A comparative study of percutaneous endoscopic interlaminar discectomy and transforaminal discectomy for L5-S1 calcified lumbar disc herniation

This research obtained the support of the Ethics Committee of our institution and informed consent of all patients. From August 2016 to August 2020, we collected 54 consecutive patients with L5-S1 CLDH treated with PEID and PETD in our hospital. These patients were divided into PEID (n = 28) and PETD (n = 26) groups according to the surgical methods. The inclusion criteria were as follows: 1) symptoms of pain and numbness of lower limbs; 2) L5-S1 CLDH confirmed by preoperative lumbar X-ray, computed tomography (CT) and magnetic resonance imaging (MRI); 3) failure of conservative treatment or no significant improvement in symptoms for greater than 3 months; and 4) the follow-up time was greater than 12 months. The exclusion criteria were as follows: 1) multisegmental lesions; 2) noncalcified lumbar disc herniation; 3) lumbar spinal stenosis, lumbar instability, lumbar tuberculosis, lumbar infection or spinal tumor. A percutaneous transforaminal endoscopic spine system (Joimax, Karlsruhe, Germany), tip-flexible bipolar radiofrequency system (Elliquence LLC, USA), ultrasonic osteotome (SMTP, China) and endoscopic instruments (MaxMorespine GmbH, Germany) were used.

All patients were placed on the operating table in the prone position after general anesthesia. The surgical segment was identified by fluoroscopy on an X-ray machine. After marking the puncture site on the body surface, routine disinfection was performed. The puncture point was anesthetized with local infiltration of 0.5% lidocaine. The puncture needle was inserted in 1.0 cm beside the posterior midline. The needle position was confirmed by fluoroscopy of a C-arm X-ray machine. A 0.7-cm longitudinal incision was made at the skin mark. The skin, subcutaneous tissue and lumbodorsal fascia were incised in turn. The dilating tube was placed to the ligamentum flavum. The working cannula and endoscope were inserted along the dilating tube (Fig. 1A). After checking the operating system, the light source was connected, and the operation was performed under continuous saline irrigation. Under the endoscope, the ligamentum flavum was cut by scissors (Fig. 2A). After reaching the epidural space, the lateral dural sac and nerve root were exposed. A blunt dissector was used to expose and separate the calcified disc and herniated nucleus pulposus. The locations of the nerve root, dural sac and herniated disc were explored. The degree of calcification and size of the herniated disc were carefully confirmed. Under the endoscope, the calcified and herniated disc tissue was removed by an ultrasonic osteotome (SMTP, China) (Fig. 2B), and the herniated free nucleus pulposus was removed using nucleus pulposus forceps (Fig. 2C). Under direct vision, no obvious compression of the nerve root and dural sac was observed (Fig. 2D). During the operation, bipolar radiofrequency ablation was used to adequately stop bleeding. After removing the working cannula, the incision was closed intradermally and covered with a sterile dressing. All patients underwent CT and MRI examinations before (Fig. 3A-D) and after (Fig. 3E-H) operation.

The patient was placed in a prone position after local anesthesia, and the responsible segment was identified by C-arm X-ray fluoroscopy. The level of responsible intervertebral space and the posterior midline line were marked. Routine disinfection and sheet laying were performed. The puncture site was set at 12 ~ 14 cm next to the posterior midline, and the puncture point was anesthetized with 0.5% lidocaine injection. The 18-G puncture needle was inserted in the marked puncture site, and the needle slid along the lateral aspect of the superior articular eminence and entered the spinal canal through the intervertebral foramen. It was confirmed that the puncture needle was located in the midline on the anterior radiograph and the posterior upper edge of the vertebral body on the lateral radiograph by fluoroscopy with a C-arm X-ray machine. After inserting the guide wire, a puncture needle was removed. The skin was cut to approximately 0.7 cm, and the expanding cannula was inserted gradually. Finally, the bevelled cannula was inserted along the dilatation tube. When the working channel was difficult to insert, foraminoplasty was performed, in which by a trephine was used to remove the anterior part of the superior articular process. Then the working cannula was successively introduced. The position of the working cannula was confirmed under fluoroscopy on a C-arm X-ray machine (Fig. 1B). The working cannula was flushed with 3000 ml of saline. A blunt dissector was used to reveal and separate the calcified disc and herniated nucleus pulposus. The calcified disc was cut with an ultrasonic osteotome (SMTP, China) (Fig. 2E). Subsequently, a nucleus pulposus forceps was used to remove the calcified disc and herniated nucleus pulposus under an endoscope (Fig. 2F). The working cannula was moved appropriately. The nerve roots and dural sac were moved by a blunt dissector (Fig. 2G). The nerve roots and dural sac were then explored for relaxation, and no protruding discs compressed the nerve roots and dural sac. The bipolar radiofrequency ablator was used to perform fibrous annuloplasty. Bleeding points were carefully explored and given adequate hemostasis (Fig. 2H). The nerve root and dural sac were confirmed to be free of compression, and no bleeding points were evident. The working cannula was removed. Then, the incision was sutured intradermally and covered with a sterile dressing. The CT and MRI examinations of all patients were done before (Fig. 4A-D) and after (Fig. 4E-H) operation.

All patients were successfully operated on by a trained and experienced spine surgeon in our hospital. We followed up all 54 patients (28 in the PEID group and 26 in the PETD group). The demographic characteristics (age, sex, BMI, duration of symptoms, type of calcification, location of calcification and follow-up time) of the two groups were significantly similar as shown in Table 1. In the PEID group, the operative time, intraoperative fluoroscopy times, postoperative hospital stay, intraoperative blood loss and complication rate were 64.61 ± 5.60 min, 2.93 ± 0.90 times, 2.57 ± 1.14 days, 13.75 ± 4.44 ml and 7.14%, respectively. In the PETD group, the operative time, intraoperative fluoroscopy times, postoperative hospital stay, intraoperative blood loss and complication rate were 85.58 ± 8.52 min, 13.35 ± 2.30 times, 2.58 ± 1.07 days, 13.65 ± 3.62 ml and 7.69%, respectively. PEID was superior to PETD in terms of operative time and intraoperative fluoroscopy times, but no significant difference in intraoperative blood loss, postoperative hospital stay or incidence of complications were noted as shown in Table 2.