View source for Scapula

{{Short description|Bone that connects the humerus and clavicle}}
{{About|the bone|the Roman Catholic sacramental pendant|Scapular|the Roman Governor of Britain|Publius Ostorius Scapula}}
{{Redirect|Shoulderblade|the community in the United States|Shoulderblade, Kentucky}}
{{Infobox bone
| Name          = Scapula
| Latin         = scapula <br /> (omo)
| Image         = Pectoral girdle front diagram.svg
| Caption       =
| Image2        = Scapula - posterior view2.png
| Caption2      = The upper picture is an anterior (from the front) view of the [[thorax]] and [[shoulder girdle]]. The lower picture is a posterior (from the rear) view of the thorax (scapula shown in red).
| Articulations =
}}
The '''scapula''' ({{plural form}}: '''scapulae''' or '''scapulas'''<ref>O.D.E. 2nd Ed. 2005</ref>), also known as the '''shoulder blade''', is the [[bone]] that connects the [[humerus]] (upper arm bone) with the [[clavicle]] (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side of the body being roughly a mirror image of the other. The name derives from the [[Classical Latin]] word for [[trowel]] or small [[shovel]], which it was thought to resemble.

In compound terms, the prefix '''omo-''' is used for the shoulder blade in medical terminology. This prefix is derived from ὦμος (ōmos), the Ancient Greek word for shoulder, and is cognate with the Latin {{lang|la|(h)umerus}}, which in Latin signifies either the shoulder or the upper arm bone.

The scapula forms the back of the [[shoulder girdle]]. In humans, it is a [[flat bone]], roughly triangular in shape, placed on a posterolateral aspect of the [[thoracic cage]].<ref>{{Cite web|url=http://www.ehealthstar.com/anatomy/shoulder-blade-scapula|title=Scapula (Shoulder Blade) Anatomy, Muscles, Location, Function {{!}} EHealthStar|website=www.ehealthstar.com|date=2 December 2014|access-date=2016-03-17}}</ref>

== Structure ==
The scapula is a thick, flat bone lying on the thoracic wall that provides an attachment for three groups of muscles: intrinsic, extrinsic, and stabilizing and rotating muscles. 

The intrinsic muscles of the scapula include the muscles of the [[rotator cuff]](SITS muscle)—the subscapularis, [[supraspinatus muscle|supraspinatus]], infraspinatus and teres minor.<ref>Marieb, E. (2005). Anatomy & Physiology (2nd ed.). San Francisco, CA: Pearson Benjamin Cummings.</ref> These muscles attach to the surface of the scapula and are responsible for the internal and external rotation of the [[shoulder joint]], along with [[humerus|humeral]] abduction.

The extrinsic muscles include the [[biceps]], [[Triceps brachii muscle|triceps]], and [[deltoid muscle]]s and attach to the [[coracoid process]] and supraglenoid tubercle of the scapula, infraglenoid tubercle of the scapula, and [[spine of the scapula]]. These muscles are responsible for several actions of the glenohumeral joint.

The third group, which is mainly responsible for stabilization and rotation of the scapula, consists of the [[trapezius]], [[Serratus anterior muscle|serratus anterior]], [[Levator scapulae muscle|levator scapulae]], and [[rhomboid muscles]]. These attach to the medial, superior, and inferior borders of the scapula.

The head, processes, and the thickened parts of the bone contain [[cancellous]] tissue; the rest consists of a thin layer of compact tissue.

The central part of the supraspinatus fossa and the upper part of the [[infraspinatous fossa]], but especially the former, are usually so thin in humans as to be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent muscles are separated only by fibrous tissue. The scapula has two surfaces, three borders, three angles, and three processes.

=== Surfaces ===
[[File:Anatomy of Scapula.gif|thumb|3d model of scapula, along with annotations showing the various parts of the scapula]]

====Front or subscapular fossa====
The front of the scapula (also known as the costal or ventral surface) has a broad concavity called the '''subscapular fossa''', to which the [[subscapularis muscle]] attaches. The medial two-thirds of the fossa have 3 longitudinal oblique ridges, and another thick ridge adjoins the lateral border; they run outward and upward. The ridges give attachment to the tendinous insertions, and the surfaces between them to the fleshy fibers, of the subscapularis muscle. The lateral third of the fossa is smooth and covered by the fibers of this muscle.

At the upper part of the fossa is a transverse depression, where the bone appears to be bent on itself along a line at right angles to and passing through the center of the [[glenoid cavity]], forming a considerable angle, called the subscapular angle; this gives greater strength to the body of the bone by its arched form, while the summit of the arch serves to support the [[spine of scapula|spine]] and [[acromion]].

The costal surface superior of the scapula is the origin of 1st digitation for the serratus anterior origin.

{| class="wikitable" align="left"
|+ Figure 1 : Left scapula. Costal surface.
| [[File:Left scapula - close-up - animation - stop at anterior surface.gif|220px]]
|| [[File:Gray202.png|152px]]
|| [[File:Scapula ant numbered.png|175px]]
|| {{ordered list |[[Subscapular fossa]] |[[Glenoid cavity]] |[[Coracoid process]] |[[Acromion]] |[[Superior border of scapula|Superior border]] |[[Suprascapular notch|Scapular notch]] |[[Superior angle of scapula|Superior angle]] |[[Medial border of scapula|Medial border]] |[[Inferior angle of the scapula|Inferior angle]] |[[Lateral border of the scapula|Lateral border]] |[[Infraglenoid tubercle]]}}
|}
{{Clear}}

====Back====
The back of the scapula (also called the dorsal or posterior surface) is arched from above downward, and is subdivided into two unequal parts by the spine of the scapula. The portion above the spine is called the [[supraspinous fossa]], and that below it the [[infraspinous fossa]]. The two fossae are connected by the [[spinoglenoid notch]], situated lateral to the root of the spine.
* The ''supraspinous fossa'', above the spine of scapula, is concave, smooth, and broader at its vertebral than at its humeral end; its medial two-thirds give origin to the [[Supraspinatus]]. At its lateral surface resides the spinoglenoid fossa which is situated by the medial margin of the [[glenoid fossa of scapula|glenoid]]. The spinoglenoid fossa houses the [[suprascapular canal]] which forms a connecting passage between the [[suprascapular notch]] and the [[spinoglenoid notch]] conveying the [[suprascapular nerve]] and vessels.<ref>{{cite journal |last1=Al-Redouan |first1=Azzat |last2=Holding |first2=Keiv |last3=Kachlik |first3=David |title="Suprascapular canal": Anatomical and topographical description and its clinical implication in entrapment syndrome |journal=Annals of Anatomy |date=2021 |volume=233 |page=151593 |doi=10.1016/j.aanat.2020.151593 |pmid=32898658 |doi-access= }}</ref>    
* The ''infraspinous fossa'' is much larger than the preceding; toward its vertebral margin a shallow concavity is seen at its upper part; its center presents a prominent convexity, while near the axillary border is a deep groove which runs from the upper toward the lower part. The medial two-thirds of the fossa give origin to the [[Infraspinatus]]; the lateral third is covered by this muscle.

There is a ridge on the outer part of the back of the scapula. This runs from the lower part of the glenoid cavity, downward and backward to the vertebral border, about 2.5&nbsp;cm above the inferior angle. Attached to the ridge is a fibrous septum, which separates the [[infraspinatus muscle]] from the [[Teres major]] and [[Teres minor]] muscles. The upper two-thirds of the surface between the ridge and the axillary border is narrow, and is crossed near its center by a groove for the scapular circumflex vessels; the [[Teres minor]] attaches here.

The broad and narrow portions above alluded to are separated by an oblique line, which runs from the axillary border, downward and backward, to meet the elevated ridge: to it is attached a fibrous septum which separates the [[Teres (disambiguation)|Teres]] muscles from each other.

Its lower third presents a broader, somewhat triangular surface, the '''inferior angle of the scapula''', which gives origin to the [[Teres major]], and over which the [[Latissimus dorsi]] glides; frequently the latter muscle takes origin by a few fibers from this part.
{| class="wikitable" align="left"
|+Figure 2 : Left scapula. Dorsal surface.
|-
| [[File:Left scapula - close-up - animation - stop at posterior surface.gif|220px]] || [[File:Gray203.png|153px]] || [[File:Scapula post numbered.png|172px]]
| {{ordered list |[[Supraspinous fossa]] |[[Spine of scapula|Spine]] |[[Infraspinous fossa]] |[[Superior border of scapula|Superior border]] |[[Superior angle of scapula|Superior angle]] |[[Medial border of scapula|Medial border]] |[[Inferior angle of the scapula|Inferior angle]] |[[Lateral border of the scapula|Lateral border]] |[[Lateral angle of the scapula|Lateral angle]] |[[Acromion]] |[[Coracoid process]] |Origin of [[teres major muscle]] |Origin of [[teres minor muscle]]}}
|}
{{Clear}}

====Side====
The [[acromion]] forms the summit of the shoulder, and is a large, somewhat triangular or oblong process, flattened from behind forward, projecting at first laterally, and then curving forward and upward, so as to overhang the glenoid cavity.
{| class="wikitable" align="left"
|+Figure 3 : Left scapula. Lateral surface.
|-
| [[File:Left scapula - close-up - animation - stop at lateral surface.gif|260px]] || [[File:Gray205 left scapula lateral view.png|112px]] || [[File:LeftScapulaLateral.jpg|146px]]
| {{ordered list |[[Coracoid process]] |[[Glenoid cavity]] |[[Supraspinous fossa]] |[[Acromion]] |[[Infraspinous fossa]] |[[Inferior angle of the scapula|Inferior angle]] |[[Lateral border of the scapula|Lateral border]]}}
|}
{{Clear}}

=== Angles ===
There are 3 angles:

The '''superior angle of the scapula''' or '''medial angle''', is covered by the [[trapezius muscle]]. This angle is formed by the junction of the [[Superior border of scapula|superior]] and [[Medial border of scapula|medial borders]] of the scapula. The superior angle is located at the approximate level of the [[Thoracic vertebrae#Second thoracic vertebra|second]] [[Thoracic vertebrae|thoracic vertebra]]. The superior angle of the scapula is thin, smooth, rounded, and inclined somewhat lateralward, and gives attachment to a few fibers of the [[levator scapulae muscle]].<ref name="Gray's Anatomy 1918">{{cite book | title=Anatomy of the Human Body, 20th ed. / thoroughly rev. and re-edited by Warren H. Lewis. | publisher=Lea & Febiger | author=Gray, Henry | year=1918 | location=Philadelphia | pages=206|ol = 24786057M}}</ref>

The '''inferior angle of the scapula''' is the lowest part of the scapula and is covered by the [[latissimus dorsi muscle]]. It moves forwards round the chest when the arm is abducted. The inferior angle is formed by the union of the medial and lateral borders of the scapula. It is thick and rough and its posterior or back surface affords attachment to the [[teres major]] and often to a few fibers of the latissimus dorsi. The [[Anatomical terms of location#Usage in human anatomy|anatomical plane]] that passes vertically through the inferior angle is named the [[scapular line]].

The '''lateral angle of the scapula''' or '''glenoid angle''', also known as the '''head of the scapula''', is the thickest part of the scapula. It is broad and bears the [[glenoid fossa]] on its articular surface which is directed forward, laterally and slightly upwards, and articulates with the [[head of the humerus]]. The inferior angle is broader below than above and its vertical diameter is the longest. The surface is covered with cartilage in the fresh state; and its margins, slightly raised, give attachment to a [[fibrocartilaginous]] structure, the [[glenoidal labrum]], which deepens the cavity. At its apex is a slight elevation, the [[supraglenoid tuberosity]], to which the long head of the [[biceps brachii]] is attached.<ref name="Al-Redouan and Kacklik 2022">{{cite journal |last1=Al-Redouan |first1=Azzat |last2=Kachlik |first2=David |title=Scapula revisited: new features identified and denoted by terms using consensus method of Delphi and taxonomy panel to be implemented in radiologic and surgical practice |journal=J Shoulder Elbow Surg |date=2022 |volume=31 |issue=2 |page=e68-e81 |doi=10.1016/j.jse.2021.07.020 |pmid=34454038 |url=https://www.jshoulderelbow.org/article/S1058-2746(21)00636-4/fulltext|url-access=subscription }}</ref>

The '''anatomic neck of the scapula''' is the slightly constricted portion which surrounds the head and is more distinct below and behind than above and in front. The '''surgical neck of the scapula''' passes directly medial to the base of the coracoid process.<ref name="FrichLarsen2017">{{cite journal|last1=Frich|first1=Lars Henrik|last2=Larsen|first2=Morten Schultz|title=How to deal with a glenoid fracture|journal=EFORT Open Reviews|volume=2|issue=5|year=2017|pages=151–157|issn=2396-7544|doi=10.1302/2058-5241.2.160082|pmid=28630753|pmc=5467683|doi-access=free}}</ref>

<gallery>
File:Superior angle of left scapula01.png|Superior angle shown in red
File:Head of scapula02.png|Lateral angle shown in red
File:Scapula ant - anatomical neck and surgical neck.png|Anatomic neck: red, Surgical neck: purple
File:Inferior angle of the left scapula01.png|Inferior angle shown in red

</gallery>

=== Borders ===
{{anchor|border}}{{anchor|Lateral border of scapula}}{{anchor|Superior border of scapula}}{{anchor|Axillary border of scapula}}{{anchor|Medial border of scapula}}

There are three borders of the scapula:
* The '''superior border''' is the shortest and thinnest; it is concave, and extends from the [[superior angle]] to the base of the [[coracoid process]]. It is referred to as the cranial border in animals.
::At its lateral part is a deep, semicircular notch, the [[scapular notch]], formed partly by the base of the [[coracoid process]]. This notch is converted into a [[foramen]] by the [[superior transverse scapular ligament]], and serves for the passage of the [[suprascapular nerve]]; sometimes the ligament is [[ossified]].
::The adjacent part of the superior border affords attachment to the [[omohyoideus]].

<gallery>
File:Superior border of left scapula01.png|[[#Costal (Front, Ventral, Anterior)|Costal surface of left scapula]]. Superior border shown in red.
File:Superior border of left scapula - animation01.gif|Left scapula. Superior border shown in red.
File:Superior border of scapula - animation02.gif|Animation.  Superior border shown in red.

</gallery>
* The '''axillary border''' (or "lateral border") is the thickest of the three. It begins above at the lower margin of the [[glenoid cavity]], and inclines obliquely downward and backward to the inferior angle. It is referred to as the caudal border in animals.
::It begins above at the lower margin of the [[glenoid cavity]], and inclines obliquely downward and backward to the [[inferior angle]].
::Immediately below the glenoid cavity is a rough impression, the [[infraglenoid tuberosity]], about {{convert|2.5|cm|0|abbr=on}}. in length, which gives origin to the long head of the [[triceps brachii]]; in front of this is a longitudinal groove, which extends as far as the lower third of this border, and affords origin to part of the [[subscapularis]].
::The inferior third is thin and sharp, and serves for the attachment of a few fibers of the [[teres major]] behind, and of the [[subscapularis]] in front.
<gallery>
File:Lateral border of left scapula01.png|[[#Dorsal (Back, Posterior)|Dorsal surface of left scapula]]. Lateral border shown in red.
File:Lateral border of left scapula - animation.gif|Left scapula. Lateral border shown in red.
File:Lateral border of scapula - animation.gif|Animation. Lateral border shown in red.

</gallery>
* The '''medial border''' (also called the vertebral border or medial margin) is the longest of the three borders, and extends from the superior angle to the inferior angle.<ref name="Shuenke 2010">{{Cite book|title = Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System|last = Shuenke|first = Michael|publisher = Everbest Printing Ltd.|year = 2010|isbn = 978-1-60406-286-1|location = New York}}</ref> In animals it is referred to as the '''dorsal border'''.

::Four muscles attach to the medial border. [[Serratus anterior]] has a long attachment on the anterior lip. Three muscles insert along the posterior lip, the [[levator scapulæ|levator scapulae]] (uppermost), [[Rhomboid minor muscle|rhomboid minor]] (middle), and to the [[rhomboideus major|rhomboid major]] (lower middle).<ref name="Shuenke 2010" />
<gallery>
 File:Medial boder of left scapula - animation.gif|Left scapula. Medial border shown in red.
 File:Medial boder of scapula - animation.gif|Animation. Medial border shown in red.
 File:Medial border of scapula01.png|Still image. Medial border shown in red.
 File:Levator scapulae.png|[[Levator scapulae muscle]] (red)
 File:Rhomboideus minor.png|[[Rhomboid minor muscle]] (red)
 File:Rhomboideus major.png|[[Rhomboid major muscle]] (red)
</gallery>

=== Development ===
[[File:Gray206.png|thumb|'''Figure 5 :''' Plan of ossification of the scapula. From seven centers.]]

The scapula is [[ossified]] from 7 or more centers: one for the body, two for the [[coracoid process]], two for the [[acromion]], one for the vertebral border, and one for the inferior angle. Ossification of the body begins about the second month of fetal life, by an irregular quadrilateral plate of bone forming, immediately behind the [[glenoid cavity]]. This plate extends to form the chief part of the bone, the [[Spine of scapula|scapular spine]] growing up from its [[dorsal surface]] about the third month. Ossification starts as membranous ossification before birth.<ref>{{cite web|url=http://www.gehealthcare.com/|title=GE Healthcare - Home|website=www.gehealthcare.com}}</ref><ref>{{cite book |url=https://books.google.com/books?id=t70Ij7jHLIkC&q=%22membranous+ossification%22+scapula&pg=PA97|title=Facial Trauma|isbn=978-0-8247-5008-4|last1=Thaller|first1=Seth|last2=Scott Mcdonald|first2=W|date=2004-03-23}}</ref> After birth, the cartilaginous components would undergo [[endochondral]] [[ossification]]. The larger part of the scapula undergoes membranous ossification.<ref>{{cite web|url=http://www.medcyclopaedia.com/library/topics/volume_vii/o/ossification.aspx|archive-url=https://archive.today/20110526162035/http://www.medcyclopaedia.com/library/topics/volume_vii/o/ossification.aspx|url-status=dead|archive-date=2011-05-26|title=Ossification|publisher=[[General Electric|GE]]|work=Medcyclopaedia}}</ref> Some of the outer parts of the scapula are cartilaginous at birth, and would therefore undergo endochondral ossification.<ref>{{cite web|url=http://www.bartleby.com/107/50.html|title=II. Osteology. 6a. 2. The Scapula (Shoulder Blade). Gray, Henry. 1918. Anatomy of the Human Body.}}</ref>

At birth, a large part of the scapula is osseous, but the glenoid cavity, the coracoid process, the acromion, the vertebral border and the inferior angle are [[cartilaginous]]. From the 15th to the 18th month after birth, ossification takes place in the middle of the coracoid process, which as a rule becomes joined with the rest of the [[bone]] about the 15th year.

Between the 14th and 20th years, the remaining parts ossify in quick succession, and usually in the following order: first, in the root of the coracoid process, in the form of a broad scale; secondly, near the base of the acromion; thirdly, in the inferior angle and contiguous part of the vertebral border; fourthly, near the outer end of the acromion; fifthly, in the vertebral border.
The base of the acromion is formed by an extension from the spine; the two [[Nucleus (cell)|nuclei]] of the acromion unite, and then join with the extension from the spine. The upper third of the glenoid cavity is ossified from a separate center (sub coracoid), which appears between the 10th and 11th years and joins between the 16th and the 18th years. Further, an [[epiphysial plate]] appears for the lower part of the glenoid cavity, and the tip of the coracoid process frequently has a separate nucleus. These various [[epiphyses]] are joined to the bone by the 25th year.

Failure of bony union between the acromion and spine sometimes occurs (see [[os acromiale]]), the junction being effected by [[fibrous tissue]], or by an imperfect articulation; in some cases of supposed [[fracture]] of the acromion with ligamentous union, it is probable that the detached segment was never united to the rest of the [[bone]].

{{blockquote|''"In terms of comparative anatomy the human scapula represents two bones that have become fused together; the (dorsal) scapula proper and the (ventral) coracoid. The epiphyseal line across the glenoid cavity is the line of fusion. They are the counterparts of the ilium and ischium of the pelvic girdle."''|R. J. Last – 'Last's Anatomy}}

== Function ==
The following muscles attach to the scapula:

{| class="sortable wikitable"
! Muscle !! Direction !! Region
 |-
 | [[Pectoralis Minor]] || insertion || [[coracoid process]]
 |-
 | [[Coracobrachialis]] || origin   || [[coracoid process]]
 |-
 | [[Serratus anterior muscle|Serratus Anterior]] || insertion  || [[Medial border of scapula|medial border]]
 |-
 | [[triceps|Triceps Brachii]] (long head) || origin  || [[infraglenoid tubercle]]
 |-
 | [[Biceps brachii muscle|Biceps Brachii]] (short head) || origin || [[coracoid process]]
 |-
 | [[Biceps brachii muscle|Biceps Brachii]] (long head) || origin || [[supraglenoid tubercle]]
 |-
 | [[Subscapularis]] || origin || [[subscapular fossa]]
 |-
 | [[Rhomboid major muscle|Rhomboid Major]] || insertion || [[Medial border of scapula|medial border]]
 |-
 | [[Rhomboid minor muscle|Rhomboid Minor]] || insertion  || [[Medial border of scapula|medial border]]
 |-
 | [[Levator scapulae muscle|Levator Scapulae]] || insertion || [[Medial border of scapula|medial border]]
 |-
 | [[Trapezius]] || insertion || [[spine of scapula]]
 |-
 | [[Deltoid muscle|Deltoid]] || origin || [[spine of scapula]]
 |-
 | [[Supraspinatus muscle|Supraspinatus]] || origin  || [[supraspinous fossa]]
 |-
 | [[Infraspinatus]] || origin  || [[infraspinous fossa]]
 |-
 | [[Teres minor|Teres Minor]] || origin  || [[lateral border]]
 |-
 | [[Teres major|Teres Major]] || origin  || [[lateral border]]
 |-
 | [[Latissimus dorsi|Latissimus Dorsi]] (a few fibers, attachment may be absent) || origin   || [[inferior angle]]
 |-
 | [[Omohyoid]] || origin  || [[Superior border of scapula|superior border]]
|}

=== Movements ===

Movements of the scapula are brought about by the scapular muscles. The scapula can perform six actions:
* Elevation: upper [[trapezius]] and [[levator scapulae]]
* Depression: lower trapezius
* Retraction ([[adduction]]): [[Rhomboid muscles|rhomboids]] and middle trapezius
* Protraction (abduction): [[serratus anterior]]
* Upward rotation: upper and lower trapezius, serratus anterior
* Downward rotation: rhomboids,<ref>{{Cite journal|last1=Paine|first1=Russ|last2=Voight|first2=Michael L.|title=The role of the scapula|date=2016-11-22|journal=International Journal of Sports Physical Therapy|volume=8|issue=5|pages=617–629|issn=2159-2896|pmc=3811730|pmid=24175141}}</ref><ref>{{Cite book|title=Anatomy & Physiology|last=Saladin|first=K|publisher=McGraw-Hill|year=2010}}</ref> Levator Scapulae, and Pec Minor

== Clinical significance ==

===Scapular fractures===
[[File:Winging scapula.jpg|thumbnail|A [[winged scapula]] (left)]]
[[File:Scapula ant - anatomical neck and surgical neck.png|thumb|left|140px|Left scapula, anterior surface. Anatomic neck: red, Surgical neck: purple]]
Because of its sturdy structure and protected location, [[Scapular fracture|fractures of the scapula]] are uncommon. When they do occur, they are an indication that severe [[chest trauma]] has occurred.<ref name="Moore03">{{cite book | chapter=Trauma to the chest wall and lung |vauthors=Livingston DH, Hauser CJ | title=Trauma. Fifth Edition |veditors=Moore EE, Feliciano DV, Mattox KL | year=2003 | publisher=McGraw-Hill Professional | isbn=0-07-137069-2 | pages=516 }}</ref>
Scapular fractures involving the neck of the scapula have two patterns. One (rare) type of fracture is through the '''anatomical neck''' of the scapula. The other more common type of fracture is through the '''surgical neck''' of the scapula. The surgical neck exits medial to the [[coracoid process]].<ref>{{cite journal | last1 = van Noort | first1 = A | last2 = van Kampen | first2 = A | date = Dec 2005 | title = Fractures of the scapula surgical neck: outcome after conservative treatment in 13 cases | url = http://igitur-archive.library.uu.nl/dissertations/2005-1130-200011/c3.pdf | journal = Arch Orthop Trauma Surg | volume = 125 | issue = 10 | pages = 696–700 | doi = 10.1007/s00402-005-0044-y | pmid = 16189689 | s2cid = 11217081 | url-status = dead | archive-url = https://web.archive.org/web/20090919155155/http://igitur-archive.library.uu.nl/dissertations/2005-1130-200011/c3.pdf | archive-date = 2009-09-19 }}</ref>

An abnormally protruding inferior angle of the scapula is known as a [[winged scapula]] and can be caused by [[paralysis]] of the [[serratus anterior muscle]]. In this condition the sides of the scapula nearest the spine are positioned outward and backward. The appearance of the upper back is said to be wing-like. In addition, any condition causing weakness of the serratus anterior muscle may cause scapular "winging".

=== Scapular dyskenesis ===
{{see also|Impingement syndrome}}
The scapula plays an important role in shoulder impingement syndrome.<ref name="Kibler, BW. 1998">Kibler, BW. (1998). The role of the scapula in athletic shoulder function. The American Journal of Sports Medicine, 26(2), 325-337.</ref>

Abnormal scapular function is called scapular dyskinesis. The scapula performs elevation of the acromion process during a throwing or serving motion, in order to avoid impingement of the rotator cuff tendons.<ref name="Kibler, BW. 1998" /> If the scapula fails to properly elevate the acromion, impingement may occur during the cocking and acceleration phase of an overhead activity. The two muscles most commonly inhibited during this first part of an overhead motion are the serratus anterior and the lower trapezius.<ref>Cools, A., Dewitte, V., Lanszweert, F., Notebaert, D., Roets, A., et al. (2007). Rehabilitation of scapular muscle balance. The American Journal of Sports Medicine, 35(10), 1744.</ref> These two muscles act as a force couple within the glenohumeral joint to properly elevate the acromion process, and if a muscle imbalance exists, shoulder impingement may develop.

Other conditions associated with scapular dyskenesis include [[thoracic outlet syndrome]] and the related [[pectoralis minor syndrome]].<ref>{{cite journal |last1=Watson |first1=L.A. |last2=Pizzari |first2=T. |last3=Balster |first3=S. |title=Thoracic outlet syndrome Part 2: Conservative management of thoracic outlet |journal=Manual Therapy |date=2010 |volume=15 |issue=4 |pages=305–314 |doi=10.1016/j.math.2010.03.002}}</ref><ref>{{cite journal |last1=Ahmed |first1=Adil S. |last2=Graf |first2=Alexander R. |last3=Karzon |first3=Anthony L. |last4=Graulich |first4=Bethany L. |last5=Egger |first5=Anthony C. |last6=Taub |first6=Sarah M. |last7=Gottschalk |first7=Michael B. |last8=Bowers |first8=Robert L. |last9=Wagner |first9=Eric R. |title=Pectoralis Minor Syndrome – Review of Pathoanatomy, Diagnosis, and Management of the Primary Cause of Neurogenic Thoracic Outlet Syndrome |journal=JSES Reviews, Reports, and Techniques |date=2022 |pages=S2666639122000694 |doi=10.1016/j.xrrt.2022.05.008|doi-access=free |pmc=10426640 }}</ref>

== Etymology ==
The name ''scapula'' as synonym of ''shoulder blade'' is of Latin origin.<ref name="Dorland2000">Anderson, D.M. (2000). ''Dorland’s illustrated medical dictionary'' (29th edition). Philadelphia/London/Toronto/Montreal/Sydney/Tokyo: W.B. Saunders Company.</ref> It is commonly used in medical English<ref name="Dorland2000" /><ref name="Dorland1948">Dorland, W.A.N. & Miller, E.C.L. (1948). ‘’The American illustrated medical dictionary.’’ (21st edition). Philadelphia/London: W.B. Saunders Company.</ref><ref name="Dirckx1997">Dirckx, J.H. (Ed.) (1997).''Stedman’s concise medical dictionary for the health professions.'' (3rd edition). Baltimore: Williams & Wilkins.</ref> and is part of the current official Latin nomenclature, ''[[Terminologia Anatomica]]''.<ref name="FCAT">Federative Committee on Anatomical Terminology (FCAT) (1998). ''Terminologia Anatomica''. Stuttgart: Thieme</ref> Shoulder blade is the colloquial name for this bone.{{citation needed|date=August 2022}}

== In other animals ==
[[File:Eptesicus fuscus scapulae ribs.jpg|thumb|Scapulae, spine and ribs of ''[[Eptesicus fuscus]]'' (Big Brown Bat).]]
In fish, the '''scapular blade''' is a structure attached to the upper surface of the articulation of the [[pectoral fin]], and is accompanied by a similar '''coracoid plate''' on the lower surface. Although sturdy in [[Chondrichthyes|cartilagenous fish]], both plates are generally small in most other fish, and may be partially cartilagenous, or consist of multiple bony elements.<ref name=VB>{{cite book |author=Romer, Alfred Sherwood|author2=Parsons, Thomas S.|year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, PA|pages= 186–187|isbn= 0-03-910284-X}}</ref>

In the early [[tetrapod]]s, these two structures respectively became the scapula and a bone referred to as the '''procoracoid''' (commonly called simply the "[[coracoid]]", but not [[homology (biology)|homologous]] with the mammalian structure of that name). In amphibians and reptiles (birds included), these two bones are distinct, but together form a single structure bearing many of the muscle attachments for the forelimb. In such animals, the scapula is usually a relatively simple plate, lacking the projections and spine that it possesses in mammals. However, the detailed structure of these bones varies considerably in living groups. For example, in frogs, the procoracoid bones may be braced together at the animal's underside to absorb the shock of landing, while in turtles, the combined structure forms a Y-shape in order to allow the scapula to retain a connection to the clavicle (which is part of the shell). In birds, the procoracoids help to brace the wing against the top of the [[sternum]].<ref name=VB />

In the fossil [[therapsid]]s, a third bone, the true '''coracoid''', formed just behind the procoracoid. The resulting three-boned structure is still seen in modern [[monotreme]]s, but in all other living mammals, the procoracoid has disappeared, and the coracoid bone has fused with the scapula, to become the coracoid process. These changes are associated with the upright gait of mammals, compared with the more sprawling limb arrangement of reptiles and amphibians; the muscles formerly attached to the procoracoid are no longer required. The altered musculature is also responsible for the alteration in the shape of the rest of the scapula; the forward margin of the original bone became the spine and acromion, from which the main shelf of the shoulder blade arises as a new structure.<ref name=VB />

=== In dinosaurs ===

In [[dinosaur]]s the main bones of the [[Pectoral girdle#In dinosaurs|pectoral girdle]] were the scapula (shoulder blade) and the [[coracoid]], both of which directly articulated with the [[Clavicle#In dinosaurs|clavicle]]. The clavicle was present in [[saurischian]] dinosaurs but largely absent in [[ornithischian]] dinosaurs. The place on the scapula where it articulated with the [[humerus]] (upper bone of the forelimb) is called the [[Glenoid#In dinosaurs|glenoid]]. The scapula serves as the attachment site for a dinosaur's back and forelimb muscles.{{citation needed|date=March 2021}}

== Gallery ==
{{Gallery|width=150|height=150|File:Human scapula 1.stl|3D image
 |File:Scapula - animation.gif|Position of scapula (shown in red). Animation.
 |File:Left scapula - close-up - animation.gif|Shape of scapula (left). Animation.
 |File:Gray204b.png|Thorax seen from behind.
 |File:Shoulder joint.svg|Diagram of the human shoulder joint, front view
 |File:Shoulder joint back-en.svg|Diagram of the human shoulder joint, back view
 |File:Gray521.png|The scapular and circumflex arteries.
 |File:Gray203.png|Left scapula. Dorsal surface. (Superior border labeled at center top.)
 |File:Slide2DEN.JPG|Scapula. Medial view.
 |File:Slide4DEN.JPG|Scapula. Anterior face.
 |File:Slide6DEN.JPG|Scapula. Posterior face.
 |File:3d Scapula Rendered.gif|Computer Generated turn around Image of scapula
 |File:Suprascapular Canal Course Al-Redouan.png|Suprascapular canal path
 |File:Scapula Anatomy by Jason Christian.webm|Scapula Anatomy
}}

== See also ==
{{Anatomy-terms}}
* [[Scapulimancy]]/[[Oracle bone]] the light side

== References ==
* {{Gray's}}
{{Reflist}}
* Nickel, Schummer, & Seiferle; ''Lehrbuch der Anatomie der Haussäugetiere''.

== External links ==
{{Commons category}}

* {{SUNYAnatomyLabs|10|st|03|01}} - "Joints of the Upper Extremity: Scapula"
*  [http://www.dartmouth.edu/~anatomy/shoulder/bones/bones2.html shoulder/bones/bones2] at the [[Dartmouth Medical School]]'s Department of Anatomy
*  [http://www.dartmouth.edu/~anatomy/shoulder/surface/surface2.html shoulder/surface/surface2] at the [[Dartmouth Medical School]]'s Department of Anatomy
* {{NormanAnatomy|radiographsul}} ({{NormanAnatomyFig|xrayleftshoulder}})

{{Bones of upper extremity}}
{{Portal bar|Anatomy}}
{{Authority control}}

[[Category:Scapula| ]]
[[Category:Bones of the upper limb]]
[[Category:Flat bones]]
[[Category:Shoulder]]