Reliability and Validity of an Acromion Marker Cluster for Recording Scapula Posture at End Range Clavicle Protraction, Retraction, Elevation, and Depression

Abstract

Acromion marker cluster (AMC) methods have been shown to accurately track scapula motion during humeral elevation below 90°, however, their accuracy has not been assessed in shoulder girdle motion such as clavicle protraction, retraction, elevation, and depression independent of humeral movement. The aim of this study was to examine the reliability and validity of the AMC method to record scapula orientation at end range clavicle protraction, retraction, elevation, and depression. The right scapulae of 22 female and 20 male asymptomatic volunteers were assessed with an AMC and scapula locator (SL) method during end range clavicle protraction, retraction, elevation, and depression (without humeral elevation) using an 8-camera 3D movement registration system. Measurements recorded from the AMC and SL measures showed fair to excellent agreement (ICC 0.4-0.92). While the AMC method overestimated and underestimated scapular motion in some planes compared to the SL, root mean square error between methods were low for scapular internal/external rotation (2.3-3.7°), upward/downward rotation (4.5-6.6°), and anterior/posterior tilt (3.2-5.1°), across all conditions. The AMC method was shown to be a reliable and valid measurement of scapula orientation at end range clavicle movements independent of humeral movement.

Three-dimensional measurements of scapular kinematics: Interrater reliability and validation of a skin marker-based model against an intracortical pin model

“…None of these validated the skin marker model against markers on intracortical pins, however. More recently, a setup similar to the present study compared an AMC model to a scapula locator at end range elevation, depression, protraction and retraction of the clavicle without elevating the arm, reporting mean RMSEs for the scapular rotations of less than 10° [ 40 ].…”

External handheld loads affect scapular elevation and upward rotation during shoulder elevation tasks

“…Both scapulae utilized a three non-collinear acromion marker cluster (AMC) placed on the spine of the scapula as it transitioned into the acromion. Bet-Or et al ( 2017 ) found the AMC method to track scapula kinematics during shoulder elevation has high test–retest reliability (intraclass correlation coefficient = 0.90–0.98) and error of (SEM = max 2.3 deg, MDC = max 6.2 deg) for all 3 scapular rotations. Additional markers were placed on the 7th cervical vertebrae spinous process, 8th thoracic vertebrae spinous process, jugular notch, xiphoid process, a four-marker cluster on each arm midway between the lateral epicondyle and the lateral aspect of the acromion.…”

Comparison of Shoulder Range of Motion Quantified with Mobile Phone Video-Based Skeletal Tracking and 3D Motion Capture—Preliminary Study

“…We estimated the glenohumeral joint location using a functional approach [ 16 , 17 ]. To this end, a temporary cluster was attached to the skin covering the acromion to track the scapula to allow for measurement of relative motion between the upper arm and scapula [ 18 ]. The scapular cluster was placed at the junction of the scapular spine and acromion [ 19 ].…”