Planning and positioning
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Preoperative plain radiographs and computed tomography (CT) should be obtained to evaluate bone quality and pedicle size and angle. The entry point for pedicle screw placement is variable in the thoracic spine, and anatomic landmarks are unreliable. Preoperative planning using CT and plain films is important. The transverse width of the pedicle can be determined using preoperative CT and is the limiting factor in screw size. Frameless stereotaxy can improve accuracy of pedicle screw placement.
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The patient is placed prone on chest bolsters, a Wilson frame, or a Jackson table to release abdominal contents from pressure, preventing epidural venous congestion and intraoperative blood loss.
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The pelvis and knees are flexed to augment normal thoracic kyphosis.
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If upper thoracic spine fixation is needed, the head must be fixed in a neutral position with a Mayfield head frame with the patient’s arms secured on the sides.
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In mid-thoracic to lower thoracic spine fixation procedures, the head need not be secured, and the arms are positioned at 90-degree angles above the head. The axilla is cushioned with foam pads.
FIGURE 69-1:
The patient is positioned prone with chest bolsters taking pressure off the abdomen. The arms are placed at no more than 90-degree angles to prevent brachial plexus injury. A Mayfield head frame is placed in upper thoracic fusions.
Procedure
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