The correlation between the dose and distribution of intratendinous fluid injections in the flexor tendons/ligaments of the horse.

An in vitro study was carried out to define the correlation between the dose and distribution of intratendinous fluid injections in the different flexor tendons/ligaments of the palmar/plantar, metacarpal/metatarsal region of the horse. Injection of 0.1-0.2 ml resulted in a local intratendinous fluid depot showing minimal abaxial spreading and more extensive proximodistal expansion. If 0.3-0.5 ml was injected the abaxial spreading remained minimal but the proximodistal expansion increased significantly, the depots in the axial proximal, mid and distal region flowing together. Also minimal peritendinous fluid accumulation was visible. Increasing the dose from 0.5 to 2 ml resulted in extensive abaxial spreading and peritendinous accumulation. These findings indicate that the 2 ml injection recommended in the veterinary literature probably represents an oversized dose. If a small lesion is present a 0.1-0.2 ml intratendinous injection should be adequate. The injection should preferably be guided by ultrasonography to allow precise deposition of the drug into the lesion. In larger local defects a depot of 0.3-0.5 ml apparently is sufficient. If a very large portion of the tendon is injured, several depots of 0.3-0.5 ml approximately 5 cm apart is preferred to cover the full proximodistal extension of the lesion.