Surface Anatomy of Forearm, Wrist & Hand PDF

Surface Anatomy of Forearm & wrist By : Fatemeh Zare October 2024 1 Skeletal surface landmarks The posterior border of the ulna is subcutaneous throughout its whole extent from the subcutaneous surface of the olecranon superiorly to...

Surface Anatomy of Forearm & wrist By : Fatemeh Zare October 2024 1 Skeletal surface landmarks The posterior border of the ulna is subcutaneous throughout its whole extent from the subcutaneous surface of the olecranon superiorly to the styloid process below. Its position corresponds to the longitudinal furrow which can be seen on the posterior aspect of the forearm when the elbow is fully flexed and which separates the flexor group of muscles from the extensors. In contrast, the shaft of the radius can only be felt indistinctly because of its covering of muscles. 2 Skeletal surface landmarks The rounded head of the ulna forms a surface elevation on the medial part of the posterior aspect of the wrist when the hand is pronated. The styloid process of the ulna projects distally from the posteromedial aspect of the head. Loading… Ulnar head 3 Skeletal surface landmarks The expanded lower end of the radius forms a slight surface elevation on the lateral side of the wrist and can be traced downwards into the styloid process of the radius. The posterior aspect of the lower end of the radius is partly obscured by the extensor tendons but can be palpated without difficulty. It presents a tubercle (of Lister), which is grooved on its ulnar aspect by the tendon of extensor pollicis longus. The tubercle lies in line with the cleft between the index and the middle fingers. 4 Skeletal surface landmarks The styloid process of the ulna lies at higher level and on a more posterior plane than the styloid process of the radius. The relative positions of these two bony points can be determined if the wrist is grasped firmly between the finger and thumb and pressure Loading… is applied in a proximal direction. In a fracture of the lower end of the radius with proximal and posterior displacement (Colles' fracture), the two styloid processes come to lie in the same plane. 5 Skeletal surface landmarks bones of the carpus that can be palpated and identified: The pisiform bone forms an elevation which can be both seen and felt on the palmar aspect of the wrist at the base of the hypothenar eminence. It can be moved over the articular surface of the triquetral bone when the wrist is passively flexed. 6 Skeletal surface landmarks bones of the carpus that can be palpated and identified: The hook of the hamate lies 2.5 cm distal to the pisiform and is in line with the ulnar border of the ring finger. It can be felt by deep pressure in this situation and here the superficial division of the ulnar nerve can be rolled from side to side over the tip of the hook. 7 Skeletal surface landmarks bones of the carpus that can be palpated and identified: The tubercle of the scaphoid bone is situated at the base of the thenar eminence. In many subjects it forms a small visible elevation. Immediately distal to it but covered by muscles of the thenar eminence, the crest of the trapezium can be identified on deep pressure. The scaphoid and trapezium can also be palpated in the anatomical snuffbox. 8 Skeletal surface landmarks The wrist joint is easily identified between the carpus and the distal ends of the radius and ulna on flexion and extension of the wrist, even though it is covered by tendons. The line of the wrist joint corresponds to a line, convex upwards, which joins the styloid process of the radius to that of the ulna. It is delineated by the proximal of the two transverse anterior wrist skin creases. 9  Soft tissues The cubital fossa forms a depression in the middle of the upper part of the front of the forearm. Medial border: pronator teres Lateral border: brachioradialis Superior border 10  Soft tissues Brachioradialis is the most superficial of the muscles on the lateral side of the forearm. It can be demonstrated by flexing the elbow in the semi prone position against resistance, when it stands out as Loading… a prominent ridge which extends upwards beyond the level of the elbow joint on the lateral side of the arm. 11  Soft tissues Shafts of the radius and ulna are covered by the bellies of the flexor and extensor groups of muscles of the forearm respectively. The longitudinal furrow which corresponds to the posterior border of the ulna indicates the line which separates these two groups of muscles. More distally, many of the tendons of these two muscle groups can be identified individually. 12  Soft tissues Shafts of the radius and ulna are covered by the bellies of the flexor and extensor groups of muscles of the forearm respectively. The longitudinal furrow which corresponds to the posterior border of the ulna indicates the line which separates these two groups of muscles. More distally, many of the tendons of these two muscle groups can be identified individually. 13  Soft tissues When the wrist is flexed against resistance, a number of tendons become obvious Flexor digitorum suprficialis 14  Soft tissues When the thumb is fully extended, a depression known as the 'anatomical snuff box' is seen on the lateral aspect of the wrist immediately distal to the radial styloid process. Progressing distally from the styloid the following may be palpated: articular surface of the scaphoid (best felt during alternate ulnar and radial deviation at the wrist) radial aspect of the trapezium expanded base of the first metacarpal (best felt during circumduction of the thumb) 15  Soft tissues extensor pollicis longus tendon If a finger is run along tendon of extensor pollicis longus proximally, the superficial radial nerve can be rolled from side to side as it crosses the tendon. 16  Soft tissues The tendons of the extensors of the wrist can be identified on the back of the carpus when the fist is clenched and relaxed alternately. The tendons of extensor digitorum can readily be seen on the back of the hand when the fingers are fully extended. The tendon of extensor carpi ulnaris can be felt distal to the ulnar styloid as it crosses the wrist when the wrist is extended and deviated to the ulnar side. 17  dorsal head of the ulna Soft tissues radial (Lister’s) tubercle The tendons located within the six extensor compartments of the wrist B are subcutaneous and palpable. Compartment 1 (containing abductor pollicis longus and extensor pollicis brevis) sits over the lateral radius. Regional tenderness to palpation occurs in de Quervain’s tenosynovitis. Compartment 2 (containing extensors carpi radialis longus and brevis) and 3 (containing extensor pollicis longus) flank the lateral and medial sides of the dorsal radial (Lister’s) tubercle, respectively. Compartments 5 (containing extensor digiti minimi) and 6 (containing extensor carpi ulnaris) flank the posterior and medial sides of the ulnar head, respectively. Compartment 4 (containing extensors digitorum and indicis) sits between the ulnar head and compartment 3. 18  Soft tissues The median nerve enters the forearm on the medial side of the termination of the brachial artery and runs vertically downwards in the midline of the limb. At the wrist it lies exactly in the midline and projects from under cover of the palmaris longus tendon on its radial side. Since this tendon may be absent, this is obviously an inconstant landmark. 19  Soft tissues The ulnar nerve in the forearm corresponds to a line drawn from the base of the medial epicondyle of the humerus to the radial side of the pisiform bone. Deep pressure at both these bony landmarks will produce paresthesia. In the lower part of the forearm the line of the nerve lies along the radial side of the tendon of flexor carpi ulnaris. 20  Soft tissues The ulnar artery commences in the midline of the forearm opposite the neck of the radius. In its upper and deepest part of its course in the forearm, it can be represented by a line which passes downwards and medially across the elevation produced by the superficial flexor muscles of the forearm, to reach the radial side of the ulnar nerve at the junction of the upper one-third with the lower two-thirds of the forearm. In the rest of its course in the forearm, the ulnar artery lies along the radial side of the ulnar nerve. 21  Soft tissues The radial artery commences opposite the neck of the radius Biceps on the medial side of the tendon tendon of biceps. It runs downwards and radially through the forearm to the wrist, where its pulsation can be readily felt in the interval between the tendon of flexor carpi radialis on the ulnar side and the lower part of the anterior border of the radius laterally. It then continues distally across the anterior margin of the expanded lower end of the radius, then passes posteriorly, deep to the tendons of abductor pollicis longus and extensor pollicis brevis, to enter the anatomical 'snuffbox' where, once again, its pulsation can be felt. 22  Soft tissues radial artery The upper part of the line which represents the course of the radial artery passes deep to the medial part of the elevation produced by the brachioradialis on the anterior aspect of the forearm. 23  Soft tissues The radial nerve gives off its posterior interosseous branch Biceps at the level of the lateral tendon epicondyle, a finger's breadth to the lateral side of the tendon of the biceps, and then runs distally in a vertical direction. In the middle one-third of the forearm it lies along the radial side of the radial artery. In the lower third it inclines backwards to pass across the tendon of extensor pollicis longus at the wrist (where it can be rolled against the tendon), to be distributed as the cutaneous supply of the radial side of the dorsum of the hand and radial three and a half digits. 24  Soft tissues radial nerve Biceps The posterior interosseous tendon nerve passes downwards and posteriorly to supply all the extensor muscles of the forearm apart from brachioradialis and extensor carpi radialis longus (both supplied by the radial nerve before it divides). The nerve winds to the posterior aspect of the forearm around the lateral side of the radius between the two planes of fibers of the supinator. 25  Soft tissues lateral radial nerve epicondyle Biceps posterior interosseous nerve tendon The origin of the nerve anterior to the lateral epicondyle to a point on the dorsum of the wrist midway between the head of the ulna and the dorsal tubercle of the radius. Here the nerve ends as a flattened pseudoganglion from which filaments are distributed to the ligaments and joints of the carpus. Dorsal Ulnar radial head tubercle 26  Soft tissues radial nerve posterior interosseous nerve Radial An important surgical head landmark is where the posterior interosseous nerve winds round the upper end of the radius. This can be indicated in the following Zone of posterior interosseous manner. nerve winding around radial neck (white): approximately 2.5 Place the index finger of the cm distal to radial head opposite hand on the dorsal aspect of the head of the radius. Align the middle and ring fingers below the index. The ring finger then lies over the nerve; this is important in making an incision for exposure and removal of a fractured head of radius. The incision should not extend more than a finger's breadth below the head of the radius. 27  Soft tissues The flexor retinaculum can be outlined by defining its bony attachments. Its distal border, concave downwards, can be indicated on the surface by a curved line which joins the crest of the trapezium to the hook of the hamate Its proximal border by a curved line concave upwards which joins the tubercle of the scaphoid to the pisiform. 28 Surface Anatomy of hand Loading… 29 Skeletal surface landmarks The heads of the metacarpal bones form the prominence of the knuckles, that of the middle finger being the most prominent. Their convex, palmar aspects can be felt on deep pressure over the fronts of the metacarpophalangeal joints and can be gripped knuckle between the finger and the thumb. Deep pressure over the distal aspect of the head of the metacarpal bone reveals the base of the corresponding proximal phalanx. the line of the metacarpophalangeal joint can be detected on the dorsum of the hand as the fingers are flexed and extended. 30  Skeletal surface landmarks The dorsal aspects of the shafts of the metacarpal bones of the fingers and thumb and trapezium can be felt rather indistinctly, being obscured by the extensor tendons. The interphalangeal joints can be felt on the dorsal aspect of the flexed finger, just distal to the prominences caused by the heads of the proximal and middle phalanges. 31  Soft tissues The skin of the palm of the band is marked by a number of creases which, however, are of little value as points of reference. The thenar eminence is a fleshy elevation induced by the abductor and the flexor pollicis brevis, which overlie the opponens pollicis. The hypothenar eminence on the medial side of the palm-is formed by the corresponding muscles of the little finger but is not so prominent. 32  Soft tissues The medial border of the hand is formed by the medial aspect of the hypothenar eminence The lateral border is formed by the dorsal aspect of the metacarpal bone of the thumb which can be palpated throughout its whole extent and, at its base The carpometacarpal joint of the thumb can be indistinctly palpated on its dorsal aspect. The wide range of movement at this saddle joint can be appreciated. 33  Soft tissues Transverse skin creases cross the palmar aspects of the fingers in three situations: The most proximal crease is placed at the junction of the digit with the palm and lies nearly 2 cm distal to the metacarpophalangeal joint The intermediate crease lies opposite the proximal interphalangeal joint The distal crease is placed just proximal to the distal interphalangeal joint. 34  Soft tissues The lateral part of the dorsal aspect of the hand between the index finger and the thumb shows a fleshy elevation caused by the first dorsal interosseous muscle, which becomes more conspicuous when the index finger is abducted against resistance. The corresponding anterior aspect of the first web space is formed by adductor pollicis. 35  Soft tissues The superficial palmar arch is continuous with the ulnar artery which lies to the radial side of the pisiform. Its course can be marked out by a line drawn downwards in front of the hook of the hamate bone which then curves radially with a downward convexity across the palm to the thenar eminence. The most distal part of the curve reaches the level of the palmar surface of the extended thumb. However, the curvature of this vessel is subject to considerable variation. The deep palmar arch can be represented by a line about 1.5 cm proximal to the superficial arch. 36  Soft tissues On the back of the hand is the irregular plexus of the dorsal venous arch. Its position and arrangement are both highly variable: from its ulnar side originates the basilic vein, which ascends along the ulnar side of the distal forearm. The cephalic vein arises from the radial extremity of the dorsal arch; at the wrist level it can be felt and seen (if the forearm is compressed) immediately dorsal to the radial styloid process after crossing the roof of the anatomical 'snuffbox'. This site is commonly and safely used for intravenous cannulation. 37 Thanks for your attention 38