Mr James Langdon

BSc (Hons) MB BS MRCS (Eng) FRCS (Orth) Consultant Orthopaedic Spinal Surgeon


A spondylolysis is a bony defect in the pars interarticularis. The pars interarticularis is a part of a lamina. The lamina is the bony arch that forms the back part of a vertebra. A spondylolysis is also known as a pars defect.

A spondylolysis is often thought to be a stress fracture. The condition most commonly presents with back pain in teenagers or young adults. Spondylolysis occurs in approximately 6% of teenagers, though is most commonly seen in young sportsmen and women. There is an increased risk with sports that involve a lot of arching of the lower back, such as gymnastics, butterfly swimming, diving, and fast bowling. A spondylolysis usually occurs at the L5 level in the lower back. A spondylolysis can progress to a spondylolisthesis.


A spondylolysis can be diagnosed by x-ray, MRI or CT scans.

Treatment of spondylolysis

The initial management of a spondylolysis is a period of rest and abstinence from sport. This is followed by trunk and abdominal strengthening exercises, guided by a physical therapist, and a gradual return to sport.

Surgery is normally only considered if non-operative measures have failed to relieve your symptoms. A surgical repair of the pars defect may be sufficient in younger patients; in older patients or in those with some degree of instability, a fusion may be required.


A spondylolisthesis is when one vertebral body slips forwards relative to the vertebral body beneath it. This will produce both a gradual deformity of the lower spine but also a narrowing of the spinal canal and the exit foramen. The exit foramen are where the nerves exit the spine. A spondylolisthesis can cause pain in the back, pain in the legs, or both.

Spondylolistheses are classified by their cause. The commonest types are lytic and degenerative spondylolisthesis:

Lytic spondylolisthesis: This is a spondylolisthesis that occurs in a vertebra previously affected with a spondylolysis. This typically occurs at the L5/S1 level.

Degenerative spondylolisthesis: A degenerative spondylolisthesis occurs as a result of the degeneration of the lumbar facet joints. This degenerative changes lead to an alteration in the shape of these joints, meaning that there is less bony resistance to abnormal movement. A degenerative spondylolisthesis is most often seen in older patients, and typically occurs at the L4/5 level.

A spondylolisthesis can also occur due to a congenital abnormality of the posterior spine (Dysplastic), following trauma (Post-traumatic), due to a weakness secondary to a bone disease or tumour (Pathologic), or following previous lower back surgery (Iatrogenic).

The severity of a spondylolisthesis is classified according to the percentage of slip relative to the vertebral body below. A slip of 0-25% is classified as grade 1, a slip of 25-50% is classified as grade 2, a slip of 50-75% is classified as grade 3, and a slip of 75-100% is classified as grade 4.   If the vertebral body slips completely off the front of the vertebra below then this is termed a spondyloptosis, or grade 5 spondylolisthesis. The degree of vertebral slippage does not directly correlate with the amount of pain a patient will experience.


A spondylolisthesis can be diagnosed by a MRI scan or x-ray. Occasionally a patient will also require a CT scan.

Treatment of a spondylolisthesis

The initial treatment is normally physical therapy from a physiotherapist, chiropractor or osteopath. The aim of this treatment is to strengthen the muscles that support the spine to compensate for the instability caused by the spondylolisthesis. If this fails to give satisfactory relief then some form of cortisone injection would normally be considered. These should be done in conjunction with further rehabilitation.

If symptoms persist despite non-operative measures, or if there are significant neurological symptoms due to nerve compression then surgery may be required. This would normally be either a decompression operation to relieve the pressure on the nerves, or a decompression and fusion to relieve the pressure on the nerves and prevent further slippage. The type of surgery will depend on the cause of the spondylolisthesis and the type of symptoms being experienced.