L

umbar fusion (also known as arthrodesis) is the most widely used technique in spine surgery and consists of creating a bone weld between 2 vertebrae so that they stop moving. To achieve a good weld requires that there is no movement, the absence of movement allows bone growth which is achieved through the use of the famous screws, rods and interbody devices (they are boxes that are placed between the vertebrae to increase stability and promote fusion).

The surgery consists of stimulating the bone growth so that it grows and two vertebrae so that they stop moving. Often bone substitutes are used to promote the creation of bone solder.

When is lumbar fusion performed?
A lumbar fusion should be performed when we have vertebral instability, vertebral degeneration is very important and/or low back pain is one of the predominant symptoms.

We refer to vertebral instability when there is excessive movement between the vertebrae, sometimes the instability is prior to surgery as occurs in spondylolisthesis.

Sometimes when a nerve decompression is performed we have to remove too many bone structures to access the lumbar canal and decompress the nerve roots, so we generate post-laminectomy instability and it is necessary to fuse the vertebrae.

There are other occasions when there is very advanced disc degeneration or very important osteoarthritis in the joints that join the vertebrae. In these cases, arthrodesis is performed if low back pain is significant.

Types of vertebral mergers
The different types of vertebral fusion can be divided into 2 depending on where we access the vertebra and where the bone bridge or weld is performed. By generalizing we will divide vertebral fusions into posterior and anterolateral.

Complications of lumbar fusion
Performing a spinal arthrodesis increases the risk of complication since it increases the surgical time, which can increase the risk of bleeding and therefore the risk of receiving a transfusion. Increased surgical time is also associated with a higher incidence of infections.

Pseudoarthrosis or lack of union. Sometimes the bone does not grow and vertebral fusion is not achieved. However, we usually have fusion rates higher than 90%. The lack of union causes back pain and excess tension on the screws, which can cause them to break or loosen. To solve a pseudoarthrosis we must re-intervene the patient. To increase stability, we usually put screws with a larger diameter, put in interbody cages if there were none, or increase the size of the interbody cages if possible.

Degeneration of the adjacent disc. There is a theory that increasing the stiffness of the column increases the stress and load on the upper and lower segments of the fusion. The degeneration of the adjacent disc with clinical repercussions varies between 5.2% and 18.5%. When we have a degeneration of the adjacent disc, many times it is necessary to extend the surgery and fuse the vertebrae of the disc that has degenerated.