The spine consists of a series of vertebrae held together to give support for the spinal cord and nerves arising from it. Each vertebra consists of a solid body with a bony ring behind it. At the top and bottom of this ring are bony protuberances called articular processes which articulate (form a working joint) with the neighbouring vertebrae.
These articulations form the facet joints that provide stability to the spine.
Before a spondylolisthesis can develop there must be a spondylolysis present.
In spondylolysis there is a defect in the pars interarticularis (which literally means the "piece between the articulations").
So spondylolysis means a defect in the thin piece of bone connecting the upper and lower facets, and can be unilateral (involving one side) or bilateral (involving both sides). Although the defect can be found at any level, the commonest vertebra involved is the 5th Lumbar vertebra (or L5).
In cases of bilateral spondylolysis, the posterior articulations can no longer provide the posterior stability, and anterior slipping of the L5 vertebra over the sacrum could result. This slip itself is called Spondylolisthesis.
Using the lateral (side) x-ray, the slip is graded according to its degree of severity. The Myerding grading system measures the percentage of vertebral slip forward over the body beneath. The grades are as follows:
Grade 1: 25%
*Complete vertebral slippage, known as spondyloptosis.
What causes it?
The commonest cause of spondylolisthesis is spondylolysis, however, the cause of spondylolysis is the subject of much debate. Some experts feel that it is an inherited defect of the pars interarticularis. In surveys of school children, spondylolysis is present in 4% to 6% of cases even when the child has no symptoms.
Among the Eskimos, the incidence is as high as 40%, perhaps suggesting a genetic factor. Conversely, it has been postulated that the high prevalence of pars defects in the Alaskan Eskimos could be due to carrying infants in a papoose which places an undue amount of premature stress on the pars interarticularis. This keeps the infant in an upright position for extended periods of time and these devices may cause their children to develop pars defects.
Closer to home parents should avoid the use of an upright walker until the child can walk unassisted as overloading bones not yet strong enough to take the weight of the body may cause pars fractures.
However, certain other observations point to repetitive trauma causation. Incidence goes up with age, and incidence is higher in children involved in certain kinds of sports like gymnastics, weight-lifting and football that put a lot of stress on the back.
In gymnastics, the hyperextension position of the lumbar spine places excessive stress on the back, leading to stress fractures in the pars interarticularis.
In an attempt to unify the two causative theories, some physicians believe that most children with spondylolysis may be born with a "weak" pars interarticularis. Repeated stress with activities during the years of growth between 8 and 14 causes the "stress fracture" that leads on the spondylolysis.
The red arrows show the pars fracture in this
15 year old male basketball player
that often accompany spondylolisthesis:
· Pain in the low back, especially after exercise
· Increased lordosis (i.e., swayback)
· Pain and/or weakness in one or both thighs or legs
· Reduced ability to control bowel and bladder functions
· Tight hamstring musculature
In cases of advanced spondylolisthesis changes may occur in the way people stand and walk such as the development of a waddling style of walking. This causes the abdomen to protrude further, due to the low back curving forward more. The torso (chest, etc.) may seem shorter; and muscle spasms in the low back may occur.
Spondylolisthesis typical posture may include:
· Short torso (body)
· Flat buttocks
· Rib cage appears low
· Iliac crests (hip bones) are high
· Altered gait because of tight hamstrings
· Vertical sacrum
· Hips don't fully extend back
However, most children with spondylolysis, and even some children with spondylolisthesis may not experience back pain and may grow up unaware that they have the condition.
For those with symptoms, back pain is probably the most common symptom, and often presents during the adolescent growth spurt. There is often a history of trauma at sports, usually trivial, and an X-ray reveals the "fracture". In adolescents, boys are affected 2 to 3 times more often than girls. However, at times the spondylolysis is not due to that particular injury, but a result of years of cumulative stress of the back.
Sometimes the child is brought in by the parents because of poor posture or funny gait. This is usually due to spondylolisthesis, causing muscle spasm in the back that makes the back stiff, and tight hamstrings causing the child to walk with the knees bent, and a short stride. Sometimes, there is an associated scoliosis that is more obvious to the observer than the spondylolisthesis.
The two x-ray images show a spondylolysis in a 16 year old footballer in the picture above left, and a spondylolysis in a 14 year old hockey player on the right.
How do you prevent it?
There is nothing you can do about your genes, but there is certainly something you can do about your activities.
Avoiding sports in the growing years is usually not an option, but you can choose your sports wisely. For your little gymnast, limiting the number of hours of practice (unless she is an aspiring Olympian), or alternating gymnastics with another sport like swimming or bicycling may be helpful. And there is no place for weight lifting in the pre-pubertal child.
with a higher risk of spondylolysis/spondylolisthesis include:
· Pole vaulters
· Weight lifters
· High jumpers
In adults, spondylolisthesis is usually caused by degenerative disk disease and often affects women over 40 years of age.
Degenerative disc on the left, normal healthy disc on the right
With aging, discs lose water content and ultimately height. As the vertebra on either side of the disc come closer to each other through the loss of disc height, the upper vertebra may slide forward on the sub-adjacent vertebra producing spondylolisthesis.
Spondylolisthesis is also associated with deterioration of the facet joints connecting the two vertebrae. As the facet joints become arthritic due to this deterioration, they enlarge in an attempt to confer stability. As the two rings of the vertebral segments which make up the spinal canal, slide past each other, the canal narrows in size. The combination of canal narrowing and enlargement of the facet joints, produces the characteristic nerve compression problems found in degenerative spondylolisthesis. The nerves are compressed in two major areas at the site of a degenerative spondylolisthesis. It is believed that a reduction in nerve blood flow accounts for the symptoms produced from spinal canal narrowing.
The role of chiropractic
Specialised advanced chiropractic treatments for Spondylolysis and Spondylolisthesis have been developed over the years and have great success in both relieving symptoms and providing greater stability. At the Holdfast Bay Musculoskeletal Centre we utilise the Cox mechanised flexion-distraction technique in treating these problems. The treatment is very gentle, quite pleasant to undergo, and brings pleasing results.
The role of rehabilitation
It is important that individual patient weaknesses are assessed and that a program is prepared which is specific to their needs. The goals of exercise are to improve back and abdominal strength and increase flexibility. Since tight hamstrings are almost always part of the clinical picture, appropriate hamstring stretching is important. Instruction in pelvic tilt exercises may help reduce any postural component causing increased lumbar lordosis. Myofascial release may play a role as well in reducing pain from the soft tissue component.
Surgery becomes necessary only if all of the above treatments fail to keep the patient relatively free of pain, or at least keep it at a tolerable level. Surgical treatment for Spondylolysis and Spondylolisthesis must address both the mechanical symptoms and the compressive symptoms if they are present and when indicated can be quite successful.