Regional structure-function relationships of lumbar cartilage endplates

Area of Science:

• Biomedical Engineering
• Orthopedics
• Spine Biomechanics

Background:

• Cartilage endplates (CEPs) are vital for intervertebral disc (IVD) protection.
• The heterogeneous structure-function relationships within CEPs are not well understood.
• Regional variations in CEP properties may influence IVD degeneration.

Purpose of the Study:

• To characterize and correlate regional biphasic mechanical properties and biochemical composition of human lumbar CEPs.
• To investigate the relationship between CEP porosity, s-GAG content, and mechanical behavior.
• To identify regional differences in CEP collagen fiber organization.

Main Methods:

• Mechanical testing of human lumbar CEPs (n=8/region) under confined compression.
• Quantification of swelling pressure, aggregate modulus, and hydraulic permeability.
• Biochemical assays for porosity and s-GAG content; Second Harmonic Generation microscopy for collagen structure.

Main Results:

• Swelling pressure and aggregate modulus were regionally dependent, lowest in the central CEP.
• CEP permeability showed no significant regional dependence.
• Porosity significantly correlated with all measured biphasic mechanical properties and appeared to be the primary indicator.
• Collagen fibers showed regional insertion patterns, perpendicular centrally and oblique peripherally.

Conclusions:

• Human lumbar CEPs exhibit regionally dependent mechanical properties.
• Regional variations in porosity and matrix structure likely drive these mechanical differences.
• This study provides baseline biomechanical data for CEPs, aiding future IVD degeneration research.