A quantitative method for evaluating inferior glenohumeral joint stiffness using ultrasonography

Area of Science:

• Biomechanics
• Medical Imaging
• Rehabilitation Science

Background:

• Shoulder subluxation in post-stroke patients is linked to nerve issues and muscle fatigue.
• Accurate measurement of inferior glenohumeral joint (GHJ) laxity is crucial for effective treatment.
• Current quantitative methods for GHJ laxity and stiffness evaluation are still developing.

Purpose of the Study:

• To develop a novel ultrasonography protocol for assessing inferior GHJ laxity and stiffness under optimal conditions.
• To investigate the impact of humerus and shoulder braces on GHJ properties.
• To establish reliable testing parameters for GHJ laxity and stiffness measurement.

Main Methods:

• Developed and optimized an ultrasonography protocol using multistage inferior displacement forces on healthy volunteers.
• Defined optimal testing conditions by evaluating different loading mechanisms, shoulder constraining methods, and loading modes.
• Compared GHJ laxity and stiffness between a humerus brace and a shoulder brace using paired t-tests.

Main Results:

• Ultrasonographic laxity measurements with a pulley system were as reliable as direct loading.
• Constraining the unloaded shoulder and loading the upper arm with a flexed elbow demonstrated lower residual variance.
• Humeral braces with belts significantly increased GHJ stiffness compared to shoulder braces without such features.

Conclusions:

• The developed ultrasonography protocol provides a reliable method for measuring GHJ laxity and stiffness.
• Humeral braces may reduce GHJ laxity under external load, potentially preventing subluxation in post-stroke individuals.
• Optimal testing involves constraining the unloaded shoulder, loading the upper arm with a flexed elbow, and using a pulley system.