Annulus fibrosus micro-damage in Mild intervertebral disc degeneration

Area of Science:

• Biomedical Engineering
• Orthopedics
• Spine Research

Background:

• Intervertebral disc (IVD) degeneration causes biomechanical changes and structural defects, often leading to pain.
• The annulus fibrosus (AF) structure is crucial for IVD function, but its changes during degeneration are not fully understood.

Purpose of the Study:

• To investigate microdamage and mechanical function in the AF of mildly degenerated human IVDs.
• To characterize early structural changes in the annulus fibrosus during intervertebral disc degeneration.

Main Methods:

• Human cadaveric discs (n=18) were analyzed from anterior, posterior, and lateral regions of the inner and outer AF.
• Collagen microdamage was assessed using Collagen Hybridizing Peptide (CHP) and Second Harmonic Generation (SHG) imaging.
• Mechanical testing was performed on the same AF regions.

Main Results:

• No significant differences in mechanical properties were found between degenerative grades.
• Early structural damage, indicated by higher CHP and SHG signal intensity, was observed in the posterior outer AF of Grade 3 discs compared to Grade 2.
• Large variances in mechanical properties were noted, especially in the posterior outer AF.

Conclusions:

• The posterior outer AF is identified as an initial site of structural damage and biological response during IVD degeneration.
• Despite limited mechanical differences, early structural damage in the posterior outer AF suggests its importance in disease progression.
• Targeting the posterior outer AF could lead to early diagnostic and therapeutic interventions for IVD degeneration.