Posterior stabilization

Based on CT and MRI imaging, a plan should be prepared to determine:

• The size and optimal location of implants used
• Whether spinal cord decompression is necessary and if so, the amount of tissue to remove in order to achieve sufficient spinal cord decompression

Every case will be unique, and we will here illustrate just one example.

In patients requiring posterior lateral decompression, not requiring anterior column reconstruction, bilateral posterior pedicle screw fixation fixation with minimum fixation of at least one level above and below the involved segment should be used.

Short segment constructs lead to increased stress on the posterior implants increasing the risk of implant failure (screw pullout/fracture). The risk of implant failure may be decreased by cement augmentation of fenestrated screws and through reconstitution of the anterior column using cement augmentation of the pathological fracture.

Fixation of multiple spinal segments does not affect functionality in the thoracic spine due to the presence of rigid rib cage. Adequate screw purchase should be aimed for during initial surgery as revision surgeries are too demanding for these patients.

The preoperative neurological assessment must be carried out as described in the Neurological Evaluation.

For this procedure the patient is placed in the prone position and the posterior midline approach is used.

Pedicle screws are inserted one or two levels above and below the tumor on both sides.

In cases of multilevel tumors or poor bone quality this construct can be extended.

In tumor patients achieving optimal screw purchase is even more important than in trauma patients to minimize risk of pullouts and reduce the number of levels involved.

Optimal pedicle screw purchase will, in order of importance, be achieved by:

1. Selecting the largest possible screw diameter
2. Selecting the longest possible screw
3. Positioning of the screw under the cranial endplate
4. Cement augmentation of the screw.

• Pedicle screw insertion

Rod contouring should mainly follow the curvature of the spine. Reducing preexisting deformities is typically not necessary and may lead to screw pull-out.

The rod is inserted into the screw heads and the screw heads are tightened with the inner nuts.

If posterior decompression is performed only one rod is inserted to facilitate access to the spinal canal.

Life expectancy and performance status should be used to determine whether bone grafting is indicated.

For patients with good prognosis and a long life-expectancy, posterior fusion may optionally be performed using allograft and/or local autograft.

For nonfusion surgeries, the facet joint capsule is preserved during the entire procedure.

If the surgeon plans for a fusion, the facet capsule is excised, and the joint cartilage surfaces and posterior cortex are denuded/curetted.

Pieces of bone graft (autograft, allograft) are inserted into the decorticated facet joint for fusion.

Prior to wound closure, intraoperative imaging is performed to check the adequacy of reduction, position, and length of screws and the overall coronal and sagittal spinal alignment.

Lateral view of the above.

Patients are made to sit up in the bed on the first day after surgery. Bracing is optional but preferably omitted for patient comfort. Patients with intact neurological status are made to stand and walk on the first day after surgery.

Patients can be discharged when medically stable or sent to a rehabilitation center if further care is necessary.

During admission adequate caloric intake of a high-quality diet should be monitored.

Patients are generally followed with periodical x-rays and (optionally) MR imaging at 6 weeks, 3 months, 6 months, and 1 year to monitor for tumor recurrence and hardware failure.

Postoperative radiation is required to avoid tumor recurrence. SBRT is usually initiated within two weeks following surgery. Conventional radiotherapy is usually initiated 2-4 weeks after surgery to reduce the risk of wound healing disturbances.

The radiation modality is selected based on tumor histology and history of prior radiation.