Minimally Invasive Spine Procedures — Interventional Pain Consultants

Interspinous Spacer (INSPAN)

Conditions: Lumbar Spinal Stenosis • Neurogenic Claudication • Ligamentum Flavum Buckling • Central Canal Stenosis

An interspinous spacer is a small titanium implant that is placed between the spinous processes — the bony projections at the back of each vertebra — to maintain the spinal canal in an open, neutral position. By preventing narrowing of the spinal canal during standing and walking, the spacer mimics the relief that stenosis patients naturally experience when they lean forward or sit down, providing continuous symptom relief while preserving normal spinal motion.

Lumbar spinal stenosis causes neurogenic claudication because the spinal canal narrows further when a patient stands erect or extends the spine. In this position, the ligamentum flavum buckles inward and the inferior articular facet slides forward, compounding the compression on neural elements. An interspinous spacer gently separates the spinous processes at the affected level, holding the canal open and preventing compression during activities that would otherwise provoke symptoms.

The INSPAN device is a permanent implant designed to withstand the biomechanical forces of the lumbar spine. Unlike fusion devices, the interspinous spacer preserves segmental motion and does not alter the normal kinematics of the spine. Clinical studies have demonstrated sustained improvement in pain, walking distance, and quality of life at 5-year follow-up, with a low rate of complications and reoperation.

Conditions Treated

• Moderate lumbar spinal stenosis with neurogenic claudication
• One- or two-level lumbar stenosis at L2-L3, L3-L4, or L4-L5 levels
• Stenosis symptoms that are relieved by sitting or leaning forward (flexion-relief sign)
• Neurogenic claudication limiting walking distance to less than 2-3 blocks
• Ligamentum flavum buckling contributing to dynamic canal narrowing
• Mild to moderate central canal stenosis without severe foraminal compromise

How It Works

The procedure is performed under fluoroscopic guidance with the patient positioned prone. Following administration of local anesthesia and moderate sedation, a small midline incision (approximately 3-4 centimeters) is made over the affected spinal level. The physician carefully dissects through the subcutaneous tissue to expose the spinous processes and the supraspinous ligament at the target interspace.

Using a series of dilators and sizers, the physician determines the appropriate spacer height and position. The INSPAN device, constructed from titanium alloy with a contoured shape designed to fit between adjacent spinous processes, is then inserted using a specialized delivery instrument. The spacer is positioned posterior to the ligamentum flavum and anterior to the interspinous ligament, effectively holding the spinous processes apart and preventing the canal narrowing that occurs with standing and walking. The device is self-retaining and does not require screws or other fixation.

What to Expect

The procedure is completed in 30-45 minutes under moderate sedation. Patients are positioned prone and receive intravenous antibiotics prior to incision to minimize infection risk. After local anesthetic infiltration, the surgeon creates a small incision and places the spacer under direct visualization and fluoroscopic confirmation. Most patients report a sensation of pressure but not sharp pain during the procedure.

Following the procedure, patients are monitored for approximately 1-2 hours before discharge. X-rays are obtained in the recovery area to confirm optimal implant position. Patients are encouraged to stand and walk before discharge to demonstrate improvement in walking tolerance. Most patients notice immediate improvement in their ability to walk without the familiar leg symptoms.

Recovery

Recovery from interspinous spacer placement is rapid because the procedure avoids bone removal, muscle stripping, and general anesthesia. Patients are instructed to avoid heavy lifting, twisting, and bending at the waist for 4-6 weeks to allow the soft tissues to heal around the implant. Light walking is encouraged from the day of surgery and is the primary activity during the early recovery period.

Most patients return to desk work within 1-2 weeks and to full activity within 4-6 weeks. Physical therapy is typically initiated at 4-6 weeks to strengthen the core and paraspinal muscles. The spacer is permanent and does not require replacement. If symptoms recur at a different level in the future, the same procedure can be performed at the new level without affecting the existing spacer.

Clinical Considerations

Ideal candidates have moderate lumbar spinal stenosis at one or two levels with a clear flexion-relief pattern — symptoms that are predictably relieved by sitting or leaning forward. Patients with severe fixed stenosis, significant spondylolisthesis (greater than Grade I), scoliotic deformity, or prior fusion at the target level are not good candidates. The procedure is contraindicated in patients with active infection, osteoporosis with vertebral fracture risk, or allergy to titanium.

At Interventional Pain Consultants, we perform thorough preoperative evaluation including standing and supine MRI to assess both fixed and dynamic components of stenosis. We review each patient's imaging, clinical presentation, and response to conservative therapies to determine whether an interspinous spacer is the optimal treatment choice for their specific pattern of lumbar spinal stenosis.