Deformity

Tumor

Degenerative disease (stenosis)

Disk herniation

Trauma

Carefully assess preoperative imaging for the presence of dural ectasia, sclerotic or atretic pedicles.

Includes plain x-rays (standing, supine, bending films, and traction films), magnetic resonance imaging (evaluation of the neuraxis and the disks and facets), and computed tomography (CT) scan (bony anatomy of individual vertebrae, measurement of pedicles, and measurement of pelvic parameters)

Measure Cobb angles to determine proximal and distal levels of construct and desired correction to maintain global balance.

Consider sagittal vertical axis and pelvic parameters when assessing need for sagittal deformity correction.

Measure approximate lengths and sizes of planned instrumentation.

Review preoperative plain films carefully to establish vertebral level nomenclature for intraoperative localization; careful assessment of scans is imperative to ensure correct levels.

May position prone with Mayfield head holder if crossing cervicothoracic junction or on the prone Jackson table for thoracolumbar exposure

Care should be taken to adjust the hip and chest pads to assist with correction. Proper positioning preoperatively can facilitate deformity correction and fracture reduction. Extra blankets can be placed under the patient’s thighs to facilitate as much natural lordosis as possible. Extra hip pads and/or foam padding can facilitate correction of a lumbar scoliosis. Extra chest pad can be used to facilitate neutral positioning of the cervical spine when head is in ProneView holder.

Ensure posterior iliac crest is prepped and draped if harvesting autograft through a separate incision. If the lumbar spine is being included in the surgery, often the same skin incision can be used with a separate fascial incision over the iliac crest.

Be sure to discuss the anesthesia plan for the case well in advance, to facilitate a multidisciplinary approach to the management of estimated blood loss (EBL) and perioperative pain control.

This plan should include the use of medical management of hemorrhage (for deformity cases, high-dose tranexamic acid bolus and infusion, DDAVP [1-deamino-8-D-arginine vasopressin] administration prior to surgery).

Multimodal anesthesia as needed to include ketamine, intravenous acetaminophen, nonsteroidal anti-inflammatory drugs, long-acting narcotics such as methadone if indicated

In addition, the incidence of postoperative ileus in deformity patients can be quite high, so use of intestinal motility agents and gastric tubes should be considered.

Blood pressure management should also be discussed: mean arterial pressure goal more than 80 mm Hg in the setting of myelopathy or during planned deformity correction; possible use of hypotensive anesthesia in the proper patient (adolescent idiopathic scoliosis) for minimizing EBL during exposure.

Total intravenous anesthesia in the setting of MEP monitoring: the timing of MEPs should be discussed with the anesthesia and neuromonitoring teams prior to surgery. If neurology is intact and not in danger, we obtain MEPs after the flip to the prone position, then allow for administration of paralytic to relax the patient during exposure, which decreases EBL. The paralytic should work off by the time screws are ready to be inserted; if not, the anesthesia team can administer a reversal agent.

Midline incision, either curvilinear over spinous processes or straight approximating midline at surgeon’s discretion

Ensure same counting nomenclature is used between preoperative and intraoperative imaging for localization.

For a long deformity correction, anatomic landmarks can be used; else, preoperative plain films or C-arm can be used, depending on the indication for surgery.

Take care to check levels repeatedly, as it is not difficult to be at the wrong level in the thoracic spine. If in doubt, check with a different radiographic method.

Standard posterior midline approach is utilized.

Continue dissection laterally over transverse process of proximal instrumented vertebra (PIV).

Define anatomic landmarks for freehand pedicle screw insertion at each level:

May use a combination of short and long cerebellar and/or Weitlaner retractors to achieve exposure while minimizing need for retractor repositioning during instrumentation

In a long deformity correction, consider releasing tension on the retractors to minimize paraspinal muscle necrosis. Also consider packing off portions of the wound with sponges to minimize blood loss.

If placing freehand thoracic pedicle screws in the setting of severe deformity, consider use of multiple laminotomies to assist in direct palpation of the pedicles from within the canal to guide screw placement.

For routine deformities (idiopathic scoliosis), dorsal facetectomies (removal of the inferior articular process) are performed throughout the entire construct. In the thoracic spine, an osteotome or gauge is used to resect the inferior articular process. The superior articular process is then denuded of cartilage. Care must be taken at the apex of the thoracic deformity on the concave side, as the facets and pedicles are very close to one another, the deformity is very stiff, and the spinal cord is in close proximity to the pedicles.

In the lumbar spine, the dorsal portion of the facet is removed with an osteotome or rongeur, followed by resection of a portion of the inferior articular process using an osteotome or skinny rongeur. Laminar spreaders may be used in the lumbar spine to distract the joint and to assess flexibility.

In cases where the apex of the curve is very stiff, but the disks appear open anteriorly, posterior column osteotomies (PCOs) may be used. These can render the apex more flexible, but carry an increased risk of neural or dural injury, because of the intracanal work at the apex. If the disks appear fused anteriorly (via CT scan), a PCO is unlikely to facilitate any significant correction.

To perform a PCO, the spinous process of the cephalad vertebra is removed, as is the ligamentum flavum. The flavum resection is widened out to the level of the facet joints bilaterally, and Kerrison rongeurs and/or Leksell rongeurs and/or a burr is used to resect the facets in their entirety, either from medial to lateral or lateral to medial depending on the anatomy. Hemostasis is achieved using thrombin and gelfoam.