Quantification of 3D Kinematic Measurements for Knee Flexion and Tibial Rotation Using an IMU-Based Sensor and...

Area of Science:

• Biomechanics
• Orthopedic Surgery
• Medical Device Technology

Background:

• Knee rotational stability is critical for anterior cruciate ligament (ACL) procedures.
• Current clinical assessments of knee stability are subjective and lack precision.
• Objective measurement tools are needed for accurate evaluation and rehabilitation.

Purpose of the Study:

• To evaluate the accuracy and repeatability of the GATOR system for measuring knee flexion and rotation.
• To compare the GATOR system's performance against a reference inertial measurement unit (IMU).
• To assess the GATOR system's potential for improving anterior cruciate ligament (ACL) assessment and remote rehabilitation.

Main Methods:

• The GATOR system, integrating ultrasound and IMUs, was tested on six cadaveric knee specimens.
• Specimens were secured in an Oxford Knee Jig for controlled flexion (0-120°) and rotation (internal/external) at various flexion angles.
• Data were analyzed using Bland-Altman plots, root mean square error (RMSE), mean biases, and paired t-tests, comparing GATOR to a reference Xsens DOTS IMU.

Main Results:

• The GATOR system demonstrated good agreement with the reference IMU, with over 60% of trials showing errors < 5° and 80% < 10°.
• Internal rotation measurements showed narrower limits of agreement (biases: 1.91-6.88°) compared to external rotation.
• The system's bone-referenced sensor alignment may reduce soft tissue artifacts, though the ultrasound component's isolated effect was not assessed.

Conclusions:

• The GATOR system shows potential as an accurate and repeatable tool for measuring knee flexion and rotation.
• Its performance suggests it could enhance objective assessments in anterior cruciate ligament (ACL) procedures.
• Optimal sensor placement is recommended for maximizing the system's utility in clinical settings and remote rehabilitation programs.