Sonographically Guided Flexor Hallucis Longus Tendon Sheath Injection

Abstract

The purpose of this study was to describe a sonographically guided technique to perform flexor hallucis longus (FHL) tendon sheath injections. Scans were performed with an intermediate-frequency (7.5- to 12-MHz) linear transducer with the scan plane corresponding to the anatomic axial plane and the patients positioned prone. The transducer was placed along the posteromedial ankle with the needle entry point being lateral to the Achilles tendon. A 25-gauge, 1.5-in needle or a 22-gauge spinal needle was positioned directly into the tendon sheath during real-time visualization with injection of a standardized therapeutic mixture (anesthetic and long-acting corticosteroid) at the level of the posterior sulcus for the FHL. Distention of the tendon sheath during real-time visualization was considered a successful injection. Twenty-four injections in 20 patients (12 female and 8 male; age range, 22-64 years) were performed with this technique. In each case, distention of the FHL tendon sheath was obtained as the desired end point. Apart from minor paresthesias from local anesthesia, no long-term complications from these injections have occurred to date. We describe a method to perform sonographically guided injections of the FHL tendon sheath. Sonography provides several distinct advantages as a method to provide guidance for delivery of therapeutic injections. The most important of these is the ability to visualize the needle and make adjustments in real time to ensure that medication is delivered to the appropriate location. Given these advantages, we propose that sonographic guidance provides an excellent alternative in the administration of corticosteroids to the FHL tendon sheath.