Posterior Cervical Foraminotomy

Background

Cervical disc protrusions, if they compress the nerves in the neck typically cause arm pain. There are a number of operative ways that this can be managed but, if suitable, a posterior cervical foraminotomy is a vastly under-rated operation which avoids some of the shortcomings of other disc operations and yet still has an excellent outcome in terms of symptom relief, in a minimally invasive fashion.

 The typical patient presents with pain down one arm which may radiate to the hand. Cervical disc problems are exceedingly common and it is important to realize that in the vast majority of cases non-operative management works very well. Most patients settle within 6-12 weeks after the onset of symptoms. The pathophysiology of why a patient gets symptoms is disc protrusion is complex, as not all disc patients get pain.

A posterior cervical foraminotomy is a minimally-invasive procedure designed to enlarge to space through which the nerve root exits from the spinal cord (the so-called neural foramen) and at the same time try to remove any piece of disc which is pushing on the nerve. Interestingly, sometimes the foraminotomy alone can alleviate symptoms without a discectomy being needed. The whole disc is not removed, just the fragment pressing the nerve root. A fusion is not performed and most patients typically do not require a neck collar after the surgery.

A disc protrusion per se may not cause symptoms. If the annulus is acutely torn, neck pain may result, but the management is usually not operative. If the disc pushes on a nerve, as shown in the previous  scans, then symptoms down one or occasionally both arms may result. The symptoms can include pain, numbness, “pins and needles”, and weakness.

Anatomy

The anatomy of a typical intervertebral disc as shown below:

(Below): The intervertebral disc lies in front of the spinal nerves and is situated between the vertebral bodies. It carries 80% of the load transmitted through the neck and is the shock absorber for the spine. The lowermost discs of the neck (C56 and C67) are most prone to wear and tear and potential rupture.

Note that there is an outer shell, called the annulus fibrosis and an inner core called the nucleus pulposus. The annulus is the consistency of a pencil eraser, whereas the nucleus is gel-like and, as we get older, dehydrates and becomes like crabmeat. The discs act as shock absorbers and flexing the spine loads the disc. A tear in the outer annulus can consequently cause severe neck pain. Once an annular tear occurs, it may heal, or it may allow nucleus to come out of the centre of the disc, into the spinal canal, where it may compress nerves. This is usually called one of a number of terms, including “disc prolapse”, “ruptured disc”, “slipped disc”,  “extruded disc” etc etc.  All these terms essentially mean the same thing. Once nerves are compressed, surgery may be complicated. It is important to know that the prolapsed disc cannot be pushed back into place and nothing but time will heal the annular tear. Thus, in general, any surgery using this approach is aimed at improving the arm pain, not the neck pain.

Reason For Operation

Cervical disc protrusions are not usually operated upon early, but there are some clear situations when a surgeon may recommend early surgery. If there is evidence of severe weakness, early surgery may be offered. If the pain in the arm is so severe that narcotic analgesia is not controlling the pain, early surgery may again be an option. Finally, if there is a suggestion of spinal cord compression, and myelopathy, early surgery is advocated. A posterior cervical foraminotomy is not the operation of choice if a disc protrusion is causing myelopathy as this typically indicates that the compression of the spinal cord is from disc material in front of the cord. Consequently, a posterior approach such as for a cervical foraminotomy is not suited for spinal cord compression and myelopathy.

If a patient has pain, but it is not too severe, then typically conservative management is initiated. It must be remembered that the vast proportion of patients will settle with time and as long as improvements are noted at 6 weeks, there is minimal or no weakness, and the pain is not excruciating and is livable with oral analgesia, then waiting and continuing with conservative therapy is a good option.

If weakness occurs and is not improving, surgery is usually offered. Similarly, if symptoms are not improving at 6 weeks then surgery is an option.

In most cases, when managing just arm pain, surgery is a treatment option that speeds up the rate of recovery, remembering that most cases will get better by themselves. Again, specific recommendations are tailored to the patient. In the vast number of cases, the goal is control of pain, and any intervention that achieves this and is less invasive than surgery is a reasonable option.

 Technique

If surgery is undertaken, it is usually performed as a minimally-invasive procedure. The procedure can be performed as a day stay surgery, but most patients stay in hospital for 1-2 nights. General anesthesia is utilized and the surgery is performed through an incision of 2-4 cm. Much emphasis is placed on performing the surgery through tiny incisions. Usually a small window is made on one side of a spinous process, at the junction of the lamina and facet joint, through the removal of some bone and ligament to allow visualization of the  involved root. Using a high speed drill and microinstruments, once the nerve root affected is identified, the whole out of which the nerve passes is enlarged. This is the foraminotomy. (see below):

                                      nerve root exposed      bony drilling       lamina

The amount of bony removal (in red) is shown below:

The nerve root is then gently elevated and if there is a disc bulge this is palpated. If identified, the disc bulge is incised and typically a tiny piece of disc is removed. The whole disc is not removed. The operation is then complete and after placing cortisone over the nerve root, closure is effected, typically, with dissolving sutures for skin. Typically this takes 1-2 hours to perform.

             (Above): A preop and postop CT to shoe the extent of bone removal (arrowed) in order to effect an adequate foraminotomy.

Risks

The greatest risk is injury to one or more nerves or spinal cord and this is typically 1-2%. The risks of infection, bleeding etc. etc. are similar to those for a any other spinal operation as are the risks of general complications. A small proportion of patients will have a recurrent disc protrusion, either at the same side and level or at different levels or the opposite side. This operation will not alter the future likelihood to get neck pain.

 The small but real risks from surgery are the reason why all patients with disc protrusions do not immediately have surgery.

Expectations

In uncomplicated cases the likelihood of good/excellent relief of arm pain is 80-90%. Numbness is slow to recovery and may persist. Weakness also may take 6-12 weeks to return to normal. Pins and needles usually starts to improve immediately.

 Recovery

  After surgery, patients are monitored on the ward overnight. A soft collar is worn for comfort if desired, and typically patients are discharged within 1-2 days. At home, for the first 6 weeks, nothing greater than 5-10 lbs must be lifted and after this a return to normal activities can be effected. The sutures do not require removal and dissolve with time.

Non-Surgical Options

Despite the length discussion about surgery, most patients get better without surgery.

Conservative therapy comprises

·        Analgesia with NSAIDs (e.g. Mobic, Voltaren or Celebrex)

·        Analgesia with other medications such as Tramadol

·        Avoidance of bending/lifting and ergonomics at work

·        Physiotherapy (traction may help)

·        Perineural steroid and local anesthetic injections (these can be very helpful)

·        Possibly acupuncture

 Other Points

A posterior cervical foraminotomy is an excellent operation for the patient with arm symptoms secondary to a cervical disc protrusion that avoids implantation of foreign devices and spinal fusion. Not all patients are suitable for this operation but those who are generally do very well.