[The proximal sesamoid bone of the horse; vascular and neurologic characteristics].

Sesamoiditis is characterized clinically by repeated lameness and radiologically by changes in the proximal sesamoid bones. This thesis, which was defended in June 1997, investigated two characteristics of sesamoiditis, namely the arterial blood supply and the innervation of the proximal sesamoid bones, in order to gain more insight into the etiopathogenesis of sesamoiditis. Experiments with patient material showed that the proximal sesamoid bones have an enormous arterial reserve, due in part to the formation of an arterial shift. Moreover, the sesamoid bones have their own sensory innervation, provided by a branch of the medial and lateral palmar nerve. This branch is called the sesamoid nerve in this article. A special technique was developed to anaesthetize this nerve and can be used for further differentiation of pastern lameness. That the sesamoid bones are sensitive to pain was demonstrated by detection of the so-called nociceptive neuropeptides, substance P and calcitonin gene-related peptide, which are specifically involved in pain sensation. However, the adjacent ligament appear to be even more sensitive. The etiopathogenesis of sesamoiditis is discussed, as are a number of clinical implications of pain in the sesamoid bones. A number of potential future developments are mentioned.