How to Read Wrist X-rays

Have a **System for Reading Wrist Xrays

• Always verify the patient, laterality, and quality of xrays
• There are three main distal radius views in a series an AP, Lateral, and Oblique
• When presenting to someone (such as in fracture conference), say what views you're looking at (AP, Lateral, Oblique)
  • If you aren’t sure, just say 3 views of a R wrist… for example
• Skeletally mature or immature?
• Look for obvious injuries and comment on them. Use the most straightforward and correct answer.
  • Don’t jump into the details right away
• After you have established the obvious. Go back and systematically go through the images in each view

AP Wrist Xray: Assess the quality

• AP view: Work your way proximal to distal
  • Image centered at the distal radial ulnar joint (DRUJ) - the space between the radius and ulna
  • The long axes of third metacarpal, capitate and the radius should fall in a straight line indicating the wrist was in a neutral position
  • The pisiform and triquetrum overlap
  • Look at cortices of the radius and ulna, when outlining them, also look at medulla for any abnormalities
  • In a Posterior to Anterior (PA) view the ulnar styloid is on the ulnar-most border (left image below), in the AP view the ulnar styloid is closer to the middle of the ulnar head (right side)

Distal Radius Angles

• Review the distal radius angles (Remember: 22-11-11, volar tilt is half of the radial inclination)
  • Radial inclination (normal 22 degrees)
  • Volar tilt (11 degrees) - aka. palmar tilt
  • Radial length (11mm)

Gilula Lines

• Look at the Gilula lines 1, 2, and 3 in that order (See picture below that show Gilula lines)
• Look at the space in-between each carpal bone to look for intercarpal widening (widening between carpal bones), start looking proximal then work distal

• Gilula lines are just imaginary lines that carpal bones make that can help you tell if there is something out of place. Any break in any of the lines means that something is off.

Distal Radioulnar Joint (DRUJ)

• Look at distal radioulnar joint (DRUJ), widening of the DRUJ can communicate instability
• Look at the radiocarpal joint, 2/3rds of the lunate should articulate with the distal radius

(Llyas JAAOS, 2008).

• The left AP wrist is normal. The right shows <2/3rd of lunate articulating with the distal radius which means there is ulnar subluxation and likely a ligamentous injury, you can always compare to the other wrist.

Ulnar Variance

• Assess the ulnar variance
  • Ulnar variance is measured by drawing a transverse line at the level of the lunate fossa and a second transverse line at the level of the ulnar head, and determining the distance between the two lines. (JBJS, 2006). The forearm must be in a neutral position (not pronated or supinated).
    • Ulnar variance changes by up to a millimeter as the forearm moves from full supination to full pronation; therefore, the standard neutral position should be used
  • The image below shows ulnar positivity
    • The yellow horizontal line closer to the bottom of the picture is at the level of the lunate fossa (ulnar volar corner of the distal radius). The top line is at the level of the ulnar head. The ulnar head is more distal than the lunate fossa, therefore it is ulnar positive.

Lateral Xray: Assess the Quality

• The palmar border of the pisiform should overlap with the middle third of the scaphoid

• The image above is close to being a perfect lateral, the palmer border of the pisiform is close to overlapping with the middle third of the scaphoid
• Outline the radius and ulna then the look at the medullary canals
• Assess DRUJ, the ulna subluxing dorsally is characteristic of DRUJ instability
  • This is why it is important to have a good lateral based on pisiform overlap with the scaphoid

Capitate, Lunate, Radius in Line on the Lateral

• Check that the distal radius, lunate, and capitate are in line on the lateral (yellow line in the image)
• Then look at radius-lunate articulation (the moon shaped bone is the lunate sitting on the radius), then lunate-capitate articulation (the capitate is sitting in the cup of the lunate)
  • The outline in red is the lunate, the capitate is outlined in green. Always look and make sure the capitate is sitting in the cup of the lunate.

• Here is an example of when the capitate is no longer sitting in the cup of the lunate, and what the looks like on the AP and Lateral wrist xrays.
• This is a dorsal perilunate dislocation (notice that the lunate remained in its position articulating with the distal radius, but the capitate is dislocated dorsally)
• If the lunate was fully dislocated, this would be a “lunate dislocation”, not a perilunate dislocation

Scaphoid Position on Lateral

• Assess scaphoid position
  • Look at the scapholunate angle, normal should be 30-60 degrees (the lunate should follow the scaphoid if the scapholunate (SL) ligament is intact, example: when the scaphoid flexes with wrist flexion, so should the lunate)
  • >70 degrees where the scaphoid flexes and the lunate extends (cup points towards the dorsal wrist), this means that the scapholunate ligament is injured/not functional)

• Here is an example of a scapholunate dissociation where the scapholunate angle is >70 and the lunate no longer follows the scaphoid, most easily viewed on the lateral. There is also slight widening between the scaphoid and lunate on the AP view (the space does not match the space between the lunate and triquetrum for example).

Oblique View

• Assess quality by looking for ~1/3 overlap of the ulnar head with the radius
• Oblique distal radius xrays are great for assessing radial styloid fractures and seeing a full broad side scaphoid view (which makes it easier to see scaphoid fractures)
• Helpful for seeing triquetral fractures and hamate fractures (hamate fracture depicted below)

• Review from proximal to distal outline of radius and ulna, then carpal bones
• Outline the metacarpals
• Review the soft tissue: Proximal to distal

Dorsal Tangential View

• Mainly used in the OR under fluoroscopy to assess that the volar distal radius plate screws do not penetrate the dorsal cortex of the radius
  • Volar distal radius locking plate screws must be unicortical
  • dorsal compartment tendons, such as, extensor pollicis longus (EPL), travel directly across the dorsal distal radius, and the tips of the screws can cause them to rupture over time
    • EPL is a commonly affected tendon, so if someone can no longer extend their thumb interphalangeal joint 3-6 months after a distal radius ORIF, check a dorsal tangential view to see if there was a long screw
    • You hope that you can catch it soon enough to remove the distal radius hardware to prevent this from happening, so if a patient is having pain with tendon motion (digit extension/flexion or wrist extension/flexion, then be concerned that it is from hardware irritation.
• How to obtain the image intraoperatively:

• EPL runs just ulnar to Lister’s tubercle, the dorsal bump that you can feel on your distal radius, and the dorsal cortex of the distal radius slopes down as it goes radial (towards the thumb)
• It is easy to get fooled by the overlap of the scaphoid, making it look like your distal radius, that is why a CT scan can be helpful (axial view on the right), to assess the profile of the distal radius and how fast it slopes down from Lister’s tubercle
• In the image to the left below, the far left (furthest radial screw) is penetrating the dorsal cortex (this is bad)
• SL stands for scapholunate, the space between the scaphoid and lunate
• You also want to check that your must ulnar screw does not penetrate the distal radial ulnar joint (DRUJ)
• In the image below, the screw marked with “!!” is penetrating the 2nd dorsal compartment (read on for explanation)

• There are 6 dorsal wrist compartments (memorize this by the acronyms)
  • 1: Abductor pollicis longus (APL), Extensor pollicis brevis (EPB)
  • 2: Extensor carpi radialis longus (ECRL), Extensor carpi radialis brevis (ECRB)
  • 3: Extensor pollicis longus (EPL)
  • 4: Extensor digitorum communis (EDC), Extensor indicis proprius (EIP)
    • notice that EIP is just ulnar to the most radial EDC tendon going to the index finger, 97% of the time, EIP can be found more ulnar than the EDC tendon (important for harvest surgery) - many diagrams you find online are incorrect
  • 5: Extensor digiti minimi (EDM)
  • 6: Extensor carpi ulnaris (ECU)

Classifying Distal Radius Fractures

• From our experience, there is no one perfect classification system, we recommend basing your descriptions of distal radius fractures on whether they appear stable versus unstable. This requires knowing your predictors of instability (La Fontaine’s Criteria) and knowing your Operative Criteria.
• The classification systems below are good to be familiar with as you may be asked about them, but in practice we have not seen them commonly used.

List of Distal Radius Fracture Classification Systems

• Frykman
  • based on joint involvement (radiocarpal and/or radioulnar) +/- ulnar styloid fracture, does not guide treatment

• Fernandez
  • based on mechanism of injury, guides treatment

• Melone Classification
  • divides intra-articular fractures into 4 types based on displacement, does not guide treatment

• AO Classification
  • Comprehensive, mainly used for research purposes

(AO Distal Radius Fracture Classification: Global Perspective on Observer Agreement)

La Fontaine’s Criteria (Predictors of instability)

• Dorsal angulation > 20 degrees
• Initial radial shortening >5mm
• Associated ulnar fracture
• Dorsal comminution >50%
• Palmar comminution
• Intraarticular comminution
• Osteoporosis (Age >60 years of age was used in the original criteria)

Of these factors, radial shortening, followed by dorsal comminution, are the most predictive of instability.

Distal Radius Operative Criteria

(Commit these to memory):

• Open fractures
• Associated neurovascular or tendon injury
• Associated fracture of the carpal bones
• Associated acute carpal tunnel syndrome
• High-energy injuries
• Radiographic findings indicating instability (see La Fontaine’s Criteria: ([AO Distal Radius Fracture Classification: Global Perspective on Observer Agreement)](How%20to%20Read%20Wrist%20X-rays%20de4d9d2ac9794fe6b6359c9bc3a2a88b.md)
  • Volar or dorsal comminution
  • Displaced intra-articular fractures >2mm
  • Radial shortening >5mm
• Associated ulnar fracture (not ulnar styloid)
• Severe osteoporosis (often depends on displacement)
• Articular margin fractures (dorsal and volar Barton’s fractures, aka. Volar or Dorsal sheer fractures)
  • Requires an intact posterior cortex for volar Barton/sheer fractures, or volar cortex for dorsal sheer fractures
• Severely comminuted and displaced extra-articular fractures
• Die-punch fractures
  • Volar ulnar corner fractures
• Progressive loss of volar tilt and radial length following closed reduction and casting

Case example:

How would you read this xray?

• Answer: “This is an AP and Lateral of a left wrist in a skeletally mature individual showing an extra articular distal radius fracture. (Generally it is good to avoid eponyms, like Colles Fracture).
• Another descriptor would be to say, “A dorsally angulated extraarticular distal radius fracture with associated ulnar styloid fracture”.
• If you are in a fracture conference, that is all you may have time to say, but you should be looking back over the image using a system. Work from proximal to distal, outline the bones, look in the medullary canals, visualize important/imaginary lines to help you pick up on abnormalities, and don’t forget about the surrounding soft tissue!