25. Osteology of the scapula, clavicle and proximal humerus Flashcards
what type of bone is the scapula?
Irregular bone
What does the scapula articulate with?
- It articulates with the humerus at the glenohumeral joint
* with the clavicle at the acromioclavicular joint. In doing so, the scapula connects the upper limb to the trunk
describe the shape of the scapula
a triangular, flat bone, which serves as a site for attachment for seventeen different muscles
What is the anterior surface of the scapula referred to as? What is the fossa of this surface called and which muscle originates from this fossa?
- Anterior surface is called the costal surface which faces the rib cage.
- Has a subscapular fossa(large concave depression over most of its surface), from which the subscapularis (rotator cuff muscle) originates
Where is the coracoid process located on the scapula and in which direction does it project? Where does it lie relative to the clavicle?
Arises from the superolateral surface of the scapula and projects anterolaterally
- a hook-like projection, which lies directly below the clavicle
Which muscle attach to the coracoid process?
- Pectoralis minor inserts onto it
- short head of biceps brachii and coracobrachialis originate from it
What are 3 important landmarks of the lateral surface of the scapula?
Glenoid fossa (glenoid cavity)
Supraglenoid tubercle
Infraglenoid tubercle
What is the glenoid fossa and where is it located?
A shallow cavity, located superiorly on the lateral border. This articulates with the head of the humerus to form the glenohumeral (shoulder) joint.
What is the Supraglenoid tubercle and what attaches to it?
A roughening immediately superior to the glenoid fossa. This is the site of origin of the long head of the biceps brachii muscle.
What is the infraglenoid tubercle and what attaches to it?
A roughening immediately inferior to the glenoid fossa. This is the site of origin of the long head of the triceps brachii muscle.
what is the lateral surface of the scapula the site of?
The lateral surface of the scapula is the site of the glenohumeral joint, and of various muscle attachments
What are 4 important landmarks of the posterior surface of the scapula?
- Spine
- Acromion
- Infraspinous fossa
- Supraspinous fossa
What is the acromion and what does it articulate with?
Large projection arising from the lateral end of the scapula spine.
The acromion arches laterally over the glenohumeral joint and articulates with the clavicle at the acromioclavicular joint
What is the infraspinous fossa and what originates from here?
A depression below the spine of the scapula. The infraspinatus muscle originates from this area.
What is the supraspinous fossa and what originates from here?
A depression above the spine of the scapula. The supraspinous fossa is much smaller than the infraspinous fossa and is more convex in shape. The supraspinatus muscle originates from this area
What is the the posterior surface of the scapula the site of?
The posterior surface of the scapula is the site of origin for the majority of the rotator cuff muscles of the shoulder
What is the scapula spine?
the most prominent feature of the posterior scapula. It runs
transversely across the scapula.
Where is the Glenohumeral joint and the Acromioclavicular joint?
Glenohumeral joint: between the glenoid fossa (glenoid cavity) of the
scapula and the head of the humerus.
Acromioclavicular joint: between the acromion of the scapula and the clavicle
What is the scpulothoracic joint and why is it not a true joint?
Between the anterior surface of the scapula and the rib cage.
This is not a true joint as it has none of the characteristics of a joint (i.e. union by fibrous, cartilaginous or synovial tissue). Instead, it is an articulation of the scapula with the thorax that itself depends on the integrity of the acromioclavicular and sternoclavicular joints
Why does a fractured scapula usually not require fixation?
Tone of the surrounding muscles holds the fragments in place whilst healing occurs
What can cause fractures of the scapula?
Fractures of the scapula are relatively uncommon, and if they do occur, they are an indication of severe chest trauma. They are frequently seen in high speed road collisions, crushing injuries, or high-impact sports injuries.
What are the articulation of the clavicle on either side?
Laterally: acromion
Medially: manubrium (of the sternum)
What are the 3 main functions of the clavicle?
- Attaches the upper limb to the trunk as part of the ‘shoulder girdle’.
- Protects the underlying neurovascular structures supplying the upper limb.
- Transmits force from the upper limb to the axial skeleton.
What is the clavicle classified as?
classified as a long bone and has a slight ‘S’ shape
Describe the structure of the clavicle
The medial aspect is convex anteriorly, and the lateral aspect concave. The medial end is referred to as the sternal end and the lateral end as the acromial end; between the two ends is the shaft
What does the sternal end of the clavicle contain?
contains a large facet for articulation with the manubrium of the sternum at the sternoclavicular joint
What is the inferior surface of the sternal end of the clavicle marked by?
Marked by a rough oval depression for the costoclavicular ligament (a ligament of the sternoclavicular joint)
Which muscles attach to the shaft of the clavicle?
The shaft of the clavicle acts a point of origin and insertion for several muscles: deltoid, trapezius, subclavius, pectoralis major, sternocleidomastoid sternohyoid