Thoracic and Thoracolumbar Spine Fractures with Ventral Mass Lesion: Ventral versus Dorsal Operation

Management of thoracic and thoracolumbar spine fractures continues to evolve, but remains controversial in regard to nonoperative treatment, the role of surgery, and what type of surgery is best. Nonoperative management has been shown to be effective if spinal canal compromise is minimal, dorsal elements are intact, and no neurologic deficits are present.¹ More severe fractures also can be effectively treated nonoperatively.² Patients with fractures and loss of more than 50% of vertebral body height, spinal canal stenosis greater than 50%, major kyphotic deformity in excess of the Cobb angle of 20 degrees, neurologic deficit (including sphincter dysfunction), intractable pain, and instability despite bedrest or sufficient bracing are generally considered candidates for surgery.

Dorsal decompression and stabilization techniques remain the most commonly used procedures for thoracic and thoracolumbar fractures. Ventral decompression and stabilization can be accomplished with a dorsal approach via either a unilateral transpedicular costotransversectomy or a lateral extracavitary approach.^3–7 A bilateral microsurgical transpedicular approach without costotransversectomy also can be used. Visualization of the ventral dural surface and contralateral nerve root during removal of retropulsed bone fragments can be limited, however. Application of a ventral plating system can be difficult, if not impossible. Insertion of an anterior vertebral body prosthesis can be accomplished by unilateral transverse process resection and lateral rib transection for release to allow extrapleural lung retraction during cage placement. In addition, long constructs of dorsal instrumentation with pedicle screw implant two levels above and two levels below the fracture site often are necessary after extensive corpectomy to ensure stability. Percutaneous pedicle screw insertion is now possible. This limits the extent of posterior surgical dissection necessary for spine exposure. Placement of an expandable cage as a vertebral body prosthesis after corpectomy is now feasible with appropriate implant instrumentation to accomplish distraction, restore alignment, and maintain anterior column structural integrity. The complication rate with the lateral extracavitary approach, which allows for the most extensive ventral canal decompression, can be significant—even for experienced spine surgeons.⁸

Indirect decompression with distraction using pedicle screws can result in a satisfactory ventral decompression via ligamentotaxis. However, canal clearance of large retropulsed fragments can be incomplete, and anterior middle column reconstruction is limited. Moreover, the load-bearing capacity of the injured vertebral body may not be sufficient.^9,10 The addition of transpedicular interbody grafting to posterior stabilization has not been shown to uniformly prevent loss of initial correction.^11,12

The role of ventral thoracotomy approaches for decompression and stabilization in the treatment of thoracolumbar spine fractures has significantly advanced during the last 20 years,^13–21 primarily due to the refinement of surgical approaches and the use of minimal access spine surgery, including thoracoscopy.^22–24 Improved CT imaging permits more detailed analysis of fractures and selection of the optimum spinal approach. The goals of ventral surgeries are decompression of neural elements under direct vision as well as restoration of spinal alignment and stability without immobilizing intact motion segments. Ventral surgery can be accomplished either as a single-stage, stand-alone procedure with a plate or as combined posterior-anterior surgery in conjunction with a posterior short-segment pedicle screw fixation.^{16,19–21,23}

Biomechanical studies indicate that ventral instrumentation systems, in combination with a ventral strut graft, restore spinal stability after vertebral body resection. In a porcine corpectomy model, ventral strut grafting with instrumentation was 15% stiffer during axial loading than was the intact spine.²⁵ In comparison, dorsal instrumentation alone was 76% less stiff than the intact spine. Gurr et al.²⁶ studied the ventrally placed Kaneda vertebral body prosthesis device and compared it with pedicle screw systems in a bovine model. Equivalent biomechanical stiffness after corpectomy and reconstruction with the Kaneda system over three spinal segments was achieved only if dorsal instrumentation spanned at least five levels.²⁶ Thus, it would be necessary to include several healthy, asymptomatic spinal segments in such a fusion and stabilization procedure.

Because many thoracolumbar spine fractures have significant involvement of both the anterior and middle column vertebral structures, spine surgeons have always found the ventral approach for decompression and stabilization challenging. In burst fractures, the epidural compression most commonly is ventral to the dura mater, making ventral surgery the most direct approach for decompression.²⁰ However, in the past, because of the lack of appropriate ventral instrumentation and difficult, unfamiliar ventral exposures (i.e., thoracotomy or thoracolumbar exposures), the ventral route was considered less desirable by many spine surgeons. Recent advances in spinal instrumentation and refinement of ventral surgical approaches have changed this attitude. The indications for single-stage ventral decompression and stabilization have continued to expand, and several clinical studies have shown excellent results.^16,19,20 The largest series, by Kaneda et al.,¹⁶ included 150 patients with thoracolumbar burst fractures treated with ventral decompression and stabilization. All of the patients had neurologic deficits after their injury. The mean follow-up was 8 years (range, 5–12 years), and the fusion rate was 93%. Only 10 patients developed nonunion, which was managed with secondary dorsal instrumentation and fusion. Postoperative spinal canal stenosis, measured by CT, ranged from 0% to 8% (mean, 2%). Neurologic function improved by at least one Frankel grade in 95% of patients, bladder dysfunction completely resolved in 72% of patients, and 86% of patients returned to work without restriction. This study demonstrates that a ventral approach alone can yield excellent results in restoration of neurologic functions and spinal stability.

More recently, Zdeblick et al.¹⁹ reviewed a 7-year experience with ventral spinal decompression and fusion at the University of Wisconsin. Surgical indications were incomplete neurologic deficit, segmental kyphotic deformity greater than 25 degrees, and significant comminution of the vertebral body/pedicle complex. Thirty-five patients with thoracolumbar burst fractures were treated with ventral surgery, strut grafting, and fixation using the Z plate. Thirty-three patients were treated only with anterolateral instrumentation. The mean surgical time was 295 minutes, and the mean estimated blood loss was 1750 mL, with a mean hospital stay of 9 days. All patients were followed for a minimum of 2 years with a mean follow-up of 27 months. Forty-six percent (16 out of 35 patients) presented with a neurologic deficit, and all 16 of those patients demonstrated at least one Frankel grade of improvement after surgery. Twenty-nine of 30 patients who underwent ventral spinal decompression and fusion demonstrated radiographic healing, and 5 patients were lost to follow-up. One patient required a subsequent posterior fusion for an increase in kyphotic deformity. There were no instances of hardware failure, and the sagittal alignment was improved from a mean preoperative kyphosis of 18 degrees to a mean of 6 degrees on final follow-up.

The results of both of these studies illustrate that stand-alone anterior decompression, fusion, and stabilization is an effective treatment with excellent clinical and radiographic results. However, blood loss can be high in these procedures, illustrating the increased morbidity of thoracotomy and thoracolumbar approaches. In addition, all patients in both series were required to wear a thoracolumbar orthosis after surgery. For instance, in the study by McDonough et al.,¹⁹ a thoracolumbar sacral orthosis was worn whenever the patient was out of bed for a minimum of 3 months.

Because of the large incisions required for thoracotomy and thoracoabdominal approaches and their associated morbidities, and because of the difficulties of performing ventral spinal surgeries in the acute setting, Beisse et al.^27–29 at the Trauma Center Murnau in Germany developed a minimally invasive thoracoscopic approach for the management of burst fractures using anterior column reconstruction and decompression (Fig. 217-1). The technique uses four small access portals along with a main working portal, which measures approximately 3 cm in diameter. Thoracic and thoracolumbar spine fractures from T4 through L1 can be treated using this technique. Between 1996 and 2004, these authors performed more than 800 endoscopic operations for spine fractures. To refine the technique, they developed an anterior plating system that can be placed thoracoscopically. Publications indicate that the rate of conversion to open surgery is less than 1%. There have been only four cases of hardware failure using the minimally invasive anterior implant, and no cases of misplaced hardware have been reported. Approach-related complications have been minimal (approximately 5.4%) in their series. In separate publications, the authors evaluated the results of the anterior decompression and illustrated the effectiveness of thoracoscopic spinal canal decompression for fractures.²⁴ Using the method of Bradford and McBride,⁹ the average preoperative narrowing of the spinal canal reported by Beisse et al.²⁴