Motion of the shoulder complex during multiplanar humeral elevation

Abstract

Background: Many prior studies have evaluated shoulder motion, yet no three-dimensional analysis comparing the combined clavicular, scapular, and humeral motion during arm elevation has been done. We aimed to describe and compare dynamic three-dimensional motion of the shoulder complex during raising and lowering the arm across three distinct elevation planes (flexion, scapular plane abduction, and coronal plane abduction).

Methods: Twelve subjects without a shoulder abnormality were enrolled. Transcortical pin placement into the clavicle, scapula, and humerus allowed electromagnetic motion sensors to be rigidly fixed. The subjects completed two repetitions of raising and lowering the arm in flexion, scapular, and abduction planes. Three-dimensional angles were calculated for sternoclavicular, acromioclavicular, scapulothoracic, and glenohumeral joint motions. Joint angles between humeral elevation planes and between raising and lowering of the arm were compared.

Results: General patterns of shoulder motion observed during humeral elevation were clavicular elevation, retraction, and posterior axial rotation; scapular internal rotation, upward rotation, and posterior tilting relative to the clavicle; and glenohumeral elevation and external rotation. Clavicular posterior rotation predominated at the sternoclavicular joint (average, 31 degrees). Scapular posterior tilting predominated at the acromioclavicular joint (average, 19 degrees). Differences between flexion and abduction planes of humerothoracic elevation were largest for the glenohumeral joint plane of elevation (average, 46 degrees).

Conclusions: Overall shoulder motion consists of substantial angular rotations at each of the four shoulder joints, enabling the multiple-joint interaction required to elevate the arm overhead.

Fig. 1

Fluoroscopic view of transcortical clavicular pin placement.

Fig. 2

Subject setup with pins, sensors, and housings and additional surface sensors, including the thorax surface sensor, in place. Note the electromagnetic transmitter placed behind the subject at the level of the acromion and the light fingertip contact on the flat planar surface guiding the motion.

Fig. 3

Motions of the clavicle were defined as protraction-retraction (A) as seen in the superior view of a right shoulder, with the ghosted image representing increased protraction; elevation-depression (B) as seen in the anterior view of a right shoulder, with the ghosted image representing increased elevation; and anterior-posterior rotation (C) as seen in the lateral view of a right shoulder, with the ghosted image representing posterior rotation.

Fig. 4

Motions of the scapula were defined as internal-external rotation (A) as seen in the superior view of a right shoulder, with the ghosted image representing increased internal rotation; upward-downward rotation (B) as seen in the posterior view of a right shoulder, with the ghosted image representing increased upward rotation; anterior-posterior tilting (C) as seen in the lateral view of a right shoulder, with the ghosted image representing posterior tilting; the glenohumeral plane of elevation (D) as seen in the superior view of a right shoulder, with the ghosted images representing anterior and posterior positions relative to the plane of the scapula; and elevation angle (E) as seen in the posterior view of a right shoulder.

Fig. 4

Motions of the scapula were defined as internal-external rotation (A) as seen in the superior view of a right shoulder, with the ghosted image representing increased internal rotation; upward-downward rotation (B) as seen in the posterior view of a right shoulder, with the ghosted image representing increased upward rotation; anterior-posterior tilting (C) as seen in the lateral view of a right shoulder, with the ghosted image representing posterior tilting; the glenohumeral plane of elevation (D) as seen in the superior view of a right shoulder, with the ghosted images representing anterior and posterior positions relative to the plane of the scapula; and elevation angle (E) as seen in the posterior view of a right shoulder.

Fig. 5-A

Figs. 5-A through 5-D The joint motions across planes of elevation during raising of the arm. The values are given as the mean and the standard error. Red = scapular plane abduction (SAB), green = flexion, and blue = abduction. ROM = range of motion. Fig. 5-A Sternoclavicular motion.

Fig. 5-B

Acromioclavicular motion.

Fig. 5-C

Scapulothoracic motion.

Fig. 5-D

Glenohumeral motion.