HUMERUS (LONG BONE OF UPPER LIMB )
-HUMERUS (LONG BONE OF UPPER LIMB )
– It has :
• Side determination
1) Upper end is rounded ( to form head )
2) Lower end :
– Expanded from side to side
– Flattened from before backwards
3) The head is directed medially, upwards and backwards.
4) The lesser tubercle projects from front of upper end.
– It is limited laterally by the intertubercular sulcus or bicipital groove.
• FEATURES :
1) The head :
– Head is directed medially , backwards and upwards .
– Head Articulates with glenoid cavity of scapula to form Shoulder joint.
2) Anatomical neck :
– It is a line separating the head from rest of the upper end .
3) The lesser tubercle :
– It is an elevation on anterior aspect of the upper end.
4) The greater tubercle :
– It is an elevation that forms lateral part of upper end .
– Posterior aspect of greater tubercle is marked by 3 impressions ;
5) The intertubercular sulcus or bicipital groove :
– It separates the lesser tubercle medially from anterior part of greater tubercle.
– The sulcus has ,
√ medial lip
√ lateral lip .
6) The surgical neck :
– It is a narrow line separating the upper end of humerus from the shaft.
7) Morphological neck :
– It lies 0.5 cm above the surgical neck.
– Shows the position of epiphyseal line.
– It is rounded in upper half and triangular in lower half .
– It has 3 borders : Anterior border
– 3 surfaces : Anterolateral surface
Posterior surface .
* Borders :
1) Anterior border
√ Upper one-third : forms lateral lip of intertubercular sulcus.
√ Middle part : forms anterior margin of deltoid tuberosity.
√ Lower half : smooth and rounded
2) The lateral border :
√ At lower end it forms the lateral supracondylar ridge.
3) Medial border :
√ Upper part forms medial lip of intertubercular sulcus
√ At middle it has a rough strip and is continuous below with medial supracondylar ridge.
1) Anterolateral surface :
– Lies between anterior and lateral border.
– Upper half is covered by deltoid
– A little above the middle , there is a deltoid tuberosity.
– Behind the deltoid tuberosity , the radial groove which runs downwards and forwards across the surface.
2) The anteromedial surface
– Lies between anterior and medial borders
3) The posterior surface
– Lies between medial and lateral borders.
• Lower end
– It forms condyle by which is expanded from side to side.
– It has a articular and non-articular parts .
* Articular parts includes,
√ The capitulum : articulates with head of radius.
√ The trochlea : Articulates with Trochlear notch of ulna.
* Non-articular part includes ,
√The medial epicondyle
√ The lateral epicondyle
√ The lateral supracondylar ridge
√ The medial Supracondylar ridge
√ The Coronoid fossa
√ The radial fossa
√ The olecranon fossa.
1) Subscapularis : inserted into lesser tubercle.
2) Supraspinatus : inserted into greater tubercle ( upper impression )
3) Infraspinatus : inserted into greater tubercle ( middle impression )
4) Teres minor : inserted into greater tubercle ( lower impression )
5) Pectoralis major : inserted into lateral lip of intertubercular sulcus.
6) Latissimus dorsi : inserted into floor of intertubercular sulcus.
7) Teres major : inserted into medial lip of intertubercular sulcus.
8) Deltoid : inserted into deltoid tuberosity .
9) Coracobrachialis : inserted into rough area on middle of medial border.
10) Brachialis : arises from lower half of anteromedial and anterolateral surface of shaft .
11) Brachioradialis : arises from upper two-thirds of lateral supracondylar ridge.
12) Extensor carpi radialis longus : arises from the lower one-third of lateral supracondylar ridge.
13) Pronator teres : arises from lower one-third of medial Supracondylar ridge.
14) Superficial flexor muscle of forearm : arise from medial epicondyle (anterior aspect).
15) Superficial extensor muscles of forearm and supinator : lateral epicondyle.
16) Anconeus : arises from the lateral epicondyle ( posterior surface ).
17) Triceps brachii :
– Lateral head : arises from oblique ridge on upper part of posterior surface ( above radial groove ).
– Medial head : arises from posterior surface ( below radial groove).
18) Capsular ligament of shoulder joint : attached to anatomical neck except on medial side.
19) Capsular ligament of elbow joint
20) Three nerves
– the axillary nerve at surgical nec
– the radial nerve at radial groove
– the ulnar nerve behind the medial epicondyle.
– Humerus ossification starts from one primary centre and seven secondary centres.
* Primary centre
– Appears in middle of diaphysis during 8 th week of development.
* Secondary centres
• Upper end of humerus ossifies from 3 secondary centres
√ First year – one for the head
√ Second year – one for the greater tubercle
√ Fifth year – one for the lesser tubercle.
– During 6 th year , the 3 centres fuse together to form one compound epiphysis.
– During 20 th year, it fuses with the shaft .
– At the level of lower margin of the head, the epiphyseal line encircles the bone.
– This is the growing end of this bone.
• Lower end ossifies from 4 centres and form 2 epiphyses.
√ First year – one for capitulum and lateral flange of trochlea.
√ 9 th year – one for medial flange of trochlea.
√ 12 th year – one for lateral epicondyle.
– During 14 th year all three fuse to form another compound epiphysis.
– At about 16 year , it fuses with shaft.
– The centre for medial epicondyle appears during 4-6 years , forms a separate epiphysis, and fuses with shaft during 20 th year.
• CLINICAL ANATOMY
– common sites of HUMERUS (LONG BONE OF UPPER LIMB ) fracture are ; surgical neck, shaft, and supracondylar region.
* Supracondylar Fracture
– Common in young age
– It occurs due to fall on outstretched hand.
– Lower fragment displaces backwards.
– This fracture may cause injury to the median nerve.
– It may lead to volkmann’s ischemic contracture caused by brachial artery occlusion.
* The 3 bony points of normal elbow form the equilateral triangle in a flexed elbow and are in one line in an extended elbow.
* The humerus has a poor blood supply at junction of upper and middle thirds.
– Fracture at this site may show delayed union or non union .
– The head of humerus commonly dislocates anteroinferiorly.