Vertebral Columns, Spring 2018

Vertebral Columns International Society for the Advancement of Spine Surgery

Spring 2018

Street art in Toronto, Home of ISASS18

In This Issue EDITORIAL Outpatient Spine Surgery: Safe, Efficient and Here to Stay................... 3 COMPLICATIONS Reduction of Intraoperative Blood Loss in Spine Surgery...................... 5 NEW TECHNOLOGY A Single-Use, Disposable Implant System for Thoracolumbar Fixation Surgery by Innovative Surgical Designs................................................. 7 REVIEW Expandable Cages: A Review..................................................................9 IMPROVEMENT Thoracic Myelopathy - You Find What You Look For......................... 13 CASE CHALLENGE Case Challenge: A Sacral Tumor.......................................................... 16

Editor in Chief Kern Singh Editorial Board Matthew Colman, MD Jeffrey Goldstein, MD Jonathan Grauer, MD Hamid Hassanzadeh, MD Safdar Khan, MD Mark Kurd, MD Yu-Po Lee, MD John O’Toole, MD Alpesh Patel, MD Sheeraz Quereshi, MD Kris Siemionow, MD Seth Williams, MD Publisher Jonny Dover Vertebral Columns is published quarterly by the International Society for the Advancement of Spine Surgery. © 2018 ISASS. All rights reserved.

Opinions of authors and editors do not necessarily reflect positions taken by the Society.

This publication is available digitally at http://vertebralcolumns.com.

ISSN 2414-6277.

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EDITORIAL

Outpatient Spine Surgery: Safe, Efficient and Here to Stay Brittany E. Haws, BS Benjamin Khechen, BA Kern Singh, MD With the rapid growth of outpatient surgery centers, the topic of patient safety in this setting has come under increased scrutiny. Outpatient centers have provided patients with a convenient and cost-effective alternative to a hospital setting for surgeries with minimal risk of complication. With technological and medical advances, procedures in many disciplines once thought to be unsuited for the outpatient arena are increasingly adapted for use in this environment thereby favorably bending the healthcare cost-curve.

The benefits of outpatient surgery are substantial. Outpatient surgery centers are more easily accessible than large hospital facilities, and the streamlining of services allows for maximum efficiency and minimal wait times. These advantages have led to outpatient surgery centers achieving an overall patient satisfaction rate of 92%.1 Additionally, outpatient surgery is cost effective, with a $2.6 billion annual saving to Medicare alone. With the employment of specialized staff, outpatient surgery centers are able to focus on providing the highest quality and level of care for patients.

Regardless of operative setting, a surgeon must always be prepared for potential complications. This is particularly important in the outpatient setting, where the resources of

a full hospital are not always available. In this setting, the management plan must be more extensive to ensure all necessary equipment is on hand and staff members are prepared and capable of handling any potential life-threatening complications. Furthermore, physicians should to have an action plan designed to expedite hospital transport at the first sign of impending harm.

A recent article published in USA Today, written by Christina Jewett from Kaiser Health News and Mark Alesia from the IndyStar, brings particular attention to the risk of cervical hematoma after outpatient cervical spine surgery.2 The authors describe a greater risk for rare complications such as a cervical hematoma in the outpatient setting, however, only anecdotal evidence was presented. Though rare, a cervical hematoma can develop in the first few hours after surgery. For this reason, patients in the outpatient setting are monitored closely during the immediate postoperative period so emergent treatment can be initiated if needed.

A recent article by McClelland, et al. analyzed complication rates after outpatient cervical spine fusions among all published reports from 1996-20163. In a total of 2448 patients, the overall complication rate was 1.8% and the mortality rate was only 0.1%. Notably, these rates are much lower than those reported for hospital-performed procedures which can be as high as 5%. One in-

vestigation into outpatient surgery safety reported a 0.095% adverse event rate in 244,297 outpatient procedures.4 Other studies have reported rates of major perioperative morbidity ranging from 0.09% to 0.6% for common outpatient procedures.5-7 While concerns are often expressed over the impact of physician ownership of outpatient surgery centers, the majority of operating rooms where outpatient surgery is performed are owned and operated by hospitals or health systems.

Regardless of financial incentive, it is the obligation of the surgeon to prioritize patient safety and choose the most appropriate surgical setting for each procedure performed.

Surgeons must rigorously assess a patient’s eligibility for outpatient surgery, as pre-existing conditions may put patients at a higher risk for complications. In a recent retrospective review of 1449 patients undergoing outpatient cervical and lumbar decompression procedures, Helseth et al. suggested that low comorbidity, patient age less than 70 years, and single-level pathology should be criteria for outpatient spine procedure candidates.8 However, further research is necessary to identify optimal candidates for outpatient spine procedures.

Patients considering outpatient surgery would benefit from employing due diligence to ensure they are being treated at a center that is compliant with safety standards.

Furthermore, patients should be Vertebral Columns • Spring 2018

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encouraged to communicate any concerns to their surgeon, and to share information regarding medical conditions they may have or medications that they are taking.

A proficient surgeon that employs responsible patient selection can perform many surgical procedures safely in an outpatient center, while favorably reducing costs to society as a whole. Excellent outcomes and high patient satisfaction, combined with lower costs indicates the superior healthcare value with outpatient surgery that many patients with spinal or other musculoskeletal pathology are safe to experience.

References

1. Services MPACUSDOHAH. Medicare Payment Advisory Commission report to the Congress, March 2010. J Pain Palliat Care Pharmacother 2010;24:302-5.

2. Jewett C, Alesia M. How a push to cut costs and boost profits at surgery centers led to a trail of death. USA Today, 218.

3. McClelland S, 3rd, Oren JH, Protopsaltis TS, et al. Outpatient anterior cervical discectomy and fusion: A meta-analysis. J Clin Neurosci 2016;34:166-8.

4. Mathis MR, Naughton NN, Shanks AM, et al. Patient selection for day case-eligible surgery: identifying those at high risk for major complications. Anesthesiology 2013;119:131021.

5. Warner MA, Shields SE, Chute CG. Major morbidity and mortality within 1 month of ambulatory surgery and anesthesia. JAMA 1993;270:1437-41.

6. Keyes GR, Singer R, Iverson RE, et al.

Analysis of outpatient surgery center safety using an internet-based quality improvement and peer review program. Plast Reconstr Surg 2004;113:1760-70.

7. Engbaek J, Bartholdy J, Hjortsø NC. Return hospital visits and morbidity within 60 days after day surgery: a retrospective study of 18,736 day surgical procedures. Acta Anaesthesiol Scand 2006;50:911-9.

8. Helseth Ø, Lied B, Halvorsen CM, et al.

Outpatient Cervical and Lumbar Spine Surgery is Feasible and Safe: A Consecutive Single Center Series of 1449 Patients. Neurosurgery 2015.

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COMPLICATIONS

Reduction of Intraoperative Blood Loss in Spine Surgery procedures, TXA can have major adverse reactions, though review of TXA use in orthopedic procedures Introduction demonstrates safety with little risk Intraoperative blood loss in spine of serious complications.6,7 Addisurgery is a serious surgical dilemtionally, rotational thromboelastoma as blood loss itself is dangerous metry (ROTEM) is used preoperand the risks involved in blood atively and also intraoperatively, transfusion include infection, to determines the specific factor anaphylaxis, transfusion-related deficiencies patients develop during acute lung injury (TRALI) and the procedure. With ROTEM, pafluid shifts causing decompensatient coagulopathy can be isolated tion. In the case of more intensive and treated accordingly.8 multi-level or revision procedures, As spine procedures particularly, transfusions are inevitable, porare associated with high amounts tending further complications. of blood loss, specific surgical More recently, alternatives to intechniques to help combat this traoperative transfusions have been have been implemented. Minimalput forth and newer technologies ly invasive techniques have been have come about to help decrease brought about to conserve blood, as the need for patient exposure to for- these techniques generally decrease eign blood products. The purpose the surgical trauma and operative of this review is to comment on the time, thereby reducing blood loss methods of decreasing intraoperaand the need for transfusion. One tive blood loss during spine surgery, such example is the minimally which ultimately decrease transfuinvasive transforamenal lumbar sion rates in patients.1-3 interbody fusion (TLIF) compared to an open posterolateral fusion apIntraoperative Techniques proach, where a decrease in blood In addition to treating patients with loss was seen in the minimally Tranexamic Acid (TXA) preopinvasive technique.9 Another sureratively, various studies establish gical technique includes temporary benefit in using TXA intraoperaclosure of the open sites in which tively as it reduces blood loss and the surgeon is not directly working. patients suffer less complications Patient positioning is important 4,5 postoperatively. A maintenance as varying positions affect intraabdose of 1mg/kg/hour appears to dominal pressure (IAP). A high have adequate hemostatic effects.

IAP can put pressure on the inferior In longer, more intensive procedure vena cava and the venous system, however, surgeons can opt for a causing leakage of blood through higher loading dose or maintenance surrounding, pressurized tissues. dose to ensure proper hemostaTo decrease the IAP, a Jackson sis.5 Notably, in non-orthopedic table is utilized during posterior Rabia Qureshi & Hamid Hassanzadeh

approach surgeries.10,11 Newer technologies have been used recently to decrease intraoperative blood loss including bipolar sealing systems and ultrasonic bone cutting devices. Bone cutting devices, used in osteotomies, function to cut bone while leaving the surrounding tissue intact. With the use of a bone cutter, operative times and surrounding tissue damage are decreased, significantly lessening blood loss intraoperatively. Specifically, the ultrasonic bone cutters amplify electrical current and create high frequency oscillations which aid in the cutting of bone with less adjacent tissue damage.

Concomitantly, the cut surfaces of bone are “sealed�, decreasing bony bleeding that may occur.12,13 Bipolar sealing systems, another new innovation to decrease blood loss, target surrounding bone and soft tissue during surgery and work to occlude vessels by delivering controlled thermal energy.14 With the use of the bipolar sealing system, Mankin et al displayed a 57% decrease in blood loss during spine surgery.15 Further analysis of other orthopedic procedures employing sealing devices also revealed a general decrease in blood loss, though no effects on postoperative complications were noted.16 Other methods of decreasing intraoperative blood loss include cell savers, hemodilution and temperature/pressure regulation.

Cell savers, which filter shed blood and return the autologous blood to the patient and can decrease the Vertebral Columns • Spring 2018

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need for allogenic blood transfusion (and associated high costs), especially in patients who refuse allogenic blood products.17,18 Another method of decreasing blood loss is acute normovolemic hemodilution (ANH), which is an intraoperative technique to collect autologous blood, replacing it with an isotonic crystalloid solution. Decreases in the necessity for transfusion were noted in some studies of spine procedures, which may be due to the induction of a mildly hypercoagulable state from the ANH, though further study should be conducted to confirm.1,19 Temperature and pressure are factors affecting intraoperative blood loss as platelet function is impaired by hypothermia, increasing blood loss at lower temperatures. Patients should be actively warmed to a core temperature of at least 36.6 C.20 In addition to temperature regulation, compartmental pressure regulation should be implemented. Along with the decrease in IAP, high vertebral intraosseous pressures indicate bleeding through bony and venous structures. By controlling the compartment pressures, localized bleeding can be decreased.21 Systemic hypotension however, is dangerous and should not be used to control bleeding in spine surgery as blindness can result.22 Conclusion Many complications can result from excessive blood loss in spine surgery. Transfusion, similarly, poses risk of complications such as systemic infections, cardiac or renal decompensation and anaphylaxis.

Due to these adverse outcomes, many intraoperative methods have been applied to prevent or decrease blood loss including antifibrinolytics, temperature and pressure regulation, hemodilution, cell savers and the use of newer technologies 6

Vertebral Columns • Spring 2018

such as bipolar sealing devices and ultrasonic bone cutters. With these techniques, intraoperative blood loss is greatly minimized, reducing the blood loss related complications patients may suffer from postoperatively and improving overall outcomes, even in high-risk patients.

References

1. Theusinger OM, Spahn DR. Perioperative blood conservation strategies for major spine surgery. Best Practice & Research Clinical Anaesthesiology. 2016;30(1):41-52.

2. Spahn DR, Goodnough LT. Alternatives to blood transfusion. The Lancet.381(9880):1855-1865.

3. Hu SS. Blood loss in adult spinal surgery.

European Spine Journal. 2004;13(1):S3-S5.

4. Yagi M, Hasegawa J, Nagoshi N, et al. Does the intraoperative tranexamic acid decrease operative blood loss during posterior spinal fusion for treatment of adolescent idiopathic scoliosis?

Spine. 2012;37(21):E1336-E1342.

5. Winter SF, Santaguida C, Wong J, Fehlings MG. Systemic and Topical Use of Tranexamic Acid in Spinal Surgery: A Systematic Review.

Global Spine J. 2016;06(03):284-295.

6. Eubanks JD. Antifibrinolytics in Major Orthopaedic Surgery. Journal of the American Academy of Orthopaedic Surgeons.

2010;18(3):132.

7. Ho K, Ismail H. Use of intravenous tranexamic acid to reduce allogeneic blood transfusion in total hip and knee arthroplasty: a meta-analysis. Anaesthesia and intensive care.

2003;31(5):529.

8. Naik BI, Pajewski TN, Bogdonoff DI, et al. Rotational thromboelastometry–guided blood product management in major spine surgery. Journal of Neurosurgery: Spine.

2015;23(2):239-249.

9. Patel AA, Zfass-Mendez M, Lebwohl NH, et al. Minimally Invasive Versus Open Lumbar Fusion: A Comparison of Blood Loss, Surgical Complications, and Hospital Course. The Iowa Orthopaedic Journal. 2015;35:130-134.

10. Han IH, Son DW, Nam KH, Choi BK, Song GS. The effect of body mass index on intra-abdominal pressure and blood loss in lumbar spine surgery. Journal of Korean Neurosurgical Society. 2012;51(2):81-85.

11. Lee TC, Yang LC, Chen HJ. Effect of patient position and hypotensive anesthesia on inferior vena caval pressure. Spine.

1998;23(8):941-947.

12. Bartley CE, Bastrom TP, Newton PO. Blood loss reduction during surgical correction of adolescent idiopathic scoliosis utilizing an ultrasonic bone scalpel. Spine Deformity.

2014;2(4):285-290.

13. Hu X, Ohnmeiss DD, Lieberman IH. Use of an ultrasonic osteotome device in spine surgery: experience from the first 128 patients.

European Spine Journal. 2013;22(12):28452849.

14. Marulanda G, Ragland P, Seyler T, Mont M. Reductions in blood loss with use of a bipo-

lar sealer for hemostasis in primary total knee arthroplasty. Surgical technology international.

2004;14:281-286.

15. Mankin KP, Moore CA, Miller LE, Block JE. Hemostasis with a bipolar sealer during surgical correction of adolescent idiopathic scoliosis. Journal of spinal disorders & techniques.

2012;25(5):259-263.

16. Min J-K, Zhang Q-H, Li H-D, Li H, Guo P. The Efficacy of Bipolar Sealer on Blood Loss in Primary Total Hip Arthroplasty: A Meta-Analysis. Medicine. 2016;95(19):e3435.

17. Carless PA, Henry DA, Moxey AJ, O’Connell D, Brown T, Fergusson DA. Cell salvage for minimising perioperative allogeneic blood transfusion. The Cochrane database of systematic reviews U6 - ctx_ver=Z39.88-2004&ctx_ enc=info%3Aofi%2Fenc%3AUTF-8&rfr_id=info%3Asid%2Fsummon.serialssolutions. com&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft. atitle=Cell+salvage+for+minimising+perioperative+allogeneic+blood+transfusion&rft.jtitle=The+Cochrane+database+of+systematic+reviews&rft. au=Carless%2C+Paul+A&rft.au=Henry%2C+David+A&rft.au=Moxey%2C+Annette+J&rft.au=O%27Connell%2C+Dianne&rft. date=2010&rft.eissn=1469-493X&rft. issue=4&rft.spage=CD001888&rft_id=info%3Apmid%2F20393932&rft.externalDocID=20393932&paramdict=en-US U7 - Journal Article. 2010(4):CD001888.

18. Esper SA, Waters JH. Intra-operative cell salvage: a fresh look at the indications and contraindications. Blood Transfus. 2011;9(2):139147.

19. Epstein NE, Peller A, Korsh J, et al. Impact of intraoperative normovolemic hemodilution on transfusion requirements for 68 patients undergoing lumbar laminectomies with instrumented posterolateral fusion. Spine.

2006;31(19):2227-2230.

20. Schmied H, Reiter A, Kurz A, Sessler DI, Kozek S. Mild hypothermia increases blood loss and transfusion requirements during total hip arthroplasty. The Lancet. 1996;347(8997):289292.

21. Menovsky T, De Ridder D. Simple intraoperative technique for hemostasis of cervical venous bleeding. Neurosurgery. 2008;62(5 Suppl 2):ONS442-ONS444.

22. Lee LA, Roth S, Posner KL, et al. The American Society of Anesthesiologists Postoperative Visual Loss RegistryAnalysis of 93 Spine Surgery Cases with Postoperative Visual Loss. The Journal of the American Society of Anesthesiologists. 2006;105(4):652-659.

NEW TECHNOLOGIES

A Single-Use, Disposable Implant System for Thoracolumbar Fixation Surgery by Innovative Surgical Designs D. Greg Anderson, MD; Kristen Radcliff, MD and Saad Chaudhary, MD, MBA Surgical management of thoracolumbar disease has become common place in the modern healthcare environment.1 In recent years, healthcare systems have increasingly shifted their focus towards increased efficiency in the delivery of healthcare services as reimbursements for surgical and inpatient services has declined.3 Implants charges are a major cost-driver for thoracolumbar fusion surgery.3 Time efficiency in the operating room also has a major effect on operational costs as time in the operating room has been shown to be at least $51.70 per minute.5 Surgical site infection has been shown to double the healthcare cost following spinal surgery.4 The medical device industry has been tasked with the challenge of helping healthcare systems address these cost-drivers by creating products that enhance efficiency in the delivery of healthcare services.

Innovative Surgical Designs (ISD), Bloomington, IN has recently introduced the True™ Spinal Fixation system. This pedicle screw-based thoracolumbar fixation system seeks to address the challenges of the modern healthcare environment by 1) preloading each pedicle screw implant on a drive system and providing them individually sterile packaged so that no back ta-

ble assembly is required and 2) utilizing a single-use disposable pack with all the necessary intruments for pedicle screw placement thereby reducing the overall implant and instrument footprint, (Figure 1). CEO, Mark Bartosh says, “One key to the True™ system is how it packs so much functionality into the implants, reducing the need for multiple instruments that might be required with a traditional spinal fixation system.”

Figure 2: 6mm extension tab on the True™ implant guides the placement of instruments during either minimally invasive or open surgical technique.

Figure 1: Instrument kit for a True™ spinal fixation case.

The True™ system also incorporates a unique rod with circular bushings on each end. The rod is shaped to reduce stiffness in the flexion-extension plane while maintaining high stiffness and resistance to lateral bending and axial rotation of the fused segment.

Rods are placed segmentally from screw to screw, allowing the system to be self-contouring (Figures 2 and 3). Both MIS and open procedures can be performed using the same system, due to a thin, 6mm extension tab on each of the pedicle screw implants (Figure 2). The instruments are manufactured from a strong plastic and incorporate metal

tips to ensure precise interaction with the implants (Figure 1). Final tightening of the system is achieved through a break away system (Figure 3).

Due to the disposable nature of the spinal instruments, preparation for a thoracolumbar fusion case is much quicker and more reliVertebral Columns • Spring 2018

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able compared to the opening of multiple wrapped spinal implant and instrument trays. In addition, product sterility is ensured by a validated process of gamma sterilization instead of a variable “in house” process of cleaning, sterilizing and wrapping the instruments for each case. The instruments are Figure 3: Two-level construct using the True™ Spinal Fixation system.

single-use, so sharpness and function is ensured. Back table set up for a case is minimal as each of the implants is provided on the drive system, ready for implantation.

Surgical technique for the True™ system is similar to other systems although many surgeons find the work flow to be streamlined by the simplicity of the surgical instru-

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ments.

Institutional cost savings with the True™ system is achievable due to savings in operating room time and the lack of personnel time required to clean, re-sterilize and repackage instruments between cases. Additionally, there is a potential benefit of reduced surgical site infections with single-use sterile product.

There is decreased risk of instrument contamination and the implants do not sit on the back table for significant periods of time prior to being used.

In summary, the True™ Spinal Fixation System by Innovative Surgical Designs has several potential advantages over a traditional pedicle screw system. True™ instruments and implants are provided in small sterile pouches that require minimal footprint. The instruments and the implants can be opened when they are needed during the surgery. These differences allow for increased OR efficiency, decreased work by the staff managing trays and theoretically decreased infection rate. Additionally, the True™ system eliminates the need for resterilization, as it is a single-use disposable system, further decreasing cost and infection risk. The unique design of the rod allows for strong segmental correction and

simplifies adjacent segment instrumentation in revision cases. One disadvantage of the rod design is the decreased strength in rotation relative to traditional pedicle screw systems. However, ISD is currently adapting the True™ system to be compatible with a 5.5mm round rod.

References

1. Rajaee SS, Bae HW, Kanim LE, Delamarter RB. Spinal fusion in the United States: analysis of trends from 1998 to 2008. Spine (Phila Pa 1976). 2012 Jan 1;37(1):67-76.

2. Litrico S, Recanati G, Gennari A, Maillot C, Saffarini M, Le Huec JC. Single-use instrumentation in posterior lumbar fusion could decrease incidence of surgical site infection: a prospective bi-centric study. Eur J Orthop Surg Traumatol. 2016 Jan;26(1):21-6.

3. Robinson JC, Brown TT. Quantifying opportunities for hospital cost control: medical device purchasing and patient discharge planning. Am J Manag Care. 2014 Sep 1;20(9):e418-24.

4. Patel H, Khoury H, Girgenti D, Welner S, Yu H. Burden of Surgical Site Infections Associated with Select Spine Operations and Involvement of Staphylococcus aureus. Surg Infect (Larchmt). 2016 Nov 30.

5. Gabriel A, Maxwell GP, Griffin L, Champaneria MC, Parekh M, Macarios D. A Comparison of Two Fat Grafting Methods on Operating Room Efficiency and Costs.

Aesthet Surg J. 2017 Feb;37(2):161-168.

REVIEW

Expandable Cages: A Review Elizabeth Yu, MD and Safdar N. Khan, MD

or reconstruction with an expandable cage for vertebral body tumors.

Background They concluded their complication Expandable cages have been derates were similar to what was scribed in the literature since the already described for anterior alone mid-2000s. Use of expandable or combined anterior and posterior cages in the spine have grown in spinal approaches.5 popularity with various clinical Approaches for placement of applications. Static cages, strucexpandable cages include anterior, tural autograft/allograft, or polylateral and posterior approaches. methylmethacrylate placed from Anterior approaches range from a posterior approach pose chalthoracotomies to retroperitoneal lenges when filling a large defect or transperitoneal approaches. through a smaller working window. Posterior approaches can include This is encountered often with a the lateral extracavitary approach, posterior approach, whether it is transpedicular approach or the for an interbody fusion or a vertecostotransversectomy approach. brectomy in the thoracic or lumbar Variability of complexity depends spine for conditions ranging from on the location of the pathology, to degenerative disease to metastatic include cervical, thoracic or lumbar disease and infection to unstable spine. Each approach is not withfractures. Structural autograft risks out their own morbidities. complications at the donor site.

The benefits of an expandable cage Polymethylmethacrylate places risk allows one to avoid the anterior of thermal injury or extravasation at approach in the more difficult to the surgical site. access regions, such as the upper thoracic spine. When collapsed, Vertebrectomy or Corpectomy the expandable cage also decreases Expandable cages were originally the need for sacrificing nerve roots described for filling corpectomy posteriorly that are in the field with defects via the anterior approach.1-3 a static cage.6 In 2003, Thongtrangan et al reCervical expandable cages were ported a retrospective chart review described in the early 2000s as reporting their clinical experience well. Elder et al in 2016 performed with the use of expandable cages a systematic review of expandable via the anterior approach for vercages used in the cervical spine for tebral body tumors.2 Several years corpectomy. A majority of the relater, case reports and case series views were case series or retrospecemerged describing the benefits of tive studies. The most common an all-posterior approach for an an- uses were for degenerative disease, terior and posterior reconstruction trauma, infection, tumor, deformity of the spine secondary to metastatic and ossification of the posterior tumors.4-6 Shen et al described the longitudinal ligament. The most largest multicenter series in 2008 of common complication was subsid21 patients who underwent posteri- ence. The authors did not identify

any study assessing the improvement or maintenance of lordosis with an expandable cage versus a static cage.7 Burkett et al reviewed their patient experience with expandable cages for cervical disease, to include spondylosis, fracture, ligamentous injury, osteomyelitis, deformity, tumor and revision surgery. The authors concluded the expandable cages deployed are safe and effective constructs without significantly increased hardware complication risks.8 Expandable cages also have the ability to be modular. This allows for customizable lordosis versus kyphosis versus parallel implants of the endcaps. Eleraky et al compared expandable and static cages in the setting of thoracolumbar spine fractures. They assessed the angular correction, with noted improvement of the expandable cages in postoperative follow up.9 Sciuba and Sasani et al noted reduction in thoracic hyperkyphosis with expandable cage in thoracolumbar fractures or other thoracic reconstruction.10, 11 Zairi et al followed patients with cervical myelopathy and assessed their outcomes with use of an expandable cage. They reported 2 degrees of improvement of kyphosis angle compared to preoperative measurements. This was maintained at latest follow up.12 Lange et al performed a prospective study on patients with traumatic fractures of the thoracolumbar spine. Approach was anterior or posterior for the corpectomy and expandable cage placement. At latest follow up, the authors reported minimal loss of correction.3 Vertebral Columns • Spring 2018

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Various cadaveric biomechanical studies have been performed. They include studies to assess risks of endplate fractures, stiffness of construct as well as comparison to other implants. In the cervical spine, Kandziora et al performed a cadaveric biomechanical study assessing the stiffness of a tricortical iliac crest bone graft, static cage, and expandable cage with and without anterior plating and posterior screws and rods. They concluded stand-alone device is not recommended.1 Elerasky et al evaluated PMMA versus expandable cage in the setting of metastatic disease.

They reported a trend toward correction of kyphotic deformity with the expandable cage.13 Pflugmacher et al performed a cadaveric biomechanical study assessing stiffness when an anterior L1 corpectomy was performed with expandable or static cage with and without anterior plating. Posterior supplemental fixation was then applied. The authors concluded that anterior plating with cage does not provide adequate stability and requires additional supplemental posterior fixation. Static and expandable cages provided the same amount of motion in all directions.14 Footprint size of the endcaps are also variable. Mundis et al performed a cadaveric biomechanical study that compared round versus rectangular shaped endcaps with anterior plate versus posterior pedicle screw placement in the setting of an L1 corpectomy. The authors concluded reduction of motion with flexion and extension for both endcaps, but decreased lateral bending with rectangular endcaps.

Either supplemental fixation with plate or pedicle screws provided increased stiffness of the construct.15 Because of the smaller size when the cage implant is collapsed, a 10

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minimally invasive approach can be applied with a smaller surgical incision. A thorascopic approach has been described in the early development of expandable cages. Ragel et al describes his surgical technique for an L1 corpectomy with placement of an expandable cage and lateral plate. This was performed through 4 smaller incisions.16 Interbody fusion Expandable interbody cages differ from corpectomy expandable cages.

Differences range from material composition to how the implant expands. Many expandable cages are composed of titanium. Alimi et al reported their series of patients that underwent transforaminal lumbar interbody fusions with expandable polyetheretherketone cages. They retrospectively reviewed 49 patients who underwent the described procedure. Average follow up was 19 months. The authors followed the visual analog scale, oswestry disability index, disc and foraminal height, listhesis reduction and subsidence. They reported that there was improvement of ODI, VAS as well as disk and foraminal height.

There was reduction of listhesis.

Overall, the authors concluded the PEEK stack cage provided early reasonable results.17 New technology; however, is not without complications. Stein et al presented a case report of a patient that underwent a 2 level transforaminal lumbar interbody fusion with a polyetheretherketone PEEK expandable cage. The cage expanded via insertion of PEEK wafers. This was complicated by retropulsion of one of the wafers of the implant, resulting in lumbar radiculopathy. The patient required revision surgery.18 A similar case report was reported prior to this case report.19

Corpectomy cages typically expand cephalad and caudad. Newer cages are emerging that expand medial to lateral in the interbody cages.

Cannestra et al recently compared various expandable transforaminal lumbar interbody (TLIF) cages via a cadaveric biomechanical study.

Expansion of the cage included cephalad-caudad expansion or medial-lateral expansion. Pedicle screws were placed unilaterally or bilaterally. The range of motion was then assessed and compared to a prior anterior lumbar interbody cage (ALIF) placement with anterior plate. The authors found the medial-lateral expansion cage with unilateral pedicle screws was comparable with ALIF with anterior plate and TLIF with bilateral pedicle screws. They concluded that a larger footprint cage may decrease the need for supplemental fixation.20 Various biomechanical studies are available evaluating expandable cages.[21-23] Pekmezci et al performed a cadaveric biomechanical study assessing expandable and fixed interbody cages. They assessed stiffness and noted despite a larger footprint, expandable cages trended toward higher subsidence rate. With increased edge loading, such as hyperlordotic cage, there is an even greater risk of subsidence.

[24] Mantell et al performed a cadaveric biomechanical study assessing the motion with an expandable lateral interbody cage and static transforaminal lumbar interbody cage with or without pedicle screws in a lumbar spondylolisthesis model. The authors reported the expandable lateral interbody cage with unilateral pedicle screws were equivalent to a static transforaminal lumbar interbody cage with bilateral pedicle screws.25

Similar to expandable cages for vertebral body reconstruction, in the interbody fusion technique, the small size of the collapsed implant lends itself to a minimally invasive approach with a smaller surgical incision and less trauma to the surrounding tissues. Kim et al retrospectively analyzed their patient data with patients who underwent a minimally invasive transforaminal lumbar interbody fusion with an expandable cage. They reported improvement in disc height restoration and high fusion rates. There was no subsidence, collapse or cage migration at 2 year follow up.26 Coe et al described their experience with a PEEK implant that expanded cephalad and caudad for a posterior lumbar interbody fusion through a minimally invasive approach.27 Complications Expandable cages are not without complication issues. Bone fusion is a concern. This includes difficulty with placement of bone graft extenders within the cage portion that is expanded in situ. The large footprint also decreases the surface area for bone fusion. Park et al; however, retrospectively reviewed 34 patients treated in their institution who underwent a stand alone single level posterior lumbar interbody fusion with expandable cage. They used imaging to include dynamic radiographs and computer tomography to assess bone fusion.

30 of 34 patients were noted to have bone bridge on CT. The authors concluded stand alone expandable cages may provide satisfactory clinical outcomes.28 Endplate fractures have been described in the literature. This may occur early or late. Early subsidence has been described. Payer et al reported appropriate preparations of the endplates

are imperative to decrease the risk of subsidence.29 Bone mineral density also affects subsidence risks.30 A larger endplate footprint decreases subsidence risk.31 Recently described angular mismatch of the endcaps may affect subsidence risks.32 Late endplate violation, or adjacent segment vertebral body fractures, have been described.

There is a risk of over distraction as well as undersizing of the cage.

Over distracting the cage risks endplate violation or potentially distracting the spinal cord when in the thoracic or cervical level.17,33-35 Pekmezci et al performed a cadaveric biomechanical study comparing expandable and fixed cages in a single level corpectomy model of the thoracolumbar spine. They reported expandable cages had higher contact area and endplate forces compared to the fixed cages.

They also reported the expansion torque did not correlate with the forces on the endplate, suggesting tactile feedback may not allow for prevention of endplate injury.36 Undersizing the cage can result in graft extrusion.

Expandable cages are traditionally more expensive. There is no literature available assessing the cost effectiveness of expandable cages in complex spine cases at this time.

Conclusion Expandable cages allow for the circumferential approach to the spine via one approach. They allow a large defect to be filled, which was once a challenge with the use of static devices. They also allow for the use of smaller incisions in the setting of minimal invasive spine surgery.

Judicious use of these devices is important. Their outcomes are comparable to those of static cages.

References

1. Kandziora, F., et al., Biomechanical comparison of expandable cages for vertebral body replacement in the cervical spine. J Neurosurg, 2003. 99(1 Suppl): p. 91-7.

2. Thongtrangan, I., et al., Vertebral body replacement with an expandable cage for reconstruction after spinal tumor resection.

Neurosurg Focus, 2003. 15(5): p. E8.

3. Lange, U., et al., Anterior vertebral body replacement with a titanium implant of adjustable height: a prospective clinical study. Eur Spine J, 2007. 16(2): p. 161-72.

4. Hunt, T., F.H. Shen, and V. Arlet, Expandable cage placement via a posterolateral approach in lumbar spine reconstructions.

Technical note. J Neurosurg Spine, 2006. 5(3): p. 271-4.

5. Shen, F.H., et al., The use of an expandable cage for corpectomy reconstruction of vertebral body tumors through a posterior extracavitary approach: a multicenter consecutive case series of prospectively followed patients. Spine J, 2008. 8(2): p. 329-39.

6. Jandial, R., B. Kelly, and M.Y. Chen, Posterior-only approach for lumbar vertebral column resection and expandable cage reconstruction for spinal metastases. J Neurosurg Spine, 2013.

19(1): p. 27-33.

7. Elder, B.D., et al., A systematic review of the use of expandable cages in the cervical spine.

Neurosurg Rev, 2016. 39(1): p. 1-11; discussion 11.

8. Burkett, C.J., et al., Use of titanium expandable vertebral cages in cervical corpectomy. J Clin Neurosci, 2012. 19(3): p. 402-5.

9. Eleraky, M.A., et al., Expandable versus nonexpandable cages for thoracolumbar burst fracture. World Neurosurg, 2011. 75(1): p.

149-54.

10. Sciubba, D.M., et al., Thoracic kyphotic deformity reduction with a distractible titanium cage via an entirely posterior approach.

Neurosurgery, 2007. 60(4 Suppl 2): p. 223-30; discussion 230-1.

11. Sasani, M. and A.F. Ozer, Single-stage posterior corpectomy and expandable cage placement for treatment of thoracic or lumbar burst fractures. Spine (Phila Pa 1976), 2009.

34(1): p. E33-40.

12. Zairi, F., et al., Relevance of expandable titanium cage for the treatment of cervical spondylotic myelopathy. Eur Spine J, 2012.

21(8): p. 1545-50.

13. Eleraky, M., et al., Comparison of polymethylmethacrylate versus expandable cage in anterior vertebral column reconstruction after posterior extracavitary corpectomy in lumbar and thoraco-lumbar metastatic spine tumors.

Eur Spine J, 2011. 20(8): p. 1363-70.

14. Pflugmacher, R., et al., Biomechanical comparison of expandable cages for vertebral body replacement in the thoracolumbar spine. Spine (Phila Pa 1976), 2004. 29(13): p. 1413-9.

15. Mundis, G.M., et al., Contribution of Round vs. Rectangular Expandable Cage Endcaps to Spinal Stability in a Cadaveric Corpectomy Model. Int J Spine Surg, 2015. 9: p. 53.

16. Ragel, B.T., A. Amini, and M.H. Schmidt, Thoracoscopic vertebral body replacement with an expandable cage after ventral spinal canal de-

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compression. Neurosurgery, 2007. 61(5 Suppl 2): p. 317-22; discussion 322-3.

17. Alimi, M., et al., Expandable PolyarylEther-Ether-Ketone Spacers for Interbody Distraction in the Lumbar Spine. Global Spine J, 2015. 5(3): p. 169-78.

18. Stein, I.C., et al., Failure of a polyether-ether-ketone expandable interbody cage following transforaminal lumbar interbody fusion. Eur Spine J, 2015. 24 Suppl 4: p. S555-9.

19. Kim, P.D., E.M. Baron, and M. Levesque, Extrusion of expandable stacked interbody device for lumbar fusion: case report of a complication. Spine (Phila Pa 1976), 2012. 37(18): p. E1155-8.

20. Cannestra, A.F., et al., MIS Expandable Interbody Spacers: A Literature Review and Biomechanical Comparison of an Expandable MIS TLIF With Conventional TLIF and ALIF. Spine (Phila Pa 1976), 2016. 41 Suppl 8: p.

S44-9.

21. Gonzalez-Blohm, S.A., et al., Biomechanical analysis of an interspinous fusion device as a stand-alone and as supplemental fixation to posterior expandable interbody cages in the lumbar spine. J Neurosurg Spine, 2014. 20(2): p. 209-19.

22. Gonzalez-Blohm, S.A., et al., In vitro evaluation of a lateral expandable cage and its comparison with a static device for lumbar interbody fusion: a biomechanical investigation.

J Neurosurg Spine, 2014. 20(4): p. 387-95.

23. Bhatia, N.N., et al., Biomechanical evaluation of an expandable cage in single-segment posterior lumbar interbody fusion. Spine (Phila Pa 1976), 2012. 37(2): p. E79-85.

24. Pekmezci, M., et al., Comparison of Expandable and Fixed Interbody Cages in a Human Cadaver Corpectomy Model: Fatigue Characteristics. Clin Spine Surg, 2016. 29(9): p. 387-393.

25. Mantell, M., et al., Biomechanical analysis of an expandable lateral cage and a static transforaminal lumbar interbody fusion cage with posterior instrumentation in an in vitro spondylolisthesis model. J Neurosurg Spine, 2016. 24(1): p. 32-8.

26. Kim, C.W., et al., Minimally Invasive Transforaminal Lumbar Interbody Fusion Using Expandable Technology: A Clinical and Radiographic Analysis of 50 Patients. World Neurosurg, 2016. 90: p. 228-35.

27. Coe, J.D., et al., Multiexpandable cage for minimally invasive posterior lumbar interbody fusion. Med Devices (Auckl), 2016. 9: p. 341347.

28. Park, J.H., et al., Clinical and radiological outcomes of unilateral facetectomy and interbody fusion using expandable cages for lumbosacral foraminal stenosis. J Korean Neurosurg Soc, 2010. 48(6): p. 496-500.

29. Payer, M., Implantation of a distractible titanium cage after cervical corpectomy: technical experience in 20 consecutive cases. Acta Neurochir (Wien), 2006. 148(11): p. 1173-80; discussion 1180.

30. Jost, B., et al., Compressive strength of interbody cages in the lumbar spine: the effect of cage shape, posterior instrumentation and bone density. Eur Spine J, 1998. 7(2): p. 132-41.

31. Hasegawa, K., et al., An experimental study on the interface strength between titanium

12

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mesh cage and vertebra in reference to vertebral bone mineral density. Spine (Phila Pa 1976), 2001. 26(8): p. 957-63.

32. Mohammad-Shahi, M.H., et al., The effect of angular mismatch between vertebral endplate and vertebral body replacement endplate on implant subsidence. J Spinal Disord Tech, 2013.

26(5): p. 268-73.

33. Karikari, I.O., et al., Minimally invasive lumbar interbody fusion in patients older than 70 years of age: analysis of peri- and postoperative complications. Neurosurgery, 2011. 68(4): p. 897-902; discussion 902.

34. Kim, M.C., et al., Subsidence of polyetheretherketone cage after minimally invasive transforaminal lumbar interbody fusion. J Spinal Disord Tech, 2013. 26(2): p. 87-92.

35. Lam, F.C., R. Alkalay, and M.W. Groff, The effects of design and positioning of carbon fiber lumbar interbody cages and their subsidence in vertebral bodies. J Spinal Disord Tech, 2012.

25(2): p. 116-22.

36. Pekmezci, M., et al., Comparison of expandable and fixed interbody cages in a human cadaver corpectomy model, part I: endplate force characteristics. J Neurosurg Spine, 2012.

17(4): p. 321-6.

IMPROVEMENT

Thoracic Myelopathy - You Find What You Look For Introduction Idiopathic spinal cord herniation and dorsal intradural arachnoid cysts are uncommon causes of thoracic myelopathy.1 Their presentation can vary from back pain to spastic paraparesis with bowel and bladder dysfunction.2 The clinical presentation and radiological appearance is inconsistent and commonly confused, leading to a delayed or misdiagnosis.3 In this clinical highlight, we describe two cases detailing the radiological and anatomic differences between these entities that hopefully provides a clearer understanding and awareness of these distinct ‘not to be missed’ pathologies.

Case 1 A 70-year old male presented with a one-year history of ataxia and recent urinary urgency and occasional incontinence. On physical examination he had 5/5 strength and normal sensation but spasticity with exaggerated lower limbs reflexes. Magnetic resonance imaging (MRI) showed a T6 ventral cord herniation through a dural defect with enlargement of the dorsal thoracic subarachnoid space. (Fig.1) The computed tomography (CT) myelogram confirmed the diagnosis and ruled out an arachnoid cyst by the absence of altered dorsal CSF flow or arachnoid webbing. Erosion of the posterior vertebral wall was present due to the chronic effect of CSF pulsations.

Due to the patient’s progressive

symptoms, surgery was offered and he underwent a T6 laminectomy, intradural exploration and repair of the ventral dural defect. Intraoperatively, ultrasound was used after the laminectomy to confirm that the exposure was adequate to address the spinal cord herniation. A midline durotomy was performed and with gentle elevation of the dentate ligament, the herniated portion of ventral spinal cord was visible as was the dural defect. The posterior vertebral body wall erosion seen on preoperative imaging was also evident. (Fig. 2) The herniated spinal cord was gently elevated back into the intradural space and a small piece of dural substitute (Durepair, Medtronic, Minneapolis, MN) was then placed intradurally covering the dural defect. (Fig. 2) The dorsal durotomy was then closed using a running 5-0 Gore-Tex suture (Gore Medical, Flagstaff, AZ). The wound was closed in layers. He was ambulatory on postoperative day one and was discharged on postoperative day 2. At follow-up he had substantial improvement of his preoperative symptoms with normalization of urinary function and steady gait.

Case 2 A 40-year old man presented with acute onset upper thoracic pain and a ‘lightning’ sensation running down the back and legs while lifting heavy boxes at work. Subsequently he complained of bilateral lower extremity cramping, tightness and gait imbalance. On examination

he had normal motor function and sensation with a spastic gait and exaggerated deep tendon reflexes.

MRI (Fig. 3) revealed a ventrally displaced and compressed spinal cord at T3-4 with dorsal scalloping of the cord and T2 weighted intramedullary signal change present.

A CSF flow anomaly dorsal to the cord could be seen at this level possibly consistent with an arachnid cyst. The patient underwent a T3-4 laminectomy and complete excision of the dorsal intradural arachnoid cyst. Intraoperative ultrasound after the laminectomy (prior to dural opening) revealed independent and altered CSF flow in the cyst distinct from the rest of the intradural space. Upon opening the dura, the cyst was immediately visible and consistent with significant scarring of the arachnoid and demarcation separate from the normal arachnoid and spinal cord (Fig. 4).

Using sharp dissection the cyst was removed as a single piece. The ventral dura was examined to ensure there was no spinal cord herniation.

The dura was then closed using a running 5-0 Gore-Tex suture. The wound was closed in layers. He was ambulatory on postoperative day one and was discharged on postoperative day 2. He made an excellent postoperative recovery with resolution of all his symptoms.

Discussion Ventral spinal cord herniation is a relatively rare disease and characterized by herniation of the spinal cord through a ventral dural Vertebral Columns • Spring 2018

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defect.4,5 A vast majority of spinal cord herniations occur either anteriorly or antero-laterally between T2 and T8. Patients typically present with spastic parapaesis, often in the form of Brown-Sequard syndrome.1–3

Figure 1. T2-weighted (A) Sagittal and (B) axial MRI showing a T6 ventral transdural idiopathic spinal cord herniation.

(C) Sagittal and (D) axial CT myelogram highlighting the absence of any CSF flow disruption dorsally and the presence of erosion of the posterior cortex of the vertebral body (arrows).

MRI typically demonstrates ventral kinking of the thoracic cord with obliteration of the anterior CSF space and enlargement of the dorsal subarachnoid space. (Fig.1) Some authors have measured a kink angle (two tangents drawn on the maximally inflected cranial and caudal portions of the spinal cord) and determined that the value of the exterior angle being greater that 32 degrees was highly suggestive of spinal cord herniation.6 Due to the similar appearance of dorsal spinal cord “scalloping” on sagittal MRI, spinal cord herniation and dorsal intradural arachnoid cyst can be easily confused.1,3 Both can present with pain and spastic paraparesis as well as bowel and bladder dysfunction. However, the severity of myelopathy tends to be greater 14

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in patients with spinal cord herniation. Our patient with arachnoid cyst (Case 2) had sudden onset pain followed by progressive spasticity.

It is possible that a valsalva-like maneuver during lifting something heavy may have increased CSF pressure and enlarged what was a previously asymptomatic arachnoid cyst thus resulting in new or worsening spinal cord compression.

Typically, the durations of symptoms is longer in patients with intradural arachnoid cysts compared to spinal cord herniation.6 Another distinguishing characteristic between these two entities is that MRI classically shows an altered CSF flow within the arachnoid cyst that is not present in cases of spinal cord herniation (Fig.3).6,7 The extent of this altered flow depends of whether CSF reaches the subarachnoid space through a narrow or wide opening. Complete elimination of the ventral CSF space at the level of compression is not commonly seen with an arachnoid cyst but is almost universal in cases of spinal cord herniation.8 In addition, gadolinium enhanced images may help differentiate an arachnoid cyst from other neoplastic pathologies.

Awareness of these subtle clinical and radiological differences before surgery can be helpful in making a

Figure 2. (A and B) intraoperative high-resolution photographs showing the herniated spinal cord and the underlying bony erosion. (C and D) Repair of the dural defect with an artificial dural patch after reduction of the herniation. correct diagnosis between ventral spinal cord herniation and a dorsal arachnoid cyst. Surgery is generally reserved for symptomatic cases as there are occasional reports of spontaneous resolution of ventral spinal cord herniations.2,9 Surgical strategies have evolved in the treatment of ventral spinal cord herniations.10 Closure of the dura has been attempted by primarily suturing the dura and/or by placing various artificial dural patches extradurally (Fig. 2). Some authors have described simply widening the dural defect to prevent strangulation of the cord.10 We prefer to simply place a piece of artificial

Figure 3. T2-weighted (A) Sagittal and (B) axial MRI showing a dorsal arachnoid cyst at T3-4 with alteration of the CSF flow at that level (arrow). (C)T1-weighted Gadolinium enhanced sagittal MRI showing no enhancement of the lesion (arrow) ruling out a neoplastic etiology.

12. Kumar A, Sakia R, Singh K, Sharma V. Spinal arachnoid cyst. J Clin Neurosci Off J Neurosurg Soc Australas. 2011;18(9):11891192. doi:10.1016/j.jocn.2010.11.023.

Figure 4. (A) Intraoperative photographs of the cyst as seen during surgery and after complete excision (B). dural replacement intradurally over the dural defect that is fashioned to a size just larger than the defect.

This “patch” acts like a sling preventing the spinal cord from re-herniating through the defect. We have not seen any recurrences using this technique in the last 10 years. In cases of arachnoid cysts, excision is the most definitive treatment (Fig. 4) and where not possible marsupialization works with very low recurrence rates.11,12 Conclusion In the patient presenting with lower extremity sensory, motor or gait changes and possibly bladder dysfunction, thoracic myelopathy should be included in the differential diagnosis. The combination of upper motor neuron signs/symptoms (with or without significant lumbar imaging findings) should prompt the clinician to order a thoracic MRI. The detection of subtle entities such as idiopathic spinal cord herniation and intradural arachnoid cyst requires an awareness of their unique anatomic and radiologic characteristics.

References

1. Darbar A, Krishnamurthy S, Holsapple JW, Hodge CJ. Ventral thoracic spinal cord herniation: frequently misdiagnosed entity.

Spine. 2006;31(17):E600-605. doi:10.1097/01. brs.0000229247.69171.a1.

2. Groen RJM, Middel B, Meilof JF, et al.

Operative treatment of anterior thoracic spinal cord herniation: three new cases and an individual patient data meta-analysis of 126 case reports. Neurosurgery. 2009;64(3 Suppl):ons145-159-160. doi:10.1227/01.

NEU.0000327686.99072.E7.

3. Carter BJ, Griffith BD, Schultz LR, Abdulhak MM, Newman DS, Jain R. Idiopathic spinal cord herniation: an imaging diagnosis with a significant delay. Spine J Off J North Am Spine Soc. 2015;15(9):1943-1948. doi:10.1016/j. spinee.2015.04.013.

4. Summers JC, Balasubramani YV, Chan PCH, Rosenfeld JV. Idiopathic spinal cord herniation: Clinical review and report of three cases. Asian J Neurosurg. 2013;8(2):97-105. doi:10.4103/1793-5482.116386.

5. Berg-Johnsen J, Ilstad E, Kolstad F, Züchner M, Sundseth J. Idiopathic ventral spinal cord herniation: an increasingly recognized cause of thoracic myelopathy. J Cent Nerv Syst Dis. 2014;6:85-91. doi:10.4137/JCNSD.S16180.

6. Nakashima H, Imagama S, Yagi H, et al. Clinical and Radiographical Differences Between Thoracic Idiopathic Spinal Cord Herniation and Spinal Arachnoid Cyst. Spine. December 2016. doi:10.1097/ BRS.0000000000002013.

7. Haber MD, Nguyen DD, Li S. Differentiation of idiopathic spinal cord herniation from CSF-isointense intraspinal extramedullary lesions displacing the cord. Radiogr Rev Publ Radiol Soc N Am Inc. 2014;34(2):313-329. doi:10.1148/rg.342125136.

8. Kendall BE, Valentine AR, Keis B. Spinal arachnoid cysts: clinical and radiological correlation with prognosis. Neuroradiology.

1982;22(5):225-234.

9. Barbagallo GMV, Marshman LAG, Hardwidge C, Gullan RW. Thoracic idiopathic spinal cord herniation at the vertebral body level: a subgroup with a poor prognosis? Case reports and review of the literature. J Neurosurg.

2002;97(3 Suppl):369-374.

10. Nakamura M, Fujiyoshi K, Tsuji O, et al.

Long-term surgical outcomes of idiopathic spinal cord herniation. J Orthop Sci Off J Jpn Orthop Assoc. 2011;16(4):347-351. doi:10.1007/ s00776-011-0065-z.

11. Hughes G, Ugokwe K, Benzel EC. A review of spinal arachnoid cysts. Cleve Clin J Med. 2008;75(4):311-315.

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CASE CHALLENGE

Case Challenge: A Sacral Tumor Matthew Colman, MD A healthy 49 year-old man presented with complaints of scrotal pain, buttock pain, and bilateral S1 radiculopathic pain and numbness. He had difficulty performing a single limb heel-rise on the left and right but otherwise is normal with regard to strength in the L2-S1 myotomes.

He describes normal bowel and bladder habits.

He presented with an MRI of the lumbar spine and sacrum, a technicium-99 bone scan, and a CT of the chest and pelvis which are significant for a destructive, localized lesion in the S1-S4 bodies, compromising most sacral neuroforamina with anterior and posterior epidural extension.

What is the differential diagnosis for an adult with a destructive bony sacral lesion?

• Carcinoma metastasis • Multiple Myeloma • Lymphoma • Chordoma • Giant cell tumor of bone (middle age adults) • Aneurysmal bone cyst (young adults) Most entities in the above differential can appear aggressive with bony destruction. Tumors with very eccentric or non-midline location are less likely to be chordoma, which has a notochordal remnant cell of origin. Relative non-enhancement on the bone scan as with this case may suggest myeloma, but can occur with any tumor in which the normal osteoblastic repair response is suppressed by rapid tumor 16

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A

B C

Figures 1A and 1B demonstrate the sagittal T2 and axial T1 post contrast MRI images of a destructive sacral tumor with intracanal extension. Figure 1C demonstrates a Tc99 bone scan with relative inactivity of the lesion and no distant lesions. growth or tumor cytokine secredemonstrated multinucleated giant tion. Serum laboratory analysis was cells and neoplastic mononuclear normal in this case but may suggest stromal cells characteristic of giant the correct diagnosis via monocell tumor of bone. clonal protein spike (myeloma), or white blood cell count abnormalWhat is the preferred treatment in ities (lymphoma). Additionally, a this case? thorough history and physical may 1. Observation suggest risk factors for metastatic 2. Radical sacrectomy with a marcarcinoma such as a prolonged gin of normal tissue smoking history, breast/thyroid 3. Intralesional tumor excision mass, blood in urine, or others. and neural decompression A posterior- based CT-guided core 4. Selective arterial embolization needle biopsy at our institution 5. Sterotactic, intensity modulat-

ed, or other conformal radiotherapy 6. Medical treatment with an anti-RANK ligand antibody 7. Combinatorial: surgery plus radiation 8. Combinatorial: embolization plus radiation 9. Combinatorial: embolization plus medical treatment Giant cell tumor of bone (GCT) in the axial skeleton is a benign but aggressive disease of middle aged adults which can cause local compromise of bony structure and neural elements. Approximately 5-15% of all GCT occurs in the spine, and like their extremity counterparts, they exhibit benign metastatic potential in the range of 1-5%. Treatment should be individualized, and the extent of treatment should consider the morbidity of the proposed approach, the neurologic status, structural integrity of the spine, and the apparent biology of the tumor. GCT of the spine may behave as either a benign active (Enneking stage 2), or benign aggressive (Enneking stage 3) lesion. Differentiating between these stages is based predominantly on extraosseous extension and rapidity of growth.

Where possible, en bloc resection leads to the best rates of local control, but is not typically possible in the sacrum without undesirable morbidity. Intralesional curettage is often successful at achieving durable local control, but Boriani et al reported that this approach may only be successful in Enneking stage 2 tumors (94% local control) as opposed to stage 3 tumors (39% local control).1 Li et al reported a large series of surgically managed sacral GCT with high failure rates in patients treated with curettage only, suggesting a marginal or en bloc procedure depending on the

Figure 2 demonstrates the prembolization (left) and postembolization (right) fluoroscopic images of the tumor. level of the sacral disease.2 Surgical adjuvants such as argon beam are frequently described and may offer benefit, although evidence is lacking.

A recent systematic review acknowledged that while definitive evidence is poor, there appear to be several effective nonsurgical treatment options for spinal GCT.3 Radiotherapy is a reasonable modality for unresectable or recurrent disease, but evidence is variable regarding its effectiveness, and downstream secondary sarcoma or radiation-induced neural injury are downsides. Selective arterial embolization is advisable prior to intralesional surgery to reduce excessive intraoperative blood loss, but this modality may be used successfully as stand alone therapy, with excellent long-term control, albeit after multiple procedures.4 Use in spinal zones such as the mid thoracic spine which do not have redundant blood supply should be done with care to avoid cord infarct. Finally, there is excellent evidence that the anti-RANK-ligand antibody drug Denosumab can provide local control and regression of disease both perioperatively as adjuvant treatment or as stand-alone therapy. Downsides include usual return

of disease upon therapy cessation, jaw osteonecrosis, and metabolic abnormalities.

Case resolution Our patient underwent stand-alone selective arterial embolization with planned consolidation therapy with Denosumab (Figure 2). Unfortunately, 24 hours post embolization the patient had increased sacral pain, worsening bilateral S1 weakness (4/5), and complete loss of bowel and bladder function. An urgent MRI (Figure 3) was obtained which demonstrated stable extensive appearance of the tumor with some increased intra-canal prominence. It was presumed that vascular congestion or tumor swelling as a result of the embolization led to a tipping point in neural compressive mass effect. The patient was taken emergently for sacral laminectomy with some improvement in his saddle anesthesia but persistent bowel and bladder deficits. He also suffered in subsequent days from geographic embolization-related skin necrosis. After wound equilibrium was achieved through local dressings, Denosumab was started. Over the next six months, the tumor regressed radiographically (Figure 4) and the patient regained Vertebral Columns • Spring 2018

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Figure 3 demonstrates the MRI appearance (T2 sagittal / T1 post contrast axial) of the tumor 24 hours post embolization with acute loss of bowel and bladder function.

Figure 4 demonstrates the MRI appearance (T2 sagittal / T1 post contrast axial) of tumor involution after 6 months of denosumab therapy. independent urinary function and partial bowel control.

Conclusion This challenging case demonstrates the diagnosis and multidisciplinary treatment options available for a benign aggressive sacral tumor.

Complication profiles for all treatment modalities have the potential to be significant, but Denosumab has emerged as an excellent modality for recurrent or unresectable giant cell tumor of bone. The drug may also be a good induction modality to modify the disease burden, facilitating other modalities such as surgery or embolization.

References

1. Boriani S, Bandiera S, Casadei R, Boriani L, Donthineni R, Gasbarrini A, et al. Giant cell tumor of the mobile spine: a review of 49 cases.

Spine 2012;37:E37–45.

2. Li G, Fu D, Chen K, Ma X, Sun M, Sun W, et al. Surgical strategy for the management of sacral giant cell tumors: a 32-case series. Spine J 2012;12:484–91 3. Luksanapruksa P, Buchowski JM, Singhatanadgige W, Rose PC, Bumpass DB. Management of spinal giant cell tumors. Spine J. 2016 Feb;16(2):259-69.

4. Lin PP, Guzel VB, Moura MF, Wallace S, Benjamin RS, Weber KL, et al. Long-term follow-up of patients with giant cell tumor of the sacrum treated with selective arterial embolization. Cancer 2002;95:1317–25.