This is a condition that results in one vertebral body slipping forwards in relation to the lower vertebral body. The spondylolisthesis can be classified according to the cause or the degree of slip (from 1 to 5). Patients can be asymptomatic – and this can be an incidental finding or they can have a combination of back and leg pain.
The most common type is a degenerative spondylolisthesis with the forward slippage occurring as a result of degenerative changes in the facet joints and intervertebral disc. Patients present over the age of 40 years and it is most common in the sixth decade. Women are four times more likely to be affected than men. Most cases occur at the L4-L5 level (90%) with the L3-L4 and L5-S1 being less commonly affected (10%).
An isthmic spondylolisthesis is less common – and is associated with a defect in the pars interarticularis part of the vertebral body (spondylolysis). This is a posterior structure of the vertebral body that is between the facet joints. There are different types of defects: a lytic defect or stress fracture, an elongation of the pars or an acute pars fracture associated with an injury. Patients with an isthmic spondylolisthesis may be asymptomatic particularly in childhood. Alternatively they present with lower back pain or leg pain as the slip progresses with age.
The precise treatment depends on the patient’s symptoms and ranges from analgesic medication and physiotherapy, through to surgical stabilisation and decompression. In the first instance, nerve root blocks may be administered and can provide prolonged therapeutic benefit. A degenerative spondylolisthesis does not generally progress whereas an isthmic spondylolisthesis can do – and may require stabilisation to prevent further nerve compression.