Tuesday 28 June 2016

The Palm of the Hand-Skin-The Palmar Aponeurosis-Dupuytren’s Contracture-Carpal Tunnel Syndrome-

The Palm of the Hand
Skin
The skin of the palm of the hand is thick and hairless. It is bound down to the underlying deep fascia by numerous fibrous bands. The skin shows many flexure creases at the sites of skin movement, which are not necessarily placed at the site of joints. Sweat glands are present in large numbers.
The palmaris brevis is a small muscle that arises from the flexor retinaculum and palmar aponeurosis and is inserted into the skin of the palm. It is supplied by the superficial branch of the ulnar nerve. Its function is to corrugate the skin at the base of the hypothenar eminence and so improve the grip of the palm in holding a rounded object.
The sensory nerve supply to the skin of the palm is derived from the palmar cutaneous branch of the median nerve, which crosses in front of the flexor retinaculum and supplies the lateral part of the palm, and the palmar cutaneous branch of the ulnar nerve; the latter nerve also crosses in front of the flexor retinaculum and supplies the medial part of the palm.
The skin over the base of the thenar eminence is supplied by the lateral cutaneous nerve of the forearm or the superficial branch of the radial nerve.

The Palmar Aponeurosis
The palmar aponeurosis is triangular and occupies the central area of the palm. The apex of the palmar aponeurosis is attached to the distal border of the flexor retinaculum and receives the insertion of the palmaris longus tendon. The base of the aponeurosis divides at the bases of the fingers into four slips. Each slip divides into two bands, one passing superficially to the skin and the other passing deeply to the root of the finger; here each deep band divides into two, which diverge around the flexor tendons and finally fuse with the fibrous flexor sheath and the deep transverse ligaments.


The medial and lateral borders of the palmar aponeurosis are continuous with the thinner deep fascia covering the hypothenar and thenar muscles. From each of these borders, fibrous septa pass posteriorly into the palm and take part in the formation of the palmar fascial spaces . The function of the palmar aponeurosis is to give firm attachment to the overlying skin and so improve the grip and to protect the underlying tendons.

Dupuytren’s Contracture
Dupuytren’s contracture is a localized thickening and contracture of the palmar aponeurosis, which limits hand function and may eventually disable the hand. It commonly starts near the root of the ring finger and draws that finger into the palm, flexing it at the metacarpophalangeal joint. Later, the condition involves the little finger in the same manner. In long-standing cases, the pull on the fibrous sheaths of these fingers results in flexion of the proximal interphalangeal joints. The distal interphalangeal joints are not involved and are actually extended by the pressure of the fingers against the palm.

Surgical division of the fibrous bands followed by physiotherapy to the hand is the usual form of treatment. The alternative treatment of injection of the enzyme collagenase into the contracted bands of fibrous tissue has been shown to significantly reduce the contractures and improve mobility.

Carpal Tunnel Syndrome
The carpal tunnel, formed by the concave anterior surface of the carpal bones and closed by the flexor retinaculum, is tightly packed with the long flexor tendons of the fingers, with their surrounding synovial sheaths, and the median nerve. Clinically, the syndrome consists of a burning pain or “pins and needles” along the distribution of the median nerve to the lateral three and a half fingers and weakness of the thenar muscles. It is produced by compression of the median nerve within the tunnel. The exact cause of the compression is difficult to determine, but thickening of the synovial sheaths of the flexor tendons or arthritic changes in the carpal bones are thought to be responsible in many cases. As you would expect, no paresthesia occurs over the thenar eminence because this area of skin is supplied by the palmar cutaneous branch of the median nerve, which passes superficially to the flexor retinaculum. The condition is dramatically relieved by decompressing the tunnel by making a longitudinal incision through the flexor retinaculum.





























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