With degenerative disc disease, a cervical disc loses its mechanical strength as a response to pathology. The disc then begins to herniate or protrude out of its intervertebral space. If the disc material protrudes far enough, it can press against spinal roots or directly onto the spinal cord, producing pain and other symptoms that often require surgery to correct. The aim of surgery is to remove the compressive force on neural, or nerve-containing, tissues and then stabilize the vertebrae.
Cervical Discectomy
Surgeons usually perform surgery when nonsurgical approaches fail to relieve disease symptoms and when these symptoms become severe, according to the Mayfield Clinic. Generally, surgery is of two types: open and minimally invasive. Minimally invasive surgeries require endoscopic techniques. Discectomy focuses on removing the disc material partially or in its entirety so that neural tissues can decompress. Surgeons can approach cervical discectomy from the posterior or the anterior aspect of the body, but according to the Academy of Orthopaedic Surgeons, the preferred approach is from the anterior side. Sometimes surgeons must remove more than one intervertebral disc.
Cervical Vertebral Fusion
When a surgeon removes an intervertebral disc, a patient's disc space is left with a void. Without the disc cushion in between, the vertebral bones are unstable. Also, two bones mechanically rubbing together with no interposing cushion can produce pathology. Therefore, the remaining vertebrae require fusion, according to the American Academy of Orthopaedic Surgeons.
To encourage fusion of the vertebrae, a surgeon can graft bone chips from the patient's pelvis into the intervertebral space. Another technique is to use bone tissue taken from cadaver donors. These grafts promote the migration of a patient's bone cells into the intervertebral space. In time, the graft and new bone cells integrate, resulting in fusion of the opposing vertebral bones. The vertebral bones must remain stationary for fusion to occur, however. If they do not, a pseudarthrosis, or nonunion, results. Keeping the bones stationary requires the use of immobilizing hardware, including rods, plates and screws, to hold the bones in place.
Cervical Disc Replacement
Spinal fusion is a complex surgical process that is sometimes unsuccessful, according to the BlueCross BlueShield Association. It also results in immobility between two or more vertebrae, which can put stress on the remaining vertebrae to compensate for the immobility. Compensation can lead to degenerative disease in the remaining discs. A relatively new procedure called artificial intervertebral disc arthroplasty circumvents these disadvantages of spinal fusion and replaces a degenerated disc with an artificial one.
The surgical procedure for disc replacement is nearly identical to that of discectomy, according to the BlueCross BlueShield Association. The primary difference is that the patient requires neither intervertebral fusion nor permanent fixation hardware in a disc replacement. Having a disc between the vertebrae also eliminates significant complications that can occur with spinal fusion, according to the BlueCross BlueShield Association. Disc replacement eliminates the risk of hardware complications, such as screw fracture and tissue injury that can result from the hardware. Disc replacement also avoids the complication of degenerative disc disease developing above and below the fusion site. The artificial disc allows for natural movement down the spinal column and distributes forces evenly.
