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Minimally Invasive Thoracic Microendoscopic Diskectomy: A Tool for All Surgeons?
Perspectives Commentary on: Minimally Invasive Thoracic Microendoscopic Diskectomy: Surgical Technique and Case Series by Smith et al. pp. 421 427.
Edward C. Benzel, M.D. Professor of Surgery, Cleveland Clinic Chairman, Department of Neurosurgery Co Director, Spine Surgery Fellowship Program, Cleveland Clinic
Minimally Invasive Thoracic Microendoscopic Diskectomy: A Tool for All Surgeons? Edward C. Benzel1 and Tiffany Grace Perry2
PROBLEM AND PRESENTATION
O
ne of the most common pathologic conditions encountered by spine surgeons is a herniated nucleus pulposus. The incidence of symptomatic thoracic disk herniations is <1%. The relative mobility and range of motion about the ventrally located instantaneous axis of rotation partially accounts for the frequency of herniations in the lumbar and cervical spine. The thoracic spine is comparatively immobile with the sternum and rib cage providing substantial structural support, with a commensurate restriction of motion. Paraspinal muscles also contribute to diminished mobility, whereas the natural kyphosis of the thoracic spine limits the incidence of dorsal disk and annulus bulging. The structures that provide such immobilization making herniated nucleus pulposus less common in the thoracic region also serve as a barrier, of sorts, to the surgeon for surgical intervention. The transthoracic, transthoracic extrapleural, costotransversectomy, and dorsal approaches all are associated with significant drawbacks from an exposure and technical perspective. None of these approaches can be universally employed, and each is associated with approach-specific obstacles. The location, laterality, and characteristics of a disk herniation play a key role in the surgical decision-making process. A central calcified disk is better addressed through a ventral or far lateral approach, whereas a soft lateral disk herniation may be better managed via a dorsolateral approach. Patient presentation may vary, depending on the location and magnitude of the herniation. For far lateral disk herniations, radicular pain may be the
Key words - Microendoscopic - Minimally invasive - Myelopathy - Radiculopathy - Spine surgery - Thoracic disk herniation - Thoracic diskectomy
Abbreviation and Acronym TMED: Thoracic microendoscopic diskectomy
presenting complaint. An acute central disk herniation may cause rapid onset of myelopathy. Upper thoracic to midthoracic disk herniations may cause a deep chest pain that can be mistaken for cardiac pain. Midthoracic to lower thoracic disk herniations may masquerade as renal colic or gastrointestinal pain. The ultimate key to the decision-making process is careful physical examination in conjunction with obtaining appropriate imaging studies.
TREATMENT AND TRADITION The complexity of surgical treatment of thoracic disk herniations was well described by Eichholz et al. (1): “The discrepancy between the small percentage of patients seen with this disease and the large number of surgical techniques developed is a testament to the difficulty the spine surgeon may encounter when attempting to treat these patients.” Treatment options vary, depending on the severity of symptoms. A patient who presents with isolated radicular or back pain may be successfully treated nonoperatively. Patients with persistent debilitating pain or signs of myelopathy are often managed best with surgery. Surgical evaluation consists of appropriate imaging with magnetic resonance imaging or computed tomography with or without myelography. The surgical treatment of thoracic disk herniations is associated with the risk of permanent neurologic injury, either from direct injury to the spinal cord or by ischemic insult. For the approach to the disk space, thoracic nerve roots may be sacrificed, usually with minor consequences. Ventral and true lateral approaches facilitate access to the disk without risk of retraction of the spinal
From the 1Department of Neurosurgery, and 2Center for Spine Health, Neurological Institute, Cleveland Clinic, Cleveland, Ohio, USA To whom correspondence should be addressed: Edward C. Benzel, M.D. [E mail: [email protected]] Citation: World Neurosurg. (2013) 80, 3/4:319 321. http://dx.doi.org/10.1016/j.wneu.2013.01.059
WORLD NEUROSURGERY 80 [3/4]: 319 321, SEPTEMBER/OCTOBER 2013
www.WORLDNEUROSURGERY.org
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PERSPECTIVES
cord, but they involve risk to the thoracic organs and great vessels. Dorsal approaches involve more muscle dissection and bone removal, including the rib heads and facets of the thoracic spine, potentially inducing instability, more pain, and greater blood loss. Dorsolateral approaches to the thoracic spine may be associated with significant morbidity. These invasive approaches may also be associated with a 50% incidence of a postthoracotomy pain syndrome. Eichholz et al. (1) initially described a thoracic microendoscopic diskectomy (TMED) in 2006. This approach was developed to facilitate the surgical treatment of thoracic herniated nucleus pulposus without the morbidity of the traditional open approaches. The goals were to decrease blood loss, postoperative pain, hospital stay, and surgical recovery time. This technique is essentially a modification of the minimally invasive microendoscopic approach to the lumbar spine.
INVASIVENESS AND INNOVATION In the past 20 years, other authors have proposed similar techniques to treat thoracic disk herniations in an attempt to minimize the morbidity of ventral or lateral approaches. Jho et al. (2) used a 70-degree endoscope for the transpedicular endoscopic approach to thoracic disk herniations (3). Their trajectory began more medially and involved drilling through the lamina, medial facet, and a portion of the pedicle. They used a more angled scope to achieve an adequate view of the spinal canal. However, this steep angle can create a distorted view for the surgeon. The scope used by Smith et al. employs a 30-degree endoscope that is inserted through a more dorsolateral approach, with a musclesplitting technique to minimize postoperative pain. Uribe et al. (4) described using the extreme lateral minimally invasive approach, initially designed for lumbar interbody fusions, for thoracic disk herniations. Of their 60 cases, 7 (11.7%) acquired durotomies that, in most cases, were secondary to the adherence of calcified disk herniations to the dura mater. One benefit to this approach is that visualization of the disk space is achieved without the use of an endoscope; however, it also requires an accompanying interbody fusion. In contrast to the study by Smith et al., Uribe et al. (4) did not allow the presence of a calcified disk to exclude patients from their study. Their study was also larger, with 60 patients compared with 16 patients in the TMED study. This discrepancy in the study size is likely due to the specific exclusion criteria used by the TMED study.
TMED TECHNIQUE Smith et al. describe their experience with the TMED approach in 16 patients from 2003e2007 with thoracic disk herniations from T3-T12. Patients without myelopathy were considered for surgical intervention if they had an inadequate response to conservative therapy. Patients with progressive myelopathy were considered to be surgical candidates without conservative therapy. The authors excluded patients with calcified disk herniations but included patients with lateral and medial soft disk herniations. Patient presentations included segmental pain, radiculopathy, and myelopathy. They tracked operative time, blood loss, length of stay, and patient outcome over 24 months.
320
www.SCIENCEDIRECT.com
Two patients had poor outcomes because of other contributing disease processes (one with multiple sclerosis and one with multiple systems atrophy). As stated by the authors, the outcomes of these 2 patients likely would not have differed with another surgical approach. Of the 16 patients, 13 had excellent or good outcomes with near resolution of symptoms at 24-month follow-up. Only 1 patient had a fair outcome owing to improved but persistent segmental pain. At the time of 24-month followup, no patients had a symptomatic recurrent disk herniation or any segmental instability owing to the procedure. Smith et al. note that they did not encounter any complications during their surgical procedures, but they also acknowledge their small study population as well as the extensive minimally invasive experience by the experienced senior author. The TMED procedure seems to be an excellent approach that provides access to the thoracic spine for diskectomy, while minimizing blood loss, hospital stay, and postoperative pain. However, the operative time may increase, considering the use of new equipment for minimal access and endoscopy. In addition, surgeon learning curve with the use of endoscopic instruments in the spine plays a role regarding the safety and efficacy of the TMED procedure. Most spine-trained surgeons are familiar with minimally invasive techniques but may not be familiar with the use of the endoscope for spine applications. Since the initial description of the TMED procedure in 2006, three-dimensional endoscopy has matured; this new development may aid surgeons who may be more comfortable with three-dimensional visualization.
FOOD FOR THOUGHT The TMED procedure is best used for lateral soft disk herniations but also may be used for more medial herniations if a Woodson instrument or small down-angled curette is adjunctively employed. As with all operations, the three most important decision-making elements are (i) preoperative history and examination, (ii) acquisition of appropriate imaging studies, and (iii) appropriate patient selection. The TMED procedure seems to be a well-tolerated and safe approach for lateral noncalcified soft disk herniations. Given the relatively low incidence of symptomatic thoracic disk herniations and the even lower incidence of lateral noncalcified thoracic disk herniations, any single spine surgeon’s experience with this technique will likely be very small and suboptimal. The learning curve for the use of the endoscope in conjunction with the minimal access technique is crucial regarding the reduction of operative time and minimizing risk. With the dorsolateral muscle-splitting open technique, the incision is only slightly longer than the incision of the TMED approach. In addition, blood loss is usually minimal, and bone resection is insignificant. From the risk-to-benefit ratio perspective, is the innovative TMED procedure all that different from the traditional open approach? Do the extended learning curve and the duration of surgery warrant an expanded use of TMED? Ultimately, a comparison of the cumulative TMED and open surgical experiences of thoughtful and unbiased surgeons will answer the question: “Is TMED a tool for all spine surgeons?” Only time will tell.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.01.059
PERSPECTIVES
REFERENCES 1. Eichholz KM, O’Toole JE, Fessler RG: Thoracic microendoscopic discectomy. Neurosurg Clin N Am 17:441-446, 2006. 2. Jho HD: Endoscopic transpedicular thoracic discectomy. J Neurosurg 91(2 Suppl):151-156, 1999. 3. Regev GJ, Salame K, Behrbalk E, Keynan O, Lidar Z: Minimally invasive transformational,
thoracic microscopic discectomy: technical report and preliminary results and complications. Spine J 12:570-576, 2012.
Citation: World Neurosurg. (2013) 80, 3/4:319 321. http://dx.doi.org/10.1016/j.wneu.2013.01.059 Journal homepage: www.WORLDNEUROSURGERY.org
4. Uribe JS, Smith WD, Pimenta L, Hartl R, Dakwar E, Modhia UM, Pollock GA, Nagineni V, Smith R, Christian G, Oliveira L, Marchi L, Deviren V: Minimally invasive lateral approach for symptomatic thoracic disc herniation: initial multicenter clinical experience. J Neurosurg Spine 16:264-297, 2012.
WORLD NEUROSURGERY 80 [3/4]: 319 321, SEPTEMBER/OCTOBER 2013
Available online: www.sciencedirect.com 1878 8750/$ see front matter ª 2013 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
321
Edward C. Benzel, M.D. Professor of Surgery, Cleveland Clinic Chairman, Department of Neurosurgery Co Director, Spine Surgery Fellowship Program, Cleveland Clinic
Minimally Invasive Thoracic Microendoscopic Diskectomy: A Tool for All Surgeons? Edward C. Benzel1 and Tiffany Grace Perry2
PROBLEM AND PRESENTATION
O
ne of the most common pathologic conditions encountered by spine surgeons is a herniated nucleus pulposus. The incidence of symptomatic thoracic disk herniations is <1%. The relative mobility and range of motion about the ventrally located instantaneous axis of rotation partially accounts for the frequency of herniations in the lumbar and cervical spine. The thoracic spine is comparatively immobile with the sternum and rib cage providing substantial structural support, with a commensurate restriction of motion. Paraspinal muscles also contribute to diminished mobility, whereas the natural kyphosis of the thoracic spine limits the incidence of dorsal disk and annulus bulging. The structures that provide such immobilization making herniated nucleus pulposus less common in the thoracic region also serve as a barrier, of sorts, to the surgeon for surgical intervention. The transthoracic, transthoracic extrapleural, costotransversectomy, and dorsal approaches all are associated with significant drawbacks from an exposure and technical perspective. None of these approaches can be universally employed, and each is associated with approach-specific obstacles. The location, laterality, and characteristics of a disk herniation play a key role in the surgical decision-making process. A central calcified disk is better addressed through a ventral or far lateral approach, whereas a soft lateral disk herniation may be better managed via a dorsolateral approach. Patient presentation may vary, depending on the location and magnitude of the herniation. For far lateral disk herniations, radicular pain may be the
Key words - Microendoscopic - Minimally invasive - Myelopathy - Radiculopathy - Spine surgery - Thoracic disk herniation - Thoracic diskectomy
Abbreviation and Acronym TMED: Thoracic microendoscopic diskectomy
presenting complaint. An acute central disk herniation may cause rapid onset of myelopathy. Upper thoracic to midthoracic disk herniations may cause a deep chest pain that can be mistaken for cardiac pain. Midthoracic to lower thoracic disk herniations may masquerade as renal colic or gastrointestinal pain. The ultimate key to the decision-making process is careful physical examination in conjunction with obtaining appropriate imaging studies.
TREATMENT AND TRADITION The complexity of surgical treatment of thoracic disk herniations was well described by Eichholz et al. (1): “The discrepancy between the small percentage of patients seen with this disease and the large number of surgical techniques developed is a testament to the difficulty the spine surgeon may encounter when attempting to treat these patients.” Treatment options vary, depending on the severity of symptoms. A patient who presents with isolated radicular or back pain may be successfully treated nonoperatively. Patients with persistent debilitating pain or signs of myelopathy are often managed best with surgery. Surgical evaluation consists of appropriate imaging with magnetic resonance imaging or computed tomography with or without myelography. The surgical treatment of thoracic disk herniations is associated with the risk of permanent neurologic injury, either from direct injury to the spinal cord or by ischemic insult. For the approach to the disk space, thoracic nerve roots may be sacrificed, usually with minor consequences. Ventral and true lateral approaches facilitate access to the disk without risk of retraction of the spinal
From the 1Department of Neurosurgery, and 2Center for Spine Health, Neurological Institute, Cleveland Clinic, Cleveland, Ohio, USA To whom correspondence should be addressed: Edward C. Benzel, M.D. [E mail: [email protected]] Citation: World Neurosurg. (2013) 80, 3/4:319 321. http://dx.doi.org/10.1016/j.wneu.2013.01.059
WORLD NEUROSURGERY 80 [3/4]: 319 321, SEPTEMBER/OCTOBER 2013
www.WORLDNEUROSURGERY.org
319
PERSPECTIVES
cord, but they involve risk to the thoracic organs and great vessels. Dorsal approaches involve more muscle dissection and bone removal, including the rib heads and facets of the thoracic spine, potentially inducing instability, more pain, and greater blood loss. Dorsolateral approaches to the thoracic spine may be associated with significant morbidity. These invasive approaches may also be associated with a 50% incidence of a postthoracotomy pain syndrome. Eichholz et al. (1) initially described a thoracic microendoscopic diskectomy (TMED) in 2006. This approach was developed to facilitate the surgical treatment of thoracic herniated nucleus pulposus without the morbidity of the traditional open approaches. The goals were to decrease blood loss, postoperative pain, hospital stay, and surgical recovery time. This technique is essentially a modification of the minimally invasive microendoscopic approach to the lumbar spine.
INVASIVENESS AND INNOVATION In the past 20 years, other authors have proposed similar techniques to treat thoracic disk herniations in an attempt to minimize the morbidity of ventral or lateral approaches. Jho et al. (2) used a 70-degree endoscope for the transpedicular endoscopic approach to thoracic disk herniations (3). Their trajectory began more medially and involved drilling through the lamina, medial facet, and a portion of the pedicle. They used a more angled scope to achieve an adequate view of the spinal canal. However, this steep angle can create a distorted view for the surgeon. The scope used by Smith et al. employs a 30-degree endoscope that is inserted through a more dorsolateral approach, with a musclesplitting technique to minimize postoperative pain. Uribe et al. (4) described using the extreme lateral minimally invasive approach, initially designed for lumbar interbody fusions, for thoracic disk herniations. Of their 60 cases, 7 (11.7%) acquired durotomies that, in most cases, were secondary to the adherence of calcified disk herniations to the dura mater. One benefit to this approach is that visualization of the disk space is achieved without the use of an endoscope; however, it also requires an accompanying interbody fusion. In contrast to the study by Smith et al., Uribe et al. (4) did not allow the presence of a calcified disk to exclude patients from their study. Their study was also larger, with 60 patients compared with 16 patients in the TMED study. This discrepancy in the study size is likely due to the specific exclusion criteria used by the TMED study.
TMED TECHNIQUE Smith et al. describe their experience with the TMED approach in 16 patients from 2003e2007 with thoracic disk herniations from T3-T12. Patients without myelopathy were considered for surgical intervention if they had an inadequate response to conservative therapy. Patients with progressive myelopathy were considered to be surgical candidates without conservative therapy. The authors excluded patients with calcified disk herniations but included patients with lateral and medial soft disk herniations. Patient presentations included segmental pain, radiculopathy, and myelopathy. They tracked operative time, blood loss, length of stay, and patient outcome over 24 months.
320
www.SCIENCEDIRECT.com
Two patients had poor outcomes because of other contributing disease processes (one with multiple sclerosis and one with multiple systems atrophy). As stated by the authors, the outcomes of these 2 patients likely would not have differed with another surgical approach. Of the 16 patients, 13 had excellent or good outcomes with near resolution of symptoms at 24-month follow-up. Only 1 patient had a fair outcome owing to improved but persistent segmental pain. At the time of 24-month followup, no patients had a symptomatic recurrent disk herniation or any segmental instability owing to the procedure. Smith et al. note that they did not encounter any complications during their surgical procedures, but they also acknowledge their small study population as well as the extensive minimally invasive experience by the experienced senior author. The TMED procedure seems to be an excellent approach that provides access to the thoracic spine for diskectomy, while minimizing blood loss, hospital stay, and postoperative pain. However, the operative time may increase, considering the use of new equipment for minimal access and endoscopy. In addition, surgeon learning curve with the use of endoscopic instruments in the spine plays a role regarding the safety and efficacy of the TMED procedure. Most spine-trained surgeons are familiar with minimally invasive techniques but may not be familiar with the use of the endoscope for spine applications. Since the initial description of the TMED procedure in 2006, three-dimensional endoscopy has matured; this new development may aid surgeons who may be more comfortable with three-dimensional visualization.
FOOD FOR THOUGHT The TMED procedure is best used for lateral soft disk herniations but also may be used for more medial herniations if a Woodson instrument or small down-angled curette is adjunctively employed. As with all operations, the three most important decision-making elements are (i) preoperative history and examination, (ii) acquisition of appropriate imaging studies, and (iii) appropriate patient selection. The TMED procedure seems to be a well-tolerated and safe approach for lateral noncalcified soft disk herniations. Given the relatively low incidence of symptomatic thoracic disk herniations and the even lower incidence of lateral noncalcified thoracic disk herniations, any single spine surgeon’s experience with this technique will likely be very small and suboptimal. The learning curve for the use of the endoscope in conjunction with the minimal access technique is crucial regarding the reduction of operative time and minimizing risk. With the dorsolateral muscle-splitting open technique, the incision is only slightly longer than the incision of the TMED approach. In addition, blood loss is usually minimal, and bone resection is insignificant. From the risk-to-benefit ratio perspective, is the innovative TMED procedure all that different from the traditional open approach? Do the extended learning curve and the duration of surgery warrant an expanded use of TMED? Ultimately, a comparison of the cumulative TMED and open surgical experiences of thoughtful and unbiased surgeons will answer the question: “Is TMED a tool for all spine surgeons?” Only time will tell.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.01.059
PERSPECTIVES
REFERENCES 1. Eichholz KM, O’Toole JE, Fessler RG: Thoracic microendoscopic discectomy. Neurosurg Clin N Am 17:441-446, 2006. 2. Jho HD: Endoscopic transpedicular thoracic discectomy. J Neurosurg 91(2 Suppl):151-156, 1999. 3. Regev GJ, Salame K, Behrbalk E, Keynan O, Lidar Z: Minimally invasive transformational,
thoracic microscopic discectomy: technical report and preliminary results and complications. Spine J 12:570-576, 2012.
Citation: World Neurosurg. (2013) 80, 3/4:319 321. http://dx.doi.org/10.1016/j.wneu.2013.01.059 Journal homepage: www.WORLDNEUROSURGERY.org
4. Uribe JS, Smith WD, Pimenta L, Hartl R, Dakwar E, Modhia UM, Pollock GA, Nagineni V, Smith R, Christian G, Oliveira L, Marchi L, Deviren V: Minimally invasive lateral approach for symptomatic thoracic disc herniation: initial multicenter clinical experience. J Neurosurg Spine 16:264-297, 2012.
WORLD NEUROSURGERY 80 [3/4]: 319 321, SEPTEMBER/OCTOBER 2013
Available online: www.sciencedirect.com 1878 8750/$ see front matter ª 2013 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
321