Abstract
Background Scapholunate instability (SLI) is the most common form of carpal instability. Early
detection of SLI is imperative as early reconstructive procedures can potentially
prevent the natural history of progressive degenerative arthritis. After wrist arthroscopy,
magnetic resonance imaging (MRI) remains the next best noninvasive diagnostic option;
however, access still remains costly and is often limited in many health care systems
worldwide. In this article, we describe a novel device that allows for dynamic X-rays
to be taken, accentuating the scapholunate (SL) widening.
Description of Technique Twist X-ray views are generated by the patient clenching a device that combines the
standard clenched fist views with ulnar deviation and supination. The test is easy
to perform and functions by combining a higher grip force with the ulnar deviation
and pronation effects of the extensor carpi ulnaris tendon, thus accentuating the
SL gap in dynamic instability.
Patients and Methods We present a series of four patients with dynamic SLI and compare the findings of
the Twist X-rays with conventional wrist X-rays series, including standard anteroposterior,
lateral, radial, and ulna deviation, clenched fist, and pencil grip views.
Results In all the four patients, there was substantial dynamic SL widening. The SL interval
increased from a mean of 1.8 mm (range: 1.5–2.8) on posteroanterior X-rays to 6.3 mm
(range: 4.6–8.2) with the Twist views. Interestingly, on the pencil grip view, the
mean widening was only 1.5 mm (range: 1–2.8 mm).
Conclusion The authors describe a novel device that allows for improved detection of dynamic
SL ligament instability when performing stress X-ray views of the wrist.
Level of Evidence This is a Level IV study.
Keywords
scapholunate instability - X-ray - wrist - scapholunate ligament - scapholunate advanced
collapse - arthritis
