Feasibility for Ultrasound-Guided Injection of the Collateral Ligaments of the Distal Interphalangeal Joint in Horses.

This research investigated the success of ultrasound-guided injections in the collateral ligaments of a horse’s distal interphalangeal joint using cadaver limbs. While the ligament was successfully injected in 97.4% of cases, complete coverage was less frequent and other surrounding structures were also injected unintentionally.

Objective and Method

• The research team carried out a study to assess the feasibility of using ultrasound-guided injections to target the collateral ligaments of the distal interphalangeal joint in horses.
• This comes in response to cases of desmitis (inflammation of the ligaments) causing lameness in performance horses, for which such injections could be a treatment.
• 76 cadaver horse limbs were subjected to this method, each injected with dye to clarify the injection’s path and destination.
• To quantify successes and potential errors, the hooves were later cross-sectioned to check the dye’s location compared to the target ligaments and any other structures.

Findings

• The collateral ligament was reached by the injection in a large majority of cases (97.4%).
• However, the entire length of the ligament was less consistently covered—only in about 43.2% of trials was the dye confirmed to have permeated all areas of the ligament.
• In other cases, either two areas (45.9%) or just one area (10.8%) of the ligament was affected.

Inadvertent Effects

• The results were occasionally off-target, which could potentially result in unintentional interactions with other elements of the equine foot:
• The distal interphalangeal joint was also injected in 81.6% of cases and the common digital extensor tendon in 43.4% of cases.

Significance and Interpretation

• The findings indicate that using ultrasound can help guide injections to this specific ligament but does not ensure that the injection won’t inadvertently affect other structures within the foot.
• The positive predictive value (likelihood the injection hits the ligament when ultrasound indicates so) is high at 98%, yet the negative predictive value (likelihood the injection misses the ligament when ultrasound indicates it would) is very low at 9%.
• This suggests further research and refinement of the method are necessary to increase its reliability.