A Rare Anomaly of the Pectoralis Major? the Chondroepitrochlearis

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1 Okajimas Folia Anat. Jpn., 60 (2-3): , August 1983 Case Report A Rare Anomaly of the Pectoralis Major? the Chondroepitrochlearis By Shoji CHIBA, Takao SUZUKI and Tatsuo KASAI Second Department of Anatomy, Hirosaki University Medical School Hirosaki 036, Japan?Received for Publication, April 18, Key words: Chondroepitrochlearis, Pectoralis major, Anomaly Summary: The chondroepitrochlearis was found in the left upper extremity of a 92-year-old Japanese male. This represents the second report of the anomaly in Japan after Yokoh ('33). The pars abdominalis of the pectoralis major consisted of two slender muscle slips, A and B, and after arising from the lower costal cartilages as normal, they took a somewhat horizontal course towards the axilla, being separated from the parent muscle. Slip A was attached to the aponeurotic sheet deep to the insertion of the pectoralis major and abruptly turned its course downwards along the humerus. It then continued to the characteristic long slender tendon and finally inserted onto the medial epicondyle of the humerus. Slip B passed caudal to slip A, and in the axilla it crossed the muscular arch which arose from the latissimus dorsi. The most caudal pectoral nerve arising from the ansa pectoralis supplied both the muscle slips together with the muscular arch of the axilla. According to Saar ('03), the insertion of the pectoral muscles in ungulates sometimes migrates distalwards along the humerus and is onto the medial epicondyle of the humerus. The aberrant muscle under discussion here would thus be a phylogenetic recapitulation of this condition. Tobler ('02) and Ruge ('14) have also suggested that the chondroepitrochlearis in man would be derived from the panniculus carnosus of lower mammals, and this was demonstrated by the present authors from the nerve supply. Crossing of the separated abdominal part of the pectoralis major with the muscular arch of the axilla was a noticeable finding of the anomaly, and the authors consider that it would be closely related genetically with the appearance of this anomaly. The chondroepitrochlearis is a rare anomaly of the pectoralis major and only a few cases have been reported in the literature. The characteristic feature of this anomaly is an abnormally elongated slender tendon which extends from the insertion of the pectoralis major to the medial epicondyle of the humerus. During the course of examination of the muscular arch of the axilla, the authors encountered this anomaly in the left upper extremity of a 92-year-old Japanese male. Findings Abnormal findings were not observed in the clavicular and sternocostal parts of the pectoralis major or in the pectoralis minor. Muscle twisting of the inferior part of the pectoralis major was almost normally observed forming the so-called pectoral pouch (Pectoralis-tasche) which will be 175

2 176 S. Chiba et al. Fig. 1. Ventral view of the left upper arm, showing the chondroepitrochlearis of the present case. At the lower border of insertion of the pectoralis major, the aberrant muscle slip A continued to the tendinous sheet, to which the muscular arch of the axilla was connected. The characteristic long slender tendon arose from the sheet and ran distalwards along the medial side of the biceps brachii under the deep fascia of the arm. Almost normal muscle twisting of the inferior part of the pectoralis major was observed. The other aberrant muscle slip B crossed the muscular arch. Fig. 2 The characteristic long slender tendon of the present case which extended from the axilla to the medial epicondyle of the humerus. The origin of the pectoral muscles has been cut together with the aberrant slips (A, B) and the muscular arch of the axilla, and they have been reflected laterally to show the contents of the axilla. The inferior lateral superficial branchial artery was present, and separated the tendon under discussion from the medial brachial intermuscular septum. The asterisk (*) shows the connection between the ulnar and the mdial antebrachial cuataneous nerves.

3 A Rare Anomaly of The Pectoralis Major 177

4 178 S. Chiba et al. discussed below. The abdominal part of the pectoralis major (Pars abdominalis) consisted of two muscle slips, A and B, both of which arose commonly from the lower costal cartilages, slip A being superficial to B. As they passed laterally towards the axilla, they took a somewhat horizontal course, being separated from the lower border of the sternocostal part of the pectoralis major. At the same time, both slips were kept apart from each other, A being cranial to B. In the axilla, slip A was connected with the aponeurotic sheet and, abruptly turning its course downwards along the arm, continued to the characteristic slender tendon which is described below. The aponeurotic sheet to which not only muscle slip A but also the muscular arch of the axilla was attached, was deep to the insertion of the pectoralis major, and further it was connected with the overlying fascia of the short head of the biceps brachii and the coracobrachialis. Caudal slip B passed in an almost horizontal direction towards the axilla, and after crossing the root of the muscular arch of the axilla inserted onto the superficial part of the arch. The muscular arch of the axilla originated from the lateral border of the latissimus dorsi and, after being crossed by slip B, passed cranioventralwards and connected with the aponeurotic sheet described above (Fig. 1). The long slender tendon, one of the most characteristic findings in this case, originated from the aponeurotic sheet and passed downwards on the arm obliquely and medially. It was covered with the deep fascia of the arm, and crossed superficial to the median nerve and the inferior lateral superficial brachial artery at about the middle one-third of the arm. It then passed deep to the basilic vein and the medial antebrachial cutaneous nerve. At the lower end of the arm, it was connected with the medial intermuscular septum of the arm and finally inserted onto the medial epicondyle of the humerus. The total length of this tendon was about 200 mm, and its width in the middle of the arm was 2-3 mm (Fig. 2). The most caudal branch of the ansa pectoralis (the caudal pectoral nerve) was divided into two, passing behind the pectoralis minor, and supplied muscle slip B and the muscular arch. Another small branch arising from the supplying nerve to the dorsal lamina of the reflected part of the pectoralis major supplied muscle slip A. Both the nerves passed around the inferior margin of the pectoralis minor (Figs. 3 and 4). No other remarkable abnormalities were found in this case. Discussion Only a few cases of this anomaly have been described. As shown in the table, Tobler ('02), Saar ('03, two cases), Bose ('04, three cases), Eisler ('12), Steinbach ('22), Yokoh ('33), Tischendorf ('49) and Landry ('58) have reported it. Among these, Steinbach referred to several other cases, most of which were described in the last century, so that 20 cases have been published in total. In Japan, the present case represents the second one after Yokoh. The long slender tendon extending from the insertion of the pectoralis major to the medial epicondyle of the humerus was common to all the reported cases, except the one of Eisler in which the tendon terminated in the deep fascia of the arm. According to Saar, Bose and Tischendorf, the insertion of the pectoralis major in lower mammals has been said to extend sometimes from the greater tubercle of the humerus to the medial epicondyle. The chondroepitrochlearis would thus be a phylogenetic recapitulation of this condition. Saar examined the pectoral muscles

5 A Rare Anomaly of The Pectoralis Major 179 Fig. 3. Nerve distribution to the pectorales major and minor and also to the abe A rrant muscle slips and B together with the muscular arch of the axilla. The most caudally originating nerve from the ansa pectoralis (P1, P2, P3) supplied muscle slip B and the muscular arch. The long slender tendon extended from the tendinous sheet into which muscle slip A and the muscular arch were attached. This is a dorsal view of the specimen, and the positional relation between the pectoral nerves and muscles can be more clearly understood by reference to Fig. 4.

6 180 S. Chiba et a/. Fig. 4. Schematic diagram of the nerve distribution to the pectoral muscles and the muscular arch of the axilla. The ansa pectoralis was formed by three nerve roots (P1, P2, P3). P1 originated from C8 and Ti, and both P2 and P3 from C7. In this schema, the pectoral muscles have been sectioned longitudinally. of ungulates (sheep, goat, deer and pig) and noted that the insertion of the pectoral muscles of these animals migrated distalwards along the humerus and especially in the former two animals, it was attached to the medial epicondyle of the humerus. He also stated that in these animals the pectoral muscles consisted of the sternohumerales superficialis and profundus. The former originated from the anterior surface of the sternum at the level of the first costal cartilage and passed infero-laterally, while the latter was a wide muscle and arose from the 1st to 5th costal cartilages. Both the muscles combined together in the axilla and continued to a slender tendon to insert onto the medial epicondyle of the humerus. On the other hand, it has been said that the chondroepitrochlearis in man was derived from the most caudal part of the pectoralis major, the insertion of which was separated from the parent muscle. Wood (1866) and Perrin (1871) termed the separated muscle as mentioned above the epigastric slip and stated that it presented an incomplete form of the chondroepitrochlearis. According

7 A Rare Anomaly of The Pectoralis Major 181 to Tobler ('02) and Ruge ('10, '14), the separated muscle was none other than the pars abdominalis of the pectoralis major and this was also confirmed by the present authors from the nerve supply. As regards the nerve supply of this aberrant muscle, details were given only by Tobler ('02) and Tischendorf ('49), of whom the former described a common branch with that to the accompanying muscular arch of the axilla, and the latter a supplying nerve to the abdominal part of the pectoralis major. As is well known, the pectoralis major under normal conditions displays twisting near the insertion; that is, the caudally originating muscle fibers pass under the more cranially originating fibers to insert more proximally onto the humerus. It has therefore been said that in the anomaly under discussion, normal twisting of the pectoralis major is lacking. Eisler also stated the same, referring to the cases previously reported by others. In the present case, however, careful examination demonstrated that muscle twisting was almost normally observed and a pectoral pouch was present, whereas the most caudal part of the muscle continued to the slender tendon and was not concerned in the twisting. The muscular arch of the axilla being associated with this anomaly could not be neglected, since not only did it continue to the aponeurotic sheet from which the long slender tendon arose but it crossed the separated muscle slip of the pectoralis major. As seen from the table, of the 12 authors who reported this anomaly, 5 described the muscular arch in company with this anomaly, 5 did not mention it, and only Bose denied the presence of the arch in his two cases. Yokoh ('33) stated that the latissimo-condyloideus which arose from the latissimus dorsi and continued to the medial epicondyle of the humerus, was associated in his case. However, he probably misunderstood the nomenclature of this aberrant muscle, and it should be the muscular arch of the axilla, although he did not mention the supplying nerve. During the course of investigation of the muscular arch of the axilla, the present authors have sometimes observed a separation of the inferior part of the pectoralis major from the parent muscle, being associated with the muscular arch. In these cases, both the muscles crossed each other in the axilla, as observed in the present case. The authors refer to this as a crossing type of muscular arch and it was usually observed in the well-developed arch. As described in our previous report ('77), the authors found the muscular arch in 45 of 354 upper extremities, and in 7 of them they found the crossing type of arch. The present case was one of these cases. Ruge ('14) carried out an extensive study on the panniculus carnosus of mammals, and mentioned several atypical cases of the muscular arch in man, referring to Tobler ('02), Gehry ('03), Bose ('04), Bluntschli ('10) and Sicher ('11). In these cases, the inferior part of the pectoralis major was separated from the parent muscle and its insertion was shifted distalward along the humerus as far as the medial epicondyle. According to the illustrations quoted by Ruge, the insertion of the most caudal part of the pectoralis major was pulled distalwards along the humerus in company with the muscular arch, and therefore both the muscles were considered to have a genetically intimate relation with each other. Ruge ('14) also concluded that these aberrant muscles were derived from the panniculus carnosus of mammals. In the report of LeDouble (1897) and some textbooks of anatomy such as that of Cunnigham ('51), the definition of the chondroepitrochlearis is explained with a broad meaning, incorporating those cases inserting into the deep fascia of the arm, the medial intermuscular septum or the

8 182 S. Chiba et al. medial epicondyle of the humerus. One other problem is to distinguish the anomaly under discussion from the coracobrachialis longus. The insertion of the coracobrachialis is shifted distalwards and continues to the medial intermuscular septum of the arm. Thus, the two anomalies resemble each other in appearance, although the nerve supply should offer a key for resolving this problem. References 1) Bluntschli, H.: Uber die Beteiligung des Musculus latissimus dorsi an Achselbogenbildungen beim Menschen. Morph. Jahrb., 41: , ) Base.: Uber einige Muskelvarietaten, den Pectoralis major, Latissimus dorsi und Achselbogen betreffend. Morph. Jahrb., 32: , ) Brash, J. C.: Muscles of upper limb. Cunningham's text-book of anatomy. 9th ed., 479, Oxford Univ. Press, London, ) Eisler, P.: Muskeln der Brust. Die Muskeln des Stammes , Gustav Fischer, Jena, ) Gehry, K.: Neue BeitrAge zur Geschichte des Achselbogens des Menschen, eines Rudimentes des Panniculus carnosus des Mammalier. Morph. Jahrb., 31: , ) Kasai, T. and Chiba, S.: True nature of the muscular arch of the axilla and its nerve supply. Acta Anat. Nippon., 52: , (in Japanese) 7) Landry, S. 0.: The phylogenetic significance of the chondro-epitrochlearis muscle and its accompanying pectoral abnormalities. J. Anat., 92: 57-61, ) Le Double, A.-F.: Muscles des parois de la poitrine. Traite des variations du systeme musculaire de l'homme. Tome 1, , Schleicher Freres, Paris, ) Perrin, J. B.: Notes on some variations of the pectoralis major, with its associate muscles seen during sessions , 69-70, at King's College, London. J. Anat. and Physiol., 5: , ) Ruge, G.: Ein Rest des Haut-rumpf-muskels in der Achselgegend des Meschen Achselbogen. Morph. Jahrb., 41: , ) Ruge, G.: Der Hautrumpfmuskel des Menschen. Morph. Jahrb., 48: 1-57, ) v. Saar, G. F.: Zur vergleichenden Anatomie der Brustmuskeln und des Deltamuskels. Archiv. f. Anat. u. Phys., Anat. Abthlg., , ) Sicher, H.: Zur Morphologie des Achselbogens beim Menschen. Morph. Jahrb., 43: , ) Steinbach, K.: Uber Varietdten der Unterzungenbein- und Brustmuskulatur. Anat. Anz., 56: , ) Tischendorf, F.: Eininge seltenere atypische Brustmuskeln des Menschen und ihre Beurteilung. Zeitschr. f. Anat. u. Entwicklungsgesch., 114: , ) Tobler, L.: Der Achselbogen des Menschen, ein Rudiment des Panniculus carnosus der Mammalier. Morph. Jahrb., , ) Wood, J.: Variations in human myology observed during the winter session of at King's College, London. Proc. Roy. Soc. Lond., , ) Yokoh, Y.: Uber zwei Anomalien. Acta Anat. Jpn., 6: 8-9, , (in Japanese)

9 A Rare Anomaly of The Pectoralis Major 183 A: separated muscle of the abdominal part of the pectoralis major Ab: abdominal part of the pectoralis major Abs: inferior lateral superficial brachial artery Ach: muscular arch of the axilla B: separated muscle of the abdominal part of the pectoralis major Bi: biceps brachii Br: brachialis Cam: medial antebrachial cutaneous nerve Cbm: medial brachial cutaneous nerve Cet: tendon of the chondroepitrochlearis Cl: clavicular part of the pectoralis major Co: coracobrachialis CS, C6, C7, C8 and Ti: ventral divisions of the 5th, 6th, 7th and 8th cervical and the 1st thoracic nerves Em: medial epicondyle of the humerus La: latissimus dorsi M: median nerve MC: musculocutaneous nerve Mi: pectoralis minor P1, P2 and P3: pectoral nerve roots Sep: medial brachial intermuscular septim St: sternocostal part of the pectoralis major U: ulnar nerve V: axillary vein 2, 3 and 4: lateral cutaneous branches of the 2nd, 3rd and 4th intercostal nerves Table 1. Summarized data of the previously reported cases on the chondroepitrochlearis

10 184 S. Chiba et al. Plate I Photograph of the present case. Ventral view of the left upper arm.

11 A Rare Anomaly of The Pectoralis Major 185 Plate I