A histological study of macroscopically normal equine digital flexor tendons

Area of Science:

• Veterinary Anatomy
• Histology
• Equine Tendon Biology

Background:

• Superficial (SFT) and deep (DFT) digital flexor tendons exhibit distinct histological structures.
• Variations in histology exist between different anatomical locations within the same tendon and between fore and hind limbs.
• Age-related changes affect both SFTs and DFTs, with various alterations observed.

Purpose of the Study:

• To describe the normal histological appearance of SFTs and DFTs.
• To identify age-related histological changes in these tendons.
• To investigate a specific histological change associated with common SFT injury sites.

Main Methods:

• Histological examination of SFT and DFT samples.
• Comparative analysis of tendon structures from different sites and limbs.
• Observation of age-related changes and injury-associated alterations.

Main Results:

• Distinct histological differences were identified between SFTs and DFTs.
• Histological variations were noted across different tendon regions and limb types.
• A patchy loss of stainable nuclei was observed at common SFT injury sites, a change previously termed tendon necrosis.
• Age-related histological alterations were documented in both tendon types.

Conclusions:

• The study highlights significant histological variability in digital flexor tendons.
• A specific finding of nuclear loss in SFTs warrants further investigation regarding its etiological role in clinical lesions and potential impact on mechanical tendon strength.
• The cause and effect relationship between observed acellularity and clinical tendon injuries remains unproven.