Pathogenesis of canine aural hematomas.

Morphologic examination of 3 ears from 2 dogs with aural hematomas revealed that the hematomas had developed within the pinnal cartilage. The cartilage had fractured from perichondrium to perichondrium and in some areas clefts had formed within the cartilage. Cartilage fracture could have resulted from wave motions set up in the pinna during head shaking. An explosive burst of head shaking exceeding a critical head velocity or a more gentle but sustained head shaking establishing a sinusoidal wave motion within the ear could have caused cartilage fracture.