Interspinous device

Implantation of interspinous devices is one option for treating lumbar canal stenosis.

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. 

There are a number of devices available with^1,4:

• motion-preserving devices
  • static/rigid: made from non-compressible material to ensure consistent spinous process distraction
  • dynamic/flexible: made from deformable material that can act as a distinction made between static and dynamic devices. Dynamic devices can compressshock absorber during extension while also allowing
• fusion devices: an alternative to pedicle screw and rod fixation when used with other devices for flexion ¹. spinal fusion

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 level disease orsegment degeneration or spinal stimulator implantation ³
• grade I degenerative spondylolisthesis
• discogenic low back pain
• nontraumatic instability
• facet syndrome⁴

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
• compression fracture
• severe facet joint hypertrophy requiring resection leading to instability
• ≥ grade≥grade 2 spondylolisthesis
•  spondylolyticspondylolytic spondylolisthesis
• severe lumbar scoliosis
• osteoporosis

Procedure

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. Some

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 (e.g. Superion) canhas yet to be implanted percutaneouslyestablished ¹⁵. 

Complications

• wound complication: ~15% ⁵
• spinous process fracture: ~5% ^1,5
• device loosening, breakage or migration: ~ 4% ^2,5
• deep infection: ~1% ⁵