Experimental Model of Posterolateral Spinal Arthrodesis in Sheep

OBJECTIVES: The authors evaluated the reliability in obtaining a posterolateral spinal arthrodesis (PSA) with autologous bone graft. SUMMARY OF BACKGROUND DATA: Posterolateral spinal arthrodesis using autogenous cancellous bone graft is the most simple and efficient technique to get a spinal graft. No extensive biomechanical study of PSA is available. Thus, an experimental model of PSA is needed. METHODS: Eleven sheep underwent lumbar autologous bone grafts and Cotrel-Dubousset instrumentations, and four sheep were used as controls. Sacrifice and biomechanical evaluation of the lumbar spines were performed after 1 year. RESULTS: All grafts appeared continuous. A large decrease of flexibility (in rotation and in translation) was found in grafted spines in every direction. Failure in extension occurred at a mean value of 35.26 +/- 3.71 Nm. CONCLUSION: A constant and homogenous PSA appears to be obtained in sheep under conditions close to the human surgery.