Morphometric analyses of the body and the branches of the normal third interosseous muscle (suspensory ligament) in Standardbreds.

This study analyzes the composition of a ligament (third interosseous muscle) in horses and finds significant variations in connective tissue, muscle tissue and adipose tissue proportions in relation to age, sex and limb types.

Objective and Methodology of the Study

• The primary aim of this study was to measure the composition of different tissues – connective tissue (CT), muscle tissue (MT) and adipose tissue (AT) – in the third interosseous muscle (TIOM), also known as the suspensory ligament, in healthy horses.
• The researchers investigated whether there were any variations related to age, sex, type of limb (thoracic and pelvic), and different segments within the ligament itself.
• The methodology of the study involved collecting samples from right limbs of 11 sound (healthy) horses. The samples were sourced from 6 different levels within the TIOM.
• These samples were then processed using paraffin or Tissue-Tek(®) embedment. Several tissue staining methods using Hematoxylin, Phloxine, and Saffron were employed to facilitate accurate image analysis.

Key Findings of the Study

• The results showed significant variations in the composition of the TIOM. The percentages of muscle and adipose tissues decreased significantly with age and when moving from proximal (closer to the body) to distal (further from the body) segments of the ligament. At the same time, the percentage of connective tissue increased significantly.
• Gender-specific differences also emerged. Female horses had a significantly higher percentage of muscle tissue compared to males. Conversely, male horses had significantly more connective tissue compared to females.
• Furthermore, it was found that the percentage of adipose tissue was significantly higher in the pelvic limbs than in the thoracic limbs of the horses.

Implications of the Findings

• The findings of this study provide new insights into the morphometry or shape characteristics of the third interosseous muscle (TIOM) in healthy horses.
• This deeper understanding of tissue variation in the TIOM based on different factors such as age, sex, and limb type, may potentially influence care and treatment strategies for horses, particularly in addressing conditions and injuries associated with this ligament.