A new variety of chondrocoracoideus muscle, or an additional head of pectoralis major muscle

Kacper Ruzik,Łukasz Olewnik,Georgi P. Georgiev,Nicol Zielinska,R. Shane Tubbs,Iva N. Dimitrova

doi:10.1007/s00276-022-02887-x

Abstract

The pectoralis major and pectoralis minor muscles are located in the anterior chest wall. This region is characterized by high morphological variability. During dissection an additional muscle was found, originating from the lateral border of the pectoralis major muscle. After fusion it passed into the tendinous part coursing under the insertion of the pectoralis major muscle, then formed a common junction with the short head of the biceps brachii muscle, the distal attachment of which is on the coracoid process. Such an accessory structure could lead to neurovascular compression and cause thoracic outlet syndrome, of which pain is usually the first symptom. This muscle has not been described in the literature so far and for that reason we can name the present case as an unique structure.

Highlights

The pectoralis region is characterized by high morphological variability
The first interesting variant is a pectoralis minimus mus‐ cle, known as the sternocostocoracoidian. It originates from the first rib cartilage and its insertion is on the coracoid process
The pectoralis intermedius usually coexists with the pectoralis quartus, its proximal attachment arising near the costochondral junction of the fifth and sixth ribs [4]

Summary

Introduction

The pectoralis region is characterized by high morphological variability. Interestingly, the PM or PMi can be completely absent [1]. The present report describes an accessory structure originating in the muscle belly of the PM and fusing with the lateral border of the PM at the level of the seventh rib. After this fusion it passes into tendinous part, crossing under the PM, and is connected to the short head of the biceps brachii; the common junction has its insertion on. The third, abdomi‐ nal, part was 164.44 mm long and 15.99 mm wide—Table 1 During this anatomical dissection an additional structure divided into muscle belly and tendon was found.

Discussion

Conclusion