A comparative study of structures comprising the thoracic outlet in 250 human cadavers and 72 surgical cases of thoracic outlet syndrome.

Objective: We have hypothesized that variations in fibrous, muscular and osseous structures with the potential to entrap the brachial plexus occur within the thoracic outlet of the normal population; and that these variations are different in pattern and frequency from those in patients presenting with thoracic outlet syndrome (TOS). Methods: Structural anomalies with potential for entrapping elements of the brachial plexus were examined following dissections of the posterior triangle of the neck in 250 human cadavers (N = 500 thoracic outlet dissections) and catalogued jointly by an anatomist and a thoracic surgeon. The pattern and frequency of anomalies in the 250 cadavers was compared to that encountered in 72 surgical cases of removal of the first rib for relief of symptomatic TOS (N = 72 procedures; 55 patients). Results: Relevant structural variations were encountered in 46% of cadavers, exhibiting no left-right or gender preference overall. When compared with the surgical group in which 100%, exhibited structurally relevant anomalies, significant differences in pattern of anomalous structures and gender distribution were revealed. Anomalies posterior to the brachial plexus, ranging from fibrous bands to cervical ribs in both groups, were prevalent in the surgical group. A 'scissors-like' pattern, with neural entrapment by anterior and posterior anomalies was frequently encountered in females. Conclusions: Based on these data and embryological considerations, we propose a revised and simplified classification of impingement mechanisms within the anatomic thoracic outlet. Comparing these data to radiological imaging and observations at surgery, we offer a new perspective for the investigation and management of patients with TOS. (C) 1998 Elsevier Science B.V. All rights reserved.