[The lumbosacral transition: morphologic variations and their functional significance].

Area of Science:

• Anatomy
• Biomechanics
• Spinal Morphology

Context:

• The articular facet of the superior articular process of the sacrum exhibits significant variations in orientation.
• Four angles (relative tilt, absolute tilt, tilted part-angle of opening, horizontal part-angle of opening) characterize facet orientation.
• These angles are determined by facet geometry and reference planes (sacrum, horizontal, sagittal).

Purpose:

• To define and analyze the geometric orientation of sacral articular facets.
• To investigate the relationship between facet orientation and spinal parameters like pelvic inclination and lumbosacral angle.
• To assess the impact of vertebral anomalies on lumbosacral stability.

Summary:

• Facet orientation is primarily determined by dynamic factors, not static moments, pelvic, or sacral inclination.
• The absolute angle of tilt correlates with sacral inclination, while relative tilt remains relatively constant.
• Lumbosacral transitional vertebrae significantly compromise the stability of the lumbosacral region.

Impact:

• Provides a precise geometric framework for understanding sacral facet morphology.
• Highlights the biomechanical influences on facet orientation in the spine.
• Identifies lumbosacral transitional vertebrae as a critical factor in spinal instability.