Posterolateral intertransverse lumbar fusion in a mouse model: surgical anatomy and operative technique.

BACKGROUND CONTEXT: Animal models are frequently used for studying the effect of bone graft substitutes or allogeneic materials on osterolateral lumbar fusion. Transgenic technology in the mouse provides a unique opportunity to further understand the biology of spine fusion. PURPOSE: To describe pertinent lumbar spine anatomy and formulate a surgical protocol for posterolateral fusion in the mouse model. STUDY DESIGN: Diagnostic model: development of an animal model for biologic evaluation of posterolateral spine fusion. METHOD: Ten mice were killed to study relevant lumbar spine anatomy and develop a protocol for lumbar spine fusion. The L4-L6 fusion protocol was validated in 46 mice for ease of exposure, preparation of the posterolateral fusion bed, introduction of bone inductive agents, and perioperative care. RESULTS: Anatomy and surgical technique for posterolateral intertransverse lumbar fusion in the mouse model are described. A paraspinal approach allows exposure of the transverse processes, decortication, and graft placement at the L4-L6 intertransverse fusion site. Decortication alone did not result in fusion, whereas the use of bone graft resulted in satisfactory fusion rates. Perioperative morbidity and mortality rates were low. CONCLUSION: The mouse posterolateral lumbar spine fusion model is reproducible, inexpensive, and has low complication rates. Knowledge of the relevant anatomy and adherence to a well-defined surgical protocol provides a reliable and reproducible experimental spine fusion model.