Lecture 3: Elbow Flashcards
What 2 articulations make up the elbow joint (briefly describe them)?
1) Humero-ulnar - between the trochlea of the humerus and trochlear notch of the ulnar
2) Humero-radial - between capitulum and upper surface of radial head
The capsule of the elbow joint reinforces the elbow joint in which 2 directions, using what tendons?
Reinforced laterally by the radial collateral ligament
Reinforced medially by the ulnar collateral ligament
The capsule is thin and loose posteriorly and anteriorly
Why is the instability of the elbow joint capsule anteriorly and posteriorly necessary?
To allow for flexion and extension ie. the movements of the elbow joint
Why is the elbow joint one of the most stable joints in the body?
Congruity between the trochlear notch of the ulnar and trochlea of the humerus
The radius has a flat articulation point with the humerus so does not contribute to stability
Posterior dislocation accounts for what percentage of elbow dislocations and when this occurs in what direction do the bones involved project?
Accounts for 80-90%
Distal end of the humerus is driven anteriorly through the weak anterior part of the joint capsule and the ulnar and radius project posteriorly
Sports injuries account for what percentage of elbow dislocations and in which people is it most common?
50%
Most common in adolescents and young people
What are the 2 main causes of posterior dislocation of the elbow?
1) Fall onto hands with elbows flexed
2) Fall onto hand with elbow hyperextended - all weight goes through ulnar and drives it posteriorly or posterolaterally
What are the 3 findings associated with a posterior dislocation of the elbow joint?
1) Ulnar collateral ligament torn
2) Fractures to the head of the radius, coronoid process, olecranon process
3) Ulnar nerve injury
What are the 3 symptoms of a posterior dislocation of the elbow joint?
1) Severe pain in the elbow - ligaments torn - possible fracture
2) Elbow appears to have become wider
3) Prominent olecranon process - as ulnar pushed posteriorly
What is the olecranon process?
The outside of the ulnar notch - bony bit of the elbow
The ulnar nerve is a branch of what?
The brachial plexus
Where does the ulnar nerve pass in the elbow joint?
Between the olecranon process of the ulnar and medial epicondyle of the distal end of the humerus
What muscle in the wrist is supplied by the ulnar nerve, what is its action?
Flexor carpi ulnaris - involved in flexion of the wrist
What is the sensory supply of the ulnar nerve?
Sensory supply to medial part of the palm and medial 1 and 1/2 fingers
What are the symptoms of a damaged ulnar nerve?
1) Numbness of medial part of palm and 1 and a half fingers
2) Weakness of flexion and adduction of the wrist
What is the difference between a simple and a complex elbow dislocation and what are the prognoses?
1) Simple elbow dislocation
- No fracture of the bones around the joint, normally ligamentous injury
- Good prognosis as often surgery is not required for treatment
2) Complex elbow dislocation
- Associated with fracture, usually of the forearm
- Surgery is often needed to fix the broken arm in order to maintain the elbow joint in a normal postition
What limits extension normally so that hyperextension at the elbow joint isnt possible - why in some individuals is hyperextension possible?
When extended the olecranon process makes contact with the humerus
There is a fossa in the humerus called the olecranon fossa which on extension the olecranon process of the ulnar enters, limiting further extension
In some people the olecranon fossa is replaced by an olecranon foramen so that further extension is not limited and hyperextension occurs
What is the difference between pronation and suppination of the forearm?
Pronation - arms facing down
Suppination - palms facing up
What are the 3 flexors of the elbow joint?
1) Brachialis
2) Biceps brachii
3) Brachioradialis - note this is an accessory flexor only involved in flexion when the forearm is mid pronated
What is the one extensor of the elbow joint?
Triceps brachii - has 3 heads, long head, lateral head and medial head
Flexors of the elbow joint are part of what muscle compartment of the upper limb?
Anterior compartment
Why is brachioradialis an odd muscle in terms of the compartment is classified as part of?
Classified as being part of the extensor compartment of the elbow but it actually passes anteriorly to end up anterior to the elbow joint
What is the origin, insertion and innervation of the triceps brachii?
Origin
Long head - infraglenoid tubercle on the scapula
Lateral head - Posterolateral humerus above spinal groove
Medial head - posteromedial humerus below spinal groove
Insertion - Common tendon which inserts into the olecranon process of ulna
Innervation - radial nerve (C5-T1)
What is the olecranon bursa?
Bag of sinovial fluid around the olecranon process of the ulna to protect it
What is bursitis of the elbow, why does it occur and what are the symptoms?
Inflammation of the olecranon bursa
Caused by excess, repeated pressure and friction over the olecranon
Causes swelling of the bursa which may be visible and is painful on palpitation
What is the anular ligament and what is its function?
The anular liagment wraps around the head of the radius
Maintains stability of the radius
Allows rotation of the humerus to allow pronation and suppination of the forearm
Why is the radius more prone to subluxation or dislocation in childhood, what age of children does this tend to effect?
Because the annular ligament is relatively weak in childhood and cannot maintain stability of the radius, tend to affect children under 4
What is ‘nursemaids syndrome’ or ‘pulled elbow syndrome’ and what is it commonly caused by?
Type of dislocation common in childhood, often results from parents swinging child or lifting child up by one arm
Get sublaxation or dislocation of the radius
When radius pulled away from the humerus the biceps brachii which is attached to it causes the head to be pulled laterally
What other joint is contained within the capsule of the elbow joint?
Proximal radioulnar joint
What is the proximal radioulnar joint?
This is an articulation between the head of the radius and the radial notch of the ulnar
What are the 2 movements of the proximal radioulnar joint?
1) Supination. - palm up
2) Pronation. - palm down
What happens to the radius and the radial tuberosity during pronation?
Radius moves up and over ulnar, so crosses over ulnar
Radial tuberosity moves from medial to lateral
What 2 muscles contract to move the forearm from the supinated to pronated position, and what nerve innervates them?
1) Pronator teres (long muscle)
2) Pronator quadratus (square muscle)
Innervated by the median nerve
Which 2 muscles contract to move the forearm from the pronated to suppinated position and what nerves innervate them?
1) Supinator
2) Biceps brachii
Innervated by radial nerve and musculocutaneous nerve
What is the primary function of biceps brachii?
Primary function is supinator of the arm
What are the 2 common sites on the elbow where the insertions of tendons into bones become inflamed?
1) Insertions of the wrist flexor tendons into the medial epicondyle
2) Insertions of the wrist extensor tendons into the lateral epicondyle
What is golfer’s elbow?
When the insertions of the wrist flexor tendons into the medial epicondyle of the distal head of the humerus become inflammed
What are the 4 wrist flexor muscles?
1) Pronator teres
2) Flexor carpi radialis
3) Palmaris longus
4) Flexor carpi ulnaris
Which vessels and nerves are at risk of damage in a supracondylar fracture and what could be the consequences?
Anterior to the humerus have the median nerve which innervates muscles in the anterior compartment of the forearm, you also have the brachial artery anterior to the humerus which also supplies the forearm
When the humerus is pushed forward there is a risk of damage to these vessels
Hand goes blue as no blood flow, you risk necrosis unless pressure is relieved from the brachial artery and therefore emergency surgery is the treatment
The elbow joint is composed of what 3 bones?
Radius, ulnar and humerus
What is tennis elbow, what are the symptoms and treatment?
Inflammation of the insertions of the wrist extensor tendons into the lateral epicondyle of the distal head of the humerus
Symptoms = local tenderness, pain radiates into forearm along affected muscles
Treatment = rest or injection of corticosteroids if the pain is severe
What is avulsion of the medial epicondyle and how can it occur?
When medial epicondyle is pulled out of position
Happens because:
1) Medial epicondyle ossifies separately to the rest of the humerus and is only connected by cartilage until 14-20 years when fusion occurs
2) Before fusion, severe trauma causing abduction of the elbow pulls the medial epicondyle out of position
What is a big risk in avulsion of the medial epicondyle?
Stretching of the ulnar nerve
What is one of the most common humeral fractures, especially in the elderly and what risk to nerves is associated with it, how can we test for this nerve damage?
Fracture of the surgical neck of the humerus (as this is the point at which the bone narrows)
Common in the elderly and may be associated with osteoporosis
The axillary nerve wraps around the surgical neck of the humerus so is at risk of damage
To test for damage to the axillary nerve - test deltoid function (supplied by the axillary nerve) and sensation in regimental badge area
What commonly occurs in a humeral shaft fracture and what is the possible nerve damage associated?
1) Bone fractures along the radial/ spiral groove on the shaft of the humerus
2) Attachment for the deltoid is above the fracture line so it pulls the lateral fragment of the humerus laterally
3) Radial nerve runs in the radial/spiral groove and risks being damaged
4) The radial nerve supplies the extensors of the wrist thus these muscles may be paralysed
5) Braches to the triceps brachii have however been given off before the damage so this muscle will not be paralysed
What is a supracondylar fracture of the humerus and who is it most common in?
Fracture of the humerus just above the condylar, humerus gets pushed anteriorly
Common in children
