Deltoid Muscle Contribution to Shoulder Function - An Experimental Approach

There is only one study in the literature about the quantitative effect of M. deltoideus on the movement of the shoulder. Here, the author described a 35-80% loss of abduction power after selective blockade of the N. axillaris. Gerber, on the other hand, found a loss of abduction force of 73-86% after blockade of the suprascapular nerve. These results are partly contradictory, which is why the investigators think that further investigation is needed.

For many questions in the field of shoulder orthopedics, this knowledge would provide an important additional basis for therapeutical decision-making. For example, in the treatment of rotator cuff ruptures but also in the implantation of both inverse and anatomical shoulder prostheses. Also, statements about different outcome prognoses could be made more precisely.

Therefore, the investigators would like to perform muscle strength measurements of the deltoid muscle on 12 healthy volunteers on the dominant arm.

Abduction, flexion, external rotation and internal rotation Mm. Infraspinatus, Supraspinatus and Subscapularis are tested respectively.

The investigators plan to carry out the measurements three times before and after an-anaesthesiological nerve block of the axillary nerve thus inactivating the deltoid muscle (performed exclusively by an anesthesiologist specialized in regional anesthesia). The success of the nerve block is confirmed by needle electromyographies (EMG) by a neurologist specialized in electrophysiology. Using EMG neurogenic pathologies within the tested muscles are also ruled out.

In order to exclude relevant rotator cuff pathologies the investigators will perform shoulder radiography in three planes and sonography of the rotator cuff before conducting the experiment described above.