Spondylosis, Spondylolysis and Spondylolisthesis.

These three terms are similar and often give rise to some confusion.

Spondylosis refers to a degenerative process which affects the structures between the vertebrae of the spinal column. It is initiated by degeneration of the intervertebral disc which then leads to a number of degenerative changes in the surrounding tissues. This condition is considered under ‘spinal degeneration’.

Spondylolysis (break in vertebra) is a non-union of a fracture of the pars interarticularis i.e. the portion at the back of the vertebra between the superior (upper) and inferior (lower) articular facets of the posterior elements. It typically occurs in adolescents or young adults, usually in the lower lumbar spine, as a result of hyperextension (excessive backward bending) of the spine during a sporting activity such as gymnastics and trampolining. It may also occur as a result of a fall. It is thought that the inferior articular facet of the vertebra above is excessively long and, when the spine is forcibly extended back, it crushes the pars interarticularis of the vertebra below, causing it to break.

The break in the bone may painful at that time. A radiograph or CAT scan taken during this period will show the typical break in the bone which then often heals spontaneously or after a period of enforced rest.  At this time reduction in physical activities, combined with a spinal support, may allow this fracture to heal.

If the spondylolysis is not picked up at the time of injury it may take one of four courses.

  • Firstly it may heal spontaneously by itself and cause no further problem.
  • Secondly the initial pain is slight and the spondylolysis remains undetected throughout the life of the affected individual.
  • Thirdly the affected individual may begin to experience significant pain in the lower back. This usually begins during late adolescence, or early adulthood. If this occurs non-operative treatment, even at this stage, may prove successful. If, however, the bony lysis still does not heal there may be an indication for surgical treatment during which the spondylolysis may be ‘repaired’ with a bone graft, with or without a surgical implant.
  • Fourthly the broken pars interarticularis lengthens as the vertebral body slips forward over the lower vertebral body giving rise to a spondylolisthesis (see below) which may. or may not, require surgical treatment.

Spondylolysthesis (a slippage of the vertebra) is where the body of one vertebra slips forward over the body of the vertebra immediately below it. The severity of the slip is usually graded by the proportion of slip as measured on a lateral radiograph as a percentage of is body the upper vertebra has moved forward. Alternative the slip is graded 1 to 5 as measured in quarter increments, with 5 being a total slip off the lower vertebra. This condition is usually the result of one of three preceding causes:

  1. An existing spondylolysis of the spine.

In a normal spine the lower facet joint of a vertebra acts as a ‘hook’ which prevents any forward movement of the vertebra underneath. If this ‘hook’ breaks and does not heal, as with a spondylolysis, the vertebra may begin to slip forward in a number of cases.

Spondylolytic spondylolisthesis

The condition has a tendency to self stabilize. Advantage can be taken of this fact by initially treating it non-operatively, providing there is no undue pain or discomfort or a continuing progression of the slip. There remains still, however, a small chance that the upper vertebra can continue to slip until it ‘falls off’ the front of the lower vertebra. For this reason regular follow up assessments need to be performed by the treating doctor. Continuing pain in the back and/or leg, continuing or excessive slippage, pain and/or numbness down the leg, or there is evidence of arthritic degeneration of the spine at that level, may be an indication for surgery.

Surgery for this condition requires a bone graft to the area. Often surgical implants are used to supplement the fusion and an attempt to reduce the amount of slippage of the vertebra is usually incorporated in the technique.


 2.Severe arthritis (spondylosis) of the spine

Spondylosis of the spine begins with degeneration of the intervertebral disc. This degeneration, in turn leads to instability of the spine at the affected level. This, in turn, leads to an arthritis of the facet joints the result or which is the retaining vertebral ‘hook’ wears away and allows the upper vertebra to slip forward.

Degenerative Spondylolisthesis

This condition usually presents in people during their mid or later life The pain in the back is often severe and is often accompanied by pain and numbness down one or both legs which makes walking difficult. Non-operative treatment may help, particularly in the elderly. This can include spinal exercises, spinal supports and spinal injections. Nevertheless, many people can remain incapacitated, In this instance surgery is often invaluable. This surgery usually includes a spinal decompression and spinal fusion of the affected level. Again spinal implants are commonly used to augment the fusion.


   3. Softening of the bone

Spondylolysthesis as a result of soft bone is relatively uncommon but can be found in children and adolescents suffering from Osteogenesis imperfecta (Brittle bone disease). In these children the fibrous tissue which is normally found in bone is abnormal, which makes the bone weak and brittle. As a result they are susceptible to experiencing multiple fractures of the bone throughout their bodies. As a result of this condition the pars interarticulosis of a vertebra may lengthen, leading to the affected vertebra slipping forward.