Ultrasonographic changes after steroid injection in carpal tunnel syndrome.

Abstract

To determine the ultrasonographic changes after steroid injection in carpal tunnel syndrome (CTS) and to evaluate the diagnostic value of ultrasound in post-treatment examination with clinical correlation. Twenty-seven wrists with idiopathic CTS after a single injection of 40mg of prednisolone hydrochloride were prospectively studied using a high-resolution ultrasound. Axial images of the wrists were obtained at the level of the distal radius, pisiform and hamate prior to and 1, 4 and 8weeks after steroid injection. The cross-sectional area (CSA, mm2) and flattening ratio (FR) of the median nerve were measured. The bowing of the flexor retinaculum (palmar displacement: PD, mm) and the transverse sliding distance of the median nerve (TSD, mm) during flexion-extension of the index finger were computed. Pre- and post-injection ultrasonographic findings were analyzed in relation to clinical parameters such as pain score. At all levels of the wrist, the CSA decreased significantly at 1week after the injection, which continued to 8weeks post-injection. The PD also diminished significantly 1week after the injection. Furthermore, the TSD significantly increased from 1week after injection, which lasted to the end of this study. The CSA, PD and TSD showed significant correlation with improvement of pain scores. Ultrasound is useful in follow-up examinations of CTS. Significant ultrasound findings after steroid injections in CTS include decreased swelling of the median nerve, decreased bowing of the flexor retinaculum and increased mobility of the median nerve. All of them significantly correlate with clinical symptoms.