Three-Dimensional Clavicular Motion during Arm Elevation: Reliability and Descriptive Data

Study Design: Cross-sectional. Objectives: To determine the reliability of a surface sensor measurement of clavicular motion during arm elevation and to describe 3-dimensional clavicular motion in an asymptomatic population. Background: Abnormal scapular motion on the thorax has been implicated in shoulder pathology. Without the ability to measure clavicular motion, it is not possible to identify if abnormal scapular motions derive from the sternoclavicular or acromioclavicular joints. Methods and Measures: Thirty-nine subjects participated in the investigation, including an asymptomatic group (n = 30) and a group with a history or current symptoms of shoulder pathology (n = 9). Clavicular angles relative to the thorax were tracked with surface electromagnetic sensors on the thorax, clavicle, and humerus as subjects completed humeral flexion, scapular plane abduction, and abduction. Within-day reliability was assessed using intraclass correlation coefficients and SEM. Descriptive statistics quantified sternoclavicular joint motions for the various arm movements. Results: Reliable measurements were obtained, with intraclass correlation coefficients ranging from 0.93 to 0.99, and SEMs from 0.9° to 1.8°. Between-day reliability SEM values were generally 2° to 4°. During elevation of the arm, the clavicle with respect to the thorax generally undergoes elevation (11°-15° maximum), retraction (15°-29° maximum), and posterior long-axis rotation (15°-31° maximum), with variability between subjects and planes of motion regarding the magnitude of motion. Conclusion: Rehabilitation approaches attempting to improve shoulder motion should benefit from improved knowledge of 3-dimensional contributions of the clavicle to normal and abnormal scapular kinematics.