Journal of Orthopaedic Research zyxwvutsrqpo 4:298-303, zyxwvutsrqponml Raven Press, New York zyxwvutsrq 0 1986 Orthopaedic Research Society An Anatomical Comparison of the Human and Bovine Thoracolumbar Spine Paul C. Cotterill, J. P. Kostuik, G. D’Angelo, G. R. Fernie, and B. E. Maki Department of Orthopaedic Surgery, University of Toronto, Orthopaedic Biomechanics Research Lab, Toronto General Hospital, West Park Research, Toronto, Ontario, Canada Summary: The bovine spine has been frequently selected as the model for in vitro mechanical studies. A comparative anatomical study has been presented describing important differences and similarities between selected areas in the adult human and calf thoracolumbar spinal segment. Differences in column length and curvature were observed. The total length of the adult bovine ver- tebral column was found to be on average 209 cm longer than the adult human spine. Equivalent throacolumbar lengths were obtained by selecting 6-8 week-old dairy calves, which because of their young age had the benefit of consistent bone density. The bovine spine was found to have only a single cervical lordotic curve and a single thoracolumbar kyphotic curve (2). A quan- titative comparison of selected dimensions of vertebrae T6, T12, and L3 was performed, and significant findings are discussed. The bovine spinous pro- cesses were found to be on average 11 1% greater in length at level T6, which contributed to a 56% greater total anterior/posterior length at this level in com- parison to the vertebrae of an adult male. A zyxwvu 23% greater bovine intertransverse length at level L3 was also shown. The orientation of the human and bovine superior facets, while being in the same general plane and direction, varied as much as 10.5 and 107% at vertebral level L3 on the two axes measured. These significantly different measurements were considered important factors that can influence experimental results when using the bovine spine as a model. Key Words: Anatomical comparison-Human bovine-Thoracollumbar- Spine. Much of the biomechanical testing of spinal im- plants has used an in vitro model. Calf spines have been used as they are easier to obtain than human spines and can be selected by age to be of compa- rable size. Little has been written however about the similarities between human and bovine spines (6,7). An appreciation of the differences in struc- ture is essential for the correct extrapolation of the results of biomechanical testing to the human situa- tion. Dyce and Wensing (3) reported that the bovine spine has two curves, i.e., a slight cervical lordotic curve in the sagittal plane followed by a gentle ky- photic curve in the thoracolumbar region. In con- trast, the human spine has two additional curves, i.e., lordotic curves in the cervical and lumbar re- gions and kyphotic curves in the thoracic and sacral areas. The thoracic and sacral curves are primary, while the cervical and lumbar curves are sec- ondary, appearing after birth in response to our upright posture (1,2). The total length of the vertebral regions in the calf spine is influenced by the relative shortness of the intervertebral discs, which contribute only 10% Address correspondence and reprint requests to Dr. J. P. Kos- tuik at Eaton North, zyxwvutsr Toronto General Hospital. 200 Elizabeth Of the length Of the in contrast to 25% in Street, Toronto, Ontario M5G 1L7, Canada. man (3). The total length of the adult bovine verte- 298