Posterolateral Percutaneous Endoscopic Discectomy with Partial Pediculotomy for the L1-L2 High-Grade Downward Migrated Disc Herniation

Percutaneous endoscopic discectomy (PED) is one of the most useful minimally invasive surgery for lumbar disc herniation (LDH) (1,2). Especially, high-grade migrated fragments are difficult to treat with the standard posterolateral PED (PLPED) technique (3,4). PED with a high-speed drill is a minimally invasive method of approaching the deep narrow lumbar space (5-8). This paper presents a successful case of PLPED with partial pediculotomy for a high-grade downward migrated fragment and discusses a hemostatic technique for severe bleeding.


Introduction
Percutaneous endoscopic discectomy (PED) is one of the most useful minimally invasive surgery for lumbar disc herniation (LDH) (1,2). Especially, high-grade migrated fragments are difficult to treat with the standard posterolateral PED (PLPED) technique (3,4). PED with a high-speed drill is a minimally invasive method of approaching the deep narrow lumbar space (5)(6)(7)(8). This paper presents a successful case of PLPED with partial pediculotomy for a high-grade downward migrated fragment and discusses a hemostatic technique for severe bleeding.

Case Report
A 72-year-old man had severe untreatable lumbago and left femoral radicular pain for 6 months. His health condition was poor with chronic renal failure requiring dialysis 3 times per week, hypertrophic cardiomyopathy, and obstructive ventilation impairment .The initial physician referred the patient to us to undergo a minimally invasive spine surgery.
During his first visit, the patient's numeric rating scale (NRS) scores were 8/10 for low back pain and 8/10 for left front femoral pain. His leg pain increased after 10 minutes of slow walking, so he needed a wheelchair. Neurological examination revealed normal deep tendon reflexes. His thigh circumference was asymmetrical (right, 35.5cm; left, 35.0cm). Owing to his pain, he could not get into a prone position for examination with the femoral nerve stretch test. The straight leg raising test result was negative bilaterally.

Journal of Head Neck & Spine Surgery
On sagittal T2-weighted magnetic resonance imaging (MRI),a high-grade downward migrated disc was observed at the L1-L2 level on the left side ( Figure 1a). The axial view at the L2 pedicle midline level showed a large fragment impinging the L2 nerve root (Figure 1b).   PLPED with partial pediculotomy under local anesthesia was planned to decompress the left L2 nerve root. Our anesthesiologist performed deep sedation of the patient. The patient was placed in a prone position, and the puncture point under fluoroscopy was simulated prior to the calculation of data (9). An 8mm skin incision was made 5cm to the left of the midline. The standard PLPED procedure was started after local anesthesia. Owing to the L1-L2 foraminal severe stenosis, we selected the outsidein technique. The adverse walking technique could be used to approach the crossing point of the superior facet and transverse process (Figure 2a). Partial pediculotomy was started from this point, and a quarter of the craniomedial portion was drilled (Figure 2b) for the total fragmentectomy ( Figure 2c) (10). We could decompress the L2 nerve root from the L1 endoplate level to under the midline of the L2 pedicle (Figure 2d).
The operative time was 2 hours; 100ml of bleeding from the L1 AEVP due to injury by the tip of the Beak-type cannula took 30min to control. We first attempted the standard hemostatic techniques of increasing the irrigation pressure (100 to 110cm H2O for 3min) several times and compression the bleeding point with rigid dissector but did not succeed the hemostasis. We then attempted the techniques for such a vigorous bleeding situation include slow cannula rolling and bleeding point compression by a flexible bipolar device with hemostatic cotton materials. We finally achieved the hemostasis and placed a drainage tube. Little outflow stayed only in the tube, which was withdrawn the next morning without hematoma formation.
The patient did not have any dysesthesia and paresis. The time to ambulation was 2 hours, and his hospital stay was 7 days. The NRS score of his affected leg improved from 8 to 1 after 2 months. In the next morning, his wound pain NRS score was 1. The axial view of the MRI scan (Figure 1c) showed that the migrated fragment was completely removed.

Discussion
The standard treatment for higher-level lumbar disc herniation is conventional discectomy with some fusion after facetstomy (11). Nowadays, many types of minimally invasive percutaneous pedicle screw systems are available (12). Owing to the poor general condition of our patient, we selected the operative procedures suitable for local anesthesia were limited. Interlaminar PED (ILPED) with partial laminectomy (7,8) and PLPED with partial pediculotomy are the best minimally techniques for patients with poor general conditions. The major difference between ILPED and PLPED with partial pediculotomy is the direction of the operative approaches. ILPED accesses from dorsal side of vertebral laminae, thereby even combined with laminectomy the migrated fragment is still covered with neural structures. On the other hand, PLPED with partial pediculotomy can directly expose the migrated fragment covering neural structures. In other words, as the migrated fragment protects underneath neural structures, we can safely drill the inner cortical bone layer of the pedicle. Additionally, the width of spinal canal at high vertebral level (ex. L1-L2) is narrower than that at low vertebral level (ex. L5-S1) (13). Consequently ILPED at high vertebral level requires more skillful technic. Our case was affected at L1-L2 vertebral level and the migrated fragment extended lateral part of the spinal canal (Figure 1b), we therefore planned to perform the PLPED with partial pediculotomy.

Journal of Head Neck & Spine Surgery
Your next submission with Juniper Publishers will reach you the below assets The disadvantages of PLPED under the situation of severe foraminal stenosis include the possibility of complicating the exiting nerve injury and bleeding from the AEVP. As the beaktype cannula has a wider view than the square-type cannula, we changed the square-type cannula with the beak-type cannula to complete the decompression of the L2 nerve root. When the joystick maneuver was used to observe the narrow disc space, the tip of the beak-type cannula injured the L1 AEVP. The flexible bipolar unit is the only instrument for hemostasis with the PED system. We needed 30min to control 100ml of bleeding from the AEVP. The robotic general surgery system already has many useful instruments developed for dissection and coagulation (14). One of the urgent needs of PED surgeons is the development of a bipolar dissector for fine manipulation like under microscopic surgery.
On the basis of this case of higher-level migrated lumbar disc herniation, PLPED with partial pediculotomy is a useful procedure for patients with poor general conditions. For the appropriate development of this procedure, the PED system requires new devices to control the bleeding from the AEVP.