Surgical anatomy of the proximal humerus for minimally invasive osteosynthesis. Cadaveric study

Abstract

In proximal humerus fractures, the minimally invasive technique with plate osteosynthesis (MIPO) uses an anterolateral approach between the anterior and middle portions of the deltoid muscle. At this level there are nervous elements, axillary or circumflex and musculocutaneous and vascular elements, vital to preserve the humeral head, the ascending branch of the posterior circumflex humeral artery (ACHP) and, to a lesser extent, the ascending branch of the anterior circumflex humeral artery (ACHA). The greatest risk to the axillary nerve occurs during the initial dissection after the two heads of the deltoid muscle have been divided. Objective: to describe the location and reference points of these vascular and nervous elements of the proximal humerus in relation to minimally invasive osteosynthesis, to avoid complications.

A classical dissection of 4 adult cadavers, 3 female and 1 male, was performed from the normal anatomy chair, using a deltopectoral approach, identifying nervous elements, axillary nerve, musculocutaneous and vascular elements, ACHP and ACHA measured in relation to the MIPO technique.

The axillary nerve was found at an average distance in the 4 cadavers of 6.5 cm distal to the acromion with the arm in neutral position and 4.6 cm distal to the acromion with 90° abduction. The ACHP emerged from the axillary artery, on the lower border of the subscapularis and then was located with the axillary nerve through the quadrangular space in all cases. The ACHA branched from the axillary artery, on the lower border of the subscapularis and continued its horizontal course behind the coracobrachialis muscle to the bicipital notch, in all cases, an average of 5.2 cm below the lower border of the acromion. The ascending branch (arcuate artery) of ACHA ascended on the lateral border of the bicipital groove and entered the proximal humerus at the level of the greater tuberosity in all cases. We highlighted a hypovascular “bare spot” with an average width of 2.7 mm, located in the greater tuberosity between the two penetrating vessels of the humeral head, results comparable to those in the international literature.

From our cadaveric study, it could be inferred that in proximal humerus surgeries with MIPO techniques, the distance of the axillary nerve in relation to the acromion and the application of the plate centered on this bare, hypovascular spot, posterior to the bicipital groove should be considered to avoid pinching of the anterior vessel.