Effects of experimental desmotomy on material properties and histomorphologic and ultrasonographic features of the accessory ligament of the deep digital flexor tendon in clinically normal horses.

The study investigates the effects of desmotomy on the accessory ligament of the deep digital flexor tendon in horses, uncovering that while scar tissues formed are of inferior quality, most functional properties are restored by an increase in the ligament’s cross-sectional area.

Study Objective and Methodology

• The researchers aimed to assess the biomechanical behavior, along with the histomorphologic and ultrasonographic features of the scar tissue, which forms following a desmotomy of the accessory ligament of the deep digital flexor tendon (AL-DDFT) in horses.
• The study was conducted on five Standardbred trotters. Key factors such as length, cross-sectional area (CSA), in vitro material properties, as well as ultrasonographic and histomorphologic features were examined six months post-desmotomy.
• To assess the changes, surgically treated limbs were compared with the untreated limbs from the same horse, serving as control.

Tensile Tests and Results

• Tensile tests were performed on the ligaments and changes in forces and elongation were recorded for analysis.
• The findings revealed that the CSA of treated ligaments had increased threefold, and they were 1 cm longer than the control ligaments.
• The scar tissue reflected lower stress resistance and material stiffness, as they stood at roughly one-third of the control values.
• However, functional qualities like force and elongation at failure reached around 80% of the values observed in the control set, indicating partial restoration of these properties through an increase in CSA.
• The scar tissue was characterized by high amounts of randomly oriented collagen fibers, as revealed by the ultrasonographic and histomorphologic analysis.

Conclusions

• While the scar tissue from desmotomy was found to be of inferior quality compared to the original tissue, supporting a lower level of stress and stiffness, the CSA increase helped restore most of its functional properties.
• The increased length of the ligament may serve to alleviate strain in the AL-DDFT following desmotomy treatment.
• Given these findings, the study recommends desmotomy as an effective treatment for chronic desmitis in horses.