- ALIF with Revision Decompression and Reinstrumentation
- Anterior Arthrodesis of the Subaxial Cervical Spine:
- AAOS - Bulletin: A minute of malpractice
- Cage Fixation: (interbody fusion)
- provides excellent stabilization in flexion and lateral bending, but poor stabilization in extension and rotation;
- advantage: may offer fusion rates of over 90% and does not interfere with posterior musculature;
- disadvantage is that a decompression is not possible (if the anterior approach is utilized);
- complications may be higher when cage fixation is performed through a posterior approach;
- specifically this approach may cause chronic radiculopathy due to epineural fibrosis caused by the added epidural manipulation
which is required for this technique;
- another complication associated with a posterior approach is retropulsion of the cage back into the spinal canal causing neurological deficit;
Interbody cage stabilisation in the lumbar spine. Biomechanical evaluation of cage design, posterior instrumentation and bone density.
Interbody fusion cages in reconstructive operations on the spine.
- Pedicle Screw Fixation:
- pedicle screw fixation is generally felt to enhance spinal fusion by providing rigid fixation of spinal vertebrae;
- in the prospective study by France et al 1999, the authors did not find that pedicle screw instrumentation benefited
patients undergoing spinal fusion, except in patients with degenerative spondylolisthesis;
- patients with degenerative disc dz had 63% good to excellent results w/ instrumentation vs 73% w/o instrumentation;
- in those w/ degenerative spondylolisthesis, good to excellent results were found in 80% of patients w/
instrumentation vs 40% w/o instrumentation;
- S1 dorsal screw placement:
- in the anatomic study by Ebraheim, et al (2000), the authors determined the safe zone for S1 screw placement;
- using a starting point located inferlateral to the S1 superior facet, the authors recommend screw direction
30 to 40 deg lateral to avoid comprimising the lumbrosacral trunk and SI joint;
- insertion medial to this direction, might injure the L4 or L5 nerve roots;
- ref: - complications:
- nerve root irriation may be more common with medially placed screws;
- Castro, et al (1996), performed a study of 30 patients with 131
screws placed under flouroscopic control;
- CT images showed cortical penetration in 40% and medial wall penetration in 29%;
- deviation on CT of more than 6mm indicated a high risk of nerve root injury;
The lumbosacral nerves in relation to dorsal S1 screw placement and their locations on plain radiographs.
Accuracy of pedicle screw placement in lumbar vertebrae.
A randomized prospective study of posterolateral lumbar fusion. Outcomes with and without pedicle screw instrumentation.
Complications Associated with Pedicle Screws.
Segmental pedicle screw fixation or cross-links in multilevel lumbar constructs. A biomechanical analysis.
- risk factors include: previous surgery, increased number of fusion levels;
- exam findings:
- worsening of preoperative symptoms;
- localized lumbar tenderness;
- diagnostic studies:
- radiographs: look for hardware failure;
- flexion / extension radiographs (look for abnormal translation);
- 4 mm of translation or more than 10 deg of angular motion between adjacent end plates (comparing
flexion and extension views);
- upto 3 mm of motion can be a normal finding;
- bone scan:
- increased uptake has little predictive value until one year after surgery;
- AP tomograms:
- best radiographic test for pseudoarthrosis;
- Assessment of pseudoarthrosis in pedicle screw fusion: A prospective study comparing plain radiographs, flexion-extension radiographs, CT scanning, and bone scintigraphy with operative findings.
- Failure of technetium bone scanning to detect pseudoarthroses in spinal fusion for scoliosis.
- A comparison of different methods used to diagnose pseudoarthrosis following posterior spinal fusion for scoliosis.
- allows best assessment of non-union
Early rod-sleeve stabilization of the injured thoracic and lumbar spine.