Minimally Invasive Anterior Cervical Approaches

Gregory Gebauer and D. Greg Anderson

Although the traditional anterior Smith-Robinson approach to cervical disk pathology fulfills many of the goals of a less-invasive surgery, alternative “minimally invasive” approaches have been pursued in recent years. The most frequently performed anterior alternative at the present time is the anterior foraminotomy technique, which can be used to treat cervical radiculopathy without the addition of a spinal fusion.

Classification

The anterior foraminotomy may be considered for cases of radiculopathy, where the pathology is limited to the foraminal zone of one or two levels and does not involve the central canal. Cases with significant myelopathy are best treated with an alternative approach.

Workup

History and Physical Examination

The ideal patient will have primarily arm pain symptoms without major neck pain and no evidence of myelopathy. Following a detailed history regarding the symptoms and general medical history, it is important to perform a detailed neurologic examination. Findings of radiculopathy, including minor deficits of strength and sensation, are common in this population, and the Spurling test will often exacerbate the arm pain. Importantly, there should be an absence of any upper motor neuron dysfunction or long-tract findings. Gait evaluation should also be normal.

Plain radiographs and an advanced imaging study, either magnetic resonance imaging (MRI) or computed tomography (CT) myelography, should be evaluated for findings of neural element compression. On plain films, it is important to ensure that the patient has no findings of kyphosis, which would contraindicate the foraminotomy approach. The advanced imaging study should show compression of the exiting nerve root that correlates to the pain on history and physical examination. It is important that the compression be in the region of the lateral spinal canal and foramen and not in the central canal. Patients with significant compression in the central spinal canal should be managed by an alternative means. Also, a patient with findings requiring surgery at more than two levels should also be managed by an alternative approach.

Treatment

The initial management for cervical radiculopathy should be nonsurgical and may include rest, nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy, traction, and spinal injections. In cases that are recalcitrant to this approach for at least 6 weeks, surgical intervention may be considered. For those with lateral compression and no evidence of deformity, an anterior foraminotomy may be considered.

The approach to the cervical spine is achieved in similar fashion to the standard Smith-Robinson approach. After radiographic confirmation that the correct level has been exposed, the longus colli muscle is dissected and retracted laterally to expose the lateral portion of the disk in the region of the uncovertebral joint. A small retractor is placed between the uncovertebral joint and the vertebral artery and is used to protect the vertebral artery during the procedure. Next, using microscopic magnification, the uncovertebral joint is drilled away until the nerve root is identified and decompressed. Soft disk material can be swept away from the nerve root with a small nerve hook. The nerve hook can also be used to confirm the adequacy of the decompression. Closure of the wound is similar to that in other anterior cervical procedures.

Outcome

For properly selected patients, the anterior foraminotomy should yield good or excellent outcomes in 85% to 98% of patients. This procedure is more technical than the traditional discectomy and fusion approach and should be learned in an appropriate setting.

It is important to protect the vertebral artery during this procedure, and injury may ensue if the artery is not well protected. Excessive drilling of the segment may lead to segmental instability with recurrent pain symptoms, requiring a spinal fusion. All other complications inherent to the anterior approach, such as swallowing problems and vocal cord paralysis, are also possible with the anterior foraminotomy approach.

Suggested Readings

Jho HD, Kim WK, Kim MH. Cervical microforaminotomy for spondylitic cervical myelopathy. Neurosurgery 2002;51(5):S2-54–59

This article describes the technique for anterior microforaminotomy.