Bilateral Ulnar Deviation Supination Stress Test to Assess Dynamic Scapholunate Instability

Abstract

We describe a new radiologic test to assess the integrity of the scapholunate ligament in dynamic scapholunate dysfunction. A bilateral forearm-holding device was designed to perform a comparative radiographic assessment of the scapholunate joint gap during resisted isometric contraction of the extensor carpi ulnaris muscle with full supination of the forearm. The concept is based on the known scaphoid pronation effect of this muscle. Clinical data from 12 patients were collected retrospectively and used to analyze the patients' symptomatic and asymptomatic (contralateral) wrists with a newly developed test called the Bilateral Ulnar Deviation Supination (BUDS) test. A wrist arthroscopy was performed in all cases as a reference standard for the radiologic test. The test was positive in 7 patients, with a mean scapholunate joint gap of 4.8 mm. The mean differences in the scapholunate joint gaps between both wrists were 2.6 mm in BUDS-positive patients and 0.2 mm in BUDS-negative patients. A Geissler stage III or IV scapholunate ligament rupture was confirmed in all BUDS-positive patients; by contrast, BUDS-negative patients exhibited either no lesion or a Geissler stage I injury. The BUDS test is a new radiologic test based on proven biomechanical effects that is able to accurately assess dynamic scapholunate dysfunctions. The analysis carried out found a correlation between radiographic and arthroscopic findings. Further research is needed to confirm the validity and reliability of the test. Therapeutic III.