Ulna Flashcards
What is the ulna?
A long bone in the forearm
Where does the ulna lie?
Medially and parallel to the radius, and second of the forearm bones
What does the ulna act as?
The stabilising bone, with radius pivoting it to produce movement
What does the ulna articulate with?
Proximally, the humerus
Distally, the radius
What is formed when the ulna articulates with the humerus?
The elbow joint
What is formed when the ulna articulates with the radius?
The distal radio-ulnar joint
What does the proximal portion of the ulna articulate with?
The trochlea of the humerus
What enables movement at the elbow joint?
The specialised structure of the ulna, with bony prominences for muscle attachment
What are the important landmarks of the proximal ulna?
The olecranon Coronoid process Trochlear notch Radial notch Tuberosity of ulna
What is the olecranon?
A large projection of bone
Where does the olecranon extend?
Proximally
What does the olecranon form?
Part of the trochlear notch
Where can the olecranon be palpated?
As the ‘tip’ of the elbow
What attaches to the olecranon?
The triceps brachii, at its superior surface
What is the coronoid process?
A ridge of bone that projects outwards in an anterior manner
What does the coronoid process form?
Part of the trochlear notch
What is the trochlear notch formed by?
Olecranon
Coronoid process
What shape is the trochlear notch?
Wrench shaped
What does the trochlear notch do?
Articulates with the trochlea of the humerus
Where is the radial notch located?
On the lateral surface of the trochlear notch
What does the radial notch do?
Articulates with the head of the radius
What is the tuberosity of the ulna?
A roughening immediately distal of the coronoid process
What is the purpose of the tuberosity of the ulna?
It is where the brachialis muscle attaches
What shape is the ulnar shaft?
Triangular
What does the ulnar shaft have?
Three borders and three surfaces
What happens as the ulnar shaft moves distally?
It decreases in width
What are the three surfaces of the ulnar shaft?
Anterior
Posterior
Medial
What is the importance of the anterior surface of the ulnar shaft?
It is the site of attachment for the pronator quadratus muscle distally
What is the importance of the posterior surface of the ulnar surface?
It is the site of attachment for many muscles
What are the three borders of the ulnar shaft?
Posterior
Interosseous
Anterior
Where is the posterior border of the ulnar shaft palpable?
Along the entire length of the forearm posteriorly
What is the importance of the interosseous border of the ulnar shaft?
It is the site of attachment for the interosseous membrane
What does the interosseous membrane do?
Spans the distance between the two forearm bones
How does the distal portion of the ulna differ from the proximal end?
It is much smaller in diameter
How does the distal portion of the ulna terminate?
In a rounded head, with a distal projection
What is the distal projection on the rounded head of the ulnar called?
The ulnar styloid process
What does the ulnar head articulate with?
The ulnar notch of the radius
What is formed when the ulnar head articulates with the ulnar notch?
The distal radio-ulnar joint
How does a fracture of the ulnar alone usually occur?
As a result of the ulna being hit by an object
Where is the most likely site of ulnar fracture?
The shaft
What happens in a shaft fracture of the ulna?
The normal muscle tone will pull the proximal ulna posteriorly
What can less commonly be fractured in the ulna?
The olecranon process
What causes olecranon process fractures?
The patient falling on a flexed elbow
What happens when the olecranon process fractures?
The triceps brachii can displace part of the fragment proximally
How are the ulna and radius attached?
Interosseous membrane
What is the result of the interosseous membrane regarding fractures?
The force of trauma to one bone can be transmitted to the other via the membrane, and therefore fracture of both the forearm bones are not uncommon
What are the two classical fractures of both forearm bones?
Monteggia’s fracture
Galeazzi’s fracture
What causes Monteggia’s Fracture?
Force from behind the ulna
What happens in Monteggia’s Fracture?
The proximal shaft of the ulna is fractured, and the head of the radius dislocates anteriorly at the elbow
What is Galaezzi’s fracture?
A fracture to the distal radius, with the ulna head dislocating at the distal radio-ulnar joint
