American Board of Surgical Assistants (ABSA) Orthopedic Practice Test

Which property of cancellous bone makes it less favorable for fixation compared to cortical bone?

1. Higher porosity

2. Lower strength

3. Higher elasticity

4. Lower blood supply

The correct answer is: Lower strength

The property of cancellous bone that makes it less favorable for fixation compared to cortical bone is its lower strength. Cancellous bone, also known as trabecular or spongy bone, is characterized by its porous structure, which provides it with a lightweight design. This structure allows for good shock absorption and provides structural support where it is most needed in the body. However, this increased porosity and the associated reduction in density lead to lower mechanical strength compared to cortical bone. While cortical bone is dense and provides stability and strength to resist the high loads imposed on it, cancellous bone's lower strength limits its ability to effectively hold fixation devices like plates, screws, or intramedullary nails. The implications of this lower strength are crucial in orthopedic applications, as devices must secure bone fragments together in a stable manner until healing occurs. The fixation in cancellous bone may not withstand the same loads that cortical bone can, making the choice of fixation strategies and implant designs critical in areas where cancellous bone is predominant.