A stress fracture, medically known as Spondylolysis, is the most common overuse injury of the lower back in sport. This condition is classified as either a bone stress reaction or a stress fracture of the lower back. It is especially common in growing adolescents and symptoms are often related to the ‘growth spurt’. Cricket fast bowlers appear to be particularly susceptible to Spondylolysis, with a reported prevalence of 55% in some teams.
At the base of the back there are five lumbar vertebrae. The most common site for Spondylolysis is the bottom-most lumbar vertebra, called L5, where the mobile lumbar spine meets the fixed pelvis. This is because this vertebra is subject to most stress during sports.
The lumbar vertebra consists of a round block of bone at the front, known as the vertebral body, and a bony ring at the back. Three bony ‘process’ stick out from this ring and provide a place for muscles to attach. The area that is affected by Spondylolysis is a part of the bony ring known as the ‘Pars’. It is not clear why, but the Pars area appears to be a weak spot in the vertebra.
The lumbar spine is required to bear large loads, due to the interaction of body weight with forces generated by sporting movements that involve large muscle forces. These forces are transmitted via the bones of the spine. Bone fatigue occurs in the Pars as a loss of bone strength and stiffness due to repeated loading. This repeated loading is of less force than it would take to produce a traumatic fracture, but because it is repeated over a period of time it eventually causes bone damage. This fatigue eventually causes microscopic cracks to occur across the Pars.
In healthy bone, if damage is not excessive, a biological process called remodeling occurs and new bone is deposited to heal the damage. In order for remodeling to occur, the body must be given adequate rest to recover from the repeated loading that occurs during sport. However, if the damage is excessive and the remodeling cannot keep pace with the damage, then microscopic failures (fractures) occur. This Pars fracture is Spondylolysis.
Signs and symptoms
This condition is most common in adolescents and is quite rare beyond this age group. Spondylolysis is characterised by an ache in the lower back which is exacerbated by sporting activities and eased by rest. Typically, it is sore when the patient bends backwards, particularly if standing on one leg. If Spondylolysis is suspected, a GP may decide to refer the patient for a scan to confirm the diagnosis.
Sporting activities should be practiced on grass if possible. Compared to Astroturf and concrete, grass has some degree of ‘give’ in it that reduces the forces that are transmitted through the spine. Competitive games should be limited to 30 each season and practice sessions should be monitored and extended gradually in frequency, duration and intensity. It is important that adequate rest periods are taken between training sessions and matches, and practices should not be overdone, particularly when participating in activities such as taking throw-ins in football and fast bowling in cricket.
The posture should be monitored. By slouching in a poor posture the back muscles become ineffective in protecting the back from injury. Sitting slumped in front of a computer for long periods should be avoided. The back should be well supported with a Seating Support and regular breaks should be taken.
In the long term, good posture is maintained by increasing the muscular stability of the spine. This can be achieved through specific stabilising exercises known as ‘Core Stability’ exercises. The Stabiliser Pressure Biofeedback Device is very useful at helping to contract the specific muscles that can help prevent Facet joint problems and back pain.