Comparison of autogenous cancellous bone grafts obtained from the sternum and proximal portion of the tibia of llamas

Objective-To describe the anatomy of the sternum in Ilamas, define the surg ical approach to the sternum for collection of cancellous bone graft tissue , and compare the histologic appearance of graft tissue obtained from the s ternum with that obtained from the proximal portion of the tibia. Design-Prospective study. Animals-12 Ilamas, 3 to 19 years old, that had been submitted for necropsy. Procedure-Radiographs were taken of the sternum and left tibia of the Ilama s. Measurements of the sternum were determined from the radiographs and adj usted for magnification. Sternebrae volumes were estimated from these measu rements. Anatomic dissections to the center of the fourth sternebra and the proximal portion of the tibia were made, and a surgical approach to the st ernum was developed. Cancellous graft tissue was obtained from each site an d submitted for histologic evaluation. Results-Sternebrae 3, 4, and 5 were significantly larger in volume than the other sternebrae. The ventral aspect of the fourth sternebra was readily a ccessed for removal of graft tissue by making a 6-cm-long ventral midline i ncision centered 17 cm craniad to the xiphoid. Mean soft tissue thickness o verlying the ventral aspect of the fourth sternebra was 3.1 cm. More tissue was obtained from the sternal (mean, 9.11 g) than from the tibial (mean, 5 .16 g) sites. Sternal graft tissue consisted of trabecular bone spicules wi th predominantly hematopoietic marrow, whereas tibial tissue consisted of t rabecular bone spicules with only fatty marrow. Conclusions and Clinical Relevance-The fourth sternebra in Ilamas is readil y accessible for obtaining autogenous cancellous bone graft tissue that con sists of predominantly hematopoietic marrow.