Case Report Singapore Med J 2008; 49(9) : e254 Multiple accessory structures in the upper limb of a single cadaver Vollala V R, Nagabhooshana S, Bhat S M, Potu B K, Rakesh V ABSTRACT terms of the number and morphology of its heads.(1-4) The arterial and muscular variations of the This muscle frequently has more than two heads arising upper limbs are common but important with from the humerus at the insertion of the coracobrachialis regard to surgical approaches. Even though or the neck of the humerus. There are reports describing anomalies of the coracobrachialis muscle supernumerary bicipital heads, ranging from three to are rare, anatomical variations of the biceps seven. Among them, the three-headed variant represents brachii, existence of the accessory muscles in the most common type that has been reported with a the forearm and persistent median artery are prevalence ranging from 7.5%–18.3%.(2,5-8) known and well documented. During routine Normally, the coracobrachialis muscle arises dissection, we observed some important from the tip of the coracoid process of the scapula anatomical variations in a 50-year-old male in common with the short head of the biceps brachii cadaver. The variations were unilateral. The muscle and inserts into the middle of the anteromedial anomalies were: third head for biceps brachii surface of the shaft of the humerus. The reported muscle, an accessory belly for coracobrachialis morphological variations of the coracobrachialis muscle crossing the median nerve and brachial muscle include accessory slips inserting to the medial vessels and continuing with the medial head epicondyle of the humerus, medial supracondylar of triceps brachii muscle to be inserted to the ridge, medial intermuscular septum, the lesser olecranon process (coracoulnaris), a persistent tubercle and a supernumerary head passing over the median artery and an additional muscle in the shoulder joint.(9-11) The presence of accessory muscles in Department of anterior compartment of forearm. Although the forearm was reported back in 1813 by Gantzer, and Anatomy, Melaka Manipal there are individual reports about these from then on, these muscles have been reported with Medical College, variations, the combination of these variations variable attachments.(12-21) The accessory heads of the Manipal University, Manipal 576104, in one cadaver has not previously been described deep flexors of the forearm (Gantzer’s muscles) have Karnataka, in the literature. Awareness of these variations been described as small bellies inserting either into India is necessary to avoid complications during the flexor pollicis longus (FPL) or flexor digitorum Vollala VR, MSc Lecturer radiodiagnostic procedures or surgeries in the profundus (FDP). The median artery is a transitory upper limb. Nagabhooshana S, vessel that represents the arterial axis of the forearm MSc, PhD during early embryonic life. It normally regresses Professor Keywords: anatomical variants, biceps brachii, in the second embryonic month to become the small Bhat SM, MSc coracobrachialis, coracoulnaris, median slender artery, arteria comitans nervi mediani.(22) Associate Professor artery Persistence of the median artery is not uncommon, and Department of Anatomy, Singapore Med J 2008; 49(9): e254-e258 its incidence is reported as ranging between 1.5% and Kasturba Medical 27.1%.(23-25) College, Manipal University, IntrODUctiON Manipal 576104, Case RepOrt Karnataka, The classical description of attachments of the biceps India brachii muscle include: the short head arising from The study involved the upper limb dissections of a 50- Potu BK, MSc the tip of the coracoid process of the scapula and the year-old male cadaver. The dissections of both upper Lecturer long head arising from the supraglenoid tubercle of extremities (right and left) of the body were carried out Rakesh V, MSc the scapula and from the glenoidal labrum. Distally, according to the instructions by Cunningham’s Manual Lecturer (26) the two bellies unite to form a common tendon which of Practical Anatomy. The body was preserved Correspondence to: is inserted into the posterior rough part of the radial by the injection of a formalin-based preservative Dr Venkata Ramana Vollala tuberosity and through the bicipital aponeurosis to (10% formalin) and stored at −4°C. Before taking Tel: (91) 820 292 2642 Fax: (91) 820 257 1905 the subcutaneous posterior border of ulna. It is one photographs, the dissected region was rinsed with water. Email: ramana.anat@ of the most variable muscles in the human body, in The third head of biceps brachii muscle, accessory gmail.com Singapore Med J 2008; 49(9) : e255 1a 1b Fig. 1a Photograph of the anterior compartment of the left Fig. 1b Schematic diagram of the anterior compartment of arm shows the third head of biceps brachii and accessory the left arm. belly of coracobrachialis crossing the median nerve and BB: biceps brachii; CB: coracobrachialis; MHT: medial head brachial vessels. of triceps brachii; NVB: neurovascular bundle (median nerve, BB: biceps brachii; THB: third head of biceps brachii; CB: ulnar nerve and brachial vessels); MCN: musculocutaneous coracobrachialis; MHT: medial head of triceps brachii; NVB: nerve neurovascular bundle (median nerve, ulnar nerve and brachial vessels); MCN: musculocutaneous nerve belly of coracobrachialis muscle crossing the median for the middle finger (Fig. 2). The following are the nerve and brachial vessels, a persistent median artery approximate sizes of the muscle: muscle length 7 cm, and an additional muscle in the anterior compartment tendon length 15 cm, muscle width 0.8 cm, and tendon of forearm were found in the left upper limb. However, width 0.3 cm. The additional muscle belly was anterior the right upper limb showed no abnormality. to both the anterior interosseous nerve and vessels, and The accessory head of the biceps brachii muscle the ulnar artery. The nerve and arterial supply to the arose from the shaft of the humerus between the muscle came from the anterior interosseous nerve and insertion of the coracobrachialis muscle and origin ulnar artery, respectively. There was persistent median of the brachialis muscle. The additional muscle fibres artery taking origin from the anterior interroseous formed a narrow tendon which inserted into the medial artery and accompanied the lateral aspect of the median aspect of the tendon of the biceps brachii muscle to be nerve up to the wrist (Fig 3). The artery gave muscular inserted to the radial tuberosity (Fig. 1a). In the same branches to the nearby muscles. arm, we also found an anomalous coracobrachialis muscle. The origin of coracobrachialis was normal DiscUssiON from the tip of the coracoid process along with the Although the third head of biceps brachii is a common short head of biceps brachii, but the muscle fibres occurrence in mammals,(27-29) previous studies in divided into superficial and deep bellies. The deep human beings show that the third head of biceps fibres inserted to the medial surface of the middle of the brachii is seen in about 8% of Chinese,(3) 10% of shaft of the humerus, deep to the neurovascular bundle white Europeans,(3,30) 12% of black Africans,(3) 18% of the anterior compartment of the arm. The superficial of Japanese,(3) 20.5% of South African blacks, 8.3% fibres crossed the median nerve, ulnar nerve, brachial of South African whites,(5) 20% of Brazilian whites, vessels and continued with the medial head of triceps 9% of Brazilian blacks,(2) 15% of Turks,(6) and merely brachii muscle to be inserted to the olecranon process 2% in the Indian population.(31) Thus, the occurrence (Figs. 1a & b), forming the potential site for entrapment of third head of biceps brachii in the Indian population or compression of the neurovascular bundle. A review is rare. According to Rodriguez-Niedenfuhr et al, of the literature suggests that the occurrence of this the accessory bicipital head in the present case variation is very rare globally. The nerve supply to corresponds to the inferomedial type.(7) Based on its the third head of biceps brachii and coracobrachialis origin, it may be considered as a remnant of the long muscle was from the musculocutaneous nerve. head of coracobrachialis muscle, an ancestral hominoid There was an additional muscle in the anterior muscle.(32,33) The third head of biceps brachii in our compartment of the forearm. It was seen deep to the case originated from the anteromedial surface of the flexor digitorum superficialis (FDS) and took origin humerus distal to the insertion of the coracobrachialis, from the undersurface of the FDS distal to its origin passed inferomedial to the main biceps brachii and from the medial epicondyle of humerus. The muscle anterior to the brachialis muscle, and inserted into the belly ended in a long tendon in the middle part of the medial side of the common biceps tendon. The medial forearm and the tendon merged with the tendon of FDP humeral origin of the third head may provide additional Singapore Med J 2008; 49(9) : e256 Fig. 2 Anterior photograph of the left forearm. The accessory head (Gantzer muscle) of the flexor digitorum profundus arises from under the surface of the flexor digitorum Fig. 3 Photograph shows the persistent median artery. superficialis and inserts into the tendon for the middle finger B: brachial artery; U: ulnar artery; R: radial artery; PMA: of flexor digitorum profundus. persistent median artery; MN: median nerve. FDP: flexor digitorum profundus; Ah of FDP: additional head of flexor digitorum profundus; FDS: flexor digitorum superficialis, *******: tendon of additional head of flexor digitorum profundus. strength to the biceps during supination of the forearm did not find any such reported clinical cases, this kind and elbow flexion irrespective of shoulder position.(34) of neurovascular disorders may be similar to the cases The presence of the third head may cause unusual bone of entrapment by ligament of Struthers.