The cervical decompression and spine fusion surgery is performed with the patient in the supine position (lying on the back, with the face upward) under general anesthesia. Usual requirements include adequate padding of bony and soft tissue structures. Sequential compression boots are applied to the patient's lower extremities to avoid development of blood clots during the operation.
Most spine surgeons prefer to use Somatosensory Evoked Potentials (SSEPs) or Motor Evoked Potentials (MEPs) to monitor spinal cord function during the surgery. However, this is not essential.
Anterior Cervical Decompression and Fusion Operation
The spine surgeon will often use either an operating microscope or surgical loupes to provide for magnification and illumination as the operation proceeds. Although the dural sac is visualized during the decompression, the spinal cord and nerve roots are not directly seen.
The surgical procedure is done as follows:
- The decompression and spine fusion procedure begins with either a longitudinal or transverse incision in the lower front of the neck. The underlying musculature of the neck is carefully dissected, allowing the surgeon to expose the front of the cervical spine by retracting the esophagus and trachea toward midline and the carotid artery and associated structures to the side.
- Muscles and membranes overlying the anterior cervical spine are dissected as well, and retractors are placed to protect the soft tissues of the neck as the operation proceeds.
- After the surgical level(s) have been confirmed by X-ray or fluoroscopy, intervertebral discs are removed at the level(s) to be decompressed. In some instances it is only necessary to remove the abnormal discs, with or without small bone spurs at their margins.
- osteophytes (bone spurs) are present, the surgeon may opt to remove the vertebrae between the evacuated disc spaces. Biting instruments (rongeurs) of varying sizes and shapes and high speed drills are used to remove the remaining bone and disc material, creating a trough measuring 15-16 mm in width extending across the entire longitudinal extent of the involved portion of the cervical spinal cord. If the vertebrae are removed as well, this component of the surgery is called a corpectomy.
- Bone and disc are removed down to the level of the posterior longitudinal ligament (PLL), which overlies the dura directly. The spine surgeon may choose to remove the PLL if it is felt that it contributes to the compression of the spinal cord, or if there are fragments of herniated disc material beneath it. In that case the posterior longitudinal ligament is then carefully grasped and incised, and then removed in a piecemeal fashion.
- After the spinal cord and nerve roots have been decompressed at the appropriate levels, the portions removed must be reconstructed so as to support the normal loads of the cervical spine. This means either inserting bone grafts within each disc space ('interbody' grafts), or inserting a longer 'strut' graft which spans the defect created in the process of removing a vertebral body(s). In either case the intent is to promote the formation of a living bridge of bone between the previously distinct vertebrae (a spine fusion). The spine surgeon may employ either the patient's own bone (autograft) or banked human cadaver bone (allograft), or a synthetic scaffold into which bone graft may be inserted (metal or carbon fiber cages). The reasons for selecting among these are many and complex. Patient and surgeon should discuss these issues pre-operatively, keeping in mind that the chosen strategy will influence the likelihood of healing success. Failure of bone graft healing is among the principal reasons for repeat surgery in these cases.
- In many cases, the spine surgeon will recommend internal fixation of the operated/grafted segments with a titanium plate and screw device, which is secured to the remaining vertebral bodies at the margins of the corpectomy, providing for further stability and promoting adequate fusion as well as preventing dislodgement of the bone graft.
Factors thought to increase the probability of bone graft/fusion failure include:
- Increasing numbers of levels to be fused (i.e., 2 levels is more difficult to fuse than one level)
- Smoking or other sources of nicotine intake
- Patient failure to comply with postoperative activity restrictions and/or brace wear
- Poor bone quality (e.g. from osteoporosis)
- Certain medications (e.g. predisone, anti-inflammatories, chemotherapy, rheumatoid arthritis, etc.)
The usual length of stay in the hospital for decompression and spine fusion surgery varies from one to four days.