Osteology of the Upper Limb PDF

Osteology of the Upper Limb By Dr. Felix Ovie Ogbo  Introduction to Osteology of the Upper Limb Osteology is the study of the structures of bones or skeletal system. With Concern; human bones and the analysis of their shape, structure, and composition. It is ap...

Osteology of the Upper Limb By Dr. Felix Ovie Ogbo  Introduction to Osteology of the Upper Limb Osteology is the study of the structures of bones or skeletal system. With Concern; human bones and the analysis of their shape, structure, and composition. It is applied in various fields such as forensic anthropology, Paleontology, and archeology to identify individuals. Terminology in Osteology: a long bone shaft is the Diaphysis, the ends of the bone are the Epiphysis. And the region where the diaphysis runs into the epiphysis is known as Metaphysis. Bones found in the upper limb include: General view of the bones of the upper 1. Clavicle at the shoulder limb 2. Scapula at the shoulder involved in the pectoral girdle 3. Humerus in the arm 4. Ulna on the medial side of forearm 5. Radius on the lateral side of forearm 6. Carpals at the wrist 7. Metacarpals in the hand 8. Phalanges in the hand  Pectoral Girdle Two scapulae and two clavicles make up the pectoral (shoulder) girdle. It is not a complete girdle, having only an anterior attachment to the axial skeleton, via the sterno clavicular joint at the sternum. Lacking a posterior attachment to the axial skeleton, the pectoral girdle has a wide range of movement. Because it is not weight-bearing, it is structurally more delicate than the pelvic girdle. The primary function of the pectoral girdle is to provide attachment areas for the numerous muscles that move the shoulder and elbow joints.  Clavicle The clavicle connects the upper limbs to the trunk. It is placed nearly horizontally at the anterior aspect of the thorax immediately above the first rib. It articulates medially (the sternal end) with the manubrium of sternum at the sternoclavicular joint and laterally (acromial end) with the acromion of the scapula at the acromioclavicular joint.  Functions of the clavicle 1. It acts as a fulcrum for muscles that enable lateral movement of the arm 2. It forms one of the bony boundaries of the cervico axillary canal and thus protects the neurovascular bundle passing through that canal to supply the upper limbs. 3. Transmits shock from the upper limb to the axial skeleton. The clavicle presents a double curvature; a convex curvature directed anteriorly towards the sternal end, and a concave curvature directed posteriorly towards the acromial end. The two curvatures divide the clavicle into a medial 2/3 and a lateral 1/3.  Lateral 1/3 of Clavicle The lateral 1/3 has – 2 borders – anterior and posterior borders and 2 flat surfaces- a superior surface and an inferior surface. The superior surface is flat and has an impression for attachment of muscles. Deltoid muscle is attached in front while trapezius muscle is attached behind this impression. The inferior surface is also flat and rougher than the superior surface owing to strong ligament attachments to it. Towards the acromial end, the clavicle presents a rounded elevation called the conoid tubercle which gives attachment to the conoid ligament.  The lateral 1/3 terminates at the acromial end of the clavicle. The acromial end of the clavicle is flattened and directed a bit downwards for articulation with the acromial process of scapula. At the circumference of the articular facet is attached the acromio clavicular ligament. Medial 2/3 The medial 2/3 of the clavicle is convex anteriorly and concave posteriorly. It has – 3 borders – anterior, superior and posterior 3 surfaces – anterior, posterior and inferior  Borders The lateral part of the anterior border is smooth and marks the interval between the attachments of pectoralis major and deltoid muscles. At the medial part is attached the clavicular head of pectoralis major muscle. The superior border is smooth laterally but rough medially. The rough medial part gives attachment to the sternocleidomastoid muscle. The posterior border is also called the subclavian border. It separates the posterior and inferior surfaces and forms the posterior boundary of the groove for subclavius. This groove gives attachment to a layer of the cervical fascia which envelops the omohyoid muscle.  Variations of the Clavicle The clavicle varies in shape in the population. It is one of the most variable long bones. Generally, the female clavicle is thinner, less curved and smoother than those of the male. In individuals who often engage in manual labour, the clavicle is much more thicker and more curved with more prominent markings and ridges for muscle attachment.  Ossification of the Clavicle 1. The clavicle is the first bone to begin ossification and one of the last to finish, beginning at about 5th to 6th weeks intrauterine and ends at about age 25. 2. Two primary centers appear in the shaft during the 6th week of fetal life and soon fuse with each other. 3. The sternal end ossifies from a secondary center that appears between 15 and 20 years of age, and fuses with the shaft by the age of 25 years. 4. An additional center may appear in the acromion.  Applied Anatomy 1. Fractures of the Clavicle Fractures: the clavicle is one of Most fractures of the clavicle are the most fractured bones in caused by indirect violence. The the body due to its position. bone is most commonly fractured at the junction of its medial 2/3 and lateral 1/3. Children are at higher risk of this fracture which may result from indirect force transmitted 2. Green stick fractures from an out stretched hand This occurs during child delivery. In through the forearm bones to this case, one of the clavicles is the shoulder during a fall. fractured and the other one is bent, giving the resemblance of a tree branch that has been bent sharply The clavicle is weakest at but not disconnected, hence the junction between the medial name green stick fracture.  Scapula The scapula, otherwise called the The scapular has; shoulder blade is a triangular flat 2 surfaces – Anterior and bone that lies on the posterolateral posterior. aspect of the thorax. 3 angles – Superior, lateral and inferior. It overlies the 2nd to 7th ribs. 3 borders – Medial, lateral and superior. The greater part of the scapula 3 Processes – Spine, acromion and consists of a flat triangular plate of coracoid. bone called the body. The upper part of the body is broad, representing the base of the triangle. The inferior end is pointed and represents the apex.  Surfaces The body has 2 surfaces - The part above the spine forms anterior (or costal) and the supraspinous fossa, posterior (or dorsal) along with the upper surface of the spine. surfaces. The area below the spine The anterior surface is forms the infraspinous smooth and lies against fossa, along with the lower the posterolateral part of surface of the spine. the chest wall. It is somewhat concave from The supraspinous and above downwards. infraspinous fossae communicate with each other through the spinoglenoid  The acromion is continuous The medial border of the with the lateral end of the acromion shows the presence spine. It forms a projection that of a small oval facet for is directed forwards and partly articulation with the lateral overhangs the glenoid cavity. end of the clavicle. It has 2 borders lateral and The acromion also has upper medial that meet anteriorly at and lower surfaces. the tip of the acromion. The lateral border meets the crest of the spine at a sharp angle termed the acromial angle.  Borders The lateral border runs from the glenoid cavity to the inferior angle. The medial border extends from the superior angle to the inferior angle. The superior border passes laterally from the superior angle, but is separated from the glenoid cavity (at lateral angle) by the root of the coracoid process. A deep suprascapular notch is seen at the lateral end of the superior border. The region of the glenoid cavity is often regarded as the head of the scapula. Immediately medial to it there is a constriction which constitutes the neck.  Clinical Correlation 1. Fractures of the scapula are uncommon. 2. Sprengles shoulder is a They can occur in automobile condition in which the scapula accidents. Usual sites of fracture is placed higher than normal. are: 3. Winging of the scapula is a a. Body of the scapula. condition in which the medial border of the scapula is lifted b. Fracture through the neck. off the chest wall. c. Fracture of the acromion process. It is caused by paralysis of the serratus anterior. d. Fracture of the coracoid process  Humerus The humerus is a long bone. A long bone is usually made up of 3 parts – a. an upper end b. a shaft c. a lower end. The humerus is a typical example of a long bone.  Upper end of Humerus This is to differentiate it from a relatively The upper end of the humerus bears: lower area slightly below the tubercles called the surgical neck. The head of humerus which is hemispherical in shape and articulates with the glenoid The head of humerus is directed upwards cavity of the scapula to form the and medially. glenohumeral (shoulder) joint. It is larger than the glenoid cavity with which it articulates at the shoulder joint. Two tubercles – greater tubercle and lesser tubercle, separated by an intertubercular The greater tubercle bears 3 flat sulcus. impressions in a highest, middle and lowest order. A depressed area connects the head with the tubercles of the humerus. These impressions give attachment to the insertions of the supraspinatus, This depressed area is called the anatomical infraspinatus and teres minor respectively. neck.  The lesser tubercle on the other hand is pronounced, although smaller than the greater, and bears an impression which gives attachment to the subscapularis muscle. These 4 muscles together constitute the rotator cuff (SITS) muscles which confer some degree of stability to the upper part of the shoulder joint. The intertubercular sulcus, also called the bicipital groove lodges the tendon of the long head of biceps brachi muscle and also transmits a branch of the anterior circumflex humeral artery en route to the shoulder joint. The surgical neck is below the tubercles and is the commonest site of fracture of the humerus.  Shaft of Humerus The shaft is otherwise called the body and by description is triangular in shape. As such, it has – Three borders: anterior, lateral and medial, and Three surfaces: anterolateral, anteromedial and posterior.  Lower End Of Humerus The lower end of humerus is It is therefore referred to as the triangular in shape. It ends below common flexor tendon. It is larger on each side in a broad articular than the lateral epicondyle and gives surface descending from the attachment to the ulna collateral supracondylar ridges into a prominent ridge called the ligament of the elbow joint. epicondyle. The ulna nerve runs in a groove on So, on the medial side we have the the back of the medial epicondyle medial epicondyle and on the and can be demonstrated at this lateral side we have the lateral site. epicondyle. The medial epicondyle represents Correspondingly on the lateral site a common site of origin for muscles is the lateral epicondyle which that flex the elbow joint and represents a common site of forearm and the pronator teres attachment for extensors of the muscle. elbow joint and forearm and the supinator muscle.  The lateral epicondyle is smaller than the medial epicondyle and also gives attachment to the radial collateral ligament of the elbow joint. As a result of the fact that the medial epicondyle is larger than the lateral epicondyle, the forearm at the elbow joint usually tilts away from the body (as in a woman carrying a bad), thereby creating an angle between the tilted forearm and the body. The angle is called carrying angle. Extending beyond the epicondyles are two prominent projections joined together at the middle. The lateral ends of these projections are more prominent than the medial ends. The surfaces of these prominences are smooth because they are lined by hyaline cartilage (typical for articular surfaces of synovial joints). The lateral prominence is called the capitulum while the  The capitulum articulated with the head of the radius at the humero radial articulation (a part of the elbow joint) while the trochlear process fits into the trochlear notch of ulna at the humero ulna articulation (also a part of the wrist joint). Above the front of the capitulum is a prominent depression called the radial fossa which receives the anterior border of the head of radius when the forearm is flexed. Above the front part of the trochlear process is a relatively smaller depression called the coronoid fossa which receives the coronoid process of the ulna when the forearm is flexed. At the back of the lower end of the humerus is another prominent fossa called the olecranon fossa which receives the summit of the olecranon process of the ulna when the forearm is flexed.  Ossification of the Humerus 3. Secondary centers at the lower end are as 1. A primary center appears in the shaft follows: during the 8th fetal week. The greater part of the bone is formed from this center. In the capitulum during the first year. 2. Secondary centers at the upper end In the medial part of the trochlea in the ninth or appear as follows: tenth year. For the head appears early in the first year. In the lateral epicondyle around the twelfth year. For the greater tubercle in the second year. These fuse to form a single epiphysis which For the lesser tubercle in the fifth year. fuses with the shaft around 15 years of age. These three parts fuse with each other in A separate center appears in the medial the sixth year to form a single epiphysis for epicondyle around the fifth year; and fuses with the upper end that fuses with the shaft the shaft about the twentieth year. around 18 to 20 years of age.  Applied Anatomy 1. Most fractures of the humerus occur at the surgical neck. This is most common in the elderly due to osteoporosis.  BONES OF THE FOREARM Radius The radius is the shorter and lateral of the two forearm bones. It has a proximal end and a distal end connected by a shaft. Proximal End The proximal end includes a head which is short, a neck and a tuberosity which is directed medially. Proximally, the superior aspect of the head of radius is concave for articulation with the capitulum of humerus during flexion and extension of the elbow joint. The head also articulates peripherally with the radial notch of ulna. Thus, the head is covered with articular cartilage. The neck of radius is the constriction distal to the head. The radial tuberosity is oval and is located distal to the medial part of the neck and demarcates the proximal end from the shaft.  The lateral and medial sides of the bone can be distinguished by examining the shaft which is convex laterally and has a sharp medial (or interosseous) border. The head is disc shaped and its upper surface is slightly concave and articulates with the capitulum of the humerus. Medially, the head of radius articulates with a depression at the upper end of the ulna called the radial notch of ulna. This union marks the formation of the superior radioulnar joint. The region just below the head is constricted to form the neck. Just below the medial part of the neck there is an elevation called the radial tuberosity.  Shaft The shaft of the radius in contrast to that The anterior border begins at of the ulna gradually enlarges as it the radial tuberosity and runs passes distally. downwards and laterally across the anterior aspect of the shaft. The shaft of the radius has three borders This part of the anterior border is (anterior, posterior, and interosseous) called the anterior oblique and three surfaces (anterior, posterior, line. lateral). The medial border, also called interosseous border is easily identified The anterior surface lies as it forms a sharp ridge which extends between the interosseous and from just below the tuberosity to the anterior borders, the posterior lower end of the shaft. surface between the interosseous and posterior Near the lower end this border forms the borders while the lateral posterior margin of a small triangular surface is between the anterior area. and posterior borders.  Distal End The distal end of the radius is essentially 4 sided in a transverse section. It has anterior, lateral and posterior surfaces (as in the shaft), and additional medial and inferior surfaces. The lateral surface prolong downwards as a projection called the styloid process. The medial aspect of the lower end has an articular area called the ulnar notch of radius. It articulates with the lower end of the ulna to form the inferior radioulnar joint. The inferior surface of the lower end is articular. It takes part in forming the wrist joint. It is subdivided into a medial quadrangular area that articulates with the lunate bone, and a lateral triangular area that articulates with the scaphoid bone.  Ossification of the Radius 1. A primary centre appears in the shaft during the 8th week of fetal life. 2. A secondary centre appears in the lower end in the first year and joins the shaft around 18 years of age. 3. A secondary centre appears in the head of the bone during the 4th or 5th year and fuses with the shaft around the 16th year. Occasionally, the radial tuberosity may ossify from a separate centre.  Clinical Correlation Fractures of the Radius 1. The radius may be fractured through the middle of its shaft (either alone or along with the shaft of the ulna). It may also be fractured either through the upper end (or head) or through the lower end. 2. Fracture of the lower end of the radius is called Colles’s fracture. This fracture is very common in older persons, especially women. Complications of this fracture include injury to or compression of the median nerve, rupture of the tendon of the extensor pollicis longus and subluxation of the inferior radioulnar joint. 3. Occasionally, fracture of the lower end of the radius is associated with forward displacement (as against backward displacement in Colles’s fracture). This is called Smith’s fracture or Barton’s fracture.  Ulna The ulna, being a long bone has a shaft, an upper end and a lower end. Upper End 1. The upper end is irregular and larger compared to the lower end is small. 2. The upper end has a large trochlear notch on its anterior aspect. 3. The upper end of the ulna consists of two prominent projections - the olecranon process and the coronoid process. 4. When seen from behind the olecranon process appears to be a direct upward continuation of the shaft and forms the uppermost part of the ulna. 5. The coronoid process projects forwards from the anterior aspect of the ulna just below the olecranon.  6. The trochlear notch covers the anterior aspect of the olecranon process and the superior aspect of the coronoid process. It takes part in forming the elbow joint and articulates with the trochlea of the humerus. 7. The trochlear notch is also divisible into medial and lateral areas corresponding to the medial and lateral flanges of the trochlea. 8. In addition to its anterior surface which forms the upper part of the trochlear notch, the olecranon process has superior, posterior, medial and lateral surfaces. 9. The anterior surface is triangular. Its lower part shows a rough projection called the tuberosity of the ulna. 10. The upper part of the lateral surface of the coronoid process shows a concave articular facet called the radial notch. The radial notch articulates with the head of the radius forming the superior radio-ulnar joint.  The Shaft 1. The shaft of the ulna 3 borders; a sharp lateral/ interosseous border, and less prominent anterior and posterior borders. 2. It also has 3 surfaces; anterior, posterior and medial. 3. The anterior border begins at the tuberosity of the ulna and runs downwards until it terminates as the styloid process. 3. The posterior border begins at the apex of the triangular area on the posterior aspect of the olecranon process and ends at the styloid process. 4. The anterior surface of the ulna lies between the interosseous and anterior borders, the medial surface lies between the anterior and posterior borders and the posterior surface is bounded by the interosseous and posterior borders.  The Lower End 1. The lower end of the ulna consists of a disc-like head and a styloid process. 2. The head has a circular inferior surface which is separated from the cavity of the wrist joint by an articular disc. It also has another convex articular surface on its lateral side which articulates with the ulnar notch of radius to form the inferior radioulnar joint. 3. The styloid process is a small downward projection that lies on the posteromedial aspect of the head.  Ossification of the Ulna 1. A primary center appears in the shaft in the 8th week of fetal development and forms the greater part of the ulna. 2. A center for the lower end appears around the 5th or 6th year and joins the shaft by the 18th year. 3. The greater part of the olecranon is ossified by extension from the primary center. 4. The proximal part of the process is ossified from two centers that appear about the 10th year and join the shaft around the 15th year.  Clinical Correlation Fractures of the Ulna Fracture through the middle of the shaft of the ulna may occur alone or in combination with a similar fracture of the radius. Fracture through the upper one-third of the shaft is often accompanied with forward dislocation of the head of the radius. This is called Monteggia fracture. Fracture of the olecranon can occur because of direct injury through a fall. The fracture usually involves the trochlear articular surface. Fracture of the coronoid process is rare, and is usually associated with posterior dislocation of the elbow joint.  CARPALS The carpal bones are 8 in number, arranged in 2 rows of 4 bones each of the proximal. The bones row are (from lateral to medial) - a. Scaphoid b. Lunnate c. Traquetrium d. Pisiform The bones of the distal row are (from lateral to medial)- a. Trapezium b. Trapezoid c. Capitate d. Hamate  Bones of the Proximal Row Lunate Scaphoid The lunate bone can be distinguished 1. The scaphoid bone can be distinguished because it is shaped like the moon. because of its distinctive boat-like shape. 1. Proximally, the bone has a convex 2. The proximal part of the bone is covered by articular facet that takes part in a large, convex, articular surface for the forming the wrist joint. radius. 3. Distally and laterally the palmar surface of the bone bears a projection called the tubercle. 2. The bone articulates with the 4. The medial surface of the scaphoid scaphoid laterally, with the triquetrum medially and with the capitate articulates with the lunate bone (proximally) and with the capitate (distally). distally. 5. The distal surface of the scaphoid articulates with the trapezium (laterally) and 3. Between the areas for the capitate with the trapezoid bone (medially). and for the triquetrium, the lunate may articulate with the hamate bone.  Triquetrum 1. The triquetral bone can be distinguished from other carpal bones by its small rough cuboidal shape. Pisiform 1. This bone is 2. It has palmar, dorsal, proximal, distal, medial and lateral easily surfaces. distinguished as it is shaped like a 3. The distal part of its palmar surface articulates with the pea. pisiform bone. 4. The medial surface is directed proximally and medially, and bears a slightly convex surface that comes into contact with the articular disc of the inferior radioulnar joint and participates in forming the wrist joint. 2. Its dorsal aspect 5. Its lateral surface is also directed distally and articulates bears a single with the hamate. facet for articulation with 6. The proximal surface is also directed laterally and the triquetrum. articulates with the lunate bone.  Bones of the Distal Row Trapezium Trapezoid 1. This bone can be 1. This bone can be distinguished because it bears a distinguished from other carpal thick prominent ridge on its palmar aspect called the bones because of its small size tubercle. and its irregular (shoe-like) shape. 2. The trapezium articulates proximally and medially with 2. The trapezoid articulates the scaphoid, distally and distally with the base of the laterally with the first second metacarpal bone, metacarpal bone, distally and medially with the base of the laterally with the trapezium, second metacarpal bone and medially with the capitate and medially with the trapezoid proximally with the scaphoid bone. bone.  The Capitate Bone The Hamate Bone 1. The capitate bone is the largest carpal 1. The hamate has a prominent bone, and bears a rounded head at one end. hook-like process attached to the distal and medial part of its 2. It articulates proximally with the lunate bone, the rounded head fitting palmar aspect. into a socket formed by the lunate and scaphoid bones. 2. When viewed from the palmar aspect the hamate is triangular in 3. It articulates distally with the third shape, the apex of the triangle metacarpal bone mainly and partially being directed proximally. with the second and fourth metacarpals. 4. Its lateral aspect articulates with the 3. Proximally, the apex of the bone scaphoid (proximally) and with the may articulate with the lunate trapezoid (distally). bone, distally with the fourth and fifth metacarpal bones, medially 5. Medially, it articulates with the hamate with the triquetrum and laterally bone. with the capitate bone.  METACARPALS 1. The metacarpal bones are 5 in number. They are present in the hand. They are numbered from lateral to medial side so that the bone related to the thumb is the first metacarpal, and that related to the little finger is the fifth. 2. Each metacarpal is a miniature long bone having a shaft, a distal end and a proximal end. 3. The distal end forms a rounded head. It bears a large convex articular surface for articulation with the proximal phalanx of the corresponding digit. 4. The shaft is triangular in cross section and has medial, lateral and dorsal surfaces. 5. The bases (or proximal ends) of the metacarpal bones are irregular in shape. They articulate with the distal row of carpal bones. 6. The bases of the second and third, third and fourth, and fourth and fifth metacarpal bones also articulate with each other, forming the intermetacarpal joints.  PHALANGES 1. Each digit of the hand (except the thumb) has three phalanges: proximal, middle and distal. 2. The thumb has only two phalanges: proximal and distal. 3. Each phalanx has a distal end or head, a proximal end or base, and an intervening shaft or body.  Ossification of the Bones of the Hand 1. Each carpal bone is ossified from one centre that (as a rule) appears before birth as follows: Capitate: 2nd month Hamate: 3rd month Triquetral: 3rd year Lunate: 4th year Scaphoid: 4th to 5th year Trapezium: 4th to 5th year Trapezoid: 4th to 5th year Pisiform: About 10th year  Metacarpals Metacarpals a. Each metacarpal has a primary center for the shaft that appears in the 9th fetal week. b. The first metacarpal has a secondary center for the proximal end that appears in the 2nd or 3rd year, and unites with the shaft at about 16 years. c. The other metacarpal bones have secondary centers in their distal ends that appear at about two years of age and unite with the shaft between 16 and 18 years of age.  Phalanges Phalanges a. Each phalanx has a primary center for the shaft and a secondary center for its proximal end. b. The primary center appears first in the distal phalanges (about the 8th week), then in the proximal phalanges (about the 10th week) and lastly in the middle phalanges (about the 12th fetal week). c. The secondary centers appear first in the proximal phalanges (2nd year) and later in the middle and distal phalanges (3rd or 4th year). They unite with the shafts between 16 to 18 years of age.  Clinical Correlation 1. Fractures of Bones of the Hand Fractures of the carpal bones are rare. The scaphoid bone is the most commonly fractured carpal bone. Fracture of the metacarpals and phalanges are rare and they do, the shaft is the most vulnerable part. 2. Anomalies of limbs One or more limbs of the body may be partially(phocomelia), or completely(Amelia) absent. This condition may be produced by harmful drugs, and is seen characteristically in the children of mothers who have received the drug thalidomide during pregnancy. Absence of limb bones, in whole or in part, may also occur independently and may be the cause of deformities of the limb.  3. Limb Deformities Part of a limb may be deformed (e.g. club hand). There may be abnormal fusion between different bones of the limb. Adjoining digits may be fused (syndactyly), phalanges of a digit may be fused to one another (synphalangia). The radius and ulna may be fused to each other, or to the humerus. A digit may be abnormally large (macrodactyly) or abnormally short (brachydactyly). Supernumerary digits may be present (polydactyly). Abnormally short limbs are called achondroplasia. Sometimes bone ends are not properly formed leading to congenital dislocation at joints.