Spinal Fixation/Fusion

Spinal fixation/fusion is a procedure in which a surgeon uses instruments such as rods, plates, and screws to help bones of the spine fuse.

An instrumented spinal fusion is performed in conditions like, deformity, trauma, tumour, or surgery. The purpose of this surgery is to restore spinal strength so that the spine can withstand normal day-to-day stresses and can also protect the spinal cord and nerves.

The basic principle of a spinal fusion is the creation of a bone bridge (Autograft- own bone, allograft – artificial bone). Upon this the proteins in the human body encourage bones to grow and fuse with each other. In an instrumented spinal fusion, instruments–rods, plates, screws, cages, and/or hooks–hold the bones in place while they fuse. The screws or hooks serve as strong anchors to the spine. These anchors are then attached to metal rods that span the weakened segments, forming a metallic bridge. When good fusion is achieved, the instruments are no longer necessary. However, they are usually left in place to avoid additional surgery

Conditions requiring Instrumented fixation

• Mechanical back pain – Not relieved by non surgical methods.
• Diseased conditions – Spondylolisthesis, spinal deformities
• Spinal instability – caused by tumours, trauma/fractures, malformations, degenerative, and surgical instability

Benefits of instrumented spinal fusion include:

• Immediate spinal stability
• Early and better bone fusion
• Correction of spinal deformity
• Prevention of further deformity

Risks of instrumented spinal fusion include:

• Increased chance of infection
• Increased rigidity and further mechanical problems
• Increased soft tissue disruption and therefore perhaps postoperative pain

Surgery – This surgery is performed under general anaesthesia, where the patient is unconscious and cannot feel pain during the surgery. In most of the cases, before spinal fusion the spinal cord or nerve roots are decompressed by removing the covering bone to alleviate pain and remove damaged tissue.

Spinal fusion may be performed at any level of the spine: cervical, thoracic, lumbar or sacral.

• Occipitocervical fixation: The Occiput, base of the head and the high cervical bones are fused with the help of lateral mass screws and occipital plate.
• Cervical lateral mass screw fixation: specialised small screws are inserted along the sides of the cervical vertebrae from behind and are fixed with long rods and screws on top of them.
• Pedicle screw fixation: Pedicle screws, which are specialized bone screws that are inserted into the pedicles, thick, sturdy sections of bone at the back of the spine. These act as attachment points for the rods, inserted next, that form the metal bridge. These are usually done at thorasic and lumbar level pathologies.
• Anterior cervical fixation: These fixations are done from the front of the neck, after discectomy (removal of disc) or a corpectomy (removal of a vertebral body). The front of the spine bears much of the weight of the body, so implants in this area must be extremely strong. Sometimes, a solid piece of bone (ileac crest) is used as an implant in an anterior fusion. Plates and screws may help support any type of anterior implant and keep it in place as the bones heal.