Implantation of interspinous devices is one option for treating lumbar canal stenosis and other causes of low back pain. These devices attempt to produce lumbar flexion by distracting the lumbar spinous processes restoring height and resulting in tightening of the thickened ligamentum flavum, and widening of the central canal and neural exit foramen 1,5. They can also unload the facet joints and provide spinal stability 4.
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Indications
neurogenic claudication secondary to lumbar canal stenosis that is relieved with flexion that has failed conservative treatment 1
salvage/rescue treatment for recurrent neurologic claudication syndrome post-laminectomy, adjacent segment degeneration or spinal stimulator implantation 3
grade I degenerative spondylolisthesis
discogenic low back pain
non-traumatic instability
Contraindications
Contraindications will vary depending on the device but generally include 1:
low back pain without groin, buttock or lower limb radiation
previous spinal fusion or decompression at the target level
severe facet joint hypertrophy requiring resection leading to instability
≥grade 2 spondylolisthesis
spondylolytic spondylolisthesis
severe lumbar scoliosis
Procedure
There are a number of devices available made of varying materials including titanium, silicone and polyetheretherketone (PEEK) 1,4,6:
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motion-preserving devices
static/rigid: made from non-compressible material to ensure consistent spinous process distraction
dynamic/flexible: made from compressible material that can act as a shock absorber during extension
fusion devices: an alternative to pedicle screw and rod fixation when used with other devices for spinal fusion
The technique will depend on the device but the procedure is generally considered minimally invasive 4. Interspinous devices can be implanted as a standalone procedure although some (e.g. Coflex®) are designed to be implanted after spinal decompression 1.
Outcomes
Approximately 33% of patients will develop new or worsening pain and ~15% will require reoperation 5. Short-term (6 months) pain relief and reduction in disability is similar to decompressive surgery but the long-term (2+ year) effectiveness of these devices has yet to be established 5.
Complications
wound complication: ~15% 5
spinous process fracture: ~5% 1,5
device loosening, breakage or migration: ~ 4% 2,5
deep infection: ~1% 5