Overview Of Upper Limb PDF

672 Chapter 6 Upper Limb OVERVIEW OF UPPER LIMB It includes the pectoral, scapular, and deltoid regions of the upper limb, an...

672 Chapter 6 Upper Limb OVERVIEW OF UPPER LIMB It includes the pectoral, scapular, and deltoid regions of the upper limb, and the lateral part (greater supracla- vicular fossa) of the lateral cervical region. It overlies half The upper limb is characterized by its mobility and ability to of the pectoral girdle. The pectoral girdle (shoulder grasp, strike, and conduct fine motor skills (manipulation). girdle) is a bony ring, incomplete posteriorly, formed by These characteristics are especially marked in the hand when the scapulae and clavicles, and completed anteriorly by performing manual activities, such as buttoning a shirt. the manubrium of the sternum (part of the axial skeleton). Synchronized interplay occurs between the joints of the 2. Arm (L. brachium): first segment of the free upper limb upper limb to coordinate the intervening segments to per- (more mobile part of the upper limb independent of the form smooth, efficient motion at the most workable distance trunk) and the longest segment of the limb. It extends or position required for a specific task. Efficiency of hand between and connects the shoulder and the elbow, and function results in large part from the ability to place it in consists of anterior and posterior regions of the arm, the proper position by movements at the scapulothoracic, centered around the humerus. glenohumeral, elbow, radio-ulnar, and wrist joints. 3. Forearm (L. antebrachium): second longest segment of The upper limb consists of four major segments, which the limb. It extends between and connects the elbow and are further subdivided into regions for precise description wrist and includes anterior and posterior regions of (Figs. 6.1 and 6.2): the forearm overlying the radius and ulna. 1. Shoulder: proximal segment of the limb that overlaps parts of the trunk (thorax and back) and lower lateral neck. 1/2 Pectoral girdle 2 1 Clavicle Acromioclavicular joint 3 5 Glenohumeral 6 (shoulder) joint Scapula Humerus 8 Arm 10 Anterior view 12 14 1 Elbow 4 joint Proximal 16 Radius 5 radio-ulnar joint Forearm Ulna 7 Distal Wrist radio-ulnar (radio- joint Posterior view carpal) 9 joint Carpus Regions of upper limb: Midcarpal 11 joint Metacarpus 1. Deltoid 9. Posterior elbow 2. Clavipectoral 10. Anterior forearm Hand triangle 11. Posterior forearm Phalanges 3. Pectoral 12. Anterior wrist 13 Carpo- 4. Scapular 13. Posterior wrist metacarpal 5. Axillary 14. Palm/palmar 15 joint 6. Anterior arm 15. Dorsum of hand Metacarpo- 7. Posterior arm 16. Digits (fingers 16 phalangeal Interphalangeal joints 8. Cubital including thumb) joints Anterior view FIGURE 6.1. Segments and bones of upper limb. The joints divide the FIGURE 6.2. Regions of upper limb. For exact description, the upper superior appendicular skeleton, and thus the limb itself, into four main seg- limb is divided into regions based on the external features (surface ments: shoulder, arm, forearm, and hand. anatomy) of the underlying muscular formations, bones, and joints. Moore_Chap06.indd 672 12/10/2012 6:00:59 PM  Chapter 6 Upper Limb 673 4. Hand (L. manus): part of the upper limb distal to the Although the paired bones of both the leg and forearm flex forearm that is formed around the carpus, metacarpus, and extend as a unit, only those of the upper limb are able and phalanges. It is composed of the wrist, palm, dor- to move (supinate and pronate) relative to each other; the sum of hand, and digits (fingers, including an opposable bones of the leg are fixed in the pronated position. thumb), and is richly supplied with sensory endings for The wrist and ankle have a similar number of short bones touch, pain, and temperature. (eight and seven, respectively). Both groups of short bones interrupt a series of long bones that resumes distally with several sets of long bones of similar lengths, with a similar COMPARISON OF UPPER number of joints of essentially the same type. The digits of the upper limb (fingers including the thumb) are the most AND LOWER LIMBS mobile parts of either limb. However, all other parts of the upper limb are more mobile than the comparable parts of Developing in a similar fashion, the upper and lower limbs the lower limb. share many common features (see Chapter 5). However, they are sufficiently distinct in structure to enable markedly dif- ferent functions and abilities. Because the upper limb is not BONES OF UPPER LIMB usually involved in weight bearing or motility, its stability has been sacrificed to gain mobility. The upper limb still possesses The pectoral girdle and bones of the free part of the upper limb remarkable strength; and because of the hand’s ability to con- form the superior appendicular skeleton (Fig. 6.3); the pel- form to a paddle or assume a gripping or platform configura- vic girdle and bones of the free part of the lower limb form the tion, it may assume a role in motility in certain circumstances. inferior appendicular skeleton. The superior appendicular Both the upper and the lower limbs are connected to skeleton articulates with the axial skeleton only at the sterno- the axial skeleton (cranium, vertebral column, and associ- clavicular joint, allowing great mobility. The clavicles and scap- ated thoracic cage) via the bony pectoral and pelvic girdles, ulae of the pectoral girdle are supported, stabilized, and moved respectively. The pelvic girdle consists of the two hip bones by axio-appendicular muscles that attach to the relatively connected to the sacrum (see Chapter 5). The pectoral gir- fixed ribs, sternum, and vertebrae of the axial skeleton. dle consists of the scapulae and clavicles, connected to the manubrium of the sternum. Both girdles possess a large flat bone located posteriorly, which provides for attachment of Clavicle proximal muscles, and connects with its contralateral partner The clavicle (collar bone) connects the upper limb to the anteriorly via small bony braces, the pubic rami and clavicles. trunk (Figs. 6.3 and 6.4). The shaft of the clavicle has a However, the flat iliac bones of the pelvic girdle are also con- double curve in a horizontal plane. Its medial half is con- nected posteriorly through their primary attachment to the vex anteriorly, and its sternal end is enlarged and triangular sacrum via the essentially rigid, weight-transferring sacro-iliac where it articulates with the manubrium of the sternum at the joints. This posterior connection to the axial skeleton places sternoclavicular (SC) joint. Its lateral half is concave anteri- the lower limbs inferior to the trunk, enabling them to be orly, and its acromial end is flat where it articulates with the supportive as they function primarily in relation to the line of acromion of the scapula at the acromioclavicular (AC) joint gravity. Furthermore, because the two sides are connected (Figs. 6.3B and 6.4). The medial two thirds of the shaft of both anteriorly and posteriorly, the pelvic girdle forms a com- the clavicle are convex anteriorly, whereas the lateral third is plete rigid ring that limits mobility, making the movements flattened and concave anteriorly. These curvatures increase of one limb markedly affect the movements of the other. The the resilience of the clavicle, and give it the appearance of an pectoral girdle, however, is connected to the trunk only ante- elongated capital S. riorly, via the sternum, by flexible joints with 3 degrees of The clavicle: freedom. It is an incomplete ring because the scapulae are not Serves as a moveable, crane-like strut (rigid support) from connected with each other posteriorly. Thus, the motion of which the scapula and free limb are suspended, keeping one upper limb is independent of the other, and the limbs are them away from the trunk so that the limb has maximum able to operate effectively anterior to the body, at a distance freedom of motion. The strut is movable and allows the and level that enable precise eye–hand coordination. scapula to move on the thoracic wall at the “scapulotho- In both the upper and the lower limbs, the long bone of racic joint,”1 increasing the range of motion of the limb. the most proximal segment is the largest and is unpaired. The long bones increase progressively in number but decrease in 1 The scapulothoracic joint is a physiological “joint,” in which movement size in the more distal segments of the limb. The second most occurs between musculoskeletal structures (between the scapula and associ- proximal segment of both limbs (i.e., the leg and forearm) ated muscles and the thoracic wall), rather than an anatomical joint, in which has two parallel bones, although only in the forearm do both movement occurs between directly articulating skeletal elements. The scapu- articulate with the bone of the proximal segment, and only lothoracic joint is where the scapular movements of elevation–depression, in the leg do both articulate directly with the distal segment. protraction–retraction, and rotation occur. Moore_Chap06.indd 673 12/10/2012 6:01:01 PM  674 Chapter 6 Upper Limb Superior border Spine of scapula Coracoid process Superior angle Acromioclavicular joint Acromial end of clavicle Acromion of scapula Sternal Acromion Clavicle end Acromial angle Lesser tubercle Supraspinous Greater tubercle fossa Greater tubercle Head of scapula Scapula Intertubercular sulcus Scapula Suprascapular notch Head of humerus (bicipital groove) Neck of scapula Surgical neck Surgical neck of humerus Medial border Anatomical neck Body of scapula Infraspinous of humerus fossa Lateral Subscapular Lateral Deltoid tuberosity Deltoid tuberosity border fossa border Radial groove Inferior angle Shaft of humerus Shaft of Humerus Humerus humerus Lateral supra-epicondylar Medial supra-epicondylar ridge ridge Medial supra- Lateral supra- Radial fossa Coronoid fossa epicondylar ridge epicondylar Lateral epicondyle ridge Medial epicondyle Capitulum Lateral Trochlea epicondyle Medial epicondyle Head of radius Coronoid process Head of radius Neck of radius Tuberosity of radius Tuberosity of ulna Olecranon articulating with olecranon fossa of humerus Posterior Anterior oblique line oblique line Posterior border Ulna Ulna Shaft of radius Radius Shaft of ulna Radius Dorsal Head of ulna articulating with Head of ulna tubercle ulnar notch of radius of radius Styloid process Styloid process Styloid process of ulna Styloid of radius Carpal bones process Carpal bones of radius Metacarpal bones Metacarpal bones Proximal Proximal phalanx phalanx Proximal (first) Proximal (first) Distal Distal phalanx Middle (second) Phalanges Middle (second) phalanx Distal (third) Distal (third) (A) Anterior view (B) Posterior view FIGURE 6.3. Bones of upper limb. Moore_Chap06.indd 674 12/10/2012 6:01:01 PM  Chapter 6 Upper Limb 675 Sternal end Anterior Shaft the 2nd–7th ribs (see Fig. I.11, p. 20). The convex poste- Acromial end rior surface of the scapula is unevenly divided by a thick projecting ridge of bone, the spine of the scapula, into a small supraspinous fossa and a much larger infraspinous Posterior fossa (Fig. 6.5A). The concave costal surface of most of the scapula forms a large subscapular fossa. The broad bony Sternal facet Superior surface surfaces of the three fossae provide attachments for fleshy (articular surface) muscles. The triangular body of the scapula is thin and Conoid tubercle translucent superior and inferior to the spine of the scapula; although its borders, especially the lateral one, are somewhat Posterior thicker. The spine continues laterally as the flat, expanded acromion (G. akros, point), which forms the subcutaneous Trapezoid point of the shoulder and articulates with the acromial end Impression for Anterior Subclavian line of the clavicle. The deltoid tubercle of the scapular spine costoclavicular groove Acromial facet ligament (articular surface) is the prominence indicating the medial point of attachment Inferior surface of the deltoid. The spine and acromion serve as levers for the attached muscles, particularly the trapezius. FIGURE 6.4. Right clavicle. Prominent features of the superior and infe- rior surfaces of the clavicle. The bone acts as a mobile strut (supporting Because the acromion is a lateral extension of the scapula, brace) connecting the upper limb to the trunk; its length allows the limb to the AC joint is placed lateral to the mass of the scapula and its pivot around the trunk. attached muscles (Fig. 6.5C). The glenohumeral (shoulder) joint on which these muscles operate is almost directly infe- rior to the AC joint; thus the scapular mass is balanced with Fixing the strut in position, especially after its elevation, that of the free limb, and the suspending structure (coraco- enables elevation of the ribs for deep inspiration. clavicular ligament) lies between the two masses. Forms one of the bony boundaries of the cervico-axillary Superolaterally, the lateral surface of the scapula has a canal (passageway between the neck and arm), afford- glenoid cavity (G. socket), which receives and articulates ing protection to the neurovascular bundle supplying the with the head of the humerus at the glenohumeral joint upper limb. (Fig. 6.5A & C). The glenoid cavity is a shallow, concave, oval Transmits shocks (traumatic impacts) from the upper fossa (L. fossa ovalis), directed anterolaterally and slightly limb to the axial skeleton. superiorly—that is considerably smaller than the ball (head Although designated as a long bone, the clavicle has no of the humerus) for which it serves as a socket. The beak- medullary (marrow) cavity. It consists of spongy (trabecular) like coracoid process (G. korak-odés, like a crow’s beak) is bone with a shell of compact bone. superior to the glenoid cavity, and projects anterolaterally. The superior surface of the clavicle, lying just deep to This process also resembles in size, shape, and direction a the skin and platysma (G. flat plate) muscle in the subcutane- bent finger pointing to the shoulder, the knuckle of which ous tissue, is smooth. provides the inferior attachment for the passively supporting The inferior surface of the clavicle is rough because coracoclavicular ligament. strong ligaments bind it to the 1st rib near its sternal end The scapula has medial, lateral, and superior borders and and suspend the scapula from its acromial end. The conoid superior, lateral, and inferior angles (Fig. 6.5B). When the tubercle, near the acromial end of the clavicle (Fig. 6.4), scapular body is in the anatomical position, the thin medial gives attachment to the conoid ligament, the medial part of border of the scapula runs parallel to and approximately the coracoclavicular ligament by which the remainder of the 5 cm lateral to the spinous processes of the thoracic verte- upper limb is passively suspended from the clavicle. Also, brae; hence it is often called the vertebral border (Fig. 6.5B). near the acromial end of the clavicle is the trapezoid line, From the inferior angle, the lateral border of the scapula to which the trapezoid ligament attaches; it is the lateral part runs superolaterally toward the apex of the axilla; hence it is of the coracoclavicular ligament. often called the axillary border. The lateral border is made The subclavian groove (groove for the subclavius) in the up of a thick bar of bone that prevents buckling of this stress- medial third of the shaft of the clavicle is the site of attachment bearing region of the scapula. of the subclavius muscle. More medially is the impression The lateral border terminates in the truncated lateral for the costoclavicular ligament, a rough, often depressed, angle of the scapula, the thickest part of the bone that oval area that gives attachment to the ligament binding the 1st bears the broadened head of the scapula (Fig. 6.5A & B). rib (L. costa) to the clavicle, limiting elevation of the shoulder. The glenoid cavity is the primary feature of the head. The shallow constriction between the head and body defines the neck of the scapula. The superior border of the scapula is Scapula marked near the junction of its medial two thirds and lateral The scapula (shoulder blade) is a triangular flat bone that third by the suprascapular notch, which is located where lies on the posterolateral aspect of the thorax, overlying the superior border joins the base of the coracoid process. Moore_Chap06.indd 675 12/10/2012 6:01:03 PM  676 Chapter 6 Upper Limb Superior angle Facet for clavicle Supraspinous fossa Suprascapular notch Superior Coracoid process border Acromion Acromion Acromion Acromial Coracoid Crest of spine angle process Lateral Head of scapula Medial angle Glenoid Neck of scapula border cavity Spine of scapula Lateral border Deltoid tubercle of spine Subscapular fossa Infraspinous Inferior fossa angle (A) Costal surface Posterior surface (B) Posterior surface Clavicle (suspending strut) Acromioclavicular (AC) joint Acromioclavicular joint Supraglenoid Clavicular joint tubercle Coracoclavicular Acromion ligament Coracoclavicular ligament (suspending device and Supraspinous Coracoid point of balance) fossa process Head of humerus Spine Infraglenoid tubercle Glenohumeral joint Infraspinous fossa Scapula Scapular Mass of mass free limb Lateral border of scapula Inferior angle (C) Posterior view Lateral view FIGURE 6.5. Right scapula. A. The bony features of the costal and posterior surfaces of the scapula. B. The borders and angles of the scapula. C. The scapula is suspended from the clavicle by the coracoclavicular ligament, at which a balance is achieved among the weight of the scapula and its attached muscles plus the muscular activity medially and the weight of the free limb laterally. The superior border is the thinnest and shortest of the three The junction of the head and neck with the shaft of the borders. humerus is indicated by the greater and lesser tubercles, The scapula is capable of considerable movement on the which provide attachment and leverage to some scapulo- thoracic wall at the physiological scapulothoracic joint, pro- humeral muscles (Fig. 6.3A & B). The greater tubercle viding the base from which the upper limb operates. These is at the lateral margin of the humerus, whereas the lesser movements, enabling the arm to move freely, are discussed tubercle projects anteriorly from the bone. The intertu- later in this chapter with the muscles that move the scapula. bercular sulcus (bicipital groove) separates the tubercles, and provides protected passage for the slender tendon of the long head of the biceps muscle. Humerus The shaft of the humerus has two prominent features: The humerus (arm bone), the largest bone in the upper the deltoid tuberosity laterally, for attachment of the del- limb, articulates with the scapula at the glenohumeral joint, toid muscle, and the oblique radial groove (groove for and the radius and ulna at the elbow joint (Figs. 6.1, 6.3, and radial nerve, spiral groove) posteriorly, in which the radial 6.5C). The proximal end of the humerus has a head, surgical nerve and profunda brachii artery lie as they pass anterior to and anatomical necks, and greater and lesser tubercles. The the long head and between the medial and the lateral heads spherical head of the humerus articulates with the glenoid of the triceps brachii muscle. The inferior end of the humeral cavity of the scapula. The anatomical neck of the humerus shaft widens as the sharp medial and lateral supra-epicon- is formed by the groove circumscribing the head and sepa- dylar (supracondylar) ridges form, and then end distally in rating it from the greater and lesser tubercles. It indicates the especially prominent medial epicondyle and the lat- the line of attachment of the glenohumeral joint capsule. The eral epicondyle, providing for muscle attachment. surgical neck of the humerus, a common site of fracture, The distal end of the humerus—including the trochlea, is the narrow part distal to the head and tubercles (Fig. 6.3B). capitulum, olecranon, coronoid, and radial fossae—makes Moore_Chap06.indd 676 12/10/2012 6:01:03 PM  Chapter 6 Upper Limb 677 Lateral Medial supra-epicondylar ridge Lateral supra-epicondylar supra-epicondylar ridge Humerus Humerus ridge *Radial fossa *Coronoid fossa *Olecranon fossa Lateral epicondyle Medial Medial Lateral Flexors Extensors for extensors epicondyle epicondyle epicondyle for flexors for Ulnar nerve Anconeus for *Capitulum *Trochlea *Trochlea *Parts of condyle of humerus (A) Anterior view (B) Posterior view FIGURE 6.6. Distal end of right humerus. A and B. The condyle (the boundaries of which are indicated by the dashed line) consists of the capitulum; the trochlea; and the radial, coronoid, and olecranon fossae. up the condyle of the humerus (Fig. 6.6). The condyle has Bones of Forearm two articular surfaces: a lateral capitulum (L. little head) for articulation with the head of the radius, and a medial, The two forearm bones serve together to form the second unit spool-shaped or pulley-like trochlea (L. pulley) for articu- of an articulated mobile strut (the first unit being the humerus), lation with the proximal end (trochlear notch) of the ulna. with a mobile base formed by the shoulder, that positions the Two hollows, or fossae, occur back to back superior to the hand. However, because this unit is formed by two parallel trochlea, making the condyle quite thin between the epicon- bones, one of which (the radius) can pivot about the other (the dyles. Anteriorly, the coronoid fossa receives the coronoid ulna), supination and pronation are possible. This makes it pos- process of the ulna during full flexion of the elbow. Posteri- sible to rotate the hand when the elbow is flexed. orly, the olecranon fossa accommodates the olecranon of ULNA the ulna during full extension of the elbow. Superior to the capitulum anteriorly, a shallower radial fossa accommo- The ulna is the stabilizing bone of the forearm and is the dates the edge of the head of the radius when the forearm medial and longer of the two forearm bones (Figs. 6.7 and 6.8). is fully flexed. Its more massive proximal end is specialized for articulation Olecranon Trochlear notch Coronoid Ulna process Radial notch Humerus Tuberosity Supinator of ulna Radius crest Supinator Ulna fossa (C) Flexion Shaft (body) Interosseous border (A) Proximal end of ulna (B) Extension Lateral views FIGURE 6.7. Bones of right elbow region. A. The proximal part of the ulna. B. The bones of the elbow region, demonstrating the relationship of the distal humerus and proximal ulna and radius during extension of the elbow joint. C. The relationship of the humerus and forearm bones during flexion of the elbow joint. Moore_Chap06.indd 677 12/10/2012 6:01:04 PM  678 Chapter 6 Upper Limb Olecranon with the humerus proximally, and the head of the radius lat- Trochlear erally. For articulation with the humerus, the ulna has two notch prominent projections: (1) the olecranon, which projects Head Coronoid proximally from its posterior aspect (forming the point of the Neck process elbow), and serves as a short lever for extension of the elbow, Radial Tuberosity tuberosity and (2) the coronoid process, which projects anteriorly. of ulna The olecranon and coronoid processes form the walls of Shafts the trochlear notch, which in profile resembles the jaws of a Radius Radius crescent wrench as it “grips” (articulates with) the trochlea of Interosseous the humerus (Fig. 6.7B & C). The articulation between the membrane ulna and humerus primarily allows only flexion and extension Level of section in E of the elbow joint, although a small amount of abduction– Articular adduction occurs during pronation and supination of the Head of circumference ulna in ulnar forearm. Inferior to the coronoid process is the tuberosity of head notch of of the ulna for attachment of the tendon of the brachialis of ulna radius muscle (Fig. 6.7A and 6.8A & B). Styloid Styloid Styloid On the lateral side of the coronoid process is a smooth, process process process of radius of ulna of radius rounded concavity, the radial notch, which receives the broad periphery of the head of the radius. Inferior to the (A) Anterior view (B) Posterior view radial notch on the lateral surface of the ulnar shaft is a prom- inent ridge, the supinator crest. Between it and the distal Groove for extensor Groove for extensor pollicis longus part of the coronoid process is a concavity, the supinator digitorum and fossa. The deep part of the supinator muscle attaches to the extensor indicis Dorsal tubercle of radius supinator crest and fossa (6.7A). Ulnar notch Groove for extensor The shaft of the ulna is thick and cylindrical proximally, carpi radialis longus but it tapers, diminishing in diameter, as it continues distally Styloid process and brevis (Fig. 6.8A). At the narrow distal end of the ulna is a small (C) Posterior view of distal end of radius but abrupt enlargement, the disc-like head of the ulna with a small, conical ulnar styloid process. The ulna does not reach—and therefore does not participate in—the wrist Styloid Grooves for tendons Dorsal process tubercle (radiocarpal) joint (Fig. 6.8). of ulna of radius For Styloid RADIUS Head of ulna articular For For process disc lunate scaphoid of radius The radius is the lateral and shorter of the two forearm Distal radio-ulnar joint Radius bones. Its proximal end includes a short head, neck, and medially directed tuberosity (Fig. 6.8A). Proximally, the (D) Inferior view of distal ends of ulna and radius smooth superior aspect of the discoid head of the radius is Border Posterior concave for articulation with the capitulum of the humerus Border during flexion and extension of the elbow joint. The head also Surface Interosseous Surface articulates peripherally with the radial notch of the ulna; thus Medial borders Lateral the head is covered with articular cartilage. Ulna Radius surface Interosseous surface The neck of the radius is a constriction distal to the head. Surface membrane Surface The oval radial tuberosity is distal to the medial part of the Border Anterior Border neck, and demarcates the proximal end (head and neck) of the radius from the shaft. (E) Inferior view of cross section through shafts of the ulna and radius and interosseous membrane The shaft of the radius, in contrast to that of the ulna, gradually enlarges as it passes distally. The distal end of FIGURE 6.8. Right radius and ulna. A and B. The radius and ulna are the radius is essentially four sided when sectioned trans- shown in the articulated position, connected by the interosseous mem- brane. C and D. The features of the distal ends of the forearm bones. versely. Its medial aspect forms a concavity, the ulnar notch E. In cross section, the shafts of the radius and ulna appear almost as (Fig. 6.8C & D), which accommodates the head of the ulna. mirror images of one another for much of the middle and distal thirds Its lateral aspect becomes increasingly ridge-like, terminat- of their lengths. ing distally in the radial styloid process. Projecting dorsally, the dorsal tubercle of the radius lies between otherwise shallow grooves for the passage of the tendons of forearm muscles. The radial styloid process Moore_Chap06.indd 678 12/10/2012 6:01:06 PM  Chapter 6 Upper Limb 679 is larger than the ulnar styloid process, and extends farther of the interosseous membrane run an oblique course, pass- distally (Fig. 6.8A & B). This relationship is of clinical impor- ing inferiorly from the radius as they extend medially to the tance when the ulna and/or the radius is fractured. ulna (Fig. 6.8A & B). Thus, they are positioned to transmit Most of the length of the shafts of the radius and ulna forces received by the radius (via the hands) to the ulna for are essentially triangular in cross section, with a rounded, transmission to the humerus. superficially directed base and an acute, deeply directed apex (Fig. 6.8A & E). The apex is formed by a section of Bones of Hand the sharp interosseous border of the radius or ulna that connects to the thin, fibrous interosseous membrane of The wrist, or carpus, is composed of eight carpal bones, the forearm (Fig. 6.8A, B, & E). The majority of the fibers arranged in proximal and distal rows of four (Fig. 6.9A–C). Distal Distal phalanx Phalanges Middle Head of middle phalanx Proximal Head of proximal phalanx Head Head Shaft Head Tubercle Capitate (C) Base 2 3 4 5th metacarpal Shaft Shaft 1 5 Base Trapezoid (Td) 1st metacarpal Base Trapezoid Capitate Hook of hamate Trapezium (Tz) Hamate (H) Tubercle Pisiform (P) of trapezium Triquetrum Triquetrum (Tq) Scaphoid (S) Carpal bones Lunate (L) Tubercle Lunate of scaphoid Distal row (A) Anterior (palmar) view Proximal row (B) Posterior (dorsal) view Sesamoid bone Td Tz H C Tq S 3 2 4 H L R 5 C 1 Tq L U H Tz R Tq C P S L (D) (E) R (C) U C – E. Anteroposterior views FIGURE 6.9. Bones of right hand. A–C. The skeleton of the hand consists of three segments: the carpals of the wrist (subdivided into proximal and distal rows), the metacarpals of the palm, and the phalanges of the fingers or digits. U, ulna; R, radius. D. The distal end of the forearm and hand of a 2.5-year- old child. Ossification centers of only four carpal bones are visible. Observe the distal radial epiphysis (R). E. The distal end of the forearm and hand of an 11-year-old child. Ossification centers of all carpal bones are visible. The arrow indicates the pisiform lying on the anterior surface of the triquetrum. The distal epiphysis of the ulna has ossified, but all the epiphyseal plates (lines) remain open (i.e., they are still unossified). (Parts C and D courtesy of Dr. D. Armstrong, Associate Professor of Medical Imaging, University of Toronto, Toronto, Ontario, Canada.). Moore_Chap06.indd 679 12/10/2012 6:01:07 PM  680 Chapter 6 Upper Limb These small bones give flexibility to the wrist. The carpus is largest, the middle ones are intermediate in size, and the dis- markedly convex from side to side posteriorly, and concave tal ones are the smallest. The shafts of the phalanges taper anteriorly. Augmenting movement at the wrist joint, the two distally. The terminal phalanges are flattened and expanded rows of carpal bones glide on each other; in addition, each at their distal ends, which underlie the nail beds. bone glides on those adjacent to it. From lateral to medial, the four carpal bones in the proxi- OSSIFICATION OF BONES OF HAND mal row (purple in Fig. 6.9A & B) are the: Radiographs of the wrist and hand are commonly used to Scaphoid (G. skaphé, skiff, boat): a boat-shaped bone assess skeletal age. For clinical studies, the radiographs are that articulates proximally with the radius, and has a compared with a series of standards in a radiographic atlas of prominent scaphoid tubercle; it is the largest bone in skeletal development to determine the skeletal age. Ossifica- the proximal row of carpals. tion centers are usually obvious during the 1st year; however, Lunate (L. luna, moon): a moon-shaped bone between the they may appear before birth. Each carpal bone usually ossi- scaphoid and the triquetral bones; it articulates proximally fies from one center postnatally (Fig. 6.9D). The centers for with the radius and is broader anteriorly than posteriorly. the capitate and hamate appear first. Triquetrum (L. triquetrus, three-cornered): a pyramidal The shaft of each metacarpal begins to ossify during fetal bone on the medial side of the carpus; it articulates proxi- life, and ossification centers appear postnatally in the heads mally with the articular disc of the distal radio-ulnar joint. of the four medial metacarpals and in the base of the 1st Pisiform (L. pisum, pea), a small, pea-shaped bone that metacarpal. By age 11, ossification centers of all carpal bones lies on the palmar surface of the triquetrum. are visible (Fig. 6.9E). From lateral to medial, the four carpal bones in the distal row (green in Fig. 6.9A & B) are the: Surface Anatomy of Upper Limb Bones Trapezium (G. trapeze, table): a four-sided bone on the Most bones of the upper limb offer a palpable segment or lateral side of the carpus; it articulates with the 1st and surface (notable exceptions being the lunate and trapezoid), 2nd metacarpals, scaphoid, and trapezoid bones. enabling the skilled examiner to discern abnormalities owing Trapezoid: a wedge-shaped bone that resembles the tra- to trauma (fracture or dislocation) or malformation (Fig. 6.10). pezium; it articulates with the 2nd metacarpal, trapezium, The clavicle is subcutaneous and can be easily palpated capitate, and scaphoid bones. throughout its length. Its sternal end projects superior to the Capitate (L. caput, head): a head-shaped bone with a manubrium (Fig. 6.10). Between the elevated sternal ends of rounded extremity is the largest bone in the carpus; it the clavicles is the jugular notch (suprasternal notch). The articulates primarily with the 3rd metacarpal distally, and acromial end of the clavicle often rises higher than the acro- with the trapezoid, scaphoid, lunate, and hamate. mion, forming a palpable elevation at the acromioclavicular Hamate (L. hamulus, a little hook): a wedge-shaped bone (AC) joint. The acromial end can be palpated 2–3 cm medial on the medial side of the hand; it articulates with the 4th to the lateral border of the acromion, particularly when the and 5th metacarpal, capitate, and triquetral bones; it has a arm is alternately flexed and extended. Either or both ends of distinctive hooked process, the hook of the hamate, that the clavicle may be prominent; when present, this condition extends anteriorly. is usually bilateral. The proximal surfaces of the distal row of carpal bones Note the elasticity of the skin over the clavicle and how articulate with the proximal row of carpal bones, and their easily it can be pinched into a mobile fold. This property of distal surfaces articulate with the metacarpals. the skin is useful when ligating (tying a knot around) the third The metacarpus forms the skeleton of the palm of the part of the subclavian artery: The skin lying superior to the hand between the carpus and the phalanges. It is composed clavicle is pulled down onto the clavicle and then incised; of five metacarpal bones (metacarpals). Each metacarpal after the incision is made, the skin is allowed to return to its consists of a base, shaft, and head. The proximal bases of the position superior to the clavicle, where it overlies the artery metacarpals articulate with the carpal bones, and the distal (thus not endangering it during the incision). heads of the metacarpals articulate with the proximal pha- As the clavicle passes laterally, its medial part can be felt to langes, and form the knuckles of the hand. The 1st metacar- be convex anteriorly. The large vessels and nerves to the upper pal (of the thumb) is the thickest and shortest of these bones. limb pass posterior to this convexity. The flattened acromial The 3rd metacarpal is distinguished by a styloid process on end of the clavicle does not reach the point of the shoulder, the lateral side of its base (Fig. 6.10). formed by the lateral tip of the acromion of the scapula. Each digit (finger) has three phalanges except for the The acromion of the scapula is easily felt and often vis- first (the thumb), which has only two; however, the phalan- ible, especially when the deltoid contracts against resistance. ges of the first digit are stouter than those in the other fin- The superior surface of the acromion is subcutaneous and gers. Each phalanx has a base proximally, a shaft (body), and may be traced medially to the AC joint. The lateral and pos- a head distally (Fig. 6.9). The proximal phalanges are the terior borders of the acromion meet to form the acromial Moore_Chap06.indd 680 12/10/2012 6:01:08 PM  Chapter 6 Upper Limb 681 Jugular notch Manubrium of sternum Superior border Superior border of clavicle of clavicle Acromioclavicular joint Acromion of scapula Acromial angle Acromion of scapula Greater tubercle Greater tubercle of humerus of humerus Crest of scapular spine Lesser tubercle of humerus Medial (vertebral) Coracoid process border of scapula of scapula Inferior angle of scapula Olecranon Lateral epicondyle of humerus Lateral epicondyle (A) Anterior (B) Posterior of humerus Medial epicondyle of humerus Head of radius Lateral border of distal radius Styloid Posterior border process of ulna Lateral border of radius of distal radius Head and styloid Styloid process Tubercle of process of ulna of radius scaphoid Pisiform Head and styloid Capitate process of ulna Hook of hamate Heads of metacarpals Pisiform Tubercle of Styloid trapezium Posterior aspects process Bases, lateral aspects and of metacarpals of 3rd heads of proximal phalanges and phalanges metacarpal Green = palpable features of upper limb bones FIGURE 6.10. Surface anatomy of bones of upper limb. angle (Fig. 6.10B). The humerus in the glenoid cavity and the back of the head, the scapula is rotated, elevating the the deltoid muscle form the rounded curve of the shoulder. glenoid cavity such that the medial border of the scapula The crest of the scapular spine is subcutaneous through- parallels the 6th rib and thus can be used to estimate its posi- out and easily palpated. tion and, deep to the rib, the oblique fissure of the lung. The When the upper limb is in the anatomical position, the: inferior angle of the scapula is easily felt and is often visible. It is grasped when testing movements of the glenohumeral Superior angle of the scapula lies at the level of the joint to immobilize the scapula. The coracoid process of the T2 vertebra. scapula can be felt by palpating deeply at the lateral side of Medial end of the root of the scapular spine is opposite the clavipectoral (deltopectoral) triangle (Fig. 6.11). the spinous process of the T3 vertebra. The head of the humerus is surrounded by muscles, Inferior angle of the scapula lies at the level of the T7 except inferiorly; consequently, it can be palpated only by vertebra, near the inferior border of the 7th rib and 7th pushing the fingers well up into the axillary fossa (armpit). intercostal space. The arm should not be fully abducted, otherwise the fascia in The medial border of the scapula is palpable inferior to the axilla will be tense and impede palpation of the humeral the root of the spine of the scapula as it crosses the 3rd–7th head. When the arm is moved and the scapula is fixed (held ribs. The lateral border of the scapula is not easily palpated in place), the head of the humerus can be palpated. because it is covered by the teres major and minor muscles. The greater tubercle of the humerus may be felt with the When the upper limb is abducted and the hand is placed on person’s arm by the side on deep palpation through the deltoid, Moore_Chap06.indd 681 12/10/2012 6:01:08 PM  682 Chapter 6 Upper Limb Clavipectoral (deltopectoral) triangle Coracoid process Deltoid Coracoid process Greater tubercle Lesser tubercle Pectoralis major Intertubercular sulcus (bicipital groove) Shaft of humerus Anterior view FIGURE 6.11. Palpation of coracoid process of scapula. inferior to the lateral border of the acromion. In this position, The posterior border of the ulna, palpable throughout the the greater tubercle is the most lateral bony point of the shoul- length of the forearm, demarcates the posteromedial bound- der and, along with the deltoid, gives the shoulder its rounded ary between the flexor–pronator and the extensor–supinator contour. When the arm is abducted, the greater tubercle is compartments of the forearm. The head of the ulna forms a pulled beneath the acromion and is no longer palpable. large, rounded subcutaneous prominence that can be easily The lesser tubercle of the humerus may be felt with dif- seen and palpated on the medial side of the dorsal aspect of ficulty by deep palpation through the deltoid on the anterior the wrist, especially when the hand is pronated. The pointed aspect of the arm, approximately 1 cm lateral and slightly subcutaneous ulnar styloid process may be felt slightly distal inferior to the tip of the coracoid process. Rotation of the to the rounded ulnar head when the hand is supinated. arm facilitates palpation of this tubercle. The location of The head of the radius can be palpated and felt to rotate in the intertubercular sulcus or bicipital groove, between the the depression on the posterolateral aspect of the extended greater and the lesser tubercles, is identifiable during flexion elbow joint, just distal to the lateral epicondyle of the and extension of the elbow joint by palpating in an upward humerus. The radial head can also be palpated as it rotates direction along the tendon of the long head of the biceps during pronation and supination of the forearm. The ulnar brachii as it moves through the intertubercular groove. nerve feels like a thick cord where it passes posterior to the The shaft of the humerus may be felt with varying dis- medial epicondyle of the humerus; pressing the nerve here tinctness through the muscles surrounding it. No part of the evokes an unpleasant “funny bone” sensation. proximal part of the humeral shaft is subcutaneous. The radial styloid process can be easily palpated in the The medial and lateral epicondyles of the humerus are anatomical snuff box on the lateral side of the wrist (see subcutaneous and easily palpated on the medial and lateral Fig. 6.65A); it is larger and approximately 1 cm more distal aspects of the elbow region. The knob-like medial epicon- than the ulnar styloid process. The radial styloid process is easi- dyle, projecting posteromedially, is more prominent than the est to palpate when the thumb is abducted. It is overlaid by the lateral epicondyle. tendons of the thumb muscles. Because the radial styloid pro- When the elbow joint is partially flexed, the lateral epi- cess extends more distally than the ulnar styloid process, more condyle is visible. When the elbow joint is fully extended, ulnar deviation than radial deviation of the wrist is possible. the lateral epicondyle can be palpated but not seen deep to a The relationship of the radial and ulnar styloid processes depression on the posterolateral aspect of the elbow. is important in the diagnosis of certain wrist injuries (e.g., The olecranon of the ulna can be easily palpated (Fig. 6.12). Colles fracture). Proximal to the radial styloid process, the When the elbow joint is extended, observe that the tip of anterior, lateral, and posterior surfaces of the radius are pal- the olecranon and the humeral epicondyles lie in a straight pable for several centimeters. The dorsal tubercle of radius is line (Fig. 6.12A & B). When the elbow is flexed, the olec- easily felt around the middle of the dorsal aspect of the distal ranon descends until its tip forms the apex of an approxi- end of the radius. The dorsal tubercle acts as a pulley for the mately equilateral triangle, of which the epicondyles form long extensor tendon of the thumb, which passes medial to it. the angles at its base (Fig. 6.12C). These normal relation- The pisiform can be felt on the anterior aspect of the ships are important in the diagnosis of certain elbow injuries medial border of the wrist and can be moved from side to (e.g., dislocation of the elbow joint). side when the hand is relaxed. The hook of the hamate can Moore_Chap06.indd 682 12/10/2012 6:01:12 PM  Chapter 6 Upper Limb 683 Medial epicondyle (site of ulnar nerve) Olecranon Lateral epicondyle Posterior view Head of radius (B) Extension: epicondyles and olecranon aligned Head of ulna during extension Ulnar styloid process Dorsal tubercle of radius Radial styloid process Scaphoid and trapezium Pisiform Hamate Styloid process of 3rd metacarpal Metacarpals Posterior view Lateral view (A) Posterior view (C) Flexion: epicondyles form triangle and align vertically with olecranon during flexion FIGURE 6.12. Surface anatomy of bones and bony formations of elbow region. be palpated on deep pressure over the medial side of the dorsal tubercle of radius. The dorsal aspects of the phalanges palm, approximately 2 cm distal and lateral to the pisiform. can also be easily palpated. The knuckles of the fingers are The tubercles of the scaphoid and trapezium can be palpated formed by the heads of the proximal and middle phalanges. at the base and medial aspect of the thenar eminence (ball of When measuring the upper limb, or segments of it, for thumb) when the hand is extended. comparison with the contralateral limb, or with standards for The metacarpals, although overlain by the long extensor ten- normal limb growth or size, the acromial angle (Fig. 6.10B), dons of the digits, can be palpated on the dorsum of the hand. lateral epicondyle of the humerus, styloid process of the The heads of these bones form the knuckles of the fist; the 3rd radius, and tip of the third digit are most commonly used as metacarpal head is most prominent. The styloid process of the measuring points, with the limb relaxed (dangling), but with 3rd metacarpal can be palpated approximately 3.5 cm from the palms directed anteriorly. BONES OF UPPER LIMB because the aim of treating an injured limb is to preserve or restore its functions. Upper Limb Injuries Because the disabling effects of an injury to an Variations of Clavicle upper limb, particularly the hand, are far out of pro- The clavicle varies more in shape than most other portion to the extent of the injury, a sound under- long bones. Occasionally, the clavicle is pierced by a standing of the structure and function of the upper limb is of branch of the supraclavicular nerve. The clavicle is the highest importance. Knowledge of its structure without thicker and more curved in manual workers, and the sites of an understanding of its functions is almost useless clinically muscular attachments are more marked. Moore_Chap06.indd 683 12/10/2012 6:01:12 PM  684 Chapter 6 Upper Limb Fracture of Clavicle not separate; the bone resembles a tree branch (greenstick) that has been sharply bent but not disconnected. The clavicle is one of the most frequently fractured bones. Clavicular fractures are especially common in Ossification of Clavicle children, and are often caused by an indirect force transmitted from an outstretched hand through the bones of The clavicle is the first long bone to ossify (via intra- the forearm and arm to the shoulder during a fall. A fracture membranous ossification), beginning during the 5th may also result from a fall directly on the shoulder. The weakest and 6th embryonic weeks from medial and lateral part of the clavicle is the junction of its middle and lateral thirds. primary ossification centers that are close together in the After fracture of the clavicle, the sternocleidomastoid shaft of the clavicle. The ends of the clavicle later pass through muscle elevates the medial fragment of bone (Fig. B6.1). a cartilaginous phase (endochondral ossification); the carti- Because of the subcutaneous position of the clavicle, the end lages form growth zones similar to those of other long bones. of the superiorly directed fragment is prominent—readily A secondary ossification center appears at the sternal end, palpable and/or apparent. The trapezius muscle is unable to and forms a scale-like epiphysis that begins to fuse with the hold the lateral fragment up owing to the weight of the upper shaft (diaphysis) between 18 and 25 years of age, and is com- limb; thus, the shoulder drops. The strong coracoclavicular pletely fused to it between 25 and 31 years of age. This is the ligament usually prevents dislocation of the acromioclavicular last of the epiphyses of long bones to fuse. An even smaller (AC) joint. People with fractured clavicles support the sag- scale-like epiphysis may be present at the acromial end of the ging limb with the other limb. In addition to being depressed, clavicle; it must not be mistaken for a fracture. the lateral fragment of the clavicle may be pulled medially by Sometimes fusion of the two ossification centers of the the adductor muscles of the arm, such as the pectoralis major. clavicle fails to occur; as a result, a bony defect forms between Overriding of the bone fragments shortens the clavicle. the lateral and medial thirds of the clavicle. Awareness of The slender clavicles of neonates may be fractured during this possible congenital defect should prevent diagnosis of a delivery if they have broad shoulders; however, the bones fracture in an otherwise normal clavicle. When doubt exists, usually heal quickly. A fracture of the clavicle is often incom- both clavicles are radiographed because this defect is usually plete in younger children—that is, it is a greenstick fracture, bilateral (Ger et al., 1996). in which one side of a bone is broken and the other is bent. This fracture was so named because the parts of the bone do Fracture of Scapula Fracture of the scapula is usually the result of severe trauma, as occurs in pedestrian–vehicle accidents. Sternocleidomastoid Usually there are also fractured ribs. Most fractures Trapezius require little treatment because the scapula is covered on both sides by muscles. Most fractures involve the protruding subcu- Trunks of brachial plexus taneous acromion. Fracture of clavicle Coracoclavicular ligament Fractures of Humerus Most injuries of the proximal end of the humerus are Coracoid process fractures of the surgical neck. These injuries are Brachial plexus especially common in elderly people with osteoporo- sis, whose demineralized bones are brittle. Humeral fractures Pectoralis major often result in one fragment being driven into the spongy bone of the other fragment (impacted fracture). The injuries usually result from a minor fall on the hand, with the force being trans- Humerus, scapula, and mitted up the forearm bones of the extended limb. Because of lateral fragment of clavicle shift down owing to gravity; impaction of the fragments, the fracture site is sometimes stable proximal humerus is pulled and the person is able to move the arm passively with little pain. medially by pectoralis major, An avulsion fracture of the greater tubercle of the humerus which may cause overriding of fractured ends of clavicle. is seen most commonly in middle-aged and elderly people