Vertebral Resection for the Correction of Fixed Coronal Deformity

Clifford B. Tribus

INDICATIONS/CONTRAINDICATIONS

The spine surgeon has several different options for reestablishing spinal balance in the patient with spinal deformity of the thoracolumbar spine. In patients with flexible deformity in the sagittal or coronal plane, a posterior, anterior, or combined anterior and posterior approach will typically suffice to correct the deformity and maintain spinal balance. When a fixed spinal deformity exists, particularly with spinal imbalance, spinal osteotomy is often necessary to reestablish spinal balance. A rare subset of patients exists who have a fixed spinal deformity in the coronal plane. In these patients, posterior osteotomy alone and even anterior/posterior osteotomy procedures are not sufficient to correct coronal deformities (3,5,7,9,12,13). In order to reestablish spinal balance safely in these patients, the spine must be shortened and translated. This requires vertebral body resection (VBR) (1,2,4,6).

The indication for VBR is loss of spinal balance in the coronal plane. As with other spinal deformity problems, the indications for surgery are pain, progression, neurologic deficit, and cosmesis. Additionally, the patients with coronal deformity will frequently have a substantial functional deficit.

The diagnosis leading to a fixed coronally decompensated spine is most commonly postsurgically treated idiopathic scoliosis. Congenital scoliosis or other postsurgical deformity patient may also lead to fixed coronal deformity.

Confirming the diagnosis of fixed coronal deformity is self-evident on physical exam and standing plane radiographs. Supine bending films will confirm the fixed nature of the deformity. Vertebral resection is not necessary, however, unless the shoulders are parallel or angled away from the coronal deformity. If the shoulders are positioned in this manner, resection is necessary to allow shortening and translation of the spine enabling the shoulders to be rebalanced and centered over the pelvis.

The wide utilization of the pedicle subtraction osteotomy (PSO) has allowed the expansion of the PSO technique to include dorsal vertebral column resection (VCR). This evolving technique allows a full three-column resection of the vertebral column from the posterior approach and is a viable alternative to the anterior and posterior VBR. The neural elements are more readily identified from the posterior side, while risk to the local vasculature is greater (10,11,14, 15, 16). The surgical technique for both will be presented.

PREOPERATIVE PLANNING

Patients indicated for VCR require extensive preoperative evaluation. A cursory review of posture and radiographs will establish the necessity of the procedure, but a careful physical exam and assessment of the patient’s state of health is required to determine if the patient is a candidate for this extensive procedure.

These deformities are typically quite complex. Any neurologic deficit needs to be explained and the question of its reversibility answered. Preoperative cardiopulmonary and nutritional status should be assessed. In addition to being physically prepared to undergo extensive surgery, the patient should be emotionally prepared. A support system should be in place, and most importantly, the goals between physician and patient should be matched and realistic. If the patient is a candidate, he or she should donate autogenous blood.

Radiographic studies would include standing AP and lateral radiographs on long films, as well as supine bending films to assess flexible correction. MRI is useful to assess neurologic elements as well as discs of areas not to be included in the fusion. A CT scan with sagittal and coronal reconstructions is needed to assess previous fusions and to plan for hardware placement and resection. Consideration should be given to utilizing intraoperative computer-assisted technology for the placement of hardware and performance of VCR.

The surgeon should plan for neurologic monitoring depending on the level of the resection and proposed hardware placement. Both Tc motor evoked potentials and somatosensory evoked potentials should be utilized. The potential need for a wake-up test should be discussed with the patient preoperatively. The need for a monitored bed in an intensive care unit should be anticipated and prearranged.

SURGICAL TECHNIQUE

The Anterior Approach

In the case when an anterior/posterior resection is planned, the anterior spine is approached first. The typical scenario is a two-level resection at the apex of the deformity. For the purpose of discussion, a resection of T12 and L1 will be described. Neurologic monitoring should also be established prior to positioning.

The patient is positioned, well padded, on the operating table in the lateral position with the convexity of the deformity up. A double arm board, axillary roll, and pillows between the knees are useful adjuncts to a beanbag and three-inch cloth tape to secure the patient to the operating table. Take care to protect the peroneal nerve on the down leg. In planning the incision, be mindful of the rib/vertebral angle, as the ribs may be quite vertical, thus requiring the approach to be made through a more proximal rib. Additionally, if the approach is proximal to the ninth rib, a double-lumen endotracheal tube should be considered. A standard thoracic, thoracolumbar, or lumbar approach is performed, and the levels to be resected are exposed. To approach T12-L1, a thoracolumbar approach is performed.

The incision is created with a skin knife, and subcutaneous tissues and underlying muscle layers are incised with electrocautery. If the diaphragm needs to be mobilized, it may be peeled directly off of the chest wall with electrocautery either from above or below. I prefer the superior approach, applying traction on the diaphragm with a sponge stick and incising the diaphragm at its insertion on the chest wall. A cuff of diaphragm may be left on the chest wall to facilitate later closure or the diaphragm may be directly repaired to the chest wall. Particular care should be given to incising the crus of the diaphragm as large segmental vessels are often found just deep to the crus.

Ipsilateral segmental vessels are controlled and markers placed to confirm radiographically that the appropriate levels are exposed (Fig. 21-1). An osteoperiosteal flap is then elevated. The purpose of the flap is to later contain the morcelized graft placed in the vertebrectomy site, yet in adults, a true flap is difficult to develop.

In performing the resection, you need to recognize and utilize as many visual clues as to the location and orientation of the spinal cord as possible. Discectomies are performed proximal and distal to the levels to be resected. Often the patient has already had an anterior fusion ablating the discs. The CT scan with reconstructions should be scrutinized for residual landmarks in the fusion mass. The pedicles are a particularly reliable landmark for the initial localization of the cord. Given that these deformities are in three dimensions, however, once the cord is localized, its direction is still often not clear. At the start of the resection, a rongeur is used so that resected bone may be reused as bone graft. As the posterior cortex is approached, use a diamond-tip burr to reduce the risk of dural tear. The posterior cortex is thinned and then resected with small curettes and Kerrison rongeurs. The posterior longitudinal ligament (PLL) should be left intact as both a landmark and a biologic barrier (Figs. 21-2

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