Spondylolisthesis simply means the abnormal slip of one vertebra with respect to the vertebra immediately below. This is usually occurs forwards (anteriorly) of the upper vertebra, also known as anterolisthesis. Less common is a backwards (posterior) slip, also known as retrolisthesis. Much less common is a sideways (lateral) slip, called a laterolisthesis.
There are four grades of severity of slip, determined by the amount that the upper vertebra has slipped in relation to the lower one. A slip of less than 25% is grade 1, 25-50% is grade 2, 50-75% is grade 3 and 75-100% is grade 4.
Degenerative spondylolisthesis usually occurs in older women, most often at L4/5, but can occur at other levels. This type of slip is due to degeneration of the pair of facet joints between the two affected vertebrae.
The slip may cause either low back pain and / or symptoms related to nerve compression, which include leg weakness, leg numbness or tingling within the legs. The area of the leg affected depends upon which of the nerves is being compressed.
Lytic or spondylolytic
Lytic spondylolisthesis usually occurs at L5/S1 and normally presents in the teenage years or 20s. The classical example is the so-called fast (cricket) bowler’s “stress fracture”. It occurs due to repetitive stresses in the lumbar spine but it often appears with no obvious history of repetitive trauma.
There is an acquired fracture through the portion of the vertebra between the two articular processes. This part of the vertebra is called the pars or pars interarticularis, meaning the part of the vertebra between the adjacent two facet joints.
What are the treatment options?
Simple pain control, using over the counter medication such as Paracetamol or anti inflammmatories, such as Ibuprofen can be helpful. Symptoms may improve with physiotherapy to strengthen the inner core muscles. Some patients are also happy to adjust their activity levels.
Caudal epidurals, nerve blocks or pars injection in case of lytic spondylolisthesis may be useful in planning surgery, or providing pain relief for those patients not imminently undergoing surgery.
Surgery may be considered when there is pressure on the nerves causing leg pain or weakness, or for back pain due to instability.
Lumbar decompression is used to relieve the pain within the legs caused by nerve compression. This may be combined with an instrumented fusion.
Lytic spondylolisthesis may be treated with a lumbar fusion, though occasionally the lytic area can be repaired, thus avoiding a fusion between the two veretbrae.