Exploring age-related differences in asymptomatic male shoulder kinematics using four-dimensional computed tomography

Area of Science:

• Orthopedics and Sports Medicine
• Biomechanics
• Gerontology

Background:

• Age-related shoulder motion differences are crucial for understanding and managing shoulder injuries.
• Previous research on age-related shoulder motion was limited to static, single-plane analyses.
• The shoulder's complex, multi-joint (glenohumeral and scapulothoracic) movement requires dynamic, multi-plane investigation.

Purpose of the Study:

• To quantify age-related differences in glenohumeral and scapulothoracic joint kinematics during motion.
• To assess age-related variations in the neutral positioning of the scapula and humerus.
• To provide insights into the biomechanical factors underlying age-associated shoulder conditions.

Main Methods:

• Thirty-one male participants were divided into two age cohorts (<45 and ≥45 years).
• Four-dimensional computed tomography (4D CT) was used to dynamically track bone motion during forward elevation and internal rotation.
• Six degrees of freedom kinematics were calculated, alongside static neutral joint positioning.

Main Results:

• Older adults showed significantly less relative humeral head translation during motion compared to younger adults.
• Significant differences in scapular positioning (anterior translation, medial rotation) were observed between cohorts during forward elevation.
• Older individuals displayed altered neutral scapular (superior translation, lateral rotation, posterior tilt) and humeral (anterior position) alignments.

Conclusions:

• This study identified significant age-related differences in shoulder kinematics and neutral joint positioning.
• These findings contribute to a better understanding of age-related changes in shoulder subluxation, diseases, and range of motion (ROM).
• The results highlight the importance of considering dynamic, multi-joint movements in age-related shoulder assessments.