A physiological dynamic testing machine for the elbow joint

Area of Science:

• Biomechanics
• Orthopedic Surgery
• Biomedical Engineering

Background:

• Developing realistic testing methods is crucial for evaluating orthopedic implants used in elbow joint reconstruction and trauma surgery.
• Existing methods often lack the capacity to replicate physiological movement patterns and force transmission accurately.
• Simulating daily use frequencies is essential for comprehensive implant assessment.

Purpose of the Study:

• To develop an in vitro biomechanical testing setup for assessing elbow implants.
• The setup aims to combine realistic force transmission with physiological movement patterns.
• The frequency of testing mimicked daily use of the elbow.

Main Methods:

• A multidisciplinary approach was used to develop and manufacture an in vitro biomechanical testing machine.
• Pneumatic actuators and an aluminum forearm module facilitated 3 degrees of freedom movement simulation.
• Force and angular sensors replicated in vivo measurements for motion and force analysis.

Main Results:

• 16 human elbow joint specimens were tested at 35 Nm, simulating 5000 cycles from 10° extension to 110° flexion.
• Failure occurred in 9 out of 16 specimens due to transmitted forces.
• Failure rates were significantly higher in female and smaller specimens.

Conclusions:

• A functional testing machine capable of simulating near-physiological repetitive elbow motions was successfully constructed.
• The prototype requires modifications to address identified technical deficiencies.
• Careful selection of cadaver specimens based on implant application is critical for accurate in vitro testing.