoms of lumbar and leg pain are heavy, or even the whole lower limb is painful, there is obvious pressure and percussion pain in the spinous process or paraspinal process of the upper lumbar vertebrae, the muscle strength of the lower limb decreases earlier or sooner, the knee reflex is weakened or disappears, and the femoral nerve pull test is positive, and the performance cannot be explained by low lumbar disc herniation. Conventional CT scan is susceptible to leakage due to the influence of segments and levels [14 ], whereas MRI of the lumbar spine can clarify the sagittal images of all discs in T11/S1, so the chance of leakage and misdiagnosis is smaller. 3.2 Minimally invasive treatment of high lumbar disc herniation High lumbar disc herniation, especially above L3/4, is highly symptomatic and progresses rapidly, and unnecessary conservative treatment often aggravates its symptoms and misses its optimal recovery period. In 1997, Foley and Smith developed the microendoscopic discectomy (MED) system via the posterior intervertebral plate, which is a major endoscopic technique in the field of spinal surgery. The development of the Microendoscopic Discectomy System (MED), a major advancement in endoscopic technology in the field of spine surgery, is a major step forward. After more than a decade of clinical application and exploration, MED is not only a classic technique for minimally invasive treatment of simple lumbar disc herniation (low level), but has now been applied to various types of lumbar disc herniation (including extremely lateral type lumbar disc herniation and high level lumbar disc herniation) and lumbar spinal stenosis [ 16, 17 ]. Compared with traditional surgical nucleus pulposus removal, MED has the advantages of less trauma, faster postoperative recovery and shorter hospital stay. 3.3 Surgical access of MED Traditional MED is performed through the intervertebral space, and the dural sac and nerve roots can be exposed by biting off a little of the lower edge of the upper vertebral plate and the upper edge of the lower vertebral plate and removing the ligamentum flavum to complete the removal of the nucleus pulposus. For L1/2 and L2/3 disc herniation, because the volume of the spinal canal at this interval is relatively small, there are many nerve tissues, the epidural space, especially the anterior epidural space, is small, the nerve roots travel a short distance in the spinal canal after exiting the epidural sac, and the position is deep and fixed, so that the nerve roots are not easily pulled apart, and excessive force can easily cause nerve injury, so the approach through the intervertebral space is often difficult. It is often difficult to remove the disc through the intervertebral space. Especially for central disc herniation, pulling may cause injury to the round spinal cord or nerve roots. The transvertebral foramen approach under MED only removes the cortex of the outer edge of the synovial joint, peels off a small amount of intertransverse tissue, and removes the degenerated herniated nucleus pulposus laterally through the foramen under endoscopic surveillance, thus greatly reducing damage to the spinal structures and bleeding. This approach can also be used to remove the nucleus pulposus in extreme lateral lumbar disc herniation. For lateral lumbar disc herniation in L1/2 and L2/3 segments, microscopic endoscopic removal of the nucleus pulposus through the lamina cribrosa is also feasible, with excision of the medial edge of the articular eminence and access from the lateral side of the dural sac and nerve roots to minimize the strain on the nerve roots and dural sac to avoid injury. In this group, all 24 cases of L3/4 disc herniation were completed through the interlaminar approach, 3 of 5 cases of L1/2 disc herniation were completed through the interlaminar approach, 3 of 6 cases of L2/3 disc herniation were completed through the interlaminar approach, and the rest were completed through the intervertebral foramen approach to remove the nucleus pulposus, and all procedures were completed successfully without postoperative complications such as infection, nerve root injury, or dural tear. Both approaches are effective ways to complete the removal of the nucleus pulposus. The author concludes that for herniation obviously on one side and the symptoms are also unilateral, the translaminar approach is optional, with the advantage that the operation is the same as the posterior microendoscopic removal of the nucleus pulposus for low lumbar disc herniation, with easy removal of the nucleus pulposus, less bleeding, and easy to master, but the operation should be done carefully and gently to avoid nerve root or spinal cord injury caused by rough traction. For very lateral type high lumbar disc herniation, or large central type disc herniation, the intervertebral space approach is often inadequate due to fear of nerve injury, making it difficult to remove the nucleus pulposus. In this case, the transvertebral foraminal approach is an ideal option to remove the bone at the outer edge of the articular process, tilt the working channel, and remove the herniated degenerated nucleus pulposus from the lateral side via the foramen under endoscopic surveillance. The foraminal approach removes only the outer edge of the synovial joint and strips away a small amount of intertransverse tissue, so it is less destructive to the spinal structures, reduces bleeding, and more importantly, avoids pulling on the dural sac and nerve roots. The following methods can be used to prevent injury: (1) use continuous epidural anesthesia, so that the patient may report pain or numbness in the corresponding lower extremity when the nerve root is encountered during the operation. ② When stripping the soft tissue between the transverse processes to reveal the intervertebral disc, first use a miniature nerve root stripper to gently probe and pull it cephalad along with the surrounding tissues, without deliberately looking for free. ③ Skilled microscopic hemostasis, keeping the operative field clear, and eliminating operation in a pool of blood are important prerequisites to avoid injury to the nerve root [17 ]. In conclusion, with the advancement of minimally invasive techniques, endoscopic minimally invasive surgical treatment has occupied a very important position in the field of surgery. Posterior microendoscopic nucleus pulposus removal is a feasible method for the treatment of high-grade lumbar disc herniation.