This prospective study was approved by the Ethics Committee of West China Hospital, Sichuan University and was registered with the Chinese Clinical Trial Registry (ChiCTR1800019551). The study was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants prior to surgery.
69 patients with single-level LLSC stenosis simultaneously occurred in both zone 1 and 2 from November 2018 to April 2019 were enrolled. All of the patients were performed with TPLF-PELD by one endoscopic spine surgeon (KQQ). The characteristics of 69 patients are shown in Table 1. LBP occurred in 5 patients (7.2%), muscle weakness of the lower limbs in 1 patients (1.4%), extremity radiating pain with/without gluteal pain in 62 patients (89.8%) and neurogenic intermittent claudication in 53 patients (76.8%). All patients have no operation history.
Table 1
characteristics of patients undergoing accurate two-time percutaneous lumbar foraminoplasty (TPLF) and percutaneous endoscopic lumbar decompression (PELD)
Patient data | |
Age at presentation, yrs | 66.1 ± 7.5*(range, 42–91 years) |
Male gender | 40 (57.9%) |
Occupation | |
Sedentary | 18 (26.1%) |
Light work | 30 (43.4%) |
Heavy manual work | 21 (30.5%) |
Duration of symptoms, mo | 20.9 ± 5.6* (range, 4–90 months) |
Level of involvement | |
L3/4 | 0 (0%) |
L4/5 | 57 (82.6%) |
L5/S1 | 12 (17.4%) |
Side of LLSC stenosis | |
left | 39 (56.5%) |
right | 30 (43.5%) |
Patients with comorbidities | |
Diabetes mellitus | 27 (39.1%) |
Smoking | 24 (34.8%) |
Alcohol consumption | 12 (17.4%) |
Osteoporosis | 22 (31.8%) |
Hypertension | 27 (39.1%) |
Use of antidepressants | 1 (1.4%) |
Physical treatment and medications | |
Steroid intake | 19 (27.5%) |
Nerve blocks/epidural blocks | 11 (15.9%) |
*Data represented as mean (± standard deviation) |
Included for study were patients who (1) manifested as single nerve root symptom, such as single side extremity pain, numb or weakness, with or without LBP. (2) with full preoperative radiological information. The method of distinguishing stenotic zone has been described in previous study (Fig. 1)[8]. Stenosis in zone 1 was diagnosed by sagittal T2-weighted MRI scans through paracentral region: the anteroposterior distance less than 1 mm. Stenosis in zone 2 was diagnosed by axial bone window CT scans: the anteroposterior distance in lateral recess region less than 3 mm. The radiological diagnosis should be identical to clinical symptom. Preoperative blocking of the nerve root could be applied in some intractable cases. (3) with obvious symptom (preoperative leg pain Visual Analogue Score (VAS) score over 6) after over 3 months’ invalid conservative treatment. (4) was informed consent for our study and agreed to accomplish all follow-up.
Excluded for study were patients who (1) have lumbar segmental instability indicated by preoperative lumbar flexion-extension X-Ray. (2) combined with lumbar central canal stenosis. (3) was diagnosed as pure lumbar disc herniation. (4) high-grade lumbar spondylolisthesis with multi-level spinal stenosis. (5) with high iliac crest, the peak of iliac crest exceed lower quarter of L4 vertebral body, which hindered puncture in L5/S1. (6) with surgical contraindication.
Special Surgical Tools
Specially designed Depth-Limited Trephine for foraminoplasty by ourselves (ZL 201621149959.2)[12]: consist of trephine, handle and stopper (Fig. 2). The saw tooth of the trephine has no difference with traditional trephine. The diameter of trephine has different sizes: 6.5 mm, 7.5 mm and 10 mm. But the total length of the trephine is same: 243 mm. In the proximal end of the trephine, 17 circular grooves are designed. The first groove is 165 mm away from the distal end of trephine and there’s the interval of 2 mm in the next adjacent grooves. The depth of foraminoplasty was accurately controlled and limited by the stopper located in the trailing end of the trephine. The stopper is locked in one of the grooves, and then the trephine cannot advance. The exact foraminoplasty depth we need can be adjusted by the location of the stopper. The handle can be easily assembled and unassembled from the trephine.
Surgical Techniques
All TPLF-PELD procedures employed by the author were essentially a classic Thessys technique popularized by Hoogland[9]. The procedures were performed under local anesthesia in the prone position on a radiolucent table using C-arm fluoroscopy. An 1.6 mm Spinal Guiding Cannulas (SPINENDOS, Germany) was inserted into the safe zone of Kambin’s triangle. The puncture point were 12 ± 2 cm from midline according to the size of body and surgical level, 2–5 cm from horizontal line of target intervertebral disc. After infiltrating 15–20 ml of 0.5% lidocaine in the subcutaneous soft tissue, around SAP and intervertebral foramen, the needle was replaced with a 0.7-mm-diameter guiding wire. A Dilator 2-channels (7.0, 6.3 or 5.3 mm-diameter) was passed over the guiding wire under fluoroscopic control. Trephine Protection Tube (6.5, 7.5 or 8.5-mm-diameter) were introduced over the obturator until it was placed in proper position. The Depth-Limited Trephine designed by ourselves(6.5, 7.5 or 8.5-mm-diameter, selected based on pathologic condition) was used to perform two-time foraminoplasty, which was facilitated by changing the trajectory of trephine to aim for the different compressive portion. The details of the two foraminoplasty procedures are shown in Table 2, Fig. 3.
Table 2
Details of the two foraminoplasty procedure
| Target region | The inclination of the trephine | Removed section | The depth of foraminoplasty |
In lateral view | In AP view |
The first foraminoplasty | Retrodiscal space (Zone 1) | From the tip of superior articular process (SAP) to the posterior rim of the upper endplate of distal vertebral | From the tip of SAP to midpoint of upper endplate of distal vertebral body | Upper-medial-ventral part of facet joint which comprise tip and upper-ventral part of SAP, a part of inferior articular process (IAP) and a small ventral part of laminar. | Limited to 10–12 mm controlled by the special designed trephine |
The second foraminoplasty | Upper bony lateral recess (zone 2) | From the tip of SAP to the cross-point of middle pedicular line and the posterior surface of vertebral body | From the tip of SAP to midpoint of middle pedicular line | Lower medial-ventral part of SAP | Limited to 12–14 mm controlled by the special designed trephine |
In the first foraminoplasty, the scale of the resection can be slightly adjusted based on different pathologic conditions. After the first foraminoplasty, radiofrequency probe was endoscopically used (Working Tube With Elevator Tip, ID 7.2 mm, OD 8.0 mm, L178 mm; Spinal Endoscope, 30° direction of view, WC 3.75 mm OD 6.3 mm, WL 181 mm) to control bleeding and adequate exposure bony structures by resecting adherent soft tissue. The margin of exposure should from upper-ventral surface of SAP to lower-ventral surface of SAP and upper surface of pedicle. And then, a 1.5 mm Kirschner wire was knocked in the aiming site. After take out the Spinal endoscope, the second foraminoplasty was then performed after positioning the Trephine Protection Tube over the Kirschner wire and adjusting its tip embracing the ventral-basial part of SAP. In some sever stenosis cases, in order to preventing injuring nerve roots, we only entered the trephine into three quarters of SAP and break the involved SAP instead of completely resecting by trephine. For the two foraminoplasty procedures, the trephine need to be underdraught aiming to resecting more SAP.
After that, the Trephine Protection Tube was replaced with the Working Tube With Elevator Tip. And then, high-speed drilling was used to resect remaining hypertrophied SAP or IAP if needed. The Working Tube was adjusted to find and convenient for completely remove decompressive factors: the hypertrophied ligamentum flavum, facet joints and anterior herniated disc. To reduce the recurrence rate of lumbar disc herniation (LDH), we did not perform discectomy (only decompress dorsal compressive factors) for patients whose annulus was not damaged. The compressed nerve root was decompressed and explored from the distal-end to near-end, especially for the attachment point of annulus. The surgeon can see and mobilize both the traversing nerve root and exiting nerve root under endoscopic visualization. Free movement of dural sac and nerve root can be a sign of complete decompression. Epidural bleeding was controlled with a radiofrequency probe under saline irrigation.
Each operation duration, times of intraoperative C-arm fluoroscopy use and complication were recorded. Every patients were asked to wear lumbar protection devices for 2–4 weeks after the operation and to take muscle function exercise in 2 weeks after the operation.
Outcome Assessment
Outcomes were evaluated by follow-up interviews (WY) at 3 months and final follow-up after surgery. We used LBP and leg pain VAS and Oswestry disability index (ODI) to evaluate the outcomes of surgery. Function outcomes were assessed by using the modified Macnab criteria[13]. All patients routinely undergo 3D-reconstructive CT scans in 2 days after the operation, undergo MRI and CT scans in 3 months to confirm the complete decompression. In the final follow-up, patients undergo CT to confirm the no recurrence of LLSC stenosis, and flexion-extension X-Ray to observe lumbar stability. All postoperative radiological exams are permitted to be discharged.
Statistical analysis
Statistical analysis were performed with SPSS 23 software(SPSS Inc., Chicago, IL). Preoperative and postoperative (3 month and final follow-up) VAS and ODI scores were analyzed with ANOVA. P < 0.05 was considered as significant.