A new method to measure post-traumatic joint contractures in the rabbit knee

Area of Science:

• Biomechanics
• Orthopedic research
• Animal models

Background:

• Accurate measurement of joint angles is essential for understanding knee biomechanics and developing treatments for joint contractures.
• Existing methods may lack the precision or multi-degree-of-freedom capabilities required for complex joint motion analysis.

Purpose of the Study:

• To introduce and validate a new device and method for measuring rabbit knee joint angles.
• To assess the device's capability in quantifying joint motion in both normal and pathological (contracture) states.

Main Methods:

• A custom gripping device with femoral and tibial clamps was developed, integrated with a materials testing system and a rotary potentiometer.
• The system captures multiple degrees of freedom, including compression-distraction, internal-external rotation, and coupled translations/rotations.
• Knee joint extension-flexion was measured by combining material testing system displacement and potentiometer readings.

Main Results:

• Normal rabbit knees exhibited minimal changes in extension under cyclic loading (average 1.9 deg).
• The device successfully demonstrated significant loss of knee extension (flexion contracture) in rabbits with surgically induced femoral condyle fractures and immobilization (35 deg vs. 11 deg).
• Internal friction of the device was found to be less than 2% of measured loading.

Conclusions:

• The developed device and method provide a reliable tool for measuring rabbit knee joint angles.
• This system is suitable for characterizing rabbit knee models of post-traumatic joint contractures and advancing orthopedic research.