Production of a standard closed fracture in laboratory animal bone.

To develop a technique for the production of a standard closed experimental fracture, a new apparatus was designed and tested on 40 male Sprague-Dawley rats. First, the femur was treated with an intramedullary Steinmann pin. The femoral diaphysis was then fractured by means of a blunt guillotine driven by a dropped weight. Radiographically, this technique resulted in a highly reproducible transverse fracture. There was minimal comminution and minimal angulation of the intramedullary pin. Histologically, there was minimal soft tissue damage. Mechanical testing showed that all fractures healed. Pin removal was accomplished with ease and without disturbance of the healed fracture site. The apparatus is simple to use and inexpensive to build. Through its use, a highly reproducible closed fracture model is established.