In most adult low back pain presentations, the use of MRI is not recommended due to the poor correlation between structural MRI findings and symptoms. However, in younger athletes, the percentage of presentations that have a definitive pathology is as high as 73%. This is in marked contrast to known pathology being present in adults as being as low as 5-15%.
What is the most common cause of low back pain in youth athletes?
The most common source of low back pain in a youth athlete is a lumbar bone stress injury (LBSI) or spondylolysis, and yet this diagnosis is only found in around 6% of the adult population. The lumbar vertebra does not fully fuse until around the age of 23 so the immature bone is more susceptible to injury than it is after full skeletal maturation. However, not all low back pain in younger athletes is a bone stress injury, so how do we know who might be at risk of a LBSI and who might not?
What questions should we ask?
An accurate subjective assessment will create a strong suspicion of a LBSI in an athlete aged under 23, who has:
- Unilateral low back pain.
- Aggravated by extension related activity and eases with rest.
- Progressively gets easier to provoke symptoms.
In overhead athletes, most young athletes with low back pain, present initially with unilateral low back pain on the contralateral side to their dominant throwing arm. Less is known around laterality and preferred kicking leg in adolescent soccer players, but the condition is often seen bilaterally in gymnasts and rugby players.
Can we test for a lumbar bone stress injury?
There is no gold standard objective test for a LBSI but there are frequent observed patterns. My objective testing supports my suspicions from the subjective assessment, but also confirms where my treatment goals need to be focussed and creates objective markers for reassessment purposes.
The objective markers will be covered in more detail in a further post, however my “go to” tests are:
- Lumbar active extension in standing
- Lumbar extension + side flexion/rotation (depends on sport)
- Glute bridge – double or single
- Long arm prone bridge
Should we scan all adolescent athletes with low back pain?
The only accurate way to diagnose a LBSI is through imaging. MRI has largely replaced both x-ray and CT scans in the diagnosis of lumbar bone stress injuries and with much lower levels of radiation risk allowing the subsequent monitoring and prognosis for bone healing. MRI with VIBE sequences has been reported in one study to be 98% sensitive and 92% specific for the diagnosis of LBSI compared to CT (Ang et al., 2016), however, poor quality imaging, incorrect sequencing or inappropriate protocols and reporting by clinicians inexperienced in lumbar bone stress injuries in adolescents may adversely affect the reliability.
Summary
The most common cause of low back pain in athletes aged 23 and under who are engaged in extension and rotational based sports is a lumbar bone stress injury.
The aim of treatment in this population group should always be to create osseous union (structural) which may offer improved long-term outcomes for the athlete.
Early diagnosis using specific MRI protocols is advocated in young athletic populations involved in extension/rotational based sports, who experience unilateral low back pain of between 2-4 weeks duration.
The only reliable way to understand the potential for healing and the degree of injury to guide informed rehabilitation is to proceed with an early MRI scan. If an MRI scan is not available, the safest form of management is to assume a LBSI is present and proceed with offloading and activity modification and follow the LBSI protocol.
More details about the assessment, diagnosis and management of low back pain can be found in the online course Youth Athlete Low Back Pain or in person on the From Injury to Return to Play in Active Kids course
