Technical Considerations of the Transforaminal Approach for Lumbar Disk Herniation

Transforaminal full endoscopic lumbar diskectomy (TELD) is a typical minimally invasive surgery, with the associated benefit of decreased possibility of anatomic structural injury, and is an effective alternative to open diskectomy. Among the various endoscopic spinal surgical techniques currently available, TELD is the most basic and traditional surgery that can be performed through the transforaminal route; it has been used for >30 years. Recently, with the advancements in surgical techniques, TELD has been successfully performed for patients with lumbar disk herniation of different types. However, beginner surgeons are unfamiliar with the anatomy of transforaminal endoscopic surgery and this surgery has a steep learning curve to date. If not well prepared, operators may experience complications that require reoperation in the early stages. These complications may include symptomatic incomplete decompression, exiting nerve root injury, dural tearing, and rarely, hematoma, infection, and visceral injury. Here, we propose several technical guidelines for TELD to increase the possibility of successful lumbar diskectomy and to reduce the incidence of complications. The first step is the accurate anatomic understanding of Kambin triangle and determining the appropriate endoscopic access angle, depending on the type of disk herniation. The second step is to determine a safe and easily accessible entry point and then landing and docking the working sleeve as close to the target as possible without causing exiting nerve root injury. The third step is complete decompression of the symptomatic nerve with free mobilization of the neural tissue. The final step involves performing foraminoplasty using an advanced technique to overcome the limitations associated with TELD in difficult cases.

Full Endoscopic Lumbar Diskectomy for Lumbar Disk Herniation in the Presence of a Low-Lying Cord

BACKGROUND

The distal extent of the spinal cord is most often at the level of the L1 or L2 vertebral body. In rare cases, a low-lying cord extends more distally. In this scenario, pathology that normally causes radiculopathy may cause myelopathy due to compression of the cord rather than nerve roots of the cauda equina.

CASE DESCRIPTION

A 40-year-old man presented with progressive leg pain, sensory changes, hyperreflexia, and gait disturbance 1 month after a fall. The patient was myelopathic and had central L1/2 and L2/3 disk herniations. After unsuccessful unilateral laminotomy bilateral decompression, it was decided that an endoscopic diskectomy would be the best technique to remove the disk herniation without trauma to the cord or destabilizing the spine to require fusion. A percutaneous endoscopic lumbar diskectomy at L1/2 was performed under local anesthesia. The patient's leg pain, sensory changes, hyperreflexia, and gait disturbance resolved after surgery, and he was doing well at 6 months' follow-up.

CONCLUSIONS

In patients with spina bifida occulta who present with myelopathy, lumbar disk herniation should be considered if the patient has a low-lying cord. This is the first report of percutaneous endoscopic lumbar diskectomy for lumbar disk herniation in the presence of a low-lying spinal cord. We have demonstrated that this approach can treat this condition effectively and safely.

Could the Splitting of the Annulus During Percutaneous Endoscopic Lumbar Diskectomy (PELD) Be a Culprit for Recurrent Disk Herniation?: An Analysis of the Reherniation Pattern After PELD

OBJECTIVE

To explore which preoperative radiologic variables have propensity for reherniation and to evaluate whether the inherent annulus splitting procedure during percutaneous endoscopic lumbar diskectomy (PELD) could prompt reherniation, we assessed the correlation between the anatomic location of annular penetration and reherniation.

METHODS

Three hundred and fifty patients who underwent PELD for central or subarticular disk herniation through a transforaminal approach were followed-up for at least 24 months. Fifty-four subjects that were reoperated for recurrent herniation were allocated as the reherniation group and the other 296 subjects were allocated as the non-reherniation group. The numerical rating scale score, another lumbosacral disk herniation (LDH) lesion in addition to the PELD level (another LDH), location (central or subarticular) and severity of LDH (protrusion or extrusion), and tear of the posterior longitudinal ligament (PLL) were compared between the 2 groups to identify which variables could be predictive factors for reherniation. To assess the influences of PELD on reherniation, location and severity of reherniation were compared with those of initial herniation.

RESULTS

The location at the subarticular region and the existence of a concomitant PLL tear during initial LDH were significantly related to subsequent reherniation. The location and severity of these reherniations were significantly retained when compared with those of primary herniation.

CONCLUSIONS

PLL tear and subarticular herniation were significantly related to recurrent disk herniation. Reherniation patterns after PELD generally matched those of primary herniation. The annulus penetrating step during PELD did not increase the risk of reherniation.

Learning Curve for Percutaneous Endoscopic Lumbar Diskectomy in Bi-needle Technique Using Cumulative Summation Test for Learning Curve

BACKGROUND

The purpose of this study was to determine the number of cases needed to achieve the level of competence for percutaneous endoscopic lumbar diskectomy (PELD) via the bi-needle technique using the cumulative summation test for learning curve (LC-CUSUM).

METHODS

A retrospective design was used. We included 60 patients who underwent a single-level PELD via the bi-needle technique performed by a single surgeon. The surgeon had 5 years of experience in open surgery including the transforaminal endoscopic spine system and Yeung endoscopic spine system but no experience in the bi-needle technique. Surgery success was defined as an operative time <60 minutes, and the acceptable procedure was completed within 3 times of C-arm fluoroscopies. The LC-CUSUM was used to analyze the data.

RESULTS

The average operative time for PELD via the bi-needle technique was 58.3 ± 12.4 minutes. The mean operative time was 65.7 ± 12.1 minutes in the early learning period (30 cases) and 51.0 ± 7.5 minutes in the late learning period (30 cases) (P < 0.05). On the basis of the evaluation indexes of the operative time and radioactive exposure, the LC-CUSUM signaled proficiency for the bi-needle technique at the 50th-54th operation. Seven cases of complications were observed during the whole learning process, with 6 in the early period and 1 in the late period (P < 0.05).

CONCLUSIONS

The novel bi-needle technique is safe and effective for PELD with appropriate patients, and the learning curve is acceptable. A substantial learning period (50-54 cases) is needed before a spine surgeon can master the bi-needle technique.

A Modified Percutaneous Endoscopic Technique to Remove Extraforaminal Disk Herniation at the L5-S1 Segment

OBJECTIVE

To introduce a modified percutaneous endoscopic lumbar diskectomy (PELD) technique to remove extraforaminal disk herniation at the L5-S1 segment, including the technical essentials and preliminary results.

METHODS

The geometric parameters of the transverse process, facet joint, and sacrum (TFS) space based on imaging examination were measured in 100 common patients. The technical essentials, including working cannula placement and disk removal involved in the technique, were described. Ten cases (7 men and 3 women) with extraforaminal disk herniation at L5-S1 were surgically treated with the PELD technique through the TFS space from June 2015 to March 2017.

RESULTS

The maximum diameter of the TFS space varied from 2.73 to 11.81 mm (6.84 ± 2.01 mm) on the left and 3.00 to 10.47 mm (7.02 ± 2.05 mm) on the right. The distance of possible skin entry points from midline varied from 33.28 to 84.18 mm, and the distance of external iliac vessels to skin varied from 70.05 to 119.14 mm. All 10 patients who underwent the modified PELD technique were back to previous activities in 1 month. Visual analog scale (VAS) or Oswestry Disability Index (ODI) scores reduced to 2.5 ± 2.0 or 25.4 ± 10.8 from 7.5 ± 1.3 or 75.2 ± 13.3, respectively, 1 day after operation. At 30 days after the operation, the VAS score was 1.0 ± 0.6 and ODI score was 10.2 ± 3.2. No neurologic deficit or surgical site infection occurred.

CONCLUSIONS

We introduced a modified PELD technique to remove extraforaminal disk herniation at the L5-S1 segment. This technique was less invasive, effective, and safe. We also summarized a detailed protocol to identify and remove the herniated disk for nerve protection.