E94 Spine • Volume 32 • Number 2 • 2007 Figure 1. The difference between the earlier transforaminal technique and our extraforaminal technique in terms of skin entry point and the angle of needle insertion. use percutaneous techniques for the treatment of spinal disorders. 8–10 Yeung and Tsou have reported favorable outcomes by applying transforaminal endoscopic discectomy to a mixed group of 307 patients, out of whom 30 were extraforaminal/foraminal disc herniations. 9 Similarly, Lew et al also reported their technique and results for foraminal/extraforaminal disc herniations with transforaminal endoscopic technique. 10 Both these techniques essentially used an inside-out technique, meaning thereby that the needle and working cannula are initially positioned inside the disc, intradiscal decompression is performed first, and subsequently the herniated foraminal/extraforaminal fragment is removed. The authors present a different technique, i.e., the “targeted fragmentectomy” technique for endoscopic removal of these extraforaminal disc herniations and also evaluate the results in a series of 41 patients. The target point for needle insertion is identified first from preoperative images, and the needle track and starting point are decided according to location of the hernia mass. The skin entry point is relatively medial and the approach angle is also relatively steeper in our technique as compared with the earlier described techniques (Figure 1). This gives a wider safety margin and makes the procedure less painful and better tolerated by the patients. We call it “extraforaminal targeted fragmentectomy” technique because the main focus in our technique is on the removal of the herniated disc fragment lying in the extraforaminal territory first, with little, if any, removal of the intradiscal contents. In some of the cases, we do advocate removal of the intradiscal fragments lying inside the posterolateral anulus, but such cases are few and the indications are explained later in the text. Materials and Methods Between May 2001 and June 2004, 778 patients were operated by a single surgeon (G.C.) for the diagnosis of a lumbar disc herniation. Of them, 478 were operated by lumbar microdiscectomy and 300 were operated by percutaneous endoscopic lumbar discectomy technique using a working channel endoscope (YESS System, Richard Wolff, Knittlingen, Germany). Among the percutaneous group, 41 patients were with an extraforaminal disc herniation. A retrospective analysis of these 41 patients along with a detailed description of our surgical technique is the focus of the present study. Patient selection criteria were as follows: 1) predominant unilateral radiating leg pain with or without associated back pain, 2) positive nerve root tension sign (sciatic or femoral nerve), 3) corresponding imaging findings on CT and MRI showing a single level soft extraforaminal disc herniation, and 4) failure of conservative treatment for 6 weeks. Patients who were operated before 6 weeks had severe radicular pain and did not show any signs of improvement during the first 2 weeks. The exclusion criteria were as follows: 1) presence of intraspinal pathology correlating with clinical symptoms, 2) associated evidence of bony foraminal or central stenosis with facet hypertrophy, 3) presence of instability, and 4) calcified disc. In the preoperative assessment, the patients were evaluated for their pain on a Visual Analog Scale (VAS) and functional assessment by a patient-based questionnaire (Oswestry Disability Index [ODI]). Clinical examination was performed for any nerve root tension sign and neurologic deficit. Routine lumbar radiographs along with CT scan and MRI scan were taken to outline the exact nature and level of the pathology (Figures 2, 3A). CT and MRI images were also used to calculate the exact point of skin entry for the needle insertion. VAS Figure 2. Preoperative MR sagittal view of the far lateral region with an up-migrated sequestrated herniated fragment (arrow) arising from L5–S1 disc, compressing the nerve root.
Percutaneous Endoscopic Discectomy • Choi et al E95 Figure 3. A, The preoperative MR axial scan along with topogram of the same patient showing L5–S1 extraforaminal disc herniation (arrow shows the sequestrated herniated fragment). B, Postoperative MR axial scan with topogram showing removal of the herniated fragment. evaluation for radicular pain and neurologic examination were repeated in the immediate postoperative period. Follow-up evaluation was done at 3 and 6 weeks and subsequently, if required. Postoperative MRI was done in all patients to evaluate and document the degree of decompression (Figure 3B). VAS and ODI were evaluated again at the time of final follow-up. The differences in preoperative and final follow-up VAS and ODI were checked statistically by paired Student t test, and a value of 0.05 was considered significant. The results were divided into satisfactory and unsatisfactory outcomes on the basis of percentage change in the value of the final ODI as compared with the preoperative value. An improvement of 50% or more was considered satisfactory and less than 50% was considered unsatisfactory. Question of lifting of heavy weight had to be modified according to the patient status before the onset of the current symptoms. Question of sexual activity was excluded. If any patient needed further surgery at the index level at any point of time during the follow-up period, it was automatically included in the poor group. Postoperative Protocol. The patients were discharged on either the same day or within 3 postoperative days, with a prescription for oral antibiotics for 3 days. Surgical Technique. The patient is put in a prone position on a radiolucent operating table with the affected side facing the surgeon and draped aseptically. The surgery is done under local anesthesia supplemented with neurolept analgesia [IV Fentanyl, (Hana Pharma, Seoul, Korea) 50 g initially and repeated if required]. Under image intensifier, the disc space to be approached is marked by drawing the 2 endplates, which should be seen parallel to each other. For the L5–S1 and L4–L5 levels, slight degree of cephalic-caudal tilt of the C-arm is usually needed (Fergusson view). The midline as well as the extent of iliac crest is marked with a marking pen, again under image intensifier. The skin entry point has already been calculated from preoperative assessment of axial CT scan. This can vary from 5 to 8 cm depending on the target pathology. The usual initial target point of the needle tip is the midpedicular line close to the superior endplate of the caudal vertebra, thus keeping the needle tip in the middle of Kambin’s safe triangle; 1% lidocaine is injected at the skin and along the desired tract. An 18-G spinal needle is inserted at the skin entry point and navigated toward the disc space under fluoroscopic control. In our technique, the needle angle from the midsagittal plane varies from 10° to 50°, depending on the level and location of the herniated disc (Figure 1). In case of L5–S1 EFDH, the skin entry point lies just medial to the iliac crest in line with the disc space. Therefore, at this level, the needle angle is usually lower (10°–30°) than other levels. In the anteroposterior view, when the needle tip is at the midpedicular line, it should be seen at the posterior vertebral bodyline in the lateral view. This confirms that the needle tip is lying at the posterior margin of the disc space. It is useful to inject some more lidocaine at this point to make the procedure more comfortable for the patient. The spinal needle is now advanced further to the center of disc space. The stylet is withdrawn and a discogram is performed by injecting 2 to 3 mL of a mixture of radio opaque dye (Telebrix, Guerbert, France), indigo carmine (Indigo Carmine, Carmine, Korean United Pharma, Seoul, South Korea), and normal saline mixed in 2:1:2 ratios. The injected mixture usually leaks and tends to follow the track of the sequestrated herniation through the tear in the anulus. Indigo carmine, being a base, selectively stains the degenerated acidic nucleus pulposus and helps for easier identification of the herniated disc during endoscopic visualization. Next, a 0.8-mm blunt-tipped guide wire is passed through the needle and the needle is withdrawn. The subcutaneous tract is developed by passing serial dilators of increasing size from 1 to 5 mm in a gentle twisting motion. This helps in pushing the exiting nerve root away from the working path. After withdrawal of the dilators, a blunt-tapered obturator is passed over the guide wire by gentle twisting motions under image intensifier control. The conical tip of the blunt obturator further helps in avoiding the entrapment of the exiting nerve root in the working path. The obturator tip is anchored over the surface of the disc space. Now, a closed round tip-working cannula (6 mm diameter) is passed over the obturator with its tip resting on the outer surface of the disc space, implying, thereby, that the cannula tip is anchored over the anulus. As the exiting nerve root is usually pushed cranially and laterally by the herniated disc, it is usually safe to carry out the above said manipulations without causing much pain. The 20° working channel endoscope (5.8 mm YESS scope, Working channel 2.7 mm) is then introduced through the working cannula. The first vision is usually of some adipose tissue covering the anulus, but sometimes the blue-stained herniated disc can also be directly seen on introduction of the endoscope. The adipose tissue is cleared using a flexible bipolar radio frequency probe (Triggerflex probe, Ellman Corp., New York) under endoscopic visualization. Any small bleeding points are also coagulated with bipolar probe, as good hemostasis is one of the keys to perform this procedure. By slight gentle twisting motions of the working cannula, the herniated fragment is brought into view and is released from its surrounding adhesions by a side-firing laser probe using Ho:YAG laser (Lumenis Inc., New York). The fragment can also be delivered into the field of vision with the help of a blunt probe. It is not imperative to visualize the whole of the herniated fragment before removal as it is jammed under or over the nerve root and attempts to see the whole fragment may produce unwanted procedural pain. Grasping the tail of the fragment with the endoscopic grasping forceps and gentle pulling is usually sufficient to remove the herniated fragment. At this stage, one can see the peridural membrane lying between the nerve root and the posterior surface of vertebral body (Figure 4). 11 Sometimes the large fragments are difficult to remove through the endoscopic working channel. Under such circumstance, one can grasp the large fragment and remove the endoscope along with the forceps, leaving the working cannula in position. The herniated disc in EFDH is usually fragmented;