THE SKELETON OF THE UPPER LIMB

  The skeleton of the upper limb is divided into two parts - the pectoral girdle and the freely movable part of the upper limb: pectoral girdle, includes the clavicle and the scapula, with the help of which the free part of the upper limb articulates with the torso. free part of the upper limb,includes bones of the arm (ossa brachii), bones of the forearm (ossa antebrachii) and bones of the hand(ossa manus). 

                                       PECTORAL GIRDLE

 The scapula:The scapula (“shoulder blade”) is a large, triangular flat bone on the posterior side of the rib cage, overlying ribs 2 through 7. The spine of the scapula,spina scapulae is a prominent diagonal bony ridge seen on the posterior surface. The spine strengthens the scapula, making it more resistant to bending. Above the spine is the supraspinous fossa,fossa supraspinata and below the spine is the infraspinous fossa,fossa infraspinata. The spine broadens toward the shoulder as the acromion. This process serves for the attachment of several muscles, as well as for articulation with the clavicle. Inferior to the acromion is a shallow depression, the glenoid cavity,cavitas glenoidalis into which the head of the humerus fits. The coracoid process,processus coracoideus is a thick upward projection lying superior and anterior to the glenoid cavity. The scapula has anterior(costal surface) and posterior surfaces.The anterior surface faces the ribs.On the anterior surface of the scapula is a slightly concave area known as the subscapular fossa. The posterior surface faces the skin of the back.

                 Angles of the scapula 

•  Acromial angle,angulus acromialis; sharp bend at the site where the spine of the scapula becomes continuous with the lateral margin of the acromion. 
• Inferior angle,angulus inferior; lower angle of the scapula.
•  Lateral angle,angulus lateralis; lateral angle of the scapula bearing the glenoid cavity. 
• Superior angle,angulus superior ;upper medial angle of the scapula . 

                   Margins of the scapula 

•  Medial margin,margo medialis; border of the scapula facing the vertebral column. 
• Lateral margin,margo lateralis; border of the scapula facing the humerus. 
• Superior margin,margo superior; upper border of the scapula. 

  

  DonNMU.

  Clinical application: The scapula has numerous surface features because 15 muscles attach to it. Clinically, the pectoral girdle is significant becausethe clavicle and acromion of the scapula are frequentlybroken in trying to break a fall. The acromion is used as a landmark for identifying the site for an injection in the arm. This site is chosen because the musculature of the shoulder is quite thick and contains few nerves.

                         HOW TO KNOW LEFT OR RIGHT SCAPULA 

•   Identify the glenoid cavity and place it laterally. 
•   Place the spine of the scapula posteriorly.In this way you can be able to identify the position of the scapula easily. 

           The clavicle:The slender S-shaped clavicle(“collarbone”) connects the upper extremity to the axial skeleton and holds the shoulder joint away from the trunk to permit freedom of movement. The articulation of the medial sternal extremity of the clavicle to the manubrium of the sternum is referred to as the sternoclavicular joint. The lateral acromial extremity of the clavicle articulates with the acromion of the scapula.This articulation is referred to as the acromioclavicular joint. A conoid tubercle is present on the acromial extremity of the clavicle, and a costal tuberosity is present on the inferior surface of the sternal extremity. Both processes serve as attachments for ligaments. 

 Clinical application:The long, delicate clavicle is the most commonly broken bone in the body. When a person receives a blow to the shoulder, or attempts to break a fall with an outstretched hand, the force is transmitted to the clavicle, possibly causing it to fracture. The most vulnerable part of this bone is through its center, immediately proximal to the conoid tubercle. Because the clavicle is directly beneath the skin and is not covered with muscle, a fracture can easily be palpated, and frequently seen. 

                         FREE PART OF THE UPPER LIMB 

The humerus:The humerus is the longest bone of the upper extremity.It consists of a proximal head(proximal epiphyses), which articulates with the glenoidcavity of the scapula; a body (“shaft”); and a distal end(distal epiphysis), which is modified to articulate with the two bones of the forearm. Surrounding the margin of the head is a slightly indented groove denoting the anatomical neck. The surgical neck, the constriction just below the head, is a frequent fracture site. The greater tubercle is a large knob on the lateral proximal portion of the humerus. The lesser tubercle is slightly anterior to the greater tubercle and is separated from the greater by an intertubercular groove. The tendon of the long head of the biceps brachii muscle passes through this groove. Along the lateral midregion of the body of the humerus is a roughened area, the deltoid tuberosity, for the attachment of the deltoid muscle. Small openings in the body are called nutrient foramina. The humeral condyle on the distal end of the humerus has two articular surfaces. The capitulum is the lateral rounded part that articulates with the radius. The trochlea is the pulleylike medial part that articulates with the ulna. On either side above the condyle are the lateral and medial epicondyles. The large medial epicondyle protects the ulnar nerve that passes posteriorly through the ulnar sulcus. It is popularly known as the “funny bone” because striking the elbow on the edge of a table, for example, stimulates the ulnar nerve and produces a tingling sensation. The coronoid fossa is a depression above the trochlea on the anterior surface. The olecranon fossa is a depression on the distal posterior surface. Both fossae are adapted to work with the ulna during movement of the forearm. 

              Margins(borders): 

• Medial margin,margo medialis: inner margin of the humerus continuous distally with the medial supracondylar ridge.
•  Lateral margin,margo lateralis: outer margin of the humerus continuous distally with the lateral supracondylar ridge. 

                Surfaces: 

•  Anteromedial surface,facies anteromedialis: surface of the humerus lying medial to the prolongation of the crest of the greater tubercle. 
•  Anterolateral surface,facies anterolateralis: surface of the humerus located lateral to the prolongation of the crest of the greater tubercle. 
• posterior surface,facies posterior. 
  

   clinical application:The medical term for tennis elbow is lateral epicondylitis, which means inflammation of the tissues surrounding the lateral epicondyle of the humerus. At least six muscles that control backward (extension) movement of the wrist and finger joints originate on the lateral epicondyle. Repeated strenuous contractions of these muscles, as in stroking with a tennis racket, may strain the periosteum and muscle attachments, resulting in swelling, tenderness, and pain around the epicondyle. Binding usually eases the pain, but only rest can eliminate the causative factor, and recovery generally follows. 

        HOW TO KNOW IF A HUMERUS IS LEFT OR RIGHT. 
   clue I 
 1. Identify the head of the humerus and the medial epicondyle.               These two should be medially placed. 
 2.Identify the coronoid and radial fossae. These two should be               anteriorly placed with the olecranon fossa placed posteriorly. In        this position, we can determine if its left or right. 
 clue II 
      1. place the head of the humerus and the medial epicondyle at               the medial position. 
      2.the olecranon fossa should be posteriorly placed. 
      3.If the head of the humerus faces left,it means it is a right                  humerus and vice versa. 

   THE RADIUS:The radius consists of a body,corpus radii with a small proximal end, and a large distal end. A proximal disc-shaped head articulates with the capitulum of the humerus and the radial notch of the ulna. The prominent tuberosity of radius (radial tuberosity), for attachment of the biceps brachii muscle, is located on the medial side of the body, just below the head. On the distal end of the radius is a double-faceted surface for articulation with the proximal carpal bones. The distal end of the radius also has a styloid process on the lateral tip and an ulnar notch on the medial side that receives the distal end of the ulna. The styloid processes on the ulna and radius provide lateral and medial stability for articulation at the wrist. 
                                 Surfaces:

•  Anterior surface,facies anterior.
•  Posterior surface,facies posterior. 
•  Lateral surface, facies lateralis. 

                                 Borders: 

• Anterior border,margo anterior. 
• Posterior border,margo posterior. 
• Interosseous border,margo interosseous.

  Clinical application: When a person falls, the natural tendency is to extend the hand to break the fall. This reflexive movement frequently results in fractured bones. Common fractures of the radius include a fracture of the head, as it is driven forcefully against the capitulum; a fracture of the neck; or a fracture of the distal end (Colles’ fracture), caused by landing on an outstretched hand.

When falling, it is less traumatic to the body to withdraw the appendages,bend the knees, and let the entire body hit the surface.

Athletes learn that this is the safe way to fall.

                          how to know left and right radius

• The proximal end should face up and the distal end, down.
• Place the radial tuberosity medially.
• Identify the nutrient foramen and place it anteriorly.i.e away from you.
• The radial styloid process should also be at the lateral position.

   ULNA:The proximal end of the ulna articulates with the humerus and radius. A distinct depression, the trochlear notch, articulates with the trochlea of the humerus. The coronoid process forms the anterior lip of the trochlear notch, and the olecranon forms the posterior portion. Lateral and inferior to the coronoid process is the radial notch, which accommodates the head of the radius.

   On the tapered distal end of the ulna is a knobbed portion, the head, and a knoblike projection, the styloid process. The ulna articulates at both ends with the radius.In the forearm, it is located medially.

DonNMU.

   

                                               

                                          how to know left and right ulna

• The proximal and distal epiphysis should first of all be placed at the right position;proximal up, distal down.
• face the trochlear notch away from you and look at the olecranon.
• Check to see which side the radial notch is.
• If it is on the right, it a right ulna and vice versa.

                                     BONES OF THE HAND

The hand contains 27 bones, grouped into the carpus, metacarpus,

and phalanges.

   Carpus:The carpus, or wrist, or carpal bone contains eight bones arranged in two transverse rows of four bones each. 

  The proximal row, naming from the lateral (thumb) to the medial      side, consists of the: 

• scaphoid (navicular),os scaphoideum
• lunate,os lunatum
•  triquetrum,os triquetrum and 
• pisiform,os pisiforme.The pisiform forms in a tendon as a sesamoid bone. 

     The distal row, from lateral to medial, consists of the  

• trapezium,os trapezium (greater multangular), 
• trapezoid,os trapezoideum (lesser multangular), 
• capitate,os capitatum and 
• hamate,os hamatum. The scaphoid and lunate of the proximal row articulate with the distal end of the radius.

     Metacarpus:The metacarpus, or palm of the hand, contains five metacarpal bones. Each metacarpal bone consists of a proximal base, a body, and a distal head that is rounded for articulation with the base of each proximal phalanx. The heads of the metacarpal bones are distally located and form the knuckles of a clenched fist.

   The phalanges:The 14 phalanges are the bones of the digits. A single finger bone is called a phalanx (fa'langks). The phalanges of the fingers are arranged in a proximal row, a middle row, and a distal row.

  The thumb, or pollex (adjective, pollicis), lacks a middle phalanx.

The digits are sequentially numbered I to V starting with the

thumb—the lateral side, in reference to anatomical position.

   

   Clinical application: The hand is a marvel of structural complexity that can withstand considerable abuse. Other than sprained ligaments of the fingers and joint dislocations, the most common bone injury is a fracture to the scaphoid—a wrist bone that accounts for about 70% of carpal fractures. When immobilizing the wrist joint, the wrist is positioned in the plane of relaxed function. This is the position in which the hand is about to grasp an object between the thumb and index finger.

                                    Kamal Umar Labaran(Med)

                           Donetsk National Medical University.