Over the years, pedicle fixation systems proved to be biomechanically superior for segmental fixation. Thus, numerous systems and variations have been developed and continue to be developed by several spine companies in the US and abroad.
Advantages of Pedicle Screw Fixation:
Since pedicle screws traverse all three columns of the vertebrae, they can rigidly stabilize both the ventral and dorsal aspects of the spine. The pedicle also represents the strongest point of attachment of the spine and thus significant forces can be applied to the spine without failure of the bone-metal junction. Furthermore, the rigidity of pedicle fixation allows for the incorporation of fewer normal motion segments in order to achieve stabilization of an abnormal level.
Pedicle screw fixation does not require intact dorsal elements. Thus, it can be used after a laminectomy or traumatic disruption of laminae, spinous processes and/or facets. Additional advantages include less requirements for postoperative bracing and improvements in fusion rates.
Disadvantages of Pedicle Screw Fixation:
1. Steep learning curve.
2. Caudal or medial penetration of the pedicle cortex can result in dural or neural injury.
3. Implantation of pedicle screws requires extensive tissue dissection to expose the entry points and to provide the required lateral to medial orientation for optimal screw trajectory.
4. Lengthy operative time with potential for significant blood loss and increased risk of infection.
5. Postoperative imaging studies (especially MRI) are, in part, obscured by the implants.
6. Rigid fixation can accelerate adjacent motion segment degeneration.
7. Costly procedures.
Principal Indications for Pedicle Fixation:
1. Existing painful spinal instability:
* post-laminectomy spondylolisthesis
* painful pseudoarthrosis
2. Potential instability:
* spinal stenosis
* degenerative scoliosis
3. Unstable fractures.
4. Augmenting anterior strut grafting:
* tumor
* infection
5. Stabilizing spinal osteotomies.
Contraindications for Pedicle Fixation:
1. Recent infection.
2. Laminectomies that will not cause instability
3. Fusions which are normally successful without fixation.