Complete ulnas and fibulas in a pony foal.

Complete ulnas and fibulas were found in a 10-month-old Welsh Pony examined because of severe flexural deformity, with carpal and tarsal valgus deformities, in all limbs. Presence of these normally vestigial structures is considered a form of atavism. At one week of age, periosteal transection was performed for the angular deformity, resulting in no improvement. When performing this procedure, the authors recommend transection of these vestigial structures if present.