In vitro evaluation of a medial approach for intra-articular injection of the tarsometatarsal joints of horses.

To develop a reliable method for injection of the tarsometatarsal (TMT) joint of horses through a medial approach and to characterize anatomy of the synovial recesses of the TMT joint with CT. 13 pairs of fresh cadaveric equine tarsi. TMT joints were assessed with radiography and CT. Twelve pairs of TMT joints were assigned to an experienced veterinarian (8 joints) or veterinary student (16 joints) for injection with contrast medium through a medial or a lateral approach. Every TMT joint was then reexamined radiographically and with CT to assess diffusion of contrast medium. The number of attempts for the lateral and medial approaches between and within investigators was evaluated, which included evaluation of the diffusion of contrast solution in relation to the approach used. All 24 TMT joints were successfully injected, as confirmed with radiography and CT. There was no significant difference in the number of attempts between the medial and lateral approaches and between investigators. No significant difference was detected in the distribution of contrast medium in each synovial recess between the medial and lateral approaches. The medial approach described here for injection of the TMT joint of horses was highly reliable. It involved use of an easily palpable anatomic landmark on the mediodistal aspect of the TMT joint. An established alternative method for injection of the TMT joint may be useful in clinical practice for diagnostic and therapeutic purposes, although a medial approach may increase risk of injury to veterinarians.