Anterior Cervical Discectomy and Fusion

OVERVIEW

Anterior Cervical Discectomy and Fusion, commonly referred as ACDF, utilizes a anterior approach to decompress (remove impingement) from the spinal cord, and the exiting nerve roots at the levels that are compromised. The cervical vertebral bodies (bones of the spine) are fused together using an interbody technique. Typically, an incision is made in the front of the neck and is usually no longer than 2 to 3 inches, depending on the number of affected levels. Discectomy is a surgical technique used to remove one or more herniated or diseased discs. This technique relieves neck pain as well as radiating pain down the arms by relieving the pressure from the spinal cord and exiting nerve roots.

Following discectomy, a bone graft is placed in the empty disc space for support and stability (the interbody fusion). ACDF is preferably also used in patients whose neck is affected by kyphosis (forward cervical curve) due to disc degeneration. The goal of the procedure is to bring the neck back into normal alignment to recreate a normal ‘lordotic curve’ as well as to decompress the spinal cord and the adjacent nerve roots, previously subject to irritation. The subsequent bone-healing across the fusion is encouraged by securing a thin metal plate with screws over the vertebral column to stabilize the affected levels.

WHY ACDF?

ACDF is commonly performed for a variety of painful spinal conditions, such as:

SURGICAL PROCEDURE -STEP BY STEP-

INCISION MADE

                                                               

A 2-3 inch incision is made in the front of the neck.

(The size of the incision varies depending on the number of affected levels.)

                                                                                                    

DISC ACCESSMENT AND REMOVAL

                                                                              

After the incision is made (typically on the left side of the neck), the cervical spine is exposed and the levels are assessed. Occasionally, bone spurs are removed first, after which a special retractor is placed to safeguard the esophagus and trachea (windpipe with the voice-box) medially, and the blood vessels and nerves to the head and brain laterally. The effects of the diseased disc(s) on the spinal cord and adjacent nerve roots are then easily seen and the disc is removed in its entirety (complete discectomy). A fusion is then necessary.

After remaining pressure is removed from the spinal cord and the exiting roots, often by using a specialized high-speed burr (50,000RPM), the opening between the vertebral bodies above and below the opened disc space need to be restored. This is accomplished with a plastic cage, or a structural bone graft, placed into the empty disc space. The bone graft restores spine stability and realigns the vertebral bones. In addition, the graft relieves pressure on nerve roots and the spinal cord, by keeping the nerve tunnels between the bones open.

There are several types of bone grafts used in the anterior cervical spine:

DISC REMOVED

  • Autograft - bone obtained from the same individual receiving the graft. Bone can be harvested from non-essential bones (spinous process), or from the iliac crest (pelvis).
  • Allograft - bone is derived from humans, but is not harvested from the individual receiving the graft. Allograft bone is taken from cadavers that have donated their bones to a source called the bone bank. Allograft is a safe option as there are strict rules and regulations preventing any potential risk of diseasr transmission. Additionally, the bone banks are also regulated by the U.S. Food and Drug Administration (FDA). There are typically no live cells or tissue associated with the allograft bone: it merely functions as a scaffold that gets replaced by the patient's own bone over time.
  • Synthetic graft - bone that is artificially created from ceramics such as calcium phosphates. The material can be dipped in growth factors or patient's bone marrow to promote biological activity and improve healing (fusion).
                                                                              

Bone graft also possesses important characteristics, depending on it's type.

  • Autograft
    • Osteogenic - osteoblasts contribute to new bone growth.
    • Osteoinductive - osteoprogenitor cells are stimulated to differentiate into osteoblasts to begin new bone formation.
  • Allograft
    • Osteoconductive - the bone material serves as a scaffold for new bone growth that is perpetuated by the native bone. Osteoblasts from the margin of the defect that is being grafted utilize the bone graft material as a framework upon which to spread and generate new bone.
  • Synthetic graft
    • Typically just osteoconductive, but can be laden with osteo-inductive growth factors to promote bone healing/fusion.

ADDITIONAL SUPPORT ADDED

                                                                              

After the structural bone graft is placed inside the empty disc space, a metal plate is placed longitudinally onto the front of the cervical spine to cover the affected levels. The plate is then secured with a series of metal scres to the spine.

Complete fusion starts when the structural allograft is entered from the patient's bony endplates of the vertebral bodies above and below the graft, and a process called 'bone remodeling' starts with cutting cones and creeping substitution to replace the allograft over time.

                              

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