PURPOSE: Publications describe variable spatial relationships between the axillary artery and brachial plexus whereby the axillary artery may be compressed by the median nerve roots when the upper extremity is hyper-abducted. The purpose of this study is to quantify the frequency of variant positioning of the axillary artery with respect to the brachial plexus, describe and quantify the lengths of the median nerve roots, and evaluate intra-arterial pressure in axillary arteries of normal and variant cadavers when the upper extremity is hyper-abducted. METHODS: Three-hundred and thirty-eight cadaveric axillae were dissected to evaluate the spatial relationship between axillary artery and the median nerve roots. Three-hundred and twelve cadaveric axillae were dissected to evaluate the lengths of the median nerve roots. Twelve cadavers were selected for evaluation of the intra-arterial pressure during a hyper-abduction procedure. RESULTS: The axillary artery was positioned anterior to the median nerve roots in 6.8% of axillae and positioned posterior to the median nerve roots in 93.2% of axillae. An experimental cohort, possessing a classic relationship between axillary artery and median nerve roots and a proximal union of the median nerve roots, showed an increase in intra-arterial pressure during hyper-abduction test. All other experimental cohorts exhibited no change in intra-arterial pressure. CONCLUSIONS: These findings suggest that the median nerve roots are capable of compressing the axillary artery when the upper extremity is hyper-abducted, the axillary artery is positioned posterior to the median nerve roots, and the patient possesses a more proximal convergence of the median nerve roots.
PURPOSE: Publications describe variable spatial relationships between the axillary artery and brachial plexus whereby the axillary artery may be compressed by the median nerve roots when the upper extremity is hyper-abducted. The purpose of this study is to quantify the frequency of variant positioning of the axillary artery with respect to the brachial plexus, describe and quantify the lengths of the median nerve roots, and evaluate intra-arterial pressure in axillary arteries of normal and variant cadavers when the upper extremity is hyper-abducted. METHODS: Three-hundred and thirty-eight cadaveric axillae were dissected to evaluate the spatial relationship between axillary artery and the median nerve roots. Three-hundred and twelve cadaveric axillae were dissected to evaluate the lengths of the median nerve roots. Twelve cadavers were selected for evaluation of the intra-arterial pressure during a hyper-abduction procedure. RESULTS: The axillary artery was positioned anterior to the median nerve roots in 6.8% of axillae and positioned posterior to the median nerve roots in 93.2% of axillae. An experimental cohort, possessing a classic relationship between axillary artery and median nerve roots and a proximal union of the median nerve roots, showed an increase in intra-arterial pressure during hyper-abduction test. All other experimental cohorts exhibited no change in intra-arterial pressure. CONCLUSIONS: These findings suggest that the median nerve roots are capable of compressing the axillary artery when the upper extremity is hyper-abducted, the axillary artery is positioned posterior to the median nerve roots, and the patient possesses a more proximal convergence of the median nerve roots.