Palmar/plantar approach for radiographic-guided injection of the equine distal interphalangeal joint collateral ligament insertion.

This study presents a procedure for injecting into the insertion point of a horse’s distal interphalangeal joint (DIPJ) collateral ligament using radiographic guidance, based on tests in 74 horse limbs. The accuracy rate was high and, in the majority of cases, the injection avoided entering the DIPJ itself.

Background

• Limited knowledge and existing techniques surround radiographic-guided injection into the distal interphalangeal joint (DIPJ) collateral ligaments. This research sought to develop and evaluate a new technique involving palmar/plantar radiographic guidance.
• The DIPJ collateral ligaments are important in horses due to their high weight-bearing capacity and frequent injury. Therefore, accurate diagnostic and therapeutic injections are critical in the management of lameness and injury in horses.

Methodology

• The technique was developed using 50 horse limbs (cadavers) and then tested on an additional 24 limbs.
• An 18 G, 9 cm spinal needle was placed in the depression in between the palmar digital neurovascular bundle and the arch of the ungular cartilage. Then, it was advanced towards the distal phalanx collateral fossa.
• Radiographs were used after placement to confirm that the needle was located on the proximal border of the distal phalanx at the collateral fossa.
• Subsequently, dye was injected, hoof walls were partially removed, and collateral ligaments were dissected with needles in place, to identify the dye and needle location.

Findings

• The technique’s accuracy rate was high: correct needle placement was achieved in 85% of the cases (41 out of 48), although successful dye placement into the ligament was slightly lower, at 71% (34 out of 48).
• The injection avoided entering the DIPJ itself for the most part. Dye entered the DIPJ in only 4% of the injections (2 out of 48).
• However, dye entered periligamentous structures in 46% of all injections (22 out of 48).

Implications

• The technique developed and evaluated in this study demonstrated a high accuracy rate with a low injection rate into the DIPJ.
• This suggests that it may be a feasible method for precise therapeutic and diagnostic injections into the DIPJ collateral ligament in living horses, aiding in the management of lameness or injury. However, further research including clinical trials in live horses would be needed to validate its effectiveness and safety.