gms | German Medical Science

Objectives/Interrogation: 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, MRI remains the next best non-invasive diagnostic option, however access still remains costly and often limited in many healthcare systems worldwide. In this paper, we describe a novel device that allows for dynamic x-rays to be taken, accentuating the SL widening.

Methods: Twist x-ray views are generated by the patient clenching a device which 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 scapholunate gap in dynamic instability.

We present a series of 4 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, clench fist and pencil grip views.

Results and Conclusions: In all 4 patients there was substantial dynamic scapholunate widening. The SL interval increased from a mean of 1.8mm (range, 1.5-2.8) on PA x-rays to 6.3mm (range, 4.6-8.2) with the Twist views. Interestingly, on the pencil grip view, the mean widening was only 1.5mm (range, 1-2.8mm).

Here we describe a novel device that allows for improved detection of dynamic scapholunate ligament instability when performing stress x-ray views of the wrist.