17: Anterior Thoracolumbar Spinal Fusion via Open Approach for Idiopathic Scoliosis

Published on 21/04/2015 by admin

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Last modified 21/04/2015

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Procedure 17 Anterior Thoracolumbar Spinal Fusion via Open Approach for Idiopathic Scoliosis

Peter G. Gabos

Indications

image To halt progression of spinal curvature

image To restore spinal alignment and balance

image To preserve caudal motion segments (typically one to two segments) when compared with posterior spinal fusion (PSF)

image To prevent the crankshaft phenomenon in skeletally immature patients (Risser 0, open triradiate cartilage)

image To allow for a thoracoscopic approach in selected cases

image Appropriate candidates typically include Lenke type 1 (single structural thoracic) and Lenke type 5 (single structural thoracolumbar/lumbar) curves (Figure 17-1, A and B).

image image

FIGURE 17-1, A-B

Indications Pitfalls

• Anterior surgery tends to be “kyphogenic.” This may not be appropriate in curves with thoracic kyphosis greater than 40 degrees or in cases of thoracolumbar (“junctional”) kyphosis or lumbar hypolordosis.

• Patients weighing greater than 60 kg, with curves greater than 75 degrees, with or without hyperkyphosis, are not candidates for single-rod thoracic open or thoracoscopic fusion.

Indications Controversies

• Does sparing a spinal motion segment significantly benefit the patient?

• Are there more risks/complications with anterior surgery?

• Is there better correction of curvature with anterior versus posterior surgery?

Examination/Imaging

image Clinical assessment of curve location, coronal and sagittal balance, trunk rotation, shoulder asymmetry, pelvic obliquity, integrity of the neuraxis, and any other associated anomalies

image Full-length standing posteroanterior, lateral, and right and left supine bending radiographs to assist in curve classification, assessment of curve flexibility, and selection of fusion levels

image Magnetic resonance imaging in selected cases (e.g., neurologic signs or symptoms, early- or juvenile-onset scoliosis, rapid curve progression, unusual curve pattern)

Treatment Options

• Posterior spinal fusion with dual-rod instrumentation

• Anterior spinal fusion with single- or dual-rod instrumentation, by open or thoracoscopic technique

Positioning

image The surgical approach is always from the convex side of the curvature in the lateral decubitus position.

Positioning Pearls

• Copious padding of all bony and soft tissue prominences, such as the axilla (“axillary roll”) and lateral knee, is required to prevent a compressive neuropathy or pressure necrosis of the upper or lower extremity or trunk.

• Electrophysiologic monitoring of the upper extremities will allow early detection of compressive neuropathies, prompting immediate repositioning and/or repadding of the upper extremity.

• A flat radiolucent table and beanbag positioner are utilized.

• When utilized, unobstructed fluoroscopic access is verified before preparation and draping.

• Neurophysiologic monitoring of spinal cord function, using both somatosensory evoked potential and transcranial motor evoked potential monitoring, is recommended to optimize patient safety.

Portals/Exposures

Thoracic

image Standard thoracotomy approach gives access to vertebral levels T2 to approximately L1.

image Expanded access can be achieved with the use of a double thoracotomy if absolutely necessary.

Thoracolumbar

image A tenth rib thoracoabdominal approach allows the greatest exposure and versatility for fusions crossing the thoracolumbar junction (Figure 17-2).

image

FIGURE 17-2

Lumbar

image An anterior retroperitoneal flank approach gives sufficient access to vertebral levels.

Portals/Exposures Pearls

• Thoracic (open technique)

• Single-lung ventilation is not required but does allow for better visualization during the procedure.
• Standard thoracotomy is utilized, typically choosing the interspace corresponding to the apex of the deformity.
• Constructs spanning more than seven levels may require a double thoracotomy.
• To limit incision size and chest wall dissection, disk excision and screw implantation can be done through small percutaneous accessory incisions at the more cephalad or caudad levels.

• Thoracolumbar

• Split the costal cartilage at the tip of the tenth rib, maintaining the attachments to the diaphragm (cephalad cartilage tip) and abdominal musculature (caudad cartilage tip).
• Use temporary stay sutures to mark the diaphragm as it is incised, for later reapproximation.
• Reapproximate the split tenth rib costal cartilage to initiate closure.

• Lumbar

• Beware of the thinning musculature and superficial location of the peritoneum medially near the rectus sheath.
• Dissection should proceed medial to the psoas muscle.
• The genitofemoral nerve lies directly on the psoas muscle.
• The iliolumbar vein consistently requires ligation when working at the L4-5 level.
• Preserve paraspinous sympathetic fibers that do not interfere with the dissection.

Procedure: Thoracolumbar Spine Fusion via an Open Approach Using Single-Rod Instrumentation

Step 1: Anterior Release and Diskectomy

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