Minimally Invasive Spinal Fusion Overview
Pain in the lower back (lumbar spine) is the second most common reason for visits to the family physician. Typically lumbar pain can improve without surgery, through conservative therapy, i.e. medication, physical therapy, or injections. A spinal fusion is considered a last resort and is only needed when conservative therapy proves ineffective.
Reasons for a Fusion
One of the main reasons for a spinal fusion surgery is instability in the lower back. Instability can arise due to age, a stress fracture, or if the small joints that keep the spine straight move out of alignment. The surgeon usually grades the instability from 0-4, with 4 being severe.
As we age, the wear and tear on the back can cause the disc and joints to wear down and slip out of place. When this happens, the bone is unable to maintain its position and can start pressing on nerves. A fusion may also be needed because of degenerative disc disease. As we get older, the spinal discs begin to break down and the fluid in our disc begins to decrease. As a result, the disc begins to lose its ability to act as shock absorbers and is less flexible. Due to fluid loss and dehydration, the discs become thinner and narrows the distance between the vertebrae. Cracks and tears can form, causing the jellylike material inside the disc to be forced out, resulting in the disc to bulge or even rupture.
The degeneration of the discs and instability in the back can result in pain in the back, buttock or leg, as well as weakness, numbness or tingling in the leg. The surgeon can attempt to remove the piece of ruptured disc or clean up the bone spurring that is pinching the nerve. For some people, their disc can re-rupture, even after a microdiscectomy and in some cases, can only be corrected through a fusion.
Instability can arise due to a condition called spondylolisthesis. This occurs when the small joints that help keep the spine aligned move out of line. Once the bone in your back slides forward over the bone below it, nerve roots can become squeezed. The small joints can move out of line due to trauma to the back, a stress fracture, a congenital defect, arthritis, or an infection.
Symptoms of spondylolisthesis include back pain, numbness or weakness in both legs. In rare cases, it can lead to loss of bladder or bowel control. Some people experience no symptoms or symptoms years after the bone slides forward.
A lumbar spinal fusion surgery can also be necessary to remedy a rare condition called spondylolysis, which is affects mostly affects the fifth lumbar vertebra in the lower back. Spondylolysis is a stress fracture in one of the vertebras of the back. The vertebrae can also start shifting out of place if there is a severe stress fracture.
All of these conditions can be diagnosed by x-rays of the lower back but an MRI or CT scan may be needed before treatment begins to see if the vertebra is pressing on nerves. Initial treatment includes conservative therapy (anti-inflammatory medications) and taking a break from physical activities. The surgeon may also recommend physical therapy or a back brace. Injections and pain management may help temporarily and exercises could aid in stabilizing the core/trunk strength. If the slippage continues to get worse or if the back does not respond to conservative therapy, a spinal fusion may be necessary.
During a spinal fusion procedure, two vertebrae are fused (joined) together to lock it into place (see spinal fusion surgery video above). The spine is made up of vertebrae and between each vertebrae is an intervertebral disc which serves as support and helps keep the spine aligned properly. If an intervertebral disc is damaged or herniated, it must be removed. Once removed, the vertebrae don’t have support and therefore the two vertebrae must be fused to keep the spine aligned. A bone graft helps grow new bone between the two discs, joining the two together. For a spinal fusion, it is typically taken from pelvic bone or a cadaver.
If a spinal fusion is necessary, more and more people are opting for minimally invasive surgery versus traditional surgery. Minimally invasive spinal fusion causes less damage to surrounding tissues, which exposes less muscle for a quicker recovery and fewer spinal fusion surgery risks. Using a microscope, the muscles are spread gently and the surgeon can work around them, reducing spinal fusion complications. In addition to less muscle damage, minimally invasive spinal fusion results in a smaller incision, reduced blood loss, less pain, and a shorter stay. The length of spinal fusion recovery time is also greatly reduced, as is the amount of narcotic pain medication needed.
There are three main types of minimally invasive spinal fusion, based on where damaged intervertebral disc is located. ALIF, where the incision is through the abdomen, XLIF Spinal Fusion, through the side, and TLIF, through the back.
Spinal fusion surgery recovery time depends on the severity of the instability but usually consists of just one week of rest and downtime. During the week, you’re up and walking, resting, and taking it easy. The next step is a few weeks of lighter activity, walking, and working and then by six weeks post op, some light exercise.