Surgery about the coracoid: neurovascular structures at risk

Abstract

Purpose: The purpose of this study was to examine the neurovascular structures at risk when performing surgery about the coracoid.

Type of study: Anatomic cadaveric study.

Methods: Five fresh-frozen cadaveric shoulders were dissected to determine the dimensions of the coracoid and the distance from the coracoid to adjacent neurologic and vascular structures. The minimal distance from the coracoid tip to the axillary nerve, musculocutaneous nerve, the lateral cord of the brachial plexus, and the axillary artery was measured using a precision caliper. Similarly, the minimal distance from the base of the coracoid to the axillary nerve, musculocutaneous nerve, the lateral cord of the brachial plexus, and the axillary artery was measured.

Results: The coracoid tip was defined as that portion of the bone that was distal to the "elbow" of the coracoid. Results showed that the mean width (medial-to-lateral dimension in the plane of the subscapularis tendon) of the coracoid tip was 15.9 +/- 2.2 mm, and the mean length of the coracoid tip was 22.7 +/- 4.5 mm. The mean thickness of the coracoid tip at its midportion was 10.4 +/- 1.5 mm. The portion of the coracoid tip which was closest to the neurovascular structures was the anteromedial portion of the coracoid tip. The distance from the anteromedial portion of the coracoid tip to the axillary nerve, the musculocutaneous nerve, the lateral cord, and the axillary artery was 30.3 +/- 3.9 mm, 33.0 +/- 6.2 mm, 28.5 +/- 4.4 mm, and 36.8 +/- 6.1 mm, respectively. Similarly, the portion of the base of the coracoid that was closest to the neurovascular structures was its anteromedial portion. The shortest distance from the anteromedial aspect of the base of the coracoid to the axillary nerve, the musculocutaneous nerve, the lateral cord, and the axillary artery was 29.3 +/- 5.6 mm, 36.5 +/- 6.1 mm, 36.6 +/- 6.2 mm, and 42.7 +/- 7.3 mm, respectively.

Conclusions: Procedures about the coracoid are relatively safe procedures. The lateral cord of the brachial plexus is at greatest risk during dissection about the tip of the coracoid, and the axillary nerve is at greatest risk during dissection about the base of the coracoid. The safety of arthroscopic coracoplasty or interval releases is further increased by the fact that most of the work is performed on the lateral aspect of the coracoid, which is even further away from the neurovascular structures.

Clinical relevance: This study quantifies the relative risk of injury to neurovascular structures during arthroscopic surgery about the coracoid.