The shoulder : rupture of the supraspinatus tendon and other lesions in or about the subacromial bursa / E.A. Codman.

  • Codman, E. A. (Ernest Amory), 1869-1940.
Date:
1934
Catalogue details

Licence: In copyright

Credit: The shoulder : rupture of the supraspinatus tendon and other lesions in or about the subacromial bursa / E.A. Codman. Source: Wellcome Collection.

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    higher by bundling than by elevating the arm. Rotation of the clavicle, slight as it is, tends to throw the glenoid forward and face it more directly upward. Consider that the clavicle is a rod fastened near its end to the coracoid and acromion which join together firmly at the glenoid. Forget the rest of the scapula. Twist the clavicle, which is about T1/^ inches long, a few degrees on its long axis, and the glenoid, which is offset two inches, will move a good deal even assuming no acromio-clavicular motion. As the arm is elevated it is very easy to feel on your own shoulder that the scapula not only rises but rotates on the chest wall. The lower angle which is easily palpated may travel an arc of over 45 degrees on the circumference of the chest. Part of this motion is made possible at the acromio-clavicular joint, but most of it is due to rotation of the clavicle at the sterno-clavicular joint. To sum up, we may say that during the motion of elevation the humerus is rotating on its own vertical axis, pivoting on a fulcrum which is rotating and passing forward in relation to a center which is rising, moving backward and slowly rotating on a left turn. Taking all these facts into consideration, it is quite possible that by astronomic calculation from motion-picture X-ray films of a liv¬ ing skeleton, the “relativity” of these compound motions might be made out. But when this has been done, calculations for the motions of the spinal column must be added, for in life it is scarcely possible to move the shoulder without compensatory curving or twisting of our spines. This is particularly true in patients with sore shoulders. Lateral elevation of the humerus in the coronal plane cannot be accomplished as far as a right angle with the axis of the body, if the arm is first put in internal rotation (i.e., arms akimbo). How¬ ever, if it starts in the anatomic position it may be raised to the hori¬ zontal or perhaps a little higher without any external rotation. This includes motion of the scapula on the chest wall through motion at the acromio-clavicular joint and at the sterno-clavicular joint. Only a part of this 90 degrees is performed by the shoulder joint, per¬ haps less than a half. Full lateral motion or elevation in the coronal plane can only be accomplished in external rotation. In internal rotation, the tuberosity meets the acromion, but as the arm is ex¬ ternally rotated, the shape of the head and neck under the acromion changes, and the head rolls in under the acromion by a very narrow margin at just about the region of the bicipital groove. At the same time the scapula tilts so that the glenoid turns upward. However, elevation in the sagittal plane can be accomplished in internal rotation.