Generation of closed transverse fractures in small animals

Abstract

The most common procedure that has been developed for use in rats and mice to model fracture healing is described. The nature of the regenerative processes that may be assessed and the types of research questions that may be addressed with this model are briefly outlined. The detailed surgical protocol to generate closed simple transverse fractures is presented, and general considerations when setting up an experiment using this model are described.

Figure 1

Radiographic Examples of Closed Simple Transverse Fracture Model A) Examples of the Rod Placement and Fracture of mouse femur (upper) and mouse tibia (lower) panels. Images were generated using dental x-ray device. B) Three examples of fractures that would be excluded from study. The exclusion criteria are denoted in the figure with the arrow indicating the position of the fracture on the radiograph. Images were generated using a Faxitron® device.

Figure 2

Materials for carrying out closed fracture procedure A) The instruments and materials that are needed for carrying out the surgical procedure in either rats or mice. B) Fracture devise for the generation of closed transverse fractures by controlled blunt trauma and three point bending. 1) Devise as generated from the schematic drawings courtesy of Dr. Kristen Billiar, and as described in Marturano et al., 2008 (9). 2) Drop weight and electromagnet striker release assembly. 3) Calibration scale to adjust distance of drop. 4) Blunt striking blade and anvil for positioning of femur and generation of three point bending. C) Three types of fixation pins used to stabilize closed fractures in rats and mice.

Figure 3

The surgical steps of the closed fracture procedure 1) Manual palpitation and positioning to localize line for incision over the central patellar groove. 2) Exposure of the center of the groove on the femoral and tibia condyle for pin insertion. 3) Lateral subluxation of the patella and extensor mechanism. 4) Creation of the entry hole for pin insertion. 5) Pin insertion. 6) Position of the femur for fracture. 7) Positioning of the mouse for postoperative x-ray and immediate postoperative x-ray assessment showing a successful mid-diaphyseal fracture.