|Year : 2015 | Volume
| Issue : 1 | Page : 46-49
Axillary arch muscle- a case report
Kanika Sachdeva1, Monika Lalit1, Anupama Mahajan2, Poonam Delmotra3
1 Assistant Professor, Sri Guru Ram Das Institute of Medical Sciences & Research, Amritsar, Punjab, India
2 Professor, Sri Guru Ram Das Institute of Medical Sciences & Research, Amritsar, Punjab, India
3 Associate Professor, Department of Anatomy, Chintpurni Medical College & Hospital, Bungal, Pathankot, Punjab, India
|Date of Web Publication||29-Nov-2019|
Assistant Professor of Anatomy Sri Guru Ram Das Institute of Medical Sciences & Research, Amritsar, Punjab
Source of Support: None, Conflict of Interest: None
Anomalous muscles donot usually cause symptoms but are of academic interest. Axillary arch is a variable muscular slip encountered in axilla. Purpose of the present study was to report a rare case of axillary arch muscle. Knowledge of this muscle variation and the possibility of finding it during axillary procedures are crucial for lymph node staging, lymphaedenectomy and for differential diagnosis in compressive pathologies of axillary vessels and brachial plexus. During routine dissection of left axilla in a 60-year old male cadaver, an anomalous muscular slip was encountered. The slip was extending between latissimus dorsi muscle to coracoid process, deltoid muscle, fascia covering biceps and coracobrachialis and was confirmed as axillary arch muscle. The embryological basis, genetics and clinical implications have been discussed. This rare variation will be of interest not only to anatomists but also for clinicians and surgeons dealing with this area.
Keywords: axillopectoral muscle, Langer’s arch, pectoralis major, lattisimus dorsi
|How to cite this article:|
Sachdeva K, Lalit M, Mahajan A, Delmotra P. Axillary arch muscle- a case report. Natl J Clin Anat 2015;4:46-9
| Introduction|| |
Anatomical variations and abnormalities of muscles of upper limb have become significant because of new imaging techniques such as computed tomography & magnetic resonance imaging. Also these variations are important in order to define the anatomical features of each in relation to clinical diagnosis and for surgical procedures. Anomalous muscles usually do not cause symptoms but are of academic interest. They become a surgical problem when they produce symptoms or are difficult to differentiate from soft tissue tumours. Axillary arch muscle, also known as Langer’s muscle, Axillopectoral muscle, Pectodorsal muscle, Arcus axillaris or the Achselbogen Muskel is a rare muscular anomaly of axilla. It is a muscular arch, 7-10 cm in length and 5-15 mm in breadth, may cross from edge of latissimus dorsi, midway in the posterior axillary fold, over the front of axillary vessels and nerves to join the tendon of pectoralis major, corachobrachialis or fascia over biceps.
| Case Report|| |
During routine dissection of left axilla in a 60-year old male cadaver, at Chintpuni Medical College & Hospital, Bungal, Pathankot (Punjab), an anomalous muscular slip was encountered. It was taking origin from latissimus dorsi, but showed variable insertions going towards coracoid process, deltoid muscle, fascia covering biceps & coracobrachial, crossing axillary vessels, cords & branches of brachial plexus and was confirmed as axillary arch muscle. It was 8 cm in length and 1.5 cm at its broadest point. No such anomaly was found on the contralateral limb. [Figure 1].
|Figure 1: Dissected left axilla showing axillary arch|
Abbreviations : DEL : Deltoid Muscle; AA: Axillary Arch; CP: Coracoid Process ; CB: Corachobrachialis Muscle; BB: Biceps Brachii Muscle; TBB: Tendon of Biceps Brachii; LD: Latissimus Dorsi; AS&F: Axillary Skin & Fascia; NVB: Neurovascular Bundle.
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| Discussion|| |
Axillary arch muscle was accurately described by Langer in 1846 and thereafter it became known as Langer’s arch. Later this variation was identified as axillopectoral muscle.
Many variants of this anomaly have been observed, like the muscle adhering to the coracoid process of scapula, medial epicondyle of humerus, teres major, long head of triceps brachii, biceps brachii and pectoralis minor. It is usually seen as a single band but it can divide into double or, rarely, multiple structures which extend across axilla. In its complete and common form, it arises from latissimus dorsi and inserts into trilaminar tendon of pectoralis major on the humerus, while in its incomplete form it presents with varying insertions into pectoralis minor, corachobrachialis, long or short heads of biceps, teres major, coracoid process, first rib, axillary fascia or coracobrachialis fascia. MRI studies have concluded that 76% arches insert solely onto the anterior deep fascia of corachobrachialis muscle, 6% onto deep fascia of pectoralis major muscle and 18% insert via a small weblike structure on to the fascia of both coracobrachialis and the pectoralis major muscles.
The nerve supply to this variant muscle is most commonly from medial pectoral nerve thus indicating embryological origin of these muscles from the pectoral muscle but those closely connected to latissimus dorsi may be supplied by thoracodorsal nerve.
The occurrence of axillary arch varies in different races, as low as 0.25% in British to 10% in Belgian subjects. In Japanese and South Indian population, it is 7% and 1.47% respectively. Prevalence varies from 3% to 27% in cadaveric dissection studies. Merida- Velasco et al reports the occurrence of this variation to be more common in males than in females. They further report its commoner bilateral presentation as compared to a unilateral one.
The embryological derivation of Langer’s arch remains unknown but the most reliable theory supports its origin from panniculus carnosus, which is embryological remnant of a more extensive sheet of skin associated musculature lying at junction between superficial fascia and subcutaneous fat. This structure is well developed in lower mammals, particularly rodents, while in higher primates & humans it is evident only as muscle such as platysma & dartos; in the remainder of the body it becomes vestigial. In lower mammals, panniculus carnosus is highly developed to form the pectoral group of muscles. However, in man, it has retrogressed because its functional importance decreased during evolution in favour of wider upper limb mobility.
Another hypothesis supports that limb muscles develop in situ from mesenchyme around the developing bones, this mesenchyme being derived from the somatic layer of the lateral plate mesoderm. Cihak described 4 fundamental phases in the ontogenesis of muscle pattern. This muscle anomaly could have arisen during phase 3 of ontogenesis of the muscles in left axilla. During phase 3, some muscle primordia from different layers fuse to form a single muscle. Grim, however, stated that some muscle primordia disappear through cell death, despite the fact that the cells within them have differentiated to the point of containing myofilaments. Persistence of some cells between latissimus dorsi and pectoralis major may account for the muscular slip in the case described.
Genetic Basis: A possible genetic basis has been pointed out by Aziz who found it bilaterally in a patient of trisomy.
Cadaveric, neurosurgical & medicodiagonostic evidences of the presence of axillary arch of Langer is assumed to produce symptoms similar to those of entrapment or obstruction type syndromes and may also influence the motor control of shoulder girdle. It has been shown that the presence of axillary arch significantly increases the strength, endurance and motor control of the shoulder along with an increase of paraesthetics in women but not in men. Possible shoulder stabilization and an improved proprioception were also found both in men & most of women with axillary arch.
Aberrant slips may also cause axillary vessel entrapment syndromes, branches of brachial plexus entrapment symptoms and has been suggested to have a role in development of lymphedema of upper limb. Recognition that a patient may have an arch muscle before surgery is reported to prevent unforeseen bleeding, nerve damage, lymphatic disruption. Division & removal of this arch has been recommended to reduce postop edema. Knowledge of this variation may help during lymph node staging & lymphedenectomy, radical mastectomy, cannulization, cathetarization of axillary vessels, transposing & anastomosing cephalic vein to upper basilic/axillary vein in cephalic vein stenosis treatment syndrome,while using latissimus dorsi flaps to treat the traumatic wounds of the antecubital fossa, treating shoulder displacement, fracture of the humerus, the nerve block and to treat the functional limitation of the range of shoulder movement.
Compression of neurovascular bundle by axillary arch should be considered as differential diagnosis of thoracic outlet and hyperabduction syndromes.
The presence of axillary arch muscle during physical examination may be detected in physical examination as a palpable mass within the axilla or a loss of the axillary concavity. However a physical examination may not reveal all the axillary arch muscles and an MRI may be needed for an accurate diagnosis.
| Conclusions|| |
To conclude, this muscular anomaly holds a great deal of importance as it is rare and important to know in many clinical applications. It has a potential to cause significant functional defects, has surgical implications & may be of particular interest to orthopaedic surgeons, neurologists and cosmetic surgeons.
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