Osteology of the Upper Limb PDF

OSTEOLOGY OF THE UPPER LIMB BY DR. A.O. OJEWALE 1  Each upper limb INTRO’ contains 32 bones namely:  Bones of the pectoral girdle:  Scapula, the shoulder blade (1). Clavicle, the collar bone (1)...

OSTEOLOGY OF THE UPPER LIMB BY DR. A.O. OJEWALE 1  Each upper limb INTRO’ contains 32 bones namely:  Bones of the pectoral girdle:  Scapula, the shoulder blade (1). Clavicle, the collar bone (1). Humerus, the bone of arm (1). Radius and ulna, the bones of forearm (2). Carpal bones, the bones of wrist (8). Metacarpals, the bones of hand (5). Phalanges, the bones of digits (fingers) (14). Bones of the upper limb. 2  CLAVICLE The clavicle or collar bone is the long bone, with a slight S-shaped curve. It is located horizontally on the anterior aspect of the body at the junction of root of the neck and trunk. It articulates medially with the sternum and 1st rib cartilage and laterally with the acromion process of the scapula. It is subcutaneous and hence it can be palpated through its entire extent. It is the only bony attachment between the trunk and upper limb. 3  FUNCTIONS OF THE CLAVICLE It acts as a strut for holding the upper limb far from the trunk so that it can move freely. This allows free swing of the upper limb for various prehensile acts such as holding, catching, etc. It transmits forces from the upper limb to the axial skeleton (sternum). It provides an area for the attachment of muscles. 4  The features of the clavicle It is the only long bone which lies horizontally. It has no medullary cavity. It is subcutaneous throughout its extent. It is the first bone to start ossifying (between the fifth and sixth week of intrauterine life) and last bone to complete its ossification (at 25 years). It is the only long bone which ossifies by two primary centers. It is the only long bone which ossifies in membrane except for its medial end (long bones ossify in cartilage). It may be pierced through and through by cutaneous nerve (supraclavicular nerve). 5  PARTS:  The clavicle consists of three parts: two ends (medial and lateral) and a shaft. Ends  The lateral (acromial) end is flattened above downwards and articulates with medial margin of the acromion process.  The medial (sternal) end is enlarged and quadrilateral. It articulates with the clavicular notch of the manubrium sterni. Right clavicle: Upper one, superior aspect; Lower one, 6 inferior aspect. Parts of the clavicle (Cont’d)  Shaft The shaft is curved. Its medial two-third is round and convex forwards, and its lateral one-third is flattened and concave forwards. The inferior surface of the shaft possesses a small longitudinal groove in its middle third. 7  FEATURES AND ATTACHMENTS OF THE PARTS OF THE CLAVICLE Lateral End/Acromial End: It is flattened above downwards. An oval facet on this end articulates with the facet on the medial margin of the acromion to form acromioclavicular joint. The lateral end provides attachment to fibrous capsule of acromioclavicular joint. 8 Right clavicle showing attachments of the muscles and Medial End/Sternal End The enlarged medial end has a saddle- shaped articular surface, which articulates with the clavicular notch of manubrium sterni to form sternoclavicular joint. It provides attachment to (a) fibrous capsule (b) articular disc, and (c) interclavicular ligament. 9 Right clavicle showing attachments of the muscles and ligaments:  Shaft The shaft of the clavicle is divided into two parts: lateral one-third and medial two- third. The medial two-third of shaft is convex forward and lateral one-third is concave forward.  Lateral One-third It is flattened from above downwards. It has two surfaces, i.e., superior and inferior, and two borders, i.e., anterior and posterior. 10 Surfaces Superior surface: It is subcutaneous between the attachments of deltoid and trapezius. Inferior surface: It presents a conoid tubercle and trapezoid ridge, which provide attachments to conoid and trapezoid parts of coracoclavicular ligament, respectively. The conoid tubercle is located on the inferior surface near the posterior border at the junction of the lateral one-fourth and medial three-fourth of the clavicle. The trapezoid ridge extends forwards and laterally from conoid tubercle. 11 Borders Anterior border: It is concave forwards and gives origin to deltoid muscle. A small tubercle called deltoid tubercle may be present on this border. Posterior border: It is convex backwards and provides insertion to the trapezius muscle. 12 Medial Two-third of shaft of the clavicle It is cylindrical in shape and presents four surfaces: anterior, posterior, superior, and inferior. Anterior surface: It is convex forwards and gives origin to clavicular head of pectoralis major. Posterior surface: It is concave backwards and gives origin to sternohyoid muscle near its medial end. 13  Cont’d Superior surface: The clavicular head of sternocleidomastoid muscle originates from medial half of this surface. Inferior surface: It presents the following features: Costoclavicular ligament is attached to an oval impression at its medial end. Subclavius muscle is inserted into the subclavian groove on this surface. Clavipectoral fascia is attached to the margins of subclavian groove. Nutrient foramen of clavicle is located on the lateral end of the subclavian groove. 14 Muscles and ligaments attached to the clavicle Muscles ligaments Pectoralis major Coracoclavicular Sternocleidomastoid (clavicular Costoclavicular head) Deltoid Interclavicular Trapezius Subclavius 15  Ossification of the clavicle The ossification of clavicle is membranocartilaginous. It ossifies in the membrane except its medial end which ossifies in the cartilage. The clavicle begins to ossify before any other bone in the body. It ossifies by four ossification centres – two primary centres for shaft and two secondary centres, one for each end. 16  Ossification centers of the clavicle Site of appearance Time of appearance Time of fusion Two primary centres 5–6 weeks of 45th day of IUL (medial and lateral) intrauterine life (IUL) in the shaft Secondary centre at 19–20 years (2years 25th year sternal end earlier in female) Secondary centre at 20th year Fuses immediately the acromial end (occasional) 17  APPLIED ANATOMY Fracture of clavicle: The clavicle is the most commonly fractured bone in the body. It commonly fractures at the junction of its lateral one-third and medial two-third due to blows to the shoulder or indirect forces, usually as a result of strong impact on the hand or shoulder, when person falls on the outstretched hand or the shoulder. When fracture occurs, the lateral fragment is displaced downward by the weight of the upper limb because trapezius alone is unable to support the weight of the upper limb. 18  Cont’d  The fracture at the junction of lateral one-third and medial two-third occurs because: This is the weakest site. Two curvatures of clavicle meet at this site. The transmission of forces (due to impact) from the clavicle to scapula occur at this site through coracoclavicular ligament. Clavicle fracture: A, medial fragment; 19 Clavicular Congenital dysostosis: anomalies It is a clinical condition in which medial and lateral parts of clavicle remain separate due to non- union of two primary centers of ossification. Cleidocranial dysostosis: It is a clinical condition characterized by partial or complete absence of clavicle associated with defective ossification of the skull bones. 20  SCAPULA The scapula (shoulder blade) is a large, flattened, and triangular bone located on the upper part of the posterolateral aspect of the thorax, against 2nd to 7th ribs.  PARTS The scapula is highly mobile and consists of four parts: a body and three processes- spinous, acromion, and coracoid. Right scapula: A, anterior aspect 21  Body  The body is triangular, thin, and transparent. It presents the following features: Two surfaces: (a) costal and (b) dorsal. Three borders: (a) superior, (b) lateral, and (c) medial. Three angles: (a) inferior, (b) superior, and (c) lateral. The dorsal surface presents a shelf-like projection on its upper part called spinous process. The lateral angle is truncated to form an articular surface-the glenoid cavity. . 22 The lateral angle is thickened and called head of the scapula, which is connected to the plate-like body by an inconspicuous neck. Right scapula: anterior aspect; posterior aspect. 23 Processes  There are three processes. These are as follows: Spinous process. Acromion process. Coracoid process.  The spinous process is a shelf-like bony projection on the dorsal aspect of the body.  The acromion process projects forwards almost at right angle from the lateral end of the spine.  The coracoid process is like a bird’s beak. It arises from the upper border of the head and bends sharply to project superoanteriorly. 24  ATTACHMENTS  Surfaces Costal surface (subscapular fossa)  It is concave and directed medially and forwards.  It presents three longitudinal ridges, which provide attachment to the intramuscular tendons of subscapularis muscle.  The subscapularis muscle (a multipennate muscle) arises from the medial two-third of subscapular fossa/ costal surface except near the neck where a subscapular bursa intervenes between the neck and the subscapular tendon. 25  Cont’d The serratus anterior muscle is inserted on this surface along the medial border and inferior angle. Right scapula showing attachments of the muscles and 26 ligaments: Dorsal surface The dorsal surface is convex and presents a shelf-like projection called spinous process. The spinous process divides the dorsal surface into supraspinous and infraspinous fossae. The upper, supraspinous fossa is smaller (one-third) and lower, infraspinous fossa is larger (two-third). The spinoglenoid notch lies between lateral border of the spinous process and the dorsal surface of the neck of scapula. 27 Through the spinoglenoid notch supraspinous fossa communicates with the infraspinous fossa and suprascapular nerve and vessels pass from supraspinous fossa to the infraspinous fossa. The supraspinatus muscle arises from medial two-third of supraspinous fossa. The infraspinatus muscle arises from medial two-third infraspinous fossa. The teres minor muscle arises from the upper two-third of the dorsal surface of lateral border. This origin is interrupted by the circumflex scapular artery. 28 The teres major muscle arises from the lower one-third of the dorsal surface of lateral border and inferior angle of scapula. The latissimus dorsi muscle also arises from dorsal surface of the inferior angle by a small slip. Inferior angle Right scapula showing attachments of the m and ligaments: dorsal surface. 29 Borders  Superior border The superior border is the shortest border and extends between superior and lateral angles. The suprascapular notch is present on this border near the root of coracoid process. The suprascapular notch is converted into suprascapular foramen by superior transverse (suprascapular) ligament. 30  Cont’d The suprascapular artery passes above the ligament and suprascapular nerve passes below the ligament, through suprascapular foramen. The inferior belly of omohyoid arises from the superior border near the suprascapular notch. 31  Lateral border The lateral border is the thickest border, acts as fulcrum during rotation of the scapula and extends from inferior angle to the glenoid cavity. The infraglenoid tubercle is present at its upper end, just below the glenoid cavity. The long head of triceps muscle arises from the infraglenoid tubercle 32 Medial border (vertebral border) It extends from superior angle to the inferior angle. It is thin and angled at the root of spine of scapula. The serratus anterior muscle is inserted on the costal surface of the medial border and the inferior angle. The levator scapulae muscle is inserted on the dorsal aspect of the medial border from superior angle to the root of spine. 33  Cont’d The rhomboid minor muscle is inserted on the dorsal aspect of the medial border opposite the root of spine.  The rhomboid major muscle is inserted on the dorsal aspect of the medial border from the root of spine to the inferior angle. 34  Angles  Inferior angle: It lies over the 7th rib or the 7th intercostal space.  Superior angle: It is at the junction of superior and medial borders, and lies over the 2nd rib.  Lateral angle (head of scapula) It is truncated and bears a pear-shaped articular cavity called the glenoid cavity, which articulates with the head of humerus to form glenohumeral (shoulder) joint. A fibrocartilaginous rim, the glenoid labrum is attached to the margins of glenoid cavity to deepen its concavity. 35  Cont’d The capsule of shoulder joint is attached to the margins of glenoid cavity, proximal to the attachment of glenoid labrum. The long head of biceps brachii arises from supraglenoid tubercle. This origin is intracapsular. 36  Processes  Spinous process (spine of scapula) It is a triangular shelf-like bony projection, attached to the dorsal surface of scapula at the junction of its upper one-third and lower two-third. It divides the dorsal surface of scapula into two parts—upper supraspinous fossa and lower infraspinous fossa. The spine has two surfaces—(a) superior and (b) inferior, and three borders—(a) anterior, (b) posterior, and (c) lateral. 37  Surfaces The superior surface of spine forms the lower boundary of supraspinous fossa and gives origin to supraspinatus. The inferior surface of spine forms the upper limit of infraspinous fossa and gives origin to infraspinatus. 38  Borders The anterior border of spine is attached to the dorsal surface of scapula. The lateral border of spine bounds the spinoglenoid notch through which pass suprascapular nerve and vessels from supraspinous fossa to infraspinous fossa. The posterior border of spine is also called crest of spine. Trapezius is inserted to the upper lip of crest of spine, while posterior fibres of deltoid take origin from its lower lip. 39  Acromion process (acromion) It projects forwards almost at right angle from the lateral end of spine and overhangs the glenoid cavity. Its superior surface is subcutaneous. It has a tip, two borders (medial and lateral), and two surfaces (superior and inferior). The medial and lateral borders of acromion continue with the upper and lower lips of the crest of the spine of scapula, respectively. Its superior surface is rough and 40  Cont’d Its inferior surface is smooth and related to subacromial bursa. The medial border of acromion provides insertion to the trapezius muscle. Near the tip, medial border presents a circular facet, which articulates with the lateral end of clavicle to form the acromioclavicular joint. The lateral border of acromion gives origin to intermediate fibres of the deltoid muscle. The coracoacromial ligament is attached to the tip of acromion. 41  Cont’d The acromial angle is at the junction of lateral border of acromion and lateral border of the crest of the spine of scapula. 42 Coracoid process It arises from the upper part of the head of scapula and bent sharply so as to project forwards and slightly laterally. The coracoid process provides attachment to three muscles-short head of biceps brachii, coracobrachialis, and pectoralis minor, and three ligaments- coracoacromial, coracoclavicular, and coracohumeral. 43  Cont’d The short head of biceps brachii and coracobrachialis arise from its tip by a common tendon. The pectoralis minor muscle is inserted on the medial border of the upper surface. The coracoacromial ligament is attached to its lateral border. The conoid part of the coracoclavicular ligament (rhomboid ligament) is attached to its knuckle. 44  Cont’d The trapezoid part of the coracoclavicular ligament (rhomboid ligament) is attached to a ridge on its superior aspect between the pectoralis minor muscle and coracoacromial ligament. The coracohumeral ligament is attached to its root adjacent to the glenoid cavity. 45  OSSIFICATION The ossification of scapula is cartilaginous. The cartilaginous scapula is ossified by eight centres-one primary and seven secondary. The primary centre appears in the body. The secondary centres appear as follows: Two centres appear in the coracoid process. Two centres appear in the acromion process. One centre appears each in the (a) medial border, (b) inferior angle, and (c) in the lower part of the rim of glenoid cavity. 46  Cont’d The primary centre in the body and first secondary centre in the coracoid process appears in eighth week of intrauterine life (IUL) and first year of postnatal life, respectively and they fuse at the age of 15 years. All other secondary centres appear at about puberty and fuse by 20th year. 47  HUMERUS  The humerus is a long bone and consists of three parts: upper end, lower end, and shaft.  Upper End  The upper end presents the following five features: Head. Neck. Greater tubercle. Lesser tubercle. Intertubercular sulcus 48 Right humerus: anterior view; posterior 49  Cont’d The head is smooth and rounded, and forms less than half of a sphere. It is directed medially backwards and upwards. It articulates with the glenoid cavity of scapula to form the glenohumeral (shoulder) joint. 50  Lower End  The lower end presents the following features: Capitulum, a lateral rounded convex projection. Trochlea, a medial pulley-shaped structure. Radial fossa, a small fossa above the capitulum. Coronoid fossa, a small fossa above the trochlea. Medial epicondyle, a prominent projection on the medial side. Lateral epicondyle, a prominent projection on the lateral side but less than the medial 51  Cont’d Olecranon fossa, a large, deep hollow on the posterior aspect above the trochlea  Shaft The shaft is a long part of bone extending between its upper and lower ends. It is cylindrical in the upper half and flattened anteroposteriorly in the lower half. 52  FEATURES AND ATTACHMENTS Upper End Head It is smooth, rounded and forms one-third of a sphere. It is covered by an articular hyaline cartilage, which is thicker in the center and thinner at the periphery. 53 Right humerus showing attachments of the muscles and ligaments: A, anterior aspect; B, posterior aspect 54  Neck of the humerus  The humerus has three necks:  Anatomical neck  It is constriction at the margins of the rounded head.  It provides attachment to the capsular ligament of the shoulder joint, except- superiorly where the capsule is deficient, for the passage of tendon of long head of biceps brachii, medially the capsule extends down from the anatomical neck to the shaft for about 1–2 cm. 55 Surgical neck It is short constriction in the upper end of the shaft below the greater and lesser tubercles/below the epiphyseal line. It is related to axillary nerve and posterior and anterior circumflex humeral vessels. It is the most important feature of the proximal end of the humerus because it is weaker than the more proximal regions of the bone, hence it is one of sites where the humerus commonly fractures leading to damage of associated nerves and vessels. 56 Morphological neck It is the junction between diaphysis and epiphysis. It is represented by an epiphyseal line in the adult bone. It is a true junction of head with the shaft. 57  Greater tubercle It is the most lateral part of the proximal end of humerus. Its posterosuperior aspect bears three flattened facet-like impressions: upper, middle, and lower, which provide attachment to supraspinatus, infraspinatus, and teres minor muscles, respectively.  Lesser tubercle It is small elevation on the front of upper end of humerus, just above the surgical neck. It provides attachment to subscapularis muscle 58  Intertubercular Sulcus/Bicipital Groove It is a vertical groove between lesser and greater tubercles. It contains (a) long head of biceps, enclosed in the synovial sheath and (b) ascending branch of anterior circumflex humeral artery.  Three muscles are attached in the region of this groove: Pectoralis major on the lateral lip of the groove. Teres major on the medial lip of the groove. Latissimus dorsi in the floor of the groove 59  Shaft The upper part of the shaft is cylindrical and its lower part is triangular in cross section. It has three borders and three surfaces.  Borders Anterior border: It starts from the lateral lip of the intertubercular sulcus, and extends down to the anterior margin of the deltoid tuberosity and become smooth and rounded in the lower half, where it ends in the radial fossa. 60  Medial border It extends from the medial lip of the intertubercular sulcus down to the medial epicondyle. Its lower part is sharp and called medial supracondylar ridge. This ridge provides attachment to medial intermuscular septum. A rough strip on the middle of this border provides insertion to the coracobrachialis muscle. A narrow area above the medial epicondyle provides origin to the humeral head of the pronator teres. 61 Lateral border Its upper part is indistinct while its lower part is prominent where it forms the lateral supracondylar ridge. Above the lateral supracondylar ridge, it is ill-defined but traceable to the posterior part of the greater tubercle. About its middle, this border is crossed by the radial groove from behind. The lower part of this border, lateral supracondylar ridge, provides attachment to the lateral intermuscular septum. 62  Surfaces Anterolateral surface It lies between the anterior and lateral borders. A little above the middle, this surface presents a characteristic V-shaped tuberosity–the deltoid tuberosity which provides insertion to the deltoid muscle. 63  Anteromedial surface It lies between the anterior and medial borders. The upper part of this surface forms the floor of the intertubercular sulcus. About its middle and close to the medial border it presents a nutrient foramen directed downwards. 64 Posterior surface It lies between the medial and lateral borders. In the upper one-third of this surface, there is an oblique ridge directed downwards and laterally. This ridge provides origin to the lateral head of the triceps brachii. Below and medial to the ridge, is the radial/spiral groove, which lodges radial nerve and profunda brachii vessels. The entire posterior surface below the spiral groove provides origin to the medial head of the triceps brachii. 65 Lower End of the humerus It is flattened from before backwards and expanded from side to side. The capitulum (rounded convex projection laterally) articulates with the head of radius. The trochlea (pulley-shaped projection medially) articulates with the trochlear notch of ulna. The ulnar nerve is related to the posterior surface of the medial epicondyle. The anterior surface of the medial epicondyle provides an area for common flexor origin of the superficial flexors of the forearm. 66 The anterolateral part of lateral epicondyle provides an area for common extensor origin. The posterior surface of lateral epicondyle gives origin to anconeus muscle. The coronoid process of ulna fits into coronoid fossa (above the trochlea) during full flexion of elbow. The head of radius fits into radial fossa (above capitulum) during full flexion of elbow. The olecranon process of ulna fits olecranon fossa (on posterior aspect above the trochlea) into during full extension of elbow. The capsule of elbow joint is attached above the coronoid and radial fossae anteriorly and above the olecranon fossa posteriorly. 67  OSSIFICATION The humerus is ossified by the following ossification centres: One primary centre for shaft. Three secondary centres for upper end. Four secondary centres for lower end. 68  APPLIED ANATOMY The three nerve (axillary, radial, and ulnar) are closely related to the back of humerus as follows:  Axillary nerve around the surgical neck.  Radial nerve in the radial/spiral groove  Ulnar nerve behind the medial epicondyle. These nerves are often involved in the fracture of humerus at the above sites: Common sites of fracture of the Three nerves closely humerus: These are (a) surgical neck related to the back of the 69 humerus Supracondylar fracture of the humerus: It is caused by a fall on the outstretched hand and commonly occurs in young age. Anatomically, it presents as backwards displacement of the lower fragment with unduly prominent elbow, however the three bony points of elbow (medial epicondyle, lateral epicondyle, and olecranon process) form the usual equilateral triangle because the olecranon process always moves Supracondylar fracture of with the lower fragment. the humerus 70  Cont’d This fracture may cause injury to median nerve and brachial artery. The injury to the brachial artery may cause Volkmann’s ischemic contracture. Median nerve is most commonly involved in the Supracondylar fracture of the humerus The separate centre for medial epicondyle and its late union with the shaft may be mistaken for the fracture of medial epicondyle of humerus. 71  RADIUS The radius is the lateral bone of the forearm and is homologous to the medial bone of the leg, the tibia.  PARTS The radius is a long bone and consists of three parts: upper end, shaft, and lower end. 72 Upper End The upper end presents head, neck, and radial tuberosity. The head is disc shaped and articulates above with the capitulum of humerus. The neck is constricted part below the head. The radial tuberosity is just below the medial part of the neck.  Shaft The long shaft extends between the upper and lower ends and presents a lateral convexity. It widens rapidly towards the distal end and is concave anteriorly in its distal part. Its sharpest interosseous border is located on the medial side. 73  Lower End The lower end is the widest part and presents five surfaces. The lateral surface projects distally as the styloid process. The dorsal surface presents a palpable dorsal tubercle (Lister’s tubercle), which is limited medially by an oblique groove. 74 Right radius and ulna: Anterior view 75  ANATOMICAL POSITION  The side of radius can be determined by keeping the bone vertically in such a way that:  The narrow disc-shaped end(head) is directed upwards.  The sharpest border (interosseous border) of the shaft is kept medially.  The styloid process at the lower end is directed laterally and prominent tubercle (Lister’s tubercle) at lower end faces dorsally.  The convexity of shaft faces laterally, and concave anterior surface of shaft faces anteriorly. 76  FEATURES AND ATTACHMENTS  Upper End  Head It is shaped like a disc and in living it is covered with an articular hyaline cartilage. It articulates superiorly with capitulum to form humero-radial articulation. The circumference of head is smooth and articulates medially with the radial notch of ulna, rest of it is encircled by the annular ligament. 77  Neck It is the constricted part just below the head and is embraced by the lower part of annular ligament. The quadrate ligament is attached to the medial side of the neck.  Radial tuberosity Biceps tendon is inserted to its rough, posterior part. A small synovial bursa covers its smooth anterior part and separates it from the biceps tendon. 78  Shaft The shaft has three borders and three surfaces. Borders Anterior border It starts below the anterolateral part of radial tuberosity and runs downwards and laterally to the styloid process. The upper part of this border is called anterior oblique line and lower part forms the sharp lateral border of the anterior surface. Its anterior oblique line gives origin to radial head of flexor digitorum superficialis (FDS).79 Radius and ulna of right side showing attachments of the muscles and ligaments: A, anterior aspect; B, posterior aspect (FCU = flexor carpi ulnaris, ECU = extensor carpi 80 ulnaris, FDP = flexor digitorum profundus).  Posterior border It is well-defined only in its middle third of the shaft. Above it runs upwards and medially to the radial tuberosity and form the posterior oblique line.  Medial (interosseous) border It is the sharpest border. It extends above up to radial tuberosity and below its lower part forms the posterior margin of the small triangular area on the medial side of the lower end of the bone. Interosseous membrane is attached to its lower three-fourth 81  Surfaces Anterior surface It is concave and lies between anterior and interosseous borders. Flexor pollicis longus originates from its upper two-fourth. Pronator quadratus is inserted on its lower one-fourth. Nutrient foramen is present a little above the middle of this surface in its upper part. The nutrient canal is directed upwards. Nutrient artery for radius is a branch from anterior interosseous artery. 82  Posterior surface It lies between the interosseous and posterior borders. Abductor pollicis longus (APL) arises from the middle one-third of this surface. Extensor pollicis brevis (EPB) arises from lower part of this surface. Lateral surface It lies between anterior and posterior borders. Supinator is inserted on the widened upper one-third of this surface. Pronator teres is inserted on the rough area in the most convex middle part of this surface. 83  Lower End The lower end is the widest part of the bone and has five surfaces. Anterior surface: The anterior surface presents a thick ridge, which provides attachment to palmar radio-carpal ligament of wrist joint. Posterior surface: The posterior surface presents the dorsal tubercle of Lister lateral to the groove for the tendon of extensor pollicis longus. It also presents grooves for other extensor tendons. 84 The groove lateral to the Lister’s tubercle is traversed by tendons of extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB). Through the groove medial to groove for extensor pollicis longus passes tendons of extensor digitorum and extensor indicis. Medial surface: The medial surface presents the ulnar notch for articulation with the head of ulna. Articular disc of inferior radio-ulnar joint is attached to the lower margin of ulnar notch. 85 Lateral surface: The lateral surface projects downward as the styloid process and is related to tendons of adductor pollicis longus and extensor pollicis brevis. The brachioradialis is inserted to the base of styloid process and radial collateral ligament of wrist joint is attached to the tip of styloid process. Inferior surface: The inferior (distal) surface presents a lateral triangular area for articulation with the scaphoid and a medial quadrangular area for articulation with the lateral part of the lunate. 86  OSSIFICATION  The radius ossifies from the following three centres:  One primary centre appears in the mid-shaft during 8th week of IUL.  Two secondary centres, one for each end: Centre for lower end appears at the age of first year. Centre for upper end appears during fifth year. The upper epiphysis fuses at the age of 12 years. The lower epiphysis fuses at the age of 20th year. 87  Madelung deformity: It is a congenital anomaly of radius which presents the following clinical features. The anterior bowing of distal end of radius, due to an abnormal growth of distal epiphysis. It occurs between 10 and 14 years of age. There is premature disappearance of distal epiphyseal line. There may be subluxation or dislocation of distal end of ulna, due to defective development of distal radial epiphysis. 88  APPLIED ANATOMY The radius is a weight-bearing bone of the forearm; hence fractures of radius are more common than ulna. In fracture shaft of radius, with fracture line below the insertion of biceps and above the insertion of pronator teres the upper fragment is supinated by supinator and lower fragment is pronated by the pronator teres. In fracture at the distal end of radius (Colles’ fracture) the distal fragment is displaced backwards and upwards. The reverse of Colles’ fracture is called Smith’s fracture. 89 Fracture of styloid process of radius is termed ‘Chauffeur’s fracture’ The radius is most commonly fractured bone in people over 50 years of age. It is often fractured as a result of a fall on outstretched hand. Fracture at distal end of the radius: 90 A,Colles’ fracture; B, Smith’s fracture  ULNA The ulna is the medial bone of forearm and is homologous to the lateral bone of leg-the fibula.  PARTS The ulna is a long bone and consists of three parts: upper end, lower end, and shaft. Upper End The upper end is expanded and hook-like with concavity of hook facing forwards. The concavity of upper end (trochlear notch) lies between large olecranon process above and the small coronoid process below. 91  Shaft The long shaft extends between the upper and lower ends. Its thickness diminishes progressively from above downwards throughout its length. The lateral border (interosseous border) is sharp crest-like.  Lower End The lower end is slightly expanded and has a head and styloid process. The styloid process is posteromedial to the head. 92  ANATOMICAL POSITION  It can be determined by keeping the side of ulna bone vertically in such a way that: The broad hook-like end is directed upwards. The sharp crest-like interosseous border of shaft is directed laterally. The concavity of the hook-like upper end and the coronoid process are facing forwards 93  FEATURES AND ATTACHMENTS Upper End The upper end has two processes: coronoid and olecranon, and two notches: trochlear and radial. Processes Olecranon process: It projects upwards from the upper end and bends forward at its summit like a beak. It has the following five surfaces: 94  Upper surface Its rough posterior two-third provides insertion to the triceps brachii. Capsular ligament of elbow joint is attached anteriorly near its margins. A synovial bursa lies between the tendon of triceps and capsular ligament. Anterior surface: It is smooth and forms upper part of the trochlear notch. Posterior surface It forms a subcutaneous triangular area. A synovial bursa (subcutaneous olecranon bursa) lies between posterior surface and skin. 95  Cont’d Medial surface: Its upper part provides attachments to three structures: (a) ulnar head of flexor carpi ulnaris (origin), (b) posterior, and (c) oblique bands of ulnar collateral ligament.  Coronoid process: It is bracket-like projection from the front of the upper end of the ulna below the olecranon process. It has four surfaces: superior, anterior, medial, and lateral. 96 Superior surface: It is smooth and forms the lower part of trochlear notch Anterior surface: It is triangular in shape. Its lower corner presents an ulnar tuberosity. Brachialis muscle is inserted to the whole of the anterior surface including ulnar tuberosity.  The medial margin of the anterior surface is sharp and has a tubercle at its upper end called sublime tubercle. 97  Cont’d The medial margin provides attachment to the following structures from proximal to distal: (i) Anterior band of ulnar collateral ligament. (ii) Oblique band of ulnar collateral ligament. (iii) Humero-ulnar head of flexor digitorum superficialis (iv) Ulnar head of pronator teres. (v) Ulnar head of flexor pollicis longus. Medial surface: It gives origin to flexor digitorum profundus. 98  Cont’d  Lateral surface: The upper part of this surface possesses a radial notch for articulation with the head of the radius. The annular ligament is attached to the anterior and posterior margins of the radial notch.  The lower part of the lateral surface below radial notch has a depressed area called supinator fossa, which accommodates radial tuberosity during supination and pronation. Supinator fossa is bounded behind by supinator crest. Supinator crest and adjoining part of supinator fossa gives origin to the supinator muscle. 99 Notches (articular surfaces) Trochlear notch It is C-shaped (semilunar) and articulates with the trochlea of humerus. It has a non-articular strip at the junction of its olecranon and coronoid parts. Its superior, medial, and anterior margins provide attachment to capsule of the elbow joint. Radial notch It articulates with the head of radius to form the superior radio-ulnar joint. 100 Shaft It has three borders-lateral, anterior, and posterior; and three surfaces-anterior, medial, and posterior. Borders  Lateral (interosseous) border It is sharpest and is continuous above with the supinator crest. It is ill-defined below. Interosseous membrane is attached to this border except for its upper part. 101  Anterior border It extends from the medial side of the ulnar tuberosity to the base of styloid process. It is thick and round. It upper three-fourth gives origin to flexor digitorum profundus.  Posterior border It starts from the apex of triangular subcutaneous area on the back of olecranon process and descends to the styloid process. It is subcutaneous throughout, hence can be palpated along its entire length. It provides attachment to three muscles by a common aponeurosis. The muscles are: (a) Flexor digitorum profundus, (b) Flexor carpi ulnaris.(c) Extensor carpi ulnaris. 102  Surfaces  Anterior surface It lies between anterior and interosseous borders. The flexor digitorum profundus arises from its upper three-fourth. The pronator quadratus arises from an oblique ridge on the lower one-fourth of this surface. The nutrient foramen is located a little above the middle of this surface and is directed upwards. 103  Medial surface It lies between the anterior and posterior borders. The flexor digitorum profundus arises from the upper two-third of this surface Posterior surface It lies between posterior and interosseous borders. It is divided into smaller upper part and large lower part by an oblique line, which starts at the junction of upper and middle third of posterior border and runs towards the posterior edge of radial notch. 104 Area above the oblique line receives insertion of anconeus muscle. Area below the oblique line is divided into larger medial and smaller lateral parts by a faint vertical line. The lateral part provides attachment to three muscles form proximal to distal as follows: Abductor pollicis longus in the upper one- fourth. Extensor pollicis longus in the middle one- fourth. Extensor indicis in the next one-fourth. The distal one-fourth is devoid of any attachments. 105 Lower End The lower end consists of head and styloid process. Head It presents a convex articular surface on its lateral side for articulation with the ulnar notch of radius to form the inferior radio-ulnar joint. Its inferior surface is smooth and separated from wrist joint by an articular disc of inferior radio-ulnar joint. 106 Styloid process It projects downwards from the posteromedial aspect of the head of ulna Its tip provides attachment to medial collateral ligament of wrist joint. The apex of triangular articular disc is attached to the depression between head and base of styloid process. Tendon of extensor carpi ulnaris lies in the groove between the back of the head of ulna and styloid process. 107 OSSIFICATION The ulna ossifies from the three main centres: one primary centre for the shaft and two secondary centres, one each for the lower end and the upper end. 108  APPLIED ANATOMY A fracture of the shaft of ulna due to direct injury when a night watchman reflexly raises his forearm to ward off the blow of the stick is termed night-stick fracture. When the elbow is fully extended, the tip of olecranon process and medial and lateral epicondyles of the humerus lie in a same horizontal line. When the elbow is fully flexed the three bony points form an equilateral triangle. In dislocation of elbow this relationship is disturbed. 109 Ulna stabilizes the forearm by gripping the lower end of humerus by its trochlear notch and provides foundation for radius to produce supination and pronation at superior and inferior radio-ulnar joints. The fracture of upper third of shaft of ulna with dislocation of radial head at superior radio-ulnar joint is called Monteggia fracture dislocations.  The fracture of lower third of the shaft of radius associated with dislocation of inferior radio-ulnar joint is called Galeazzi fracture dislocation. 110 THANK YOU 111