Objective: To identify the most common sites of and possible predisposing factors for nonunions in cats with fractures of the appendicular skeleton.
Design: Retrospective study.
Animals: 344 cats treated for fractures between 1998 and 2002, 18 of which developed nonunions.
Procedures: Information collected from the medical records included signalment; type of trauma; fracture location, orientation, and type; degrees of displacement and comminution; treatment; and outcome.
Results: The tibia and proximal portion of the ulna were identified as the most common sites for nonunions. Factors significantly associated with development of a nonunion included age, body weight, affected bone, fracture type, degree of comminution, and fixation type, with older cats, heavier cats, cats with fractures of the tibia or proximal portion of the ulna, cats with open fractures, cats with comminuted fractures, and cats with fractures stabilized with a type II external skeletal fixator being significantly more likely to develop a nonunion. Eleven of the 18 cats with nonunions had a successful outcome following treatment of the nonunion.
Conclusions and clinical relevance: Results suggest that in cats, fractures involving the tibia and proximal portion of the ulna are more likely to develop nonunions than are fractures involving other sites but that many factors may increase the risk of nonunion. Use of excessively large and rigid type II external skeletal fixators may be associated with development of nonunions; however, type II external skeletal fixators were commonly used to stabilize fractures in sites predisposed to nonunion.