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A Study on Variations of Accessory Coracobrachialis Muscle Along with Variations of Biceps Brachii Muscle

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A Study on Variations of Accessory Coracobrachialis Muscle Along with Variations of Biceps Brachii Muscle ORIGINAL PAPER A study on variations of accessory coracobrachialis muscle along with variations of biceps brachii muscle Debalina Maiti, Swagata Bhattacharya Maiti D, Bhattacharya S. A study on variations of accessory coracobrachialis supracondylar ridge and medial epicondyle of humerus. The coracobrachials muscle along with variations of biceps brachii muscle. Int J Anat Var. muscle originated from the tip of coracoid process with conjoint origin of 2018;11(2): 66-69. biceps brachii muscle. We also observed that the two heads of biceps brachii SUMMARY muscle of that arm fused at a lower level than usual, almost at the level of an imaginary line joining the two epicondyles of humerus and formed a very Coracobrachialis is a muscle of arm that shows several variations in its short tendon to get inserted into the radial tuberosity of radius. attachment. After dissecting twenty eight arms of embalmed cadavers to study the variations, we found an accessory belly of coracobrachialis Key Words: Coracobrachialis; Accessory belly of coracobrachialis; Biceps brachii; muscle which originated from the tendon of coracobrachialis muscle at the Variations; Medial intermuscular septum; Medial epicondyle of humerus; Ulnar middle of the medial side of shaft of humerus and was inserted into medial nerve; Muscle tansplant INTRODUCTION MATERIALS AND METHODS orphologically, coracobrachialis muscle represents the adductor The embalmed adult cadavers used for gross anatomy dissection courses Mcompartment of arm. But it is not very important in human beings as were utilized for this study. Twenty eight arms were dissected to determine adductor muscle, due to the upright posture, as gravity plays the role of main the morphological criteria of the coracobrachialis muscle. We followed the adductor (1). In some mammals, it is tricipital in origin. In human beings, following steps: the upper two heads are usually fused while taking origin from the coracoid process and enclose musculocutaneous nerve in between so that it seems that 1. Careful dissection of the sites of origin and insertion of the muscle. musculocutaneous nerve pierces coracobrachialis muscle. Sometimes, two upper heads are found separately in human beings. The musculocutaneous 2. Any variability in the innervation of the muscle and its relationship with nerve is situated between two separate heads till insertion (2,3). The third the musculocutaneous nerve. head is usually suppressed in human beings. RESULTS Coracobrachialis muscle is reported to have many variations, like –muscle originated from the coracoid process and the capsule of the shoulder joint. Two interesting findings we noticed in this study: It was inserted into the antebrachial fascia and the medial epicondyle of the humerus (4), presence of coracobrachialis brevis inserting into the A) Almost in all cases the musculocutaneous nerve pierced the capsule of shoulder joint (5). In one case, the proximal accessory bands of coracobrachialis muscle. Most of the fleshy part of the muscle arose corachobrachialis brevis muscle started from the root of coracoid process and from the tip of coracoid process with conjoint origin of short head of a few aponeurotic fibers from the conoid ligament of clavicle and inserted biceps brachii muscle (Figure 1). The muscle was inserted by fleshy fibers to the medial intermuscular septum (6). The presence of two heads of origin at the middle of the medial border of the humerus, between the flexor for the coracobrachialis muscle, which are situated superficial (anterior) and compartment and the extensor compartment of arm (Figure 2). The two deep (posterior) to the musculocutaneous nerve. The superficial head arises heads of biceps brachii muscle were fused above mid arm level to form a mainly from most of the medial border of the tendon of the short head of single long tendon (Figure 2). the biceps brachii muscle. The deep head arises from the apex of the coracoid process of the scapula and the adjoining lateral border of the tendon of (B) One case showed an accessory belly of coacobrachialis muscle in the left the short head of the biceps brachii muscle. The musculocutaneous nerve upper limb of a female cadaver. It originated from the fleshy part of the provides a separate branch for each head. In cases where the coracobrachialis coracobrachialis muscle at its insertion at the middle of medial border of muscle was not pierced by the musculocutaneous nerve, the muscle was left humerus (Figures 3 and 4) and was inserted into medial epicondyle of formed of one head that has an origin analogous to that of the superficial humerus and medial supracondylar ridge on the left arm (Figure 5). The head. One case showed a splitting of the deep head into two bellies shortly coracobrachialis muscle was pierced by musculocutaneous nerve as usual after its origin, where the muscle appeared as being formed of three heads. (Figures 4 and 6). The fleshy accessory belly was also fused in part with Variations in the insertion were present as an additional aponeurotic medial head of triceps brachii along medial border of humerus where the insertion above the usual insertion and an aponeurotic extension to the deep medial intermuscular septum appeared to be deficient (Figure 7). The ulnar fascia on the medial aspect of the arm (7). The lower head which is usually nerve was in close relation with the substance of lower part of this belly for a suppressed in human beings; sometimes present as the ligament of Struthers reasonable distance (Figures 5-7), within the fibrous part of the muscle. We which is attached between an occasional bony spur called supratrochlear spur also observed that the biceps brachii muscle of this limb was continuous as from antero-medial surface of lower part of humerus and medial epicondyle two separate heads roughly up to a line joining two epicondyles of humerus, of humerus. Median nerve and brachial artery pass deep to the ligament and and then they joined forming a very short tendon, inserted into the radial are vulnerable to be compressed by being entrapped between the ligament tuberosity of radius (Figure 8). and bony surface (1). Department of Anatomy, R. G. Kar Medical College and Hospital, Kolkata, West Bengal, India. Correspondence: Dr. Debalina Maiti, Department of Anatomy, R. G. Kar Medical College and Hospital, Kolkata, West Bengal, India, Tel: +919836963158; e-mail: [email protected] Received: May 08, 2018, Accepted: June 12, 2018, Published: June 25, 2018 This open-access article is distributed under the terms of the Creative Commons Attribution Non-Commercial License (CC BY-NC) (http:// creativecommons.org/licenses/by-nc/4.0/), which permits reuse, distribution and reproduction of the article, provided that the original work is properly cited and the reuse is restricted to noncommercial purposes. For commercial reuse, contact [email protected] Int J Anat Var Vol 11 No 2 June 2018 66 Maiti et al. Diagram 1: Corresponds to Figure 1 Figure 1) Illustration shows, left Coracobrachialis muscle originating conjointly with short head of left biceps brachii muscle, Musculocutaneous nerve piercing the muscle. BB – Biceps brachii muscle; CB – Corachobrachialis muscle; MCN Diagram 3: Corresponds to Figure 3 – Musculocutaneous nerve; MN -- Median nerve; BA – Brachial artery; UN – Figure 3) Illustration shows, Variatioins-Accessory belly of Coracobrachialis Ulnar nerve; ABCB – Accessory belly of Coracobrachialis muscle muscle on left arm, taking origin from the insertion site of the left Coracobrachialis muscle Diagram 2: Corresponds to Figure 2 Figure 2) Illustration shows, conjoint origin of left coracobrachialis muscle with short head of left biceps brachii muscle. It is inserted into middle of humerus by Diagram 4: Corresponds to Figure 4 fleshy fibres and pierced by Musculocutaneous nerve. Ulnar nerve and Median Figure 4) Illustration shows, Variant muscle belly taking origin from the nerve are medial to the muscle. Two heads of Biceps brachii muscles are fused insertion site of left Coracobrachialis muscle (after retraction) above mid-arm level 67 Int J Anat Var Vol 11 No 2 June 2018 A study on variations of accessory coracobrachialis muscle along Diagram 7: Corresponds to Figure 7 Diagram 5: Corresponds to Figure 5 Figure 7) Illustration shows, The accessory belly of the muscle is connected with fibers of the medial head of left Triceps brachii muscle along the lateral Figure 5) Illustration shows, the variant belly is inserted into the medial margin of left arm epicondyle of left humerus and the left medial supracondylar ridge of humerus Diagram 6: Corresponds to Figure 6 Diagram 8: Corresponds to Figure 8 Figure 6) Illustration shows, the variant belly is in close proximity with left Ulnar Figure 8) Illustration shows, two heads of left Biceps brachii muscle fuse at lower nerve. The left Coracobrachialis muscle is pierced by left Musculocutaneous nerve level than usual Int J Anat Var Vol 11 No 2 March 2018 68 Maiti et al. DISCUSSION single muscle mass. Thereafter, some muscle primordia disappear through cell death (8). Failure of muscle primordia to disappear during embryologic The coracobrachialis muscle is more important morphologically than development may account for the presence of the accessory belly of functionally. The coracobrachialis muscle in the arm is morphologically coracobrachialis muscle reported in this case. the sole representative of adductor group of muscle in the arm, but such function during the process of evolution became insignificant in man. Three
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