An unusually medial axillary arch muscle

Area of Science:

• Anatomy
• Morphology
• Human Anatomy

Background:

• Anatomical variations in the upper limb are common and can impact surgical procedures.
• The axillary arch is a rare anatomical variant, typically located more laterally.
• Understanding variations of the latissimus dorsi and associated muscles is crucial for clinical practice.

Purpose of the Study:

• To document and describe an unusual muscular slip in the left upper limb of an adult male cadaver.
• To determine the origin, insertion, and innervation of this muscular slip.
• To classify this finding in relation to known anatomical variations like the axillary arch.

Main Methods:

• Gross anatomical dissection of an adult male cadaver's left upper limb.
• Detailed observation and measurement of the anomalous muscular slip and its attachments.
• Identification of related nerves and muscles, including the latissimus dorsi, pectoralis minor, teres major, biceps brachii, and coracobrachialis.

Main Results:

• A triangular muscular slip (3.5 cm x 2.5 cm) originated from the latissimus dorsi.
• The slip inserted via a 6 cm tendon onto the coracoid process, with fibrous strands attaching to pectoralis minor and biceps/coracobrachialis origins.
• Tendinous bands connected the slip's margin to the teres major; the thoracodorsal nerve supplied the latissimus dorsi but not the slip directly.
• This represents an axillary arch muscle in an unusually medial position.

Conclusions:

• The identified muscular slip represents a rare, medially located axillary arch variant.
• This anatomical variation may have implications for understanding nerve pathways and surgical approaches in the axillary region.
• Further studies are needed to determine the prevalence and functional significance of such medial axillary arch variations.