Spinal Fusion: An Overview

Spine Care Institute
Hospital for Special Surgery


Introduction

Spine fusion is the result of any process that makes bones of the spine grow together, eliminating the motion between those bones. There are obvious questions that surround spinal fusion:

  • What is spine fusion?
  • How and why do doctors do them?
  • What can be expected regarding quality of life after spine fusion?

When we are born, all of our joints are new and have experienced none of the “wear and tear” that is a part of our daily routine. While some people will be involved in heavy labor for their jobs, or will enjoy running several hundred miles per year, even the typical activities of average people lead to small amounts of wear and tear in their joints every day.

Over the course of a lifetime, the daily wear and tear can lead to pain in the joints also known as arthritis. Arthritis can affect all of the joints of the body, including the spine, usually resulting in pain with movement. When non-operative treatments fail to control end-stage spine arthritis symptoms, one way to control symptoms of painful motion is to stop the motion by fusing the affected section of the spine.

How and Why a Spine is Fused

Spinal fusions can happen by themselves, or they can be the result of surgery.

Infections in the spine (most notably with tuberculosis or after infections in the disks of the spine) can lead to spontaneous spine fusions, as can very severe scoliosis or kyphosis (spine deformities leading to altered shapes of the spine). Much more commonly, spine fusions are the result of surgeries intended to induce the “knitting together” of the spine bones (called “vertebrae”).

In 2005, over 300,000 spinal fusions were performed in the United States involving the chest (thoracic) or low back (lumbar) vertebrae, and another 100,000+ were done to fuse vertebrae in the neck (cervical spine).

Reasons to perform the surgeries include: 

  • End-stage spine degeneration
  • Fractures of the spine
  • Loss of spine stability
  • Severe spine deformity
  • Tumors of the spine.

Surgeries for fusions use many different techniques, but all of these involve “tricking” the body into “believing” that the vertebrae to be fused are parts of a broken bone. Once the surgery is complete, the body does its job to “heal the broken bone,” resulting in spine fusion.

Improving Bone Healing

Spine fusions require bone healing, the same way that bone healing is required to mend a fractured leg or arm bone. There are several ways to improve bone healing, including keeping the bones from moving, using bone grafts to promote bone growth, and using new drugs (bone growth factors) or devices (electrical bone growth stimulators) to stimulate and increase bone production.

Implanting Devices: Bone movement during attempts at healing prevents the “knitting together” of bone pieces, and results in what is called “non-union” or “pseudarthrosis.” Bone movement can be minimized by implanting devices (screws, rods, and others) that support the bones and hold them motionless, or by using postoperative braces that support the neck or trunk and reduce movements.

Bone grafts: These can come from the patient undergoing the operation (called autografts) or from donors (called allografts). Autografts for spine fusions are very commonly taken from the pelvis (the iliac bones), and may require a second incision during the surgery. Allografts are commercially supplied, and are processed to minimize complication risk (infection or other). Bone grafts act as the “raw materials” for the bone healing process, and greatly improve the success rates for bone healing.

Bone growth factors: Bone morphogenetic protein (BMP) or parathyroid hormone derivatives (PTH), two examples of bone growth factors, can also greatly improve the production of bone and improve fusion success rates. The BMPs are used during surgery, and PTH is used in the months after surgery. Electrical stimulators can be implanted during the surgery or applied to the skin postoperatively, and promote bone healing by acting on the bone cells and making them more productive in the healing process. Using combinations of these treatments improves fusion success even more.

Recovery from Surgery

After spine fusion surgery, patients typically feel stiffness in the area where the fusion was performed. Most fusions involve only two vertebrae, so the amount of stiffness to expect is relatively small. Longer fusions will result in more stiffness; remember that a fusion is designed to stop motion, so the stiffness is an expected result.

Patients frequently have a urinary catheter in the early days after spine fusion surgery, and will have a “pain button” to deliver medicines as needed to control discomfort at the surgical site. Pain at the site of the surgery for 3-6 weeks after the operation is unfortunately quite common, but these symptoms resolve with time - as does the need for pain medicine.

In the months before and after spine fusion surgery it is important to maintain good nutrition to keep the body primed for bone healing, and to avoid smoking or use of non-steroidal medicines (such as naprosyn or ibuprofen) as these interfere with bone healing.

Physical therapy is another important factor in the ultimate success of the spinal fusion, and completing the exercise regimens preoperatively and postoperatively will help to ensure that the spine fusion surgery performed will result in improvement in the symptoms experienced. Physical therapists will teach patients how to move to avoid pain symptoms and how to prevent putting excess stress and forces on the spine during the healing process.

As a part of the preoperative evaluation, your surgeon will have you seen by an Internal Medicine physician to be certain that you are as healthy as you can be, and to check that there are no parts of your health that need to be improved prior to surgery (such as quitting smoking, starting a medicine to control high blood pressure, or the like).

Remember the saying that “an ounce of prevention is worth a pound of cure,” and that if there are things we can identify to reduce the risks of surgery, it is best to address them before the surgery is done.

Summary

At HSS, we specialize in a variety of surgical procedures that help to optimize spine fusion success. We offer anterior and posterior approaches to the spine for ideal “fit” of the procedure to the needs of the patient, and a variety of options to help improve the fusion success, including minimally invasive methods, multiple types of bone grafts, bone growth factors, among other interventions.

Through combination of specialized surgical techniques, use of appropriate bone grafts, and post-operative physical therapy to maximize functioning after surgery, spinal fusion procedures are very well tolerated and provide excellent control of symptoms.


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