Normal Radiolunate Angle Size on Radiography
The radiolunate angle describes the angular relationship between the long axis of the radius and the long axis of the lunate on a lateral wrist radiograph. It is a fundamental measurement in the assessment of carpal alignment and kinematics. Accurate determination of this angle is essential for identifying dorsal or volar intercalated segment instability (DISI/VISI) and guiding surgical planning.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Lateral | -15-15¡ |
Clinical Significance
A normal radiolunate angle falls between -15° and +15° on the lateral view. Values outside this range indicate pathological carpal malalignment. A positive angle exceeding +15° suggests dorsiflexion of the lunate, consistent with DISI (Dorsal Intercalated Segment Instability), most commonly associated with scapholunate ligament disruption. A negative angle beyond -15° indicates volar flexion of the lunate, characteristic of VISI (Volar Intercalated Segment Instability), often linked to lunotriquetral ligament injury.
Clinical pitfalls include suboptimal wrist positioning during radiography, which can artificially alter the measured angle. The radiolunate angle should always be interpreted alongside the scapholunate angle (normal 30°–60°) and capitolunate angle for comprehensive carpal instability evaluation.
- Scapholunate dissociation (DISI pattern)
- Lunotriquetral ligament tear (VISI pattern)
- Perilunate dislocation or fracture-dislocation
- Chronic carpal instability following distal radius fracture malunion
- Inflammatory arthropathy with ligamentous laxity
Reference: Schmitt R, Lanz U. Diagnostic Imaging of the Hand. TIS. (2008).
Imaging Notes
The radiolunate angle is measured on a true lateral wrist radiograph with the wrist in neutral position, forearm pronated, and the beam centered on the carpus. The long axis of the radius is drawn through the midpoints of the radial shaft, and the long axis of the lunate is drawn perpendicular to its proximal and distal articular surfaces. The angle subtended by these two lines represents the radiolunate angle. Patient positioning is critical — even slight wrist flexion or extension will shift the measurement outside the normal range and lead to false-positive diagnoses.
When plain radiographs are equivocal, dynamic fluoroscopy or MRI with dedicated wrist coils can provide additional information about ligamentous integrity and subtle instability patterns not captured on static views.