Anatomy of wrist and Hand 2 Assistant professor Dr. Alaa A. Alharba Orthopedic &Hand Surgeon

Deep Fascia : of the palm Is thickened to form the flexor retinaculum and palmar aponeurosis It is a specialized thick bands of deep fascia that hold the long flexor and extensor tendons in position at the wrist. Flexor retinaculum Extensor retinaculum

Flexor retinaculum: It stretches across the front of the wrist and convert the concave anterior surface of the carpal bones into an osteofascial tunnel ( Carpal tunnel), for the passage of the median nerve and the flexor tendons of the thumb and fingers.

Flexor retinaculum: It is attached medially to the pisiform bone and hook of the hamate and laterally to the tubercle of the scaphoid and trapezium bone. The attachment to the trapezium consists of superficial and deep parts and forms a synovial-lined tunnel for passage of the tendon of the flexor carpi radialis.

The upper border of the retinaculum corresponds to the distal transverse skin crease in front of the wrist and is continuous with the deep fascia of the forearm. The lower border is attached to the palmar aponeurosis

Carpal Tunnel: The bones of the hand and flexor retinaculum form the carpal tunnel . The median nerve lies in a restricted space between the tendons of the flexor digitorum superficialis and the flexor carpi radialis muscles.

Palmar aponeurosis : is a triangular and occupies the central area of the palm. It’s apex is attached to the distal border of the flexor retinaculum and receives the insertion of Palmaris longus tendon. The base divides at the base of fingers into four slips. Each slip divides into two bands, one pass superficially to the skin and other passing deeply to the root of fingers to fuse finally with the fibrous flexor sheath and the deep transverse ligament

Palmar aponeurosis : The medial and lateral borders of the aponeurosis are continuous with the thinner deep fascia covering the thenar and hypothenar muscle groups. Functions: to improve hand grip by providing firm attachment to the overlying skin and to protect the underlying tendons

The Dorsum of the Hand

The Dorsum of the Hand Skin: It is thin, hairy, and freely mobile on the underlying tendons and bones. Sensory nerve supply: Superficial branch of radial nerve: it supplies the lateral two thirds of the dorsum of the hand. It divides into several dorsal digital nerves that supply the thumb, index, and middle fingers, and the lateral sides of the ring finger. Posterior cutaneous branch of ulnar nerve: it supplies the medial third of the dorsum of the hand. It divides into several dorsal digital branches that supply the medial side of the ring and the sides of the little finger.

Extensor retinaculum The retinaculum is attached medially to the pisiform and hook of the hamate and laterally to the distal end of the radius. The upper and lower borders of the retinaculum are continuous with the deep fascia of the forearm and hand respectively.

The extensor retinaculum send fibrous septa pass to the underlying radius and ulna and form six compartments that contain the tendons of the extensor muscles. Each compartment is provided with a synovial sheath , which extends above and below the retinaculum.

These compartments from radial to ulnar side 1st :contains the tendons of Abductor pollicis longus(AbPL) and extensor pollicis brevis(EPB) have a separate synovial sheaths but share a common compartment. 2nd:contains the tendons of Extensor carpi radialis longus(ECRL) and brevis(ECRB) tendons share a common synovial sheath and are situated on the lateral part of the posterior surface of the radius. 3rd:contains the tendons of Extensor pollicis longus tendon(EPL) winds around the medial side of the dorsal tubercle of the radius. 4th:contains the tendons of Extensor digitorum(ED) and extensor indicis(EI) tendons share a common synovial sheath and are situated on the lateral part of the posterior surface of the radius.

5.5th: contains the tendons of Extensor digiti minimi(EDM) tendon is situated posterior to the distal radioulnar joint. 6.6th contains the tendons of Extensor carpi ulnaris(ECU) which grooves the posterior aspect of the head of the ulna.