Lumbar sagittal shape variation vis-à-vis sex during growth: a 3-year follow-up magnetic resonance imaging study in children from the general population

STUDY DESIGN: A longitudinal descriptive magnetic resonance imaging study on the changes of the supine lumbar lordosis (SLL), supine sacral slope (SSS), and sagittal wedging of the vertebral body (VB) and intervertebral discs (IVD) in children from the general population.

OBJECTIVE: To compare the shape variation during growth of the SLL, SSS, and sagittal wedging of the VB and IVD in boys and girls.

SUMMARY OF BACKGROUND DATA: The normal shape variation of the VB, IVD, SLL, and SSS during growth vis-à-vis sex in children from the general population is poorly clarified in the literature as it is usually reported in relation to pathological conditions.

METHODS: The SLL, SSS, and sagittal wedging of all lumbar (L1-S1) VBs and IVDs were measured twice from T2-weighted magnetic resonance images of 100 healthy children (51 boys and 49 girls), at mean age 12 to 13 years (t0) and after approximately 3 years (t1) using the iQ-VIEW system (IMAGE Information Systems Ltd., Plauen, Germany). Data for body compositions and pubertal status were collected, and their correlations were analyzed.

RESULTS: At baseline (t0), most lumbar VBs were significantly more lordotic in boys (17.1º) than in girls (22.2º); however, girls manifested greater SLL and SSS (45.2º and 33.6º, respectively) than boys (40.7º and 31.4º, respectively), and all IVDs were lordotic, with only the L5-S1 IVD differing between sexes, being more lordotic in girls than in boys (mean difference = 2.8º). At follow-up (t1), SSS became greater in boys (35.7º) than in girls (32.5º), yet all other parameters became independent of sex including all IVDs (except L5-S1) becoming significantly more lordotic, and more so in boys than in girls (total lumbar mean differences being 9.0º and 3.8º, respectively). Increase in boys' heights was correlated with the increase in the L2-L4 lordotic IVD wedging (r = 0.45). Positive correlations were indicated between puberty Tanner stage and individual's height and weight (0.41 < r < 0.45).

CONCLUSION: Lumbar VBs decreased their lordotic wedging process during growth, whereas the opposite was observed with the IVDs and SLL, which increased in boys and decreased in girls, becoming independent of sex. The SSS, however, manifested the same process of shape variation, becoming greater in boys than in girls.