Cervical Spine (Neck) Surgery

The intervertebral disc of the cervical spine is critical for normal motion and function of the neck. Degenerative changes of the disc may cause a desiccated piece of the disc to extrude through a tear in the back of the disc and compress a nerve root. Also, a focal bone spur formed through the degenerative process may compress a nerve. If non-operative treatment does not result in relief of neck and arm pain from the compressed nerve, surgical decompression is indicated. 

Standard Surgical Procedure 

The standard surgical procedure approaches the cervical disc from the front with removal of the entire worn-out disc and elimination of the compression on the nerve. A fusion is usually then performed to stabilize the motion segment. A bone graft is placed between the vertebral bodies where the degenerated disc was removed. 
This is a highly successful operation, however, limitations exist because of the fusion procedure. An increased incidence of degeneration of the disc above and below the fusion occurs due to the increased forces on the adjacent motion segment. Bone graft is required either from the patient's own iliac crest, or from cadaver bone. And finally, immobilization is required postoperatively with a cervical collar, an internal plate and screws, or both.

Cervical Artificial Disc Replacement 

A cervical artificial disc replacement is a device that is placed into the intervertebral disc space instead of a bone graft after the disc is removed with the goal of retaining as much normal motion as possible while keeping the motion segment stable. The theoretical advantages are to reduce the incidence of adjacent segment degeneration while maintaining normal neck motion, the elimination of bone graft donor site complications and possible disease transmission from donor bone graft, and early neck motion without bracing requirements. 

There are a number of Cervical Disc Replacement devices that have shaped the scene we have currently. The Bryan Disc made significant advances into understanding cervical motion preservation surgery. It is however somewhat obsolete now and is not being utilised as commonly (see figures 1,2 and 3).

There is the Synthes Prodisc C (see Figures 4,5 and 6) and perhaps the most stringently tested of them all, the SpinalKinetics M6-C (Figures 7 and 8)

Click here for a full range of current cervical disc replacements

Figure 1. The Bryan disc

Figure 2. Bryan disc in neck flexion

Figure 3. Bryan disc in neck extension

Artificial Cervical Disc Replacement - PCM 

The Prodisc-C (made by Synthes Spine) is similar to the lumbar version of the Prodisc. It consists of two metal plates each made of cobalt chrome. Extending from the upper and lower part of each plate is a metallic fin. The two plates ride on a UHMWPE insert that is fixed to the lower plate. The Prodisc-C allows for a range of motion within a specific range as allowed by the prosthesis. The endplates are sprayed with a titanium layer to promote bony in-growth, which helps the device stay firmly in place. The Prodisc-C is currently in clinical trials in the U.S.

Figure 4 Prodisc-C

Figure 5 Prodisc C in neck flexion

Figure 6 Prodisc C in neck extension

The M6 artificial cervical disc offers an innovative option for artificial cervical disc replacement because of its unique design which is based on a natural disc’s qualities.

Engineered to replicate your own disc, the M6 is the only artificial disc that incorporates an artificial nucleus (made from polycarbonate urethane) and a woven fiber annulus (made from polyethylene). The M6 artificial nucleus and annulus are designed to provide the same motion characteristics of a natural disc.

Together, the M6’s artificial nucleus and annulus provide compressive capabilities along with a controlled range of natural motion in all 6 degrees of freedom along each vertebra. This “natural” motion is designed to provide the freedom to move your neck naturally while minimizing the stress to adjacent discs and other important spinal joints.

The M6 has two titanium outer plates with keels for anchoring the disc into the bone of the vertebral body. These outer plates are coated with a titanium plasma spray that promotes bone growth into the metal plates, providing long term fixation and stability of the disc in the bone.

Artificial Disc Components



Artificial Nucleus

Artificial Annulus

Sheath

Fixation

Please click here for information on the Investigational Device Exemption (IDE) Study on the M6-C device
Please click here for information on the M6-C movements (kinematics)
Please click here for information on more movement characteristics of the M6-C disc replacement
Please click here for information on Clinical and Radiologic Outcomes of the M6-C device

Figure 7 Spinal Kinetics M6-C in neck flexion

Figure 8 Spinal Kinetics M6-C in neck extension

All these devices and more are readily available for use in the USA and parts of Europe but for on-label use for 1-2 levels.

In Australia, the Federal Government has finally allocated a Medicare rebate code for the use of SINGLE level disc cervical disc replacement.

The results long-term for these devices are pending and the risk of adjacent level deterioration is still not proven to be lower for these devices over the Gold Standard fusion, Anterior Cervical Discectomy and Fusion (ACDF).

Time will tell.

Dr Pope prefers to use the M6-C as his preferred device and has no affiliations with the company, suppliers and does not receive royalties, retainers, fees or any financial incentives to utilize the device.

Dr Pope is trained extensively to implant all of the above mentioned devices including others to the strictest of regulatory standards and is approved by the respective companies as an accredited trained surgeon to safely implant their devices.

Please click here to access Dr Pope’s review article on Disc Replacement Surgery in Volume 11, Edition 2 of the GP News 2011

Please click here for the recent evidence for Cervical Disc Replacement.