Summary

The proximal insertions of the biceps brachii fuse together well below the pectoralis major tendon, which is an important consideration when completing an all-arthroscopic subpectoral biceps tenodesis.

Abstract

Introduction

The biceps brachii is the most variable muscle in the upper arm, with two separate proximal origins and a single distal insertion. The long head of the biceps is a common shoulder pain generator that is often managed surgically with tenotomy or tenodesis. The pectoralis major tendon (PMT) is a useful surgical landmark for both open and arthroscopic biceps tenodesis. A good understanding of the biceps brachii anatomy at superior and inferior PMT borders is important to avoid tenodesis of the short head, or both heads during a subpectoral biceps tenodesis. The purpose of this cadaveric anatomy study was to identify whether the short and long heads of the biceps brachii were separate or fused at the level of the PMT insertion. A secondary purpose of this study was to identify whether the long head structure (tendon, musculotendinous, muscle) was different at the upper and lower borders of the PMT respectively.

Methods

Twenty-one cadaveric upper arm specimens from 11 cadavers were dissected via a standard deltopectoral approach. The short and long heads of the biceps brachii were identified. The insertion of the PMT was elevated off the humerus to assess whether the biceps brachii proximal insertions were separate or fused at the upper and lower borders of the PMT respectively. The mean fusion distance and standard deviation of the short and long heads with relation to the PMT inferior border was recorded. A Chi squared test assessed whether the structure of the long head was different at the upper and lower borders of the PMT respectively.

Results

The mean fusion distance of the proximal biceps insertions was 95.5  38.4 millimeters (mm) distal to the inferior border of the PMT. The proximal muscle bellies fused proximal to the PMT inferior border in only 1 of 21 specimens included. The long head musculotendinous structure started an average of 18.7  33.7mm distal to the PMT superior border and 32.8  38.3mm proximal to the PMT inferior border. The long head muscle belly started an average of 76.9  26.9mm distal to the superior border and 30.7  23.4mm distal to the inferior border of the PMT. There was a significant association between the PMT border and the structure of the long head of the biceps brachii, 2 (2, 21) = 24.5, p < 0.001.

Discussion And Conclusion

The most important finding of this study was that the biceps brachii proximal insertions fuse together well below the PMT inferior border. The PMT is a useful surgical landmark for both open and arthroscopic biceps tenodesis. Recently, an all-arthroscopic subpectoral biceps long head tenodesis at the PMT inferior border has been described. A good understanding of the biceps brachii anatomy at superior and inferior PMT borders is important to avoid tenodesis of the wrong head, or both heads during an all-arthroscopic subpectoral biceps tenodesis.