Imaging for percutaneous lumbar disc decompression procedures

Techniques in Regional Anesthesia and Pain Management (2007) 11, 81-89

Imaging for percutaneous lumbar disc decompression procedures Timothy Deer, MD,a Leonardo Kapural, MD, PhDb From the aCenter for Pain Relief, Charleston, West Virginia; and the b Cleveland Clinic, Cleveland, Ohio. KEYWORDS: Percutaneous decompression; Nucleoplasty; Dekompressor; Decompressive catheter; Herniated disc; Imaging; Fluoroscopy

This article analyzes the proper use of imaging in the performance of procedures for disc decompression by minimally invasive techniques. The importance of obtaining and reviewing images before the procedure is discussed. Reviewed are the positioning, preparation, performance, and follow up of patients undergoing these procedures. The proper views on fluoroscopic imaging are highlighted, and examples are given of desirable images for performing these cutting edge techniques. Clinical pearls and pitfalls for those procedures are reviewed, and examples of proper imaging are shown. © 2007 Elsevier Inc. All rights reserved.

Disc disease is a common cause of pain and disability. The indications for surgical disc decompression, removal, or replacement are controversial and continuously debated.1 In some cases, surgical treatment is the obvious treatment of choice. This is true for disc herniation causing mechanical nerve root compression, disc extrusion, and fracture of a disc fragment into the foramen. In some cases, the argument for surgical correction is not as strongly supported.2 These indications include contained disc herniation, concordant pain during provocative discography, and pain with annular leak in the setting of maintained disc pressure. In this article, we will review the placement of a needle into the disc space to decrease the disc pressure and volume to treat these less severe conditions. There are various ways of achieving the disc decompression which have clearance by the Food and Drug Administration (FDA). Mechanisms of decompression include mechanical removal of disc material, therAddress reprint requests and correspondence: Timothy Deer, MD, Center for Pain Relief and Professor, Department of Anesthesiology, West Virginia University, 400 Court Street, Suite 304, Charleston, WV 25301. E-mail address: [email protected].

1084-208X/$ -see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1053/j.trap.2007.02.014

mal contraction of the disc material, or tissue breakdown by breaking up the nucleus pulposus.3 Specifically, three techniques used as minimally invasive treatments for contained protrusion of the nucleus pulposus are the Nucleoplasty TM (ArthroCare Corporation, Sunnyvale, CA), which uses radiofrequency vaporization of nuclear tissue, catheter disc decompression (Acutherm, Smith and Nephews, London, England), which uses heat from the resistive coil positioned within disc herniation, and Dekompressor® (Stryker Inc., Kalamazoo, MI), which uses volume reduction to decrease the intradiscal pressure.4-7

Preoperative imaging Before performing the planned decompressive procedure, it is important to familiarize yourself with the patient’s baseline anatomy. This may be accomplished by reviewing the previous plain films, MRI, CT scans, or provocative discograms. The plain films are helpful in evaluating the disc space height, any bone spurring, presence of scoliosis, or spinal

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diseases. MRI is helpful to determine the disc height, intrinsic disc structure, disease processes, and to allow for a strategy for disc entry. The addition of gadolinium to the imaging process is helpful in patients with a history of lumbar surgery. In these cases, the gadolinium helps to delineate between scar tissue versus recurrent disc disease. CT scans offer some of the advantages of MRI, although the view of the disc is not as ideal. CT does offer the advantage of seeing the tissues surrounding the spine with greater clarity. This is important if any processes are ongoing adjacent to the spine, such as tumor, abscess, or aortic disease. Provocative discography is helpful in identifying the pain generator. The anatomy of the annulus and nucleus can also be evaluated. This is important since the choice of percutaneous procedure may be different based on the integrity of the annulus and the appearance and pressure within the nucleus pulposus.

if any exist. All coexisting diseases should be stabilized. Careful attention should be given to diseases associated with bleeding disorders and immunosuppression. Preoperative clearance by the primary care physician is recommended for patients with any questionable problems, such as poorly controlled diabetes or the need for medications that effect platelets or clotting. Anesthesia consultation is also recommended before surgery.

Anesthesiology Once the patient is felt to be stable for surgery, the anesthesia care team is consulted to evaluate the American Society of Anesthesiology status and any preoperative precautions needed before beginning. Options for relieving pain during the procedure include:

Preoperative evaluation

Local anesthesia

The patient should be informed of possible complications and risks. The patient should be given time to ask any pertinent questions and express concerns. Other surgical options should be addressed as well as conservative options

The procedure can be performed under local anesthesia with no sedation to avoid affecting the patient’s mental status. The advantage of this technique is the patient is alert and can easily notify the surgeon of any pain related to

Figure 1 Proper initial anterior–posterior view of disc space when coducting any of three minimally invasive disc decompressive procedures. The lower L4-5 end-plate is horizontally lined with posterior part of the same end-plate. Spinous processes are positioned midline.

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nerve irritation. The disadvantage of performing this procedure under local is the patient may experience significant discomfort, and this may result in an uncooperative patient who does not maintain proper positioning.

Monitored anesthesia care with local anesthetic supplementation The procedure can be performed under monitored anesthesia care with the patient remaining responsive. For many patients, this is the ideal method of anesthesia. The patient is made comfortable which assists in maintaining positioning. Local anesthetic is used for the skin wheel and superficial tissues. It is important to have a continuing conversation with the patient when sedation is used to assure they remain responsive at all times. The sedation should be discontinued at any point in which there is an issue of nerve irritation.

83 complications. It is the opinion of the authors that these procedures should not be done under general anesthesia.

Preoperative and intraoperative antibiotics There are no definitive studies that show an advantage to using preoperative antibiotics in these patients.8-10 Despite this lack of evidence-based studies, most physicians use intravenous antibiotics before going to the procedure area. Recommended drugs vary based on local pathogens in the institution in which the procedure is being performed.9 Commonly, the antibiotic selected is a third generation cephalosporin or vancomycin.9,10 Many clinicians also choose to place a small amount of intradiscal antibiotic at the time of the disc assessment. In most of these settings, the antibiotic is a cephalosporin which is diluted to a very low concentration with contrast.

General anesthesia The procedure can be performed under general anesthesia. This will reduce movement and discomfort. The disadvantages of this type of anesthesia far outweigh the advantages. The patient is put at high risk for permanent nerve damage and

Positioning Once the patient has been selected for a lumbar percutaneous disc decompression, they are positioned in the prone position.

Figure 2 In the oblique view, superior articulate process (SAP) of the L4-5 disc level (level of interest) is brought at the half width of the intervertebral disc. That provides an optimal angle for nuclear access of the probe.

Figure 3

Target image of SAP and disc space. Needle is positioned next to the SAP using tunnel-view approach from an oblique angle.

Figure 4 Lateral view of advancing DekompressorTM canula. Final position should be within the nuclear herniation and away from the end-plates and neural elements.

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Figure 5 Anterior–posterior view of advancing DekopressorTM canula. Same-sided contained herniation exists posteriorly. The tip of the canula appears to be within the disc which will be confirmed by injecting through the canula diluted contrast dye.

The greatest difficulty of positioning is the natural lumbar lordosis patients have at baseline. When positioning a patient for this procedure, there are several important points: 1. The abdomen and pelvis should be properly padded and positioned to eliminate lumbar lordosis. The goal is to create a neutral angle of the lumbar spine, or ideally to create a kyphosis to allow for easier access to the disc spaces. 2. The shoulders should be square with no rotation. Rotation at the upper body can create an abnormal film in the lumbar spine. 3. The patient should have no weight resting on the arms. The patient should be relaxed with the weight resting on the chest. By resting weight on the arms, the muscles of the lumbar spine are contracted, the procedure is made more difficult, and the level of pain from the procedure may be increased. 4. The patient’s head should be relaxed and placed comfortably on a cushion. Stress in the head and neck can also cause tightness in the lumbar spine. 5. The patient’s legs should be relaxed with the feet resting on a pillow and the knees slightly bent. The legs should remain uncrossed.

6. Patients who have a large abdominal pannus may be shifted to obscure the midline. In these patients, cushions should be used to level the patient and the table should be rotated. Obesity is a complicating factor for positioning, imaging, and all aspects of the procedure.

Imaging Before performing percutaneous disc decompression, the physician should have a thorough understanding of fluoroscopic imaging, radiation safety, and principles of multiplaner imaging (an excellent review in this issue by Dr. Davros). The quality of equipment varies dramatically from facility to facility and among office-based practices, hospitals, and ambulatory surgery centers. The physician must match the technique to the capabilities of the machine available for use (see Dr. Davros article).

Table It is important to have an appropriate table for the performance of these procedures. The table should tilt side to side, perform Trendelenburg and reverse Trendelenburg move-

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Figure 6 Lateral view of the contrast study. Injected diluted contrast allows visual control over the nucleoplasty wand. The tip of the wand is at the anterior edge of L4-5 intervertebral nucleus.

ments, and move up and down appropriately. All components of the table should be fluoroscopically compatible. Rods, bars, screws, and padding components should be radio-opaque. The table should allow easy access to the airway in the event of emergency and allow for free motion of the C-Arm in all desired views.

Principles of imaging Once the patient has undergone preoperative evaluation and stabilization, proper positioning, prepping, and draping, the procedure is initiated. Previous evaluation of the spine with preoperative imaging should have familiarized the surgeon with the patient before coming to the operating room. It is helpful to post any important films in the procedure area at the time of surgery for review during the technique. The procedure is initiated by performing scout films to maximize the chances of a good outcome.

Initial films The initial films are important to line up angles and assure proper level. Films should start at the T12 level, and the

vertebral bodies should be counted and marked down to the sacrum. A sterile marking pen can be helpful in keeping track of proper levels and disc spaces. Once the level of interest is confirmed, the end plates of the disc spaces should appear sharp and crisp as a uniform linear structure (Figure 1). This is accomplished by rotating the image under live guidance into angles of cephalad and caudad views until the proper view is seen. The angle of correction will vary based on the degree of lordosis or kyphosis present at the disc level of interest.

Target films Once the baseline films are satisfactory, the next step is to obtain a film for the probe target. This is based on maintaining the proper angle on the cephalad to caudad view and then moving the beam to an oblique view that shows the superior articular process dissecting the midline of the disc space (Figure 2). Once this film is properly aligned, the needle is targeted to the inferior portion of the lateral edge of the superior articular process (Figure 3).

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Figure 7 The nucleoplasty SpineWandTM as in Figure 6 now in the starting position at posterior edge of the nucleus. Usually, six channels are created within the nucleus.

Procedure films

Procedure confirmation

The depth of the needle or the progress toward the midline cannot be determined by the oblique view, so it is important to continuously move the image from the oblique to the anterior–posterior view to the lateral view as the needle is advanced. (Figures 4 and 5).

After the needle has been confirmed on proper views, the procedure is performed. Different methods of decompression exist. These include mechanical decompression by drilling, thermal decompression by coagulation, and tissue disruption by passing a probe in different tracks in the nucleus on repeated occasions.11 Despite the chosen technique, the goal is to take repeated images to maintain the tools within the nucleus pulposus (Figures 5– 8). When performing disc decompression, the goal is to avoid entering the annulus. This differs from intradiscal electrothermoplasty where the annulus is intentionally entered. Once the desired action of decompression is completed, the clinician may opt to repeat the imaging contrast study or the pressure measurement. This postprocedure imaging and pressurization measurement is at the discretion of the clinician.

Contrast confirmation Once the needle is in good position on all views, the next step is performed. Some clinicians prefer to place a small amount of contrast into the disc before doing the disc decompression. The placement of contrast is similar to a conventional discogram, although the volume of contrast is often reduced (Figures 6 and 7). The appearance of the disc should be reviewed, the pressure of the disc should be noted, and the reproduction of pain should be recorded if applicable The pressure can be checked after the disc decompression as a comparison to evaluate the effect of the removal of volume on the pressure measurement.

Specifics For the nucleoplasty (Figures 6 and 7; CoblationTM, ArthroCare Corporation, Sunnyvale, CA), an access to the disc is accomplished through a 17-gauge cannula with

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Figure 8 Acutherm resistive coil placed within the nucleus. Active, heating portion of the coil is positioned over the posterolateral contained disc herniation.

the obturator stylet. It is followed by a radiofrequency electrode called the SpineWand (Figures 6 and 7). The tip of the needle is placed at the junction of annulus and nucleus, so that nucleus will be only accessed by the active tip. Tissue removal creates channels through the nucleus to the opposite side of the disc, where a depth-stopper prevents ablation into the annulus12 (Figure 6). The cannula will be slowly withdrawn to the starting position (Figure 7) six times. The patient is then brought to the recovery room and shortly discharged home.13-15 For Dekompressor® discectomy, a battery-operated disposable hand piece is connected to a helical probe. A 17gauge cannula provides access to the disc space and as a channel for tissue removal (Figures 4 and 5). Once the desired cannula tip position is achieved in the disc, probe is inserted through the cannula and connected. Rotation of the exposed helical probe tip will result in the aspiration of nuclear tissue and mechanical evacuation back through the cannula. The amount of the nuclear material will depend on the size of contained herniation.15 The electrothermal Decompression Catheter (Acutherm; Smith and Nephew, London, UK; Figure 8) is composed similarly of a 17-gauge introducer needle and resistive coil. Introducer should be positioned in the posterior part of the disc opposite from the side where contained herniation is present.

Resistive coil will then be threaded through the disc nucleus until clearly positioned into concavity of the herniation (Figure 8). Thermal energy will then be used for the focal decompression of contained herniated disc over 16 minutes.16

Table 1 Clinical pearls to consider when performing techniques Evaluate and stabilize comorbid states prior to proceeding. Review and understand the anatomy prior to proceeding. Spend time and effort to assure proper positioning. Prep and drape carefully and widely. Evaluate the patient with a baseline image to line up proper angles. Evaluate the patient with a baseline image to assure proper level. Obtain a proper target image to identify needle placement. Image in all views as the probe is placed to assure location. Make sure the patient is responsive. Reposition the needle if the patient complains of a paresthesia. Assure proper end position of the needle on two or more views. If a discogram is performed, coordinate it with the procedure. Use digital manometry to measure pressure reduction with decompression. Monitor post procedure for complications or side effects.

Deer and Kapural Table 2

Imaging and Disc Decompression

Pitfalls to avoid when performing techniques

Do not perform this procedure in patients with unstable diabetes, clotting disorders, or immunosuppression. Do not perform this procedure in patients who are tilted, have uneven shoulder or leg position, or other positioning problems. Do not perform this procedure in patients who are under general anesthesia or are unresponsive. Do not fail to reposition the needle if a paresthesia is elicited. Do not perform the procedure with equipment that does not allow proper disc space visualization. Do not perform the procedure on the wrong level. Do not perform the procedure in the annulus. Do not decompress the disc so extensively that the volume leads to posterior element disease.

Pearls Table 1 shows which clinical pearls should be considered when performing these techniques.

Pitfalls Table 2 shows the pitfalls that should be avoided when performing these techniques.

Conclusion The minimally invasive nature of percutaneous disc decompression makes this technique attractive to patients who hope to avoid larger open spine surgery procedures. Proper imaging makes the procedure less difficult, improves safety, and increases the likelihood of a successful long-term outcome.

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