Lumbar Spondylolysis
Stress fracture of the pars interarticularis causing low back pain in young athletes
ICD-10: M43.06 · lumbar condition
Lumbar spondylolysis is a stress fracture or structural defect of the pars interarticularis — the narrow isthmus of bone in the posterior neural arch connecting the superior and inferior articular processes. It is the most common cause of low back pain in adolescent athletes, accounting for up to 47% of athletic low back pain presentations. The L5 level is affected in approximately 90% of cases. The pars fracture typically results from repetitive hyperextension and rotation loading — movements inherent to gymnastics, football lineman play, wrestling, dance, and rowing. The injury begins as a stress reaction (marrow edema without a visible fracture line on CT) and may progress to a frank cortical fracture, bilateral defects, and ultimately spondylolisthesis (forward slip) if not treated promptly. Diagnosis requires clinical suspicion in young athletes with extension-provoked low back pain. MRI is the preferred first study in adolescents (no radiation), identifying early stress reactions before CT cortical fracture. Single-photon emission CT (SPECT) is highly sensitive for active lesions. Management is directed at the activity stage: early lesions without a cortical break can heal with bracing and rest; established fractures with sclerotic margins rarely heal but become asymptomatic with activity modification; bilateral defects with slip progression may require surgical fusion.
Anatomy & Pathology
The pars interarticularis is the isthmus between the superior articular process (which faces posteriorly and connects to the vertebra above) and the inferior articular process (which faces anteriorly and connects to the vertebra below). At L5, this segment is particularly vulnerable because it must resist large shear forces generated by the lumbosacral angle. Bilateral pars fractures at any level disconnect the posterior element from the vertebral body, potentially allowing forward slippage.
Symptoms
- Low back pain localized to the L4–L5 or L5–S1 level, worse with extension
- Pain provoked by single-leg lumbar hyperextension test (stork test)
- Hamstring tightness and spasm
- Pain with activity and relief with rest
- Tenderness over the lower lumbar paraspinals
- Absence of neurological deficits in isolated spondylolysis (no slip)
- Insidious onset in young athletes with no single traumatic event
Causes & Risk Factors
- Repetitive hyperextension and rotational loading in adolescent athletes
- High-risk sports: gymnastics, diving, football lineman, wrestling, rowing, cricket fast bowling
- Genetic predisposition — higher prevalence in certain ethnic groups (Inuit) and families
- Rapid adolescent growth spurts reducing bone mineralization relative to mechanical demand
- Lumbar hyperlordosis increasing pars stress concentration
Imaging Findings
Imaging studies are commonly used to identify findings associated with this condition. Results vary by individual; a qualified spine specialist interprets findings in the context of a full clinical evaluation.
MRI
- Pars interarticularis stress reaction: T2 hyperintensity (marrow edema) at the pars before fracture is complete — the earliest MRI sign
- Completed pars fracture: low T1 and T2 signal at the isthmus with surrounding edema
- Spondylolisthesis (forward slip) graded by Meyerding classification: Grade I (less than 25% slip) through Grade IV (greater than 75%)
- Nerve root compression from foraminal stenosis when spondylolisthesis is present
- Note: MRI detects early stress reactions before X-ray or CT changes — preferred for initial diagnosis in young athletes
CT Scan
- Definitive characterization of pars fracture — acute (clean margins), chronic (sclerosis), or fibrous non-union
- Bilateral vs unilateral fracture assessment — bilateral fractures at L5 cause most isthmic spondylolisthesis
- SPECT-CT: combined SPECT (metabolic activity) with CT (anatomy) provides highest sensitivity for active pars lesions
X-Ray
- Oblique lumbar views: the Scottie dog sign — fracture through the pars appears as a collar on the neck of the Scottie dog
- Lateral view: spondylolisthesis slip percentage measurement at L5-S1 (most common level)
- AP view: inverted Napoleon hat sign in high-grade spondylolisthesis
Who Is Commonly Affected
The following patterns are commonly associated with this condition based on published population studies. Individual presentation varies; these figures are informational only.
Peak Age Range
Initial fracture typically 8–15 years in athletes; symptomatic spondylolisthesis progression in young adults
Gender Distribution
Male predominance in sports-related cases (hyperextension sports such as gymnastics, football, cricket); female predominance in high-grade spondylolisthesis
Estimated Prevalence
Pars defects present in approximately 5–6% of the general population; up to 30–50% in athletes involved in hyperextension activities; L5 affected in approximately 90% of cases
Treatment Options
Conservative
- Activity restriction and thoracolumbosacral orthosis (TLSO) bracing for 3–6 months for acute/early lesions
- Physical therapy after pain resolves: core stabilization, hamstring flexibility, lumbar extension avoidance
- Gradual return-to-sport protocol under supervision once pain-free and bracing complete
Surgical
- Direct pars repair (Buck screw, Scott wire/hook-screw technique) for symptomatic unilateral pars defects in young athletes without slip
- Posterior spinal fusion (L5–S1) for bilateral defects with spondylolisthesis failing conservative care
- Minimally invasive pars repair techniques in experienced centers
When to see a spine specialist
Young athletes with low back pain lasting more than 2 weeks, particularly if worsened by lumbar extension, should be evaluated for spondylolysis before returning to sport. Early diagnosis and bracing significantly improves healing rates. If a pars defect is identified, sports medicine or pediatric spine consultation is recommended to guide activity restriction and treatment.
Specialists Who Treat Lumbar Spondylolysis
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Questions to Ask Your Doctor
Bring these questions to your next appointment about lumbar spondylolysis.
- 1
Is my pars fracture acute (showing marrow edema on MRI) or chronic (sclerotic on CT) — and does that determine whether it can heal with bracing?
- 2
Am I at risk of progression to spondylolisthesis (forward slippage), and what percentage of slip do I currently have?
- 3
What is the minimum time I need to restrict activity, and what criteria determine when I can safely return to sport?
- 4
Is bracing necessary, and if so, what type and how many hours per day?
- 5
If conservative treatment fails after 6 months, what are the surgical options — direct pars repair versus fusion?
Research Evidence
No studies reviewed yet for this condition. Check back soon — our evidence pipeline runs nightly.
Clinical Evidence
Frequently Asked Questions
What is the stork test and how accurate is it for spondylolysis?
The stork test (single-leg hyperextension test) is performed by having the patient balance on one leg and extend the lumbar spine. Reproduction of ipsilateral low back pain is considered positive. It has moderate sensitivity (50–73%) and specificity (17–35%) for pars defects. A positive test in a young athlete with appropriate history warrants imaging (MRI or CT) to confirm or exclude spondylolysis.
Will a pars fracture heal completely with bracing?
Healing probability depends on the stage of the lesion. MRI-detected stress reactions without cortical fracture (early lesions) have healing rates of 73–100% with bracing and activity restriction. Frank cortical fractures with a visible fracture line on CT have lower healing rates (25–60%) depending on fracture orientation. Chronic sclerotic pars defects rarely heal but typically become asymptomatic. SPECT scan activity correlates with healing potential.
Can a gymnast return to elite competition after spondylolysis?
Many gymnasts successfully return to elite competition after spondylolysis treatment. Complete healing of the pars (confirmed by CT) typically allows unrestricted return. Even non-healed but asymptomatic pars defects are compatible with high-level gymnastics in many athletes with appropriate core training and monitoring. Athletes with bilateral defects and spondylolisthesis have higher recurrence and progression risk and require more careful long-term monitoring.