The Palmaris Longus muscle is a fascinating and unique muscle found in the human body. In this article, we will delve into the anatomy of this muscle, its actions, variations, and clinical significance.
Understanding the intricacies of the Palmaris Longus muscle will provide you with valuable insight into its functions and relevance in the field of medicine.
Anatomy of the Palmaris Longus Muscle:
The Palmaris Longus muscle originates from the medial epicondyle of the humerus, the transverse carpal ligament, and the palmar aponeurosis. Its primary action is to flex the hand at the wrist joint.
The muscle is innervated by the median nerve, which it partially covers. The muscle’s insertion point is the palmar fascia, and its size can vary significantly, ranging from a thin slip of tendon to a wide, flat tendon. In some cases, the muscle belly may extend into the wrist, potentially compressing the median nerve.
| Origin | Insertion | Function | Nerve Supply | Blood Supply |
|---|---|---|---|---|
| Medial epicondyle of the humerus through the common flexor tendon. | Flexor retinaculum and palmar aponeurosis. | Anchors the skin and fascia of the hand to keep it from sliding toward the phalanges. Aids the flexion of the wrist. | C7 and C8 median nerve. | Ulnar collateral arteries. |
Prevalence and Variations:
Interestingly, the Palmaris Longus muscle is absent in about 15-25% of the population, with this number varying across different ethnic groups. The absence of the muscle does not equate to reduced grip strength.
To determine whether the muscle is present or absent, one can palpate the tendon in the midline of the anterior wrist by touching the pads of the fifth finger and the thumb while flexing the wrist. If the tendon is present, it will be visible in the midline of the anterior wrist.
Clinical Significance:
The Palmaris Longus muscle has several clinical implications. For instance, it is often used as a guide for injecting the carpal tunnel or blocking the median nerve at the wrist. Additionally, the tendon of the Palmaris Longus is the most commonly used tendon graft for hand surgeries.
Prior to surgery, it is essential to palpate the tendon and determine its thickness. If the tendon is small or absent, the patient should be informed and consented for a possible graft from another area of the body.
Palmaris Longus Tendonitis and Pain
The tendon of the Palmaris Longus is unique among forearm tendons, as it does not pass through the carpal tunnel. Instead, it is positioned above the carpal ligament, which forms the inner aspect of the wrist. When the muscle contracts, its tendon may exert pressure on the ligament, potentially mimicking some symptoms of Carpal Tunnel Syndrome.
It is important to note that not everyone possesses this muscle. If present, the tendon can be observed by forming a claw with your hand and flexing the wrist. The tendon will appear prominently across the center of the wrist, extending from the forearm to the hand.
Trigger Points in the Palmaris Longus
A Trigger Point in the Palmaris Longus can lead to pain and tingling sensations, similar to those experienced in carpal tunnel syndrome. This may manifest as a superficial prickling sensation in the palm, with referred pain causing tenderness and hindering the use of hand tools.
Furthermore, the Palmaris Longus is positioned over vital nerves and blood vessels in the forearm. In the context of Neuromuscular Therapy for Repetitive Strain Injuries, it has been found that tightness and tension in this muscle can obstruct blood flow and nerve signal transmission to the hand.
When addressing flexor muscle issues and tendonitis-related inner elbow irritation, as well as nerve entrapment syndromes like cubital tunnel syndrome, it is essential to include treatment of the Palmaris Longus muscle. Releasing tension often results in a warm sensation down the arm, which is likely due to restored blood flow.
As nerves and blood vessels frequently travel together in neurovascular bundles, increased blood flow would also imply enhanced nerve signal transmission, both of which are crucial for maintaining forearm and hand health.
Conclusion
The Palmaris Longus muscle is a fascinating and clinically significant structure with a unique anatomy and varied presence in the human population. Understanding its origins, actions, innervations, and prevalence is crucial for medical professionals working with hand and wrist injuries or surgeries. Remember, this article is for educational purposes only, and you should always consult your doctor before making any decisions about your medical care.
MD, PhD. Physical Medicine & Rehabilitation Physician from São Paulo - Brazil. Pain Fellowship in University of São Paulo.