The efficacy of ultrasound in the evaluation of dynamic scapholunate ligamentous instability

Background: The accuracy of diagnostic imaging modalities that are currently used to evaluate dynamic scapholunate ligamentous instability is equivocal. Ultrasound is commonly used for a wide variety of diagnostic purposes in orthopaedics. The purpose of the present study was to determine the efficacy of ultrasound in the diagnosis of dynamic scapholunate ligamentous instability. Methods: Two groups of individuals were prospectively studied. Group A included patients with a clinical diagnosis of unilateral dynamic scapholunate ligamentous instability, and Group B included asymptomatic volunteer control subjects. Dynamic ultrasound examinations of the dorsal portion of the scapholunate ligament in both wrists of all individuals were performed by radiologists. The radiologists were blinded with regard to the group to which each person belonged as well as with regard to the affected wrist in the patients in Group A. Arthroscopic examinations of the affected wrist in all of the patients in Group A were then performed by surgeons who were blinded with regard to the results of the ultrasound examination, and the results of the arthroscopic and ultrasound examinations were compared. The ability of ultrasound to discern asymptomatic from symptomatic individuals was also determined. Results: Over a period of 1.5 years, a total of sixty-four wrists were evaluated in fourteen patients (Group A) and eighteen normal subjects (Group B). All fourteen nonaffected wrists in Group A and all thirty-six wrists in Group B were correctly identified as normal with use of ultrasound. Of the fourteen affected wrists in Group A, thirteen were found to have scapholunate ligament laxity on the basis of arthroscopy (twelve wrists) or arthrotomy (one wrist); six of these thirteen wrists had been correctly identified as abnormal with use of ultrasound (a true-positive result), and seven had false-negative results. There was one true-negative result. The ability of ultrasound to differentiate between normal and abnormal wrists was significant (p < 0.001). For the sixty-four wrists, statistical analysis revealed that ultrasound had a sensitivity of 46.2%, a specificity of 100%, and an accuracy of 89.1%. Conclusions: We conclude that ultrasound has a high specificity and accuracy but a low sensitivity for the evaluation of dynamic scapholunate ligamentous instability, and we recommend its use as an adjunct to other diagnostic modalities for this purpose. Level of Evidence: Diagnostic study, Level IV-1 (case-control study).