Anatomical differences between dogs and cats

Cats have a supracondylar foramen which is located proximal to the medial epicondyle. The median nerve and brachial artery pass through the supracondylar foramen. Additionally, the medial epicondylar crest is not a flat and even surface as in the dog.

In dogs (A and C), the ideal position for the condylar screw (green) on the medial side is cranial and distal to the palpable landmarks of the epicondyle (blue). On the lateral side the entry hole lies within the extensor fossa.

In cats (B and D), the ideal position for the condylar screw (green) on the medial side is cranial and distal to the palpable landmarks of the epicondyle (blue). On the lateral side the entry hole lies on the edge of the extensor fossa. The risk of inadvertent joint penetration on the caudal aspect of the humerus can be minimized by drilling the hole from a slightly proximolateral to distomedial direction.

For fractures in dogs where the plate should reach far distal, a medial plate application is favored since the straight medial epicondylar crest allows fixation with very little contouring of the plate.

In cats, plate application on the distal humerus is more challenging and requires more plate contouring due to the supracondylar foramen (including the brachial artery and the median nerve) and the small and uneven epicondylar crest.

In some cases, the nerve must be freed from the supracondylar foramen to avoid nerve impingement under the plate. Therefore, plate positioning is more challenging, and lateral plate placement should be favored.