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INTRODUCTION TO UPPER LIMB ANATOMY

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GENERAL DESCRIPTION

• The upper limb is associated with the lateral aspect of the lower portion of the neck.

• It is suspended from the trunk by muscles and a small skeletal articulation between the clavicle and the sternum-the sternoclavicular joint.

• Based on the position of its major joints and component bones, the upper limb is divided into shoulder, arm, forearm, and hand.

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• The shoulder is the area of upper limb attachment to the trunk .

• The arm is the part of the upper limb between the shoulder and the elbow joint;

• The forearm is between the elbow joint and the wrist joint;

• While the hand is distal to the wrist joint.

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• The axilla, cubital fossa, and carpal tunnel are significant areas of transition between the different parts of the limb.

• Important structures pass through, or are related to, each of these areas.

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Regional anatomy of the upper limb

SHOULDER;• The shoulder is the region of upper limb

attachment to the trunk and neck.• The bone framework of the shoulder consists

of: the clavicle and scapula, which form the

pectoral girdle (shoulder girdle); and the proximal end of the humerus.

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• The superficial muscles of the shoulder consist of the trapezius and deltoid muscles, which together form the smooth muscular contour over the lateral part of the shoulder.

• These muscles connect the scapula and clavicle to the trunk and to the arm, respectively.

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Bones of the shoulder girdle• Clavicle;• The clavicle is the only bony attachment

between the trunk and the upper limb. • It is palpable along its entire length and has a

gentle elongated S-shaped contour.• Its sternal (medial) end is enlarged and

triangular where it articulates with the manubrium of the sternum to form the sternoclavicular (SC) joint.

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• Its acromial (lateral) end is flat where it articulates with the acromion to form the acromioclavicular (AC) joint.

• The medial two-thirds of the body (shaft) of the clavicle are convex anteriorly, whereas the lateral third is flattened and concave anteriorly.

• These curvatures increases the resilience of the clavicle and give it the appearance of an elongated capital "S."

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• Although designated as a long bone, the clavicle has no medullary (marrow) cavity.

• It consists of spongy (cancellous) bone with a shell of compact bone.

• The clavicle has 2 surfaces; a smooth superior surface lying just deep to the skin and the platysma muscle.

• The inferior surface of the clavicle is rough because strong ligaments bind it to the 1st rib near its sternal end and suspend the scapula from its acromial end.

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• The conoid tubercle, near the acromial end of the clavicle, gives attachment to the conoid ligament- the medial part of the coracoclavicular ligament.

• The subclavian groove in the medial third of the clavicle is the site of attachment of the subclavius muscle.

• More medially is the impression for the costoclavicular ligament, which binds the 1st rib to the clavicle.

• Near the acromial end of the clavicle is the trapezoid line, to which the trapezoid ligament attaches; it is the lateral part of the coracoclavicular ligament.

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Applied Anatomy

Variations of the Clavicle; • The clavicle varies in shape more than most

other long bones.• It is thicker and more curved in manual workers,

and the sites of muscular attachments are more marked.

• The right clavicle is thicker and stronger than the left and is usually shorter.

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Fracture of the Clavicle;• The clavicle is commonly fractured, often by

an indirect force resulting from violent impacts to the outstretched hand during a fall transmitted through the bones of the hand, forearm and arm to the shoulder- or by falls directly onto the shoulder itself.

• The weakest part of the clavicle is the junction of its middle and lateral thirds which makes this point more susceptible to fracture

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Ossification of the Clavicle;• The clavicle is the first long bone to begin to

develop, during the 5th and 6th embryonic weeks in condensed mescnchyme.

• It completely ossifies by 25th to 31st years of life making it the last of the epiphyses of long bones to fuse.

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SCAPULA

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• The scapula or shoulder blade is a triangular flat bone that lies at the posteriolateral aspect of the thorax where it covers from the 2nd-7th ribs.

• It comprises of: three angles (lateral, superior, and inferior); three borders (superior, lateral, and medial); two surfaces (costal/anterior and posterior); and three processes (acromion, spine, and coracoid

process)

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Coastal surface

Posterior surface

Spine of scapula

Infraspinous fossa

Supraspinous fossa

AcromionCoracoid process

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• The convex posterior surface is evenly divided into two by the spine of the scapula into a smaller supraspinous fossa and a much larger infraspinous fossa.

• These three fossae gives attachments to some fleshy muscles of the upper limb.

• A thick projecting ridge of bone called the spine of the scapula continues laterally as the flat expanded acromion which articulates with acromial end of the clavicle forming the acromioclavicular joint.

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• Superiorlaterally, the scapula forms the shallow glenoid cavity which articulates with the head of the humerus to form the glenohumeral/shoulder joint.

• Projecting anterolaterally to this cavity is a structure that resembles a bending finger pointing to the shoulder.

• This structure is called coracoid process.

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Coastal surface

Posterior surface

Spine of scapula

Infraspinous fossa

Supraspinous fossa

AcromionCoracoid process

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Angles and borders of scapulae• The scapula has three borders namely median,

lateral and superior.• Also has three angles namely; superior, lateral

and inferior angles.• In its anatomical position the thin median

border of the scapula runs parallel to and approximately 5cm lateral to the spinous process of the thoracic vertebrae.

• Hence, the median border is usually referred to as the VERTEBRAE BORDER.

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• From the inferior angle. The lateral border runs superiolaterally towards the apex of the axilla, hence sometimes called the AXILLA BORDER.

• The lateral border terminates in the truncated lateral angle of the scapula, where the thick glenoid cavity is located.

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• The broad process adjacent to the cavity is the head of the glenoid cavity while the constricted part between the head and the body is the NECK.

• The superior border is marked by the suprascapular notch near the junction of the medial 2/3rd and the lateral 1/3rd.

• It is the thinnest and shortest of the three borders.

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• The glenoid cavity is a shallow concave, oval fossa of approximately 4cm long and 2-3cm wide; for the reception of the head of the humerus bone.

• the cavity faces anterolateraly and slightly superiorly.

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• Fracture of the scapula;• In most cases the scapulae are well protected

by muscles and its associated thoracic wall, therefore, most fractures of the scapulae involves the protruding subcutaneous acromion.

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HUMERUS

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• The humerus (arm bone), the largest bone in the upper limb, articulates with the scapula at the scapulohumeral (shoulder) joint and the radius and ulna at the elbow joint.

• Is composed of two extremities; proximal and distal.

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Humerus

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Proximal humerus

• The proximal end of the humerus consists of the head, the anatomical neck, the greater and lesser tubercles, the surgical neck, and the superior half of the shaft of humerus.

• The head is half-spherical in shape and projects medially and somewhat superiorly to articulate with the much smaller glenoid cavity of the scapula.

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• The anatomical neck is very short and is formed by a narrow constriction immediately distal to the head.

• It lies between the head and the greater and lesser tubercles laterally, and between the head and the shaft more medially.

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Greater and lesser tubercles; • The greater and lesser tubercles are

prominent landmarks on the proximal end of the humerus and serve as attachment sites for the four rotator cuff muscles of the glenohumeral joint.

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• The greater tubercle is lateral in position. • Its superior surface and posterior surface are

marked by three large smooth facets for muscle tendon attachment:

the superior facet is for attachment of the supraspinatus muscle;

the middle facet is for attachment of infraspinatus;

the inferior facet is for attachment of teres minor.

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• The lesser tubercle is anterior in position and its surface is marked by a large smooth impression for attachment of the subscapularis muscle.

• A deep intertubercular sulcus (bicipital groove) separates the lesser and greater tubercles and continues inferiorly onto the proximal shaft of the humerus .

• The tendon of the long head of the biceps brachii passes through this sulcus.

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• Roughenings on the lateral and medial lips and on the floor of the intertubercular sulcus mark sites for the attachment of the pectoralis major, teres major, and latissimus dorsi muscles, respectively.

• The lateral lip of the intertubercular sulcus is continuous inferiorly with a large V-shaped deltoid tuberosity on the lateral surface of the humerus midway along its length, which is where the deltoid muscle inserts onto the humerus.

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• In approximately the same position, but on the medial surface of the bone, there is a thin vertical roughening for attachment of the coracobrachialis muscle.

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Surgical neck

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Surgical neck • One of the most important features of the proximal end of the

humerus is the surgical neck. • This region is oriented in the horizontal plane between the

expanded proximal part of the humerus (head, anatomical neck, and tubercles) and the narrower shaft.

• The axillary nerve and the posterior circumflex humeral artery, which pass into the deltoid region from the axilla, do so immediately posterior to the surgical neck.

• Because the surgical neck is weaker than more proximal regions of the bone, it is one of the sites where the humerus commonly fractures. The associated nerve (axillary) and artery (posterior circumflex humeral) can be damaged by fractures in this region.

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Shaft and distal end of the humerus

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• The body/shaft of the humerus has two prominent features:

• the deltoid tuberosity, laterally, for attachment of the deltoid muscle, and the oblique radial groove, posteriorly, in which the radial nerve and deep artery of the arm (Profunda brachii) lie as they pass between the medial and the long and then the lateral heads of the triceps brachii muscle.

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• Distally, the bone becomes flattened, and these borders expand as the lateral supraepicondylar ridge (lateral supracondylar ridge) and the medial supraepicondylar ridge (medial supracondylar ridge).

• The lateral supraepicondylar ridge is more pronounced than the medial and is roughened for the attachment of muscles found in the posterior compartment of the forearm.

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The condyle • The two articular parts of the condyle, the

capitulum and the trochlea, articulate with the two bones of the forearm.

• The capitulum articulates with the radius of the forearm.

• The trochlea articulates with the ulna of the forearm.

• It is pulley shaped and lies medial to the capitulum.

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The two epicondyles • The medial epicondyle, a large bony protuberance, is the

major palpable landmark on the medial side of the elbow, and projects medially from the distal end of the humerus.

• On its surface, it bears a large oval impression for the attachment of muscles in the anterior compartment of the forearm.

• The ulnar nerve passes from the arm into the forearm around the posterior surface of the medial epicondyle and can be palpated against the bone in this location.

• The lateral epicondyle is much less pronounced than the medial epicondyle.

• It is lateral to the capitulum and has a large irregular impression for the attachment of muscles in the posterior compartment of the forearm.

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• The three fossae • Three fossae occur superior to the trochlea and

capitulum on the distal end of the humerus. • The radial fossa is the least distinct of the fossae and

occurs immediately superior to the capitulum on the anterior surface of the humerus.

• The coronoid fossa is adjacent to the radial fossa and is superior to the trochlea.

• The largest of the fossae, the olecranon fossa, occurs immediately superior to the trochlea on the posterior surface of the distal end of the humerus.

• These three fossae accommodate projections from the bones in the forearm during movements of the elbow joint.

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GOODMORNING