Compression of the lumbar nerve roots and subsequent leg

Transcription

1 INVITED REVIEW ARTICLE Lumbar Decompression Using a Tubular Retractor System Sapan D. Gandhi, BS,* Christopher K. Kepler, MD, MBA,w and D. Greg Anderson, MDw Summary: Spinal stenosis and intervertebral disc herniation are the most common causes of nerve root compression and radiculopathy in the lumbar region. The symptoms from these conditions will vary widely from absent to severe and may include debilitating back and leg pain. Studies have shown positive outcomes with surgical decompression when nonoperative treatments have been exhausted. In contrast to traditional open lumbar decompression, minimally invasive techniques have been shown to decrease certain perioperative complications and shorten patient recovery time. This study will review the use of lumbar decompressive surgery using a tubular retractor system. Key Words: minimally invasive spine surgery lumbar decompression tubular retractor spinal stenosis. (Tech Orthop 2011;26: ) Compression of the lumbar nerve roots and subsequent leg pain (radiculopathy or neurogenic claudication) is commonly caused by herniated disc disease and spinal stenosis. Lumbar microdiscectomy is the most common spinal surgery performed. 1 The typical clinical presentation for a patient with a symptomatic disc herniation involves complaints of pain radiating down the extremities in a dermatomal distribution. Changes in strength, sensation, and reflexes are commonly found in association with these conditions. In elderly patients, lumbar spinal stenosis is a common cause of back and leg pain and trouble with walking. 1 The pathology of spinal stenosis is due to compression of the lumbar nerve roots by a combination of degenerative changes involving facet joint hypertrophy, ligamentum flavum thickening, and disc bulging. 2 The symptoms of lumbar stenosis are generally worse with standing and walking, and improved with flexion of the spine or sitting. Nonsurgical therapies for both herniated disc disease and lumbar stenosis include nonsteroidal anti-inflammatory drugs, epidural steroids, and physical therapy. When nonsurgical methods fail to alleviate the symptoms, surgery may be considered. Surgical decompression can be quite successful in patients with persistent symptoms brought on by lumbar stenosis or herniated disc disease. 1,3,4 Recent developments in surgical technique have led to a widespread interest in minimally invasive surgical approaches. In contrast to traditional open techniques, minimally invasive surgical decompression has been shown to decrease certain perioperative complications and shorten patient recovery time. 2,5,6 This article will review the technique of performing lumbar decompression surgery using a tubular retractor system. Received for publication May 19, 2011; accepted July 8, From the *Drexel University College of Medicine; and wthomas Jefferson University and Rothman Institute, Philadelphia, PA. The authors declare that they have nothing to disclose. Address correspondence and reprint requests to D. Greg Anderson, MD, Thomas Jefferson University and Rothman Institute, 925 Chesnut Street, 5th Floor, Philadelphia, PA davidgreganderson@comcast.net. Copyright r 2011 by Lippincott Williams & Wilkins ISSN: /11/ TECHNIQUE Preoperative Review and Surgical Setup Before surgery, a careful review of the preoperative studies (plain radiographs, magnetic resonance imaging or computed tomography myelography) should be undertaken, so that the surgeon has an intimate understanding of the location and causes of the patient s symptoms. Although these procedures are most commonly done under general anesthesia, epidural or spinal anesthesia can be used depending on the preference of the patient, anesthesia team, and surgeon. Prophylactic antibiotics and lower extremity compression stockings are administered before initiating the procedure. After the induction of anesthesia, the patient is placed prone on a radiolucent spine Jackson table, allowing fluoroscopic imaging of the lumbar spine. Special care must be taken to ensure that the abdomen is not compressed by the surgical position. A standard sterile prep and drape of the lumbar region should be used. The authors prefer to place the clamp that stabilizes the tubular retractor system on the same side as the surgeon. The C-arm and microscope can be used from either side and so are usually introduced from whichever side is easier based on the layout of the room and location of the operating room door (Fig. 1). Incision and Placement of the Tubular Retractor Before the surgical incision, the palpable landmarks including the posterior superior iliac spines, intercrestal line, and spinous processes are marked as reference points. Next, a spinal needle is introduced along the proposed surgical track. The spinal needle should be introduced lateral to the midline, aimed toward the facet joint to avoid inadvertent penetration of the spinal canal and cerebrospinal fluid leakage. C-arm fluoroscopy is then used to confirm the level for the surgical incision (Fig. 2). An incision is then made lateral to the midline corresponding to the diameter of the tubular retractor (Fig. 3). Both the skin and fascia should be opened sharply to reach the underlying multifidus muscle compartment. In situations where only an ipsilateral decompression is required, the incision is positioned 1.5 to 2 cm lateral to the midline, whereas in the setting of a bilateral decompressive procedure, the incision is made 3 to 4 cm lateral to the midline to allow angulation of the tubular retractor to the contralateral side. Heavier patients also will require a more laterally placed incision. A Cobb elevator is then used to bluntly separate the multifidus muscle from the underlying lamina. This step prepares the docking site for the tubular retractor and will minimize the resection of soft tissue that is required to perform the procedure. The use of a Kirschner wire as the initial step, before dilation, should be avoided due to the risk of inadvertent dural puncture. Next, tubular dilation is carried out with sequential dilators (Fig. 4) followed by placement of a tubular retractor of appropriate length. The smallest dilator is used to Techniques in Orthopaedics$ Volume 26, Number 3, 2011

2 Techniques in Orthopaedics$ Volume 26, Number 3, 2011 Lumbar Decompression Using Tubular Retractor FIGURE 3. A parasagittal incision is made the blue dot marks the position of the midline. FIGURE 1. The clamp for the retractor is placed on the same side of the table as the primary surgeon stands (far side in this photograph), whereas the C-arm and microscope can be brought in on the most convenient side based on the room layout. palpate the underlying anatomy and dock along the caudal edge of the lamina. With regards to the diameter of the tubular retractor, the authors prefer to use a 14 to 16 mm diameter system for a microdiscectomy procedure and an 18 to 20 mm diameter tubular retractor for decompression of lumbar stenosis. The length of the tubular retractor should be adequate to reach from the skin edge to the lamina. With the tubular retractor in position, the surgeon should secure the tube by attaching it to a table-mounted holder. Confirmation of the position of the tubular retractor should then be obtained with the C-arm fluoroscopy unit (Fig. 5). Any necessary adjustments to the tube should be made to ensure optimal access to the operative pathology before commencing the spinal procedure. An operative microscope is used for visualization. After focusing the scope down the tube, any residual soft tissue should be cleaned away with cautery to ensure good visualization of the bony landmarks (Fig. 6). The surgeon should preserve the facet joint capsule during soft tissue clearance. During this maneuver, it is important to identify the salient landmarks including the inferior laminar edge, ligamentum flavum, and the medial portion of the facet complex. FIGURE 2. Fluoroscopic image demonstrates spinal needle location before incision to ensure appropriate incision placement. FIGURE 4. Serial dilation of the incision creates the working corridor. c 2011 Lippincott Williams & Wilkins 137

3 Gandhi et al Techniques in Orthopaedics$ Volume 26, Number 3, 2011 FIGURE 5. Fluoroscopy is used to verify the location of the tubular retractor. Ipsilateral Decompression Using a Tubular Retractor System Ipsilateral decompression is used when symptomatic compression is isolated to only 1 side of the spinal canal. The decompressive procedure at this point is analogous to that used with other forms of surgical exposure. The procedure is commenced by using a curved curette to create a surgical plane between the ligamentum flavum and underside of the lamina. Next, a Kerrison rongeur is used to resect portions of the lamina sufficient to expose the compressed neural tissue. The ligamentum flavum should be resected or released adequately to expose the site of neural compression. Palpation of the pedicle within the spinal canal is useful to confirm the position of the pathology. In the case of a disc herniation, the dural edge is identified and mobilized after which a nerve root retractor is placed to provide gentle retraction. The posterolateral region of the disc is visualized and any required annulotomy is performed. Free disc material is then removed from the location of the herniation (Fig. 7). A long ball-tipped probe is used to sweep the spinal canal after excision of the visualized fragments to ensure adequate decompression of the nerve roots and an absence of additional disc material in a nonvisualized location. Large annular incisions should be avoided during discectomy as they may predispose the patient to future recurrent disc herniation. In the setting of lateral recess stenosis, the medial portion of the superior articular process is removed. This may require the use of a drill/burr to thin or remove the overlying inferior articular process. Next, a Kerrison rongeur can be used to trim the medial portion of the superior articular process until it is vertically aligned with the medial border of the pedicle. The FIGURE 6. Soft tissue is cleared with cautery to ensure good visualization of the bony landmarks. ipsilateral foramen can be decompressed with the use of a curved tip foraminotomy Kerrison rongeur. Care should be taken to ensure that the inferior articular process and par intraarticularis are not thinned to the point that fracture would be likely. Once adequate decompression of the neural tissue has been achieved, the surgeon should ensure hemostasis and then withdraw the tubular retractor. A number of technical points are worth mentioning. To minimize the risk of excessive thinning of the pars intraarticularis or inferior articular, these structures should be palpated with a number 4 Penfield to ensure that the surgeon is FIGURE 7. A pituitary rongeur is used to remove herniated disc material c 2011 Lippincott Williams & Wilkins

4 Techniques in Orthopaedics$ Volume 26, Number 3, 2011 Lumbar Decompression Using Tubular Retractor aware of their position before bony resection. To minimize the risk of dural or nerve root injury, it is helpful to initially leave the ligamentum flavum intact during bony resection of the lamina or drilling to provide protection to the dura. In addition, it is beneficial to frequently palpate the plane between the dura and the overlying tissue to ensure adhesions are not tethering the dura during the use of the Kerrison rongeur. Bilateral Decompression Using a Unilateral Approach When both sides of the spinal canal require decompression, angulation of the tubular retractor and undercutting of the spinous process region can be used to access the contralateral side of the spinal canal. Using a more laterally based incision (as described above), the ipsilateral laminotomy is done first, leaving the ligamentum flavum intact. 6 Next, the tubular retractor is wanded to the contralateral side. The surgeon will see the junction of the base of the spinous process and ipsilateral lamina when the tube has been properly positioned. It is helpful to tilt the operating table away from the surgeon s side during this maneuver to lessen the angle of the microscope and improve visibility across the midline. A high-speed drill/burr is used to drill away the undersurface of the contralateral spinous process and lamina (Fig. 8). It is useful to observe the quality of the bone during this drilling maneuver. Initially, cancellous bone will be encountered at the base of the spinous process, followed by the more cortical bone of the contralateral lamina. Next, the surgeon will encounter more cancellous-type bone as the contralateral inferior articular process is reached. The region will have to be thinned sufficiently so that the medial portion of the facet can be resected with a Kerrison rongeur. Using a small straight curette, the ligamentum flavum is then released from the undersurface of the contralateral facet complex and the thickness of the bone can be assessed. Additional drilling is used as needed to ensure that this region is resectable with a Kerrision rongeur. At this point, the attachments of the ligamentum flavum around the decompression site are released and the ligamentum flavum is removed. Direct visualization of the dural structures is then available and complete decompression of the contralateral lateral recess and foramen is achieved. After completion of the contralateral depression, the tubular retractor is angulated toward the ipsilateral side, and decompression of this region is achieved as described above. Once the bilateral decompression is complete, a ball tipped probe should be used to confirm adequate decompression of the nerve roots. Hemostasis should then be ensured. The tubular retractor can then be removed and the incision closed. Wound Closure and Postoperative Care When possible (due to the depth of the subcutaneous fat), the thoracolumbar fascia is closed using interrupted sutures. The subcutaneous tissues and skin are then closed with absorbable suture. A skin sealant is used along the incision to allow showering in the early postoperative period. The subcutaneous tissues along the incision are infiltrated with a long acting local anesthetic (Fig. 9). A dressing is then applied. After initial recovery from anesthesia, the patient is mobilized. In most cases, discharge on the day of the surgery is achieved. Patients are encouraged to walk at least 30 minutes a day and avoid strenuous activity for approximately 4 weeks. Management of pain is generally achieved with a low-potency oral narcotic or over the counter medication such as ibuprofen or acetaminophen. Formal outpatient physical therapy may be used if the patient is in need of supervised conditioning. OUTCOMES AND COMPLICATIONS Several studies have reported the outcomes with surgical intervention using a tubular retractor system. 1,3,4 Minimally invasive approaches have been shown to provide at least the FIGURE 8. The burr is used to perform the decompression. Adding water to the working area keeps bone dust down and minimizes the radius of thermal injury due to the heat generated by the burr. FIGURE 9. Injection of the wounds with a long-acting local anesthesic minimizes postoperative incisional pain. c 2011 Lippincott Williams & Wilkins 139

5 Gandhi et al Techniques in Orthopaedics$ Volume 26, Number 3, 2011 same level of symptomatic relief as traditional open techniques, but carry the added benefit of less iatrogenic soft tissue damage Minimally invasive techniques have been shown to cause less blood loss, less surgery-related postoperative pain, and require a shorter hospital stay compared with traditional open surgery. 2,5,10 A learning curve should be anticipated with tubular access decompression surgery, as with all surgical procedures. All the inherent risks of lumbar decompressive surgery remain with tubular access surgery. Careful technique and experience will help to minimize the incidence of problems associated with this type of procedure. The incidence of iatrogenic dural tears varies, but was reported to be as high as 16% in 1 study. 2 Owing to the lack of significant wound dead space, the resolution of dural tears is generally simpler compared with traditional open lumbar decompression. Small, stable dural tears may be managed by placing a small pledgette of a hemostatic agent on the site, followed by the application of a dural sealant such as fibrin glue. Larger tears may benefit from suture closure, which can be challenging but achievable using the micropituitary instrument (as the needle driver) and an arthroscopic knot pusher. 13 Infection when using a tubular retractor system is rare. 9 In the event of a wound infection, traditional techniques of debridement and antibiotic therapy should be used. CONCLUSIONS Tubular retractor approaches to lumbar decompression have potential advantages compared with open lumbar decompression. The surgeon learning curve is manageable for most surgeons by cadaver training, apprenticeship, and graduated exposure to more difficult cases. With good technique, the surgeon can anticipate less blood loss, less pain, lower infection rate, and a shorter hospital stay compared with traditional decompressive procedures. 14,15 REFERENCES 1. Atlas SJ, Keller RB, Robson D, et al. Surgical and nonsurgical management of lumbar spinal stenosis: four-year outcomes from the Maine Lumbar Spine Study. Spine. 2000;25: Khoo LT, Fessler RG. Microendoscopic decompressive laminotomy for the treatment of lumbar stenosis. Neurosurgery. 2002;51(Suppl 2): Atlas SJ, Keller RB, Wu Y, et al. Long-term outcomes of surgical and nonsurgical management of lumbar spinal stenosis: 8 to 10 year results from the Maine Lumbar Spine Study. Spine. 2005;30: Turner JA, Ersek M, Herron L, et al. Surgery for lumbar spinal stenosis, attempted meta-analysis of the literature. Spine. 1992;17: Asgarzadie F, Khoo LT. Minimally invasive operative management for lumbar spinal stenosis: overview of early and long-term outcomes. Orthop Clin N Am. 2007;38: Palmer S, Turner R, Palmer R. Bilateral decompression of lumbar spinal stenosis involving a unilateral approach with microscope and tubular retractor system. J Neurosurg (Spine 2). 2002;97: Guiot BH, Khoo LT, Fessler RG. A minimally invasive technique for decompression of the lumbar spine. Spine. 2002;27: Benz RJ, Garfin SR. Current techniques of decompression of the lumbar spine. Clin Orthop Relat Res. 2001;384: Rosen DS, O Toole JE, Eichholz KM, et al. Minimally invasive lumbar spinal decompression in the elderly: outcomes of 50 patients aged 75 years and older. Neurosurgery. 2007;60: Podichetty VK, Spear J, Isaacs RE, et al. Complications associated with minimally invasive decompression for lumbar spinal stenosis. J Spinal Disord Tech. 2006;19: Riew KD, Rhee JM. Microsurgical techniques in lumbar spinal stenosis. Instr Course Lect. 2002;51: Park P, Foley KT. Minimally invasive transforaminal lumbar interbody fusion with reduction of spondylolisthesis: technique and outcomes after a minimum of 2 years follow-up. Neurosurg Focus. 2008;25:E Chou D, Wang VY, Khan AS. Primary dural repair during minimally invasive microdiscectomy using standard operating room instruments. Neurosurgery. 2009;64(5 Suppl 2): Ikuta K, Arima J, Tanaka T, et al. Short-term results of microendoscopic posterior decompression for lumbar spinal stenosis. Technical note. J Neurosurg Spine. 2005;2: Yagi M, Okada E, Ninomiya K, et al. Postoperative outcome after modified unilateral-approach microendoscopic midline decompression for degenerative spinal stenosis. J Neurosurg Spine. 2009;10: c 2011 Lippincott Williams & Wilkins