3D shoulder kinematics for static vs dynamic and passive vs active testing conditions

Area of Science:

• Biomechanics
• Orthopedics
• Kinesiology

Background:

• Shoulder motion analysis is crucial for establishing normal joint rotation references.
• Current assessments often rely on static positions, contrasting with dynamic clinical practices.
• Testing conditions may alter joint coordination, leading to discrepancies in shoulder orientation data.

Purpose of the Study:

• To investigate the impact of static versus dynamic and passive versus active testing on shoulder joint orientations.
• To quantify differences in shoulder kinematics under various testing modalities.

Main Methods:

• Twenty asymptomatic subjects were instrumented with 45 markers.
• Optoelectronic motion capture tracked upper limb and trunk movement.
• Three-dimensional joint angles of the sternoclavicular, acromioclavicular, scapulothoracic, and glenohumeral joints were calculated using a kinematic model.
• Data were analyzed using four-way repeated measures ANOVA, considering static/dynamic, passive/active, elevation angle, and plane of elevation.

Main Results:

• Scapulothoracic lateral rotation increased more in static (4.2° greater) and passive (6.6° greater) conditions compared to dynamic and active conditions, respectively.
• Glenohumeral elevation increased more in active (4.4° greater) conditions than in passive conditions.
• Significant differences in shoulder joint orientations were observed based on testing conditions.

Conclusions:

• Shoulder joint orientations are demonstrably affected by testing conditions (static vs. dynamic, passive vs. active).
• These findings necessitate careful consideration of testing methodology in shoulder motion analysis for reliable data acquisition and clinical application.
• Discrepancies highlight the importance of standardized protocols for inter-study comparisons and clinical decision-making.