243Trifurcating superficial brachial artery

Trifurcation of superficial brachial artery: a rare case with its clinico-embryological implications N. Gupta1, A. Anshu2, R. Dada1

1Department of Anatomy, AIIMS; 2Department of Anatomy, VMMC & Safdarjung Hospital, New Delhi, India

Case report Clin Ter 2014; 165 (5):243-247. doi: 10.7417/CT.2014.1753

Correspondence: Dr. Nidhi Gupta. Senior Resident, Department of Anatomy.AIIMS, New Delhi – 110029 India. Tel.: 00919013942019.E-mail: drnidhiaiims@gmail.com

Copyright © Società Editrice Universo (SEU)ISSN 0009-9074

Introduction

Brachial artery is the continuation of the Axillary artery beyond the distal border of the tendon of teres major and terminates at a distance of approximately 3cm distal to intercondylar line of elbow, by bifurcating into radial and ulnar artery (1). In the brachium, it is positioned deep to

Abstract-

Literatures on vasculature of upper limbs are crammed with reports of distinctly deviant version of normally prevalent vessels having modi-fied origins, altered branching and odd courses. A unique anatomical variation in vascular pattern was observed during routine dissection of right upper limb in gross anatomy laboratory, AIIMS, New Delhi, India. The brachial artery was placed superficial to median nerve in the arm and therefore it was called superficial brachial artery. In the cubital fossa, 2.8 cm distal to intercondylar line of elbow joint, this superficial brachial artery terminated by trifurcation into radial, com-mon interosseous and ulnar branches. Strikingly the ulnar branch, after its origin ran superficially over the median nerve and epitrochlear superficial flexor group of muscles of forearm in succession for the initial third of its course in the forearm, consequently it was addressed as superficial ulnar artery.

The existence of superficial brachial artery in place of normal brachial artery, its termination by trifurcation into radial, common interosseous and superficial ulnar arteries with remarkably different courses, leads to confusing disposition of structures in the arm, cubital fossa and in the forearm and collectively makes this myriad of ana-tomical variations even rarer. The clinico-embryological revelations for combination of these unconventional observations, apprises and guides the specialized medical personnel attempting blind and invasive procedures in brachium and ante-brachium. This case report depicts the anatomical perspective and clinical implications on confronting a rare variant vasculature architecture pattern of upper limb. Clin Ter 2014; 165(5):243-247. doi: 10.7417/CT.2014.1753

Key words: superficial brachial artery, superficial ulnar artery, trifurcation, variations

median nerve and is escorted by a pair of venae commitantes. Besides yielding terminal branches, it gives away profunda brachii, superior middle and inferior ulnar collateral and various muscular branches in the arm. After origin, the radial artery descends along lateral side of front of forearm lying medial to shaft of radius proximally, and anterior to it distal-ly. In the proximal one third of forearm it is overlapped by the belly of brachioradialis muscle whereas, in the distal two third part of forearm it is covered only by the skin and fascia (1). Ulnar artery after its origin descends to reach medial side of front of forearm midway between elbow and wrist. When traced further it is covered by the skin, superficial and deep fascia of forearm (1). In the cubital fossa, the median nerve lies medial to ulnar artery for a distance of 2.5 cm (2). Subsequently it crosses ulnar artery lying superficial to it before entering between two heads of pronator teres. Com-mon interosseous artery is a branch of ulnar artery which originates just distal to radial tuberosity, it reaches proximal border of the interosseous membrane to divide into anterior and posterior interosseous artery (1).

Variations in the vascular pattern of upper limb are mo-derately frequent (3). The brachial artery can lie superficial to the median nerve in almost entire course contrary to its deeper disposition with the same, referred to as superficial brachial artery (3). This superficial brachial artery may coe-xist with a deeply placed brachial artery (3), can exist alone in the brachium to substitute the main trunk as in the present case or give rise to other arterial segments which align itself parallel, deep or superficial to median nerve(3, 4). Some-times the brachial artery may trifurcate (5, 6) erratically. Nevertheless, the documentation of trifurcation of superficial brachial artery into radial, common interosseous and super-ficial ulnar artery is extremely scarce in literature.

This report emphasize embryological elucidation and clinical repercussion in a case, presenting with unilateral su-perficial brachial artery in the brachium , its trifurcation into radial, common interosseous and superficial ulnar arteries along with unique relation of superficial ulnar artery with median nerve and superficial epitrochlear forearm flexors in the cubital fossa and forearm.

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Case report

During routine dissection in right upper limb of 65 year old male embalmed cadaver at gross Anatomy laboratory of AIIMS, New Delhi, for undergraduate medical training program certain variations in the arterial pattern were no-ticed.

The axillary artery continued as superficial brachial artery in place of brachial artery when traced distal to outer border of teres major. This superficial brachial artery was seen running superficial to the normally formed median nerve in its entire length in the brachium before it eventually terminated by trifurcation into radial, ulnar and common in-terosseous arteries (Fig. 1, 2). This trifurcation of superficial brachial artery was located 2.8 cm distal to intercondylar line of elbow deep to the bicipital aponeurosis.

Superficial ulnar artery, after its formation in the cubital fossa, passed deep to bicipital aponeurosis to enter forearm. In its proximal one third parts, before aligning itself with ulnar nerve at the junction of proximal and middle third of forearm, it obliquely crossed superficially over the median nerve and ran successively over the pronator teres, flexor carpi radialis, and flexor digitorum superficialis muscles, instead of passing deep to these superficial flexors of forearm (Fig. 1, 2). Palmaris longus muscle was absent among these

superficial flexors of forearm. The roof of the superficial ulnar artery in its proximal third course was formed by an-tebrachial fascia. When traced further it assumed customary arrangement of typical ulnar artery on the lateral side of ulnar nerve in the middle and distal third of forearm.

The radial artery arising from the trifurcation of the superficial brachial artery was observed lying between an-tebrachial fascias superficially and belly of brachioradialis followed by anterior surface of radius in the deeper plane (Fig. 1, 2).

Common interosseous began as terminal branch from trifurcation of superficial brachial artery (Fig. 2). This artery measured 1.2 cm in length before it divided at proximal bor-der of interosseous membrane of forearm, into much wider anterior interosseous and narrower posterior interosseous arteries. These branches had normal morphology when observed distally.

Upon deeper exploration, no significant anastomotic communications between radial, ulnar and common inte-rosseous arteries were observed.

Dissection on the opposite upper limb of the same cadaver did not reveal any notable unusual finding. Upon verification, no history of any disease as well as evidence of invasive procedure inflicted on vessels or nerves in upper limbs was found.

Fig.1. Photograph showing dissected ventral region of right arm and forearm of an adult cadaver. B – Brachialis, BB – Biceps Brachii, BR – Brachioradialis, ECRL – Extensor Carpi Radialis Lon-gus, FDS – Flexor Digitorium Superfi-cialis, FCU – Flexor Carpi Ulnaris, FCR – Flexor Carpi Radialis, MN – Median Nerve, PT – Pronator Teres, RA – Ra-dial Artery, SBA – Superficial Brachial Artery, SBRN – Superficial Branch of Radial nerve, SP – Supinator, SUA – Superficial Ulnar Artery.

Fig. 2. Photograph showing dissected ventral region of cubital fossa of an adult cadaver.AIA – Anterior Interos-seous Artery, BR – Brachioradialis, CIA – Common Interosseous Artery, ECRL – Extensor Carpi Radialis Lon-gus, FCU – Flexor Carpi Ulnaris, FCR – Flexor Carpi Radialis, MN – Median Nerve, Msb – Muscular branch of Su-perficial Ulnar Artery, PIA – Posterior Interosseous Artery, PT – Pronator Teres, SBA – Superficial Brachial Ar-tery, SP – Supinator, SUA – Superficial Ulnar Artery, RA – Radial Artery, RIA – Recurrent Interosseous Artery, RRA – Recurrent Radial Artery, TB – Tendon of Brachialis, TBB –Tendon of Biceps Brachii, CIA – Common Interosseous Artery, TP – Trifurcation Point.

245Trifurcating superficial brachial artery

Discussion

Deviations from the conventional anatomical foray have revealed a bewildering spectrum of variations in the arterial patterns of brachium and antebrachium. The brachial artery is infrequently described running superficially, contrary to its normal disposition of being placed deep to median nerve in the brachium and had been called superficial brachial artery (3, 4). Superficial brachial artery is a steady developmental vessel. It may degenerate, coexist with brachial artery (7) or may be the only vessel existing for the supply of superior extremity (8). In a major study, the incidence of existence of superficial brachial artery was found to be 4.9% (3). The statistical difference derived for the existence of superficial brachial artery was concluded to be insignificant between male or female cadavers or in between right or left side

(3). In another exploration, superficial brachial artery was present in 12.3% population and based upon its fate it had been classified into three types (9).

It continued up to the cubital fossa and bifurcated into radial and ulnar artery.

It continued as radial artery and was acknowledged as high origin of radial artery.

It continued as ulnar artery and was acknowledged as high origin of ulnar artery.

In this case, the superficial brachial artery abided by its definition (3, 4) and had similar course to the first group (9)

but instead of bifurcation, it underwent trifurcation.Termination of brachial arteries had been extensively

assessed and evaluated (10, 11). In earlier studies it was de-monstrated that the brachial artery can ramify by trifurcation quite proximally than its usual termination, into radial, ulnar and common interosseous arteries but the precise description about pattern of termination in case of trifurcation is obscure

(1). In cases of trifurcation, additional possible branches coexistent with radial and ulnar branches may be common interosseous, radial recurrent, or the median arteries (12).

Trifurcation of brachial artery was observed in only one case out of fifty dissections of upper limbs, which led to the formation of radial, ulnar and radial recurrent arteries (13). Subsequently, the trifurcation of brachial artery into radial, ulnar and common interosseous arteries was also reported

(14). One more case, reported the high level of bilateral trifurcation of brachial artery in the lower third of arm into radial, ulnar and common interosseous artery (15).

Furthermore, the superficial brachial artery, if observed incidentally in certain cases, terminates by dividing into a medial superficial antebrachial artery and a lateral branch that continues in the forearm as a part of definitive radial artery (16).

Uniqueness of our case lies in the fact that, the superfi-cial brachial artery had unusual termination by trifurcation, unlike presumed bifurcation (16). Moreover, in outstan-ding contrast to a few recorded cases of trifurcation of the main trunk of the brachial artery (12-15), it was rather the superficial brachial artery which displayed termination by trifurcation.

The location of trifurcation was in the cubital fossa rather than high up in the arm (15). Also, in this case, the common interosseous artery was emanating at the trifurcation of superficial brachial artery besides radial and ulnar arteries,

which was dissimilar with the presentation of radial, ulnar and recurrent radial arteries resulting from trifurcation of the main brachial artery in the cubital fossa (13).

The superficial ulnar artery is a variant of the normally found ulnar artery, which may originate at axilla, brachium or in cubital fossa (3). It adopts a superficial pathway in the forearm before entering the hand and may be observed in the range of 0.6-9.3% (17). The superficial ulnar artery emanating from a trifurcating superficial brachial artery is exceedingly rare until now. However, in the current case, the superficial ulnar artery conforms to most of its other typical traits: such as the subfascial course in the antebrachium, its situation superficially over the median nerve in the cubital fossa and its association with absence of palmaris longus tendon (18).

The superficial radial artery is defined as a radial artery coursing over the tendons forming boundaries of the snuff box and has an incidence of 0.4% (3). In the present case, although the radial artery had a very shallow course in the forearm, but it fails to fulfill strict criterion to be designated as superficial radial artery as it crossed beneath the tendons of snuff box during its transition from forearm to hand. Ho-wever, several evidences recorded in past (3), suggests that the radial artery may acquire a superficial course at variable level in the forearm and justify the variant morphology observed in this case.

The altered arterial development is attributed to hemo-dynamic factors, disposition of fetus in uterus, initial limb movements, molecular signaling, genetic expression and unusual proliferation and regression in primitive stages (17). The occurrence of variations in the arterial pattern is correlated with persistence and degeneration of selective pri-mitive vascular channels in embryonic life .The anomalous vascular configuration and branching in upper limb vessels is attributable to eventual orchestrated outcomes of (19):a. The predilection of odd pathway in the embryological

vascular plexus; b. The perseverance of vessels destined to be obliterated; c. The waning of vessels ordained for eventual persisten-

ce;d. Unfinished development of vasculature and; e. Amalgamation and dissolution of the parts of vascular

plexus which are customarily discrete.The variant vessels resulting from such observations

should be studied as separate entities and an endeavor for ontogenetic justification is recommended (11). A mor-phogenetic pattern correlating embryological events and anatomical disposition in the development of upper limb vasculature can successfully formulate the construction of normal adult pattern of vessels and any unexpected variations deviating from the usual design. The intriguing arrangement of vasculature in brachium and antebrachium can be realized by means of modification in the morphogenetic pattern (11)

(Fig. 3A, 3B and 3C).The fetal superficial brachial artery SBA located in the

superficial plane of developing upper limb musculature is imperative in development of superior extremity vasculature (Fig. 3A). This superficial brachial artery SBA ramifies into two terminal branch. The medial branch is known as super-ficial antebrachial artery SABA and the lateral continues as lateral branch of superficial brachial artery called as LSBA.

246 N. Gupta et al.

SABA further divides into two terminal branches, named as median branch of superficial antebrachial artery MSABA and ulnar branch of superficial brachial artery USABA. The primitive axial artery AA proceeds deep to the plane of upper limb musculature yields two branches namely the trunk of radial artery laterally TRA and trunk of ulnar artery TUA medially before continuing as common interosseous artery CIA. CIA gives another branch distally as trunk of median artery TMA before terminating into anterior and posterior interosseous branches.

The branches of superficial brachial artery namely: LSBA, MSABA and USABA establish communications with the deep seated primitive axial artery AA through TRA, TMA and TUA respectively. These communications are destined to form the proximal parts of radial artery RA, median artery MA and ulnar artery UA at maturity of pri-mitive vasculogenesis.

Gradually, there is establishment of supremacy of flow of deeper set of arterial network derived from AA over the superficial set of arterial network formed by SBA, LSBA and the SABA. The preanastomotic segments of distal RA, MA and UA, formed by subsequent ramification and extension of SBA , degenerates to eventually yield the adult arterial pattern ( Fig. 3B).

In the present case, an unusual anastomotic channel AC (Fig. 3C) appeared to communicate the point of bifurcation of SBA with the segment of CIA distal to origin of TUA. Also, the segment of AA between the site of origin of SBA

and the trunk of CIA proximal to its communication with AC regressed completely. There is eventual dissolution of TRA, MSABA and TUA in the sequence of development of brachio-antebrachium vasculature.

In this case, owing to dissolution of a part of AA in the brachium, the normal brachial artery of the arm derived from the AA, which is placed deep to median nerve in the brachium have vanished. The SBA replaced the brachial artery as the prime vessel of arm and was flanked between the deep fascia of brachium and the median nerve because developmentally it is located in the superficial plane.

The trifurcation of SBA can be appreciated by assuming the opening of AC at the point of bifurcation of SBA into LSBA and SABA.

The initial part of ulnar artery is normally derived from TUA. In this case, the gap between the SBA and UA was filled by SABA emanating from trifurcation and its conti-nuation USABA.

Thus, the overall situation of UA in its proximal part is superficial to median nerve and the epitrochlear origin of forearm flexor group of muscles, underneath the deep fascia of forearm to validate its name of superficial ulnar artery SUA.

The explanation of origin of radial artery from trifur-cation and its superficial course throughout the forearm is justified by taking into consideration the unusual persistence of LSBA channelizing SBA with RA along with concurrent regression of TRA.

Fig. 3A, 3B, 3C. Schematic Diagram showing arrangement of various temporary, permanent and abnormal vascular connections during development of upper limb vasculature. AA-Axillary artery, AC- Anastomotic Channel, CIA- Common Interosseous Artery, LSBA- Lateral Branch of Superficial Brachial Artery, MSABA- Medial Branch of Superficial Antebrachial Artery, SABA- Superficial Antebrachial Artery, TMA- Trunk For Median Artery, TRA- Trunk for Radial Artery, TUA- Trunk for Ulnar Artery, USABA- Ulnar Branch of Superficial Antebrachial Artery, MA- Median Artery, UA- Ulnar Artery, RA- Radial Artery. Fig. 3A. Superficial (shaded) and Deep (non-shaded) arterial networks during development. Fig. 3B. The pattern of arterial networks observed after morphogenesis at birth. Fig. 3C. An abnormal anastomotic channel AC appeared between CIA and the site of bifurcation of SBA in the present case, resulting in trifurcation of SBA.

247Trifurcating superficial brachial artery

Attributable to its atypical course, the complex pattern of superficially placed arterial network in brachium and antebrachium is more vulnerable to injury owing to very striking resemblance to networks of superficial antecubital veins. The tricky situation must be acknowledged before attempting blind and invasive surgical procedures in this area to avoid inadvertent injuries. The aneurysm of brachial and ulnar artery, hematoma resulting from accidental arterial injuries in attempted venepuncture or dislocated fragment in fracture of elbow joint may compress the deeply placed median nerve and can lead to its entrapment neuropathy in its distribution. The designing of reliable forearm skin flap with neuro-vascular potential for contracture replacement and reconstructive surgeries is dependent on the prior acquisition of precise knowledge of arterial pattern and its cutaneous branches, derived from accurate angiographic images. The recurrent branches from the radial, ulnar and common interosseous arteries contributing to arterial anastomosis around elbow joint is quite significant in making manage-ment strategies in fracture and dislocation of elbow joints. Acquaintance of unusual antebrachial arteries is prerequisite for the planning of establishment of autogenous fistula in end stage renal disease patients undergoing dialysis. The utility of antebrachial arterial conduit for coronary artery bypass graft requires accurate knowledge of the pattern and extent of atypical blood vessels.

Conclusion

In conclusion, for reducing complications, failures and morbidity, the clinicians and surgeons approaching these regions must inculcate habit of anticipating encrypted anatomical variations of upper limb vasculature as a pre-cautionary step before undertaking any procedures. The precious age old practices of inspection and palpation of vessels in clinical examination of brachium and antebra-chium ,followed by subsequent doppler and angiographic evaluation, on encountering ambiguous interpretation is highly recommended prior to any invasive exploration in this region. Also the individual entity exhibiting variations must be review under light of relevant literature.

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