SCAPULA (SHOULDER BLADES)

SCAPULA (SHOULDER BLADES)

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-Other name of scapula is shoulder blades.

– The scapula is a thin bone.

– It is placed on posterolateral aspect of thoracic cage .

 

– Scapula has ;

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2 surfaces – Costal surface

Dorsal surface

3 borders – Superior border

Lateral border

Medial border

3 processes – superior angle

Inferior angle

Lateral or glenoid angle.

 

• Side determination

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– Lateral or glenoid angle is large and it bears the glenoid cavity.

– Dorsal surface is convex and costal surface is convex.

– Thickest lateral border runs from glenoid cavity above to inferior angle below.

 

• Features

 

* Surfaces

 

1) The costal surface or suprascapular fossa :

– It is concave and is directed medially and forwards.

– Marked by 3 longitudinal ridges.

 

2) The Dorsal surface :

– Gives attachment to spine of scapula which divides the surface into Supraspinous fossa and infraspinous fossa.

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*Borders

 

1) The Superior border :

– Thin and shorter

– It present suprascapular notch near the root of coracoid process .

 

2) The lateral border :

– Thick

– It presents infraglenoid tubercle at the upper end .

 

3) The medial border :

– Thin

– Extends from superior angle to inferior angle.

 

* Angles

 

1) The Superior angle

–  It is covered by trapezius.

2) The inferior angle

– It is covered by latissimus dorsi

3) The lateral or glenoid angle

– It is broad and bears the glenoid fossa or cavity .

 

* Processes

 

1) The spine or spinous process

–  It is a triangular plate of bone with 3 borders and 2 surfaces.

– It divides the dorsal surface of scapula into Supraspinous and infraspinous fossae.

– Posterior border is called as the crest of spine

– This crest has upper and lower lips.

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2) The acromion

 

– It has ,

2 borders  : medial and lateral

2 surfaces : superior and inferior

And a facet for clavicle.

3) The corocoid

– This process is directed forwards and slightly laterally .

– It is bent and finger-like.

 

Attachments

 

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1) Subscapularis : arises form medial two-thirds of the subscapular fossa .

2) Supraspinatus : arises from medial two-thirds of Supraspinous fossa.

3) Infraspinatus : arises from medial two-thirds of infraspinous fossa.

4) The deltoid : arises from lower border of  the crest of spine and from the lateral border of the acromion .

5) The trapezius : is inserted into upper border of the crest of spine and into the medial border of the acromion.

6) The serratus anterior : inserted along medial border of costal surface.

7) The long head of bicpes brachii : arises from supraglenoid tubercle.

–  The Short head is from lateral part of the tip of corocoid process.

8) The coracobrachialis : arises from medial part of the tip of corocoid process.

9) The pectoralis minor : inserted into the medial border and superior surface of the corocoid process.

10) The long head of triceps brachii : arises from infraglenoid tubercle.

11) Teres minor : arises from upper two-thirds of rough strip on dorsal surface along the lateral border.

12) Teres major : arises from lower one-third of rough strip on dorsal aspect of lateral border.

13) The levator scapular : is inserted along the dorsal aspect of medial border , from superior angle up to the root of spine.

14) The rhomboid minor : inserted into dorsal aspect ( medial border ) opposite to root of spine .

15) The rhomboid major : inserted into dorsal aspect ( medial border ) between root of spine and inferior angle.

16) The inferior belly of omohyoid : arises from upper border near the suprascapular notch.

17) The margin of glenoid cavity :  This gives attachment to capsule of shoulder joint and to glenoid labrum.

18) The margin of facet on medial aspect of the acromion : This gives attachment to capsule of Acromioclavicular joint .

19) Coracoacromial ligament :

– attached to the lateral border of acromion process

– attached to medial side of tip of acromion process.

20) The coracohumeral ligament : attached to root of corocoid process.

21) The coracoclavicular ligament : attached to corocoid process .

– Trapezoid part on the superior aspect

– Conoid part near the root.

22) Transverse ligament : bridges across suprascapular notch and converts it into foramen .

– The suprascapular vessels lies above this ligament.

23) The spinoglenoid ligament : bridges the spinoglenoid notch .

– The suprascapular vessels and the nerve passes deep to it.

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• Ossification

 

– The scapula ossification starts from one primary centre and seven secondary centres.

 

* Appearance of primary centre :

– Near glenoid cavity during 8 th week of development.

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* Appearance of secondary centre :

 

– During First year , th first secondary centre appears in middle of corocoid process .

– It fuses by 15 th year.

 

* Subcorocoid centre :

– It appears during 10 th year , in the root of corocoid process .

– Fuses by 16 th to 18 th years.

* Other centres

– Two for acromion , One for margin of glenoid cavity ( lower 2/3 rd ) ,One for medial border , One for inferior angle.

– These appears at puberty

– Fuses by 25 th year.

 

• Clinical anatomy

 

1) Winging of scapula

 

– Paralysis of serratus anterior causes ‘scapula winging’ .

– The arm cannot be abducted beyond 90°.

– Medial border of scapula becomes more prominent.

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2) The scaphoid scapula

 

– It is a developmental anomoly.

– Here , the medial border of scapula is concave.

 

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