Ex Vivo Analysis of Rotational Stiffness of Different Osteosynthesis Techniques in Mouse Femur Fracture

The various molecular mechanisms of cell regeneration and tissue healing can best be studied in mouse models with the availability of a wide range of monoclonal antibodies and gene-targeted animals. The influence of the mechanical stability of individual stabilization techniques on the molecular mechanisms of fracture healing has not been completely elucidated yet. Although during recent years several osteosynthesis techniques have been introduced in mouse fracture models, no comparative study on fracture stabilization is available yet. We therefore analyzed herein in a standardized ex vivo setup the rotational stiffness of seven different osteosynthesis techniques using osteotomized right cadaver femora of CD-1 mice. Uninjured femora without osteotomy served as controls. Femur stabilization with a locking plate or an external fixator resulted in a rotational stiffness almost similar to the intact femur. The use of a "pin-clip" device, a "locking nail," a "mouse nail," or an "intramedullary screw" produced a lower torsional stiffness, which, however, was still significantly higher than that achieved with the widely applied conventional pin. By the use of the presented data a more specific choice of stabilization technique will be possible according to the various questions concerning molecular aspects in fracture healing. (C) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1152-1156, 2009