This is the only prospective natural history study of spondylolysis and spondylolisthesis in a population unselected for pain. Initiated in 1955 with radiographs of 500 first-grade children, it followed 30 subjects with pars defects for over 45 years. The study answers a fundamental question: what actually happens to these patients over a lifetime?
When a parent asks whether their child's pars defect will ruin their back or end their athletic career, this study is your answer. The key numbers: unilateral defects never progress to slip. Bilateral L5 defects carry a 5% lifetime risk of symptomatic progression — not the 20-23% figure that clinic-based studies suggest, which are inflated by selection bias toward symptomatic patients.
When you see a child or adolescent with bilateral L5 pars defects, no baseline measurement (slip percentage, lumbar index, slip angle, age at onset) predicts ultimate outcome. Watchful waiting is appropriate, and sports restriction is not supported by this evidence.
The one actionable imaging threshold: once slip exceeds 15%, expect at least moderate L5-S1 disc degeneration on MRI. This is not a reason for surgery, but it shapes your conversation about long-term disc health.
This is the only prospective natural history study of spondylolysis and spondylolisthesis in a population unselected for pain. Initiated in 1955 with radiographs of 500 first-grade children, it followed 30 subjects with pars defects for over 45 years. The study answers a fundamental question: what actually happens to these patients over a lifetime?
When a parent asks whether their child's pars defect will ruin their back or end their athletic career, this study is your answer. The key numbers: unilateral defects never progress to slip. Bilateral L5 defects carry a 5% lifetime risk of symptomatic progression — not the 20-23% figure that clinic-based studies suggest, which are inflated by selection bias toward symptomatic patients.
When you see a child or adolescent with bilateral L5 pars defects, no baseline measurement (slip percentage, lumbar index, slip angle, age at onset) predicts ultimate outcome. Watchful waiting is appropriate, and sports restriction is not supported by this evidence.
The one actionable imaging threshold: once slip exceeds 15%, expect at least moderate L5-S1 disc degeneration on MRI. This is not a reason for surgery, but it shapes your conversation about long-term disc health.