Four-headed biceps brachii, three-headed coracobrachialis muscles associated with arterial and nervous anomalies in the upper limb

Coracobrachialis muscle morphology and coexisted neural variants: a cadaveric case series

PURPOSE

The current cadaveric case series evaluates the coracobrachialis muscle morphology, the related musculocutaneous nerve origin, course, and branching pattern, as well as associated adjacent neuromuscular variants.

MATERIALS AND METHODS

Twenty-seven (24 paired and 3 unpaired) cadaveric arms were dissected to identify the coracobrachialis possible variants with emphasis on the musculocutaneous nerve course and coexisted neural variants.

RESULTS

Four morphological types of the coracobrachialis were identified: a two-headed muscle in 62.96% (17/27 arms), a three-headed in 22.2% (6/27), a one-headed in 11.1% (3/27), and a four-headed in 3.7% (1 arm). A coracobrachialis variant morphology was identified in 37.04% (10/27). A three-headed biceps brachii muscle coexisted in 23.53% (4/17). Two different courses of the musculocutaneous nerve were recorded: 1. a course between coracobrachialis superficial and deep heads (in cases of two or more heads) (100%, 24/24), and 2. a medial course in case of one-headed coracobrachialis (100%, 3/3). Three neural interconnections were found: 1. the lateral cord of the brachial plexus with the medial root of the median nerve in 18.52%, 2. the musculocutaneous with the median nerve in 7.41% and 3. the radial with the ulnar nerve in 3.71%. Duplication of the lateral root of the median nerve was identified in 11.1%.

CONCLUSIONS

The knowledge of the morphology of the muscles of the anterior arm compartment, especially the coracobrachialis variant morphology and the related musculocutaneous nerve variable course, is of paramount importance for surgeons. Careful dissection and knowledge of relatively common variants play a significant role in reducing iatrogenic injury.

A Bilateral Symmetric Accessory Coracobrachialis Muscle Combined With an Interconnection of the Musculocutaneous Nerve With the Median Nerve

This report describes a bilateral symmetric accessory coracobrachialis muscle variant coexisting with a unilateral interconnection of the musculocutaneous nerve and the median nerve. An 80-year-old female cadaver was dissected. The bilateral coracobrachialis muscle variant consisted of three heads: two superficial heads and one deep head. One superficial head arose from the tip of the coracoid process, while the other originated from the short head tendon of the biceps brachii. The deep head of the coracobrachialis muscle emerged from the base of the coracoid process. The musculocutaneous nerve bilaterally coursed between the superficial and deep heads. On the right side, the three-headed coracobrachialis muscle coexisted with an ipsilateral interconnection of the musculocutaneous nerve and the median nerve, located at the lower third of the arm. While the presence of a unilateral three-headed coracobrachialis muscle is not rare (with a prevalence range of 0-22.2%), as well as the distal interconnection between the musculocutaneous nerve and the median nerve at the lower third of the arm (with a prevalence range of 1.8-53.6%), the coexistence of the current bilateral three-headed coracobrachialis muscle variant with the distal interconnection of the musculocutaneous and median nerves is quite unusual. A similar report underscores the finding of the bilateral coracobrachialis muscle variant.

A proposal for a new classification of the Coracobrachialis longus: A rare case or a new, distinct muscle?

BACKGROUND

The coracobrachialis muscle, along with the brachialis and biceps brachii muscles, belong to the anterior group of the brachial region. It is characterized by high level of morphological variabilities, with a common variation being the coracobrachialis longus (CBL) muscle. The CBL may be recognized as a distal part of the coracobrachialis muscle, originating from the anteromedial surface of the humerus, however, the two muscles are distinct from each other, and the distal attachment of the CBL is longer and located closer to the elbow joint. The CBL muscle may also be inserted on to various structures. The aim of the present study was to determine the frequency of the CBL muscle among a studied population, and to prepare a classification based on its morphological features.

MATERIAL AND METHODS

Classical anatomical dissection was performed on 100 upper limbs from fifty human cadavers (30 female and 20 male) fixed in 10% formalin solution.

RESULTS

The coracobrachialis muscle was found in all individuals, and the CBL muscle was present in 11%, i.e. 11 upper limbs: four women, and seven men; five left and six right. Significantly, in all cadavers in which the coracobrachialis longus was found, its presence was unilateral (five left and six right). A new classification of the CBL can be proposed based on its insertion: Type I characterized by a distal attachment located on the medial epicondyle (73% of all cases of the CBL) and Type II by an insertion into the olecranon (27% of all cases of the CBL).

CONCLUSION

The CBL muscle is morphologically variable. More studies focused on the course of this muscle among various populations are needed. Nevertheless, our findings indicate that the CBL muscle could be classified as a distinct muscle.

Supernumerary Head of the Biceps Brachii Muscle: An Anatomic Variant With Clinical Implications

Objective

The purpose of this anatomic case report is to describe a variation of the biceps brachii muscle identified in an adult male cadaveric specimen and its potential clinical relevance.

Methods

A cadaveric specimen with a left supernumerary biceps brachii muscle was dissected. Adjacent neurovascular structures were isolated, and their pathways were observed for possible areas of compression.

Results

A tricipital supernumerary head of the biceps brachii muscle was noted on the left upper extremity in an embalmed human cadaveric specimen. The median nerve and brachial artery maintained their common neurovascular path. The musculocutaneous nerve passed deep to the third head of the anatomic variant before distributing its cutaneous branches as the lateral antebrachial cutaneous nerve.

Conclusion

The presence of a supernumerary biceps brachii muscle may cause neurovascular compression of the median nerve, musculocutaneous nerve, or brachial artery, resulting in peripheral nerve deficits. When patient conditions are refractory to care, they may warrant careful evaluation of the anterior compartment of the arm for potential anomalous muscle variations.

Clinical relevance of the anatomy of the long head bicipital groove, an evidence-based review

Pathology in the bicipital groove can be a source of anterior shoulder pain. Many studies have compared treatment techniques for the long head biceps tendon (LHBT) without showing any clinically significant differences. As the LHBT is closely related to the bicipital groove, anatomical aspects of this groove could also be implicated in surgical outcomes. The aim of this review is to contribute to developing the optimal surgical treatment of LHBT pathology based on clinically relevant aspects of the bicipital groove. Medline/PubMed was systematically searched using key words "bicipital" and "groove" and combinations of their synonyms. Studies reporting on evolution, embryonic development, morphometry, vascularization, innervation, and surgical treatment of the LHBT and the bicipital groove were included. The length of the bicipital groove reported in the included studies ranged from 81.00 mm to 87.33 mm, width from 7.74 mm to 11.60 mm, and depth from 3.70 mm to 6.00 mm. The anatomy of the bicipital groove shows a bottleneck narrowing approximately two-thirds from superior. The transverse humeral ligament can constrain the bicipital groove and could be involved in anterior shoulder pain. When either LHBT tenotomy or tenodesis is performed, routinely releasing the transverse ligament could decrease postoperative anterior shoulder pain, which has frequently been reported in the literature. To avoid the bottle neck narrowing, a location below the bicipital groove may be preferred for biceps tenodesis over a more proximal tenodesis site. Level of evidence: IV.

Superficial brachioulnar artery and its clinical significance

The authors report a rare variation of the vasculature in the upper limbs of an 84-year-old male cadaver. A high bifurcation of the brachial artery occurred bilaterally at the proximal one-third of each arm. The radial arteries were larger than the ulnar arteries and gave origin to the common interosseous arteries. At the cubital fossa, the ulnar arteries traversed medial to the median nerves, continuing superficial to all forearm muscles except the palmaris longus tendon, characteristic of superficial brachioulnar arteries. The aforementioned variations have rarely been reported in previous literature and demonstrate important clinical significance in relation to accidental intra-arterial injections, errors in blood pressure readings, as well as orthopedic, plastic, and vascular surgeries of the upper limbs.

Coracobrachialis Longus Muscle: Humeroepitrochlearis

During a routine anatomical dissection of the right brachium of a 68-year-old male cadaver, an extremely rare variation of the coracobrachialis longus muscle was discovered. It started from the medial surface of the middle part of the humerus with a well-formed muscle portion and then continued into the well-presented distal tendinous portion, which was attached to the medial epicondyle of the humerus. We also briefly review the reported variations of the coracobrachialis and their potential clinical significance.

A Novel Type of Coracobrachialis Muscle Variation and a Proposed New Classification

During a routine anatomical dissection in the right brachium of a 75-year-old male cadaver, a novel variation of the coracobrachialis muscle (CB) was discovered. It consisted of three parts: proximal, starting from the upper border of the scapula; medial, presenting the well-accessed CB; and distal, formed by a proximal tendinous part that arose from the coracoid process and then transitioned into a well-defined muscle body and a distal tendinous part attached to the medial epicondyle. We also present a new systematic classification of CB variations, dividing them into two simple groups.

Rare muscular variations identified in a single cadaveric upper limb: a four-headed biceps brachii and muscular elevator of the latissimus dorsi tendon

Supernumerary or accessory heads of the biceps brachii are persistent muscular structures which can vary in number and location in the arm. Variations in other arm muscles, such as the coracobrachialis, can accompany supernumerary biceps brachii musculature in the upper limb. In this case report, we describe two rare muscular variants in a single adult male: a four-headed biceps brachii and the muscular elevator of the latissimus dorsi tendon. Additionally, accessory muscles of the brachialis and flexor digiti minimi brevis were identified in the upper limb. To our knowledge, the muscular variants identified here are considered rare, and their co-occurrence in a single upper limb has not been described previously. Also, a four-headed biceps brachii consisting of both the infero-medial and infero-lateral humeral heads has not been described previously to our knowledge. We postulate that the simultaneous appearance of several muscular variations may indicate a signaling disruption in embryogenesis during muscle patterning of the ventral limb bud. Knowledge of variant musculature in the arm is important for surgeons and clinicians as these muscles and their aberrant innervation patterns can complicate surgical procedures and may compress arteries and nerves producing upper limb pain and paresthesia. The clinical, functional and embryological implications of the upper limb variants are discussed.

Bilateral absence of musculocutaneous nerve with unusual branching pattern of lateral cord and median nerve of brachial plexus

A 43-year-old female cadaver showed a complete bilateral absence of the musculocutaneous nerve. The anterior compartment muscles of both arms were supplied by median nerve excepting the coracobrachialis which was innervated by a direct branch from the lateral cord of brachial plexus. The median nerve, after supplying the biceps and brachialis muscles, gave onto the lateral cutaneous nerve of the forearm. The median nerve also showed variation on the left side where it was formed by two lateral roots and one medial root. Variations of the brachial plexus are of great interest to anatomists, clinicians and surgeons, in that they may be incorporated in their day to day practice. Our present case may be noted for its clinical and surgical significance in the variations of brachial plexus which can be useful for diagnostic purposes.