COLUMNS International Society for the Advancement of Spine Surgery
ENDOSCOPIC SPINE SURGERY: FUTURE OR FEASIBLE? Current State of Endoscopic Spine Surgery
Also: Rare Complications of Lateral Surgery Approach to Treatment of Metastatic Disease in the Spine The Evidence (or Lack Thereof) for Cannabidiol in the Treatment of Spinal Conditions A Review of the Use of Vancomycin Powder in Spine Surgery Augmented and Virtual Reality in Spine Surgery: Where We Are Now and Where We Might Be Headed
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Editor in Chief Kern Singh, MD
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EDITORIAL Endoscopic Spine Surgery: Future or Feasible?
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ENDOSCOPY Current State of Endoscopic Spine Surgery COMPLICATIONS Rare Complications of Lateral Surgery
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CANCER Approach to Treatment of Metastatic Disease in the Spine
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PHARMACEUTICALS The Evidence (or Lack Thereof) for Cannabidiol in the Treatment of Spinal Conditions
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BIOLOGICS Use of Vancomycin Powder in Spine Surgery
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TECHNOLOGY Augmented and Virtual Reality in Spine Surgery: Where We Are Now and Where We Might Be Headed
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Editorial Board Peter Derman, MD, MBA Brandon Hirsch, MD Sravisht Iyer, MD Safdar Khan, MD Yu-Po Lee, MD Sheeraz Qureshi, MD Grant Shifflett, MD Managing Editor Audrey Lusher Designer Randy Schirz
Vertebral Columns is published quarterly by the International Society for the Advancement of Spine Surgery. ©2020 ISASS. All rights reserved. Opinions of authors and editors do not necessarily reflect positions taken by the Society. This publication is available digitally at www.isass.org/news/vertebral-columnswinter-2020
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EDITORIAL
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Endoscopic Spine Surgery: Future or Feasible? The overall advances in minimally invasive techniques and other technological innovations have laid the framework for the current landscape of endoscopic spine surgery (ESS). With smaller approaches and incisions than previously possible, ESS is thought to offer a reduced infection risk, decreased tissue trauma, and shorter operating times. If these benefits are indeed demonstrated, there are numerous advantages that may benefit spine surgery. Minimizing trauma to surrounding tissue and maintaining the integrity of muscle and nervous tissue will reduce scarring and likely result in faster recovery times. The benefits of these outcome enhancements are likely to be reflected in better patient-reported outcomes and improved satisfaction. Reduced operative durations will have a positive impact on operating room schedules, time under general anesthesia, and surgical staffing timetables. A reduced postoperative surgical stay would potentially have extensive benefits realized in both hospital or surgical center efficiency and value. Although the proposed benefits of ESS are vast, research that establishes any of the advantages is still ongoing. As of yet, no investigations have rigorously demonstrated ESS cost superiority compared with current minimally invasive surgery (MIS) or open spine surger y techniques.1 Nonetheless, isass.org
global barriers to most surgical Kern Singh, MD interventions are often focused on perioperat ive morbidit y. 2 ESS could improve perioperative morbidity through reduced postoperative lengths of stay. The feasibility of ESS depends tremendously on the endoscopic procedure and healthcare infrastructure. For example, even in a region such as Asia, with many ESS pioneers, there are significant variations in infrastructure practicality.1 Hence, ESS will only become more practical to spine surgeons as research yields more affordable equipment and techniques along with concomitant changes in healthcare infrastructure. Although most spine surgeons are aware of endoscopic surgical options, the procedures are performed by a minority of surgeons. This may be, in part, due to its steep learning curve.3 Numerous studies have reported high complication rates and operative durations during the early learning period.4 The ESS learning curve has been observed to improve significantly after 10-14 surgeries, after which time steady improvement is observed. 5 Once surgeons integrate ESS into practice, most studies report lower complication rates than open or other MIS approaches. The most frequently reported complications within endoscopic lumbar surgery are durotomy, epiVertebral Columns
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“Once surgeons integrate ESS into practice, most studies report lower complication rates than open or other MIS approaches.”
dural hematoma, and infection.6 It should still be acknowledged that the only randomized control trial to date comparing ESS with earlier MIS techniques identified no statistically significant dif ference in complication rates.7 ESS techniques often utilize irrigation techniques and local anesthesia, both of which are thought to increase epidural pressure.8 Related to these mechanics, the literature mentions complications such as postoperative headache, prodromal neck pain followed by postoperative seizure,8 and with radicular pain and
paresthesia. Radiculopathy has been confirmed by identifying a correspondence with operational level.9 Likewise, the visuospatial distortion that can occur with endoscopy has also been controversially asserted to increase the chances of durotomy.9 At present, the dramatic increase in lumbar-focused research makes the lumbar spine a prime target for ESS application. In adopting these methods, there are numerous challenging technical hurdles that surgeons are confronted with—both within individual practice and systemically in health care. Despite these challenges, the potential for decreased perioperative morbidity is likely to accelerate the expansion, acceptance, and innovation of ESS, making it an essential adjunct or even replacement for many of our current methods. n
References 1. Shi R, Wang F, Hong X, et al. Comparison of percutaneous endoscopic lumbar discectomy versus microendoscopic discectomy for the treatment of lumbar disc herniation: a meta-analysis. Int Orthop. 2019;43(4):923-937. doi:10.1007/s00264-018-4253-8
4. Marappan K, Jothi R, Paul Raj S. Microendoscopic discectomy (MED) for lumbar disc herniation: comparison of learning curve of the surgery and outcome with other established case studies. J Spine Surg. 2018;4(3):630637. doi:10.21037/jss.2018.06.14
7. Chen Z, Zhang L, Dong J, et al. Percutaneous transforaminal endoscopic discectomy compared with microendoscopic discectomy for lumbar disc herniation: 1-year results of an ongoing randomized controlled trial. J Neurosurg Spine. 2018;28(3):300310. doi:10.3171/2017.7.SPINE161434
2. Pendharkar AV, Shahin MN, Ho AL, et al. Outpatient spine surgery: defining the outcomes, value, and barriers to implementation. Neurosurg Focus. 2018;44(5):E11. doi:10.3171/2018.2.FOCUS17790
5. Choi CM, Chung JT, Lee SJ, Choi DJ. How I do it? Biportal endoscopic spinal surgery (BESS) for treatment of lumbar spinal stenosis. Acta Neurochir. 2016;158(3):459463. doi:10.1007/s00701-015-2670-7
8. Choi G, Kang H-Y, Modi HN, et al. Risk of developing seizure after percutaneous endoscopic lumbar discectomy. J Spinal Disord Tech. 2011;24(2):83-92. doi:10.1097/BSD.0b013e3181ddf124
3. Hsu H-T, Chang S-J, Yang SS, Chai CL. Learning curve of full-endoscopic lumbar discectomy. Eur Spine J. 2013;22(4):727733. doi:10.1007/s00586-012-2540-4
6. Kim M, Lee S, Kim H-S, Park S, Shim S-Y, Lim D-J. A comparison of percutaneous endoscopic lumbar discectomy and open lumbar microdiscectomy for lumbar disc herniation in the Korean: a meta-analysis. Biomed Res Int. 2018;2018:9073460. doi:10.1155/2018/9073460
9. Sairyo K, Matsuura T, Higashino K, et al. Surgery related complications in percutaneous endoscopic lumbar discectomy under local anesthesia. J Med Invest. 2014;61(3-4):264269. doi:10.2152/jmi.61.264
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Current State of Endoscopic Spine Surgery After nearly 30 years of development, endoscopic spine surgery is said to be transiting its “slope of enlightenment,”1 according to the Gartner technology adoption hypothesis. 2 To provide a complete picture of the current landscape of endoscopic spine surgery, we will briefly trace the development of endoscopic spinal techniques. As with the introduction of any new technology, a steep learning curve had to be overcome, but now endoscopic spine surgery is positioned to deliver benefits in practical surgeries. Endoscopic spine procedures are generally regarded as having begun in 1983 with Kambin’s and Gellman’s technique to manage degenerative disc disease with a non-visualized percutaneous needle nucleotomy. 3 Using a posterolateral approach with a Craig biopsy cannula, they used a technique described in 1975 by Hijikata.4 Later in 1983, the introduction of the endoscope allowed Forst and Hausmann to achieve sufficient disc space visualization that facilitated decompression.5 These initial steps were followed by numerous advances in approach techniques and visualization technologies, many of which paved the way for current high-quality endoscopic visualization and treatment systems. Although numerous advances have been made in the techniques employed within the cervical and thoracic spine, current endoscopic surisass.org
gery has most frequently been Kern Singh, MD described in the lumbar region of t he spi ne. Contempora r y methods of endoscopic spine su rger y t reat va r ious spi na l pathologies, including primary or recurrent disc disease, spinal stenosis, instability, and spondylolisthesis. Future goals of Daniel Park, MD endoscopic spine surgeons are to provide long-term outcomes utilizing these minimally invasive techniques. T he i nt ra for mat iona l, or t ra nsfora m i na l, endoscopic technique is one of t he most commonly described current lumbar techniques that is utilized to access either the extradiscal or intradiscal space. Described in 1990, the Kambin triangle is a familiar area in the endoscopic community. It is the zone bordered by the exiting nerve root anteriorly, the transverse nerve root medially, and the caudal vertebral body.6 This defined working area allows for the safe introduction of various instruments and endoscopes into the spine. However, localization to the Kambin triangle can be difficult at L5-S1 due to the iliac crest.7 Several spinal pathologies are more centrally located than the foramen, which has led some surgeons to utilize the interlaminar Vertebral Columns
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space. This transition paved the way for the ability to address pathologies beyond discal problems. The challenges that needed to be surmounted for successful interlaminar work included utilizing more specialized equipment to address bleeding and bone shaving work. As with all emerging techniques, innovation was key. Surgical innovation allowed for the development of endoscopic biportal techniques to help overcome some of the shortcomings of uniportal approaches. 8–10 Biportal approaches provided the surgeon the ability to utilize two independent hands and utilize more traditional and familiar instrumentation in contrast to the traditional uniportal techniques. This technique helped facilitate expansion of indications of endoscopic spine surgery. Fortunately, w it h t he abilit y to make more complex instruments smaller, similar pathologies Winter 2020
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can now be addressed using both uniportal and biportal techniques, allowing surgeons to capitalize on the advantages and disadvantages of each. If an uniportal approach is undertaken, surgical techniques can vary depending on whether a transforminal or an interlaminar approach is used. During the transforaminal approach, f luoroscopic guidance is used in both planes to advance a localization needle to the Kambin triangle. After successful docking of the needle in the triangle, various dilating tubes and, eventually, an endoscope is introduced over the needle. If utilizing the intralaminar approach, the needle is advanced from the midline within the interlaminar space to advance toward the ligamentum flavum-laminar junction. Again, various dilators and eventually the endoscope is introduced. Direct visualization of the pathological site is accomplished isass.org
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with continuous irrigation of the space w ith a saline solution. As for biportal techniques, localization is similar to tubular-based minimally invasive spinal procedures with a 4- to 6-mm incision in contrast to a 16- to 22-mm incision for tubular surgeries; however, the latter includes a small 4-mm viewing portal placed proximal to the working portal. Regardless of which approach is undertaken, endoscopic lumbar procedures are particularly exciting as they allow surgeries to be completed under minimal sedation and local anesthesia in a more minimally invasive method. As seen with endoscopic transforaminal lumbar technology, innovation and new instrumentation continue to facilitate progress. Today, high-resolution cameras are small, offering various angle options to maximize direct visualization while minimizing muscular trauma. Furthermore, endoscopic spine surgeons are
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“Regardless of which approach is undertaken, endoscopic lumbar procedures are particularly exciting as they allow surgeries to be completed under minimal sedation and local anesthesia in a more minimally invasive method.” now able to tackle other spinal pathologies with ease, such as those that require fusion. As these innovations continue to improve, we expect to see endoscopic spine surgery elevate our current standards of care for minimally invasive surgery. This avenue of lessening perioperative morbidity will assuredly have applications with ambulatory surgery, increased levels of patient satisfaction, and new procedural techniques that we have yet to realize. n
References 1. Hasan S, Härtl R, Hofstetter CP. The benefit zone of full-endoscopic spine surgery. J Spine Surg. 2019;5(suppl 1):S41-S56. doi:10.21037/jss.2019.04.19 2. Fenn J, Raskino M. Mastering the Hype Cycle: How to Choose the Right Innovation at the Right Time. Harvard Business Press; 2008. 3. Kambin P. Arthroscopic microdiscectomy. Arthroscopy. 1992;8(3):287-295. doi:10.1016/0749-8063(92)90058-j 4. Hijikata S, Yamagishi M, Nakayma T. Percutaneous discectomy: a new treatment method for lumbar disc herniation. J Toden Hosp. 1975;5:5-13.
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5. Forst R, Hausmann B. Nucleoscopy—a new examination technique. Arch Orthop Trauma Surg. 1983;101(3):219-221. 6. Frymoyer JW. Arthroscopic microdiscectomy: minimal intervention in spinal surgery. J Bone Joint Surg. 1991;73(4):638. doi:10.2106/00004623-199173040-00039 7. Ruetten S, Komp M, Godolias G. A new full-endoscopic technique for the interlaminar operation of lumbar disc herniations using 6-mm endoscopes: prospective 2-year results of 331 patients. Minim Invasive Neurosurg. 2006;49(2):8087. doi:10.1055/s-2006-932172
8. Kambin P, Gennarelli T, Hermantin F. Minimally invasive techniques in spinal surgery: current practice. Neurosurg Focus. 1998;4(2):e8. 9. Choi CM, Chung JT, Lee SJ, Choi DJ. How I do it? Biportal endoscopic spinal surgery (BESS) for treatment of lumbar spinal stenosis. Acta Neurochir. 2016;158(3):459463. doi:10.1007/s00701-015-2670-7 10. Eum JH, Heo DH, Son SK, Park CK. Percutaneous biportal endoscopic decompression for lumbar spinal stenosis: a technical note and preliminary clinical results. J Neurosurg Spine. 2016;24(4):602607. doi:10.3171/2015.7.spine15304
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Rare Complications of Lateral Surgery Avani Vaishnav, MBBS
Catherine Himo Gang, MPH
Sheeraz Qureshi, MD, MBA
Interbody fusion using a lateral approach is a commonly utilized surgical technique for the management of a variet y of degenerative and deformity conditions of the thoracolumbar spine. Despite its widespread use since its introduction by Ozgur et al1 in 2006, the lateral approach is associated with a number of approach-related complications owing to the close proximity of the lumbar plexus, sympathetic chain, and large vessels. 2 Although the most common complications are anterior thigh pain and hip flexor weakness, which are transient in a majority of patients, this approach carries the risk of several rare complications such as abdominal visceral injury and major vessel injury. We review the incidence, diagnosis, treatment, and outcomes of some of these rare complications of lateral surgery.
Femoral Nerve Palsy Although transient anterior thigh pain is a common complication of the lateral approach to the spine, it is often attributed to edema of the psoas muscle rather than injury to Winter 2020
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the nerve roots. In contrast, femoral nerve injury resulting in quadriceps weakness is a rare occurrence, with reported rates in a large systematic review being less than 1% 3; therefore, it is often not seen in smaller studies. In a series of 201 operative levels in 118 patients, Cahill et al4 reported 2 cases of femoral nerve injury—one during a multilevel procedure and the second during a single-level fusion—occurring during psoas muscle dilation to approach the L4-L5 disc space. Thus, this series reported an incidence of 1.7% for the entire cohort, but a higher rate of 4.8% for the L4-L5 level. In both of these cases, femoral nerve compromise was recognized by continuous electromyographic monitoring during psoas muscle dilation; because a safe zone for the approach could not be identified, both cases were aborted. Although the patient undergoing single-level fusion had improvement of quadriceps strength to 4/5 by discharge and complete resolution by 3 months, the patient who underwent multilevel surgery had weakness in the iliopsoas (grade 3/5) and quadriceps (grade 1/5), which required inpatient and outpatient rehabilitation and ambulation with a walker, and eventually resulted in quadriceps atrophy. The muscle weakness and associated decrease in patellar reflex were persistent at 9-month follow-up. isass.org
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A series of 58 patients by Knight et al5 also had 2 cases (3.4%) of ipsilateral L4 nerve root injury; however, the postoperative course of these patients is not described in this report. Le et al6 described the incidence of 1 case (1.4%) of quadriceps weakness (grade 2/5) due to femoral neuropathy, which showed complete recovery by 9 months. In a large study of 600 cases, Rodgers et al7 found only 3 cases (0.5%) of quadriceps weakness, all of which occurred with surgery at L4-L5 and resolved by 3 months. Pimenta et al8 reported 1 case (3.6%) of ipsilateral leg weakness following a lateral approach of lumbar disc replacement, Sembrano et al9 reported 1 case (3.4%) of femoral neuropathy resulting in distal weakness, and Anand et al10 reported quadriceps palsy in 2 of 28 patients (7.1%), all of which resolved by 6 months. A similar rate of 6.8% for quadriceps weakness was reported by Cummock et al11; however, the authors reported only mild weakness in all cases and suggest that this weakness does not necessarily indicate femoral nerve injury. In a small series by Tormenti et al,12 2 of the 8 patients in whom the transpsoas approach was used for scoliosis correction experienced motor radiculopathy; 1 patient had resolution of symptoms by 2 months, whereas the other had persistent weakness at the 3-month follow-up. In contrast, Malham et al 13 had 1 case (1.9%) in a series of 52 patients and Na et al14 reported 1 case in 30 patients of quadr iceps wea k ness due to lumbar plex us injury, which had not resolved by the last follow-up. Houten et al15 reported 2 cases of femoral nerve injury resulting in quadriceps isass.org
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weakness, neither of which were detected by intraoperative neuromonitoring. The diagnosis was made by clinical examination postoperatively and electromyography findings. Although both cases showed an improvement in muscle strength at follow-up of 16 to 20 months, neither had complete recovery of motor strength. Sofianos et al16 also found quadriceps weakness in 3 (6.7%) of 45 patients, of whom only 1 showed complete recovery by a mean follow-up of 21 months. Similarly, Grimm et al17 reported 1 case (0.9%) of femoral nerve neuropraxia that was not detected by intraoperative neuromonitoring, and though there was an improvement to 4/5 st reng t h in t he quadriceps at 1 year, complete resolution did not occur. Isaacs et al18 also report 1 case (0.9%) of severe quadriceps weakness (grade 1/4), which improved to 4/5 at 6 months but did not return to full strength during the follow-up. While ipsilateral femoral nerve injury may be expected as an approach-related complication, Papanastassiou et al19 reported a rare complication of contralateral femoral nerve injury. In their series of 32 patients, 2 patients developed contralateral femoral nerve palsy due to displaced endplate fragment and far lateral disc fragment, respectively. Both patients required reoperation to remove the compressive fragments, after which they had complete resolution of symptoms.
Pseudohernia A study of motor ner ve injuries during the lateral transpsoas approach 4 reportVertebral Columns
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“The lateral approach is associated with a number of approach-related complications owing to the close proximity of the lumbar plexus, sympathetic chain, and large vessels.�
ed the development of a pseudohernia (ie, abdom i na l wa l l bu lg i ng without a defect in abdominal wall musculature) in 5 patients (4.2%). In contrast, Dak war et al 20 reported a lower incidence of 1.8% (10 out of 568 cases) of abdominal wall paresis, resulting in pseudohernia. In both these studies, the diagnosis was made by cl i n ica l eva luat ion i n the postoperative period, and abdominal CT scans were performed in some cases to confirm the absence of a true wall defect. While the former report did not describe the management of these cases, the latter stated that all patients were treated conservatively, with resolution of symptoms in all but 2 patients by the 6-month follow-up; the 2 patients who did not have resolution of symptoms were lost to follow-up in the early postoperative period, as a result of which the remainder of their clinical course could not be ascertained. Choi et al 21 also describe, in their case report, the incidence of a post-operative f lank bulge, which demonstrated a dermatomal pattern that worsened with an increase in intra-abdominal pressure and was associated with hypoesthesia. Similar to the above reports, the CT scan demonstrated an intact but thinned abdominal muscle wall, without any muscular defect
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or bowel herniation. The authors reported no improvement of this complication at 17-month follow-up.
Injury to Abdominal Viscera Injury to abdominal viscera is a rare complication, with systematic reviews and meta-analyses reporting an incidence of 0.4% to 1.3% for bowel injury. 3,22 A survey of 40 surgeons,23 who had collectively performed more than 13,000 lateral interbody fusions, reported a much lower rate of 0.08% (11 of 13,004 cases), with a little less than half being diagnosed intraoperatively and the rest in the early postoperative period. In the survey results, a majority of patients required a laparotomy, and some were managed with a colostomy. At long-term follow-up, only half of these patients had a complete recovery. In a large series of 163 patients, Kim et al 24 reported 1 (0.8%) case of bowel perforation in a cohort of patients who underwent 1-4 level lateral lumbar interbody fusion. However, the study did not describe the management and clinic course of this complication. Tormenti et al12 reported 1 case (in a series of 8 patients) of cecal perforation that occurred during the lateral transpsoas approach for deformity correction. The surgery was aborted and an emergency laparotomy and segmental bowel resection was performed; 6 months later, the patient underwent a posterior-only approach for deformity correction. Balsano et al 25 described a case of colonic splenic flexure injury, which was not diagnosed intra-operatively, and presented with nausea, abdominal pain, and distension on postoperative day 1, with subsequent imaging isass.org
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revealing free air in the peritoneal cavity. Temporary colostomy, followed by closure at 3 months, was performed, with full recovery and restoration of normal bowel function. Rustagi et al 26 reported 3 cases (out of 590 patients; 0.5%) of bowel injury following a lateral transpsoas approach to the lumbar spine, none of which were apparent intraoperatively. All patients developed abdominal distension and pain in the early postoperative course, with CT scans demonstrating a collection of air in the retroperitoneal space. All 3 patients required emergency laparotomy with debridement and partial bowel resection, after which end-to-end anastomosis was performed in 2 patients and a diverting ileostomy in the third, which was closed at 4 months. Although 1 patient developed a leak in the anastomosis requiring a reoperation, none of the patients had any long-term sequelae.
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A rare complication, reported by Isaacs et al,18 is an intraoperative kidney laceration, which occurred in 1 of 107 patients (0.9%) and required a stay in the intensive care unit (ICU). Additional details regarding this complication were not described. Similarly, Anand and Baron 27 reported 3 cases of intraoperative urologic injury occurring during lateral lumbar interbody fusion. The first case occurred during instrumentation at T12-L1, resulting in brisk bleeding, which was later identified to be originating from a laceration of the superficial kidney capsule. The attending vascular surgeon determined that because the hematoma was contained, there was no active bleeding and the patient was hemodynamically stable, no further intervention was required. The only longterm sequela was an asymptomatic superior pole infarction. The other 2 cases were of ureteric injury, 1 of which was suspected
References 1. Ozgur BM, Aryan HE, Pimenta L, Taylor WR. Extreme lateral interbody fusion (XLIF): a novel surgical technique for anterior lumbar interbody fusion. Spine J. 2006;6(4):435-443. doi:10.1016/j.spinee.2005.08.012
4. Cahill KS, Martinez JL, Wang MY, Vanni S, Levi AD. Motor nerve injuries following the minimally invasive lateral transpsoas approach. J Neurosurg Pediatr. 2012;17(3):227-231. doi:10.3171/2012.5.SPINE1288
7. Rodgers WB, Gerber EJ, Patterson J. Intraoperative and early postoperative complications in extreme lateral interbody fusion: an analysis of 600 cases. Spine (Phila Pa 1976). 2011;36(1):26-32. doi:10.1097/BRS.0b013e3181e1040a
2. Lang G, Perrech M, Navarro-Ramirez R, et al. Potential and limitations of neural decompression in extreme lateral interbody fusion—a systematic review. World Neurosurg. 2017;101:99113. doi:10.1016/j.wneu.2017.01.080
5. Knight RQ, Schwaegler P, Hanscom D, Roh J. Direct lateral lumbar interbody fusion for degenerative conditions: early complication profile. J Spinal Disord Tech. 2009;22(1):34-37. doi:10.1097/BSD.0b013e3181679b8a
8. Pimenta L, Oliveira L, Schaffa T, Coutinho E, Marchi L. Lumbar total disc replacement from an extreme lateral approach: clinical experience with a minimum of 2 years’ follow-up. J Neurosurg Spine. 2011;14(1):3845. doi:10.3171/2010.9.SPINE09865
3. Hijji FY, Narain AS, Bohl DD, et al. Lateral lumbar interbody fusion: a systematic review of complication rates. Spine J. 2017;17(10):1412-1419. doi:10.1016/j.spinee.2017.04.022
6. Le TV, Burkett CJ, Deukmedjian AR, Uribe JS. Postoperative lumbar plexus injury after lumbar retroperitoneal transpsoas minimally invasive lateral interbody fusion. Spine (Phila Pa 1976). 2013;38(1):13-20. doi:10.1097/BRS.0b013e318278417c
9. Sembrano JN, Tohmeh A, Isaacs R. Two-year comparative outcomes of MIS lateral and MIS transforaminal interbody fusion in the treatment of degenerative spondylolisthesis. Spine (Phila Pa 1976). 2016;41:s123-s132. doi:10.1097/BRS.0000000000001471
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intraoperatively and the other was not. Both patients had ureteric disruption and hydronephrosis, which required emergent ureteric stent placement. Although the patient in whom ureteric injury was suspected intraoperatively did not have any long-term complications, the other patient developed postoperative ascites, which was found to be urine based, thus requiring nephrostomy tube placement. At 11 months postoperatively, both the ureteric stent and nephrostomy tube were removed and the patient’s renal function was normal.
Major Vascular Injury Although a few studies have reported the incidence of segmental artery injury, 28-30 major vessel injury remains a rare occurrence. This is further evidenced by the fact that a systematic review 3 reported rates of 0.12% and 0.25% for aortic injury and iliac
vein laceration, respectively; a meta-analysis reported an incidence of 0.4% for major vascular injury; and a survey of 40 surgeons23 reported great vessel injury in only 10 of 13,004 cases (0.08%). In the survey, half the cases required surgical repair, whereas the other half could be managed with application of a hemostatic matrix alone. No mortality or long-term sequelae were reported. Assina et al31 reported a case of a massive retroperitoneal hemorrhage due to vascular injury occurring during an eXtreme Lateral Interbody Fusion (XLIF) procedure at an ambulatory surgery center. The injury likely resulted from ventral displacement of the detachable anterior blade of a Scoville-type retractor, which caused brisk venous bleeding and necessitated emergent transfer to a hospital for vascular repair. After evacuation of the hematoma, in addition to a large defect in the right common iliac vein, which was
References 10. Anand N, Rosemann R, Khalsa B, Baron EM. Mid-term to long-term clinical and functional outcomes of minimally invasive correction and fusion for adults with scoliosis. Neurosurg Focus. 2010;28(3):E6. doi:10.3171/2010.1.FOCUS09272 11. Cummock MD, Vanni S, Levi AD, Yu Y, Wang MY. An analysis of postoperative thigh symptoms after minimally invasive transpsoas lumbar interbody fusion. J Neurosurg Spine. 2011;15(1):1118. doi:10.3171/2011.2.SPINE10374 12. Tormenti MJ, Maserati MB, Bonfield CM, Okonkwo DO, Kanter AS. Complications and radiographic correction in adult scoliosis following combined transpsoas extreme lateral interbody fusion and posterior pedicle screw instrumentation. Neurosurg Focus. 2010;28(3):1-7.
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doi:10.3171/2010.1.FOCUS09263 13. Malham GM, Parker RM, Goss B, Blecher CM, Ballok ZE. Indirect foraminal decompression is independent of metabolically active facet arthropathy in extreme lateral interbody fusion. Spine (Phila Pa 1976). 2014;39(22):E1303-E1310. doi:10.1097/BRS.0000000000000551 14. Na YC, Lee HS, Shin DA, Ha Y, Kim KN, Yoon DH. Initial clinical outcomes of minimally invasive lateral lumbar interbody fusion in degenerative lumbar disease: a preliminary report on the experience of a single institution with 30 cases. Korean J Spine. 2012;9(3):187. doi:10.14245/kjs.2012.9.3.187
15. Houten JK, Alexandre LC, Nasser R, Wollowick AL. Nerve injury during the transpsoas approach for lumbar fusion: report of 2 cases. J Neurosurg Spine. 2011;15(3):280-284. doi:10.3171/2011.4.SPINE1127 16. Sofianos DA, BriseĂąo MR, Abrams J, Patel AA. Complications of the lateral transpsoas approach for lumbar interbody arthrodesis: a case series and literature review. Clin Orthop Relat Res. 2012;470(6):1621-1632. doi:10.1007/s11999-011-2088-3 17. Grimm BD, Leas DP, Poletti SC, Johnson DR. Postoperative complications within the first year after extreme lateral interbody fusion experience of the first 108 patients. Clin Spine Surg. 2016;29(3):E151-E156. doi:10.1097/BSD.0000000000000121
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responsible for the massive hemorrhage, a large defect was also seen in the left common iliac vein and small perforations of the inferior vena cava and right internal and external iliac veins were found. Although the inferior vena cava and left common iliac vein could be repaired, the right common iliac vein could not be salvaged. Following a complicated postoperative course of 4 weeks requiring ICU admissions, numerous re-operations, and acute care rehabilitation, the patient developed a retroperitoneal abscess and bacteremia, which progressed to septic shock and multi-organ failure, and subsequently, the patient’s death. This report underscores the importance of appropriate patient selection and the use of diligent surgical technique and highlights a rare but potentially catastrophic complication of this approach. A case report by Aichmair et al32 describes the incidence of aortic perforation in a case
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“Major vessel injury remains rare, with 40 surgeons reporting such injury in only 10 of more than 13,000 cases.” of L2-L5 lateral lumbar interbody fusion. The authors reported that an attempt to advance a broken and impacted cage at L3-L4 resulted in an incidental violation of the endplate and anterior vertebral cortex, which was accompanied by a drop-in blood pressure; a presumptive diagnosis of major vascular injury was made. An emergency laparotomy was performed for evacuation of the retroperitoneal hematoma and vascular repair; during the laparotomy, an aortic perforation was determined to be the source of bleeding. After closure of the laparotomy wound, the lateral wound was explored to remove the remaining interbody cage and insert bone morphogenetic protein-2 into the disc
References 18. Isaacs RE, Hyde J, Goodrich JA, Rodgers WB, Phillips FM. A prospective, nonrandomized, multicenter evaluation of extreme lateral interbody fusion for the treatment of adult degenerative scoliosis: perioperative outcomes and complications. Spine (Phila Pa 1976). 2010;35(suppl 26S):322-330. doi:10.1097/BRS.0b013e3182022e04 19. Papanastassiou ID, Eleraky M, Vrionis FD. Contralateral femoral nerve compression: an unrecognized complication after extreme lateral interbody fusion (XLIF). J Clin Neurosci. 2011;18(1):149151. doi:10.1016/j.jocn.2010.07.109
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20. D akwar E, Le T V, Baaj AA, et al. Abdominal wall paresis as a complication of minimally invasive lateral transpsoas interbody fusion. Neurosurg Focus. 2011;31(4):3134. doi:10.3171/2011.7.FOCUS11164 21. Choi J-H, Jang J-S, Jang I-T. Abdominal flank bulging after lateral retroperitoneal approach: a case report. NMC Case Rep J. 2017;4(1):23-26. doi:10.2176/nmccrj.cr.2016-0084 22. Walker CT, Harrison Farber S, Cole TS, et al. Complications for minimally invasive lateral interbody arthrodesis: a systematic review and meta-analysis comparing prepsoas and transpsoas approaches. J Neurosurg Spine. 2019;30(4):446460. doi:10.3171/2018.9.SPINE18800
23. U ribe JS, Deukmedjian AR. Visceral, vascular, and wound complications following over 13,000 lateral interbody fusions: a survey study and literature review. Eur Spine J. 2015;24:386-396. doi:10.1007/s00586-015-3806-4 24. K im SJ, Lee YS, Kim YB, Park SW, Hung VT. Direct lateral lumbar interbody fusion: clinical and radiological outcomes. J Korean Neurosurg Soc. 2014;11(3):145151. doi:10.14245/kjs.2014.11.3.145248 25. B alsano M, Carlucci S, Ose M, Boriani L. A case report of a rare complication of bowel perforation in extreme lateral interbody fusion. Eur Spine J. 2015;24(suppl 3):405408. doi:10.1007/s00586-015-3881-6
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“Complication avoidance via careful patient selection, diligent surgical technique, and a high degree of awareness regarding the potential for these complications is imperative.�
space. Although there was intraoperative blood loss of 12 L and the patient required an ICU stay, the remainder of the peri- and the postoperative course was uneventful. Yuan et al, 33 in a series of 34 patients, reported 1 case of renal vein nicking; however, further details regarding this complication are not described. Blizzard et al 34 described a case of rena l i nju r y during lateral access to T12-L1, resulting in significant bleeding, likely from the renal artery while removing the retractor. Following the achievement of hemostasis by the vascular team, the pos-
terior part of the procedure was completed without complications. Although the CT scan demonstrated numerous renal infarctions, the patient remained asymptomatic and maintained normal renal function, and no further intervention was required.
Conclusion Although the complications described above are rare, they can be devastating and, at times, even fatal. A majority of these patients develop long-term sequelae, endure prolonged disability, or experience a long and morbid postoperative course. Thus, complication avoidance via careful patient selection, diligent surgical technique, and a high degree of awareness regarding the potential for these complications is imperative to optimize the outcomes and safety of these procedures. n
References 26. Rustagi T, Yilmaz E, Alonso F, et al. Iatrogenic bowel injury following minimally invasive lateral approach to the lumbar spine: a retrospective analysis of 3 cases. Glob Spine J. 2019;9(4):375382. doi:10.1177/2192568218800045 27. Anand N, Baron EM. Urological injury as a complication of the transpsoas approach for discectomy and interbody fusion: report of 3 cases. J Neurosurg Spine. 2013;18(1):18-23. doi:10.3171/2012.9.SPINE12659 28. L in GX, Akbary K, Kotheeranurak V, et al. Clinical and radiologic outcomes of direct versus indirect decompression with lumbar interbody fusion: a matched-pair comparison analysis. World Neurosurg. 2018;119:e898-e909. doi:10.1016/j.wneu.2018.08.003
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29. S ato J, Ohtori S, Orita S, et al. Radiographic evaluation of indirect decompression of mini-open anterior retroperitoneal lumbar interbody fusion: oblique lateral interbody fusion for degenerated lumbar spondylolisthesis. Eur Spine J. 2017;26(3):671678. doi:10.1007/s00586-015-4170-0 30. K atz AD, Singh H, Greenwood M, Cote M, Moss IL. Clinical and radiographic evaluation of multilevel lateral lumbar interbody fusion in adult degenerative scoliosis. Clin Spine Surg. 2019;32(8):E386-E396. doi:10.1097/BSD.0000000000000812 31. Assina R, Majmundar NJ, Herschman Y, Heary RF. First report of major vascular injury due to lateral transpsoas approach leading to fatality [case report]. J Neurosurg Spine. 2014;21(5):794-798. doi:10.3171/2014.7.SPINE131146
32. A ichmair A, Fantini GA, Garvin S, Beckman J, Girardi FP. Aortic perforation during lateral lumbar interbody fusion. J Spinal Disord Tech. 2015;28(2):71-75. doi:10.1097/BSD.0000000000000067 33. Yuan PS, Rowshan K, Verma RB, Miller LE, Block JE. Minimally invasive lateral lumbar interbody fusion with direct psoas visualization. J Orthop Surg Res. 2014;9(1): 1-4. doi: 10.1186/1749-799X-9-20 34. B lizzard DJ, Gallizzi MA, Isaacs RE, Brown CR. Renal artery injury during lateral transpsoas interbody fusion [case report]. J Neurosurg Spine. 2016;25(4): 464466. doi: 10.3171/2016.2.SPINE15785
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CANCER
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Approach to Treatment of Metastatic Disease in the Spine Spinal involvement is common in metastatic neoplasms and is symptomatic in up to 40% of patients with cancer.1 As survival duration in patients with malignancy improves, the demand for care of patients with spinal metastases is expected to grow. As a result, all spine specialists should have a basic understanding of the approach to diagnosis and treatment of metastatic spinal lesions. Fortunately, recent advances in interdisciplinary management of metastatic disease in the spine now offer improved tumor control with significantly less morbidity than that seen with previous treatment paradigms. The NOMS (neurologic, oncologic, mechanical stability, systemic disease) framework popularized by Bilsky et al 2 provides a systematic guide for the treatment of metastatic lesions to the spine. Neurological evaluation involves both the patient clinical status as well as imaging. Patients may be categorized by having only radicular sensory symptoms, focal versus global weakness, and myelopathy. In the cervical and thoracic spine, advanced imaging (typically with magnetic resonance imaging) is used to determine the degree of spinal cord compression from epidural disease. The Epidural Spinal Cord Compression (ESCC) scale is a validated grading system used to categorize the severity of epidural disease.3 The scale ranges from 0 (intraosseous disease only) to 3 (high grade cord compression withisass.org
out visible spinal fluid about the Brandon P. Hirsch, MD cord). Grade 1 refers to disease that deforms the thecal sac but does not compress the spinal cord and has three sub-grades (1a, b, and c). Grade 2 indicates spinal cord compression/deformation with some spinal f luid visible around the cord. Grades 2 and 3 are considered high-grade compression. In general, the neurological assessment portion of the NOMS framework categorizes patients as having either low grade (0 or 1) or high grade (2 or 3) ESCC either with or without myelopathy. The oncological assessment portion of NOMS refers to tumor type and its radiosensitivity. Historically, hematological tumors (lymphoma, myeloma, plasma cell neoplasms) as well as certain solid organ malignancies (breast, prostate, ovarian, neuroendocrine) have been considered sensitive to conventional radiotherapy. Classically, certain carcinomas (renal cell, colon, non-small cell lung, thyroid, hepatocellular), melanoma, and sarcoma have been thought of as radioresistant. Advances in radiation oncology, primarily the evolution of stereotactic radiosurgery (SRS), continue to transform the concept of tumor radiosensitivity and have revolutionized the treatment approaches for spinal metastases. SRS, also referred to as stereotactic body radiotherapy (SBRT), allows for much higher Vertebral Columns
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doses per fraction than conventional external beam radiotherapy (cEBRT) while minimizing toxicity to the spinal cord. Typically, SBRT is delivered in anywhere from 1 to 3 fractions, whereas cEBRT would require 10 to 20 sessions. Thus, SBRT improves compliance and shortens time to definitive radiation treatment.1 Early consultation with an experienced radiation oncologist is critically important in patients with spinal metastases. The approach to radiation based on histology continues to evolve, but in general, radiosensitive tumor types are treated with cEBRT regardless of the degree of spinal cord compression, whereas radioresistant disease is treated with SRS with or without adjuvant surgery depending on the neurological status of the patient. Mechanical stability is a primary determinant for the role of surgery in metastatic disease regardless of the neurological or oncological status. The Spinal Instability Neoplastic Score (SINS) is a validated scoring system used to assess spinal stability and is based on six factors: location, presence of mechanical pain, lytic versus blastic disease, spinal alignment, degree of vertebral collapse, and involvement of the posterior elements.4 The scale is scored from 0 to 18 with total scores of 0-6 indicating stable lesions not requiring surgical stabilization, 7-12 indicating indeterminate stability, and 13-18 indicating instability requiring reconstruction. Indeterminate lesions may be treated with stabilization in cases of progressive deformity or when pain relief is inadequate after nonsurgical treatment. The systemic disease component of the NOMS framework refers to the assessment of patient comorbidities, disease extent, and Winter 2020
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ability to survive the proposed treatment regimen. Much of this assessment is based on the cardiovascular status of the patient and the disease prognosis (which is in turn based on histology and stage of disease). Advances in targeted systemic therapy continue to redefine the life expectancy of patients with malignancy, making prognostication difficult. The nomogram created by the Skeletal Oncology Research Group can assist in determining survival based on a combination of lab results, patient demographics, performance status, tumor type, disease extent, and history of previous systemic therapy.5,6 This aspect of spine tumor care will continue to rapidly evolve as advances in the understanding of the molecular basis of cancer inform the development of targeted systemic therapies. The role of surgery in the treatment of spinal metastases has evolved significantly as a result of advancements in adjuvant treatment and surgical technique. Prior to these advances, surgical treatment tended to involve aggressive attempts to achieve local tumor control via spondylectomy. Modern surgery for spinal tumors is now aimed at creating a safe target for adjuvant radiotherapy while restoring spinal stability. Today, surgical treatment is used primarily for patients with high-grade epidural disease and radioresistant tumor types or in patients with overt spinal instability and/ or rapidly progressive neurological decline. “Separation surgery� refers to decompression and stabilization procedures that relieve neural compression and create an additional margin between the neural elements (typically the spinal cord) and tumor. This allows for safe delivery of high dose radiotherapy. Separation isass.org
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surgery aims to create at least a 2-mm margin about the spinal cord, which then allows for high-dose hypofractionated radiotherapy. In a landmark study by Laufer et al,7 this approach was found to reduce the rate of local tumor progression at 1 year to 4%, as opposed to 22% with conventional low dose radiotherapy. Further advancements in surgical technique have substantially improved recovery following operative treatment of spinal metastases. Minimally invasive techniques now allow separation surgery to be performed with tubular access techniques and percutaneous instrumentation, reducing surgical morbidity and allowing for earlier initiation of radiotherapy. Cement augmentation is increasingly useful for pain control treatment of stable pathological vertebral fractures.8 In addition, vertebral augmentation is being explored as a less invasive alternative to corpectomy and
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traditional anterior column reconstruction in cases requiring multilevel stabilization.9,10 The treatment approach to metastatic disease in the spine requires a multidisciplinary team including medical oncologists, radiation oncologists, and spine surgeons. The NOMS framework provides a useful guide to thinking about the treatment of this patient population. The role of surgical treatment continues to evolve with advances in targeted radiation and medical therapies. Separation surgery in conjunction with high dose hypofractionated radiation continues to be the mainstay of treatment of high-grade spinal cord compression from radioresistant metastatic spinal tumors. Spine surgeons should maintain communication with and understand the capabilities of their non-surgeon counterparts in order to optimize the outcomes of patients with spinal metastases. n
References 1. Barzilai O, Fisher CG, Bilsky MH. State of the art treatment of spinal metastatic disease. Neurosurgery. 2018;82(6):757769. doi:10.1093/neuros/nyx567 2. Barzilai O, Laufer I, Yamada Y, et al. Integrating evidence-based medicine for treatment of spinal metastases into a decision framework: neurologic, oncologic, mechanical stability, and systemic disease. J Clin Oncol. 2017;35(21):24192427. doi:10.1200/JCO.2017.72.7362 3. Bilsky MH, Laufer I, Fourney DR, et al. Reliability analysis of the epidural spinal cord compression scale. J Neurosurg Spine. 2010;13(3):324-328. doi:10.3171/2010.3.SPINE09459 4. Fisher CG, DiPaola CP, Ryken TC, et al. A novel classification system for spinal instability in neoplastic disease. Spine (Phila Pa 1976). 2010;35(22):E1221-E1229. doi:10.1097/brs.0b013e3181e16ae2
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5. Pereira NR, Janssen SJ, van Dijk E, et al. Development of a prognostic survival algorithm for patients with metastatic spine disease. J Bone Joint Surg Am. 2016;98(21):17671776. doi:10.2106/JBJS.15.00975 6. Paulino Pereira NR, Mclaughlin L, Janssen SJ, et al. The SORG nomogram accurately predicts 3- and 12-months survival for operable spine metastatic disease: external validation. J Surg Oncol. 2017;115(8):10191027. doi:10.1002/jso.24620 7. Laufer I, Iorgulescu JB, Chapman T, et al. Local disease control for spinal metastases following “separation surgery� and adjuvant hypofractionated or high-dose single-fraction stereotactic radiosurgery: outcome analysis in 186 patients. J Neurosurg Spine. 2013;18(3):207-214. doi:10.3171/2012.11.SPINE12111
8. Astur N, Avanzi O. Balloon kyphoplasty in the treatment of neoplastic spine lesions: a systematic review. Global Spine J. 2019;9(3):348-356. doi:10.1177/2192568218768774. 9. Moussazadeh N, Rubin DG, McLaughlin L, et al. Short-segment percutaneous pedicle screw fixation with cement augmentation for tumor-induced spinal instability. Spine J. 2015;15(7):16091617. doi:10.1016/j.spinee.2015.03.037 10. Chang CW, Fu TS, Lin DY, et al. Percutaneous balloon kyphoplasty and short instrumentation compared with traditional long instrumentation for thoracolumbar metastatic spinal cord compression. World Neurosurg. 2019;130:e640-e647. doi:10.1016/j.wneu.2019.06.182
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The Evidence (or Lack Thereof) for Cannabidiol in the Treatment of Spinal Conditions Peter B. Derman, MD, MBA
Cannabidiol (CBD), a nonpsychotropic component of Cannabis, has been promoted as a veritable cure-all in the popular press. An overview of the derivation, molecular underpinnings, and regulatory environment of CBD was provided in the previous edition of Vertebral Columns. But does it have a role in the treatment of spinal pathology? In an effort to shed light on this issue, the literature on the effect of CBD on various spine-related conditions is summarized below.
Disc Degeneration There is some suggestion that CBD exhibits a protective effect on intervertebral discs. An in vitro study found that CBD prevented hydrogen peroxide–induced apoptosis, inflammation, and oxidative stress in cultured rat nucleus pulposus cells.1 In an in vivo rat model of induced disc degeneration, an intradiscal injection of CBD significantly reduced the effects of disc injury as measured on magnetic resonance images and histologic analysis.2 Spinal Cord Injury An experiment utilizing a mouse model of spinal cord injury found that periodic inWinter 2020
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traperitoneal injections of CBD after injury resulted in a decrease in pro-inflammatory cytokine and chemokine expression at 48 hours and a reduction in pathological T cell (but not macrophage or microglia) invasion into the spinal cord at 2 weeks.3 CBD reduced the rate of thermal hypersensitivity but had no effect on recovery of bladder or locomotor function out to 10 weeks from the time of injury.
Bone Healing and Metabolism CBD’s effect on osteoblasts and osteoclasts appears to have implications on bone regeneration. Its administration has been associated with reduced osteoclastic bone resorption by inhibiting RANKL/RANK expression and inflammatory cytokine levels in a rat model of periodontal disease.4 Authors of a rat study of closed midshaft femur fractures observed that CBD enhanced fracture healing by increasing osteoblastic expression of lysyl hydroxylase (an enzyme involved in collagen stabilization and cross-linking).5 Interestingly, the addition of tetrahydrocannabinol attenuated the benefits of CBD. A third rat study determined that daily treatment with CBD for 2 weeks after spinal cord injury was protective against the bone mineral density loss normally observed caudal to the level of injury.6 isass.org
PHARMACEUTICALS
Neuropathic Pain A retrospective review of 11 patients with refractory neuropathic pain in the setting of failed back surgery syndrome despite spinal cord stimulation found that adjuvant administration of a combination of THC and CBD in the absence of any other oral analgesic therapy was successful in reducing numeric pain ratings from 8.18Âą1.07 to 4.72Âą0.9 over a 12-month period.7 A 2018 Cochrane systematic review of cannabis-based medicines (tetrahydrocannabinol and CBD) for the treatment of neuropathic pain in humans found that these substances outperformed placebo for reducing pain, improving sleep, and addressing psychological distress.8 There was no difference in serious side effects, but drowsiness, dizziness, and difficulties with mentation were more common in the cannabis group. However, no high-quality evidence isass.org
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could be identified. The authors concluded that the potential benefits of cannabis-based medicine in patients with chronic neuropathic pain might be outweighed by potential harms. It should be noted that no studies investigating CBD alone (as opposed to in conjunction with other cannabinoids) were identified that met the 2018 Cochrane systematic review inclusion criteria, which limits the ability to draw conclusions on CBD specifically.
Musculoskeletal and Postoperative Pain There is some clinical evidence to suggest that cannabinoids can be effective in the management of back pain, arthritic pain, and trauma-related pain; however, findings are mixed for the treatment of postoperative pain.9 Regardless, the quality of the data is poor, and the existing literature does not focus specifically on CBD. Vertebral Columns
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A limited number of animal studies investigating CBD for the treatment of arthritic and musculoskeletal pain have been performed. An experiment using a murine model of rheumatoid arthritis demonstrated that CBD had a strong protective effect via combined immunosuppressive and anti-inflammatory mechanisms.10 It was equally effective when administered orally or intraperitoneally. In vitro and ex vivo measurements were performed, but no spine-specific data were collected. Additionally, a study utilizing a rat model of postoperative incisional pain demonstrated that CBD administration was effective in reducing mechanical allodynia to the operative site.11
The Bottom Line While CBD has potential therapeutic properties and encouraging early experimental findings in the setting of spine-related pathology, the existing literature is extremely limited and likely suffers from publication bias. As such, it is not currently possible to make evidence-based recommendations in favor of its use. The risk of severe side effects from CBD consumption presently appears to be relatively low. Patients who desire to try it are not likely to be putting themselves at significant risk by doing so but should consult with their internists prior to initiation to ensure that no medical contraindications or medication interactions exist. n
References 1. Chen J, Hou C, Chen X, et al. Protective effect of cannabidiol on hydrogen peroxide–induced apoptosis, inflammation and oxidative stress in nucleus pulposus cells. Mol Med Rep. 2016;14(3):23212327. doi:10.3892/mmr.2016.5513 2. Silveira JW, Issy AC, Castania VA, et al. Protective effects of cannabidiol on lesion-induced intervertebral disc degeneration. PLoS One. 2014;9(12):e113161. doi:10.1371/journal.pone.0113161 3. Li H, Kong W, Chambers CR, et al. The non-psychoactive phytocannabinoid cannabidiol (CBD) attenuates pro-inflammatory mediators, T cell infiltration, and thermal sensitivity following spinal cord injury in mice. Cell Immunol. 2018;329:19. doi:10.1016/j.cellimm.2018.02.016 4. Napimoga MH, Benatti BB, Lima FO, et al. Cannabidiol decreases bone resorption by inhibiting RANK/RANKL expression and pro-inflammatory cytokines during experimental periodontitis in rats. Int Immunopharmacol. 2009;9(2):216-222. doi:10.1016/j.intimp.2008.11.010
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5. Kogan NM, Melamed E, Wasserman E, et al. Cannabidiol, a major non-psychotropic cannabis constituent enhances fracture healing and stimulates lysyl hydroxylase activity in osteoblasts. J Bone Miner Res. 2015;30(10):19051913. doi:10.1002/jbmr.2513 6. Li D, Lin Z, Meng Q, Wang K, Wu J, Yan H. Cannabidiol administration reduces sublesional cancellous bone loss in rats with severe spinal cord injury. Eur J Pharmacol. 2017;809:1319. doi:10.1016/j.ejphar.2017.05.011 7. Mondello E, Quattrone D, Cardia L, et al. Cannabinoids and spinal cord stimulation for the treatment of failed back surgery syndrome refractory pain. J Pain Res. 2018;11:17611767. doi:10.2147/JPR.S166617
9. Madden K, van der Hoek N, Chona S, et al. Cannabinoids in the management of musculoskeletal pain: a critical review of the evidence. JBJS Rev. 2018;6(5):e7. doi:10.2106/JBJS.RVW.17.00153 10. Malfait AM, Gallily R, Sumariwalla PF, et al. The nonpsychoactive cannabis constituent cannabidiol is an oral anti-arthritic therapeutic in murine collagen-induced arthritis. Proc Natl Acad Sci USA. 2000;97(17):95619566. doi:10.1073/pnas.160105897 11. Genaro K, Fabris D, Arantes ALF, Zuardi AW, Crippa JAS, Prado WA. Cannabidiol is a potential therapeutic for the affective-motivational dimension of incision pain in rats. Front Pharmacol. 2017;8:391. doi:10.3389/fphar.2017.00391
8. Mücke M, Phillips T, Radbruch L, Petzke F, Häuser W. Cannabis-based medicines for chronic neuropathic pain in adults. Cochrane Database Syst Rev. 2018;3:CD012182. doi:10.1002/14651858.CD012182.pub2
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BIOLOGICS
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A Review of the Use of Vancomycin Powder in Spine Surgery Surgical site infections (SSIs) are the second most common health care–associated infection (HAI) in the United States. Klevens et al estimated that 290,485 SSIs occurred in the United States in 2002 and that 8,205 of those infections resulted in death.1 SSIs have a profound impact on patient care and often necessitate the need for further surgery. Nationally, SSIs constitute the largest portion of costs related to hospital-acquired infection. The most common organisms involved in SSIs are gram-positive bacteria such as Staphylococcus aureus, Staphylococcus epidermidis, and Enterococcus.2 Of 7,000 SSIs reported to the National Healthcare Safety Network (NHSN) from 2006 through 2008, S. aureus caused 30% of all SSIs.3 The current recommendation for perioperative prophylaxis in spinal surgery is a first or second-generation cephalosporin (or clindamycin for patients with beta-lactam hypersensitivity).1 Several retrospective studies suggest that, in addition to the use of intravenous antibiotics and thorough skin preparation, intrawound vancomycin powder can reduce infection rates following spinal surgery. Although conflicting reports exist, a recent meta-analysis of 10 studies found that patients undergoing spine surgery without vancomycin powder were 3 times more likely to develop an SSI.4 While multiple studies have reported a protective benefit, others have suggested that isass.org
widespread use of intrawound Yu-Po Lee vancomycin may increase the incidence of vancomycin-resistant, gram-negative, or polymicrobial spinal infections. Ghobrial et al presented a single-institution experience of more than 900 contiguous series of cases in which vancomycin powder was routinely placed during surgical closure. 5 Sixty-six patients (6.7%) developed postoperative SSI, and the most common organism among positive wound cultures was S. aureus. There were more than 30 cases (60%) of SSIs with gram-negative organisms in the vancomycin powder group versus 12 cases (21%) in a historical control group that did not receive vancomycin powder. More interestingly, there was a trend toward higher incidence of polymicrobial infections (19%) in their cohort versus the historical control (15%; p=0.96). The study by Ghobrial et al highlights the potential for more virulent super-infections with gram-negative and polymicrobial flora secondary to organism resistance in the context of broad-spectrum antibiotic usage. A study by Chotai et al in 2017 reported single-center experience with the routine administration of intrawound vancomycin powder.6 Across 2,802 patients, vancomycin powder use lowered SSI rates from 2.5% Vertebral Columns
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to 1.6% (p=0.02). There was a significantly lower rate of S. aureus SSIs in the treatment group (32% vs 65%, p=0.003).6 While there was no growth of vancomycin-resistant S. aureus, there was a higher incidence of gram negative SSIs (28%, n=7, vs 13%, n=5) in the treatment cohort. Culture profiles were markedly different (p=0.003) in proportion to the vancomycin group, with a higher proportion of Escherichia coli, pseudomonas, Citrobacter, Klebsiella, and Serratia organisms. Furthermore, more patients with gram-negative SSIs (27%) required chronic suppressive antibiotic therapy versus those with gram-positive SSIs (12%). This finding underscores the clinically relevant adverse implication of gram-negative SSIs in the setting of routine vancomycin powder prophylaxis. With widespread use of vancomycin powder, there is also the concern for generalized microbial selection pressure in both the experimental cohorts and control cohorts. Hey et al compared the SSI profiles of their vancomycin powder (n=117) and control groups (n=272).7 Out of 19 SSIs (18 controls, 1 experimental),
there was a predominance of gram-negative organisms (Klebsiella, P. aeruginosa) in the control group. The authors describe this concerning finding as a byproduct of microbial evolution with routine vancomycin powder use in spine surgery. Ultimately, the routine use of vancomycin powder may select for more gram-negative and polymicrobial organisms, causing us to treat for these organisms as well address in our surgical prophylaxis regimen. This could lead to even greater antibiotic use and the development of additional antibiotic-resistant organisms. Vancomycin powder has the abilit y to reduce SSIs, but those benefits come with a risk. Intrawound vancomycin should likely be restricted to procedures and patients most at risk for infection. If vancomycin powder use is continued routinely, it could select for gram-negative and polymicrobial SSIs. This could lead to the use of even more antibiotics. In the interest of good antibiotic stewardship, vancomycin powder should be used judiciously so that we can maintain control of SSIs and infection-causing organisms. n
References 1. Klevens RM, Edwards JR, Richards CL Jr, et al. Estimating health care-associated infections and deaths in U.S. hospitals, 2002. Public Health Rep. 2007;122(2):160-166.
annual summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2006-2007. Infect Control Hosp Epidemiol. 2008;29(11):996-1011.
2. Fang A, Hu SS, Endres N, Bradford DS. Risk factors for infection after spinal surgery. Spine (Phila Pa 1976). 2005;30(12):1460-1465.
4. Khan NR, Thompson CJ, DeCuypere M, et al. A meta-analysis of spinal surgical site infection and vancomycin powder. J Neurosurg Spine. 2014;21(6):974-983.
3. Hidron AI, Edwards JR, Patel J, et al. NHSN annual update: antimicrobial-resistant pathogens associated with healthcare-associated infections:
5. Ghobrial GM, Thakkar V, Andrews E, et al. Intraoperative vancomycin use in spinal surgery: single institution experience and microbial trends. Spine
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(Phila Pa 1976). 2014;39(7):550-555. 6. Chotai S, Wright PW, Hale AT, et al. Does intrawound vancomycin application during spine surgery create vancomycin-resistant organism? Neurosurgery. 2017;80(5):746-753. 7. Hey HW, Thiam DW, Koh ZS, et al. Is intraoperative local vancomycin powder the answer to surgical site infections in spine surgery? Spine (Phila Pa 1976). 2017;42(4):267-274.
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TECHNOLOGY
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Augmented and Virtual Reality in Spine Surgery: Where We Are Now and Where We Might Be Headed Just before Christmas, on December 23, 2019, the US Food and Drug Administrat ion (FDA) g ranted 510(k) clearance to Augmedics for “Xvision,” an augmented reality (AR) system that allows surgeons to visualize three-dimensional anatomy using a “heads-up” display. The approval of this technology marks an important inflection point in the clinical adoption of AR and virtual reality (VR) products—the future tense that is often used to discuss these technologies may no longer be appropriate. Before we discuss the future of AR and VR, however, it is important to recognize that these terms refer to different concepts: AR overlays relevant data on “real life” images, whereas VR creates an immersive artificial environment. In the case of spine surgery, VR uses preoperative imaging (computed tomography and magnetic resonance imaging) to create an immersive, interactive, three-dimensional model that can be used to visualize, plan, and simulate key steps of a procedure. AR, on the other hand, uses the principles of navigation in conjunction with “heads-up display” to overlay imaging data on the patient anatomy during surgery. This allows the surgeon to visualize key anatomic isass.org
Sravisht Iyer, MD
structures (eg, the medial wall of the pedicle) that are usually “hidden” from view during dissection and instrumentation. As a result of this distinction, most current applications of VR have focused on preoperative planning and medical education. In spine surgery, several studies have been performed comparing VR to more “traditional” methods of instruction. These studies have uniformly shown increased screw accuracy, screw placement technique, and understanding of three-dimensional anatomy with the use of VR.1-3 This finding is largely in keeping with data from various other surgical specialties that highlight the value of VR in surgical education. The airline industry and medicine are often compared during discussions of medical errors; the same comparisons may soon be made with regards to training as well. For example, residents may be required to log a minimum number of simulator hours before they are given the reins in the operating room. Several companies have developed VR platforms that have been or are currently Vertebral Columns
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being used in spine surgery; these include: Osso VR (Boston, MA), ImmersiveTouch (Chicago, IL), and Proprio (Seattle, WA). While Osso VR and ImmersiveTouch focus on VR modeling and education, Proprio seeks to leverage machine learning and net worked camera arrays to create V R environments as well as AR applications. While VR represents a valuable adjunct for training, AR represents an important new clinical tool. Current-generation of AR systems represent a natural extension of intraoperative navigation. These systems utilize a fiducial marker (such as a spinous process clamp) and an external camera in conjunction w ith three-dimensional intraoperative imaging. Once t he f iducial marker is placed and intraoperative imaging is obtained, the camera can be used to calibrate and nav igate various instruments. Winter 2020
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Where AR differs from traditional navigation, though, is how this information is conveyed to surgeons. Instead of looking at an external monitor, AR delivers this information directly to the surgeons’ field of view via a head-mounted display or microscope; this allows the surgeon to access the navigation data and understand the position of their instrument without ever looking away from the surgical field. This is no small advantage; it allows the surgeon to better integrate haptic feedback, minimizes attention shift, and reduces the learning curve associated with navigation—“X-ray vision,” as the promotional materials put it. Much of the existing data using AR (including much of the validation for Xvision) has focused on pedicle screw placement. These data are valuable “proof of concept” and uniformly show that AR-based technologies can be used to place pedicle screws isass.org
TECHNOLOGY
with an accuracy (~95%) that is similar to conventional nav igation and free-hand techniques.4-6 This application is certainly the first of several important applications for AR in spine surgery. As minimally invasive approaches continue to grow in popularity, having a thorough, intuitive understanding of the spine in a three-dimensional space becomes increasingly important. AR has been used in cranial neurosurgery for various pathologies ranging from aneurysms, arteriovenous malformations, and tumors. For example, Mascitelli et al7 used Brain Lab Curve along with an intraoperative microscope. The Brainlab Smartbrush was used preoperatively to highlight areas of interest, which were then displayed to the surgeons intraoperatively using a heads-up display or microscope. It is not difficult to conceive of a similar technique being used to tag hypertrophic ligamentum or facet with the areas of interest then being
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highlighted for surgeons on a microscope or endoscopy screen. Indeed, as spine surgery moves to a less invasive future, it is prescient to see how AR is being used in fields such as interventional cardiology. In these cases, companies such as SentiAR (St. Louis, MO) are using AR to provide surgeons with a real-time holographic visualization of patient anatomy, which may allow surgeons a better understanding of patients’ arrhythmia and allow them to target their ablation appropriately. A similar technique could be used, for example, to visualize the lumbar plexus during lateral approaches or even for visualizing reciprocal change during deformity correction (eg, changes in the upper thoracic spine during a T10-pelvis case). While some of the examples provided will probably be the “flying car” of spine surgery 20 years from now, the approval of the first AR platform in spine surgery makes it fun to dream. n
References 1. Gasco J, Patel A, Ortega-Barnett J, et al. Virtual reality spine surgery simulation: an empirical study of its usefulness. Neurolog Res. 2014;36(11):968-973. 2. Archavlis E, Schwandt E, Kosterhon M, et al. A modified microsurgical endoscopic-assisted transpedicular corpectomy of the thoracic spine based on virtual 3-dimensional planning. World Neurosurg. 2016;91:424-433. 3. Gottschalk MB, Yoon ST, Park DK, Rhee JM, Mitchell PM. Surgical training using three-dimensional simulation in placement of cervical lateral mass screws: a blinded randomized control trial. Spine J. 2015;15(1):168-175.
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4. Molina CA, Theodore N, Ahmed AK, et al. Augmented reality–assisted pedicle screw insertion: a cadaveric proof-of-concept study. J Neurosurg Spine. 2019;31(1):139-146. 5. Elmi-Terander A, Burstrom G, Nachabe R, et al. Pedicle screw placement using augmented reality surgical navigation with intraoperative 3D imaging: a first in-human prospective cohort study. Spine. 2019;44(7):517-525.
6. Gibby JT, Swenson SA, Cvetko S, Rao R, Javan R. Head-mounted display augmented reality to guide pedicle screw placement utilizing computed tomography. Int J Comput Assist Radiol Surg. 2019;14(3):525-535. 7. Mascitelli JR, Schlachter L, Chartrain AG, et al. Navigation-linked headsup display in intracranial surgery: early experience. Oper Neurosurg (Hagerstown). 2018;15(2):184-193.
Vertebral Columns
Winter 2020