The monocortical critical size bone defect as an alternative experimental model in testing bone substitute materials

Area of Science:

• Biomaterials Science
• Orthopedic Research
• Regenerative Medicine

Background:

• Standardized animal models are crucial for evaluating bone substitute materials.
• The critical size defect (CSD) model is the established standard for bone regeneration studies.
• Typically, bicortical CSDs are employed, necessitating investigation into alternative models.

Purpose of the Study:

• To assess the suitability of monocortical defects in adult pig calvarias as a critical size defect (CSD) model.
• To evaluate the spontaneous physiological healing process within these monocortical defects.
• To compare the healing and regenerative capacity of monocortical defects filled with autogenous bone versus unfilled defects.

Main Methods:

• Creation of monocortical defects (10 x 10 mm) in adult pig calvarias.
• Group 1: Defects filled with autogenous bone.
• Group 2: Unfilled defects (control).
• Evaluation using microradiography and light microscopy at 2, 4, 12, 26, and 52 weeks.

Main Results:

• Unfilled control defects showed incomplete osseous regeneration at 52 weeks (30% nonmineralized, 55% mineralized, 15% bone marrow).
• Defects treated with autogenous bone demonstrated complete osseous filling by 26 weeks.
• Microradiographic and light microscopic analyses confirmed these findings.

Conclusions:

• Monocortical defects in pig calvarias meet the criteria for a critical size defect (CSD).
• This model offers a simpler, reproducible method for studying bone regeneration.
• The monocortical CSD is suitable for research on bone regeneration and the evaluation of bone substitute materials.