Spinal Fusion, also called Arthrodesis, is a surgical procedure to join two or more vertebrae together in order to provide stability and strength to the spinal canal and eliminate pain. To learn more about Spinal Fusion, let us first learn about normal spine anatomy.
Normal Spine Anatomy
The spine, also called the back bone, is designed to give us stability, smooth movement, as well as providing a corridor of protection for the delicate spinal cord. It is made up of bony segments called vertebrae and fibrous tissue called intervertebral discs. The vertebrae and discs form a column from your head to your pelvis providing symmetry and support to the body. The spine can be divided into 4 parts. The uppermost is the cervical region, consisting of 7 small vertebrae that form the neck.
As we move down the body, the next 12 vertebrae make up the thoracic region or mid back from which the ribs are hinged. The 5 lumbar vertebrae are the largest of the mobile vertebrae and supports 2/3 of the body’s weight. The lowest region of the spine is the sacrum and coccyx. The sacrum is a triangular plate made up of 5 fused vertebral segments while the 4 coccyxes terminate the bony spine.
A single vertebra is made up of two parts; the front portion is called the body, cylindrical in shape, and is strong and stable. The back portion of the vertebra is referred to as the vertebral or neural arch and is made up of many parts. The strong 2 pedicles join the vertebral arch to the front body.
The laminae form the arch itself while the transverse process spread out from the side of the pedicles like wings to help anchor the vertebral arch to surrounding muscle. The spinous process forms a steeple at the apex of the laminae, and is the part of our spine that is felt directly under the skin.
The laminae of the vertebra can be described as a pair of flat arched bones that form a component of the vertebral arch.
This canal is formed by the placement of single vertebral foramina, one on top of the other, to form a canal. The purpose of the canal is to create a bony casing from the head to the lower back through which the spinal cord passes.
Pars Inter Articularis
Known as the Pars, it is the part of the vertebral arch where the pedicle, transverse process, and articular process transect.
The intervertebral disc sits between the weight bearing vertebral bodies, servicing the spine as shock absorbers. The disc has fibrous outer rings called the annulus fibrosus with a watery jelly filled nucleus called the Nucleus Pulposis.
The spinal cord is the means by which the nervous system communicates the electrical signals between the brain and the body. It begins at the brain stem and is held within the spinal canal until it reaches the beginning of the lumbar vertebrae. At L1 the spinal cord resolves down to a grouping of nerves that supply the lower body.
Facets joints are the paired articular processes of the vertebral arch. These synovial joints give the spine it’s flexibility by sliding on the articular processes of the vertebrae below.
Indications for Spinal Surgery include:
- Spondylolisthesis: occurs when one vertebra slips forward in relation to an adjacent vertebra causing misalignment and potential entrapment of the spinal nerves. This condition can be congenital (present at birth) or can develop in childhood or adulthood.
- Degenerative Spondylolisthesis: degeneration of the vertebral components, usually occurring after age 50, and can lead to spinal stenosis, a narrowing of the spinal canal.
- Scoliosis or Kyphosis: abnormal curvature of the spine
- Degenerative Disc Disease: (wear and tear of the discs between vertebrae) that is unrelieved by extensive non-surgical treatments such as Physical Therapy, medications, steroid injections, rest, ice or heat.
- Traumatic injury such as fracture
- Recurrent Disc Herniation: protrusion of the disc contents between vertebrae
- Infections or Tumors causing weakening of the spine
- Instability: abnormal and excessive motion between two vertebrae.
Evaluating the source of back pain is critical in determining where a fusion is performed. Dr Hsu or Dr Singh will perform the following:
- Medical History
- Physical Examination
Diagnostic Studies may include:
- X-rays: a form of electromagnetic radiation that is used to take pictures of bones.
- MRI: magnetic and radio waves are used to create a computer image of soft tissue such as nerves and ligaments.
Spinal Fusion surgery joins (fuses) two or more vertebrae together with bone grafts and internal fixation devices to eventually form one solid piece of bone. The ultimate goal of the surgery is to alleviate the patient’s pain by generating bone growth which fuses the vertebrae and limits movement in that area of the spine.
- Spinal Fusion surgery can be performed by an open incision.
- Dr Hsu or Dr Singh will decide whether to approach the spine through the back, abdomen, or neck, depending on the area to be fused. This will be the location of your incision.
- Bone graft can be either from your hip or a bone bank or a combination of both. There are also bone graft substitutes now available.
- Pedicle screws, plates, or cages may or may not be used with the bone graft.
Dr Hsu or DrSingh will decide which options are best for you depending on your specific circumstances.
The surgery is performed under sterile conditions in the operating room with the patient under general anesthesia. Dr Hsu or Dr Singh:
- May perform a discectomy which is the removal of the damaged disc material between the vertebrae
- A Laminectomy may be done which is the removal or trimming of the lamina (roof) of the vertebrae to relieve pressure on spinal nerves.
- Screws are then placed on each side of the vertebrae to be fused
- Rods are attached to connect the screws and stabilise the spine
- Bone graft (tiny bone chips) is then placed alongside and/or between the vertebrae
It is imperative that proper spine alignment is maintained after your surgery.
After the surgery you are brought to the Intensive Care Unit, where the medical staff monitors your vital signs and also manages your post-operative pain. Patients may experience pain at the site of incision, spasms of the neck muscles, or other symptoms. After the surgery, a cervical collar is placed on your neck.
You will be taught how to use proper body mechanics to turn in bed, reposition, stand up, sit, and walk in order to maintain the integrity of the surgical fusion while it is healing.
- You will normally stay in the hospital 5-7 days.
- You will be given pain medication to make you comfortable and you may have a PCA machine: a patient controlled device to administer pain medication.
- You will probably have a urinary catheter.
- A postoperative Rehabilitation program may be prescribed by Dr Hsu or Dr Singh
- Activities will be limited for at least 6 weeks
The fusion process varies in each patient and can take anywhere from 6-9 months or longer.
Risks and complications
- As with any major surgery there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages.
- It is important that you are informed of these risks before the surgery takes place.
Complications can be medical (general) or specific to spinal surgery. Medical complications include those of the anesthetic and your general well being. Almost any medical condition can occur so this list is not complete.
- Allergic reactions to medications
- Blood loss requiring transfusion with its low risk of disease transmission
- Heart attacks, strokes, kidney failure, pneumonia, bladder infections
- Complications from nerve blocks such as infection or nerve damage
- Serious medical problems can lead to ongoing health concerns, prolonged hospitalization, or rarely death.
Specific complications of Spinal Fusion include:
- Urinary difficulties such as retention
- Paralytic Ileus: Intestinal function may be temporarily absent or decreased
- Spinal Cord Injury can cause paralysis in certain areas depending on where the injury occurs.
- Hardware Fracture: the metal devices used for stabilization of the vertebrae can break or move requiring additional surgery.
- Implant migration: if the implant moves from where the surgeon initially placed it, a second operation may be required.
- Continued or increased pain
- Sexual dysfunction if nerves to pelvic area are damaged
- Transitional Syndrome: pain caused by increased wear and tear to the vertebrae adjacent to the surgical site due to increased stress in these areas.
- Pseudoarthrosis: Failure of the vertebrae to fuse together causing motion between the vertebrae and increased pain.