Fascial Spaces of the Palm-Fascial Spaces of the Palm and Infection -Pulp Space of the Fingers--Pulp-Space Infection (Felon)

Fascial Spaces of the Palm

Normally, the fascial spaces of the palm are potential spaces filled with loose connective tissue. Their boundaries are important clinically because they may limit the spread of infection in the palm.

The triangular palmar aponeurosis fans out from the lower border of the flexor retinaculum. From its medial border, a fibrous septum passes backward and is attached to the anterior border of the 5th metacarpal bone. Medial to this septum is a fascial compartment containing the three hypothenar muscles; this compartment is unimportant clinically. From the lateral border of the palmar aponeurosis, a second fibrous septum passes obliquely backward to the anterior border of the third metacarpal bone. Usually, the septum passes between the long flexor tendons of the index and middle fingers. This second septum divides the palm into the thenar space, which lies lateral to the septum (and must not be confused with the fascial compartment containing the thenar muscles), and the midpalmar space, which lies medial to the septum. Proximally, the thenar and midpalmar spaces are closed off from the forearm by the walls of the carpal tunnel. Distally, the two spaces are continuous with the appropriate lumbrical canals .

The thenar space contains the first lumbrical muscle and lies posterior to the long flexor tendons to the index finger and in front of the adductor pollicis muscle

The midpalmar space contains the 2nd, 3rd, and 4th lumbrical muscles and lies posterior to the long flexor tendons to the middle, ring, and little fingers. It lies in front of the interossei and the third, fourth, and fifth metacarpal bones.

The lumbrical canal is a potential space surrounding the tendon of each lumbrical muscle and is normally filled with connective tissue. Proximally, it is continuous with one of the palmar spaces

Fascial Spaces of the Palm and Infection

The fascial spaces of the palm are clinically important because they can become infected and distended with pus as a result of the spread of infection in acute suppurative tenosynovitis; rarely, they can become infected after penetrating wounds such as falling on a dirty nail.

Pulp Space of the Fingers

The deep fascia of the pulp of each finger fuses with the periosteum of the terminal phalanx just distal to the insertion of the long flexor tendons and closes off a fascial compartment known as the pulp space . Each pulp space is subdivided by the presence of numerous septa, which pass from the deep fascia to the periosteum. Through the pulp space, which is filled with fat, runs the terminal branch of the digital artery that supplie the diaphysis of the terminal phalanx. The epiphysis of the distal phalanx receives its blood supply proximal to the pulp space.

Pulp-Space Infection (Felon)

The pulp space of the fingers is a closed fascial compartment situated in front of the terminal phalanx of each finger. Infection of such a space is common and serious, occurring most often in the thumb and index finger. Bacteria are usually introduced into the space by pinpricks or sewing needles.

Because each space is subdivided into numerous smaller compartments by fibrous septa, it is easily understood that the accumulation of inflammatory exudate within these compartments causes the pressure in the pulp space to quickly rise. If the infection is left without decompression, infection of the terminal phalanx can occur. In children, the blood supply to the diaphysis of the phalanx passes through the pulp space, and pressure on the blood vessels could result in necrosis of the diaphysis. The proximally located epiphysis of this bone is saved because it receives its arterial supply just proximal to the pulp space.

The close relationship of the proximal end of the pulp space to the digital synovial sheath accounts for the involvement of the sheath in the infectious process when the pulpspace infection has been neglected.

 

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.