External fixation of proximal humerus fracture. Clinical and cadaver study of pinning technique.

The risk of injuring important anatomic structures or interfering with motion of the glenohumeral joint by transcutaneous pinning of the proximal end of the humerus was investigated in 12 cadaver shoulders and in 23 patients with displaced fractures of the proximal humerus. In the cadavers, pinning of the proximal humeral shaft from laterally more than 20 mm below the surgical neck did not injure the neurovascular structures in any case. Pin insertions into the humeral head medial to the intertubercular groove endangered the cephalic vein and interfered with shoulder function by transfixing the subacromial bursa and by restricting internal rotation. Lateral pinning did not carry such risk. In the patients closed reduction and external fixation confirmed the low risk of neurovascular injuries. Lateral pinning of the humeral head resulted in an unrestricted passive mobility of the glenohumeral joint of the anesthetized patient, whereas anterior pinning carried the risk of mechanical restriction of the internal rotation.