Hand and wrist

• The anatomical snuffbox is a triangular skin depression on the lateral side of the wrist, bounded medially by the tendon of the extensor pollicis longus and laterally by the tendons of the abductor pollicis longus and the extensor pollicis brevis.
• The scaphoid bone is most easily palpated in the anatomical snuffbox.
• The pulsation of the radial artery can be felt in the anatomical snuffbox.
• The following structures pass superficial to the flexor retinaculum from medial to lateral in the anterior aspect of the wrist: Ulnar nerve, Ulnar artery, Palmar cutaneous branch of the ulnar nerve, Palmaris longus tendon, Palmar cutaneous branch of the median nerve.
• Near the proximal interphalangeal joint, the extensor expansion splits into three parts: a central part, which is inserted into the base of the middle phalanx, and two lateral parts, which converge to be inserted into the base of the distal phalanx.
• The extensor expansion receives the insertion of the corresponding interosseous muscle and the lumbrical muscle.
• The following structures pass beneath the flexor retinaculum from medial to lateral in the anterior aspect of the wrist: Flexor digitorum superficialis tendons and, posterior to these, tendons of flexor digitorum profundus, Median nerve, Flexor pollicis longus tendon, Flexor carpi radialis tendon.
• The following structures pass superficial to the extensor retinaculum from medial to lateral in the posterior aspect of the wrist: Dorsal (posterior) cutaneous branch of the ulnar nerve, Basilic vein, Cephalic vein, Superficial branch of the radial nerve.
• The following structures pass beneath the extensor retinaculum from medial to lateral in the posterior aspect of the wrist: Extensor carpi ulnaris tendon, Extensor digiti minimi tendon, Extensor digitorum and extensor indicis tendons, Extensor pollicis longus tendon, Extensor carpi radialis longus and brevis tendons, Abductor pollicis longus & the extensor pollicis brevis tendons.
• The palmar aponeurosis is a triangular-shaped thickening of deep fascia that occupies the central area of the palm, with the apex of the palmar aponeurosis attached to the distal border of the flexor retinaculum and receiving the insertion of the palmaris longus tendon.
• The base of the palmar aponeurosis divides at the bases of the fingers into four slips.
• 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.
• The flexor retinaculum is a thickening of deep fascia, measuring 2-3 cm, that holds the long flexor tendons in position at the wrist, stretching across the front of the wrist and converting the concave anterior surface of the hand into an osteofascial tunnel, called the carpal tunnel.
• The flexor retinaculum is attached medially to the pisiform bone and the hook of the hamate and laterally to the scaphoid and the trapezium bones.
• The carpal tunnel is a tunnel formed by the flexor retinaculum on the anterior surface of the wrist.
• The tendons of flexor digitorum superficialis, flexor digitorum profundus and flexor pollicis longus pass through the tunnel in addition to the median nerve.
• The median nerve passes beneath the flexor retinaculum in a restricted space between the flexor digitorum superficialis and the flexor carpi radialis muscles.
• The extensor retinaculum is a thickening of deep fascia that stretches across the back of the wrist and holds the long extensor tendons in position.
• The anterior surface of each finger, from the head of the metacarpal to the base of the distal phalanx, is provided with a strong fibrous sheath that is attached to the sides of the phalanges.
• Muscles of the hand include: 4 lumbrical muscles, 8 interossei muscles, muscles of thumb (Thenar muscles), muscles of little finger (Hypothenar muscles).
• Muscles of the thumb are supplied by median nerve, except adductor pollicis (Ulnar nerve).
• 1st & 2nd lumbricals are supplied by median nerve, while 3rd & 4th by ulnar nerve.
• Interossei are supplied by ulnar nerve.
• Palmaris brevis is attached to the flexor retinaculum, palmar aponeurosis, and skin of palm, and its nerve supply is the superficial branch of ulnar nerve, corrugating the skin to improve grip of palm.
• Lumbricals (4) are attached to the tendons of flexor digitorum profundus and extend the fingers except thumb.
• Interossei (8) are attached to the proximal phalanges of thumb and index, ring, and little fingers and the dorsal extensor expansion of each finger.
• On the posterior surface of each finger, the extensor tendon joins a fascial expansion called the extensor expansion.
• The ulnar artery enters the hand above the flexor retinaculum and forms the superficial palmar arch, which is completed on the other side by the superficial palmar branch of radial artery.
• The ulnar artery gives off one proper palmar digital artery to the medial side of the little finger and three common palmar digital arteries.
• The radial artery leaves the dorsum of the hand by turning between the first and second metacarpal bones and forms the deep palmar arch which is completed on the other side by the deep palmar branch of ulnar artery.
• The radial artery gives off the princeps pollicis artery and the radialis indicis artery.
• The deep palmar arch of the radial artery consists of three palmar metacarpal arteries that anastomose with the common palmar digital arteries of the superficial palmar arch.
• The dorsal venous arch, cephalic vein, and basilic vein are the main veins of the hand.
• The median nerve enters the palm by passing behind the flexor retinaculum and through the carpal tunnel.
• The median nerve gives off a muscular (recurrent) branch that supplies muscles of the thenar eminence and the first and second lumbrical muscles, three proper palmar digital nerves, and two common palmar digital nerves.
• The muscular (recurrent) branch of the median nerve is the most lateral branch that supplies muscles of the thenar eminence and the first lumbrical muscle.
• The cutaneous branches of the median nerve supply the palmar aspect of the lateral three and a half fingers and the distal half of the dorsal aspect of each finger.
• The ulnar nerve enters the palm anterior to the flexor retinaculum and divides into a superficial and a deep branch as it crosses the retinaculum.
• The superficial branch of the ulnar nerve gives off one common palmar digital nerve and one proper palmar digital nerve to the medial side of the little finger.
• The cutaneous branches of the ulnar nerve supply the palmar aspect of the medial one and a half finger and the distal half of the dorsal aspect of each finger.