Injection of the insertion of the collateral ligament of the distal interphalangeal joint in standing horses using the palmar radiographic-guided approach

Injury to the collateral ligament (CL) of the distal interphalangeal joint (DIPJ) is recognized as a source of lameness in horses. Intralesional injection has been advocated to increase return to performance. This study was a proof-of-concept study in standing horses to evaluate success of a palmar radiographic-guided approach for injecting insertions of the DIPJ CLs previously described in cadaver limbs. Horses were sedated, nerve blocked, and placed on wooden blocks with the limb to be injected staggered approximately 20cm cranially to the other limb. The DIPJ CL insertion was injected, using the palmar radiographic-guided technique, with 0.5 ml of new methylene blue (NMB) dye using an 18g, 9cm spinal needle. The lateral or medial CL was randomly assigned to one forelimb for injection. Lateromedial and dorsopalmar radiographs were taken to confirm correct location of the needle. Following injection, needles were removed, and horses were euthanized. Two hours after euthanasia, the metacarpophalangeal joint was disarticulated, and the hoof wall was removed. The DIPJ, injected CL, and periligamentous structures (PLS) were assessed for presence of NMB dye. A total of 20 CLs, 10 medial and 10 lateral, were injected. Overall, 19/20 (95%) had dye in CL insertions; 4/20 (20%) had dye only in CL insertion, 6/20 (30%) had dye in CL insertion and DIPJ, and 9/20 (45%) had dye in CL insertion and PLS; 1/20 (5%) had dye only in PLS. A palmar radiographic-guided approach using a staggered stance is a reliable, repeatable way to inject DIPJ CL insertions in sedated horses.