Thoracolumbar Burst Fractures: Can Thoracolumbar Burst Fractures Be Effectively Managed Using Minimally Invasive Surgery Techniques?

16 Thoracolumbar Burst Fractures: Can Thoracolumbar Burst Fractures Be Effectively Managed Using Minimally Invasive Surgery Techniques?

MIS: Gurpreet S. Gandhoke, David O. Okonkwo, and Adam S. Kanter
Open: Amandeep Bhalla and Kristen E. Radcliff

16.1 Introduction

Indications for surgical management of acute thoracolumbar burst fractures are well described and include decompression of neural elements, restoration of spinal alignment, and promotion of arthrodesis.1,2,3,4 Patients requiring surgery for thoracolumbar burst fractures may be treated via an anterior approach, posterior approach, or combined anterior–posterior approach. The goals of surgery are neural decompression, stabilization, and correction of an associated deformity when present. Anterior instrumentation has been shown to produce equivalent arthrodesis and correction of kyphotic deformity compared to posterior instrumentation while allowing for direct visualization of the spinal canal and, theoretically, a superior decompression.5 However, traditional anterior approaches to the thoracolumbar spine carry significant morbidity, including pneumothorax, aortic injury, disruption of the lumbar plexus, retrograde ejaculation, and development of abdominal or diaphragmatic hernia.6

To minimize exposure-related morbidity, a number of anterolateral laparoscopic and thoracoscopic approaches for instrumentation at the thoracolumbar junction have been attempted.7 The minimally invasive extreme lateral approach is a technique that has been previously described for the treatment of spine pathology including degenerative and scoliotic lumbar disease.8 Its use in trauma, particularly in the treatment of burst fractures, is more limited in the literature. The thoracic spine from T6–T7 level and up to the L4–L5 disc space is accessible to treat pathology utilizing this minimally invasive approach.

16.2 Advantages of Minimally Invasive Surgery

To access the anterior thoracolumbar spine from T12–L2, the conventional open approach consists of a lateral incision over the ribs and dissection of muscular layers until exposure of the peritoneum is achieved, followed by mobilization of the diaphragm and retraction of lung parenchyma to access the retroperitoneal space.9,10 This approach commonly requires insertion of a chest tube until the pleural effusion resulting from diaphragmatic dissection has drained. Complications specific to anterior spine surgery include aortic laceration (0.08%), pneumothorax (1.8%), and post-thoracotomy pain syndrome persisting for greater than 6 months (9%).6

Anterior approaches for vertebrectomy and arthrodesis via laparoscopic and video-assisted thoracoscopic techniques have been well described in the literature.7,11,12,13,14 These approaches to the anterior thoracolumbar spine have been shown to result in shorter hospitalizations when compared to open approaches.12,15 Disadvantages of endoscopic approaches include the requirement for single lung intubation, a steep and long learning curve, representation of three-dimensional anatomy in two dimensions, extensive and expensive instrumentation, extended operative times, relative inability to tackle inadvertent complications without having to open exposure, and the difficulty in placement of large reconstructive anterior instrumentation.

The lateral transpsoas approach has been previously described for the treatment of degenerative thoracolumbar disease.16 It is a minimally invasive approach that utilizes sequential dilation with electromyographic (EMG) neuromonitoring to place an expandable tubular retractor. It provides the additional benefit of minimizing dissection of the great vessels and the sympathetic plexus, thus reducing the risk of vascular injury and retrograde ejaculation.17 When the approach is retro pleural, there is no violation of the pleural or the peritoneal cavity posing less risk of complications associated with open thoracotomy, including the development of a cerebrospinal pleural fistula.18 The amount of kyphosis correction achieved is equivalent to that achieved with open anterior procedures.14,19 Additional benefits include the ability of the approach to be performed without rib resection and lung deflation. This minimally invasive lateral approach to the thoracic spine offers a very good alternative to an open thoracotomy or a video-assisted thoracoscopic corpectomy. Through a small corridor, corpectomy can be performed at most levels from T6 to L4, allowing for decompression, correction of deformity, and fusion.

16.3 Advantages of Open Surgery

Indications for an open anterior approach include burst fracture with incomplete paraplegia, retropulsed fragment with significant canal compromise, significant kyphotic deformity (> 30 degrees), delay from injury rendering ligamentotaxis ineffective, and traumatic disc herniation with flexion–distraction injury.20 The anterior approach aids in reconstruction of the anterior column with a load-sharing construct, which reduces posterior cantilever loads and the risk of late kyphotic failure. Short segment anterior or posterior fixation may be employed to neutralize the construct and impart additional stability. Anterior-only procedures have the distinct advantage of limiting the levels of fusion necessary. A circumferential fusion is necessary, however, to stabilize three-column spinal injuries in the setting of symptomatic canal occlusion. If the posterior tension band has failed, supplemental posterior stabilization is also recommended.

The anterior approach to the thoracolumbar spine affords the most direct visualization of the spinal cord via corpectomy, which optimizes ability to achieve complete neural decompression. Iatrogenic neurologic injury is not reported in major series, likely because of the safety resulting from direct anterior visualization of the thecal sac.20 The adequacy of the anterior decompression is of chief importance, and compromise of the surgical exposure through minimally invasive techniques may result in residual compression and subsequent irreversible neurologic injury. The anterior approach is superior to the transpsoas minimally invasive technique in surgical exposure, as the latter was designed to access the midportion of the disc space. With the lateral approach, it is difficult to gain access to the retropulsed fragment in the spinal canal from the lateral aspect of the midportion of the disc space without significant traction across, which risks stretch injury to the lumbar plexus.

Bleeding is a significant risk in the setting of acute fracture, and a very common complication in the surgical management of thoracolumbar burst fractures. With improved visualization, the anterior approach aids in better control of bleeding. The surgical path through the psoas muscle may cause additional bleeding, and the very nature of minimally invasive surgery (MIS) undermines the adequacy of exposure necessary to control it. The open anterior approach also improves visualization both cephalad and caudad to the injured vertebral body, so that adequate discectomies and end plate preparation can be performed.

The posterior transpedicular approach offers distinct advantages including decreased operating time, blood loss, and morbidity.21,22 The nature of the approach allows for repair of posterior dural tears.23 Posterior instrumentation assists in applying distractive forces for decompression and graft passage, as well as compressive forces to aid in stabilization.24 The posterior approach also affords for considerable deformity correction of the kyphosis and collapse inherent in thoracolumbar burst fractures. Posterior approach also allows for additional bone grafting surface across the posterior elements bilaterally. The open approach also allows repair of traumatic durotomies and decompression of nerve root fragments entrapped in the bony fragments. The posterior approach also has fewer complications of hemopneumothorax, abdominal distension, and ileus.

16.4 Case Illustration

A 17-year-old woman was the restrained driver in a high-speed motor vehicle collision. She presented with severe low back pain but remained neurologically intact (American Spinal Injury Association impairment score E [ASIA-E]). Computed tomography (CT) scan demonstrated an L1 burst fracture with 70% loss of height of the vertebral body and retropulsion-causing canal narrowing of 60%, with associated right L1 pedicle and laminar fractures (images Fig. 16.1). Magnetic resonance imaging (MRI; images Fig. 16.1a, b, e) demonstrated a disrupted posterior ligamentous complex, for a TLICS25 (Thoracolumbar Injury Classification and Severity) score of 5 (images Fig. 16.1c, f).

16.5 Surgical Technique in Minimally Invasive Surgery

The major anatomic landmarks to consider when preparing for this surgery are the ribs, lung, diaphragm, aorta, and the spinal curvature. The diaphragm will be in the surgical access path when accessing the spine for the levels from T10 to L1. The diaphragmatic tendinous attachments may be encountered down to the L3 vertebra.

When operating in the pleural cavity with the minimally invasive retractor system, double-lumen intubation and lung deflation is not required. We approach the thoracic spine with retractor placement and expansion in between the ribs, without its resection, thus gaining adequate access to the pleural cavity. Care should be taken to avoid injury to the neurovascular bundle that lies under the inferior aspect of each rib.

Preoperative MRI should be carefully evaluated to examine for the position of the aorta, the sympathetic plexus, and its relation to the psoas muscle and the spinal curvature, which may place the aorta in the path of the lateral surgical corridor.

16.5.1 Position

After induction of general anesthesia, the patient is placed in the lateral decubitus position with the left side up. We prefer to use the left side to access the spine given the aorta and iliac arteries are more pliable and forgiving than the vena cava system and more likely to withstand surgical handling without injury. In patients with scoliosis, the aorta may lie on the lateral aspect of the vertebral bodies and thus would require access from the opposite (right) side.

The patient is positioned on the table such that the table break lies at the midpoint of the iliac crest and the greater trochanter. All pressure points are padded and the patient is secured to the table with tape at the following locations:

• Over the iliac crest below the table break.

• Over the thoracic region above the region of the surgical exposure.

• From the iliac crest inferiorly securing to the foot of the table.

The bed is slightly flexed to expand the costo-pelvic interval and the intercostals. The table (not the C arm) is carefully adjusted to obtain true anteroposterior (AP; the spinous processes should be midline and the pedicles should be equidistant from the spinous processes) and lateral images (crisp end plates should be visualized).

Fluoroscopy is then utilized to mark out the fracture site on the skin, identifying the superior aspect of the disc space above and the inferior aspect of the disc space below the fractured vertebrae.

When operating within the pleural cavity (to access the spinal levels from the L1 body and above), the approach is typically in between the ribs. The incision is again marked utilizing fluoroscopy and will run parallel and in between the ribs, along the superior aspect of the inferior rib, to avoid injury to the neurovascular bundle.

A chlorhexidine wipe and ChloraPrep solution is used to sterilize the surgical site.

16.5.2 Anatomic Considerations during Access to the Retroperitoneum

The main paired abdominal muscles include the external oblique muscles, internal oblique muscles, transversus abdominis muscles, and their respective aponeuroses, which provide core strength and protection to the abdominal wall viscera. The transversalis fascia is one of the main components that maintain structural integrity of the retroperitoneal space. A 4-cm transverse incision is made along the lateral flank at the mid-line level of the index vertebral body. The incision should be made parallel to the direction of the fibers of the external oblique to minimize the possibility of injury to the motor nerves supplying them. This prevents abdominal wall pseudo-hernia formation from loss of tone to these abdominal wall muscles. Blunt dissection with anterior sweeping movements of the retroperitoneal contents is then performed to enable palpation of the psoas muscle and the transverse process of the index vertebra.

16.5.3 Thoracic Access

We use the rib-spreading technique to dissect down to the ribs, through the intercostal musculature, down to the pleura. Pleural access is gained by dissection along the superior aspect of the lowest rib. Once within the pleural cavity, finger dissection is utilized to gently palpate the lung, and the initial dilator is then passed into the pleural cavity in a dorsal trajectory following the curvature of the rib until landing at the intersection of the rib head and spine, as confirmed with fluoroscopy. The dilator is then gently positioned in the center of the vertebral body, taking care not to injure the segmental artery. The remaining dilators are then passed over the initial dilator down to the spine, followed by the final retractor system.

16.5.4 Retroperitoneal Access

The T12–L1 level, in our experience, can be accessed both through the transpleural route and through the diaphragm in the retroperitoneal space. The levels below L1 down to the L5 superior end plate require a retroperitoneal access route. A 4-cm flank incision is performed as above to gain access to the retroperitoneal space via blunt finger dissection, carefully sweeping the abdominal contents ventrally as each layer of the lateral musculature and fascia are traversed. Loss of resistance from muscles (external oblique, internal oblique, transversalis muscle and fascia transversalis) indicates that the retroperitoneal space has been reached.

Using a blunt-tipped snap to spread the fibers of the oblique muscles under vision ensures the security of the iliohypogastric and ilioinguinal nerves and thus preventing a lumbar hernia from loss of tone in the muscles of the anterior abdominal wall.

Once the tip of the transverse process is encountered, the finger is directed medially to feel for the psoas muscle, gently sweeping anteriorly and away any fascial adhesions. The first dilator is then passed with the finger as its guide through the oblique muscle layers down to the retroperitoneal space and docked on the psoas muscle in the center of the vertebral body.

16.5.5 Electrophysiological Monitoring

The lumbar plexus tends to lie in the posterior one-third of the psoas muscle. Electrophysiological monitoring is utilized in all cases to enable safe passage of the dilators and retractor system to minimize retraction and damage to these motor nerves. We utilize the Neurovision neuromonitoring, which continuously searches for the stimulus threshold that elicits an EMG response and reports this threshold both audibly and visually. As the stimulus source (the dilators and the retractor system also act as electrodes and are insulated to minimize current shunting) moves closer to the nerve, less stimulus intensity is required to elicit a response, resulting in a lower threshold, which provides an indication of the relative proximity of the dilator to the nerves.

We consider threshold values of 10 mA and greater as a marker of safe distance from the nerves.

Lower thresholds of stimulation of the nerve should be posterior to the working operative field, confirming that the lumbar plexus is behind the retractor and not pushed anteriorly.

16.5.6 Procedure

We utilize the MaXcess retractor system (NuVasive, Inc., San Diego, CA), advancing it over the dilators and minimally expanding it to reveal the inferior aspect of the rostral vertebral body and the superior aspect of the caudal vertebral body adjacent to the fractured level.

Minimal retraction is key to prevent stretch-related injury and weakness of the psoas muscle. We utilize two-click dilation in the AP plane and six-retractor-click dilation in the craniocaudad plane

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Jan 15, 2020 | Posted by in ORTHOPEDIC | Comments Off on Thoracolumbar Burst Fractures: Can Thoracolumbar Burst Fractures Be Effectively Managed Using Minimally Invasive Surgery Techniques?

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