50 Lumbar Foraminotomy (MIS)

Ali A. Baaj and Juan S. Uribe

I. Key Points

– Removing more than one-third of the medial facet joint when performing a foraminotomy could lead to instability.

– The combination of a high-speed drill and small-caliber Kerrison rongeur should be utilized to safely perform a foraminotomy.

– Foraminal stenosis and nerve root compression are the result of hypertrophy/degeneration of the superior articulating facet of the lower vertebra.

II. Indications

– Focal lateral recess and/or foraminal stenosis

III. Technique

– The patient is placed in the prone position.

• A Wilson radiolucent frame is adequate if no fixation is planned.

– Fluoroscopy is utilized for localizing the level of the foramen.

– A paramedian 2 to 3 cm incision is made 1 cm lateral to the midline.

– The fascia is incised with a monopolar cautery.

– Serial dilators and a nonexpandable tube retractor are placed under fluoroscopic visualization.

• The optimal arrangement is to dock the dilator/tube retractor on the inferior aspect of the lamina of the superior level. For example, for a L4/L5 foraminotomy, the tube is positioned on the inferior aspect of the L4 lamina.

• This approach is similar to that of minimally invasive surgery (MIS) for microdiscectomy

– The operative microscope is brought over the field.

• This is optional, but the microscope provides for better illumination and visualization through the tubular retractor.

– The inferior aspect of the lamina is drilled until the underlying ligamentum flavum is visualized.

– With the use of nerve hooks, curettes, and Kerrison rongeurs, the ligamentum flavum is resected.

– The traversing nerve root is typically visualized at this point.

IV. Complications1

– Cerebrospinal fluid (CSF) leak (<5%)

• Technically challenging to repair primarily through the MIS tube

– Nerve root injury (<1%)

– Wound infection (<1%)

V. Postoperative Care

– Mobilize early without brace.

– Discharge to home when patient meets discharge criteria.

• Typically same day or postoperative day 1

VI. Outcomes

– The presumed benefits of MIS foraminotomy include reduced blood loss, less tissue damage, and shorter hospital stays. However, no randomized trial has compared traditional open with MIS foraminotomy.

VII. Surgical Pearls

– Leaving the ligamentum flavum intact until all the “bony work” is completed protects the dura during drilling and when the Kerrison punches are in use.

– Aggressive drilling of the facet to remove more than one-third may lead to facet joint instability.

– Patients whose history and exam findings of radiculopathy correlate with the foraminal stenosis seen on imaging will likely have the best outcomes from this procedure.

Related posts:

Tumors of the Spine Transpedicular Approach Posterior and Transforaminal Lumbar Interbody Fusion (PLIF/TLIF) (Open) Surgical Resection of Spinal Vascular Lesions Physical Examination Retroperitoneal Approaches to the Thoracolumbar Spine

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