Minimally Invasive Posterior Cervical Foraminotomy

Grant D. Shifflett

Frank M. Phillips

REBUTTAL ▪ The Case against MIS Posterior Cervical Foraminotomy

Jesse E. Bible

Joon Y. Lee

INTRODUCTION

Brief Description of Standard Open Technique¹

An open posterior cervical foraminotomy (PCF) typically utilizes a standard midline incision for bilateral or unilateral foraminotomies. The lamina, the facet joint-laminar junction, and the facet joint are typically exposed while taking care to preserve the facet joint capsule. A high-speed cutting burr in combination with Kerrison rongeur may then be used to resect the inferior and superior articular processes, affording a view of the underlying nerve root. If a diskectomy is to be performed, the nerve root may then be gently retracted to gain access to the disk fragment, which may be removed with a nerve hook and pituitary rongeurs.

Potential/Theoretical Problems with Current Open Technique

Larger incisions with more extensive periosteal muscle dissection may result in increased neck pain, spasm, and discomfort and ultimately a delayed recovery.², ³, ⁴, ⁵

Figure 13.1 A 43-year-old male firefighter with the chief complaint of left radial forearm, thumb, and index finger paresthesias and pain. (A) Lateral radiograph demonstrating mild multilevel spondylosis and maintenance of the normal cervical lordosis. (B) and (C) Magnetic resonance imaging (MRI) axial and parasagittal reconstructions show a left paracentral disk herniation with compression of the C6 nerve root.

TECHNIQUE

Relevant Anatomy

Musculature of the posterior cervical spine can be described in three layers¹,⁶:

Superficial: trapezius
Intermediate: splenius capitis, splenius cervicis
Deep: erector spinal muscles (iliocostalis, longissimus cervicis, longissimus capitis, semispinalis cervicis, semispinalis capitis), multifidus, rotatory muscles

Anatomic Working Zone

The structures bordering the neuroforamen include:

Ventrally: disk and uncovertebral joint
Dorsally: superior articular facet of the caudal segment
Inferiorly: caudal vertebra pedicle
Superiorly: cranial vertebra pedicle

Figure 13.2 A 48-year-old woman presented with acute onset, isolated right ulnar forearm and pinkie pain and paresthesias with no axial neck pain. (A) Lateral radiograph demonstrating mild spondylosis and some mild flattening of the normal cervical lordosis. (B) and (C) MRI axial and parasagittal reconstructions at the C7-T1 level demonstrating a large right-sided paracentral disk herniation extending into the neural foramen with compression of the C8 nerve root.

Step-by-Step Technique

Patient Positioning

The patient is placed in prone position on a radiolucent table. Three-point Mayfield head clamp is affixed to the patient’s head and positioned in a slightly flexed posture. The head may be elevated with reverse Trendelenburg positioning to reduce bleeding in the field. Care must be taken to ensure there is no pressure on bony prominences, particularly the face and the eyes.

Surgical Approach

Under lateral fluoroscopic guidance, an incision is made approximately 10 mm off the midline on the operative side. Lateral fluoroscopy will help the location of the incision to determine an appropriate trajectory to the disk space. The authors avoid “blind” advancement of instruments or retractors to the posterior spine. After the skin incision is made, monopolar electrocautery is then used to split the cervical fascia proximally and distally. Using finger palpation, the spinous process and lamina and lateral mass can be palpated. With finger guidance, serial dilators from the tubular retraction system are then used to establish the appropriate docking point centered over the lamina-facet junction at the treatment level and confirmed fluoroscopically.
The appropriately sized tube (typically 16 to 18 mm) is then placed over the dilators, which are then removed. A table-mounted flexible arm retractor system is then connected to the tubular retractor stabilizing the docking point. A high-powered surgical microscope is then brought into the surgical field.

Decompression

Residual soft tissue over the facet joint is removed using rongeurs and monopolar electrocautery. The bony “V” representing the lamina-facet junction is then visualized, and bony edges are defined with a microcurette. A small-angled curette is then used to dissect the underlying ligamentum off the cranial lamina to delineate the bony landmarks. A small (2 or 3 mm) Kerrison rongeur is then utilized to perform a partial hemilaminectomy, allowing visualization of the lateral edge of the spinal canal and medial aspect of the exiting nerve root. A high-speed drill is then used to remove the medial portion of the inferior articular process, followed by the superior process overlying the nerve root. The foraminotomy is completed using a small Kerrison rongeur (1-mm footplate) or microcurettes. A small nerve hook may be used to palpate the superior and inferior pedicles, which represent the cranial and caudal extents of the decompression. Free passage of the nerve hook laterally into the neural foramen ensures an adequate decompression has been performed. When a soft-disk herniation is present, the corresponding cervical nerve root may be gently retracted, affording visualization of the disk fragments, which may be removed with a nerve hook and small pituitary rongeurs.