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Third head of biceps brachii: A rare occurrence in the Indian population
ARTICLE IN PRESS Ann Anat 188 (2006) 159—161
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Third head of biceps brachii: A rare occurrence in the Indian population Soubhagya R. Nayak, Latha V. Prabhu, R. Sivanandan Department of Anatomy, Centre for Basic Sciences, Kasturba Medical College, Bejai, Mangalore-575004, Karnataka, India Received 3 August 2005; accepted 10 October 2005
KEYWORDS Biceps brachii; Third head; Morphology
Summary A study of the incidence of the third head of the biceps brachii (caput accessorium) was carried out in the Department of Anatomy, Kasturba Medical College, Mangalore, India. The observations were made during routine cadaveric dissections to teach the undergraduate students. Forty-eight cadavers were included in the study. The occurrence of this anomaly and its morphology are discussed. & 2005 Elsevier GmbH. All rights reserved.
Introduction The biceps brachii muscle is classically described as a two-headed muscle that originates proximally, with a long head from the supraglenoid tubercle and short head from the coracoid process of the scapula. Distally these heads join to form a common tendon, that gets inserted to the posterior aspect of the radial tuberosity (Gray, 1973), mainly contributing to the flexion and supination of the forearm. Some aponeurotic and tendinous fibers gain insertion into the bicipital aponeurosis. Occasionally, humans possess a third head of biceps brachii, which is a common occurrence in other mammals (Dobson, 1881; Primrose, 1899; Sonntag, Corresponding author. Tel.: +91 824 2211746;
fax: +91 824 2421283. E-mail address: [email protected] (S.R. Nayak).
1923). Testut (1902) has described the biceps brachii muscle as one of the muscles with most frequent anatomic variations. In the human, the occasional presence of the third head has been reported with varying frequency according to the population; i.e., Chinese 8%, European white 10%, African black 12%, Japanese 18%, South African blacks 20.5%, South African whites 8.3%, and Colombian 37.5% (Bergman et al., 1984; Asvat et al., 1993; Rincon et al., 2002). There are no reports on the frequency of occurrence of the third head in the Indian population. The third head of biceps brachii variations may present as a group of accessory fascicles arising from the coracoid process, pectoralis major tendon, head of the humerus, articular capsule of the humerus or from the humerus itself (Sargon et al., 1996). The association of the third head with this type may cause unusual bone displacement,
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ARTICLE IN PRESS 160
S.R. Nayak et al.
subsequent to fracture, such variations have relevance in surgical procedures (Swieter and Carmichael, 1980).
Material and methods During routine cadaveric dissections of 30 male and 18 female cadavers upper limbs were examined for the incidence, origin, insertion, and innervation of the third head of biceps brachii. Upper limbs were dissected, by a longitudinal incision at the anterior aspect of the arm from the level of the acromion to the elbow junction. Then the skin, subcutaneous fat, and fascia are removed to expose the biceps brachii. While doing so, the nerve supply to the biceps brachii was carefully observed for any variations. The occurrence of the third head of the biceps brachii is very rare and even less in comparison to other populations.
Results Out of 48 subjects studied, both limbs of one of the male cadavers were found to have a threeheaded biceps brachii muscle. On the right side the third head of the biceps brachii originated from the antero-medial aspect of the humerus, just distal to the insertion of the coracobrachialis. On the same side a muscular slip arising from the long head of biceps brachii joined the brachioradialis muscle, the radial nerve was observed to pass under this slip. On the left side the third head of the biceps brachii originated from the humeral shaft and upper part of the brachialis muscle. It was almost the size of short head. On both sides the tendon of third heads joined the tendon of biceps brachii to be inserted to the radial tuberosity. The biceps with its third head was innervated by the musculocutaneous nerve and supplied by the small branches of brachial artery. Embryologically, this suggests that third head of biceps brachii is a muscle of the anterior compartment of the arm (Figs. 1–3). The variant was present in one male (3.33%, n ¼ 30), and none of the females (0%, n ¼ 18), bilaterally (2.08%, n ¼ 48). The incidence was merely 2.08%, n ¼ 48.
Discussion Gray (1973) has reported the incidence of third head of biceps brachii in as much as 10%, in his studies, this agrees with the observations of
Figure 1. Anterior view of right arm showing muscles of the anterior compartment of arm and the additional third head.
Figure 2. Antero-medial view of left arm showing the three heads of biceps brachii.
Bergman et al. (1984) in white Europeans, and a 12% incidence in black Africans. Asvat et al. (1993) reported an incidence of 21.5% in his study group for blacks, 8.3% for whites, and correlated it to the results by Greig et al. (1952). Incidences of bilaterally symmetric variations are reported in 60% of the South African population (Asvat et al., 1993), in 12.5% of the Colombian (Rincon et al.,
ARTICLE IN PRESS Third head of biceps brachii
161 compared to the females (Rincon et al., 2002; Bergman et al., 1984; Asvat et al., 1993). The relevance of all these observations in the clinical scenario is related to some physio-pathological consideration.
References
Figure 3. Lateral view of right arm showing the accessory slip to coracobrachialis.
2002), and in 2.3% of the European white population (Bergman et al., 1984). The medial brachial origin may contribute to pronation of the forearm irrespective of shoulder joint position (Bergman et al., 1984). In addition to elbow flexion independent of shoulder joint position, the third head of biceps brachii may enhance the strength of elbow flexion (Swieter and Carmichael, 1980).It is not known yet, whether or not, the third head of biceps brachii means a specific functional adaptation of population characterized for continuous moderate physical activity. Kopuz et al. (1999) attribute the appearance of this variant to evolutionary and/or racial trends. Notably, humans in contrast to other primates, lack the long head of coracobrachialis (Wood, 1870; Primrose, 1899; Sonntag, 1923, 1924). In those cases in which the third head arises from the midshaft, at site of insertion of the long head of coracobrachialis, the ancestral hominoid condition (Wood, 1870; Primrose, 1899; Sonntag, 1923, 1924). The innervation and vascularisation to the third head of the biceps brachii agrees with normal embroyologic development of the related dermatomes and myotomes as reported by other authors (Testut, 1902; Gray, 1973; Asvat et al., 1993). The only puzzling observation was that the occurrence was higher in case of males when
Asvat, R., Candler, P., Sarmiento, E.E., 1993. High incidence of third head of biceps brachii in South African populations. J. Anat. 182, 101–104. Bergman, R.A., Thompson, S.A., Afifi, A.K., 1984. Catalogue of Human Variation. Urban and Schwarzenberg, Munich, pp. 27–30. Dobson, G.E., 1881. Notes on the anatomy of cercopithecus callithichus. Proc. Zool. Soc. London, 812–818. Gray, H., 1973. Anatomy of Human Body, 29th American ed. Lea and Febiger, Philadelphia, pp. 488–499. Greig, H.W., Anson, B.J., Budinger, J.M., 1952. Variations in the form and attachments of the biceps brachii muscle. Q. Bill. North Western Med. School 26, 241–244. Kopuz, C., Sancack, B., Ozbenlis, 1999. On the incidence of the third head of biceps brachii in Turkish neonates and adults. Acta Anat. Nippon. 74 (3), 301–305. Primrose, A., 1899. The anatomy of orang-utang (Simia satyrus). Transcripts R. Soc. Canadian Institute 6, 507–598. Rincon, F., Rodriquez, I.Z., Sanchez, A., et al., 2002. The anatomic characteristics of the third head of biceps brachii muscle in Colombian population. Rev. Chil. Anat. 20 (2), 197–200. Sargon, M.F., Tunacali, D., Celik, H.H., 1996. An unusual origin for the accessory head of biceps brachii muscle. Clin. Anat. 9 (3), 160–162. Sonntag, C.F., 1923. On the anatomy, physiology and pathology of the chimpanzee. Proc. Zool. Soc. London 24, 349–449. Swieter, M.G., Carmichael, S.W., 1980. Bilateral threeheaded biceps brachii muscle. Anat. Anz. 148 (4), 346–349. Testut, L., 1902. Tretado de Anatomica Humana. Salvat, Barcelona, p. 1022. Wood, J., 1870. On a group of varieties of the muscle of the human neck, shoulder and chest. Philos. Trans. R. Soc. London 160, 83–116.
www.elsevier.de/aanat
Third head of biceps brachii: A rare occurrence in the Indian population Soubhagya R. Nayak, Latha V. Prabhu, R. Sivanandan Department of Anatomy, Centre for Basic Sciences, Kasturba Medical College, Bejai, Mangalore-575004, Karnataka, India Received 3 August 2005; accepted 10 October 2005
KEYWORDS Biceps brachii; Third head; Morphology
Summary A study of the incidence of the third head of the biceps brachii (caput accessorium) was carried out in the Department of Anatomy, Kasturba Medical College, Mangalore, India. The observations were made during routine cadaveric dissections to teach the undergraduate students. Forty-eight cadavers were included in the study. The occurrence of this anomaly and its morphology are discussed. & 2005 Elsevier GmbH. All rights reserved.
Introduction The biceps brachii muscle is classically described as a two-headed muscle that originates proximally, with a long head from the supraglenoid tubercle and short head from the coracoid process of the scapula. Distally these heads join to form a common tendon, that gets inserted to the posterior aspect of the radial tuberosity (Gray, 1973), mainly contributing to the flexion and supination of the forearm. Some aponeurotic and tendinous fibers gain insertion into the bicipital aponeurosis. Occasionally, humans possess a third head of biceps brachii, which is a common occurrence in other mammals (Dobson, 1881; Primrose, 1899; Sonntag, Corresponding author. Tel.: +91 824 2211746;
fax: +91 824 2421283. E-mail address: [email protected] (S.R. Nayak).
1923). Testut (1902) has described the biceps brachii muscle as one of the muscles with most frequent anatomic variations. In the human, the occasional presence of the third head has been reported with varying frequency according to the population; i.e., Chinese 8%, European white 10%, African black 12%, Japanese 18%, South African blacks 20.5%, South African whites 8.3%, and Colombian 37.5% (Bergman et al., 1984; Asvat et al., 1993; Rincon et al., 2002). There are no reports on the frequency of occurrence of the third head in the Indian population. The third head of biceps brachii variations may present as a group of accessory fascicles arising from the coracoid process, pectoralis major tendon, head of the humerus, articular capsule of the humerus or from the humerus itself (Sargon et al., 1996). The association of the third head with this type may cause unusual bone displacement,
0940-9602/$ - see front matter & 2005 Elsevier GmbH. All rights reserved. doi:10.1016/j.aanat.2005.10.004
ARTICLE IN PRESS 160
S.R. Nayak et al.
subsequent to fracture, such variations have relevance in surgical procedures (Swieter and Carmichael, 1980).
Material and methods During routine cadaveric dissections of 30 male and 18 female cadavers upper limbs were examined for the incidence, origin, insertion, and innervation of the third head of biceps brachii. Upper limbs were dissected, by a longitudinal incision at the anterior aspect of the arm from the level of the acromion to the elbow junction. Then the skin, subcutaneous fat, and fascia are removed to expose the biceps brachii. While doing so, the nerve supply to the biceps brachii was carefully observed for any variations. The occurrence of the third head of the biceps brachii is very rare and even less in comparison to other populations.
Results Out of 48 subjects studied, both limbs of one of the male cadavers were found to have a threeheaded biceps brachii muscle. On the right side the third head of the biceps brachii originated from the antero-medial aspect of the humerus, just distal to the insertion of the coracobrachialis. On the same side a muscular slip arising from the long head of biceps brachii joined the brachioradialis muscle, the radial nerve was observed to pass under this slip. On the left side the third head of the biceps brachii originated from the humeral shaft and upper part of the brachialis muscle. It was almost the size of short head. On both sides the tendon of third heads joined the tendon of biceps brachii to be inserted to the radial tuberosity. The biceps with its third head was innervated by the musculocutaneous nerve and supplied by the small branches of brachial artery. Embryologically, this suggests that third head of biceps brachii is a muscle of the anterior compartment of the arm (Figs. 1–3). The variant was present in one male (3.33%, n ¼ 30), and none of the females (0%, n ¼ 18), bilaterally (2.08%, n ¼ 48). The incidence was merely 2.08%, n ¼ 48.
Discussion Gray (1973) has reported the incidence of third head of biceps brachii in as much as 10%, in his studies, this agrees with the observations of
Figure 1. Anterior view of right arm showing muscles of the anterior compartment of arm and the additional third head.
Figure 2. Antero-medial view of left arm showing the three heads of biceps brachii.
Bergman et al. (1984) in white Europeans, and a 12% incidence in black Africans. Asvat et al. (1993) reported an incidence of 21.5% in his study group for blacks, 8.3% for whites, and correlated it to the results by Greig et al. (1952). Incidences of bilaterally symmetric variations are reported in 60% of the South African population (Asvat et al., 1993), in 12.5% of the Colombian (Rincon et al.,
ARTICLE IN PRESS Third head of biceps brachii
161 compared to the females (Rincon et al., 2002; Bergman et al., 1984; Asvat et al., 1993). The relevance of all these observations in the clinical scenario is related to some physio-pathological consideration.
References
Figure 3. Lateral view of right arm showing the accessory slip to coracobrachialis.
2002), and in 2.3% of the European white population (Bergman et al., 1984). The medial brachial origin may contribute to pronation of the forearm irrespective of shoulder joint position (Bergman et al., 1984). In addition to elbow flexion independent of shoulder joint position, the third head of biceps brachii may enhance the strength of elbow flexion (Swieter and Carmichael, 1980).It is not known yet, whether or not, the third head of biceps brachii means a specific functional adaptation of population characterized for continuous moderate physical activity. Kopuz et al. (1999) attribute the appearance of this variant to evolutionary and/or racial trends. Notably, humans in contrast to other primates, lack the long head of coracobrachialis (Wood, 1870; Primrose, 1899; Sonntag, 1923, 1924). In those cases in which the third head arises from the midshaft, at site of insertion of the long head of coracobrachialis, the ancestral hominoid condition (Wood, 1870; Primrose, 1899; Sonntag, 1923, 1924). The innervation and vascularisation to the third head of the biceps brachii agrees with normal embroyologic development of the related dermatomes and myotomes as reported by other authors (Testut, 1902; Gray, 1973; Asvat et al., 1993). The only puzzling observation was that the occurrence was higher in case of males when
Asvat, R., Candler, P., Sarmiento, E.E., 1993. High incidence of third head of biceps brachii in South African populations. J. Anat. 182, 101–104. Bergman, R.A., Thompson, S.A., Afifi, A.K., 1984. Catalogue of Human Variation. Urban and Schwarzenberg, Munich, pp. 27–30. Dobson, G.E., 1881. Notes on the anatomy of cercopithecus callithichus. Proc. Zool. Soc. London, 812–818. Gray, H., 1973. Anatomy of Human Body, 29th American ed. Lea and Febiger, Philadelphia, pp. 488–499. Greig, H.W., Anson, B.J., Budinger, J.M., 1952. Variations in the form and attachments of the biceps brachii muscle. Q. Bill. North Western Med. School 26, 241–244. Kopuz, C., Sancack, B., Ozbenlis, 1999. On the incidence of the third head of biceps brachii in Turkish neonates and adults. Acta Anat. Nippon. 74 (3), 301–305. Primrose, A., 1899. The anatomy of orang-utang (Simia satyrus). Transcripts R. Soc. Canadian Institute 6, 507–598. Rincon, F., Rodriquez, I.Z., Sanchez, A., et al., 2002. The anatomic characteristics of the third head of biceps brachii muscle in Colombian population. Rev. Chil. Anat. 20 (2), 197–200. Sargon, M.F., Tunacali, D., Celik, H.H., 1996. An unusual origin for the accessory head of biceps brachii muscle. Clin. Anat. 9 (3), 160–162. Sonntag, C.F., 1923. On the anatomy, physiology and pathology of the chimpanzee. Proc. Zool. Soc. London 24, 349–449. Swieter, M.G., Carmichael, S.W., 1980. Bilateral threeheaded biceps brachii muscle. Anat. Anz. 148 (4), 346–349. Testut, L., 1902. Tretado de Anatomica Humana. Salvat, Barcelona, p. 1022. Wood, J., 1870. On a group of varieties of the muscle of the human neck, shoulder and chest. Philos. Trans. R. Soc. London 160, 83–116.