The term “Land Clark Muscles” is not a recognized anatomical term; instead, the structure often referred to in this context is more accurately known as Langer’s Axillary Arch Muscle. This anatomical variation may also be called Langer’s muscle, axillary arch, or axillopectoral muscle. It represents a supernumerary muscle, meaning it is an extra muscle not typically found in all individuals. This muscular slip is considered a remnant of the panniculus carnosus, a superficial muscle layer found in many lower mammals.
Understanding Langer’s Axillary Arch Muscle
Langer’s Axillary Arch Muscle is located in the axilla, the armpit region. It commonly presents as a band of muscle fibers or a musculotendinous slip. This arch originates from the anterior border of the latissimus dorsi muscle, a large back muscle. From there, it extends across the axillary region, inserting into the pectoralis major muscle, a large chest muscle. Other insertion points can include the fascia of the coracobrachialis muscle or the biceps brachii.
The size of Langer’s Axillary Arch can vary, measuring between 7 to 10 centimeters in length and 0.5 to 1.5 centimeters in width. While its origin from the latissimus dorsi is consistent, there is wide variation in its shape, size, and insertion. It is an anatomical variant, and its prevalence varies significantly among different populations, ranging from 1.7% in some populations to as high as 43.8% in others. A meta-analysis indicated an overall prevalence of approximately 5.3% of limbs. It is found on one side, but can sometimes be bilateral.
Potential Clinical Relevance
While typically asymptomatic, the presence of Langer’s Axillary Arch Muscle can sometimes lead to clinical symptoms. Because it crosses over the axillary neurovascular bundle, which contains nerves and blood vessels, it can cause compression. This compression may affect the brachial plexus, leading to symptoms like chronic pain, numbness, or tingling sensations in the upper limb.
The arch can also compress the axillary artery or vein, causing circulatory issues, swelling, or even venous thrombosis. It may mimic other conditions, such as an enlarged lymph node or a soft tissue tumor, during a physical examination. Medical professionals may identify it during imaging scans or incidentally during surgical procedures in the axillary region. Awareness of this anatomical variation aids accurate diagnosis and helps prevent complications during surgical interventions.