What is Spondylolysis
Spondylolysis is a bony defect or stress fracture of the pars interarticularis (the bony bridge connecting the upper and lower facet joints of the vertebra), most commonly affecting the lower lumbar spine, and represents the most common identifiable cause of low back pain in children and adolescent athletes. 1, 2
Pathophysiology and Mechanism
The defect results from repetitive mechanical stress and cumulative microtrauma rather than a single acute injury, functioning as a stress fracture caused by chronic low-grade trauma to the posterior spinal elements 1, 3, 4
The pars interarticularis is the weakest point in the vertebral arch, making it vulnerable to failure under repetitive loading, particularly during hyperextension and rotational movements 3, 4
The condition can progress through stages: early stress reaction (bone marrow edema without visible fracture) → incomplete fracture → complete fracture with separation → chronic non-union with sclerotic margins 3, 5
Epidemiology and Risk Factors
Spondylolysis accounts for approximately 50% of all back pain cases in pediatric and adolescent athletes, making it the dominant diagnosis in this population 1, 2
Athletes involved in sports requiring repetitive spinal hyperextension and rotation are at highest risk, including gymnastics, diving, football (linemen), weightlifting, and wrestling 2, 3
The L5 vertebra is most commonly affected (approximately 85-95% of cases), followed by L4, due to the biomechanical stress concentration at the lumbosacral junction 3, 4
Many cases remain asymptomatic throughout life, discovered only as incidental radiographic findings 4, 1
Clinical Presentation
The hallmark symptom is activity-related low back pain that worsens with extension-based activities (arching backward) and improves with rest and flexion 1, 2, 4
Physical examination findings are often minimal or absent, though some patients may demonstrate focal tenderness over the affected level, tight hamstrings, or pain with single-leg hyperextension (stork test) 1, 4
Night pain, constant pain unrelieved by rest, or progressive neurological deficits are red flags suggesting alternative or additional pathology requiring urgent evaluation 5
Relationship to Spondylolisthesis
Spondylolysis can lead to spondylolisthesis (forward slippage of one vertebra on another) when bilateral pars defects create spinal instability, though many patients with spondylolysis never develop significant slip 6, 3
The presence of spondylolisthesis increases the likelihood of nerve root compression and may alter treatment recommendations toward more aggressive intervention 7, 6