Normal Scapholunate Angle Size on Radiography
The scapholunate angle is the angular relationship between the long axes of the scaphoid and lunate on a lateral wrist radiograph. It serves as a critical measure of carpal alignment and the integrity of the scapholunate ligament complex. Accurate assessment of this angle is essential in evaluating wrist pain, trauma, and suspected carpal instability.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Lateral | 30-60¡ |
Clinical Significance
A normal scapholunate angle of 30–60° reflects balanced carpal kinematics. Deviation beyond this range suggests disruption of the intrinsic or extrinsic wrist ligaments. An angle greater than 60° is associated with Dorsal Intercalated Segment Instability (DISI), the most common pattern seen after scapholunate ligament tear, where the lunate tilts dorsally. Conversely, an angle less than 30° raises concern for Volar Intercalated Segment Instability (VISI), which may indicate lunotriquetral ligament disruption or midcarpal instability.
Clinicians should be aware that positioning errors and wrist deviation can alter the measured angle, so the radiograph must be taken in strict neutral position. A single abnormal value should always be correlated with clinical findings and contralateral comparison views.
- Scapholunate ligament tear (acute or chronic)
- DISI deformity (angle >60°)
- VISI deformity (angle <30°)
- Perilunate dislocation or fracture-dislocation
- Inflammatory arthropathy with carpal collapse
Reference: Bowden G, McNally M, Thomas S et al. Oxford Handbook of Orthopaedics and Trauma. Oxford University Press. (2010).
Imaging Notes
The scapholunate angle is measured on a true lateral radiograph of the wrist with the forearm in neutral rotation, the wrist in neutral flexion-extension, and the fingers extended. The scaphoid axis is drawn along the palmar convexities of its proximal and distal poles, while the lunate axis is drawn perpendicular to a line connecting its dorsal and volar horns. The angle subtended between these two lines represents the scapholunate angle.
Strict positioning is paramount — even mild wrist flexion or extension can spuriously alter the measured angle. Dynamic fluoroscopic views under stress (radial/ulnar deviation) may be used as an adjunct to unmask occult instability not apparent on static images.