The treatment of thoracolumbar burst fractures continues to evolve with technological advances. The goals of surgical management, however, remain unchanged: decompression, realignment, and stabilization with a minimum number of motion segments disrupted. As such, the use of anterior instrumentation is a valuable surgical option, with refinements of approach techniques also increasing management options. Choosing the best operative approach is determined by the patient’s medical condition, the nature and location of the fracture, and the surgeon’s preference. This chapter reviews the anterior approach to decompression and reconstruction of thoracolumbar burst fractures.

33.2 Patient Selection

Debates persist regarding the indications for nonoperative versus operative treatment, with initial nonoperative management becoming more common. As a general rule only, nonoperative treatment must be considered the primary management method for thoracolumbar fractures in the absence of a neurologic injury or clear evidence of instability. ¹ Conversely, most spine surgeons will agree that progressive neurologic deterioration with substantial canal compromise is an indication for surgical intervention. The thoracolumbar injury classification and severity score (TLICS) uses fracture morphology, integrity of the posterior ligamentous complex, and neurologic status of the patient to generate an injury score. TLICS scores < 4 are directed to nonoperative treatment, whereas scores > 4 are in need of surgical correction. TLICS scores of 4 fall into a gray zone where operative or nonoperative management may be correct. ² Many spine surgeons argue for surgical intervention when kyphotic deformity is greater than 30 degrees, ³ although several advocate operating on deformities much smaller. ⁴ Progressive kyphotic deformity can also occur in patients treated nonoperatively, resulting in the need for surgical correction. ⁵ In the absence of neurologic compromise or significant or progressive kyphotic deformity, another indication for delayed operative management is intractable or debilitating pain. Further controversy continues over the optimal surgical approach (i.e., anterior, posterior, or combined). The benefits of the anterior approach for spinal decompression and reconstruction are related to fracture pattern and neurologic status. This approach allows for increased distractive force, removal of damaged disks, and canal decompression and potentially avoids iliac crest harvesting. ⁶ The anterior approach also theoretically permits fusion of a minimum number of segments, which preserves maximal residual motion. Furthermore, evidence has shown that the anterior approach is associated with fewer complications and subsequent additional surgeries. ⁵

The main indications for primary anterior reconstruction include acute fractures with incomplete neurologic deficits that need decompression, fractures in which the anterior and middle columns are so severely comminuted that a posterior procedure alone would have inadequate results, and progressive kyphosis where a posterior procedure alone may lead to anterior column collapse.

33.3 Preoperative Preparation

33.3.1 Surgical Planning

Preoperative surgical planning is essential to a successful operative intervention. Plain film radiographs provide the Cobb angle measurement, typically calculated from the superior end plate of the vertebral body above the fracture to the inferior end plate of the vertebral body below the fracture. Flexion and extension radiographs or hyperextension lateral radiographs over a bolster can also be used to assess fracture stability and help predict how much deformity correction should be expected; however, these are often not feasible in the acute setting. Fine-cut (1.0–1.5 mm) computed tomographic scans are requested to delineate the extent and nature of the bone involvement. The information can also be transferred to a three-dimensional (3-D) workstation for detailed preoperative planning, which may include calculating the size of the implants and fixation devices that may be required. Magnetic resonance imaging may also be helpful in identifying neural compression, disk herniation, extent of disease, and posterior column disruption.

33.3.2 Anesthetic Techniques

Anesthesia concerns include a wide range of issues. Preoperative pain control measures may include nerve root blocks and epidural catheter placement. Depending on the level of the fracture, planning for a double-lumen endotracheal tube for single-lung ventilation should be considered. In light of potential spinal cord compromise, normotensive and normovolemia anesthesia should be maintained at all times throughout the case. An arterial line should be used for real-time blood pressure management, and during the kyphotic correction maneuver, mild hypertension should be initiated if tolerated by the patient. Concerns for large-vessel injury mandate central venous access before the start of the case.

33.4 Operative Procedure

33.4.1 Positioning

Proper positioning of the patient is essential when performing an anterior approach to the thoracolumbar spine and is even more critical when implanting internal fixation devices. The patient is positioned in the true lateral decubitus position on a radiolucent table; we use the Jackson table (OSI, Union City, California). This position enables the surgeon to orient to the spinal canal, as well as to more directly account for angle of insertion for the vertebral screw(s). As a general rule, T2–6 fractures require a right thoracotomy (avoids the heart), whereas T7–L3, L4 fractures are best treated with a left thoracotomy/thoracoabdominal approach (avoids the liver). A left-sided approach also places the aorta closer than the vena cava to the surgeon. This is often preferred because mobilizing and manipulating the aorta is safer than manipulating the vena cava. In addition, arterial vessel repair is easier than venous repair.

The patient is positioned on an inflatable beanbag, and separate hand towels are taped across the shoulder and greater trochanter to maintain position. In addition, an axillary roll should be placed for positioning comfort and protection of the brachial plexus and arterial flow to the dependent (down) upper extremity. The ipsilateral upper extremity is placed on a padded arm holder to prevent a stretch injury. We also routinely use neuromonitoring of the upper extremities to detect early changes in the median and ulnar nerves secondary to positioning. All bony prominences and dependent areas are reinforced with foam padding. Our preference is not to flex the operating room table so the patient is not instrumented in a scoliotic position, another reason for our use of the Jackson table. A lateral position, perpendicular to the table, permits the surgeon to manually restore or improve the vertebral alignment. The dependent leg is flexed at the hip and knee to further stabilize the patient while the opposite leg remains extended. This extension of the ipsilateral hip places the psoas muscle on stretch, which can aid exposure of the thoracolumbar vertebrae. A pillow is placed between the legs to prevent pressure sores. The back remains exposed and prepared in situations where a combined anterior and posterior approach is indicated, and the iliac crest facing the surgeon is included in the surgical field ( ▶ Fig. 33.1 a, b).

33.4.2 Skin Incision

The level of fracture typically determines the skin incision. For high to midlevel thoracic fractures, a right-sided thoracotomy is used, with the incision made directly over the rib of the highest level to be instrumented. The incision is performed from the anterior axillary line to the posterior axillary line. Generally, the rib two levels proximal to the fracture are identified as a starting point. For lower thoracic and thoracolumbar fractures, a left-sided thoracotomy is used, with the incision typically performed over the 10h rib. The incision is carried to the costochondral junction and then parallel to the lateral rectus abdominis muscle edge if needed. This approach is less bloody and does not result in paraspinal muscle denervation compared with the posterior approach. Regardless of initial anatomical landmarks, the skin incision should be confirmed with preprocedure fluoroscopy.

33.4.3 Intraoperative Imaging

Intraoperative fluoroscopy or radiographs are essential in confirming the correct level of operation. Fluoroscopy also checks for proper positioning by noting the direct lateral position and can be used intraoperatively to check structural graft or implant placement, as well as screw start points and trajectories. With new technology such as the O-arm Surgical Imaging System with StealthStation Navigation (Medtronic Sofamor Danek, Memphis, Tennessee), intraoperative neuronavigation is an option for hardware guidance; however, it requires careful consideration of the arrangement of the operative theater and patient positioning. Fluoroscopy and neuronavigation necessitate use of a radiolucent operating table.

33.4.4 Other Essentials

Thoracolumbar cases require long instruments, such as periosteal elevators, rongeurs, and curets, for ease of operating. We routinely use cell saver in nontumor cases to minimize potential transfusions. A vascular surgery set containing long, fine-tipped, right-angle clamps, silk ties, medium vessel clips, vessel retractors, renal vein retractors, and periosteal retractors is also used. Self-retaining retractors such as the Omni-Flex (Omni-Tract Surgical, St. Paul, Minnesota) or Thompson-Farley systems (Thompson Surgical Instruments Inc., Traverse City, Michigan) may also be used; however, we find a handheld retractor to be most helpful. A high-speed drill with multiple bits allows for easier bone removal; however, most of the bone is removed with a rongeur or osteotome technique to preserve autologous bone for grafting. Custom drapes containing clear plastic caudally are also used to visualize the feet in case a Stagnara wakeup test is needed. ⁷

33.4.5 Intraoperative Monitoring

Although somewhat controversial given recent data on benefit versus cost, neurologic monitoring for all instrumented spinal surgeries has become standard at our institution. Specifically, somatosensory evoked potentials and motor evoked potentials are monitored throughout the case. Upper and lower extremity monitoring is also performed to monitor not only the deformity correction but also patient positioning. The Stagnara wakeup test remains the gold standard, but it is rarely used. The wakeup can be performed after deformity correction or placement of implants or if a neuromonitoring change is detected. Good communication with the anesthetic team is required in these situations, and a checklist of potential causes should be screened (e.g., patient temperature, change in anesthetic medications, mean arterial pressure, and a review of the immediately preceding surgical steps).

33.4.6 Procedure

Approach

After the skin incision is made, the selected rib is removed in a subperiosteal manner from the anterior costochondral articulation anteriorly as far posteriorly as possible. A rib cutter or rongeur can be used to fashion smooth cuts on the rib, with bone wax used on the edges for hemostasis. The removed rib is saved for autograft. With the aid of a double-lumen endotracheal tube, single-lung ventilation is then performed. The chest is entered after the pleura is incised and a rib-spreading retractor is placed for better visualization. The vertebral bodies are identified immediately, and fluoroscopy can be used for fracture localization. The parietal pleura is elevated with Bovie electrocautery (Bovie Medical Corporation, St. Petersburg, Florida) to expose one body above and one body below the level of interest. Careful attention is given to identify the segmental vessels in the valleys and the disk space on the hill. Unilateral ligation of the segmental vessels is performed using silk suture ties or vessel clips; when performed at the midlevel of the vertebral body, ligation typically does not result in neurologic compromise. In the midthoracic and thoracolumbar junction, the segmental vessels typically arise directly posteriorly from the descending aorta and run horizontally to slightly oblique. Careful attention is given to avoiding ligation of the segmental artery too far posteriorly because this may result in vessel retraction and possible neurologic compromise. Exposure is then completed with the entire lateral aspect of the vertebral body identified. Removal of the rib head with a rongeur may be required to properly place anterior instrumentation.

If access is needed to the thoracolumbar junction, the diaphragm may be taken down to facilitate exposure. The key landmark for entrance to the retroperitoneal space and the underside of the diaphragm is the costochondral cartilage of the removed rib. Splitting the cartilage in the horizontal plane of the rib identifies the retroperitoneal fat below. The cartilage is also tagged for reapproximation during closure. The plane can then be developed with blunt finger dissection to identify the undersurface of the diaphragm. The diaphragm can then be safely divided between stay sutures 1 to 2 cm from the chest wall. Because innervation to the diaphragm is from central to peripheral, it is detached sharply at its periphery along with the left crus with at least a 2 cm cuff for reattachment. We routinely “tunnel” under the diaphragm by elevating the crus, without taking down the diaphragm, if exposure to only L1 is needed. If further exposure is needed below L1, the retroperitoneal plane can be continued distally after the psoas muscle. The ureter should be identified and retracted medially with the peritoneum. The psoas muscle is elevated anterior to posterior beginning at the disk space to avoid segmental disruption. We often dissect first at each disk space and then connect the areas with segmental vessel ligation for L3 to L4 dissections. It is important to carry the dissection posteriorly to identify the pedicle junction, as well as anteriorly around the anterior longitudinal ligament (ALL). Careful attention should also be directed to identifying the exiting nerve roots as well as the sympathetic chain overlying the vertebral bodies. Sacrifice of the sympathetics will cause an ipsilateral warm, dry extremity postoperatively, which often reverses with time. With exposure complete, the self-retaining retractors can be readjusted to provide optimal exposure. Wet lap sponges are applied to the peritoneum and lung prior to blade retraction.

The disk material from the interspace above and below the fracture level is then removed using a no. 15 blade scalpel to cut the annulus and pituitary rongeurs to remove the disk material. A large Cobb elevator (Codman, Raynham, Massachusetts) can be used to create a plane at the end plate junction to ease in disk removal. The great vessels are protected anteriorly with a Chandler retractor or sponge stick. In acute fractures, the ALL is typically spared. In more chronic fractures or malunions, the ALL must be completely released because it is often contracted. The diskectomy is completed posteriorly to identify the posterior longitudinal ligament.

The corpectomy of the affected vertebral body level is then initially performed using rongeurs or osteotomes to remove any bone fragments. In acute fractures, all the removed bone is saved for autograft use. The anterior and contralateral vertebral cortexes are frequently spared because this provides a shell of bone to protect the vascular structures and assist in containing graft material. As the posterior cortex is approached, careful attention is focused on finding the spinal canal, which lies in the plane of the rib head articulation. A high-speed drill with a side-cutting bit (AM8 for the Midas Rex, Medtronic Sofamor Danek, Memphis, Tennessee) is used to safely remove the posterior cortex without damaging the dura or neural elements. Any retropulsed fragments can be removed with a long, forward-angled curet by peeling them away from the canal or using long pituitary rongeurs. Brisk epidural bleeding should be expected with entrance into the spinal canal. Powdered Gelfoam (Pfizer, Inc., New York, New York) soaked with thrombin is an excellent hemostatic agent to control epidural bleeding. If the fracture fragments have caused a dural tear, adequate exposure to identify the cerebrospinal fluid (CSF) leak is needed and a primary repair achieved, if possible. Our preferred suture for dural closure is either a 4–0 Nurolon or 6–0 Prolene (Ethicon, Inc., Somerville, New Jersey). If unable to safely place the suture, DuraGen (Integra LifeSciences Corporation, Plainsboro, New Jersey) can be used as an onlay graft. If a CSF leak persists, a lumbar drain is placed postoperatively to provide a diversion and prevent formation of a CSF or pleural fistula. With bony removal complete, the posterior disk anulus is resected at the disk space level, if needed. Decompression is ensured by palpating across the spinal canal to the opposite pedicle with either a Penfield no. 4 or a dental instrument. If decompression is complete, reconstruction can then be started.

Anterior Reconstruction

Anterior reconstruction consists of structural support and anterior instrumentation. We routinely place the screws before the graft placement, but this is discussed after the anterior support section. Options for structural support in anterior reconstruction include autograft, such as tricortical iliac crest graft, femoral or humeral shaft allograft, or polyethylethylketone (PEEK) cages filled with autograft bone or bone graft substitute. The advantages of autograft include not only being structurally sound but also autologous in nature. The disadvantages of autograft include the size of graft needed as well as potential donor site morbidity, although this potential is quite low for rib autograft. The advantages of using structural allograft bone include the absence of donor site morbidity while also being structurally sound. The disadvantages include disease risk transmission and the lack of true osteoinduction. The advantages of manufactured structural interbody support include being structurally sound while lacking the risk of disease transmission and the capability to provide a custom fit. The main disadvantage of implants is their cost; however, this may be offset by the potential complications that can occur with autograft or allograft. Our preference is to use PEEK cages packed with morcellized bone from the fractured vertebra and rib harvest. Our preference for PEEK is based on the material’s similar modulus of elasticity to bone, thus reducing additional stress forces on the construct. With the development of expandable vertebrectomy cages available in a wide range of sizes and lodotic angles, the implant can be better customized to the patient’s anatomy. The corpectomy defect is distracted primarily with manual force applied posteriorly with the surgical assistant’s fist at the apex of the deformity. The corpectomy defect can also be distracted within the defect by laminar spreaders and various insertion ramps. The custom cage packed with autograft is then placed into the corpectomy defect, with optimal placement being slightly anterior. The anterior placement assists with load sharing and correction of the segmental loss of height ( ▶ Fig. 33.2 a–c).

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