Measuring Orthopedic Plate Strain to Track Bone Healing Using a Fluidic Sensor Read via Plain Radiography.

Area of Science:

• Biomedical Engineering
• Orthopedics
• Medical Imaging

Background:

• Orthopedic implants, such as fracture plates, are crucial for stabilizing bone fractures.
• Quantifying strain on these plates is essential for monitoring fracture healing and determining safe rehabilitation protocols.
• Current methods for strain measurement can be invasive or lack real-time feedback.

Purpose of the Study:

• To develop and validate a novel fluidic sensor, X-ray visualized strain indicator under applied load (X-VISUAL), for quantifying orthopedic plate strain.
• To assess the sensor's ability to monitor fracture healing progression and inform rehabilitative care.

Main Methods:

• A fluidic sensor utilizing a radio-dense fluid and capillary system was designed.
• The sensor was attached to orthopedic plates on composite tibia mimics and human cadaveric tibias with simulated unstable and healed fractures.
• Cyclic loading was applied, and fluid displacement was measured using plain radiographs to correlate with plate bending strain.

Main Results:

• The X-VISUAL sensor demonstrated reversible and repeatable measurements with high precision (50-80 micrometer fluid level noise).
• The sensor effectively differentiated between unstable and healed fractures, with the healed allograft-repaired fracture exhibiting 13 times greater stiffness.
• The sensor's precision is sufficient (<2% body weight) to track healing from unstable to safe weight-bearing stages.

Conclusions:

• The X-VISUAL fluidic sensor provides a non-invasive method for quantifying orthopedic plate strain.
• This technology enables objective monitoring of fracture healing via standard X-ray imaging.
• The sensor has the potential to significantly improve rehabilitative care by guiding safe weight-bearing decisions.