Original Article
Minimally Invasive Direct Lateral Approach to the Thoracolumbar Junction: Cadaveric Analysis and Case Illustrations David Straus1
Ippei Takagi1
John O’Toole1
1 Department of Neurological Surgery, Rush University Medical Center,
Chicago, Illinois, United States J Neurol Surg A 2015;76:56–62.
Abstract
Keywords
► direct lateral interbody fusion ► thoracolumbar junction ► minimally invasive spine surgery ► XLIF ► DLIF
Background Multiple surgical exposures to the thoracolumbar junction have been described. The minimally invasive direct lateral approach to the lumbar spine captures the advantages of anterolateral approaches while minimizing soft tissue destruction and perioperative morbidity. Utilizing this approach at the thoracolumbar junction presents unique anatomical challenges posed by the ribs, diaphragm, pleura, and lung. Methods We examine the use of a minimally invasive direct lateral approach to the thoracolumbar junction (T10–L2) through six cadaveric approaches and provide case examples of three patients. Results In six approaches with normal spinal alignment we were able to access all disc spaces in the thoracolumbar region. The L2–L3 disc was accessed below the 12th rib in 100% of spines; L1–L2 accessed through the T11–T12 intercostal space in 83% of spines; T12–L1 was accessed through the T11–T12 intercostal space in 67% of spines and through the T10–T11 intercostal space in 33% of spines; T11–T12 was accessed through the T10–T11 intercostal space in 83% of spines; finally, T10–T11 was accessed through the T10–T11 intercostal space in 67% of spines and through the T9–T10 intercostal space in 33% of spines. Discussion The minimally invasive direct lateral approach offers access to ventral pathology at the thoracolumbar junction. Familiarity with common anatomical structures encountered during this approach in the thoracolumbar junction enhances surgical planning and facilitates surgical exposure.
Introduction Surgical approaches to spinal pathologies at the thoracolumbar junction (T10–L2) may be classified as anterior, posterior, or posterolateral. Anterior approaches include the anterolateral thoracotomy, thoracoscopic thoracotomy, and the retropleural thoracotomy.1 These approaches offer extensive anterior exposure that is advantageous in treating pathologies located ventral to the thecal sac. However, thoracotomy increases the intraoperative physiologic stress, exposes the
received May 10, 2013 accepted after revision December 30, 2013 published online May 2, 2014
Address for correspondence David Straus, MD, Department of Neurological Surgery, Rush University Medical Center, 1725 W. Harrison St., Suite 855, Chicago, IL 60612, United States (e-mail: [email protected]).
patient to approach-related complications, and prolongs the postoperative hospital course.1–4 Moreover, transthoracic approaches require the assistance of an access surgeon, and thoracoscopic techniques require significant operator experience.5 Posterior approaches to the thoracic spine include laminectomy and transpedicular approaches.6 Thoracic laminectomy may be sufficient for decompression of some thoracic spinal lesions; however, ventral pathology is totally inaccessible via this approach due to the small size of the spinal canal in relation to the thoracic spinal cord.7–9 A
© 2015 Georg Thieme Verlag KG Stuttgart · New York
DOI http://dx.doi.org/ 10.1055/s-0034-1372431. ISSN 2193-6315.
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transpedicular approach enables increased access to ventral thoracic spinal pathology.10 However, it is still a posteriorbased approach whose access to ventral pathology is limited by the presence of the spinal cord and the trajectory of the surgical corridor.11 The costotransversectomy12 and lateral extracavitary13 approaches are posterolateral approaches that offer increasingly lateral trajectories and thus allow for direct access to ventral pathologies without entrance into the pleural cavity. The posterolateral approaches may be achieved without the aid of an access surgeon and offer surgical exposure of ventral lesions comparable with anterior-based approaches. The primary disadvantage of the posterolateral approaches is the need for extensive soft tissue dissection, resulting in increased operative time and blood loss.14–16 Posterolateral approaches, moreover, do not allow for anterolateral interbody device placement and fusion, which has become a powerful tool in both focal- and long-segment deformity correction. Recently, minimally invasive direct lateral approaches to the lumbar spine have become more widely utilized, offering comparable benefits of ventral spinal exposure but also minimizing the extent of soft tissue dissection required for the exposure.11,16–18 These retrocoelomic techniques are particularly appealing when approaching the thoracolumbar junction in that they may avoid entry into the pleural cavity and do not necessitate the assistance of an access surgeon. We have performed minimally invasive tubular approaches to the thoracolumbar spine using a direct lateral approach similar to that described by Uribe et al.17 Anatomical study of the specific access points, soft tissue structures, and body cavities related to this approach has not been described. Here we examine this approach in a cadaveric model and describe our experience using this approach.
Methods Cadaveric Dissection We performed a minimally invasive direct lateral approach to the thoracolumbar junction in six fresh cadavers (three placed in the right-side-up lateral decubitus position and three placed in the left-side-up lateral decubitus position). Minimally invasive surgery (MIS) tubular access to the thoracolumbar disc spaces was performed under fluoroscopic guidance. Soft tissue structures and body cavities were examined with the aid of a surgical microscope.
Surgical Technique The cadaver is placed in the lateral decubitus position and carefully secured to the operating table. The bed can be flexed at the kidney break between the iliac crest and the rib cage if necessary for lumbar exposure but is generally not necessary for thoracolumbar junction exposure. Fluoroscopy is used to confirm access to the levels of interest and to mark incisions. Multilevel procedures often require multiple incisions to provide the proper entry angles. Also for multilevel procedures we proceed in a caudal to rostral fashion, addressing the lowest level first and successively working upward. This is
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done particularly in cases involving L4–L5 but also facilitates the access to the thoracolumbar junction levels by initially having subdiaphragmatic access. Skin incision is made in line with the intercostal space. Although not necessary for surgical access, rib autograft may be harvested at this point. Resecting a 3- to 4-cm segment of rib will allow expanded access for the retractor. Dissection through the rostral terminations of the lateral abdominal wall musculature and/or intercostals muscles is performed with blunt spreading and finger dissection. The costal insertions of the diaphragm, when present, can similarly be bluntly spread apart without the need to completely strip the diaphragmatic attachments. Access to the disc space is through either the retroperitoneal or retropleural space, not unlike that described by Kim et al19 using open techniques. Once in the retrocoelomic space, further dissection is performed bluntly to displace the retroperitoneal contents, the diaphragm, or the lung anteriorly, following the course of the correlating proximal rib to the desired disc space or until the transverse process at L1 or L2 is palpable. Under fluoroscopic guidance, a guidewire is placed in the disc space and serial tissue dilators are used to place an expandable tubular retractor system (Globus Medical, Inc., Audubon, Pennsylvania, United States) over the lateral aspect of the disc space being treated as described previously.20 This may involve dilation through either the upper psoas muscle or through the diaphragmatic crus. Neurophysiologic stimulation of the dilators and retractor blades may be used to ensure avoidance of nerves within the upper lumbosacral plexus.21 The retractor is expanded as needed, and under loupe magnification and internally placed lighting, residual strands of psoas muscle or diaphragmatic crus are dissected off the disc space. A complete discectomy is performed, the disc space is prepared for arthrodesis, and appropriate size interbody grafts are impacted into place. Lateral instrumentation, if desired, can be placed and hemostasis achieved. Upon removal of the retractor, the soft tissues are inspected. The fascia of the abdominal wall/intercostals is then closed in an interrupted fashion. If the pleural space has been entered, the final fascial stitch is left untied and a red rubber catheter in placed into the pleural space. The opposite end is submerged underwater in a kidney basin. A Valsalva maneuver is performed to expel any intrathoracic air. During the Valsalva, the catheter is quickly removed and the final fascial suture tied, completing the closure of the thoracic cavity. Final closure of the wound is performed in layers. The patient can then be placed prone to perform any posterior decompression or instrumentation in either an open or percutaneous manner. An immediate postoperative upright chest radiograph is obtained in the recovery area to assess for pneumothorax.
Case Illustrations We review three patients who underwent lateral MIS tubular approaches to the thoracolumbar junction (defined here as procedures involving any segment in between T10 and L2). All procedures were performed between 2008 and2011 at Rush University Medical Center by the senior author (J.E.O.). Journal of Neurological Surgery—Part A
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Minimally Invasive Approach to the Thoracolumbar Junction
Minimally Invasive Approach to the Thoracolumbar Junction
Fig. 1 Patient positioning. True anteroposterior and lateral fluoroscopic views must be obtained to facilitate working angles once retractors are set in place. Disc spaces are marked in blue ink; T12 rib is marked by the longest line.
Results Cadaveric Study We performed six minimally invasive direct lateral approaches in cadaveric spines with relatively normal coronal alignment (20 degrees Cobb angle) at all levels in the thoracolumbar junction starting at the L2–L3 disc space and proceeding cranially to the T10–T11 disc space (►Figs. 1–5). Abdominal wall musculature was encountered in all specimens in incisions made below the T12 rib; intercostal musculature was encountered in all incisions between the T12 and T9 ribs. A 3to 4-cm segment of rib was accessible through the skin incision in all specimens for autograft if desired. Access to the L2–L3 disc space transversed the retroperitoneum in all spines, and the disc space was covered laterally by psoas muscle in all specimens. The L1–L2 disc space was accessed through the retroperitoneum in 67% of the spines and through the pleural cavity in 33% of the spines; psoas muscle covered the disc in 50%, in 17% diaphragmatic crus was present, and in 33% no muscular fibers covered the disc space. The T12–L1 disc space
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Fig. 3 In the figure on the left, the skin incision and subcutaneous dissection to the abdominal wall musculature is seen. On the right, blunt dissection through the abdominal wall or intercostals musculature to enter the retroperitoneal or retropleural space is shown. After entry into the retrocoelomic space is achieved, blunt finger dissection is performed down to the vertebral column.
was accessed through the retroperitoneal cavity 67% of the time and through the pleural cavity 33% of the time; 50% of spines had fibers of the diaphragmatic crus over the disc space, and 50% had no muscle covering the disc. The T11–T12 disc and the T10–T11 disc were accessed through the pleural space in all spines; no muscle was encountered over the disc space in any specimen at either level. A successful approach to all levels was achieved in all specimens without manipulation of the great vessels. Every disc space in the thoracolumbar junction was accessible in all spines from a direct lateral approach without the need for rib resection. L2–L3 disc was accessed below the 12th rib in 100% of spines; L1–L2 was accessed below the 12th rib in 17% of spines and through the T11–T12 intercostal space in 83% of spines; T12–L1 was accessed through the T11–T12 intercostal space in 67% of spines and through the T10–T11 intercostal space in 33% of spines; T11–T12 was accessed through the T11–T12 intercostal space in 17% of spines and through the T10–T11 intercostal space in 83% of spines; finally, T10–T11 was accessed through the T10–T11 intercostal space in 67% of spines and through the T9–T10 intercostal space in 33% of spines (►Table 1).
Case Examples
Fig. 2 Localization over the T11–T12 disc space to finalize location of skin incision. Journal of Neurological Surgery—Part A
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For illustration, we present three patients who underwent a direct lateral minimally invasive approach to the thoracolumbar junction using the surgical technique previously described (►Table 2). All patients had degenerative spinal pathology as an indication for their surgery. The intervertebral cages were all made of polyetheretherketone and were packed with autograft rib or rhBMP-2 (Medtronic, Memphis, Tennessee, United States) with β-tricalcium-phosphate. Supplemental instrumentation was used in all cases. In one case performed for a single-level adjacent segment degeneration, a lateral plating system was used, and in the other two cases performed for adult degenerative scoliosis, correction pedicle screw instrumentation was used. Placement of supplemental posterior fixation was done in a staged manner on a different
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Fig. 4 (A) Insertion of initial dilator for localization. (B) Serial dilation over disc space on lateral fluoroscopy. (C) Anteroposterior (AP) fluoroscopy confirming appropriate alignment with disc space. (D) Final placement of retractor on AP fluoroscopy. (E) Final placement of retractor on lateral fluoroscopy.
day in these two patients. No patients required a chest tube at the end of the operation. Two patients had small pneumothoraces identified on postoperative chest X-ray; both were asymptomatic and neither required more than nasal cannula oxygen for management.
Discussion
Fig. 5 The view through the retractor is seen in the figure on the left. Note that the soft tissue covering disc space may contain psoas muscle, diaphragmatic crus, or no muscle. This soft tissue is dissected off the disc space to expose the lateral annulus. The final exposure of disc space after soft tissue removal and discectomy is shown in the figure on the right.
Minimally invasive direct lateral approaches to the thoracolumbar junction are a relatively new approach that offer a promising alternative to more invasive open posterolateral and anterior approaches while preserving many of their benefits.11,17,18,21–23 In our experience, this approach has proven useful in the management of degenerative conditions and thoracolumbar scoliosis.22 Its application to neoplastic, Journal of Neurological Surgery—Part A
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Minimally Invasive Approach to the Thoracolumbar Junction
Minimally Invasive Approach to the Thoracolumbar Junction
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Table 1 Results of cadaveric thoracolumbar direct lateral approaches L2–3, %
L1–L2, %
T12–L1, %
T11–T12, %
T10–T/11, %
Body cavity (n ¼ 6) Retroperitoneum
100
67
67
0
0
Retropleural
0
33
33
100
100
Psoas
100
50
0
0
0
Crus
0
17
50
0
0
Neither
0
33
50
100
100
Below 12th rib
100
17
0
0
0
T11–T12 intercostal
0
83
67
0
0
T10–T11 intercostal
0
0
33
100
67
Deep muscle (n ¼ 6)
Access point (n ¼ 6)
T9–T10 intercostal
0
0
0
0
33
Unable to access
0
0
0
0
0
traumatic, and infectious pathologies has also been reported.17,23,24 Exposure is adequate to perform corpectomies and place interbody cages.17 Access to the lateral aspect of the disc space enables direct visualization of the ventral thecal sac without spinal cord retraction, resulting in safer surgical decompression of ventral pathologies (e.g., retropulsed bone, epidural abscess, epidural tumor, herniated disc, and osteophytes). The results of our cadaveric studies show that the retrocoelomic approach used in direct lateral access to the thoracolumbar junction transverses the retroperitoneum in levels below L2 and transverses the retropleural space in levels above T12. The L1–L2 interspace and the T12–L1 interspace thus represent a transitional region, and approach to these levels may involve accessing either or both the retroperitoneum and the retropleural space. The psoas muscle thins toward its superior attachments at L1. It is consistently encountered during the direct lateral approach at levels below L1–L2, inconsistent at T12–L1, and not present at levels above T12. The fibers of the diaphragmatic crus are most commonly encountered at T12–L1 and occasionally found at L1–L2. In our experience, it has not been necessary to detach the diaphragm from its connections to the thoracolumbar junction at the diaphragmatic crus, as was previously described.18 The diaphragmatic crus was encountered only when accessing L1–L2 or T12–L1 in our cadaveric series, and the muscle fibers were adequately spread with the tubular dilators and retractors to expose the disc space. Similarly, we have only encountered postoperative pneumothoraces after accessing levels above L1 (where the diaphragmatic crus inserts). When the pleura is encountered during the initial approach, a retropleural dissection is attempted when possible using finger or dilator dissection. However, even if the parietal pleural is violated, chest tube insertion is Journal of Neurological Surgery—Part A
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not necessary. Access to the T12–L1 and L1–L2 spaces is most typically achieved through the 11/12th intercostal space. Access to the disc space and body is adequate using the intercostal space. Partial rib resection, however, often may be used for autograft material. Specific surgical considerations vary across the different levels in the thoracolumbar junction. At the upper lumbar levels, the lumbar plexus remains an important consideration. The roots of the plexus run in the dorsal-most quarter of the vertebral body (“zone IV”), with the important exception of the genitofemoral nerve, which runs through the psoas in the anterior half of the L2–L3 interspace (“zone II”). Thus at L2–L3, special attention must be paid to the root dorsally and to the genitofemoral nerve ventrally. At L1–L2 the roots and divisions (both ilioinguinal and iliohypogastric nerves) remain important considerations in addition to considering the diaphragmatic attachments and transitional nature of this level. At T12–L1 the diaphragm and its insertions remain an important consideration. At T11–T12 and T10–T11, the approach will almost certainly be retropleural. Care should be taken to avoid pleural tears where possible, and attention must be paid to minimizing the risk/consequences of postoperative pneumothorax. Our experience with the minimally invasive direct lateral approach has primarily been for the purpose of performing an interbody fusion and anterior column augmentation for degenerative scoliosis correction. In general, our typical approach is on the concavity of scoliotic curves to (1) enhance positional reduction of the curve with flexing of the operating table, (2) increase the height of the most collapsed side of the disc space, (3) allow access to L4–L5 disc, which is typically inaccessible from the convexity of a lumbar coronal curve, and (4) allow exposure of a greater number of disc spaces through a single interspace. Combined thoracic and lumbar
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Table 2 Case description of thoracolumbar direct lateral fusion Patient
1
2
3
Age, y
65
65
62
Sex
F
F
M
Diagnosis
Lumbar scoliosis
Thoracolumbar scoliosis, lumbar stenosis
T12–L1 Adjacent level disease
Prior same-level surgery
No
No
Yes
Procedure
T12–L5 DLIF, staged posterior L5–S1 TLIF, and percutaneous T12–pelvis screws
T11–L5 DLIF, T9–T11 MIS facet fusion, staged T9–L5 percutaneous screws, L3–L5 MIS laminectomies
T12–L1 DLIF with lateral plate fixation
Supplemental instrumentation
Pedicle screws, rods
Pedicle screws, rods
Lateral plate fixation
Staged
Yes
Yes
No
DLIF levels treated
5
6
1
Demographics
Thoracolumbar DLIF levels treated
2
3
1
Rib resection, autograft
Yes
Yes
No
OR time, min
300
415
220
EBL
150
500
150
Pneumothorax
Yes
Yes
No
Chest tube needed
No
No
No
Postoperative
Hospital LOS, d
8
9
7
Complications
Posterior wound infection, osteoporotic screw pullout
None
None
Abbreviations: DLIF, direct lateral interbody fusion; EBL, estimated blood loss; LOS, length of stay; MIS, minimally invasive surgery; OR, operating room; TLIF, transforaminal lumbar interbody fusion.
curves in multilevel cases require careful preoperative planning to ensure ease of access to all desired levels. In line with the goal of appropriate spinal reconstruction, all patients in our series received supplemental fixation. In patients with adult degenerative scoliosis, our current practice is to supplement the lateral interbody grafts with posterior instrumentation (percutaneous or open depending on the needs for deformity correction). Lateral plating offers a suitable and readily available option through this approach as well; its use was previously described in the setting of herniated discs, trauma, and tumors.24 Supplemental instrumentation in other settings may not be mandatory, especially for certain single-level cases such as thoracic herniated discs.11 The anatomical relationships presented in this article, previously unreported in the literature, should prove valuable in surgical planning, approach trajectories, and complication avoidance. Persistent surgical pain at the direct lateral site has not been noted in our experience. Previously reported complications of the minimally invasive direct lateral approach to the thoracolumbar junction include unintended durotomy, intercostal neuralgia, venous thromboembolism, hemothorax, pleural effusion, hardware failure, and wound infection.24
Incidence of surgical complications was 12.5% in a series of 80 patients who underwent this approach for a variety of different pathologies. We have not encountered any clinically significant pneumothoraces, although asymptomatic pneumothoraces were present in two of our cases. Evacuation of air via the red rubber catheter technique described earlier in cases in which the pleural space is entered may help maintain a low incidence of symptomatic pneumothorax by using this surgical approach. There were no complications related to the direct lateral technique itself. Weaknesses of this study include the relatively small number of cases and cadavers analyzed. Cadaveric specimens with more severe coronal scoliosis were not available and could influence the anatomical relationships described here. Clearly, such pathology would need to be accounted for when planning surgical approaches. The purpose of this report was to describe the anatomical characteristics and general feasibility of the minimally invasive direct lateral approach to the thoracolumbar junction. Although real-time fluoroscopic localization and incisional planning remain critical to this surgical technique, we hope that the anatomical data may enhance surgical planning, especially in the preoperative setting. Journal of Neurological Surgery—Part A
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Operative
Minimally Invasive Approach to the Thoracolumbar Junction
Conclusion
11 Uribe JS, Smith WD, Pimenta L, et al. Minimally invasive lateral
Minimally invasive direct lateral access to the thoracolumbar junction is a relatively new surgical approach. It offers many of the advantages of previously described open anterolateral approaches but with a significantly reduced extent of soft tissue dissection and no need for thoracostomy tube placement. This has allowed for reduced approach-related pain and much earlier postoperative mobilization for these patients. This technique may be applied to a wide spectrum of pathologies involving the ventral spine at the thoracolumbar junction. Facility with minimally invasive techniques is necessary to safely and successfully use this approach. In the small series of patients presented here, this minimally invasive direct lateral approach to the thoracolumbar junction appears safe and effective.
12 13
14
15 16
17
References 1 Ikard RW. Methods and complications of anterior exposure of the 2 3
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6 7 8 9
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thoracic and lumbar spine. Arch Surg 2006;141(10):1025–1034 Bohlman HH, Zdeblick TA. Anterior excision of herniated thoracic discs. J Bone Joint Surg Am 1988;70(7):1038–1047 Faciszewski T, Winter RB, Lonstein JE, Denis F, Johnson L. The surgical and medical perioperative complications of anterior spinal fusion surgery in the thoracic and lumbar spine in adults. A review of 1223 procedures. Spine 1995;20(14):1592–1599 Fessler RG, Sturgill M. Review: complications of surgery for thoracic disc disease. Surg Neurol 1998;49(6):609–618 Regan JJ, Mack MJ, Picetti GD III. A technical report on videoassisted thoracoscopy in thoracic spinal surgery. Preliminary description. Spine 1995;20(7):831–837 Fessler RG, Sekhar LN. Atlas of Neurosurgical Techniques: Spine and Peripheral Nerves. New York, NY: Thieme; 2006 Abbott KH, Retter RH. Protrusions of thoracic intervertebral disks. Neurology 1956;6(1):1–10 Arseni C, Nash F. Thoracic intervertebral disc protrusion: a clinical study. J Neurosurg 1960;17:418–430 Perot PL Jr, Munro DD. Transthoracic removal of midline thoracic disc protrusions causing spinal cord compression. J Neurosurg 1969;31(4):452–458 Patterson RH Jr, Arbit E. A surgical approach through the pedicle to protruded thoracic discs. J Neurosurg 1978;48(5):768–772
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approach for symptomatic thoracic disc herniation: initial multicenter clinical experience. J Neurosurg Spine 2012;16(3):264–279 Hulme A. The surgical approach to thoracic intervertebral disc protrusions. J Neurol Neurosurg Psychiatry 1960;23:133–137 Maiman DJ, Larson SJ, Luck E, El-Ghatit A. Lateral extracavitary approach to the spine for thoracic disc herniation: report of 23 cases. Neurosurgery 1984;14(2):178–182 Fessler RG, Dietze DD Jr, Millan MM, Peace D. Lateral parascapular extrapleural approach to the upper thoracic spine. J Neurosurg 1991;75(3):349–355 McCormick PC. Retropleural approach to the thoracic and thoracolumbar spine. Neurosurgery 1995;37(5):908–914 Chi JH, Dhall SS, Kanter AS, Mummaneni PV. The Mini-Open transpedicular thoracic discectomy: surgical technique and assessment. Neurosurg Focus 2008;25(2):E5 Uribe JS, Dakwar E, Cardona RF, Vale FL. Minimally invasive lateral retropleural thoracolumbar approach: cadaveric feasibility study and report of 4 clinical cases. Neurosurgery 2011;68(1, Suppl Operative):32–39; discussion 39 Dakwar E, Ahmadian A, Uribe JS. The anatomical relationship of the diaphragm to the thoracolumbar junction during the minimally invasive lateral extracoelomic (retropleural/retroperitoneal) approach. J Neurosurg Spine 2012;16(4):359–364 Kim M, Nolan P, Finkelstein JA. Evaluation of 11th rib extrapleuralretroperitoneal approach to the thoracolumbar junction. Technical note. J Neurosurg 2000;93(1, Suppl):168–174 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 Uribe JS, Arredondo N, Dakwar E, Vale FL. Defining the safe working zones using the minimally invasive lateral retroperitoneal transpsoas approach: an anatomical study. J Neurosurg Spine 2010;13(2):260–266 Dakwar E, Cardona RF, Smith DA, Uribe JS. Early outcomes and safety of the minimally invasive, lateral retroperitoneal transpsoas approach for adult degenerative scoliosis. Neurosurg Focus 2010; 28(3):E8 Berjano P, Balsano M, Buric J, Petruzzi M, Lamartina C. Direct lateral access lumbar and thoracolumbar fusion: preliminary results. Eur Spine J 2012;21(Suppl 1):S37–S4 Baaj AA, Dakwar E, Le TV, et al. Complications of the mini-open anterolateral approach to the thoracolumbar spine. J Clin Neurosci 2012;19(9):1265–1267
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Minimally Invasive Direct Lateral Approach to the Thoracolumbar Junction: Cadaveric Analysis and Case Illustrations David Straus1
Ippei Takagi1
John O’Toole1
1 Department of Neurological Surgery, Rush University Medical Center,
Chicago, Illinois, United States J Neurol Surg A 2015;76:56–62.
Abstract
Keywords
► direct lateral interbody fusion ► thoracolumbar junction ► minimally invasive spine surgery ► XLIF ► DLIF
Background Multiple surgical exposures to the thoracolumbar junction have been described. The minimally invasive direct lateral approach to the lumbar spine captures the advantages of anterolateral approaches while minimizing soft tissue destruction and perioperative morbidity. Utilizing this approach at the thoracolumbar junction presents unique anatomical challenges posed by the ribs, diaphragm, pleura, and lung. Methods We examine the use of a minimally invasive direct lateral approach to the thoracolumbar junction (T10–L2) through six cadaveric approaches and provide case examples of three patients. Results In six approaches with normal spinal alignment we were able to access all disc spaces in the thoracolumbar region. The L2–L3 disc was accessed below the 12th rib in 100% of spines; L1–L2 accessed through the T11–T12 intercostal space in 83% of spines; T12–L1 was accessed through the T11–T12 intercostal space in 67% of spines and through the T10–T11 intercostal space in 33% of spines; T11–T12 was accessed through the T10–T11 intercostal space in 83% of spines; finally, T10–T11 was accessed through the T10–T11 intercostal space in 67% of spines and through the T9–T10 intercostal space in 33% of spines. Discussion The minimally invasive direct lateral approach offers access to ventral pathology at the thoracolumbar junction. Familiarity with common anatomical structures encountered during this approach in the thoracolumbar junction enhances surgical planning and facilitates surgical exposure.
Introduction Surgical approaches to spinal pathologies at the thoracolumbar junction (T10–L2) may be classified as anterior, posterior, or posterolateral. Anterior approaches include the anterolateral thoracotomy, thoracoscopic thoracotomy, and the retropleural thoracotomy.1 These approaches offer extensive anterior exposure that is advantageous in treating pathologies located ventral to the thecal sac. However, thoracotomy increases the intraoperative physiologic stress, exposes the
received May 10, 2013 accepted after revision December 30, 2013 published online May 2, 2014
Address for correspondence David Straus, MD, Department of Neurological Surgery, Rush University Medical Center, 1725 W. Harrison St., Suite 855, Chicago, IL 60612, United States (e-mail: [email protected]).
patient to approach-related complications, and prolongs the postoperative hospital course.1–4 Moreover, transthoracic approaches require the assistance of an access surgeon, and thoracoscopic techniques require significant operator experience.5 Posterior approaches to the thoracic spine include laminectomy and transpedicular approaches.6 Thoracic laminectomy may be sufficient for decompression of some thoracic spinal lesions; however, ventral pathology is totally inaccessible via this approach due to the small size of the spinal canal in relation to the thoracic spinal cord.7–9 A
© 2015 Georg Thieme Verlag KG Stuttgart · New York
DOI http://dx.doi.org/ 10.1055/s-0034-1372431. ISSN 2193-6315.
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transpedicular approach enables increased access to ventral thoracic spinal pathology.10 However, it is still a posteriorbased approach whose access to ventral pathology is limited by the presence of the spinal cord and the trajectory of the surgical corridor.11 The costotransversectomy12 and lateral extracavitary13 approaches are posterolateral approaches that offer increasingly lateral trajectories and thus allow for direct access to ventral pathologies without entrance into the pleural cavity. The posterolateral approaches may be achieved without the aid of an access surgeon and offer surgical exposure of ventral lesions comparable with anterior-based approaches. The primary disadvantage of the posterolateral approaches is the need for extensive soft tissue dissection, resulting in increased operative time and blood loss.14–16 Posterolateral approaches, moreover, do not allow for anterolateral interbody device placement and fusion, which has become a powerful tool in both focal- and long-segment deformity correction. Recently, minimally invasive direct lateral approaches to the lumbar spine have become more widely utilized, offering comparable benefits of ventral spinal exposure but also minimizing the extent of soft tissue dissection required for the exposure.11,16–18 These retrocoelomic techniques are particularly appealing when approaching the thoracolumbar junction in that they may avoid entry into the pleural cavity and do not necessitate the assistance of an access surgeon. We have performed minimally invasive tubular approaches to the thoracolumbar spine using a direct lateral approach similar to that described by Uribe et al.17 Anatomical study of the specific access points, soft tissue structures, and body cavities related to this approach has not been described. Here we examine this approach in a cadaveric model and describe our experience using this approach.
Methods Cadaveric Dissection We performed a minimally invasive direct lateral approach to the thoracolumbar junction in six fresh cadavers (three placed in the right-side-up lateral decubitus position and three placed in the left-side-up lateral decubitus position). Minimally invasive surgery (MIS) tubular access to the thoracolumbar disc spaces was performed under fluoroscopic guidance. Soft tissue structures and body cavities were examined with the aid of a surgical microscope.
Surgical Technique The cadaver is placed in the lateral decubitus position and carefully secured to the operating table. The bed can be flexed at the kidney break between the iliac crest and the rib cage if necessary for lumbar exposure but is generally not necessary for thoracolumbar junction exposure. Fluoroscopy is used to confirm access to the levels of interest and to mark incisions. Multilevel procedures often require multiple incisions to provide the proper entry angles. Also for multilevel procedures we proceed in a caudal to rostral fashion, addressing the lowest level first and successively working upward. This is
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done particularly in cases involving L4–L5 but also facilitates the access to the thoracolumbar junction levels by initially having subdiaphragmatic access. Skin incision is made in line with the intercostal space. Although not necessary for surgical access, rib autograft may be harvested at this point. Resecting a 3- to 4-cm segment of rib will allow expanded access for the retractor. Dissection through the rostral terminations of the lateral abdominal wall musculature and/or intercostals muscles is performed with blunt spreading and finger dissection. The costal insertions of the diaphragm, when present, can similarly be bluntly spread apart without the need to completely strip the diaphragmatic attachments. Access to the disc space is through either the retroperitoneal or retropleural space, not unlike that described by Kim et al19 using open techniques. Once in the retrocoelomic space, further dissection is performed bluntly to displace the retroperitoneal contents, the diaphragm, or the lung anteriorly, following the course of the correlating proximal rib to the desired disc space or until the transverse process at L1 or L2 is palpable. Under fluoroscopic guidance, a guidewire is placed in the disc space and serial tissue dilators are used to place an expandable tubular retractor system (Globus Medical, Inc., Audubon, Pennsylvania, United States) over the lateral aspect of the disc space being treated as described previously.20 This may involve dilation through either the upper psoas muscle or through the diaphragmatic crus. Neurophysiologic stimulation of the dilators and retractor blades may be used to ensure avoidance of nerves within the upper lumbosacral plexus.21 The retractor is expanded as needed, and under loupe magnification and internally placed lighting, residual strands of psoas muscle or diaphragmatic crus are dissected off the disc space. A complete discectomy is performed, the disc space is prepared for arthrodesis, and appropriate size interbody grafts are impacted into place. Lateral instrumentation, if desired, can be placed and hemostasis achieved. Upon removal of the retractor, the soft tissues are inspected. The fascia of the abdominal wall/intercostals is then closed in an interrupted fashion. If the pleural space has been entered, the final fascial stitch is left untied and a red rubber catheter in placed into the pleural space. The opposite end is submerged underwater in a kidney basin. A Valsalva maneuver is performed to expel any intrathoracic air. During the Valsalva, the catheter is quickly removed and the final fascial suture tied, completing the closure of the thoracic cavity. Final closure of the wound is performed in layers. The patient can then be placed prone to perform any posterior decompression or instrumentation in either an open or percutaneous manner. An immediate postoperative upright chest radiograph is obtained in the recovery area to assess for pneumothorax.
Case Illustrations We review three patients who underwent lateral MIS tubular approaches to the thoracolumbar junction (defined here as procedures involving any segment in between T10 and L2). All procedures were performed between 2008 and2011 at Rush University Medical Center by the senior author (J.E.O.). Journal of Neurological Surgery—Part A
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Minimally Invasive Approach to the Thoracolumbar Junction
Minimally Invasive Approach to the Thoracolumbar Junction
Fig. 1 Patient positioning. True anteroposterior and lateral fluoroscopic views must be obtained to facilitate working angles once retractors are set in place. Disc spaces are marked in blue ink; T12 rib is marked by the longest line.
Results Cadaveric Study We performed six minimally invasive direct lateral approaches in cadaveric spines with relatively normal coronal alignment (20 degrees Cobb angle) at all levels in the thoracolumbar junction starting at the L2–L3 disc space and proceeding cranially to the T10–T11 disc space (►Figs. 1–5). Abdominal wall musculature was encountered in all specimens in incisions made below the T12 rib; intercostal musculature was encountered in all incisions between the T12 and T9 ribs. A 3to 4-cm segment of rib was accessible through the skin incision in all specimens for autograft if desired. Access to the L2–L3 disc space transversed the retroperitoneum in all spines, and the disc space was covered laterally by psoas muscle in all specimens. The L1–L2 disc space was accessed through the retroperitoneum in 67% of the spines and through the pleural cavity in 33% of the spines; psoas muscle covered the disc in 50%, in 17% diaphragmatic crus was present, and in 33% no muscular fibers covered the disc space. The T12–L1 disc space
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Fig. 3 In the figure on the left, the skin incision and subcutaneous dissection to the abdominal wall musculature is seen. On the right, blunt dissection through the abdominal wall or intercostals musculature to enter the retroperitoneal or retropleural space is shown. After entry into the retrocoelomic space is achieved, blunt finger dissection is performed down to the vertebral column.
was accessed through the retroperitoneal cavity 67% of the time and through the pleural cavity 33% of the time; 50% of spines had fibers of the diaphragmatic crus over the disc space, and 50% had no muscle covering the disc. The T11–T12 disc and the T10–T11 disc were accessed through the pleural space in all spines; no muscle was encountered over the disc space in any specimen at either level. A successful approach to all levels was achieved in all specimens without manipulation of the great vessels. Every disc space in the thoracolumbar junction was accessible in all spines from a direct lateral approach without the need for rib resection. L2–L3 disc was accessed below the 12th rib in 100% of spines; L1–L2 was accessed below the 12th rib in 17% of spines and through the T11–T12 intercostal space in 83% of spines; T12–L1 was accessed through the T11–T12 intercostal space in 67% of spines and through the T10–T11 intercostal space in 33% of spines; T11–T12 was accessed through the T11–T12 intercostal space in 17% of spines and through the T10–T11 intercostal space in 83% of spines; finally, T10–T11 was accessed through the T10–T11 intercostal space in 67% of spines and through the T9–T10 intercostal space in 33% of spines (►Table 1).
Case Examples
Fig. 2 Localization over the T11–T12 disc space to finalize location of skin incision. Journal of Neurological Surgery—Part A
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For illustration, we present three patients who underwent a direct lateral minimally invasive approach to the thoracolumbar junction using the surgical technique previously described (►Table 2). All patients had degenerative spinal pathology as an indication for their surgery. The intervertebral cages were all made of polyetheretherketone and were packed with autograft rib or rhBMP-2 (Medtronic, Memphis, Tennessee, United States) with β-tricalcium-phosphate. Supplemental instrumentation was used in all cases. In one case performed for a single-level adjacent segment degeneration, a lateral plating system was used, and in the other two cases performed for adult degenerative scoliosis, correction pedicle screw instrumentation was used. Placement of supplemental posterior fixation was done in a staged manner on a different
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Fig. 4 (A) Insertion of initial dilator for localization. (B) Serial dilation over disc space on lateral fluoroscopy. (C) Anteroposterior (AP) fluoroscopy confirming appropriate alignment with disc space. (D) Final placement of retractor on AP fluoroscopy. (E) Final placement of retractor on lateral fluoroscopy.
day in these two patients. No patients required a chest tube at the end of the operation. Two patients had small pneumothoraces identified on postoperative chest X-ray; both were asymptomatic and neither required more than nasal cannula oxygen for management.
Discussion
Fig. 5 The view through the retractor is seen in the figure on the left. Note that the soft tissue covering disc space may contain psoas muscle, diaphragmatic crus, or no muscle. This soft tissue is dissected off the disc space to expose the lateral annulus. The final exposure of disc space after soft tissue removal and discectomy is shown in the figure on the right.
Minimally invasive direct lateral approaches to the thoracolumbar junction are a relatively new approach that offer a promising alternative to more invasive open posterolateral and anterior approaches while preserving many of their benefits.11,17,18,21–23 In our experience, this approach has proven useful in the management of degenerative conditions and thoracolumbar scoliosis.22 Its application to neoplastic, Journal of Neurological Surgery—Part A
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Minimally Invasive Approach to the Thoracolumbar Junction
Minimally Invasive Approach to the Thoracolumbar Junction
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Table 1 Results of cadaveric thoracolumbar direct lateral approaches L2–3, %
L1–L2, %
T12–L1, %
T11–T12, %
T10–T/11, %
Body cavity (n ¼ 6) Retroperitoneum
100
67
67
0
0
Retropleural
0
33
33
100
100
Psoas
100
50
0
0
0
Crus
0
17
50
0
0
Neither
0
33
50
100
100
Below 12th rib
100
17
0
0
0
T11–T12 intercostal
0
83
67
0
0
T10–T11 intercostal
0
0
33
100
67
Deep muscle (n ¼ 6)
Access point (n ¼ 6)
T9–T10 intercostal
0
0
0
0
33
Unable to access
0
0
0
0
0
traumatic, and infectious pathologies has also been reported.17,23,24 Exposure is adequate to perform corpectomies and place interbody cages.17 Access to the lateral aspect of the disc space enables direct visualization of the ventral thecal sac without spinal cord retraction, resulting in safer surgical decompression of ventral pathologies (e.g., retropulsed bone, epidural abscess, epidural tumor, herniated disc, and osteophytes). The results of our cadaveric studies show that the retrocoelomic approach used in direct lateral access to the thoracolumbar junction transverses the retroperitoneum in levels below L2 and transverses the retropleural space in levels above T12. The L1–L2 interspace and the T12–L1 interspace thus represent a transitional region, and approach to these levels may involve accessing either or both the retroperitoneum and the retropleural space. The psoas muscle thins toward its superior attachments at L1. It is consistently encountered during the direct lateral approach at levels below L1–L2, inconsistent at T12–L1, and not present at levels above T12. The fibers of the diaphragmatic crus are most commonly encountered at T12–L1 and occasionally found at L1–L2. In our experience, it has not been necessary to detach the diaphragm from its connections to the thoracolumbar junction at the diaphragmatic crus, as was previously described.18 The diaphragmatic crus was encountered only when accessing L1–L2 or T12–L1 in our cadaveric series, and the muscle fibers were adequately spread with the tubular dilators and retractors to expose the disc space. Similarly, we have only encountered postoperative pneumothoraces after accessing levels above L1 (where the diaphragmatic crus inserts). When the pleura is encountered during the initial approach, a retropleural dissection is attempted when possible using finger or dilator dissection. However, even if the parietal pleural is violated, chest tube insertion is Journal of Neurological Surgery—Part A
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not necessary. Access to the T12–L1 and L1–L2 spaces is most typically achieved through the 11/12th intercostal space. Access to the disc space and body is adequate using the intercostal space. Partial rib resection, however, often may be used for autograft material. Specific surgical considerations vary across the different levels in the thoracolumbar junction. At the upper lumbar levels, the lumbar plexus remains an important consideration. The roots of the plexus run in the dorsal-most quarter of the vertebral body (“zone IV”), with the important exception of the genitofemoral nerve, which runs through the psoas in the anterior half of the L2–L3 interspace (“zone II”). Thus at L2–L3, special attention must be paid to the root dorsally and to the genitofemoral nerve ventrally. At L1–L2 the roots and divisions (both ilioinguinal and iliohypogastric nerves) remain important considerations in addition to considering the diaphragmatic attachments and transitional nature of this level. At T12–L1 the diaphragm and its insertions remain an important consideration. At T11–T12 and T10–T11, the approach will almost certainly be retropleural. Care should be taken to avoid pleural tears where possible, and attention must be paid to minimizing the risk/consequences of postoperative pneumothorax. Our experience with the minimally invasive direct lateral approach has primarily been for the purpose of performing an interbody fusion and anterior column augmentation for degenerative scoliosis correction. In general, our typical approach is on the concavity of scoliotic curves to (1) enhance positional reduction of the curve with flexing of the operating table, (2) increase the height of the most collapsed side of the disc space, (3) allow access to L4–L5 disc, which is typically inaccessible from the convexity of a lumbar coronal curve, and (4) allow exposure of a greater number of disc spaces through a single interspace. Combined thoracic and lumbar
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Table 2 Case description of thoracolumbar direct lateral fusion Patient
1
2
3
Age, y
65
65
62
Sex
F
F
M
Diagnosis
Lumbar scoliosis
Thoracolumbar scoliosis, lumbar stenosis
T12–L1 Adjacent level disease
Prior same-level surgery
No
No
Yes
Procedure
T12–L5 DLIF, staged posterior L5–S1 TLIF, and percutaneous T12–pelvis screws
T11–L5 DLIF, T9–T11 MIS facet fusion, staged T9–L5 percutaneous screws, L3–L5 MIS laminectomies
T12–L1 DLIF with lateral plate fixation
Supplemental instrumentation
Pedicle screws, rods
Pedicle screws, rods
Lateral plate fixation
Staged
Yes
Yes
No
DLIF levels treated
5
6
1
Demographics
Thoracolumbar DLIF levels treated
2
3
1
Rib resection, autograft
Yes
Yes
No
OR time, min
300
415
220
EBL
150
500
150
Pneumothorax
Yes
Yes
No
Chest tube needed
No
No
No
Postoperative
Hospital LOS, d
8
9
7
Complications
Posterior wound infection, osteoporotic screw pullout
None
None
Abbreviations: DLIF, direct lateral interbody fusion; EBL, estimated blood loss; LOS, length of stay; MIS, minimally invasive surgery; OR, operating room; TLIF, transforaminal lumbar interbody fusion.
curves in multilevel cases require careful preoperative planning to ensure ease of access to all desired levels. In line with the goal of appropriate spinal reconstruction, all patients in our series received supplemental fixation. In patients with adult degenerative scoliosis, our current practice is to supplement the lateral interbody grafts with posterior instrumentation (percutaneous or open depending on the needs for deformity correction). Lateral plating offers a suitable and readily available option through this approach as well; its use was previously described in the setting of herniated discs, trauma, and tumors.24 Supplemental instrumentation in other settings may not be mandatory, especially for certain single-level cases such as thoracic herniated discs.11 The anatomical relationships presented in this article, previously unreported in the literature, should prove valuable in surgical planning, approach trajectories, and complication avoidance. Persistent surgical pain at the direct lateral site has not been noted in our experience. Previously reported complications of the minimally invasive direct lateral approach to the thoracolumbar junction include unintended durotomy, intercostal neuralgia, venous thromboembolism, hemothorax, pleural effusion, hardware failure, and wound infection.24
Incidence of surgical complications was 12.5% in a series of 80 patients who underwent this approach for a variety of different pathologies. We have not encountered any clinically significant pneumothoraces, although asymptomatic pneumothoraces were present in two of our cases. Evacuation of air via the red rubber catheter technique described earlier in cases in which the pleural space is entered may help maintain a low incidence of symptomatic pneumothorax by using this surgical approach. There were no complications related to the direct lateral technique itself. Weaknesses of this study include the relatively small number of cases and cadavers analyzed. Cadaveric specimens with more severe coronal scoliosis were not available and could influence the anatomical relationships described here. Clearly, such pathology would need to be accounted for when planning surgical approaches. The purpose of this report was to describe the anatomical characteristics and general feasibility of the minimally invasive direct lateral approach to the thoracolumbar junction. Although real-time fluoroscopic localization and incisional planning remain critical to this surgical technique, we hope that the anatomical data may enhance surgical planning, especially in the preoperative setting. Journal of Neurological Surgery—Part A
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Operative
Minimally Invasive Approach to the Thoracolumbar Junction
Conclusion
11 Uribe JS, Smith WD, Pimenta L, et al. Minimally invasive lateral
Minimally invasive direct lateral access to the thoracolumbar junction is a relatively new surgical approach. It offers many of the advantages of previously described open anterolateral approaches but with a significantly reduced extent of soft tissue dissection and no need for thoracostomy tube placement. This has allowed for reduced approach-related pain and much earlier postoperative mobilization for these patients. This technique may be applied to a wide spectrum of pathologies involving the ventral spine at the thoracolumbar junction. Facility with minimally invasive techniques is necessary to safely and successfully use this approach. In the small series of patients presented here, this minimally invasive direct lateral approach to the thoracolumbar junction appears safe and effective.
12 13
14
15 16
17
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