Spondylolisthesis

The term spondylolisthesis refers to a slip of one vertebrae on another, either backward( retrolisthesis) or forward (anterolisthesis). Minor degrees of slip are common in the aging spine but occasionally these slips may be significant enough to cause symptoms typically of back or nerve root/ radicular pain.- sciatica

Due to the shape of the spine being like a long S when viewed from the side, in the standing position different forces act on the different regions of the spine so as to make a slip more likely to occur. The position in the spine will also determine whether the slip occurs forward or backward. For instance a significant amount of force acts on the spine in the lowest lumbar segments and this contributes to the fact that a slip may commonly occur at L5/S1 or L4/5. These slips are part of a number of indicators of spinal instability and causes of a spodylolisthesis include:

• Degenerative discs and facet joints- most common

• Developmental - Due to a pars defect or fracture

• Trauma and associated fractures - usually high velocity injuries

The two most common are degenerative which tend to seldom be more than 50% and those due to a pars defect which can be greater degrees of slip.

Pars defects (spondylolysis) and fractures/Lytic spondylolisthesis

Pars defects occur when parts of the spine fail to develop correctly. The pars interarticularis is the bony element that connects the facet joints to the main structural elements of the spine and so if this bony element is missing or only formed by scar tissue, the vertebrae may slip forward over time. There are a number of other elements that support the vertebrae so the slip usually takes many years to develop. The mechanism behind this is not always clear but symptoms seldom occur until at least the teenage years.

Certain sporting activities can lead to excessive force being placed across certain elements of the spine leading to stress fractures or even complete fractures. These don’t typically require surgery but may require changes to those activities that have led to stress. If a fracture has been present for some time and has not led to a slip but is symptomatic, we can considered repairing the fracture/defect before a slip occurs. Once the vertebrae have started to slip, there is commonly associated change to the disc and typically we would reduce the slip and fuse the disc rather than consider a form of repair.

Degenerative Spondylolishesis

This is the most common group and often leads to symptoms in patients later in life. Symptoms of back pain and sciatica may require surgical treatment, as the condition is often associated with spinal stenosis. Although injections with steroid may keep symptoms at bay, ultimately patients often require surgery and in the presence of spondylolisthesis, may require a fusion procedure. This is very dependent on the patient’s particular symptoms and findings on clinical examination and scanning which also may dictate what surgical techniques may be used to deal with these symptoms.

Summary

The presence of a spondylolisthesis on a scan or X-ray is not in itself an indication for any intervention. Often these deformities may be quite subtle and only a coincidental finding when evaluating for other problems. If symptomatic, however, then Mr Orpen will take this into consideration when making a diagnosis for a cause of pain and in planning the appropriate treatment.

This should be discussed carefully particularly in considering whether surgery may make the slip worse if not dealt with at the time of a decompression of the nerve roots. Also, an indication of movement of the spine and spondylolisthesis may only be evident on standing or bending X-rays rather than on an MRI scan so it is common for this investigations to be performed in conjunction with one another.