Prenatal rotation of the lumbar spine and its relevance for the development of the zygapophyseal joints.

STUDY
DESIGN: The intrauterine axial rotational characteristics of the lumbar spine were analyzed and quantified sonographically.
OBJECTIVES: To determine whether axial rotational movements of the lumbar spine occur prenatally, which may influence the morphogenesis of the zygapophysial joints. SUMMARY OF BACKGROUND DATA: Previously, the development of lumbar zygapophysial sagittal joint orientation was linked to the increase in torque of the torso as upright posture and locomotion are adopted. However, the potential influence of prenatal axial rotational movement of the lumbar spine on the development of the zygapophysial joints has not been examined.
METHODS: For this study, 52 healthy fetuses, gestation age 9 to 36 weeks, were monitored sonographically for rotational movements of the lumbar spine. By multiplanar reconstruction of the sonography images, exemplary segmental rotational values were acquired. This method was validated by directly measuring the manually induced rotation of the formalin-fixated fetus in addition to multiplanar reconstruction.
RESULTS: Axial rotations of the lumbar spine were seen in most of the examined fetuses ages 9 to 36 gestation weeks. Rotations are best assessable with multiplanar reconstruction in the second trimenon, when segmental rotation of the lower lumbar spine reaches a mean of 8 degrees (range, 4-10 degrees ).
CONCLUSIONS: Fetal axial rotation of the lower lumbar spine reaches a degree that may functionally influence the morphologic development of the articular processes of the zygapophysial joints. In contrast to the prevalent hypothesis, lumbar spine development is already functionally influenced prenatally by axial rotation.