Bodily growth and the intervertebral disc: a longitudinal MRI study in healthy adolescents.

Background Context: Low back pain (LBP) among children and adolescents is a growing global concern. Disc degeneration (DD) is considered a significant factor in the clinical symptom of LBP. Both LBP and DD become more prevalent as adolescents transition into emerging adulthood. However, the relationship between growth during the pubertal growth spurt and the morphology of lumbar discs has yet to be elucidated.

Purpose: This study aimed to assess the relationship between bodily growth during the pubertal growth spurt and the morphology of lumbar discs at age 18.

Study Design: This study was a prospective longitudinal cohort study.

Patient Sample: A randomly selected cohort of healthy children was examined at ages 8, 11, and 18. Participants with complete data sets (semi-structured interview, anthropometric measurements and lumbar spine MRI) at age 11 and 18 were included in this analysis (n=59).

Outcome Measures: The morphological characteristics of lumbar discs were evaluated on MRI. Anthropometric measures including height, sitting height and weight were obtained to calculate the Body Surface Area (BSA) and the Body Mass Index (BMI).

Methods: The morphology of the lumbar discs was evaluated on T2-weighted mid-sagittal MRI using the Pfirrmann classification. A disc with a Pfirrmann grade of 3 or higher was considered degenerated at age 18. The relationship between relative growth between ages 11 and 18 (adjusted to sex and baseline values) and DD at age 18 was assessed. To analyze the relationship between the relative increase in BSA and DD, the participants were categorized into three equal-sized categories (tertiles). For all other anthropometric measures, the analysis was based on the relative increase in each measure between ages 11 and 18.

Results: In the highest tertile of relative increase in BSA (≥43%), 76% of participants had at least 1 disc with a Pfirrmann grade 3 or higher at age 18 while only 10% and 21% of participants in the lowest and medium tertiles had DD, respectively. The sex- and baseline-adjusted odds ratio (OR) for DD at age 18 for every additional 10% increase in BSA was 1.08 (1.02-1.15). The sex- and baseline-adjusted OR (95% CI) for DD at age 18 was 10.5 (1.60-68.7) and 7.92 (1.19-52.72) with every additional 10% increase in height and sitting height, respectively. For every additional 10% increase in weight, the adjusted OR for DD at age 18 was 1.51 (1.12-2.04) and for BMI 1.05 (1.01-1.09).

Conclusions: More relative growth between ages 11 and 18 is significantly associated with the occurrence of DD in emerging adulthood. Among the measures investigated, height and sitting height are nonmodifiable. Maintaining an ideal body weight during the pubertal growth spurt may be beneficial for the health of the lumbar discs.