Creating a Box-Cavity Defect Model in the Cortical Bone of Rat Femora

Various animal models with bone defects are applied in exploring the therapeutic potential of tissue engineering for bone healing. However, most of them are unable to generate standard defects under biomechanical loading conditions, which is important in evaluating the bone healing effect of bowel materials. Compared to traditional bone defect models, the recent box cavity cortical bone defect model offers significant advancements.

It not only provides a standardized bone defect site for more accurate quantification of bone healing, but also allows for the assessment of bio materials under biomechanical loading conditions without the need for additional fixation. Our protocol provides a comprehensive and generalizable approach for investigating inter member bone formation within in vivo study of bone regeneration models. This is particularly beneficial for the field of bone tissue engineering.

To begin, place the anesthetized rat in a lateral recumbency position on the sterile surgical table. Remove the lower limb hairs with an electric shaver. Disinfect the surgical area in a circular motion with 5%iota four solution, followed by 75%alcohol.

After locating the proximal and distal femur, make a 2.5 centimeter incision along the long axis of the femur to cut through the skin tissue. Using ophthalmic forceps and tissue scissors separate the skin layer from the fascia. Expose the lateral approach to the femur through the biceps femoris and lateral femoral muscles.

Locate the intersection of the two muscle septa and carefully separate with a disposable surgical blade along the muscle border until the femoral surface is reached. Next, apply a periosteal separator to bluntly separate the femoral surface muscles and expose the middle of the femoral diaphysis. Using a sterile marker pen mark the area of the defect site on the mid surface of the femoral diaphysis.

Next, using an oral low speed handpiece drill a small hole perpendicular to the bone surface at the marked site, destroying the periosteum and bone cortex to a depth reaching the bone marrow cavity. Expand the hole in all directions to achieve a box cavity shape. Now, hold a labeled oral probe parallel to the edge of the defect to determine the defect diameter and morphology.

Suture to close the muscle and skin layers. Finally, disinfect the surgical area with 5%iota four from the inside out.