Scapula Fractures overview.

Summary

Scapula Fractures are uncommon fractures to the shoulder girdle caused by high energy trauma and associated with pulmonary injury, head injury, and increased injury severity scores. 

Diagnosis can be made with plain radiographs and CT studies are helpful for fracture characterization and surgical planning.

Treatment is usually nonoperative with a sling. Surgical management is indicated for intra-articular fractures, displaced scapular body/neck fractures, open fractures, and those associated with glenohumeral instability. 

Epidemiology

Incidence

rare

<1% of all fractures

3-5% of shoulder girdle fractures

Demographics

age

commonly between 25-50

males > females

Location  

scapular body/spine = 45-50%

glenoid = 35%

glenoid neck = 25%

glenoid fossa/rim = 10%

often associated with impaction of humeral head into glenoid 

acromion = 8%

coracoid = 7%

Etiology

Pathophysiology

mechanism of injury

high-energy trauma (80-90%)

motor vehicle collisions

account for >70% of scapula fractures

indirect trauma through fall on outstretched hand

glenohumeral dislocation

anterior dislocation leads to anterior rim fracture

posterior dislocation leads to posterior rim fracture

seizure

electric shock

Associated injuries (in 80-95%)    

medical

orthopedic 

Anatomy

Osteology

scapular body

origin or insertion of 18 muscles   

function to connect scapula to thorax, spine and upper extremity

large triangle shape with 4 major processes  

scapular spine

osseous bridge separating supraspinatus and infraspinatus

spinoglenoid notch represents possible site of compression for suprascapular nerve

glenoid

represents articulating process on lateral scapula serving as socket for glenohumeral joint

pear-shaped and wider inferiorly from anterior to posterior

average 1-5º of retroversion and 15º superior tilt from scapular plane

fibrocartilaginous labrum deepens glenoid fossa by 50% to increase stability

acromion

articulates with clavicle to form acromioclavicular joint

formed by 3 ossification centers  

pre acromion - tip

meso acromion - mid

meta acromion - base

coracoid process  

has two secondary ossification centers that are open until around age 25 and should not be interpreted as fracture

angle of coracoid

tip of coracoid

muscular attachments

conjoint tendon

coracobrachialis

short head biceps

pectoralis minor

ligament attachments

coracoclavicular (CC) ligaments

most anterior CC ligament attachment is 25mm from tip of coracoid

coracoacromial ligament

 

Arthrology

glenohumeral joint

glenoid & labrum support humeral head to produce high degree of motion

stability provided by static and dynamic stabilizers

scapulothoracic joint

not a true joint but does represent an articulation between scapula and thorax

involved primarily in elevation and depression of shoulder as well as rotation and pro-/retraction

acromioclavicular (AC) joint

articulation of acromion and distal clavicle

supported by acromioclavicular ligaments (horizontal stability) and coracoclavicular ligaments (vertical stability)

8º of rotation occurs through acromioclavicular joint

superior shoulder suspensory complex  

bone & soft tissue ring which provides connection of glenoid/scapula to axial skeleton

composed of 4 bony landmarks

distal clavicle

acromion

coracoid

glenoid

also composed of ligamentous complexes of acromioclavicular and coracoclavicular joints

Blood supply

contributions from anterior and posterior circumflex, scapular circumflex and suprascapular arteries

watershed area present in anterosuperior glenoid

Nervous system

scapula is intimately associated with brachial plexus

axillary nerve is at risk inferior to the glenoid as it runs from anterior to posterior

compression of suprascapular nerve at scapular notch leads to supraspinatus/infraspinatus weakness, with compression at the spinoglenoid notch leading only to infraspinatus weakness

Biomechanics

scapula contributes to glenohumeral rotation and abduction

 1/3 of shoulder motion is scapulothoracic, 2/3 is glenohumeral

Classification