Micromotion-based balanced drilling technology to increase near cortical strain.

Area of Science:

• Orthopedic biomechanics
• Surgical implant technology
• Fracture healing research

Background:

• Maintaining balanced micromotion at fracture sites is crucial for optimal bone healing.
• Conventional internal fixation methods may not always achieve the desired balance of cortical micromotion.
• A micromotion-based balanced drilling system using locking plates (LP) and far cortical locking (FCL) was conceptualized.

Purpose of the Study:

• To design and test a novel drilling system aimed at balancing micromotions of the near and far cortices around a fracture.
• To evaluate the system's ability to improve fracture stability and potentially control strain at the fracture site.
• To assess the impact of varying screw configurations and drill parameters on cortical strain.

Main Methods:

• A locking plate (LP) system was used to fix a 2 cm fracture gap in artificial femurs.
• A stepping drill with 3.5 mm and 5.0 mm diameters and standard/eccentric sleeves were employed.
• Fracture models were divided into control (standard holes) and experimental (elliptical holes) groups, with further subgroups based on screw number and placement; axial loads of 500 N or 1000 N were applied.

Main Results:

• The experimental group (elliptical screw holes) demonstrated significantly higher near cortical strains compared to the control group.
• Near cortical strains were significantly higher in configurations with fewer screws (three vs. four) on the proximal segment.
• Adjusting screw number and distribution influenced near cortical strain, with no significant differences observed among groups with four or more screws.

Conclusions:

• The developed drill and sleeve system effectively transforms a standard locking compression plate into a balanced internal fixation system.
• The system improves balanced motion between near and far cortices, enhancing fracture fixation.
• Controlled strain at the fracture site is achievable by modifying drill diameter and sleeve eccentricity.