Blog Topic: What is a “Spine Fusion”
In the average, normal spine there are 7 cervical, 12 thoracic, and 5 lumbar vertebra, a sacrum and coccyx.
From the skull to the sacrum, each vertebra is separated by a mobile disc, which is a highly complex structure which provides stability and motion at the same time.
In spinal deformity, such as scoliosis, the spine twists and bends, first through the discs and then the actual vertebra start to become misshapen, more trapezoidal instead of being more rectangular.
When we do surgery to correct spinal deformity (scoliosis) the first step is to get fixation into the vertebra so we can move those vertebra to a better, more desired position and then hold this new position firmly. In 2022 the most secure and most commonly utilized spine fixation are metal pedicle screws (usually made of titanium +/- cobalt chrome), which are placed from the back of the spine, into the bone, through the pedicle and into the vertebra.
Alternatively, hooks, wires and bands can also be used but these are not as good a fixation option when compared to screws.
The next step is to connect these screws (or hooks, wires, and bands) together with rods. These rods can then move the screws (or hooks, wires, and bands) to the desired position and then held rigidly in the new position. These rods, in my practice, are 98% of the time are cobalt chrome, the stiffest metal currently available and can obtain the optimal 3-d alignment of the spine in my hands.
These metal screws and rods are VERY strong and durable. However, we know the day we place them in surgery is when they are their strongest and have the strongest grip/fixation on the spine, and each day that goes by after surgery the metal gradually and almost imperceptibly gets weaker and the screws/hooks/wires/bands can get looser in/on the bone.
So 1 of 3 outcomes happen after we do spine surgery, at EACH VERTEBRAL LEVEL:
1. 1. The screws, hooks, wires, bands get loose from the bone.
2. 2. The rods, screws, hooks, wires and bands break.
3. 3. The spine fuses.
To achieve a spine fusion, we roughen the area to be fused with a drill, and then place bone graft. The body then breaks down/dissolves the bone graft which is then used by bone cells to create a solid bony connection over the area we want to fuse.
The aim of bone graft is to develop a spine fusion before the spine implants get loose from the bone or break.
Next blog post will discuss the different type of bone grafts.