Unusual additional distal aponeurotic slips of biceps brachii: A rare variation

Ritu Singh; Pooja Singh; Ranjana Verma; Rakesh Kumar Diwan

doi:10.4103/JASI.JASI_97_20

CASE REPORT

Year : 2022 | Volume : 71 | Issue : 1 | Page : 74-76

Unusual additional distal aponeurotic slips of biceps brachii: A rare variation

Ritu Singh¹, Pooja Singh², Ranjana Verma³, Rakesh Kumar Diwan⁴
¹ Department of Anatomy, School of Medical Sciences and Research, Sharda University; Department of Anatomy, King George's Medical University, Lucknow, Uttar Pradesh, India
² Department of Anatomy, Shri Shankaracharya Institute of Medical Sciences, Bhilai, Chhattisgarh, India
³ Department of Anatomy, Government Institute of Medical Sciences, Greater Noida, India
⁴ Department of Anatomy, King George's Medical University, Lucknow, Uttar Pradesh, India

Date of Submission	23-May-2020
Date of Acceptance	15-Nov-2021
Date of Web Publication	17-Mar-2022

Correspondence Address:
Dr. Ritu Singh
Department of Anatomy, School of Medical Sciences and Research, Sharda University, Greater Noida
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JASI.JASI_97_20

Abstract

Biceps brachii muscle is basically a powerful supinator. Although there is ample literature on variant origin of biceps brachii, variant insertion pattern was minimally reported. Here, we report a case, in which apart from usual insertion of biceps brachii, three distal accessory aponeurotic slips were found on the right arm of 55-year-old embalmed male cadaver. Two slips were arising from the lateral most part of bicipital aponeurosis traversing across the cubital fossa superficial to the brachial artery and median nerve and get attached to deep fascia covering the brachioradialis and pronator teres. Third accessory aponeurotic slip arises from the lateral side of biceps brachii muscle belly, traversing superficial to the musculocutaneous nerve and get attached to deep fascia covering the lateral border of brachioradialis and extensor carpi radialis longus. These extra slips may affect the kinematics of biceps brachii muscle and adds to the differential diagnosis of variety of clinical symptoms of neurovascular syndrome.

Keywords: Accessory aponeurotic slips, biceps brachii muscle, musculocutaneous nerve, superficial branch of radial nerve

How to cite this article:
Singh R, Singh P, Verma R, Diwan RK. Unusual additional distal aponeurotic slips of biceps brachii: A rare variation. J Anat Soc India 2022;71:74-6

How to cite this URL:
Singh R, Singh P, Verma R, Diwan RK. Unusual additional distal aponeurotic slips of biceps brachii: A rare variation. J Anat Soc India [serial online] 2022 [cited 2023 Mar 28];71:74-6. Available from: https://www.jasi.org.in/text.asp?2022/71/1/74/339883

Introduction

Biceps brachii muscle is one of the flexor groups of muscle in the anterior compartment of arm showing wide anatomical variation both pertaining to its origin and insertion. Although there is ample literature on variant origin of biceps brachii, documentation of anatomical variation of biceps brachii muscle related to the manner of its insertion is minimally reported.^[1] Biceps brachii muscle derives its name from its two proximally attached heads, the short and long head both originating from the scapula. The two heads join to form a single muscle belly distally that ends in a flattened tendon which get attached to radial tuberosity. The tendon has a broad medial expansion, the bicipital aponeurosis, that descends medially across the brachial artery to fuse with deep fascia over the origins of the flexor muscles of the arm.^[2] The biceps is basically a powerful supinator, especially in rapid and resisted movements of the forearm. It is also flexor of the elbow joint. These functions of muscle are executed by its attachment at the radial tuberosity as well as by bicipital aponeurosis that performs the function of drawing the posterior border of the ulna medially during supination of the forearm, thus stabilizing the distal tendon of biceps brachii.^[1] Bicipital aponeurosis also imparts protection to the brachial artery and median nerve running underneath.^[3] There was a study mentioning tendinous slip from bicipital aponeurosis giving extension to both pronator teres and flexor carpi ulnaris.^[4] In another study, accessory tendon was noted which was an extension from the lateral side of fleshy belly of the muscle on its lower third and get inserted distal to insertion of common tendon.^[5] The present case study drew our attention as we observed accessory aponeurotic slip arising from the muscle belly of biceps brachii and bicipital aponeurosis as well, lying over the neurovascular structures present in cubital fossa of the right arm. This type of variation may alter the kinematics of biceps brachii or may lead to neurovascular compression syndrome.

Case Report

During routine dissection for the undergraduate medical students in Anatomy Department at King George's Medical University, Uttar Pradesh, Lucknow, India, we came across variation in the insertion pattern of biceps brachii muscle on the right arm of 55-year-old embalmed male cadaver. The origin of biceps brachii was normal and was inserted normally on radial tuberosity, and to the antebrachial fascia of the forearm through bicipital aponeurosis. Apart from this usual insertion, three accessory aponeurotic slips were found. Two slips were arising from the lateral most part of bicipital aponeurosis traversing across the cubital fossa superficial to the brachial artery and median nerve [Figure 1]. The medial slip courses superficial to the proximal part of radial artery and superficial branch of radial nerve and get attached to the deep fascia covering the pronator teres while the lateral slip get attached to fascial covering of brachioradialis muscles [Figure 2]. Third accessory aponeurotic slip arises from the lateral side of biceps brachii muscle belly was 10 cm in length arising 7 cm proximal to the lateral epicondyle, coursing downward superficial to the musculocutaneous nerve and was attached to deep fascia covering the lateral border of brachioradialis and extensor carpi radialis longus muscle 3 cm below the lateral epicondyle [Figure 3].

Figure 1: Right cubital fossa showing tendon of Biceps Brachii (BT) muscle and 1^st and 2^nd additional aponeurotic slips arising from the lateral most part of bicipital aponeurosis (BA) traversing across the cubital fossa and get merged with pronator teres and brachioradialis muscles respectively.

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Figure 2: Right cubital fossa and upper part of front of forearm showing the medial slip (1^st) courses superficial to the proximal part of radial artery (RA) and superficial branch of radial nerve (SBRN)

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Figure 3: Lower part of front of right arm showing third (3^rd) accessory aponeurotic slip arises from the lateral side of biceps brachii muscle (BB) belly, coursing downward superficial to the musculocutaneous nerve (MCN) and was attached to deep fascia covering the lateral border of brachioradialis

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Discussion

Variation in the proximal end of biceps brachii is very well recorded in literature, but unusual insertion pattern of biceps brachii muscle is rarely documented and that too accessory aponeurotic slip is further rare.^[6] Limbs begins to develop by the end of the 4^th week, with the activation of mesenchymal cells in somatic lateral mesoderm. Mesenchymal cells at the posterior margin of the limb bud form an important signaling center in the limb development.^[7] Variation of muscle patterns may be result of altered signaling or stimulus between mesenchymal cells. The variant accessory tendinous slip from biceps brachii muscle is said to be the remnant of various muscular or tendinous slips from the distal end of the muscle during the development of fetus in utero.^[8]

Variant biceps brachii muscle was reported which gives an abnormal muscle fasciculus from its medial side and continued down as narrow tendinous slip which further subdivided into lateral and medial slips. The lateral slip cross the cubital fossa superficial to the brachial artery and median nerve and get merged with facial covering of flexor carpi ulnaris while the medial slip run deep to the brachial artery and median nerve and get attached to medial supracondylar ridge of humerus.^[9] In another cadaveric study, biceps brachii of the left arm was founded to be inserted on the posterior part of radial tuberosity, both by a common tendon and an accessory tendon. This accessory tendon was an extension from the lateral side of fleshy belly of muscle on its lower third and get inserted distal to insertion of common tendon.^[5] Bicipital aponeurosis was reported to had two slips, i.e., medial and lateral. Medial slip gave origin to some fibers of pronator teres and flexor carpi radialis and the lateral slip gave origin to some fibers of brachioradialis.^[10] Three cases of variant bicipital aponeurosis were reported. In the first case, fibers originated from bicipital aponeurosis and get merged with flexor carpi radialis muscle. In the second case, two tendinous slips arising from medial and lateral most fibers of biceps brachii, medial one passes deep to the brachial artery before merging with bicipital aponeurosis while lateral one merge directly. The third variant was third head of biceps brachii that originated from the superomedial aspect of brachialis and get merged with bicipital aponeurosis.^[3] In another study, accessory tendo-aponeurotic slip of bicep brachii was reported which traverses across the forearm, superficial to the proximal part of radial artery as well as the superficial branch of radial nerve, possibly compressing them.^[5] In the present study, we observed three accessory aponeurotic slips, two from the lateral aspect of bicipital aponeurosis and third from the lateral aspect of muscle belly of biceps brachii. The aponeurotic slips arising from the bicipital aponeurosis traverses across the cubital fossa, superficial to neurovascular bundle and get attached to fascia covering the pronator teres and brachioradialis. The third aponeurotic slip arising from the muscle belly of biceps brachii traverses downward superficial to musculocutaneous nerve and get attached to fascia covering the brachioradialis.

These extra slips may affect the kinematics of biceps brachii muscle, thus altering the movements at elbow joint and superior radio ulnar joint. In addition, these slips may produce paresthesia and ischemic symptoms due to the compression of neurovascular bundle.^[11] Hence, information on such variation adds to differential diagnosis of variety of clinical symptoms of neurovascular syndrome. The presence of accessory aponeurotic slips may end up in iatrogenic injuries during surgeries around elbow and may create problem for orthopedician because of unpredictable displacement of bone fragments after fracture.^[5] Plastic surgeons may find difficulty in elevation and transfer of lateral arm flaps due to the presence of additional aponeurotic slip on the lateral side of biceps brachii muscle.^[12]

The mode of insertion of biceps brachii muscle is accountable for its efficient function that is supination and flexion of the forearm. Clinician should also have idea of such slips as it may be one of the reasons of neurovascular compression syndrome. The facts regarding unusual variation in the insertion pattern may help orthopedician to give better outcome while repairing or reconstructing tendon surgeries during avulsion and plastic surgeons while doing the lateral arm flap elevation and transfer.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1.	Eames MH, Bain GI, Fogg QA, van Riet RP. Distal biceps tendon anatomy: A cadaveric study. J Bone Joint Surg Am 2007;89:1044-9.
2.	Standring S. Gray's Anatomy. The Anatomical Basis of Clinical Practice. 41^st ed. UK: Elsevier; 2016.
3.	Deopujari R, Quadir N, Athavale S, Gajbhiye V, Kotgirwar S. Variant bicipital aponeurosis: A cadaveric study. Peoples J Sci Res 2014;7:43-6.
4.	Bhat Kumar MR, Kulakarni V, Gupta C. Additional muscle slips from the bicipital aponeurosis and a long communicating branch between the musculocutaneous nerve and median nerve. Int J Anat Var 2012;5:41-3.
5.	Daimi SR, Siddiqui AU, Wabale RN, Gandhi KB. Additional tendinous insertion of biceps brachii: A case report. Paravara Med Rev 2010;2:16-8.
6.	Sanchita R, Mira D, Pandey M, Gupta HD. An aberrant tendo-aponeurotic extension of biceps brachii muscle a possible factor for neurovascular compression in the antibrachium. Int J Anat Var 2014;7:91-2.
7.	Moore KL, Persaud TV, Torchia MG. The Developing Human Clinically Oriented Embryology. 9^th ed. India: Saunders an Imprint of Elsevier; 2013.
8.	Bryce TH. Myology. The muscle and fascia of upper arm-M biceps brachii. In: Sharpey SE, Symington J, Bryce TH, editors. Quain's Elements of Anatomy. 11^th ed. London: Longmans, Green & Co; 1923. p. 121.
9.	Paval J, Mathew JG. A rare variation of the biceps brachii muscle. Indian J Plast Surg 2006;3937:65-7.
10.	Nayak SB, Swamy RS, Shetty P, Maloor PA, Dsouza MR. Bifurcated bicipital aponeurosis giving origin to flexor and extensor muscles of the forearm – A case report. J Clin Diagn Res 2016;10:D01-2.
11.	Warner JJ, Paletta GA, Warren RF. Accessory head of the biceps brachii. Case report demonstrating clinical relevance. Clin Orthop Relat Res 1992;280:179-81.
12.	Sawant SP, Shaikh ST, More RM. A case report on the median nerve passing through the supernumerary head of the biceps brachii muscle. Int J Anal Pharm Biomed Sci 2012;1:(2).