Локтевой сустав
Нормальная рентгеноанатомия, укладки
Основной задачей рентгенографии локтевого сустава является подтверждение / исключение перелома. Другим частым запросом является исключение остеоартрита сустава.
Стандартное исследование включает в себя передне-заднюю и боковую проекции. Дополнительно может использоваться укладка для снимка головки лучевой кости.
Стандартное исследование включает в себя передне-заднюю и боковую проекции. Дополнительно может использоваться укладка для снимка головки лучевой кости.
Figure 1. Technique for AP image of the elbow
The arm is in exorotation (palm of the hand pointing upward) and in full extension. The back of the arm should be in contact with the plate (fig. 1).
The joint is then imaged from above.
A good image shows the elbow joint, plus 1/3 of the distal humerus and 1/3 of the radius/ulna.
The joint is then imaged from above.
A good image shows the elbow joint, plus 1/3 of the distal humerus and 1/3 of the radius/ulna.
Figure 2. Technique for lateral image of the elbow
Lateral image
For a purely lateral image, the shoulder should be at the same level as the elbow. Importantly, the medial side of the entire arm should be in contact with the table. Sometimes a sand bag may prove helpful.
The hand is turned vertically, the hand palm pointing toward the patient (fig. 2).
The X-rays will pass through the joint parallel to the humeral epicondyles.
A good image will show the elbow joint with about 1/3 of the distal humerus and 1/3 of the proximal radius/ulna.
For a purely lateral image, the shoulder should be at the same level as the elbow. Importantly, the medial side of the entire arm should be in contact with the table. Sometimes a sand bag may prove helpful.
The hand is turned vertically, the hand palm pointing toward the patient (fig. 2).
The X-rays will pass through the joint parallel to the humeral epicondyles.
A good image will show the elbow joint with about 1/3 of the distal humerus and 1/3 of the proximal radius/ulna.
Figure 3. Technique of a radial head image
Radial head - capitellum image
For improved visualization of the radial head, a separate radial head image can be made, e.g. in dubious/subtle fractures.
The elbow is positioned as in the lateral image. It is then imaged under a 45-degree angle, rather than cranial as in a purely lateral image (fig. 3).
For improved visualization of the radial head, a separate radial head image can be made, e.g. in dubious/subtle fractures.
The elbow is positioned as in the lateral image. It is then imaged under a 45-degree angle, rather than cranial as in a purely lateral image (fig. 3).
Figure 4. Normal anatomy of the elbow from anterior perspective.
Normal anatomy
The elbow joint consists of 3 joints (fig. 4):
The elbow joint consists of 3 joints (fig. 4):
- Humeroulnar joint: the proximal ulna consists of the olecranon (posterior side) and the coronoid process (anterior side) and articulates with the humerus through the trochlea. Its primary function is flexion and extension of the elbow.
- Radiohumeral joint: the radial head articulates with the humerus though the capitellum. Its primary function is pronation and supination of the lower arm.
- Proximal radioulnar joint: articulation between the radial head and the radial notch of the ulna. Its primary movement is rotation of the radial head.
Figure 5. Normal anatomy on a lateral elbow image
Lateral image
The capitellum and trochlea project over each other. In order to distinguish them, it is advisable to look for the contours of the radial head; between the capitellum and the radial head is a small space (= joint space of the radiohumeral joint).
The distal humerus has a concave plane at both the anterior and posterior side; the coronoid fossa at the anterior side provides space for the coronoid process in flexion and the olecranon fossa at the posterior side (=deeper!) provides space for the olecranon during extension, increasing the range of motion during elbow flexion and extension.
The elbow joint has both anterior and posterior fat tissue, the so-called fat pads. These pads are extrasynovial but are within the articular capsule. In many cases, the anterior fat pad is seen as a thin straight lucent (=black) line at the front of the distal humerus, this is a normal finding (fig. 5). Note that the surrounding musculature is denser (=whiter) than the fat pad. The posterior fat pad is invisible on normal images (the implications are explained in the Pathology section).
The capitellum and trochlea project over each other. In order to distinguish them, it is advisable to look for the contours of the radial head; between the capitellum and the radial head is a small space (= joint space of the radiohumeral joint).
The distal humerus has a concave plane at both the anterior and posterior side; the coronoid fossa at the anterior side provides space for the coronoid process in flexion and the olecranon fossa at the posterior side (=deeper!) provides space for the olecranon during extension, increasing the range of motion during elbow flexion and extension.
The elbow joint has both anterior and posterior fat tissue, the so-called fat pads. These pads are extrasynovial but are within the articular capsule. In many cases, the anterior fat pad is seen as a thin straight lucent (=black) line at the front of the distal humerus, this is a normal finding (fig. 5). Note that the surrounding musculature is denser (=whiter) than the fat pad. The posterior fat pad is invisible on normal images (the implications are explained in the Pathology section).
Figure 6. Normal anatomy on an AP image of the elbow
AP image
The humerus projects over the olecranon. The capitellum and radius are at the lateral side. At the medial side is the trochlea, articulating with the ulna (fig. 6).
The humerus projects over the olecranon. The capitellum and radius are at the lateral side. At the medial side is the trochlea, articulating with the ulna (fig. 6).
Figure 7. Normal anatomy on a radial head image
Radius - capitellum image
This image effectively visualizes the radial head and capitellum (fig. 7).
This image effectively visualizes the radial head and capitellum (fig. 7).
Figure 8. The ossification centers of the elbow. Development of the ossification centers.
Ossification centers in children
Cartilage is invisible on X-rays. In young children the elbow joint is not yet fully grown. As they mature, 6 ossification centers develop. The ossification centers grow and eventually fuse with the humerus/radius/ulna.
The sequence of development of the ossification centers is fixed (fig. 8):
The age at which the ossification centers exactly develop is not very important. More important is the order (particularly when assessing fractures). The ages mentioned here are the ages at which they will almost certainly be present, however they usually develop even somewhat earlier.
Comment: a space is frequently visible between the lateral epicondyle and the humerus. This is a normal finding as long as the epicondyle is parallel to the adjacent distal humerus
Cartilage is invisible on X-rays. In young children the elbow joint is not yet fully grown. As they mature, 6 ossification centers develop. The ossification centers grow and eventually fuse with the humerus/radius/ulna.
The sequence of development of the ossification centers is fixed (fig. 8):
- capitellum (+-1 year)
- radial head (+-3 years)
- medial (=internal) epicondyle (+-5 years)
- trochlea (+-7 years)
- olecranon (+-9 years)
- lateral (=external) epicondyle (+-11 years)
The age at which the ossification centers exactly develop is not very important. More important is the order (particularly when assessing fractures). The ages mentioned here are the ages at which they will almost certainly be present, however they usually develop even somewhat earlier.
Comment: a space is frequently visible between the lateral epicondyle and the humerus. This is a normal finding as long as the epicondyle is parallel to the adjacent distal humerus
Checklist
The following points may be used as a guide to assess an elbow X-ray.
The following points may be used as a guide to assess an elbow X-ray.
- Quality. Is this a purely AP/lateral image? Can everything be adequately assessed?
- Soft tissues: soft tissue swelling? Anterior/posterior fat pad displacement?
- Normal radiocapitellar line? Normal anterior humeral line? (See pathology section.)
- Pediatric: is the position of the ossification centers normal?
- Changes versus previous examinations?
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/