Effectiveness of ultrasound-guided carpal tunnel injection using in-plane ulnar approach: a prospective, randomized, single-blinded study

Abstract

The objective of this study is to evaluate the degree of symptom improvement and the change of electrophysiological and ultrasonographic findings after sonographically guided local steroid injection using an in-plane ulnar approach in carpal tunnel syndrome (CTS). Seventy-five cases of 44 patients diagnosed with CTS were included and evaluated at baseline and at 4 and 12 weeks after injection. All patients received injection with 40 mg of triamcinolone mixed with 1 mL of 1% lidocaine into the carpal tunnel using an in-plane Ultrasound (US)-guided ulnar approach, out-plane US-guided approach, and blind injection. For clinical evaluation, we used the Boston Carpal Tunnel Questionnaire (BCTQ) and electrophysiological tests. The ultrasonographic findings were also evaluated with regard to cross-sectional area and the flattening ratio of the median nerve. Subjective symptoms measured by BCTQ and median nerve conduction parameters showed significant improvement at 4 weeks in the in-plane ulnar approach group compared with the out-plane ulnar approach and blind injection. This improvement was still observed at 12 weeks. The flattening ratio and cross-sectional area of the median nerve showed a more significant decrease with the in-plane ulnar approach than with the out-plane ulnar approach and blind injection (P < 0.05). US-guided local steroid injection using an in-plane ulnar approach in the CTS may be more effective than out-plane or blind injection.

Conflict of interest statement

No conflicts of interest have been reported by the authors or by any individuals in control of the content of this article. We certify that no party having a direct interest in the results of the research supporting this article has or will confer a benefit on us or on any organization with which we are associated.

Figures

FIGURE 1

Transducer position and needle approach for each technique. (A) In-plane ulnar approach US-guided carpal tunnel injection, (B) out-plane US-guided carpal tunnel injection, and (C) blind injection. US = ultrasound.

FIGURE 2

Transverse sonogram of the right carpal tunnel in a patient with idiopathic CTS. A 27-gauge needle is shown passing from the ulnar aspect of the carpal tunnel to a position adjacent to the median nerve. (A) After positioning the needle tip next to the nerve, the local anesthetic-corticosteroid mixture is injected in order to peel the nerve off the overlying flexor retinaculum via hydrodissection. (B) Anechoic injectate is shown surrounding the deep surface of the median nerve and separating it via hydrodissection from the more deeply positioned hyperechoic flexor tendons and associated synovium. CTS = carpal tunnel syndrome.

FIGURE 3

Patients’ flow diagram. BCTQ = Boston Carpal Tunnel Questionnaire, CTS = carpal tunnel syndrome, EMG = electromyography, I = in-plane, O = in-plane.