May 2017: “The Unstable Back”
Spondylolisthesis is a term which refers to the forward slippage of one vertebral body on the subjacent vertebral body. “Spondylo” is from ancient Greek and refers to the spine and “listhesis” refers to the slippage or sliding.
There can be many causes for this slippage. One of them is a defect or “fracture” that occurs in the lower part of the lumbar spine. Approximately 1% of the population can be born with this “fracture” or defect in the pars interarticularis. A further 3% or 4% of the population will develop this “defect” over the next three or four years of life. That is to say, 4% or 5% of the normal population six years or more will have this defect.
A subset of this population will then develop the forward slippage of one of the affected vertebra on the subjacent vertebra. This is a so-called “lytic spondylolisthesis”.
Despite the dramatic appearance of these changes on radiographs of the vertebral column, most of these patients remain asymptomatic. They are not aware that the condition exists.
A further small subset will be aware of previous problems. Those patients suffer with degeneration of the disc between the two mobile vertebral segments. The changes are often witnessed on plane radiographs with narrowing of the disc space and other degenerative changes.
Patients with this condition, asymptomatic and unaware of its existence, can also be subjected to injuries in the workplace, just as the rest of us can. Radiographic examinations reveal the underlying problem and stimulate great interest from all concerned.
There is a temptation to attribute the ongoing clinical symptom complex to this underlying condition and ignore the effects of the subject workplace accident.
Careful orthopaedic analysis is required. If the patient was truly asymptomatic prior to the accident and there were no features that indicated to the contrary, then it might be reasonable to assume that the accident has caused the ongoing clinical circumstance. Conversely, if it can be demonstrated with confidence that the antecedent condition had been symptomatic prior to the accident, the accident may have given rise to either nothing more than a temporary exacerbation or alternatively, a permanent aggravation of the pre-existent condition. Apportionment of blame will be necessary.