Overview of Spinal Fusion Surgery
Spinal fusion refers to a variety of surgical techniques used to rebuild damaged, painful, or unstable joints in the spine. Conceptually, spinal fusion surgery is similar to joint reconstruction surgery in other parts of the skeleton, such as knees and hips. However, because spinal joints naturally do not move much, they can be rebuilt with “fixed” prosthetics, such as rigid cages, rather than the highly mobile prosthetics of artificial knees and hips. Rebuilding a diseased joint with a fixed prosthetic is called fusion, because the body eventually grows bone across the joint and prosthetic. This can be accomplished in the spine with minimal loss of overall flexibility.
In the cervical spine, where there is more natural movement than in other parts of the spine, mobile prosthetics can be used that preserve motion at the joint, without fusion. This is commonly referred to as an arthroplasty, or disk replacement.
When is Spinal Fusion Necessary?
In general, there are two types of spinal surgery:
1. Neural decompression surgery – The spinal cord and nerves travel in tunnels within the bones and joints that make up the spinal column. In the normal state, these tunnels are large, allowing unobstructed pathways for neural structures. However, many disease states, usually arthritis, can narrow these tunnels, causing neural compression, pain, and dysfunction. When this occurs, surgical decompression of the neural elements may be required, using techniques such as discectomy or laminectomy. These surgeries remove compressive pathology from neural elements, by removing slipped disc material, or shaving back bone spurs and overgrown joints, for example. But the joints themselves are otherwise left intact to move normally.
2. Spinal fusion surgery – When joints in the spine become severely arthritic, suffer trauma, or become compromised by tumor, they may become unstable, incapable of holding spinal bones in proper and safe alignment. When this happens, it may be necessary to surgically rebuild and stabilize the joint in a process known as fusion. Although this results in reduced flexibility, the overall loss is minimal as the joints do not move significantly, even in normal spines.
Often, neural decompression surgery and spinal fusion surgery are performed at the same time, depending on the problem being addressed.
What happens in Spinal Fusion Surgery?
The process of surgically rebuilding a spinal joint is similar to rebuilding joints elsewhere in the skeleton, but with a key difference – there is no remaining movement in the rebuilt joint after fusion. The goal of fusion surgery is to restore normal anatomical alignment of the bones around the joint, and permanently fix them in that position.
The process starts with removing the old, damaged joint, such as an intervertebral disc that has collapsed or become unstable. Once this has been accomplished, the bones on either side of the joint are restored to their normal anatomical alignment. In addition, any parts of the joint that are compressing the spinal cord or spinal nerves are removed.
Once the old joint has been removed, a prosthetic is fit into its place. This prosthetic, usually made of carbon fiber, plastic, or 3-D printed titanium, maintains the restored distance and alignment of the bones on either side of the joint. In addition, the prosthetic is packed with bone or bone-like substances (bone graft) that the body will then use to manufacture new bone within the prosthetic, creating a solid fusion across the joint space.
Often, additional steps are taken to assure that bone growth takes place to create a successful fusion. The most common of these steps is the addition of stabilization hardware. The rationale is as follows:
Bone growth conceptually is similar to the expansion of ice. On a busy highway or raging river, constant movement and activity prevents ice from ever accumulating as it is constantly broken up. However, in a calm pond or sidewalk, shards of ice in appropriate conditions can form, combine, and result in a sheet across a surface.
Similarly, delicately forming bone shards cannot meld with others to create a solid bony fusion mass within the joint if there is constant motion breaking up the shards. In years past, movement was minimized after fusion surgery by placing the patient in heavy external bracing, such as a body cast or Halo vest, and enforcing strict bedrest, often for months postoperatively. Currently, these devices are seldom used. Instead, small titanium screws, plates, or rods are placed internally in a limited fashion, only across the joint to be fused. That way, heavy external fixation becomes unnecessary. The patient can move freely after surgery while the internal fixation hardware holds the necessary joint immobile as the fusion occurs.
Examples of Common Spinal Fusion Surgery
Anterior Cervical Discectomy and Fusion (ACDF):
Anterior Lumbar Interbody Fusion (ALIF):
Transforaminal Lumbar Interbody Fusion (TLIF):
What to expect if you need spinal fusion surgery
Depending on your age and overall health, medical clearance may be necessary in preparation for the surgery. You need to refrain from eating or drinking for at least 8 hours prior to the surgical procedure. If you are taking any blood thinning medication (such as aspirin, warfarin, Xarelto, Plavix, Pradaxa), it needs to be stopped five to seven days prior to the procedure. Also note that common over the counter medications such as ibuprofen, naproxen, and aspirin can also affect your body’s ability to clot, and need to be discontinued prior to surgery. Similarly, commonly taken supplements (including garlic, Ginko biloba, flaxseed oil, saw palmetto, ginger, ginseng, fish oil, vitamin K and vitamin E) also have anti-coagulant effects. If you have any questions regarding medicine and supplements, you should discuss with the surgeon at least two weeks prior to the date of the surgery. In most cases, advanced age is not a contraindication for surgery. Safe and effective surgery can be performed on patients in their 70s, 80s, or even later.
The duration of the surgery can vary but usually takes between one to four hours depending on the severity of the pathology as well as the number of spinal segments that need to be treated.
A routine spinal fusion can often be performed using minimally invasive surgical techniques in the outpatient setting. Total surgical time is around two hours In most cases, patients are able walk independently within hours of the procedure. Surgical discomfort can be managed with oral pain medication for a few days. Most patients will transition to over the counter pain medication within two weeks of the surgery.
Recovery from a spinal fusion will vary depending on your age, general health, and the extent of the surgery done. In general, you will avoid bending, lifting, and twisting (BLT) for two weeks after surgery. During this time, you will be encouraged to remain active by walking.
Sometime between 2 and 6 weeks post operatively, you will begin structured rehabilitation and exercise with physical therapy. By 12 weeks, most patients can be back to a normal, non-strenuous activity. For patients who must engage in heavy lifting and bending (e.g. construction workers), return to work may be delayed until 6 months after surgery.
Risks of the Surgery
Spinal fusions have a long track record of safety and efficacy, especially after the development of minimally invasive and microsurgical techniques. However, all surgeries entail some degree of risk. For spinal fusion, these include:
- Nerve damage
- Spinal fluid leak
- Anesthesia-related complications (e.g. pneumonia)
Fortunately, these complications are rare. When they do occur, they can typically be managed successfully, and not adversely affect your long-term result.
When selected carefully, and only when all conservative measures have been exhausted, patients who undergo spinal fusion have significantly better outcomes than non-surgically treated patients. Improvement is usually felt by 3 months after the procedure and surgically treated patients have more active lives. When surgery is followed by postoperative lifestyle changes, including weight loss, exercise, and proper posture, the benefits of spinal fusion can be permanent.