Lumbosacral lordosis in fetal spine: genetic or mechanic parameter

Abstract

Many believe that the fetus spine had only one curvature from cranial to caudal which is a global kyphosis and that the lumbosacral lordosis appears with the erect posture. They agree that the sacrum of Homo sapiens is not positioned posteriorly at birth and that it is during the first few years that the sacrum, in humans, moves dorsally in relation with the progressive acquisition of erect posture and the ontogeny of bipedal locomotion. Nevertheless, there is no biometric study assessing these parameters in vivo in utero during the fetal life. Cross-sectional biometric study of the lumbosacral junction of the spine in in utero fetuses was to document the presence of a lumbosacral lordosis in the fetal population in utero long before standing and walking and its change during growth. Fortyfive MRIs (magnetic resonance imaging) of fetuses aged of 23-40 weeks of gestation were analyzed. The measurements were performed on computerized MRI DICOM images using a professional software to calculate the curvature and radius of the lumbosacral junction. The presence or absence of visual lumbosacral lordosis was noted for each case. Correlation tests were performed in order to disclose a correlation between the gestational age and the curvature calculated. A test was considered significant for P \ 0.01. There were 14 males, 17 females and 14 undetermined. All the curves (100%) showed mathematically the presence of a lordosis in the lumbosacral region. The visual lumbosacral lordosis was present in 60% of cases. The measurement of the lumbosacral curvature varies between -0.133 and -0.033 mm -1 and a mean of -0.054 mm -1 with a corresponding radius ranging from -7 to -303 mm with a mean of -18.7 mm. The statistical analysis showed no correlation between the gestational age and the lumbosacral curvature (R 2 = 0.11). The hypothesis of increased lumbosacral lordosis with gestational age is rejected. It is difficult to accurately determine the role played separately by genetics and by erect posture. A visual lumbosacral lordosis was noted in 60% of cases with mean radius of -18.6691 mm. This lordosis was not correlated statistically to gestational age which means that it is not related to growth and might be genetically determined. Mechanical factors may play a major role in the determination of the shape of the growing pelvis. One can ask if the pelvis morphology is genetically determined or if it is mechanically determined under muscular and ligamentous stresses. This study shows that the sacrum of human fetuses is oriented posteriorly mathematically in 100% of cases, and in 60% of cases based on the morphologic appearance of the lumbosacral junction. So beside the effect of progressive acquisition of erect posture and bipedalism in determining the formation of lumbosacral angle, we believe that genetics play an important role in the formation of the lumbosacral angle.

Development of Pelvic Incidence and Lumbar Lordosis in Children and Adolescents

“…Our youngest subjects were 2 years old and, by that age, most children have already begun to walk and vertically load their spines. The presence of lordosis at the L5-S1 segment during in utero development has been reported in one study (Choufani et al, 2009). The PI of neonates (27.2 AE 12.8) is less pronounced than that of children who are old enough to walk unassisted (Table 3).…”

Trajectories of childhood body mass index are associated with adolescent sagittal standing posture

“…In contrast, a longitudinal study of 11 to 22‐year‐olds found no relationship between BMI and the development of thoracic kyphosis (16). Sagittal spinal posture development may be influenced by genetics (17), gender (16,18–22), exercise levels (23), height (14), school furniture (24) and generation (25).…”

Variability of body build and physiological spinal curvatures of young people in an accelerated longitudinal study

“…The human body, including the spinal curvatures, changes during ontogeny and phylogeny [1,2], which is reflected by the instability of characteristics and indicators of body build and posture. The period of ontogenetic stabilization between 20 and 40 years of age, accompanied by the inhibition of growth processes and establishment of body proportions does not guarantee discontinuation of the variability of physiological spinal curvatures.…”