Orthopedic Lag Screws: Biomechanics, Principles, and FRCS Exam Prep MCQs

Key Takeaway

A lag screw's primary biomechanical function is to create interfragmentary compression across a fracture. It achieves this by engaging only the far cortex, while gliding freely through the near cortex. This differential engagement pulls bone fragments together, providing absolute stability crucial for optimal fracture healing, particularly in oblique or spiral fractures.