Posterior Cervical Foraminotomy

MIS: Tim Eugene Adamson
Open: Andrew C. Hecht and Steven Joseph McAnany

12.1 Introduction

Various surgical techniques have been described for the treatment of cervical radiculopathy. The surgeon must choose between an anterior or posterior approach based on the nature of the pathology and comfort level with a particular approach. The anterior approach to the cervical spine was first pioneered by Smith and Robinson 1 and was later modified by Cloward.² Multiple modifications over the years, including allografts, cages, and fixed and dynamic plating, have led many to consider it the gold standard for the treatment of cervical disc disease.

The use of a posterior approach for the treatment of cervical radiculopathy originated more than 65 years ago. Mixter was the first to report on the use of a posterior approach for the treatment of a cervical disc herniation.³ The posterior cervical foraminotomy (PCF) was pioneered by Scoville et al and Frykholm.^4,5 In the 1980s, case series by Fager, Casotto, and Epstein et al popularized the so-called “key-hole” laminoforaminotomy with a success rate approaching 90%.^6,7,8 More recently, Jagannathan et al⁹ found a 95% success rate in the resolution of radiculopathy. In spite of a proven track record of success with a favorable complication profile, anterior cervical discectomy and fusion (ACDF) remains a more popular procedure. Ruetten et al¹⁰ showed that when treating radiculopathy alone, PCF and ACDF produce clinically equivalent results, as measured by visual analog scale, Hilibrand’s criteria, and the North American Spine Society Instrument. Similarly, Wirth et al¹¹ demonstrated similar results, finding no significant differences in surgical complication rates or postoperative symptom relief between the two approaches.

Advantages of the posterior approach include better access to posterolateral-directed herniations, no risk for pseudarthrosis or graft subsidence, and decreased risk of iatrogenic kyphosis.^9,12 The complications reported with this approach include nerve root injury, dural tear, spinal cord injury with and without K-wire misplacement, same-segment and adjacent-segment syndrome, and spinal instability.^13,14,15

The posterior laminoforaminotomy was initially developed as a midline approach, utilizing a subperiosteal lamina dissection to minimize bleeding. The open approach allows for excellent visualization and access to lateral disc herniations and bony foraminal compromise secondary to cervical spondylosis. Opponents of the open PCF cite postoperative neck pain and spasm as a disadvantage of the procedure. The development of the operative microscope resulted in a further refinement in technique but the traditional midline subperiosteal approach remained the same. In 1997, Foley and Smith introduced the lumbar microendoscopic discectomy technique and the muscle-splitting tubular retractor system.¹⁶ As an alternative to these standard open approaches, endoscopic and minimally invasive techniques have been developed. Minimally invasive surgery (MIS) techniques allow for shorter hospital stays, same-day surgery, faster recovery times, and reduced blood loss.^13,17,18 Minimally invasive foraminotomy is an increasingly relied upon means of foraminal decompression, but whether it is superior to the open technique remains a matter of debate.

12.2 Indications for Posterior Cervical Foraminotomy

The management of cervical radiculopathy remains a controversial area within spine surgery. PCFs are typically indicated for patients with cervical radiculopathy due to foraminal stenosis that is refractory to at least 6 weeks of conservative management.

The posterior laminoforaminotomy is best utilized in the treatment of foraminal lesions or cases of posterolateral soft disc herniation that compresses the nerve root while lying lateral to the cord. The primary contraindications to PCF include segmental kyphosis or instability at the operative level. A relative contraindication to PCF is the presence of clinical or radiographic myelopathy or myelomalacia. A summary of the literature for open and MIS PCF can be found in Table 12.1.

Fig. 12.1 (a) Sagittal and (b) axial T2-weighted magnetic resonance images demonstrating a left-sided disc osteophyte complex at C7–T1 causing severe foraminal stenosis with compression of the exiting C8 nerve root.

12.3 Advantages of the Minimally Invasive Surgery

All minimally invasive spinal surgery techniques, and especially those involving the cervical spine, result in less muscle damage and disruption than the traditional open techniques. By eliminating the subperiosteal dissection that detaches the muscular insertions on the posterior spinal elements and secondary denervation, the MIS approach, utilizing a muscle-splitting dilatation technique, results in less acute muscle injury and its consequences as well as less chronic muscular denervation, atrophy, and alteration to long-term cervical biomechanics.

Multiple studies have demonstrated a significant difference in the early indicators of muscle damage between open and MIS lumbar techniques focusing on the serum CPK (creatine phosphokinase) levels, which directly reflect the degree of muscle damage. In the cervical spine, this has also been shown to correlate with lower rates of postoperative pain, narcotic use, length of hospitalization, and wound infections. As would be expected, the same laminoforaminotomies done through different muscle approaches (MIS vs. open) have similar results for relief of radiculopathy.

Postoperative imaging more than 1 year after surgery reveals that the amount of long-term muscle change is markedly different between the two approaches. Unilateral atrophy of the multifidus muscle is not uncommon following an MIS approach given the direct disruption necessary to expose the lateral lamina and medial facet, but the more superficial musculature does not appear to be damaged. Following the subperiosteal dissection associated with an open approach, not only is the multifidus muscle directly affected, but also there is long-term atrophy of the semispinalis and more superficial musculature. The impact of this long-term asymmetry and potential change in function has not been studied in any detail.

12.4 Advantages of Open Surgery

The benefits of the open PCF have been detailed above. The posterior approach to the cervical spine is well known to most spinal surgeons. This familiarity provides the main benefit over the MIS technique, as it allows surgeons to avoid the steep learning curve that is associated with mastering an MIS approach. In addition, complications that are unique to the MIS approach include misplacement of the percutaneous Kirschner wire or Steinman pin, medial migration of the tubular retractor with injury to the spinal cord or nerve roots, and lateral migration of the tubular retractor with damage/injury to the exiting nerve root or vertebral artery.

12.5 Case Illustration

A 55-year-old man presented with a 1-year history of left arm pain, weakness, and paresthesias that have failed to respond to conservative treatment including physical therapy, NSAIDs (nonsteroidal anti-inflammatory drugs), and injections. Magnetic resonance imaging (MRI) revealed a C7–T1 posterolateral disc herniation with significant foraminal stenosis and compression of the left C8 nerve root ( Fig. 12.1). Surgical intervention was recommended to decompress the affected nerve root.

12.6 Surgical Technique in Minimally Invasive Surgery

Following the induction of anesthesia, the bed is positioned so that the operative side is away from the anesthesia equipment. The patient is then placed in a sitting or semirecumbent position utilizing a Mayfield-Kees head holder. The patient’s blood pressure is carefully monitored as the back is elevated and the lower legs flexed to accomplish a “lounge chair” position. This allows the head to be positioned neutrally with respect to rotation and flexion. The posterior cervical region is positioned vertically and the head holder securely locked in place. The fluoroscopy arm is then brought in from the foot of the bed and positioned to allow a true lateral image. The posterior neck is then prepped and draped with a disposable cranial incise drape to take advantage of the drainage pouch. The fluoroscopy arm is draped into the field so that imaging can be obtained at any point during the procedure.

The target level is initially localized by placing a spinal needle lateral to the neck and checked fluoroscopically. The needle is then repositioned one fingerbreadth off of midline to the affected side and introduced through the skin. Fluoroscopy is then used to monitor the trajectory as the needle is introduced to the middle of the lamina cephalad to the targeted disc space. The ideal trajectory is to angle slightly cephalad from the skin to the lamina. Once the bone is contacted and localization confirmed with fluoroscopy, the needle is removed and a 16- to 18-mm incision sharply incised. It is optimum to obliquely angle this to take advantage of the Langer line anatomy. A K-wire is then introduced through the skin incision and positioned back along the needle trajectory with fluoroscopic guidance. Positioning this in the middle of the cephalad lamina is the safest and avoids the potentially dangerous interlaminar space. Once confirmed to be on the lamina, the first dilator is passed over the wire to the bone, and the wire is then removed. The first dilator is then used to create a pocket of subperiosteal dissection, which makes the initial soft tissue steps much easier once the cylinder is in place. Before progressing to the next dilators, the superficial and deep fascia layers are relaxed by spreading a pair of scissors or a hemostat along the outside of the first dilator. The remaining dilators are then used to introduce the operative cylinder to the back of the lamina and then positioned caudally with fluoroscopic confirmation until they are centered over the target disc space before anchoring to the table-mounted arm.

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