Percutaneous pinning of the proximal part of the humerus. An anatomic study

Closed reduction and percutaneous pinning of unstable proximal humeral fractures is a well-described technique with some theoretical advantages over open techniques. To our knowledge, the risk of injury to neurovascular structures from percutaneous pinning of the proximal part of the humerus has not been studied. We sought to quantify this risk using a cadaveric model.

In ten fresh-frozen cadaveric shoulders, the intact proximal part of the humerus was pinned under fluoroscopic guidance with use of an identical published technique. A total of five 2.5-mm terminally threaded AO pins, including two lateral, one anterior, and two greater tuberosity pins, were used in each shoulder. The specimens were then dissected to determine the distance of each pin from adjacent neurovascular structures as well as key anatomic relationships.

The proximal lateral pins were located at a mean distance of 3 mm from the anterior branch of the axillary nerve. Four of the twenty lateral pins were noted to penetrate the articular cartilage of the humeral head. The anterior pins were located at a mean distance of 2 mm from the tendon of the long head of the biceps (perforating the tendon in three specimens) and of 11 mm from the cephalic vein (perforating the vein in one specimen). The proximal tuberosity pins were located at a mean distance of 6 and 7 mm from the axillary nerve and the posterior humeral circumflex artery (tenting the structures in two specimens with internal rotation), respectively. These pins moved away from the nerve with external rotation of the humerus.

The technique used in this study may be associated with a risk of injury to important anatomic structures about the shoulder. Lateral pins should be distal enough to avoid injury to the anterior branch of the axillary nerve, and multiple fluoroscopic views should be obtained to avoid penetration of the humeral head cartilage. There may be a risk of injury to the cephalic vein, the biceps tendon, and the musculocutaneous nerve with use of anterior pins, and these pins should be employed with caution. Greater tuberosity pins should be placed with the arm in external rotation, should be aimed for a point 20 mm from the inferior aspect of the humeral head, and should not overpenetrate the cortex.