Palmar aponeurosis

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Attachments, innervation and functions of the intrinsic muscles of the hand.

The palmar aponeurosis is a strong thickening of the central part of the deep fascia of the palm. It has little mobility and covers the underlying neurovascular structures, tendons and intrinsic muscles of the hand.

The palmar aponeurosis is an inverted triangle in shape and fans out over the palm and thins out medially and laterally over the hypothenar and thenar eminences, respectively.

The median nerve entering the palm through the carpal tunnel and the superficial palmar arch travel deep to the palmar aponeurosis to reach their targets. In contrast, the palmar cutaneous branch of the ulnar nerve courses above the palmar aponeurosis to reach the hypothenar eminence. The tendons of the flexor digitorum superficialis and profundus pass through digital slips formed between the palmar aponeurosis and the heads of the metacarpal bones, accompanied by the palmar digital arteries and nerves.

The tendon of the palmaris longus muscle attaches to the palmar aponeurosis while the palmaris brevis originates from it. Some sources even consider the palmar aponeurosis as the degenerated tendon of palmaris longus.

As the palmar aponeurosis has superficial fibers attaching to the skin, it improves the grip of the hand and protects the underlying flexor tendons, vessels and nerves.