Establishing a standardized diagnostic Procedure for sonographic Imaging and Evaluation of the scapholunate Ligament

Abstract

Ultrasound has not yet been established in the diagnostic workup of scapholunate ligament lesions. We aimed to develop a standardised examination procedure to visualise and evaluate the SL ligament. Forty patients (70 hands) were examined prospectively with ultrasonography and the results were compared with arthroscopy and MRI findings. We studied the visibility of the SL ligament and the SL distance on side-to-side comparison and performed a method comparison between MRI/arthroscopy and ultrasound, testing for distinction and accordance. Cut-off values for the SL distance indicating a lesion were determined and all parameters were used for developing a score. An intact ligament appears as a hyperechogenic, fibrillary structure and shows discontinuity or a hypoechogenic space when injured. An intact ligament was visible dorsally in 89.6 % and palmarly in 83.3 %. The SL distance for an intact ligament was 5/2/5.1 mm for the dorsal/middle/palmar aspect (range 3.2-6.7/0.9-4/3.1-7.8 mm) and 6.4/3/6.3 mm (range 5-9.4/2-6.2/4-9.3 mm) for a lesion. The difference between the right and left hand with an intact ligament was a maximum of 2.1/1.1/1.8 mm, an average of 0.4/0.2/0.2 mm; in case of an injury, the maximum difference was 1.2/0.9/1.1 mm. Distance values for radial and ulnar deviation were physiological but partly unpredictable. The cut-off values determined for a lesion are 5.05 mm for the dorsal aspect (sensitivity/specificity 0.95/0.60), 1.95 mm for the middle (1/0.62) and 6.15 mm for the palmar aspect (0.55/0.85). The created sonographic SL ligament score has a high AUC (area under the curve) of 0.93, a sensitivity of 85 % and a specificity of 90 %. The parameters, especially when combined to a score, allow to state whether the SL ligament is intact or not. Ultrasound can, therefore, be recommended as a diagnostic and screening method for an SL ligament lesion und should be used as a routine tool. The criteria must be checked from a perspective with high case numbers.