Tenosynovitis of the digital flexor tendon sheath and annular ligament constriction syndrome caused by longitudinal tears in the deep digital flexor tendon: a clinical and surgical report of 17 cases in warmblood horses.

This study examines the occurrence of longitudinal tears in the digital flexor tendons of horses as a potential cause of chronic inflammation and annular ligament constriction syndrome. The research contends that this condition often does not respond to traditional treatment methods but can be diagnosed using unique surgical techniques.

Research Objectives and Methodology

• The researchers intended to assess the frequency of longitudinal tears as a possible reason for chronic inflammation in the digital flexor tendon sheaths and annular ligament constriction syndrome in warmblood horses.
• This study reviewed the records of 25 horses with these chronic conditions, in which a tenoscopical inspection of the digital flexor tendon sheath was conducted between 1999 and 2000. Of these 25 horses, 17 were diagnosed with a longitudinal tear in the deep digital flexor tendon.
• All the horses in the study had a history of distension of the digital flexor tendon sheaths or signs of annular ligament constriction syndrome. A significant number of them showed signs of an inflamed digital flexor tendon sheath by ultrasonography.
• Longitudinal tears of the deep digital flexor tendon were verified in all cases via tenoscopy. The surgical treatment involved removing the torn collagen fibrils with a mechanical resector and decompressing the fetlock canal via transecting the palmar annular ligament using a hook knife under tenoscopic control.

Findings and Conclusions

• The outcomes of the treatment varied; ten horses became sound and returned to their previous level of work, three stayed lame, whilst four returned to their prior level of work but required intrasynovial treatment and less frequent competition to stay sound.
• The horses that presented with chronically inflamed digital flexor tendon sheaths or annular ligament constriction syndrome may have been suffering from longitudinal tears in the deep digital flexor tendon. However, an accurate diagnosis could not be made using ultrasonography alone.
• The study concluded that an inspection of the tendon sheath using tenoscopy is essential to make an accurate diagnosis and to provide effective treatment. This could explain why some cases of chronic inflammation of the digital flexor tendon sheath and/or annular ligament constriction syndrome do not respond to the surgical transection of the palmar annular ligament alone without using tenoscopy.