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Indian Journal of Plastic Surgery, Vol. 38, No. 2, July-December, 2005, pp. 164-166 Brief Report Unilateral appearance of a chondro-epitrochlearis muscle-a case report Jaijesh P Department of Anatomy, Melaka Manipal Medical College, Manipal - 576104, Karnataka, India Correspondence Address:Dr. Paval Jaijesh, Melaka Manipal Medical College, Manipal – 576104, Karnataka, India. E-mail: jaijesh@yahoo.co.in Code Number: pl05036 Abstract Variant muscle slips from pectoralis major muscle are rare. Among these, the muscle chondro-epitrochlearis is a very rare muscular anomaly. Here, in this report, we describe a similar muscle which had an origin from the lower ribs along with the lower fibres of the pectoralis major muscle, arched across the axilla, and then inserted to the medial epicondyle of humerus. In this report we present a review of literature on this muscle. We also discuss the clinical significance of this muscle since the knowledge of this muscle is important in the differential diagnosis of ulnar nerve entrapment.Keywords: Chondro-epitrochlearis, Pectoralis major muscle, Ulnar artery Introduction Chondro-epitrochlearis is a very rare muscular anomaly. This is the first instance of this anomalous muscle we have encountered over a period of 25 years in our dissection hall. Bergman[1] describes this anomaly as a muscular slip which arises from one or more ribs, crosses the axilla and inserts into the medial intermuscular septum or medial epicondyle of the humerus. According to Wood[2] this muscle should be described as 'epigastric slips' represented by the detached slips from the inferior border of pectoralis major that insert on the humerus on the deep surface of its own tendon of insertion. Landry et al[3] have described the phylogenetic significance of such a variant muscle and Spinner et al .[4] have emphasized its clinical relevance.Case report During the routine dissection for the medical students we found this muscle unilaterally in a male cadaver. The muscle had an origin from the sixth costal cartilage near the costo-chondral junction. The muscle continued along the inferolateral border of the pectoralis major muscle. Upon reaching the axilla, this muscle arched towards the arm, formed a narrow tendon, crossed brachial artery and inserted to the superior surface of the medial epicondyle of the humerus. In its course towards the medial epicondyle, the muscle was found plastered to the medial head of the triceps brachii muscle. The ulnar nerve was found between the tendon of this muscle and medial head of triceps muscle. [Figure - 1] [Figure - 2]Discussion The muscle described in the present report is similar to that described by Perrin.[5] He also identified a muscle which terminated opposite the middle of the anterior aspect of the arm, which had descended from the capsule of the shoulder joint anterior to the tendon of the long head of biceps brachii muscle. Bregman et al .[1] and Anson[6] found a similar muscle in 12 to 20 % bodies. But considering the current literature, this kind of high prevalence of this anomalous muscle is not well established. Although the tendinous insertion of this muscle is the common one, Bryce[7] reported a fleshy insertion of this muscle in the medial intermuscular septum 2 inches above the medial epicondyle. Macalister[8] in his work on human muscular variations makes a reference to a digastric chondro-epitrochlearis. Nerve supply of this muscle is mostly derived from the pectoral branches of the brachial plexus. Bryce[7] and laundry[3] reported about the nerve supply of this muscle which derived from an anterior division of the brachial plexus and believe that this may be due to its embryological origin from the ventral muscle mass. A dual innervation was reported by Spinner et al ,[4] one from the Y- junction of the medial and lateral roots of the median nerve, and the other from the branch of the medial pectoral nerve. In the present case the muscle is innervated by the medial pectoral nerve. Chiba et al[9] suggested that the chondro-epitrochlearis is almost always associated with the axillary arch muscle, which itself occurs in 7 to 13% of the population. Voto and Weiner[10] reported a clinical case of an infant with a contracture of the chondro-epitrochlearis in whom the axillary arch muscle was absent. According to Landry[3] and Bergman[11] the presence of an anomalous chondro-epitrochlearis is invariably associated with the absence of the usual twist of tendon of insertion of pectoralis major. But in the present case, pectoralis muscle had the usual twisted insertion and also the axillary arch muscle was absent. Landry[3] reported that chondro-epitrochlearis is an atavistic anomaly which demonstrates the distal extent of the insertion in ancestral forms. The chondro-epitrochlearis muscle has been found at autopsy in infants with chromosomal defects, namely, trisomy 13 with a D/D translocation and trisomy 18.[12] In the present case, the ulnar nerve was found entrapped between the tendon of chondro-epitrochlearis and the medial head of triceps brachii. This situation of ulnar nerve entrapment will be mimicking the manifestations of cubital tunnel syndrome or the situation where the struther's ligament is involved. To conclude, this muscle anomaly is clinically important for its potential to cause cosmetic defects, to restrict abduction of the arm and also for the differential diagnosis of the compressive neuropathy from the ulnar nerve entrapment. References
Copyright 2005 - Indian Journal of Plastic Surgery The following images related to this document are available:Photo images[pl05036f1.jpg] [pl05036f2.jpg] |
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