Figure 1. Orientation lines in the elbow joint; normal radiocapitellar line & anterior humeral line
Патология локтевого сустава
Lines (fig. 1):
Lines (fig. 1):
- A radiocapitellar line can be drawn on each image: it runs through the central radius and passes the central capitellum on a normal image. Important: this rule applies to EACH image, so not only a purely lateral image.
- The anterior humeral line is drawn along the front of the humerus and passes the anterior 1/3 of the capitellum.
Figure 2. Normal elbow versus joint effusion with positive fat pads
Fat pads:
When there is joint effusion (fluid/blood/pus) or synovitis, the capsule will become distended. Fat pads are located at the anterior and posterior side of the distal humerus. When the effusion becomes large enough, the fat tissue can be displaced away from the humerus. This is termed a so-called ‘positive fat pad’ (fig. 2).
Important: In a trauma setting, a displaced posterior fat pad almost always indicates a fracture, particularly in adults. An abnormal posterior fat pad in children is relatively less specific than in adults, as soft tissue damage may also be associated with joint effusion.
When there is joint effusion (fluid/blood/pus) or synovitis, the capsule will become distended. Fat pads are located at the anterior and posterior side of the distal humerus. When the effusion becomes large enough, the fat tissue can be displaced away from the humerus. This is termed a so-called ‘positive fat pad’ (fig. 2).
Important: In a trauma setting, a displaced posterior fat pad almost always indicates a fracture, particularly in adults. An abnormal posterior fat pad in children is relatively less specific than in adults, as soft tissue damage may also be associated with joint effusion.
Figure 3. Radial head fracture with positive anterior & posterior fat pad
Radial head fracture
Trauma mechanism
In many cases indirect trauma caused by valgus/pronation stress in an abducted arm. A common cause is falling on an outstretched arm.
Findings (fig. 3)
Trauma mechanism
In many cases indirect trauma caused by valgus/pronation stress in an abducted arm. A common cause is falling on an outstretched arm.
Findings (fig. 3)
- Often very subtle, fractures can therefore be overlooked easily.
- Look for joint effusion and therefore fat pad displacement.
- Watch carefully for cortex interruptions and densities that should not be there.
- Other abnormalities you may encounter include coronoid process fracture.
Figure 4. Mason classification
Classification according to Mason (fig. 4)
- Type I: fracture without dislocation.
- Type II: partial intra-articular fracture with dislocation of > 2mm.
- Type III: comminuted fracture of the entire radial head.
- Type IV: fracture with dislocation of the elbow joint.
Figure 5. Radial head luxation in a 6-year-old child. Note the radiocapitellar line no longer runs through the central capitellum
Radial head luxation
Radial head luxation means the radial head has become dislocated; the articulation with the ulna and humerus is abnormal. Always check the radiocapitellar line when a radial head luxation is suspected. In luxation, the line no longer runs through the central capitellum (fig. 5).
Pulled elbow/Nursemaid's elbow
A classical story where the child (particularly 2 or 3 years old) is suddenly pulled by the arm when it is in extension. The radial head becomes subluxated. The child holds the elbow in flexion and pronation and refuses to extend the elbow.
Theory: the radial head is fixed by the annular ligament. The above-described force may cause subluxation of the radial head under the ligament.
Treatment: multiple pronation/supination movements of the lower arm will cause the radial head to return to its anatomical position (sometimes with a ‘click’).
The X-ray will then be normal. A pulled elbow/Nursemaid's elbow is a clinical diagnosis.
Radial head luxation means the radial head has become dislocated; the articulation with the ulna and humerus is abnormal. Always check the radiocapitellar line when a radial head luxation is suspected. In luxation, the line no longer runs through the central capitellum (fig. 5).
Pulled elbow/Nursemaid's elbow
A classical story where the child (particularly 2 or 3 years old) is suddenly pulled by the arm when it is in extension. The radial head becomes subluxated. The child holds the elbow in flexion and pronation and refuses to extend the elbow.
Theory: the radial head is fixed by the annular ligament. The above-described force may cause subluxation of the radial head under the ligament.
Treatment: multiple pronation/supination movements of the lower arm will cause the radial head to return to its anatomical position (sometimes with a ‘click’).
The X-ray will then be normal. A pulled elbow/Nursemaid's elbow is a clinical diagnosis.
Figure 6. Essex-Lopresti fracture. The AP image of the elbow reveals a radial head fracture-luxation; the AP image of the wrist shows luxation of the distal radioulnar joint (DRU joint).
Essex-Lopresti fracture
A comminuted fracture of the radial head by a fall on an outstretched arm may be associated with tearing of the interosseous membrane of the lower arm. The force released during the trauma will be transferred distally through the interosseous membrane to the distal radioulnar joint (DRU joint), causing luxation of the DRU joint. This trauma type is also known as the Essex-Lopresti fracture.
Unfortunately the Essex-Lopresti fracture is not always recognized, simply because the wrist joint is not imaged. This may eventually cause permanent lower arm/wrist symptoms.
Learning point: in a comminuted fracture of the radial head, the wrist joint should always be imaged to exclude an Essex-Lopresti fracture.
A comminuted fracture of the radial head by a fall on an outstretched arm may be associated with tearing of the interosseous membrane of the lower arm. The force released during the trauma will be transferred distally through the interosseous membrane to the distal radioulnar joint (DRU joint), causing luxation of the DRU joint. This trauma type is also known as the Essex-Lopresti fracture.
Unfortunately the Essex-Lopresti fracture is not always recognized, simply because the wrist joint is not imaged. This may eventually cause permanent lower arm/wrist symptoms.
Learning point: in a comminuted fracture of the radial head, the wrist joint should always be imaged to exclude an Essex-Lopresti fracture.
Figure 7. Monteggia fracture; fracture of the proximal ulna and radial head luxation. Note the abnormal radiocapitellar line.
Monteggia fracture
A proximal ulnar fracture may be associated with tearing of the interosseous membrane (= fibrous connection between the ulna and radius), continuing up to the stabilizing ligaments surrounding the radial head. This will eventually result in a radial head luxation. The combination of a proximal ulnar fracture and radial head luxation is termed a Monteggia fracture. The trauma mechanism is frequently a fall on an outstretched arm.
The ulnar fracture is usually recognized easily, but the radial head luxation can be very subtle. This may lead to an untreated radial head luxation (with associated complications). So always check the position of the radial head in the presence of a proximal/mid-shaft ulnar fracture.
A proximal ulnar fracture may be associated with tearing of the interosseous membrane (= fibrous connection between the ulna and radius), continuing up to the stabilizing ligaments surrounding the radial head. This will eventually result in a radial head luxation. The combination of a proximal ulnar fracture and radial head luxation is termed a Monteggia fracture. The trauma mechanism is frequently a fall on an outstretched arm.
The ulnar fracture is usually recognized easily, but the radial head luxation can be very subtle. This may lead to an untreated radial head luxation (with associated complications). So always check the position of the radial head in the presence of a proximal/mid-shaft ulnar fracture.
Figure 8. Mechanism of the supracondylar humeral fracture.
Supracondylar humeral fracture
Children often fall on an outstretched hand. In this setting, the supracondylar humeral fracture is the most common fracture in children.
Trauma mechanism (fig. 8)
Children often fall on an outstretched hand. In this setting, the supracondylar humeral fracture is the most common fracture in children.
Trauma mechanism (fig. 8)
- Falling on an outstretched arm, resulting in hyperextension. The olecranon bends backward too far, compressing the weak point in the distal humerus, the coronoid fossa (mechanism similar to bottle opener).
Figure 9. Supracondylar humeral fracture in a 9-year-old child.
Findings
- Joint effusion with displaced fat pads (= positive fat pads).
- The anterior humeral line no longer runs through the middle 1/3 segment of the capitellum, but the capitellum is often posterior of the anterior humeral line.
- A cortex interruption proximal of the humeral condyles. Note: cortex interruption is sometimes difficult to see due to impression.
Figure 10. Lateral humeral condylar fracture according to the Milch classification.
Lateral humeral condylar fracture
After the supracondylar fracture, the lateral humeral condylar fracture is the next most common fracture in children. A fracture of the lateral humeral condyle is caused by a varus force. This may be caused by direct trauma from lateral or when the child falls on the lateral side of its arm.
The extension of the fracture line is variable.
After the supracondylar fracture, the lateral humeral condylar fracture is the next most common fracture in children. A fracture of the lateral humeral condyle is caused by a varus force. This may be caused by direct trauma from lateral or when the child falls on the lateral side of its arm.
The extension of the fracture line is variable.
- Figure 11. Lateral humeral condylar fracture continuing into the capitellar ossification center (Milch type 1).
The Milch classification distinguishes two types (fig. 10):
- Type 1 (least common): the fracture runs through the ossification centers and reaches up to the surface of the radiocapitellar joint. This is a Salter-Harris type IV fracture.
- Type 2 (most common): the fracture is medial of the capitellum and ends in the non-ossified cartilage. As the non-ossified cartilage is not visible on X-ray, it is not always clear whether the fracture continues (= Salter-Harris type IV) up to the joint surface or not (= Salter-Harris type II).
Figure 12. Avulsion fracture of the medial epicondyle with varying degrees of dislocation. Illustration 4 shows significant dislocation where the medial epicondyle has become trapped in the joint.
Medial humeral epicondylar fracture
The medial epicondyle of the humerus is the insertion site of the lower arm flexor muscles. In the event of a strong force (as in throwing a ball) an avulsion fracture may develop of the medial epicondyle (= little leaguer's elbow). In a severe dislocation, it may become trapped in the joint (fig. 12/13).
A displaced fat pad may be absent and the avulsion fracture may be very subtle. Sometimes an image of the contralateral (unaffected) elbow can be helpful.
The medial epicondyle of the humerus is the insertion site of the lower arm flexor muscles. In the event of a strong force (as in throwing a ball) an avulsion fracture may develop of the medial epicondyle (= little leaguer's elbow). In a severe dislocation, it may become trapped in the joint (fig. 12/13).
A displaced fat pad may be absent and the avulsion fracture may be very subtle. Sometimes an image of the contralateral (unaffected) elbow can be helpful.
Figure 13. A medial epicondylar fracture with some dislocation in a 9-year-old child. Also note the associated marked soft tissue swelling.
For your attention:
- the trochlear ossification center appears AFTER the appearance of the medial epicondyle on an elbow X-ray. When in the absence of a medial epicondyle an ossification center is nevertheless visible at the location of the trochlea, be aware this may be the dislocated medial epicondyle (and therefore not the trochlear ossification center).
- Always look for the presence of soft tissue swelling at the medial side. This may be an indication/substantiation of a medial epicondylar fracture diagnosis.
Figure 14. Olecranon fracture.
Olecranon fracture
The triceps insert on the olecranon. In the event of a fracture, traction of the triceps may displace the loose fragment in the cranial direction.
Trauma mechanism
The triceps insert on the olecranon. In the event of a fracture, traction of the triceps may displace the loose fragment in the cranial direction.
Trauma mechanism
- Direct fall on olecranon.
- Fall on extended arm with some flexion in the elbow.
- Avulsion fracture.
- Stress fracture (e.g. in top athletes).
- Often easily recognized on lateral images with obvious cortex interruption.
- There is usually proximal dislocation of the fragment.
Distal humeral fracture
Elderly osteoporotic patients may develop a distal humeral fracture after a fall, which is frequently a (simple) transversal fracture.
In younger patients, intercondylar fractures are also seen with a T or Y configuration. The intra-articular fracture may continue up to the trochlea.
Note: in an extra-articular fracture the distal humerus, displaced fat pads may be absent.
Elderly osteoporotic patients may develop a distal humeral fracture after a fall, which is frequently a (simple) transversal fracture.
In younger patients, intercondylar fractures are also seen with a T or Y configuration. The intra-articular fracture may continue up to the trochlea.
Note: in an extra-articular fracture the distal humerus, displaced fat pads may be absent.
Figure 15. Posterior elbow luxation, associated with a small chip fracture (possibly originating from the coronoid process).
Elbow luxation
A fall on an outstretched hand with the elbow in hyperextension may cause elbow luxation. An elbow luxation is virtually always a posterior luxation; the olecranon is posterior of the humerus (fig. 15).
Luxation is regularly associated with fractures, particularly of the radial head and coronoid process.
The combination of a posterior elbow luxation, radial head fracture and coronoid process fracture is also termed the ‘terrible triad’.
A fall on an outstretched hand with the elbow in hyperextension may cause elbow luxation. An elbow luxation is virtually always a posterior luxation; the olecranon is posterior of the humerus (fig. 15).
Luxation is regularly associated with fractures, particularly of the radial head and coronoid process.
The combination of a posterior elbow luxation, radial head fracture and coronoid process fracture is also termed the ‘terrible triad’.
Figure 16. Osteoarthritis at the elbow (the humeroulnar joint and the radiohumeral joint and the proximal radioulnar joint).
Osteoarthritis
Osteoarthritis is wear and tear on the cartilage. It is associated with a diversity of symptoms. Patients may complain about progressive load-dependent pain and/or reduced elbow function.
The osteoarthritis may be primary with no obvious identifiable cause. Secondary osteoarthritis may develop after e.g. a fracture or secondary to joint disease (e.g. rheumatoid arthritis or infection).
Radiological characteristics of osteoarthritis (fig. 16):
Osteoarthritis is wear and tear on the cartilage. It is associated with a diversity of symptoms. Patients may complain about progressive load-dependent pain and/or reduced elbow function.
The osteoarthritis may be primary with no obvious identifiable cause. Secondary osteoarthritis may develop after e.g. a fracture or secondary to joint disease (e.g. rheumatoid arthritis or infection).
Radiological characteristics of osteoarthritis (fig. 16):
- Narrowing of the joint space (secondary to cartilage loss).
- Subchondral sclerosis (increased bone production secondary to increased pressure with cartilage loss).
- Osteophyte formation (bone exostoses attempting to increase the joint surface).
- Subchondral cysts (secondary to microfractures of the subchondral bone and pressure of the synovial fluid).
Sources
- B.J. Manaster et al. The Requisites – Musculoskeletal Imaging (2007).
- N. Raby et al. Accident & Emergency Radiology – A Survival Guide. (2005).
- K.L. Bontrager, J.P. Lampignano. Textbook of Radiographic Positioning and Related Anatomy. 2014 (8th edition)
- http://www.startradiology.com/