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Several surgical techniques are available for the treatment of thoracolumbar fractures, such as isolated posterior, isolated anterior, and combined posterior-anterior surgical approaches. However, currently there are no evidence-based treatment guidelines to help choose the approach. Therefore, treatment selection is mostly based on surgical experience and the available technology in the treating hospitals. A large multicenter study has most recently evaluated the current treatment strategy for thoracolumbar fractures in the German-speaking countries.1 The study found that the isolated posterior approach is the treatment of choice, followed by the posterior-anterior approach.

When surgical treatment is indicated, such as a posterior stabilization/fusion, the planning should focus on four basic treatment principles, as defined by the AO Foundation in 1958:

• Anatomic reduction

• Stable internal fixation

• Preservation of blood supply

• Early, active mobilization

If these principles are applied to spinal surgery, then the treatment goals for thoracolumbar fractures are restoration of physiological alignment by adequate reposition; stable internal fixation to maintain reduction; and early, active mobilization of the patient.

In 1977, Magerl² began to develop an external spinal skeletal fixation (ESSF) system to treat thoracolumbar fractures. The system entailed minimally invasive surgery and the placement of Schanz screws. Thus, it was Magerl who described the first percutaneous transpedicular approach to the spine. However, the use of an external fixator led to some patient discomfort. In 1984, Dick³ reported greater mechanical stability for an internal fixator as compared with Magerl’s external fixator. Thereafter, the use of an internal fixator became, and has remained, the standard treatment to reduce and stabilize thoracolumbar fractures.

An open approach with appropriate implants (Fig. 3.1a) complies with three of the four AO principles, the exception being preservation of blood supply. This approach enables the surgeon to achieve adequate reposition with good stability as well as dorsolateral/intersegmental fusion within the injured motion segment. However, open surgical access is associated with significant soft tissue trauma, which might explain the prolonged postoperative pain that patients report in the access region.^4,5

To avoid these biological problems, there has been a clear trend toward minimally invasive surgery (MIS) of spinal pathologies (Fig. 3.1b). This trend has been supported by innovations in implant technologies, which enable adequate restoration of sagittal and frontal alignment by using a MIS approach for posterior fixation of spinal fractures.

Fig. 3.1a,b (a) Open traditional approach for an Schanz screw–based posterior fixation. (b) Percutaneous approach for an Schanz screw–based posterior minimally invasive surgery (MIS) procedure.

Although there are no validated guidelines for deciding on operative or nonoperative (conservative) management of thoracolumbar fractures, classification systems such as AOSpine,6 Thoracolumbar Injury Classification and Severity Score (TLICS),⁷ and the load-sharing classification⁸ can help the surgeon determine the fracture mechanism and the appropriate treatment strategy. Clear evidence of posterior tension-band injury, described as type B and C fractures in the new AOSpine classification⁶ is widely accepted as an indication for operative treatment, but controversy remains regarding the management of type A fractures in which posterior ligamentous structures remain intact. Some surgeons advocate conservative management even for AOSpine type A4 fractures, based on questionable clinical studies with insufficient numbers of patients and selection bias.⁹ However, thoracolumbar burst fractures (AOSpine types A3 and A4) should be evaluated carefully to determine whether conservative management or operative treatment is appropriate. Based on published recommendations from the spine working group of the German Society of Orthopaedic and Trauma Surgeons,¹⁰ surgery is indicated for type A thoracolumbar fractures in which there is monoor bisegmental sagittal deviation > 15 to 20 degrees or frontal misalignment > 5 degrees.

Indications

The ideal indication for posterior MIS fixation is a Chance fracture (AOSpine type B1) with horizontal vertebral body disruption and posterior tension-band insufficiency caused by a hyperflexion injury. The posterior construct will replace the insufficient posterior tension band until the vertebral body and the posterior bony elements show solid bony healing.

An absolute contraindication for a posterior MIS approach is the inability to visualize the radiological landmarks when using fluoroscopy-guided posterior percutaneous techniques. This might occur in cases of severely obese patients or patients with an unusual anatomic configuration of the spine.11

Some case reports describe MIS management of type C fractures, but these fractures are usually highly unstable, and it might be difficult to achieve adequate decompression and repositioning with a posterior MIS approach. Therefore, type C fractures are a relative contraindication for a posterior MIS approach.

Advantages and Disadvantages of Posterior MIS Procedures (Table 3.1)

Posterior percutaneous/mini-open MIS procedures entail less soft tissue damage because they use small skin incisions and a muscle-dilating or transmuscular approach. Kim et al¹² demonstrated significant less muscle damage with percutaneous spinal fusion than with open spinal fusion. The same findings were reported by Grass et al¹³ for MIS procedures in cases of thoracolumbar fractures by analyzing the muscle activity with needle electromyography (EMG). The MIS approach resulted in less intra-operative blood loss and less need for blood transfusion postoperatively. Recent studies also report less postoperative pain and better scores for physical function in comparison with the standard open posterior approach.

However, the use of percutaneous techniques is challenging because the surgeon must rely on radiological images, rather than tactile feedback, when inserting the percutaneous transpedicular screws. Radiological landmarks (e.g., the medial pedicle border) must be respected so as to avoid screw misplacement (Fig. 3.2).

Table 3.1 Advantages and Disadvantages of Posterior Minimally Invasive Surgery

The key factors for successful treatment of thoracolumbar fractures is adequate repositioning and maintenance of the frontal and sagittal spinal alignment. With the percutaneous approach, depending on the type of implant used, adequate intraoperative repositioning and postoperative maintenance of the alignment can be challenging (Fig. 3.3). Additional anterior fusion might be necessary to maintain the percutaneously achieved repositioning.

Fig. 3.2a–c Problems of posterior MIS procedures. Medial screw malposition grade 3 after posterior MIS fixation of a L2 burst-split fracture (AOSpine type A4), resulting in a radiculopathy (L2 right) and weakness of hip-flexion motor, grade 4.

The patient is intubated and placed in the prone position on a radiolucent table. Pillows are placed underneath the chest and pelvis to bring the target spinal area into a hyperlordotic position (Fig. 3.4). This positioning facilitates fracture reduction by ligamentotaxis in anterior column compression fractures, and provides room for anteroposterior (AP) and lateral fluoroscopy, which is used to identify radiological landmarks (Fig. 3.5). In cases in which the landmarks cannot be identified radiographically, especially in the AP plane, an open surgical approach must be performed.

Fig. 3.3a–e Problems with posterior MIS procedures. (a–c) X-rays and sagittal computed tomography (CT) reconstruction of multilevel lower thoracic fractures (T10 AOSpine type A1, T11 AOSpine type A3, and T12 AOSpine type A1). (d,e) Postoperative implant failure and increased kyphosis.

Fig. 3.4 Demonstration of prone positioning on a radiolucent table.

Dekutoski et al14 suggests that two different incisions can be used to approach the subcutaneous space: (1) a traditional paraspinal approach with several short skin incisions that are in line with the pedicle trajectory and are recommended especially for short segment fusion; and (2) a midline incision and subcutaneous lateral dissection if longer constructs are required, providing good cosmetic results. To access the screw entry points on the posterior bony surface, a muscle-dilating approach (trans–musculus longissimus) is the standard approach. An alternative, according to Dekutoski et al, is a muscle-splitting semi-open approach between the multifidus part and the longissimus part of the musculus erector spinae. However, this semi-open approach is more invasive and requires a complete fascia opening over the entire length of the construct to prevent entrapment of the fascia while inserting the rod.

Fig. 3.5a,b (a) True anteroposterior (AP) and (b) true sagittal views of L1. (a) Red lines indicate the medial margin of the left and right pedicle. Red spot indicates the correct pedicle entry point. (b) Red lines indicate the cranial and caudal pedicle and the posterior wall of the vertebra. Red circle indicates the correct pedicle entry point.

The correct entry points are identified under AP fluoroscopy by using a Jamshidi^® needle (CareFusion Corp., San Diego, CA) or a pedicle awl. The correct entry point for the right pedicle is located at the 3 o’clock position and for the left pedicle at the 9 o’clock position at the lateral margin of the pedicle eye. The central sagittal position and the sagittal orientation of the Jamshidi needle should be confirmed by a lateral fluoroscopic image. Then the Jamshidi needle is advanced transpedicularly into the vertebral body. The horizontal convergence should be adapted to the regional requirements. Fluoroscopic AP views should monitor the advance of the needle tip, until the medial corticalis has been reached (Fig. 3.6a). A lateral fluoroscopic image confirms the needle position in the sagittal plane (Fig. 3.6b). If the needle tip has already passed the posterior vertebral wall, a violation of the medial pedicle boarder is very unlikely. Then the needle is safely advanced into the center of the vertebral body. If the needle tip is still located in the pedicle area, a medial breach might occur when the needle is advanced further. Therefore, the needle should be retracted and redirected with a lower convergence, as monitored under AP-fluoroscopic control. The lateral view should confirm the correct positioning of the needle tip behind the posterior wall of the target vertebra.

After confirmation of correct Jamshidi needle positioning within the vertebra, the inner trocar is replaced by a Kirschner wire (K-wire) and the Jamshidi needle is withdrawn (Fig. 3.7a). Depending on the implant used, tapping is required. Then a screw of appropriate length and diameter is inserted using the Seldinger technique.¹⁵ This procedure should be monitored on a lateral fluoroscopic view to ensure the correct positioning of the K-wires, which have a tendency to migrate forward while inserting the screws¹⁶ (Fig. 3.7b,c). After reaching the final screw position, an AP C-arm view should confirm the appropriate screw trajectory in the frontal plane (Fig. 3.7d).

Repositioning

Depending on the implant used, rods are inserted from the cranial to the caudal direction by using an additional cranial incision or by using the cranial screw portal. The rods may be bent as needed to adapt to the anatomic condition: moderate kyphosis within the thoracic spine, straight within the thoracolumbar junction, or lordotic within the lumbar spine.

Fig. 3.6a,b (a) The medial pedicle margin has been reached, as demonstrated on a true AP view. (b) Lateral view indicates too much convergence, while the needle tip is still inside the pedicle. The needle should not be further advanced, and the convergence must be reduced.

After insertion of the Schanz screws, the fracture clamps are placed on the proximal and distal screws (Fig. 3.8). The rod is inserted through the cranial portal into both clamps. Then the whole construct is pushed toward the spine. The distance between the two Schanz screws is secured by tightening the rod to the fracture clamps. Tilting both caudal screws into a cranial direction and both cranial screw into a caudal direction helps restore the appropriate lordosis. If the vertebral height is insufficient, a gentle bilateral distraction (or unilateral distraction to correct traumatic scoliosis) might restore the vertebral body height. However, care should be taken not to over-distract the motion segment, especially in AOSpine type B2 fractures. When adequate reduction is achieved, the clamps are tightened with limited torque and the Schanz screws are cut.

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