Objective assessment of shoulder mobility with a new 3D gyroscope--a validation study

Area of Science:

• Biomechanics
• Orthopedics
• Medical Device Technology

Background:

• Objective shoulder mobility assessment is crucial for treatment follow-up.
• Conventional goniometers have high interobserver variability.
• Sophisticated instruments like BIODEX and DynaPort MiniMod TriGyro ShoulderTest-System (DP) offer objective measurements.

Purpose of the Study:

• To validate the DynaPort MiniMod TriGyro ShoulderTest-System (DP) against the established BIODEX system.
• To assess the accuracy and reproducibility of the DP for measuring shoulder mobility.

Main Methods:

• The DP, a 3D gyroscope, was attached to the BIODEX dynamometer's arm for direct comparison.
• Measurements of abduction, flexion, and rotation were taken at various angles (0°-180°), positions, and velocities.
• Accuracy was defined as a difference below 5° between systems; statistical analysis used linear regression.

Main Results:

• The DP demonstrated high accuracy, with a maximum average deviation below 2.1° compared to BIODEX.
• The DP slightly underestimated at small angles but showed increasing positive differences at higher angles.
• Device-related effects caused up to 8° differences between repeated measurements with different DP units at 180°.

Conclusions:

• The DP exhibits high correlation and good reproducibility, with deviations within the 5° tolerance when using a single device.
• A systematic device effect was noted, requiring further investigation.
• Laboratory results are promising for human trials, though challenges remain with shoulder joint center of rotation changes above 90°.