The vertebrae are the bones that make up the spinal column, which surrounds and protects the spinal cord. The intervertebral discs are soft tissues that sit between each vertebra and act as cushions between vertebrae, and absorb energy while the spinal column flexes, extends, and twists. Nerves from the spinal cord exit the spinal column between each vertebra.
Spinal fusion is a surgical technique in which one or more vertebrae are fused together to stop the motion between them. Spinal fusion may be recommended for:
Abnormal curvature of the spine (scoliosis or kyphosis)
Injury to the spinal vertebrae (spine trauma)
Protrusion of the cushioning disc between vertebrae (slipped disc, herniated disc)
Weak or unstable spine caused by infections or tumors
Different incisions are made depending on the area to be treated. The approach can be made either from the front (anterior), from the back (posterior), or both. Bone grafts may be used in the area of the spine to be fused. Fusion of new bone takes about three months and continues to gain strength over the next one to two years. Until then, the back muscles hold the graft in place. Alternatively, small titanium or carbon cylinders (known as cages) can be used to fuse two vertebrae together. The diseased disc is removed and a cage takes its place. The cage is then filled with bone graft, stimulating new bone growth that then fuses the vertebrae. Lastly, screws are sometimes used in a fusion surgery to add extra support and strength to that particular part of the vertebral column as the fusion heals. A rod is used to connect the screws which prevents movement and allows the bone graft to heal. After the fusion is completely healed, the screws and rods are typically left in place unless they cause the patient discomfort.