Case Description—A 5.5-month-old female domestic longhair cat was examined because of dorsal deviation of the caudal aspect of the sternum and progressively worsening dyspnea during play activities.

Clinical Findings—A diagnosis of pectus excavatum was made clinically and confirmed radiographically. The cardiac silhouette was shifted into the right hemithorax. The vertebral index (VI) and frontosagittal index (FSI), which are radiographic indices used to grade the extent of the deformity, were 5.2 and 3.0, respectively. Minimum thoracic height was 13 mm at this time.

Treatment and Outcome—The sternal malposition was corrected during surgery; for stabilization, an internal splint was provided by use of a plate that was applied to the ventral side of the sternum. Radiographic indices improved until day 85; at that time, an increase in the distance between plate and sternum was detected, and plate removal was advised. The radiographic indices improved again after plate removal. At 310 days after surgery, VI was 9.6, FSI was 1.6, and minimum thoracic height was 34 mm. No dyspnea was evident during physical examination.

Clinical Relevance—Results of treatment suggest that this technique may be useful as an alternative surgical option for cats with pectus excavatum that have a noncompliant sternum.