Posterior to anterior transglenoid pins: anatomy at risk.

Pneumothorax was noted after an arthroscopic procedure during which a small guidewire overpenetrated the glenoid from a posterior-superior direction. This anatomic study was undertaken to determine the structures at risk from pins overpenetrating from the posterior-superior aspect and to determine whether scapulothoracic position altered the risk. The glenoid was intentionally overpenetrated with wooden dowels from the posterior-superior aspect of the glenoid in seven fresh cadaveric shoulders. The dowels were placed arthroscopically using the Suretac instrumentation (Acufex Microsurgical, Mansfield, MA). The specimens were planed, and the relationship of these wooden pins to vital structures was evaluated. In all specimens, the dowels entered the thoracic cavity between the first and second ribs, regardless of scapular position. The pins consistently passed posterior to the neurovascular bundle but were precariously close, with an average distance to the closest neurovascular structure of 7.4 mm (range, 1 to 19 mm). Scapular position did not seem to affect this relationship.