Session 7: Osteology of the Scapula, Clavicle and Proximal Humerus Flashcards
What type of bone is the scapula?
Irregular bone
What does the scapula articulate with?
Humerus at the glenohumeral joint
Clavicle at the acromioclavicular joint
What is the subscapular fossa?
A large concave depression on the anterior surface of the scapula.
What muscle originates from the subscapular fossa?
Subscapularis
What is the coracoid process?
Which muscles originate and insert here?
A hook-like projection which can be found at the superolateral surface of the scapula.
Origination: short head of the biceps brachii
Insertion: pectoralis minor, coracobrachialis
Describe the glenoid fossa.
What does it articulate with?
Shallow cavity, superior on the lateral border.
Articulates with the head of the humerus to form the glenohumeral joint.
Describe the supraglenoid tubercle.
What muscle originates from here?
Roughening which is superior to the glenoid fossa.
Long head of biceps brachii originate here.
Describe the infraglenoid tubercle.
What muscle originates here?
Roughening which is inferior to the glenoid fossa.
Long head of the triceps brachii originate here.
There are some important bony landmarks of the scapula. Describe the spine of the scapula.
The most prominent feature of the posterior scapula which runs transversely across the scapula.
Describe the acromion.
What does it articulate with?
A 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.
Describe the infraspinous fossa.
What muscle originates here?
A depression found below the spine of the scapula.
Origination of infraspinatus.
Describe the supraspinous fossa.
What muscle originates here?
A depression located above the spine of the scapula.
Smaller than the infraspinous fossa and more convex as well.
Origination of supraspinatus.
What are the joints of the scapula?
Glenohumeral joint between the glenoid fossa and the head of the humerus.
Acromioclavicular joint between the acromion and the clavicle.
What is the scapulathoracic joint.
An articulation between the anterior surface of the scapula and the rib cage which cannot be classified as a joint.
It is an articulation of the scapula with thorax that depends on the integrity of the acromioclaviuclar and sternoclavicular joint.
Clavicle.
Type and three main functions.
Long bone.
Attaches the upper limb to the trunk.
Protects the underlying neuromuscular structures supply the upper limb.
Transmits force from the upper limb to the axial skeleton.
Structure of the clavicle.
A long bone with a slight ‘S’ shape.
The medial aspect is convex anteriorly and the lateral aspect is concave anteriorly.
The medial end is called the sternal end and the lateral end is the acromial end.
Between the ends is the shaft.
Insertion and origins of muscle on the clavicle.
Insertion of:
Trapezius (anterior surface of the acromial end)
Subclavius muscle (in middle of the shaft at the superior surface)
Origination of: Deltoid muscle (posterior surface of the acromial end) Pectoralis major (posterior surface of the middle to sternal end) Sternocleidomastoid muscle at the superior surface of the sternal end) Sternohyoid muscle (posterior surface oft the sternal end).
What does the acromial end of the clavicle articulate with?
The acromion of the scapula at the acromioclavicular joint.
What does the sternal end of the clavicle articulate with?
The sternum at the sternoclavicular joint.
What two ligaments attach at the acromial end of the clavicle?
The conoid ligament which attach at the conoid tubercle of the clavicle and the coracoid process.
The trapezoid ligament which attach at the trapezoid line of the clavicle and the coracoid process.
What are the conoid ligament and the trapezoid ligament collectively known as?
What is its main function?
The coracoclavicular ligament.
To effectively suspend the weight of the upper limb from the clavicle.
What type of joint is the acromioclavicular joint?
A plane-type synovial joint.
Where can the acromioclavicular joint be palpated?
Approx. 2-3 cm medially from the tip of the shoulder.
What are the two atypical features of the acromioclavicular joint?
The articular surfaces of the joint are lined with fibrocartilage instead of hyaline cartilage which is usually found in a synovial joint.
The joint cavity is partially divided by an articular disc. This is a wedge of fibrocartilage that is suspended from the upper part of the capsule.
What is the acromioclavicular joint reinforced by?
A loose fibrous layer which encloses the two articular surfaces.
The posterior aspect of the joint capsule is reinforced by fibres from the trapezius muscle as well.
What are the three main ligaments that strengthen the acromioclavicular joint?
Intrinsic:
Acromioclavicular ligament which runs horizontally from the acromion to the lateral clavicle. Lies superficial to the joint capsule and reinforce the superior aspect.
Extrinsic:
Conoid ligament which runs vertically from the coracoid process of the scapula to the conoid tubercle of the clavicle.
Trapezoid ligament which runs from the coracoid process of the scapula to the trapezoid line of the clavicle.
What movements does the acromioclavicular joint allow?
A small degree of axial rotation and anteroposterior movement.
Where can the sternoclavicular joint be found?
Between the sternal end of the clavicle and the manubrium of the sternum. It is the only attachment of the upper limb to the axial skeleton so its very strong.
What type of joint is the sternoclavicular joint?
A saddle-type synovial joint.
What atypical feature does the sternoclavicular joint have?
The articular surfaces are covered with fibrocartilage.
The sternoclavicular joint is separated into two compartments by a fibrocartilaginous articular disc. Why is this important?
It allows the clavicle and the manubrium to slide over each other more freely to allow rotation and movement in a third axis.
There are several movements of the shoulder that also require movement at the sternoclavicular joint.
Which?
Elevation of shoulder when shrugging or when abducting the arm over 90 degrees.
Depression of shoulders when drooping the shoulder or when extending the arm at the shoulder behind the body.
Protraction of the shoulders
Retraction of the shoulders
Rotation when the arm is raised over the head by flexion at the glenohumeral joint.
What does the proximal humerus articulate with?
The glenoid fossa of the scapula to form the glenohumeral joint.
What does the distal humerus articulate with?
The head of the radius and trochlear notch of the ulna to form the elbow joint.
What is the structure of the proximal humerus?
It has a head which articulates with the glenoid fossa.
An anatomical neck which separates the head of the humerus from the greater and lesser tubercle of the humerus.
The greater tubercle is posterolateral and the lesser tubercle is more medial.
The surgical neck of the humerus lies between the two tubercles and the shaft of the humerus.
In between the tubercles there is a depression called the intertubercular sulcus. The intertubercular sulcus runs somewhat down the proximal humerus and is defined by two lips; one lateral and one medial.
What muscles insert at the greater tubercle?
Three rotator cuff muscles: supraspinatus, infraspinatus and teres minor. Superior to inferior.
What muscles insert at the lesser tubercle?
The subscapularis.
What muscles insertions can be found by the lips of the intertubercular sulcus and in the intertubercular sulcus itself?
“A lady between two majors”
Pectoralis major inserts lateral lip
Latissimus dorsi inserts into the intertubercular sulcus
Teres major inserts onto the medial lip
Also the tendon of the long head of biceps brachii runs through the intertubercular sulcus.
Why is the surgical neck of the neck clinically important?
Because it is a frequent site of fractures usually from blunt trauma to the shoulder or from falling on an outstretched hand.
Why are fractures of the surgical neck of the humerus a problem?
Because this is where you would find the axillary nerve and the posterior circumflex artery. In the case of a fracture this site can get damaged.
What are the consequences of axillary nerve damage?
Axillary nerve damage would result in paralysis of the deltoid and teres minor muscles.
This means that abduction would be difficult as well as slight impairment of adduction and lateral rotation but mainly abduction.
Also the innervation of skin and therefore sensation would be impaired in the regimental badge area.
Where does the deltoid insert on the humerus?
On the lateral side of the humeral shaft called the deltoid tuberosity. This is a roughened area.
Explain the radial groove.
A shallow depression that runs diagonally on posterior surface of the humerus at the level of the deltoid tuberosity.
In this groove the radial nerve and profound brachii artery can be found.
What muscles attach along the humeral shaft?
Anteriorly: Coracobrachialis, deltoid, brachialis and brachioradialis
Posteriorly: medial and lateral heads of triceps.
What are the extrinsic muscles of the shoulder?
Superficial: Trapezius and latissimus dorsi
Deep: levator scapulae, rhomboid major, rhomboid minor
Location, origination, insertion, innervation and action of trapezius.
Most superficial of all the back muscles.
Originates from the external occipital protuberance of the skull, the nuchal ligament and the spinous processes of C7-T12.
Inserts onto the clavicle, acromion and the spine of the scapula.
Innervated by spinal accessory nerve (Cranial nerve XI) and receives proprioceptor fibres from C3 and C4.
Action:
Upper fibres of the trapezius elevate the scapula and rotate it during abduction of the arm above 90 degrees.
Middle fibres retract the scapula
Lower fibres pull the scapula inferiorly
How can you test the power of the trapezius muscle clinically?
Ask patient to shrug their shoulders while you attempt to push them back down.
Location, origination, insertion, innervation and action of latissimus dorsi.
Covers a wide area on the lower back inferior to the trapezius.
Originates from spinous processes of T6 to T12, the iliac crest and the thoracolumbar fascia and the three inferior ribs.
Fibres converge into a tendon and inserts into the intertubercular sulcus of the humerus.
Innervated by thoracodorsal nerve.
Actions: Latissimus dorsi extends, adducts and medially rotates the upper limb.
What are the deep muscles of the extrinsic muscles?
Levator scapulae, rhomboid major and rhomboid minor.
Location, origination, insertion, innervation and action of levator scapulae.
Small strap-like muscles found deep to trapezius and superior rhomboid minor.
Originates from the transverse processes of the C1-C4 vertebrae.
Inserts on the medial border of the scapula.
Innervated by dorsal scapular nerve.
Action: elevates the scapula.
Location, origination, insertion, innervation and action of rhomboid minor.
Deep to trapezius, inferior to levator scapulae and superior to rhomboid major.
Originates from spinous processes C7-T1.
Inserts onto medial border of the scapula at the level of the spine of the scapula.
Innervated by dorsal scapular nerve same as levator scapulae.
Actions: Retracts the scapula and rotates the medial border such that the glenoid fossa is rotated inferiorly.
Location, origination, insertion, innervation and action of rhomboid major.
Inferior to rhomboid minor and deep to trapezius.
Originates from spinous processes of the T2-T5 vertebrae.
Inserts onto the medial border of the scapula between the scapular spine and the inferior angle of the scapula.
Innervated by the dorsal scapular nerve like the levator scapulae and rhomboid minor.
Actions: Retracts the scapula and rotates the medial border such that the glenoid fossa is rorated inferiorly.
What are the intrinsic muscles of the shoulder?
Deltoid
Teres major
Four rotator cuff muscles:
SITS = Supraspinatus, infraspinatus, teres minor and subscapularis.
Location, origination, insertion, innervation and action of deltoid.
Originates from the anterior border and upper surface of the lateral third of the clavicle and from the acromion and spine of the scapula.
Inserts into the deltoid tuberosity on the lateral surface of the humerus.
Innervated by the axillary nerve (C5,C6 from the posterior cord of the brachial plexus)
Actions:
Anterior fibres flex and medially rotate the arm at the shoulder
Middle fibres abducts the arm from 15-90 degrees.
Posterior fibres extend and laterally rotate the arm at the shoulder.
Location, origination, insertion, innervation and action of teres major.
Forms the inferior border of the quadrangular space.
Originates from the posterior surface of the inferior angle of the scapula. Passes anterior to the long head of triceps.
Inserts onto the medial lip of the intertubercular groove of the humerus.
Innervated by the lower subscapular nerve.
Actions: Adducts the arm at the shoulder and medially rotates the arm
Location, origination, insertion, innervation and action of supraspinatus.
Originates from the supraspinous fossa of scapula.
Inserts onto the greater tubercle of the humerus.
Innervated by suprascapular nerve (C5,C6)
Actions: Abducts the arm from 0-15 degrees. Assists the deltoid in abducting the arm from 15-90 degrees.
Location, origination, insertion, innervation and action of infraspinatus.
Originates from the infraspinous fossa of the scapula.
Inserts onto the greater tubercle of the humerus between the supraspinatus and teres minor.
Innervation by suprascapular nerve (C5, C6)
Action: Laterally rotates the arm.
Location, origination, insertion, innervation and action of teres minor.
Originates from the posterior surface of the scapula adjacent to the lateral border.
Inserts onto the greater tubercle of the humerus inferior to the infraspinatus.
Innervation by the axillary nerve (C5, C6)
Actions: laterally rotates the arm and a weak adductor.
Location, origination, insertion, innervation and action of subscapularis.
Originates from the subscapular fossa on the costal surface of the scapula.
Inserts onto the lesser tubercle of the humerus.
Innervated by the upper and lower subscapular nerves.
Actions: Medially rotates the arm.
Muscles of the anterior compartment of the arm.
BBC:
Biceps brachii
Brachialis
Coracobrachialis
Location, structure, origination, insertion, innervation and action of biceps brachii.
Two headed muscle located anteriorly to the humerus.
Long head originates from the supraglenoid tubercle and passes through the should joint inside the joint capsule.
Short head originates from the coracoid process of the scapula.
The head unite into a belly and inserts onto the radial tuberosity and also into the deep fascia of the forearm via the bicipital aponeurosis.
Innervated by the musculocutaneous nerve (C5-C7)
Actions: Strong supinator of the forearm. Flexes the arm at the elbow and the shoulder joints. Can be remembered as when opening a bottle of win with a corkscrew. Supination to unscrew the work and flexion to pull it out.
What purpose does testing the biceps tendon reflex serve and how is it done?
It tests the spinal cord segment C6 because this myotome is predominantly responsible for elbow flexion and for supination.
It is done by by tapping the tendon of biceps brachii when it is stretched. This activates a neural reflex arc resulting in contraction of the biceps muscle and flexion of the elbow.
What is the bicipital aponeurosis?
A thick fascial band that originates close to the musculotendinous junction of the biceps. This forms the roof of the cubital fossa and ends by blending with the deep fascia of the ulnar border of the anterior forearm.
Location, structure, origination, insertion, innervation and action of coracobrachialis.
Lies deep to the short head of the biceps brachii.
Originates from the coracoid process of the scapula. Passes through the axilla.
Inserts onto the medial side of the humeral shaft at the level of the deltoid tubercle.
Innervated by the musculocutaneous nerve (C5-C7)
Actions: Flexes the arm at the shoulder and is a weak adductor of the arm.
Location, structure, origination, insertion, innervation and action of brachialis.
Lies deep to the belly of biceps brachii in the distal has of the arm. It forms the floor of the cubital fossa.
Originates from the anterior surface of the distal half of the humeral shaft.
Inserts onto the coronoid process of the ulna and the ulnar tuberosity.
Innervated by the musculocutaneous nerve (C5-C7 and contributions from the radial nerve (C5 and C6 fibres))
Actions: Brachialis flexes the forearm at the elbow
What are the muscles in the posterior compartment of the arm?
Only the triceps brachii.
Location, structure, origination, insertion, innervation and action of triceps brachii.
Three origins since the triceps brachii has three heads.
Long head: from the infraglenoid tubercle.
Lateral head: shaft of the humerus superior to the radial groove
Medial head: from the shaft of the humerus, inferior to the radial groove.
The heads converge to form a single tendon that inserts onto the olecranon of the ulna.
Innervated by the radial nerve.
Actions: Extends the forearm.
What purpose does testing the triceps tendon reflex serve?
How is it done?
To test the spinal cord segment C7 because this is the myotome which predominantly is responsible for elbow extension.
Taping the triceps tendon results in a reflex contraction of the triceps muscle and extension at the elbow.
What are the quadrangular space and the triangular space and the triangular interval?
Passageways between the muscles of the shoulder region.
Clinical importance of the quadrangular space.
It is the route via which the axillary nerve and posterior circumflex humeral artery and vein enter the posterior compartment of the arm.
Superior Inferior Medial Lateral Anterior borders of the quadrangular space.
Superior: inferior margin of teres minor Inferior: Superior margin of teres major Medially: long head of triceps brachii Laterally: surgical neck of the humerus Anteriorly: Subscapularis
What passes through the triangular space?
Circumflex scapular vessel to enter the infraspinous fossa. No nerves pass through.
Superior
Inferior
Lateral
borders of the triangular space.
Superior: inferior border of teres minor
Inferior: Superior border teres major
Laterally: long head of triceps brachii
Superior
Inferior
Lateral
borders of the triangular interval
Superior: inferior border of teres major
Medial: long head of triceps brachii
Lateral: Either shaft of the humerus or the lateral head of triceps brachii
Artery of the arm.
Brachial artery.
Route of the brachial artery.
Continuation of the axillary artery past the inferior border of the teres major muscle. The axillary artery becomes the brachial artery at the inferior border of the teres major muscle.
Provides main blood supply to the arm and fore arm.
Distal to teres major the brachial artery gives rise to the profunda brachii (deep brachial artery).
Brachial artery continues to descend the anterior compartment of the arm.
When it passes through the cubital fossa underneath the brachialis muscle the brachial artery will bifurcate into the radial and ulnar arteries.
Route of profunda brachii.
A branch of brachial artery distal to teres major. It travels with the radial nerve in the radial groove of the humerus and supplies the structures in the posterior compartment of the arm (like triceps brachii).
Where can the brachial pulse be palpated?
In the cubital fossa, medial to the tendon of biceps brachii. In the proximal arm the median nerve lies immediately lateral to the brachial artery.
Distally the median nerve crosses the medial side of the brachial artery.
