Spinal fusion is a technique used to stabilize the spinal bones or vertebrae. The goal of lumbar fusion is to create a solid bridge of bone between two or more vertebrae. Spinal fusion may be recommended when the natural disc space has decreased or the spine is unstable.
- Interbody Fusion
- Anterior Lumbar Interbody Fusion (ALIF)
- Bone Grafting
- Post-Operative Hospital Care
- X-ray Examples
The spine is composed of individual bones called vertebrae. There are typically five lumbar vertebrae. They are stacked one on top of another and are separated by discs, which act as elastic cushions or shock absorbers. Discs have a soft center, the nucleus, surrounded by a tough outer ring, the annulus. Discs allow motion between the vertebrae. The interbody space is the disc space that is located between the vertebral body bones. Each vertebral segment creates a bony circle, called the spinal canal that protects the spinal cord and spinal nerves. The spinal cord, which is the nerve center of the body, connects the brain to the rest of the body. The spinal cord and nerves travel from the cervical spine down to the lowest point of your spine, the sacrum. Spinal nerves exit the spinal canal between the vertebrae at each level. Two nerves exit each level, one on the left and one on the right. These nerves exit through openings called foramen. The discs, bony structures, ligaments and strong muscles all work together to stabilize the spine.
Interbody fusion involves placement of fusion implants and bone graft into the area between two vertebral bodies and is an effective method for achieving fusion. The intervertebral implant may be made from a variety of materials including metal, plastic, or bone. Bone graft and bone healing protein may be placed within the implant and within the interbody space to encourage bony healing. The implant helps by separating and holding the two vertebrae apart. This increases the opening around the nerve roots at that level, relieving pressure on the nerves. The intervertebral implants can also be used to correct spinal deformity and restore proper alignment. Intervertebral implants can be placed from the front, side or back of the spine. The location of the surgery is dependent on the specific anatomy of each patient, as well as the location and amount of pressure that may be occurring around the nerves in the spinal canal. The decision is based on many factors including the patient’s anatomy, location of the levels that need to be fixed, degree of spinal instability, and prior abdominal surgery.
When the implant is placed from the:
- Front to the lumbar spine, it is called an Anterior Lumbar Interbody Fusion (ALIF).
- Side to the lumbar spine, it is called a Lateral Interbody Fusion (XLIF/DLIF).
- Back to the lumbar spine, it is called a Posterior Lumbar Interbody Fusion (PLIF) or a Transforaminal Lumbar Interbody Fusion (TLIF).
In some cases, the surgeon will use additional surgical instrumentation in the front for stability. This is usually a plate and screws in the front of the spine. If support is also needed from the back of the spine, a series of screws and rods may be used. This is called a posterior instrumentation fusion and helps to achieve a posterior fusion in addition to an interbody fusion.
This surgery is done under general anesthesia, meaning the patient goes to sleep. During the surgery the patient lies face up on a special surgical bed. The procedure is performed through a three to five inch incision on the stomach and is either approached over the center of the stomach or slightly to the side. The large blood vessels that lie in front of the spine are carefully moved aside.
Once the surgeon safely creates a window to see the spine, the damaged disc is removed with surgical tools. Some of the disc wall is intentionally left behind to help contain bone graft material. Once the disc space has been cleared out, the surgeon prepares the bony surfaces for a fusion. The bones are slightly spread apart to make more room for the bone graft. This distracts the bones to realign proper curvature and enlarges the openings to relieve pressure off any pinched nerves.
An implant filled with bone graft is placed in the now empty disc space between the two vertebral bodies. Bone graft inside the disc space will go on to fuse, healing the two bones together in this area. If the fusion is successful, the vertebrae will move as one unit. This reduces future problems at this spinal segment. If the bones do not fuse as planned this is called a nonunion, or pseudarthrosis.
For some patients, an ALIF surgery is staged and followed with a Posterior Instrumentated Fusion. The posterior instrumentation may be required for stabilization to ensure fusion. If you do not have optimal bone strength, measured by a DEXA scan, a plate on the front of the lumbar spine may not be enough to support your fusion while your body builds stronger bone in between the vertebrae. This would require additional stability. These are two examples of a staged procedure. This staged procedure means you will have two smaller surgeries one day apart.
Any spine surgery has surgical risks involved. You need to discuss these with your surgeon at your pre-operative appointment. Read about Preparing for Spine Surgery and General Complications from Spine Surgery.
There are multiple options for bone graft material for spinal fusion. Surgeons at the Virginia Spine Institute may use a combination of your own bone from the area of the spine being operated on, from your hip bone, as well as bone morphogenetic protein (BMP), a genetically engineered substance that stimulates bone healing. For some patients, additional donated and prepared allograft bone is also used. Read more about how bone grafting is used as a surgical innovation.
Patients usually remain in the hospital one to three days after surgery and three to five days after a staged surgery. Postoperative pain control will be achieved with the use of IV pain medication, epidural pain medication, and/or oral pain medications. Patients are discharged home on oral pain medication. Patients begin a physical therapy walking program the day after surgery, and a physical therapist works with the patient to learn how to get out of bed and walk safely. Patients need to be comfortable with walking, climbing stairs, and getting in and out of bed before going home. The final goal is to make sure the gastrointestinal and urinary systems are working appropriately. Patients must be able to eat a solid meal and urinate without difficulty prior to leaving the hospital.
Read about Recovery from Spine Surgery and make sure you understand your post-operative plan before your surgery date.
Anterior lumbar interbody fusion is an approved and effective method for fusing the lumbar spine. The goal of surgery is to decrease pain, correct spinal deformity, and improve stability. Complications may occur but are not common. The majority of patients are satisfied with their pain relief and the results of their surgery. It is important that all patients are physically and psychologically prepared. All patients should stop smoking prior to any surgery, as smoking is extremely detrimental to your spine health, potential bone healing and successful surgical outcomes. Please review additional details with your surgeon prior to your surgery.