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HUMERUS (LONG BONE OF UPPER LIMB )

HUMERUS (LONG BONE OF UPPER LIMB )

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-HUMERUS (LONG BONE OF UPPER LIMB )

– It has  :

Upper end

Lower end

Shaft.

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• 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 :

 

•Upper end

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.

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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 ;

√ Upper

√ Middle

√ Lower.

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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.

 

• Shaft

 

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– It is rounded in upper half and triangular in lower half .

– It has 3 borders : Anterior border

Lateal border

Medial border.

– 3 surfaces : Anterolateral surface

Anteromedial surface

Posterior surface .

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* 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.

 

* Surfaces

 

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 .

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* Articular parts includes,

√ The capitulum : articulates with head of radius.

√ The trochlea : Articulates with Trochlear notch of ulna.

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* Non-articular part  includes ,

√The medial epicondyle

√ The lateral epicondyle

√ The lateral supracondylar ridge

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√ The medial Supracondylar ridge

√ The Coronoid fossa

√ The radial fossa

√ The olecranon fossa.

 

• ATTACHMENTS

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1) Subscapularis : inserted into lesser tubercle.

 

2) Supraspinatus : inserted into greater tubercle ( upper impression )

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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 .

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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 ).

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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.

 

• Ossification

 

– 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.

 

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