The fetlock tunnel syndrome: a macroscopic and microscopic study.

The research investigates the physical and structural changes occurring in the annular ligaments of horses suffering from Fetlock Tunnel Syndrome (FTS) by comparing it with the ligament structures in healthy horses.

Research and Methodology

• The study examined 49 annular ligaments (AL) from horses without known lameness or digital tendon sheath issues and 30 AL biopsies from horses suffering from FTS. The goal was to determine what changes at a macroscopic and microscopic level result in FTS.
• The macroscopic examination involved observations of the ligament’s looks and thickness.
• The microscopic examination dealt with detailed evaluation of the thickness and architecture of collagen bundles, number and size of blood vessels, and fibroblast nuclear dispersion.

Findings

• Macroscopic observations revealed that healthy annular ligaments typically had a shiny white appearance, while those from FTS afflicted horses were often thicker and less white.
• Microscopic investigations showed that healthy ligaments had parallel, undulating bundles of collagen about 1mm thick, and small blood vessels between 0.03mm to 0.12mm diameter.
• In contrast, FTS-affected ligaments exhibited thicker collagen bundles, a change in the longitudinal direction of collagen bundles, irregularly dispersed fibroblast nuclei, an increase in the number of blood vessels, enlarged diameter of arterioles (up to 0.3mm), and changes in the arterial wall.
• The structural changes in the ligaments in FTS-afflicted horses suggest a possible relationship between these alterations and the causes of FTS.

Implications

• Understanding these physical changes in ligament structure can aid in the diagnosis and treatment of FTS.
• The study opens a pathway to further investigations into the root causes of FTS, possible preventative measures, and more targeted therapies.