Facet joint changes after chemonucleolysis-induced disc space narrowing.

Area of Science:

• Biomedical research
• Orthopedics
• Cartilage biology

Background:

• Intervertebral disc degeneration is a common cause of low back pain.
• Facet joint osteoarthritis can coexist with disc degeneration.
• The biological relationship between disc height loss and facet joint changes is not fully understood.

Purpose of the Study:

• To investigate the effects of induced disc height loss on facet joint articular cartilage biology.
• To determine the reversibility of facet joint cartilage changes.
• To explore the relationship between disc pathology and adjacent facet joint health.

Main Methods:

• Chymopapain injection was used to induce disc height loss in adult mongrel dogs.
• Facet joints at involved and adjacent levels were analyzed biochemically and histologically at multiple time points (2 weeks to 6 months).
• Radiographic assessments were performed to evaluate joint space narrowing and facet joint overlap.

Main Results:

• Disc height loss was observed, with partial recovery over 6 months.
• Histological analysis revealed Safranin-O stain loss and decreased hexuronic acid content in facet cartilage, with some improvement by 6 months.
• Proteoglycan synthesis was transiently depressed, and changes were noted in adjacent facet joints.

Conclusions:

• A cause-and-effect relationship exists between intervertebral disc pathology and adjacent facet joint biology.
• Facet joint cartilage lesions induced by disc height loss appear potentially reversible.
• Sustained disc height reduction may lead to irreversible osteoarthritic changes in facet joints.