Lumbar fusion is a surgical procedure that aims to treat back pain. The premise is that the pain occurs because the back is not strong enough to support a patient’s weight or their activity level. Patients almost always have a dramatically abnormal MRI such as a collapsed disc or most commonly, spondylolistheis, which is a slippage of the bones of the back. Because a lumbar fusion places extra stress on the levels above and below the surgery, it is less recommended for younger patients. A lumbar fusion is typically a last resort option for the patient. It is considered only after all other measures such as physical therapy and injections have been exhausted.
In this surgery, screws, rods and a “cage” are implanted to strengthen the spine. In exchange for the increased strength, there is typically a 5-10 degree reduction in the flexibility of the patient’s back. Because most bending occurs at the hip, patients with a fusion can still accomplish this activity, but may feel a stiffness in their back. By improving the strength of the back, the lumbar fusion surgery has a 50-70% chance of reducing back pain.
After anesthesia, a cut in made in the back and the bone overlying the nerves is typically removed to take pressure off the nerves. This removed bone also serves as the material that is placed between the vertebrae or bones of the back. This bone, often along with bone from a cadaver, then grows into your existing bone to provide long term strength.
When there is insufficient replacement bone from the back, bone is harvested from the spinous processes (a bony projection off the back of each vertebra) or from the lamina bone in the hip. The material removed from the hip is a soft marrow substance and not a large wedge of solid bone. The purpose of this material is to help grow new bone at the fusion site in order to contribute to the long term strength of the spine.
The disc is removed and replaced by a cage that expands to restore the height of the disc. Bone is also packed between the vertebrae and along the sides of the spine to form the fusion. Screws, called “pedicle screws” are placed in the bone to hold the spine “still” and facilitate bone growth. They are bridged by a metal rod approximately one and one-half inches long, with the diameter of a pencil.
The surgery typically takes 2-3 hours and is followed by a 1-3 day stay in the hospital. While patients can walk right away, recovery typically takes 8-12 weeks. After that time patients can usually resume normal but non-strenuous activity.
In addition to the typical risks of bleeding, infection, nerve injury and CSF (cerebrospinal fluid) leak, there is also the risk that the bone will not grow. In that case, a 2nd second surgery could become necessary.
The screws and rods used in the surgery are made of titanium and do not set off metal detectors. The screws and rods could be removed in 1-2 years but, generally an additional surgery to do so is uncommonly done. (See drawing at the top of page)