Advanced Minimally Invasive Techniques: Management of High-grade Spondylolisthesis
and Thoracic Metastatic Spinal Disease
Abbas Naqvi1, Mohamed Noureldin1, Islam M. Elboghdady1, Khaled Aboushaala1, Hamid Hassanzadeh2, Eric Sundberg1, Kern Singh1
1Rush University Medical Center, Chicago, IL, USA
2University of Virginia, Charlottesville, VA, USA
Correspondence author: Kern Singh, MD, Associate Professor, Department of Orthopaedic Surgery, Rush University Medical Center 1611 W. Harrison St, Suite #300 Chicago, IL 60612; Fax: 708- 492-5373, E-mail: Kern.firstname.lastname@example.org
Citation: Naqvi A, Noureldin M, Elboghdady IM, Aboushaala K, Hassanzadeh H, Sundberg E, Singh K. Advanced Minimally Invasive Techniques: Management of High-grade Spondylolisthesis and Thoracic Metastatic Spinal Disease. J Minim Invasive Orthop, 2014, 1(2): e2. doi:10.15383/jmio.2.
Competing interests: The authors have declared that no competing interests exist.
Conflict of interest: None
Copyright: 2014 By the Editorial Department of Journal of Minimally Invasive Orthopedics. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abstract：Recentadvances in spine surgery technology and instrumentation have allowed for the development of minimally invasive (MIS) techniques. These muscle-sparing approaches have been demonstrated to provide superior, if not similar, outcomes to traditional open techniques. However, MIS techniques are associated with a steep learning curve and greater radiation exposure. Furthermore, while suitable for most degenerative spinal conditions, MIS approaches may not be appropriate for complex spinal pathology. This articlediscusses the literature onopen and advanced MIS techniques for high-grade isthmic spondylolisthesis and metastatictumors of the thoracic spine. Additionally, the authors’ preferred techniques along with their associated pearls and pitfalls are presented for both complex pathologies.
Keywords：Minimally Invasive Techniques; MIS; High-grade; Isthmic Spondylolisthesis; Thoracic Tumor; Lateral Retropleaural; Corpectomy; Transforaminal Lumbar Interbody Fusion; TLIF
Traditional open approaches to spinal surgery require extensive disruption of the paraspinal musculature as a result of the use of wide surgical corridors and self-retaining retractors.1-4 Recently, minimally invasive spine surgery (MIS) techniques have been developed to decrease retraction pressure and limit soft tissue damage5. In addition, MIS techniques demonstrate superior results in regards to blood loss, post-operative VAS scores, length of hospitalization and the subsequent financial burden placed on the treating institution.1-4 However, MIS techniques are associated with a steep learning curve, further exacerbated by a paucity of training opportunities, and a greater radiation exposure to the patient and surgical team.1-4 Furthermore, MIS procedures may not be appropriate for challenging and complex spinal pathology.
The purpose of this paper is to discuss the literature available on advanced MIS approaches to two surgically challenging spinal pathologies: high-grade isthmic spondylolisthesis and metastatictumors of the thoracic spine.
1. MIS Management of High-grade Isthmic Spondylolisthesis
Isthmic spondylolisthesis, defined as the forward progression of the vertebral body as a result of fractured pars interarticularis, is one of the most common forms of spondylolisthesis being present in 7-8% of the adult population.6,7 Low-grade disease can be managed non-operatively8. High-grade disease, classified as a slip greater than 50% as seen on imaging, can result in kyphosis, worsening slip progression, and increased risk of neurological compromise.6,7,9,10 As such, the indication of surgery for the management of symptomatic high-grade spondylolisthesis is generally agreed upon. 6,10-12
Open Surgical Approaches
High-grade isthmic spondylolisthesis can be managed by circumferential, anterior, transforaminal, or posterolateral fusionswith or without reduction.12Circumferential fusions have superior rates of fusion but increased operative time and blood loss.8 Anterior lumbar interbody fusions (ALIF) have demonstrated better restoration of sagittal balance, a critical parameter in the case of high-grade spondylolisthesis which is more likely to present with segmental kyphosis and compensatory hyperlordosis8,12. In addition, Min et al demonstrated ALIF’s superiority in terms of prevention of adjacent segment degeneration8,13. However, ALIF is further complicated by the need to gain access to the retro-peritoneum as well as mobilize the great vessels.14
Kim et al demonstrated transforaminal lumbar interbody fusion’s (TLIF) superiority in regards to clinical outcomes, measured by post-operative Oswestry Disability Index (ODI) scores, as well as operative time and hospitalization when compared to ALIF. Posterolateral fusion (PLF) produces poor fusion rates when used alone but has demonstrated superior fusion rates compared to the other techniques when utilized in conjunction with ALIF.8Nevertheless, gaining access to the pathology may be particularly challenging with posterior approaches, such as TLIF and PLF, due to the degree of anterolisthesis.
In addition to the typical disruption of the paraspinal musculature typically required by an open approach, the degree of anterolisthesis present in high-grade spondylolisthesis requires an even deeper dissection. The evolution of MIS surgery has resulted in MIS approaches to virtually all open techniques with the benefit of less soft-tissue disruption.5
Quraishi and Rampersaud described a bilateral “minimal access” approach working space that is inferior and medial compared to a standard TLIF in order to avoid the nerve root that typically obscures the disc space in high-grade spondylolisthesis.3An osteotome, under fluoroscopic guidance, was traced along the caudal pedicle and endplate in order to gain access to the collapsed disc space.3This was repeated on the contralateral side and a bilateral discectomy was performed. Spondylolisthesis reduction screws and rod were inserted with the osteotomes still within the disc space, serving as a tract to reduce the translated vertebrae.3 Local autogenous bone graft was then inserted and an interbody device was placed. Patient had significant clinical improvement, measured via VAS and ODI scores, and 8 month postop CT demonstrated arthrodesis.3 In addition, there was a 68% improvement in slip percentage and 40 degree improvement in slip angle.3
Preferred Surgical Technique
The level of interest is identified under fluoroscopic guidance. A perfect anterior-posterior (AP) view is obtained where the pedicles are symmetric, the spinous process bisects the vertebral body, and the endplates appear linear (Figure 1) (Figure2). A Jamshidi needle is advanced through the fascial incision and paraspinal musculature until reaching the lateral boarder of the pedicle as confirmed on fluoroscopy. The needle is then advanced in 5mm increments into the pedicle under AP fluoroscopic guidance. After advancing 15mm into the pedicle, a guidewire is placed until the tip of the guidewire reaches the medial wall of the pedicle in the AP fluoroscopic view (Figure 3). A lateral view is then obtained to confirm that the tip of the guidewire has crossed the posterior wall of the vertebral body. The pedicles are then cannulated above and below the level of fusion and an initial dilator is passed between the guidewires. Sequential dilation is performed and a tubular retractor is docked onto the pars interarticularis bilaterally at the level of interest. A high-speed burr is utilized to perform a laminectomyto the insertion of the ligamentum flavum proximally. The burr is then used to pass through the pars interarticularis laterally and the inferior articular process of the cephalad vertebrae is then removed bilaterally. The intervertebral disc space is identified and bipolar electrocautery is utilized to coagulate the overlying epidural veins. After adequately protecting the neural structures, an annulotomy is then performed with anosteotome to remove the posterior aspect of the vertebral body of the inferior level (Figure 4). A Kerrisonrongeur can be utilized within the annulotomy to release the posterior longitudinal ligament (PLL) as far to the contralateral side as possible. A subtotal discectomy is then performed with a combination of disc shavers, pituitary rongeurs, and curved curettes. Contralateral pedicle screws can be placed to distract the disc space for further endplate preparation. Once the disc space has been accessed a provisional paddle distractor can be placed while the end plate preparation is performed from the contralateral tube. A combination of distraction and alternating sides of the disc space preparation will allow the sub-total discectomy to be safely accomplished. Once the disc space is complete bilateral cages can be inserted to maximize disc height, correct segmental kyphosis, and to increase the surface area of the fusion bed (Figure 5).
Figure 1. AP radiograph demonstrating the congenital dyplasia of the posterior L5 and S1 elements.
Figure 2. Lateral radiograph demonstrating the isthmic spondylolisthesis at L5-S1 with significant focal kyphosis.
Figure 3. AP fluoroscopic view demonstrating proper advancement of the guidewires to the medial wall of the pedicle.
Figure 4. Lateral fluoroscopic view demonstrating the osteotomy of the posterior aspect of the vertebral body performed through the tubular retractor.
Figure 5. Lateral fluoroscopic view demonstrating placement of the interbody cage within the intervertebral space. Disc height and lordosis have both been restored.
With the cages in place, the pedicle screws can then be placed. A pedicle tap is advanced over the guide wire until it crosses the posterior vertebral body wall. The tap is removed over the guide wire and a cannulated pedicle screw of the appropriate length and diameter is then inserted under fluoroscopic guidance. After screw placement, an AP and lateral fluoroscopic view should be obtained to assess the screw positioning (Figure 6) (Figure 7). An appropriately sized rod is then inserted submuscularly through the screw slots and compression is applied across the intervertebral graft. An active reduction can be accomplished at this time if desired (it is the preference of the senior author to not perform an active reduction because of concerns of neurological injury).
Figure 6. AP fluoroscopic view demonstrating proper instrumentation and interbody cage placement.
Figure 7. Lateral fluoroscopic view demonstrating proper instrumentation and interbody cage placement as well as improvement in spinopelvic sagittal alignment.
Pearls and Pitfalls
The MIS approach, in addition to the previously discussed challenges, can be particularly difficult to perform in the presence of high-grade spondylolisthesis. Due to the degree of anterolisthesis, proper triangulation and placement of the tubular retractor can be challenging, especially in obese patients. Additionally, achieving reduction is arduous and presents with the same risk of neurological compromise as open surgery.
2. MIS Management of Thoracic Spinal Tumors: An MIS retropleural Approach
Management of primary and metastatic tumors of the anterior spine has historically represented a challenge in spine surgery. About 5% to 10% of all cancer patients develop a metastasis to the spine during the course of their disease. Thus, cord compression that is due to metastases is likely secondary to disease within the vertebral body.15-18The anatomical restraints related to the anterior spine add to the challenge of choosing the surgical approach for the treatment of these pathologies. As such, a number of open and thoracoscopic techniques have been developed.
Open approaches typically necessitate wide thoracotomies dissecting through the pleural cavity, and require double lumen intubation with single lung ventilation during the procedure and a chest tube postoperatively.19As a result, open techniques are associated with significant morbidity including pleural effusions, hemothorax, atelectasis, postoperative intercostal neuralgia, and post-thoracotomy pain.20-24Thoracoscopic approaches are oftentimes complicated with poor visualization and postoperative pleural adhesions that can potentially compromise pulmonary function. In addition, thoracoscopy requires expensive equipment and is associated with a steep learning curve. Consequently, In recent years, minimally invasive (MIS) techniques have been developed for accessing the thoracic spine.25
MIS Retropleural Approach
Scheufler described a retropleural approach in which a retractor system was utilized to displace the lungs and vasculature in order to gain access to the dorsal aspect of the mid and upper thoracic spinal canal.19 The vertebral body, with the exception of the ventral and contralateral cortex, was removed and an expandable VBR device was inserted into the subsequent defect.The device space around the device was packed with demineralized bone matrix. The patients demonstrated favorable clinical outcomes with significant reductions in perioperative morbidity and pain. Uribe et al expanded upon this approach by utilizing sequential tubular dilators.26Similar approaches have been described by Kasliwal and Deutsch and Keshavarzi et al.16,27
The MIS technique allows reconstruction of the anterior column with similar visualization to its open counterpart. Ideally, an MIS approach is suited for 1-2 level procedures, however up to 3-level corpectomy procedure have been reported in the literature.19,28,29The superior anterior thoracic spine remains a difficult region to access due to the scapula and shoulder girdle limiting access.16,25
The level of interest is localized utilizing lateral fluoroscopic guidance. A 3-4cm incision is made at the midaxillary line directly over the index vertebra in the direction of the rib.19 The rib is then exposed subperiosteally and the neurovascular bundle is reflected inferiorly.Approximately 2 cm of the rib overlying the index vertebra is resected and set aside for use as autograft21,28. At this point the parietal pleura isexposed and the plane between the pleura and endothoracic fascia is developed with a sponge stick21,28. The initial dilator is then advanced under fluoroscopic guidance and tactile feedback until it docks onto the lateral aspect of the vertebral body. Sequential dilation is then performed. An expandable retractor is placed over the dilators and subsequently secured onto the table mounted retractor arm. The vertebra and intervertebral discs above and below are subperiosteally exposed and the segmental artery is cauterized and resected as proximally as possible. The rib head at the corresponding vertebra is identified and resected, thereby exposing the posterior vertebral body, pedicle, and intervertebral discs (Figure 8).29 The borders of the corpectomy are defined by resecting the intervertebral discs above and below with an angled curette and a Kerrisonrongeur. The vertebral body is then resected utilizing a high-speed burr, rongeurs, and curettes (Figure 9). Care should be taken to preserve a thin portion of the anterior cortex and the anterior longitudinal ligament (The anterior cortex is resected in cases of primary spinal tumors). If the posterior longitudinal ligament is not part of the compressive pathology, it should be left intact.29
Figure 8. Cauterization and resection of the segmental artery and exposure of the pathologically fractured vertebral body.
Figure 9. Completed corpectomy with preservation of a thin portion of the anterior longitudinal ligament.
Lateral fluoroscopic imaging is utilized to confirm the extent of the corpectomy. An expandable titanium cage is then sized and placed into the defect for reconstruction of the vertebral body (Figure 10). The cage is expanded under lateral fluoroscopic imaging until the desired sagittal alignment is achieved. Autologous bone graft or a substitute is placed inside the cage to promote fusion. Final fixation is achieved with the placement of anterolateral plates on the adjacent vertebrae with a dual rod construct connecting the two plates. Percutaneous pedicle screws can also beutilized to supplement the fixation or in lieu of anterior fixation.24,30
Figure 10. An appropriately sized expandable titanium cage is placed within the defect.
Pearls and Pitfalls
Resection of the rib allows for easier expansion of the retractor without concern for a rib fracture. Additionally, the rib can be re-approximated at the end of surgery with a maxillofacial plate. Typically a three bladed retractor is utilized. The blades are oriented such that no blade is placed posteriorly. In this orientation, there is no blade obscuring visualization of the posterior vertebral body and spinal canal.
The discectomy can help identify the boundaries of the anterior column and spinal canal and should be performed prior to the corpectomy.29It is also important to perform the discectomies and resect the segmental artery prior to starting the corpectomy as bleeding is most severe during the bony resection.29Any remaining bleeding can then be controlled with bone wax or a gelfoam.19Preservation of the PLL in non-compressive pathology helps to avoid over distraction of the spinal segment. Care is taken to pack bone graft around the cage, as the fusion mass occurs oftentimes around the corpectomy cage.
Pleural tears are the most common complication encountered through the MIS lateral retropleural approach, occurring in 3 of 38 (7.9%) patients in a series by Scheufler.19 The surgeon must be cognizant of the risk and be prepared to place a chest tube or red rubber catheter at the end of the procedure to treat the pneumothorax.28
Despite posing technical challenges, advances in instrumentation and techniques are allowing for the development of viable MIS approaches to complex spinal pathology, previously only manageable via open surgery. While the literature is limited, early reports have demonstrated good clinical outcomes and further studies need to be performed to assess the feasibility of these techniques as alternatives to open surgery.
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