Sesamoid bone of tendon of supinator muscle
Os sesamoideum tendinis musculi supinatoris
Definition
The sesamoid bone of tendon of supinator muscle is found in the tendon of origin of this muscle, at the level of the elbow. In the dogs, the supinator muscle originates from the lateral epicondyle of the humerus, by means of a thick tendon. This tendon passes distally to the cranio-lateral aspect of the head of the radius. At this level, an oval-shaped sesamoid bone may develop inside the tendon of the supinator muscle, which articulates with the head of the radius.
In a study of 100 dogs, sesamoid bone of tendon of supinator muscle was visible on CT scan in 26% of cases and bilateral in 76.92% of cases. It was found radiographically in 8.33% of cases. It is important to recognise the presence of the sesamoid bone of tendon of supinator muscle so as not to confuse it with a fragmentation of the head of the radius, for example. A positive correlation has been suggested between elbow disease (dysplasia in particular) and the presence of the sesamoid bone of the supinator tendon.
Variation:
In cats, a sesamoid bone is rarely present in the tendon of origin of the supinator muscle; when present, it appears as a small mineralized opacity on the craniolateral aspect of the radial head.
References
Vali Y et al. Radiographic and computed tomographic evaluation of supinator sesamoid bones in dogs. BMC Veterinary Research 2022;18:377.
Thrall DE, Robertson ID. Atlas of normal radiographic anatomy and anatomic variants in the dog and cat. St. Louis (MO): Elsevier; 2023. p. 91.
