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The literature is lacking conclusive results regarding the exact mechanism of maximizing the fracture healing stages with minimal traumatic side effects. This observation mandates the development of a novel surgical procedure using small animals as a model to study fracture healing in the presence of osteoinductive agents. Previously, stabilization of osteotomies in small animal models has mainly been accomplished using Kirschner wires, but the rat's tremendous ability to heal an osteotomy stabilized by this method has masked the effects of osteoinductive agents. Thus, this study proposes using a modified 20-hole, 1.5-mm stainless-steel plate to stabilize a 5-mm segmental defect. Thirty of 32 adult male rats were fully weight-bearing within 2 days and were followed over a 15-week period. Two animals showed evidence of fixation failure due to technical error, and the animals were humanely sacrificed. At the end of the study, the fractures were stable with significantly less bone formation evident when compared to controls (p < .001). Therefore, this technique can effectively be used to evaluate compounds that will enhance bone formation and allows for stable fixation of the control with minimal callus formation or bony ingrowth. The goal of this article is to allow other investigators to reproduce this technique as well as outline the advantages and disadvantages of this novel plating technique versus the former Kirschner wire technique for the study of osteoinductive agents using small animals as a model. [ABSTRACT FROM AUTHOR]

Studies have attempted to identify the osteogenic effects of bone morphogenetic proteins using a rat femur model, which commonly involves the creation of a critical size defect followed by internal fixation of the femur. Among the most familiar fixation methods are either plating or intramedullary placement of a Kirschner wire (K-wire). There are advantages and disadvantages to each method; however, this study attempts to identify the best method by exploring the histological effects of each technique. The experiment involved two groups with no added treatment: Group P (plate fixation method) and Group K (K-wire fixation method). The animals were allowed a 4-week interval for the femurs to heal, and proximal, distal, and two midshaft cuts were examined under high-power microscopy after the fixation apparatus was removed. Group K exhibited a peculiar fibrotic healing pattern that followed the shaft of the then vacated K-wire and there was minimal new viable bone formation. Group P, however, exhibited a more natural ingrowth of newly formed bone that began at the proximal and distal cuts and proceeded centrally into the core of the defect. Due to the fibrotic tissue in Group K, this study shows that the model is insufficient due to the micromotion created and thus supports plating of critical defects as the fixation method of choice due to the creation of a stable healing environment. [ABSTRACT FROM AUTHOR]