Presented here is a novel technique of C-arm free transtubular posterolateral decompression for lumbar foraminal stenosis and lateral disc herniation under O-arm navigation.
We report a novel technique for C-arm free transtubular L5 nerve decompression under CT-based navigation to reduce the radiation hazard. This procedure is performed under general anesthesia and neuromonitoring. The patient is placed in a prone position on an operating carbon table. A navigation reference frame is placed percutaneously into the contralateral sacroiliac joint or spinous process. Then, CT scan images are obtained. After instrument registration, the L5-S1 foraminal level is confirmed with a navigated probe, and the entry point is marked. Using an approximately 2 cm skin incision, the subcutaneous tissue and muscles are dissected. The navigated first dilator is aimed at the L5-S1 Kambin's triangle, and sequential dilation is performed. The 18 mm tube is used and fixed to the frame. The bone around the Kambin's triangle is removed with a navigated burr. For lateral disc herniation, the L5 nerve root is identified and retracted, and the disc fragment is removed. The navigation-guided tubular endoscopic decompression is an effective procedure. There is no radiation hazard to the surgeon or the operating room staff.
Diagnosis and surgeries for lumbar foraminal stenosis (LFS) and lumbar lateral disc herniation (LLDH) at the L5-S1 level are challenging for spine surgeons because of this level's unique structure1. The iliac crest, broad L5 transverse process (TP), small space between the sacral ala and the L5 TP, and osteophytes make the operating window very narrow2. If the bony resection is not enough, inadequate decompression to the L5 nerve root may lead to residual symptoms. Massive bony removal causes postoperative instability. These issues limit surgeons' competencies with foraminal/extraforaminal L5 root decompression. Several reports have shown good results with minimally invasive spine surgeries, such as microscopic or endoscopic procedures in this area to decompress the L5 nerve root3,4. Recently, the use of navigation for foraminal decompression of the L5 root has been reported with good surgical outcomes5.
Fully endoscopic discectomy is becoming popular for removing lateral lumbar disc herniation6. Furthermore, microendoscopic procedures in combination with navigation can help the surgeon to decompress the L5 root with precision2. Usually, these techniques require intraoperative C-arm usage. The goal of this method is to decompress the L5 root precisely with minimum bony resection without a C-arm.
The indications for this technique are extraforaminal lumbar disc herniation and herniation/stenosis of the lateral half of the foraminal lumbar disc. The contraindications are herniation/stenosis of the medial one-third of the foraminal lumbar disc because the scope cannot reach the targeted area2.
This study was approved by the ethics committee of Okayama Rosai Hospital (No. 305).
1. Patient history taking
2. Physical examination
3. Evaluation of radiograms (XP) and magnetic resonance imaging (MRI)
Figure 1: Preoperative radiograms and MRI. (A) Lateral extension radiogram, (B) Lateral flexion radiogram, (C) Parasagittal T2 weighted MRI image, (D) Coronal T2 weighted MRI image, (E) Axial T2 weighted MR imaging at the L5-S1. The arrow indicates FLDH. Please click here to view a larger version of this figure.
4. Evaluation of computed tomography (CT) and MRI-CT fusion images
Figure 2: Preoperative CT. (A,B) Parasagittal reconstruction CT, (C) Coronal reconstruction CT, (D) Axial CT at L5-S1. The white arrows indicate calcified FLDH; a black arrow shows an osteophyte. Please click here to view a larger version of this figure.
Figure 3: CT MRI fusion images. (A) Posterior view, (B) Posterolateral view. The white arrow indicates FLDH. Please click here to view a larger version of this figure.
5. Patient positioning and neuromonitoring (NM)
6. Intraoperative CT scan and spinal navigation
Figure 4: Neuromonitoring, O-arm, and navigation. (A) Neuromonitoring, (B) O-arm, (C) Navigation. Please click here to view a larger version of this figure.
7. Navigated instrument registration
8. Incision and muscle dissection
Figure 5: Skin incision and sequential dilation. (A) Navigated pointer, (B) Navigation monitor, (C) Tubular retractor. Please click here to view a larger version of this figure.
9. Bone resection with the navigated high-speed burr
Figure 6: Navigated high-speed burr. (A,B): Intraoperative image, (B): Navigated high-speed burr. Please click here to view a larger version of this figure.
10. Endoscopic disc resection
Figure 7: Nerve root decompression. (A) Endoscope image; identifying and decompressing the L5 root (white arrow); the inter-vertebral foramen is widened by burring down the osteophytes with the help of a navigated burr. (B) Navigation monitor; during operation, the surgeons can view the one monitor indicating four pieces of information simultaneously: the surgical field, intraoperative neuromonitoring, intraoperative navigation, and microendoscope view. Please click here to view a larger version of this figure.
11. Skin closure
Figure 8: Postoperative images. (A) Axial CT image at L5-S1, (B) Parasagittal reconstruction CT, (C) Axial T2 weighted MR imaging at L5-S1. The white arrows indicate the decompression area. Please click here to view a larger version of this figure.
Eight cases (four men, four women) underwent surgery using this new technique. The average age was 72.0 years, and the average follow-up period was 1.5 years. There were five patients with L5/S1 foraminal stenosis, two patients with L5/S foraminal disc herniation, and one patient with L3/4 foraminal disc herniation. We could perform all surgeries without a C-arm. The average surgical time and blood loss were 143 min ± 14 min and 134 ± 18 mL, respectively.
The average recovery percentage obtained using the Japanese orthopedic association (JOA) score (back pain evaluation)8 was 72.3% (57%-88%). The visual analog scale (VAS) for leg pain was reduced from 63 mm to 12 mm on average. There were no surgical complications. None of the patients needed a revision surgery due to residual pain (Table 1).
Man | 4 |
Woman | 4 |
Age (year) | 43-82 (average 72.0) |
Surgical time (min) | 143 +/- 14 |
Intraoperative blood loss (mL) | 134 +/- 18 |
JOA recovery (%) | 57-88 (average 72.8) |
Complication | No |
Table 1: Representative results of navigational decompression at L5-S1.
L5 radicular symptoms are caused mainly by L4-L5 disc herniation or stenosis. These symptoms may also occur due to L5 lumbar foraminal stenosis or L5-S1 lateral lumbar disc herniation (LLDH)9. Of all the symptomatic lumbar disc herniations, L5-S1 FLDH accounts for approximately 3%10. For L5-S1 foraminal lesions, a posterolateral or transforaminal approach is recommended. For this approach, there are three main techniques, such as the microscopic, tube with endoscopic, and fully endoscopic approaches. Microendoscopic lumbar discectomy (MED) with a tube was introduced by Foley in 199711. This MED system uses a 16 mm or 18 mm tube with a small endoscope. Recently, spinal navigation has become more popular due to advanced technology12. However, spinal navigation has been applied mainly for spinal fusion13 because the bony structure is easily recognized in the navigation monitor.
Endoscopic-assisted decompression for lumbar canal stenosis was first reported in 200714. With this technique, the central canal stenosis was decompressed through a unilateral approach with a 25° angled scope. Lateral lumbar disc herniation was also treated with endoscopically assisted open removal15. However, C-arm is mandatory to approach to the exact location with these techniques.
With the microscopic decompression technique for LLDH, the skin incision is relatively long, and foraminal disc herniation is difficult to remove because it does not have adequate angle scope. The image quality of the microscope is very clear, but the instruments may disturb the surgical field compared with the endoscopic procedure. The significant removal of the facet joint may lead to postoperative spinal instability and may further accelerate the rate of degeneration16. On the contrary, limiting the bony removal to prevent instability may end up in inadequate nerve root decompression. Among them, the fully endoscopic transforaminal approach to L5-S1 foramen is one of the best options for these lesions because of its minimal invasiveness6. However, this technique has a steep learning curve, the navigation is not available, and a high iliac crest may disturb the transforaminal approach17.
With our new technique, O-arm navigation gives the minimally invasive surgeons 3D image guidance and, thus, helps in the accurate removal of bony elements. The minimum facet resection avoids additional postoperative spinal instability2. Specifically, the use of the navigated burr helps real-time dynamic feedback during the resection of the bony spur. Another advantage is that this novel technique is performed only under navigation guidance, so there is no need to use a C-arm during surgery. We use a small field of view (FOV) and low-resolution mode, so one CT scan time is less than 30 s. The radiation per second of an O-arm 3D scan is four times that of fluoroscopy, so one O-arm scan is equivalent to approximately 1.5 min of fluoroscopy according to the radiation measurement12.
There are several critical steps in our new technique. Firstly, the first navigated dilater should not be inserted too deep because it has a relatively small diameter and so might injure the L5 nerve root. Secondly, if the patient has severe symptoms, the L5-S1 foraminal area must be very narrow. So, adequate bony resection is necessary before removing the herniated disc materials. Finally, the most important step within the protocol is that a navigated pointer should be used frequently to check the location to not remove too much bony resection. If there is a concern that the navigational accuracy is compromised during surgery, another O-arm scan should be taken.
Some modifications of this technique are available. A fully endoscopic decompression can be also performed if a long navigated pointer and a navigated high-speed burr are made. For cervical disc herniation, keyhole foraminotomy with a tubular retractor and navigation is very useful technique. With this technique, the authors performed C-arm free navigated percutaneous vertebral biopsy13.
There are several limitations of the procedure. Herniation/stenosis of the medial one-third of the lumbar disc are relative contraindications for this technique because the scope cannot reach the targeted area. Another limitation is the additional stab incision for the application of the navigation reference frame. The accuracy of navigation may be compromised due to movement of the reference frame; a new scan may be needed insuch a situation.
The authors have nothing to disclose.
This study was supported by the Okayama Spine Group.
1488 HD 3-Chip camera system | Stryker | 1000902487 | |
16mm Endoscope Attachment, Sterile | Medtronic | 9560160 | |
18mm Endoscope Attachment, Sterile | Medtronic | 9560180 | |
4K 32" surgical display | Stryker | 0240-031-050 | |
Adjustable hinged operating carbon table | Mizuho OSI | 6988A-PV-ACP | OSI Axis Jackson table |
L10 AIM light source | Stryker | 1000902487 | |
METRx MED System Endoscope, Long | Medtronic | 9560102 | |
METRx MED System Reusable Endoscope | Medtronic | 9560101 | Metrx |
METRx MED System Reusable Endoscope | Medtronic | 9560101 M | |
METRx MED System Reusable Endoscope, Long | Medtronic | 9560102 | |
Navigated high speed bur | Medtronic | EM200N | Stelth |
Navigated passive pointer | Medtronic | 960-559 | |
NIM Eclipse system | Medtronic | ECLC | Neuromonitouring |
O-arm | Medtronic | 224ABBZX00042000 | Intraoperative CT |
Stealth station navigation system Spine 7R | Medtronic | 9733990 | Navigation |
Surgical Carts | Stryker | F-NSK-006-00 | |
Tubular Retractor, 16mm | Medtronic | 955-524 | |
Tubular Retractor, 16mm, Long | Medtronic | 9560216 | |
Tubular Retractor, 18mm | Medtronic | 9560118 | |
Tubular Retractor, 18mm, Long | Medtronic | 9560218 |