Elizabeth A. King
Daniel A. Osei
Safi Faruqui

Bony Anatomy

The distal end of the radius is a plateau that articulates with the scaphoid and lunate as well as the ulnar head.
The concave articular surface of the distal radius is divided distally into two articular facets: one for the scaphoid and one for the lunate. These are separated by a longitudinal sagittal ridge.
Medially, a concave articular surface articulates with the ulnar head. This is where forearm rotation occurs as the radius rotates around the ulna during pronation and supination. Restoration of each of these articular surfaces is paramount for success in treating distal radius fractures.
Multiple views of the wrist are needed to accurately assess displacement, angulation, rotation, and shortening of the fracture.
The dorsal cortex of the distal radius has a bony prominence at Lister’s tubercle with many undulations that support the extensor compartments (Fig. 11-1).
- Knowledge of this anatomy is vital to avoid dorsal cortex screw penetration and irritation of the extensor tendons with volar plate fixation.

Gardner1e-ch011-image001 — Figure 11-1 Axial CT image demonstrates the bony undulations of dorsal cortex of the distal radius.

Radiographic Anatomy

PA
- Standard PA views show the distal radius and its carpal and ulnar articulations, which normally are smooth and congruent.
- Radial height (12 mm), radial inclination (average 23 degrees), coronal shift, and ulnar variance (average 1 mm negative) are measured on this view (Fig. 11-2).
- Coronal fracture displacement can be assessed in this view, though various images in different planes are necessary to quantify intra-articular involvement, displacement, and angulation.
- Neutral PA view is useful in identifying radioulnar joint disruption.
Lateral
- This view is important in assessing the radiocarpal articulation, dorsal/volar displacement of the fracture fragment(s), and any corresponding carpal abnormalities.
- On a true lateral view, the palmar cortex of the pisiform should overlie the central third of the interval between the distal scaphoid pole and the capitate head.¹
- Volar tilt (average 11 degrees), AP distance (average 20 mm in males, 18 mm in females), and the teardrop angle are measured on this view (Fig. 11-3).
  - The teardrop represents the volar rim of the lunate facet, the mechanical buttress for subluxation of the lunate.²
  - Teardrop angle is measured between a line drawn along the central axis of the teardrop and a line along the central axis of the radial shaft. Normal teardrop angle is approximately 70 degrees.²
- VISI (volar intercalated segmental instability) and DISI (dorsal intercalated segmental instability) deformities of the lunate can signify lunotriquetral or scapholunate ligament injury, respectively (Fig. 11-4).
- Smith, Colles, and Barton fractures are best confirmed on this view (Fig. 11-5).
Pronation/supination PA oblique
- Oblique views are taken with the forearm and wrist in 45 degrees of pronation or supination (Fig. 11-6).
- These are important views that can show intra-articular involvement not seen on standard AP and lateral views.
- Pronation oblique view best visualizes the radial styloid and is useful in assessing subchondral screw placement after plate placement.³
- Supination oblique view allows evaluation of the dorsal ulnar facet of the lunate fossa.
PA tilt view
- Taken by directing the PA view 10 degrees from distal to proximal (Fig. 11-7).
- View is parallel to the radiocarpal joint and accounts for the dorsal lip of the radius.
- Proven to be an effective view to verify subchondral screw placement, especially for radial styloid screws.⁴
Lateral tilt view
- Taken by directing fluoroscopy beam 25 to 30 degrees from distal to proximal (Fig. 11-8).
- Provides better visualization of the distal radius articular surfaces, especially the scaphoid and lunate facets, as the articular surface has approximately 23 degrees of radial inclination.
- Necessary after volar locked plating to examine articular congruency of both the scaphoid and lunate facets, restoration of volar tilt, and subchondral placement of distal locking screws or pegs.
Dorsal horizon view
- This newly described dorsal tangential view provides a more complete visualization of the triangular distal radius cortex, particularly at Lister’s tubercle, allowing for a more accurate assessment of screw protrusion (Fig. 11-9).⁵^–⁸
- Obtained by supinating the forearm, hyperflexing the wrist, and aiming the beam of the image intensifier along the long axis of the radius.
Advanced imaging (CT)
- Helpful for further evaluation of comminution, intra-articular involvement, and lunate facet congruity.
- Can also identify dorsal shear fragments and centrally impacted fractures.
- Intra-articular involvement on plain films will many times warrant obtaining a CT scan for preoperative fracture fixation planning (Fig. 11-10).
Advanced imaging (MRI)
- Although not commonly used, this modality can be employed to investigate concomitant soft tissue injuries such as SL/LT ligament disruption or TFCC tears.