Spondylolysis is an overuse injury in which there is a repeated stress to an area of the vertebral column called the pars causing a stress fracture.
The spinal column is made up of individual units called vertebrae mounted atop each other with interposing discs. The pars interarticularis also called the pars in an obscure area of the vertebra in the region of the facet. This area being small is a weak link in the vertebrae that is often subjected to high amounts of compressive load. It has been proposed that this region is particularly vulnerable when the spine is in an extended position and force suddenly compresses through the spinal column, such as landing on the foot after a hop. It occurs most commonly at the fifth lumbar vertebrae, which is the last mobile segment in the spinal column. However it may occur at any of the other lumbar as well as thoracic vertebrae.
Spondylolysis affects 4-6% of the population. It is especially common in adolescents who engage in competitive sports. This leads to an over training of certain biomechanics imposing repetitive stress. The various sports where this is a common occurrence are gymnastics, dance, tennis and cricket. In these sports the spine is bent forward, bent back and rotated many times creating a mechanical stress. While spondylolysis is much more common in youths, it can occur in the general population too. Two main factors which are strongly associated with its incidence in the general population are obesity and aging. Obesity causes an increase the natural curve of the lumbar spine, i.e. lordosis, leading to increase stress and load on the spine. Aging on the other hand causes loss of bone density which can lead to a stress fracture. Spondylolysis is also found to run in families and is more prevalent in some populations suggesting a hereditary component.
Symptoms of spondylolysis include back pain which is exacerbated with activities particularly those involving hyperextension (excessive backward bending). Often people have tightness in the hamstring which is a reflex created by the body to guard the back. Spondylolysis often leads to spondylolisthesis which is a forward slipping of the vertebral body since its attachment to the posterior elements of the vertebra is defected. This is a more serious condition as the instability has a possibility of a nerve compression.
The diagnosis of spondylolysis is made by oblique lumbar spine X-rays. An oblique x-ray of the lumbar spine shows what appears to be a “scotty dog”. It is in the area of the dog's collar that the fracture occurs. CT scans and MRI may be used to diagnose the condition as well.
An early diagnosis is the key to treatment for spondylolysis as temporarily stopping the sporting activity is necessary for the bone to heal. In most cases this is a period of 4-6 weeks during which conservative treatment in the form of wearing a brace and physiotherapy are imperative. Physiotherapy treatment includes use of modalities to reduce the pain and more importantly spinal stabilization exercises for the core and pelvic floor muscles. Additionally motor control training to reduce postural lordosis and hyperextension during dynamic activities such as sports ensures correct biomechanics without imposing undue stress to the area in the future.