Interspinous Spacing Devices



  • Synonyms: Interspinous posterior decompression, interspinous distraction device, interspinous spacer device (ISD), interspinous implant

  • Dynamic stabilization alters movement & load transmission of spinal motion segment without fusion of segment

  • Interspinous spacing device places stenotic segment in slight flexion while preventing extension


  • Radiographs & CT helpful to evaluate interspinous location

    • Assess for fractures


  • Lumbar neurogenic claudication symptoms are exacerbated during extension, relieved during flexion

    • Dimensions of canal & foramen ↑ in flexion, ↓ in extension

    • Facet loading ↑ during extension, ↓ during flexion

Clinical Issues

  • ISD helpful for treatment of spinal stenosis with neurogenic claudication

    • Causes focal flexion at applied level, resulting in increased canal & foramen dimensions

  • Complications

    • ISD malposition, migration, dislocation, spinous process fracture

  • Indications

    • Lumbar stenosis ± facet joint hypertrophy & subarticular recess stenosis, foraminal stenosis

    • 1- to 2-level lumbar stenosis from L1-L5 in patients with at least moderate impairment in function

  • Patients anatomy may influence outcomes

    • Decreased accessible distance between laminospinous plane and tip of spinous process

  • Osteoporosis is contraindication

X-Stop implants at L4-L5 & L5-S1 are titanium alloy devices placed between spinous processes to reduce canal & foraminal narrowing that occurs in extension, thus reducing the symptoms of neurogenic intermittent claudication.

Sagittal bone CT shows an interspinous spacing device (ISD) , which may increase the foraminal area & height as well as spinal canal diameter in extension. ISDs may improve recurrent facet joint pain in clinical short- and midterm settings but do not exceed outcome of denervated patients.

Sagittal T1WI MR shows the susceptibility artifact from the ISDs . X-Stop is the most commonly used ISD in patients with neurogenic intermittent claudication due to lumbar stenosis.

Axial CT myelographic image of spinous process fractures at 2 levels following placement of X-Stop devices for canal stenosis shows fractures through the L4 spinous processes . Note the overlap of the wings of the adjacent level devices .

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