Documentation of medial rotation accompanying shoulder flexion. A case report

We dissected a fresh cadaver to determine which glenohumeral structures causes medial rotation of the humerus during flexion in the sagittal plane. All structures associated with both shoulders were dissected thoroughly. Both elbows were disarticulated to expose the distal end of each humerus to be used as measurement landmarks. We used a universal goniometer for measurements of shoulder flexion. To determine which structures cause passive medial rotation, the associated shoulder muscles, ligaments, and the capsule were individually reflected from the humerus. Passive shoulder flexion to the point where medial rotation started was measured after each structure was resected. The end passive glenohumeral flexion without rotation was 60 degrees after reflection of all musculature and other periarticular shoulder structures. Our results support Steindler's conclusion that during flexion of the humerus beyond the horizontal there is forced rotation caused by ligamentous tension. We also found that the bony configuration of the glenohumeral joints also plays an important role in medial rotation accompanying shoulder flexion.