Scoliosis in an Orangutan.

STUDY DESIGN: The first case of scoliosis in an Orangutan spine is reported. OBJECTIVES: To study the nature of scoliosis in the spinal specimen, and to determine the etiologic significance to human idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Idiopathic scoliosis has not been observed in primates other than man. Previous studies highlighted the importance of erect posture in the development of idiopathic scoliosis in man. METHODS: A spinal model of an orangutan spine was studied in great detail to determine its nature. The methods used included plain radiographs, computed tomography scans, a three-dimensional plastic model using rapid prototyping, and dissection of the frozen specimen. RESULTS: Features similar to human idiopathic scoliosis were noted including a right-side curve, vertebral rotation to convexity, displacement of the spinal cord to the concavity, and an equal number of ribs on either side. No evidence of congenital anomaly was found. Atypical findings included male gender, a short curve, and kyphosis at the apex. CONCLUSIONS: Although scoliosis found in the orangutan has features similar to idiopathic scoliosis, there also are some dissimilar features, making this diagnosis unlikely. The features observed in this spine suggest that erect posture is important in the morphology of human idiopathic scoliosis.