Joints - Elbow Flashcards
What type of joint is the elbow?
It is a hinge-type synovial joint.
What are the articulating surfaces of the elbow?
Consists of two separate articulations:
1) Trochlear notch of the ulna and the trochlea of the humerus.
2) Radial head and the capitulum of the humerus.
What are the features of the joint capsule in the elbow?
It has thickenings medially and laterally to form collateral ligaments.
What are the clincally relevant bursae in the elbow?
1) Intratendinous - located within the tendon of the triceps brachii.
2) Subtendinous - between the olecranon and the tendon of the triceps brachii, reducing the friction between two structures during extension and flexion of the arm.
3) Subcutaneous - between the olecranon and the overlying connective tissue (implicated in olecranon bursitis).
What are the ligaments of the elbow?
1) Radial collateral ligament - lateral side of the joint, extending from the lateral epicondyle, blending with the annular ligamnet of the radius (a ligament of the proximal radioulnar joint).
2) The ulnar collateral ligament - originates from the medial epicondyle, and attaches to the coronoid process and olecranon of the ulna.
What is the neurovasculature of the elbow?
Arterial supply is from:
The cubital anastomosis - includes recurrent and collateral branches from the brachial and deep brachial arteries.
Innervation (anteriorly):
1) Median nerve
2) Musculotaneous nerve
3) Radial nerve
Innervation (posteriorly):
1) Ulnar nerve
What are the movements of the joint?
1) Extension - triceps bachii and anconeus
2) Flexion - Brachialis, biceps brachii, brachioradialis
Note: pronation and rotate do not occur at the elbow - this occurs at the proximal radioulnar joint.
Clinical relevance: bursitis
Subcutaneous bursitis - Repeated friction and pressure on the bursa can cause it to become inflamed. Because this bursa lies relatively superficially, it can also become infected (e.g. out from a fall on the elbow).
2) Subtendinous bursitis - This is caused by repeated flexion and extension of the forearm, commonly seen in assembly line workers. Usually flexion is more painful as more pressure is put on the bursa.
Clinical relevance: dislocation
Usually occurs when a young child falls on a hand with the elbow flexed.
The humerus is driven though the weakest part of the joint capsule, which is the anterior side. The ulnar collateral ligament is usually torn and there can be ulnar nerve involvement.
Most elbow dislocations is posterior, and it is important to note that elbow dislocations are named by the postion of the ulna and radius, not the humerus.
Clinical relevance: epicondylitis (tennis elbow or golfer’s elbow)
Most of the flexor or extensor muscles in the forearm have a common tendinous origin.
The flexor muscles originate from the medial epicondyle.
The extensor muscles originate from the lateral epicondyle.
Sportspersons can develop an overuse strain of the common tendon - which results in pain and inflammation around the area of the affected epicondyle.
Typically, tennis players experience lateral epicondylitis.
Golfers experience medial epicondylitis.
Clinical relevance: supracondylar fracture
This usually due to a FOOH in a child (95%), but rarely can occur be a direct impact onto a flexed elbow.
It is typically a transverse fracture, spanning between the two epicondyles in the relatively weak epicondylar region formed by the olecranon fossa and coronoid fossa which lie opposite each other in the distal humerus.
Direct damage, or swelling can cause the interfeence to the blood supply of the forearm via the brachial artery. The resulting ischaemia can cause Vollkmann’s ischaemic contracture - uncontrolled flexion of the hand, as flexor muscles become fibrotic or short.
There can also be damage to the medial, ulnar or radial nerves. As a result, the neurobascular examination and documentation of all patients presenting with these injures is vital.
Sometimes, the blood supply can be interrupted acutely leading to a ‘pale, pulseless’ limb often in a child, usually requiring emergency surgery.
