INTRODUCTION: It is well known that lumbar disc herniation is common in adults and usually occurs upon disc degeneration, a progressive structural failure of the disc. Lumbar disc herniation in teenagers, referred as juvenile disc herniation (JDH), is rare. Etiologies of JDH, the patients have not experienced long time exposure of environmental risks. JDH patients, therefore, can be a suitable population for genetic studies. Characteristics of JDH have not been well investigated due to its rarity. Besides, the suspected etiological factors were not comprehensively investigated in published studies. This case control study, including possible physical and social risk factors like positive injury history, daily sitting time and familial aggregation, and MR findings like epiphyseal ring fractures, endplate defects, Modic changes and facet joint asymmetry, attempted to investigate the key risk factor in JDH patients.
METHODS: Patients aged 20 years or younger with electronic medical record of lumbar disc herniation and related MR features were selected. By recalling to the selected 248 JDH patients, the structured questionnaire was further filled out and analyzed. Fifty-four age and sex matched participants without findings of lumbar disc herniation on MR images were selected as controls. All patients and controls were investigated for back injury history, daily waist exposures, family histories and MR findings. The medical records of injury history, waist exposures in daily life and family histories were measured using a structured questionnaire. The type and level of disc herniation, the Pfirrmann score, the presence of epiphyseal ring fractures, endplate defects and other reported MR findings of the lumbosacral spine were evaluated on magnetic resonance images. Descriptive statistics were used to characterize demographics, environmental exposures, family histories, and MRI findings for JDH patients. Chi-square test was used to analyze the categorical variables of JDH patients and subjects in the control group.
RESULTS: Positive family history of lumbar disc herniation was the most important risk factor for JDH. Nearly half of patients (44.1%) with questionnaire data had a positive family history of lumbar disc herniation with significance (P<0.001) to age and sex matched controls. Besides, 50.5% patients with MR images had disc and endplate findings at multiple lumbar spinal levels. Additionally, epiphyseal ring fractures were found in 31.0% JDH patients and were the most prominent significant (P<0.001) MR findings between patients and controls. Degenerative findings like high Pfirrmann score (more than and equal to Ⅳ), Modic changes and high intensity zone were rare. Patients with waist injury (11.0%), large body weight (6.8%) and heavy physical labor (0%) accounted for small proportions.
DISCUSSION: Familial aggregation of lumbar disc herniation and MR findings at multiple levels indicate that JDH is more likely a genetic disorder and disc degeneration does not appear to play a major role in JDH.