Humerus Flashcards
What is the humerus?
The bone that forms the upper arm
What does the humerus do?
Joints the arm to the shoulder and forearm
What does the humerus articulate with?
The proximal region articulates with the scapula and clavicle
The distal region articulates with the forearm bones (radius and ulna)
What is formed when the humerus articulates with the scapula and clavicle?
The shoulder joint
What is formed when the humerus articulates with the forearm bones?
Elbow joint
What does the humerus act as?
The attachment site for many muscles and ligaments
What does the humerus’ role as an attachment site result in?
Various raised roughening on the bony surface
What does the proximal region of the humerus articulate with?
The scapula
What is formed when the humerus articulates with the scapula?
The glenohumeral (shoulder) joint
What are the important anatomical features of the proximal humerus?
The head Anatomical neck Surgical neck Greater and lesser tubercles Intertubercular sulcus
What is a tubercle?
A round nodule
What does a tubercle signify?
An attachment site of a muscle or ligament
Where does the head of the humerus project?
Medially and superiorly
What does the head of the humerus do?
Articulates with the glenoid cavity of the scapula
How is the head of the humerus connected to the tubercles?
By the anatomical neck
Describe the anatomical neck of the humerus?
Short in width, nondescript
Where is the greater tubercle of the humerus located?
Laterally
What does the greater tubercle of the humerus have?
An anterior and posterior face
What is the function of the greater tubercle?
It serves as attachment sites for three of the rotator cuff muscles
What muscles is the greater tubercle the attachment site for?
Supraspinatus
Infraspinatus
Teres minor
How does the lesser tubercle differ from the greater?
It is much smaller, and more medially located. It only has an anterior face
What is the purpose of the lesser tubercle?
It is the site of attachment for the last rotator cuff muscle- the subscapularis
What separates the two tubercles of the humerus?
A deep depression, called the intertubercular sulcus (or groove)
What runs through the intertubercular sulcus?
The tendon of the long head of the biceps brachii
What are the edges of the intertubercular sulcus known as?
Lips
What attaches to the lips of the intertubercular sulcus?
Tendons of the pectoralis major, teres major and latissimus dorsi
Where does the surgical neck of the humerus run?
From the tubercles to the shaft of the humerus
What is a frequent site of fracture of the proximal part of the humerus?
The surgical neck
How does a fracture of the surgical neck of the humerus occur?
By a direct blow to the area, or by falling on an outstretched hand
What are the key structures of concern in a surgical neck of the humerus fracture?
Axillary nerve
Posterior circumflex artery
Where does the axillary nerve innervate?
The skin over the lower deltoid (known as the regimental badge area)
What will damage to the axillary nerve result in?
Paralysis to the deltoid and teres minor muscles, and so the patient will be unable to abduct their arm
Sensory innervation to the regimental badge area could be lost
What important landmarks does the shaft of the humerus contain?
The deltoid tuberosity
The radial groove
What is the shaft of the humerus the site for?
Attachment for various muscles
What is found on the lateral side of the humeral shaft?
The deltoid tuberosity
What is the deltoid tuberosity?
A roughened surface where the deltoid muscle attaches
What is the radial groove?
A shallow depression
Where does the radial groove run?
Diagonally down the surface of the humerus, parallel to the deltoid tuberosity
What lies in the radial groove?
The radial nerve and the profunda brachii artery
What muscles attach anteriorly to the humerus?
Coracobrachialis
Deltoid
Brachialis
Brachioradialis
What muscles attach posteriorly to the humerus?
Medial and lateral heads of the triceps
What is the problem with a mid shaft fracture of the humerus ?
It could easily damage the radial nerve and profunda brachii artery
Why could a mid shaft fracture of the humerus easily damage the radial nerve and profunda brachii artery?
As they are tightly bound in the radial groove
What does the radial nerve innervate?
Extensors of the wrist
What would be the result of a damaged radial nerve?
The extensors of the wrist would be paralysed, resulting in unopposed flexion of the wrist, known as ‘wrist drop’
There is also some sensory loss over the dorsal (posterior) surface of the hand, and proximal ends of the lateral 3 and a half fingers dorsally
What does the dorsal region of the humerus articulate with?
The ulna and radius
What is formed when the dorsal region of the humerus articulates with the radius and ulna?
The elbow joint
What shape does the bone adopt in the dorsal region?
A flattened, almost 2D shape
What do the lateral and medial borders of the humerus form?
Medial and lateral supraepicondylar ridges
How does the lateral supraepicondylar ridge differ from the medial?
It is more roughened
Why is the lateral supraepicondylar ridge more roughened than the medial?
Because it is the site of attachment for many of the extensor muscles in the posterior forearm
What is found immediately distal to the supraepicondylar ridges?
The lateral and medial epicondyles
What are epicondyles?
Projections of the bone
Where can the epicondyles be palpated?
At the elbow- the medial more so because it is much larger
Where can the ulnar nerve be palpated?
Along the posterior side of the medial epicondyle
Why can the ulnar nerve be palpated at the medial epicondyle?
Because this is where it passes into the forearm
What articulates with the ulna?
The trochlea
Where is the trochlea located?
Medially
Where does the trochlea extend to?
The posterior of the bone
What is found lateral to the trochlea?
The capitulum
What does the capitulum article with?
The radius
What is found along the distal portion of the humerus?
Three depressions, known as the coronoid, radial and olecrannon fossae
What do the coronoid, radial and olecrannon fossae accommodate?
The forearm bones during movement at the elbow
Where are the common fracture sites of the distal humerus?
Supracondylar fractures
Medial epicondyle fractures
How does a supraepicondylar fracture occur?
By falling on a flexed elbow
What kind of fracture is a supraepicondylar?
A transverse fracture, spanning between the two epicondyles
What can distal humerus fractures lead to?
Interference to the blood supply of the forearm from the brachial artery
Damage to the medial, ulnar or radial nerve
How can a distal humerus fracture lead to interference of the blood supply from the brachial artery?
Direct damage, or swelling
What can interference in forearm blood supply lead to?
Ischaemia, which can cause Volkmann’s ischaemic contracture
What is Volkmann’s ischaemic contracture?
Uncontrolled flexion of the hand
Why does Volkmann’s ischaemic contracture occur?
Because the flexor muscles become fibrotic and short
What could a medial epicondyle fracture damage?
The ulnar nerve
What results from damage to the ulnar nerve?
A deformity known as the ulnar claw
Loss of sensation over the medial 1 and a 1/2 fingers of the hand, on both the dorsal and palmar surfaces
