How to Read Elbow Radiograph

📺 Video Link

---

How to Read Elbow Radiograph:

• Reading an elbow x-ray can be challenging, especially when trying to identify fractures after an acute elbow injury. 
• A systematic approach can aid in the radiographic recognition of occult signs of injury. 
• When reading an adult elbow x-ray, it is important to review the alignment, fat pads for effusion, and bony cortex. Below are the steps to follow when reading an elbow x-ray.

Step number 1:

• Alignment: Check the anterior humeral line and the radiocapitellar line. 
• Anterior Humeral line: This line should intersect the middle third of the capitellum on the lateral view. Fractures usually result in displacement of the capitellum posteriorly (versus anteriorly). Signs of humeral fracture are also commonly subtle; breakage may only be evidenced by an abnormal anterior humeral line. 
• Radio-capitellar line: This line is drawn through the middle of the radius posteriorly/rostrally and should bisect the capitellum on both the lateral and the AP elbow radiograph. Failure to align properly indicates a radial head dislocation that requires prompt reduction if neuro-vascular compromise is to be avoided. 

Step number 2:

• Effusion: Check for raised fat pads. 
• Anterior fat pad evaluation: A visible anterior fat pad can be normal; it is a small radiolucent shadow adherent to the anterior aspect of the distal humerus. An abnormal anterior fat pad is described as a "sail sign" because it is unusually prominent and bows outward to form a triangular shape. After trauma, blood can accumulate in the intraarticular space and push the fat pad anteriorly; a positive sail sign in the setting of trauma is a reliable indication of an intraarticular fracture – even if no fracture line can be identified. 
• Posterior fat pad evaluation: Radiographic visualization of a posterior fat pad is never normal and always signifies fluid in the intraarticular space. Again, in the setting of trauma, this strongly implies fracture of an articular surface. 

Step number 3: 

• Bone cortex: Check around every bone on the film. 
• Hourglass sign or figure of eight: Search for an adequate "hourglass sign", or "figure of eight" at the distal humerus. If absent, the study is not a true lateral, and interpretation of steps 1 through 2 is less reliable.  
• Radial head: Careful inspection of the radial head is paramount since fracture lines are often not visible; look for subtle disruptions in the cortical contour. 
• Olecranon: Look for fracture lines and subtle disruptions in cortical contour.

Pediatric elbow x-ray:
When reading a pediatric elbow x-ray, it is important to distinguish normal from abnormal anatomy:

1. Normal anatomy and development: Radiographic evaluation of the skeletally immature elbow requires knowledge of the normal sequence and appearance of the secondary ossification centers of the elbow. 
2. Radiographic evaluation: Assessment of the radiocapitellar joint, anterior humeral line, and Baumann’s angle is important. 
3. Specific injuries: Supracondylar humerus fractures are the most common type of elbow fracture in children. Several radiographic parameters are used to evaluate for the presence of a supracondylar humerus fracture.

CRITOE:
CRITOE is a mnemonic used to determine skeletal age from x-rays of a child's elbow. It stands for:

• C: Capitellum
• R: Radial head
• I: Internal (medial) epicondyle
• T: Trochlea
• O: Olecranon
• E: External (lateral) epicondyle

These letters represent the order in which the secondary ossification centers of the elbow appear and fuse. The appearance of secondary ossification centers of the elbow is predictable, but may vary from patient to patient based on sex, maturity, and may even vary from one extremity to the other. The CRITOE mnemonic can be used to remember the chronologic order of ossification.