Intrasynovial Digital Anesthesia in Trigger Finger

Overview

Trigger finger is a common disease of the hand involving swelling and inflammation of the tendon which flexes a finger, causing catching, locking, and/or pain. Trigger finger is typically treated by hand surgeons with a steroid injection through the front/palm side of the hand into the area near the tendon (i.e., at the base of the affected finger). This steroid injection is often combined with a local anesthetic (numbing agent) to help reduce short-term pain from the injection. However, the front/palm side of the hand is known to be very sensitive, and the steroid injection can be quite painful as the needle pierces the front/palm skin. To reduce the pain of steroid injections for trigger finger, a different approach involves performing the injection from the back/dorsal side of the hand, which is thought to be less sensitive (and therefore less painful) than the front/palm side of the hand. This technique is sometimes used and has been previously studied, but it is not clear if it can offer less injection-related pain than standard treatment. Accordingly, this study will be comparing short-term injection-associated pain between front/palm side and back/dorsal side steroid injections for trigger finger. The study will also seek to understand what area of the hand is numbed by the anesthetic when doing a front/palm side injection versus a back/dorsal side injection of the hand. Overall, the investigators hypothesize that back/dorsal side injections will be less painful than front/palm side injections for trigger fingers and that the area of numbing from the anesthetic will be equivalent between both types of injections.

Trigger finger (stenosing tenosynovitis) is one of the most common pathologies assessed by hand surgeons in clinic. Trigger finger involves inflammation or edema of the flexor tendon causing friction of the tendon at the site of the A1 annular pulley located at the base of the affected finger in the palm. Trigger finger is typically managed non-surgically in a clinic setting with percutaneous corticosteroid injection (CSI) which can be successful in alleviating symptoms. Patients with trigger finger who do not respond to CSI, have incomplete relief, and/or who have recurrent symptoms may then receive surgical management with release of the A1 pulley. CSIs for trigger fingers are among the most common procedures performed by hand surgeons and are often administered multiple times in a single clinic day. CSIs are frequently mixed 50:50 with 1% lidocaine to provide post-injection analgesia for patients as well as symptomatic relief of the trigger finger if acutely inflamed. These injections are commonly administered from a palmar approach into the A1 pulley of the affected digit. Numerous technical variations of palmar trigger finger injections have been described involving either subcutaneous injection superficial to the flexor tendon sheath or intrasynovial (transthecal) injection into the flexor tendon sheath. Unfortunately, given the rich sensory innervation of the palmar skin, palmar injections are associated with significant pain as the needle pierces the skin. An alternative technique is to provide digital anesthesia from a dorsal webspace approach, injecting the local anesthetic into the flexor tendon synovial sheath. This intrasynovial or transthecal technique has the benefit of a dorsal approach where the skin is less sensitive resulting in less pain (6). This technique has been described previously but is not familiar to many hand surgeons and is not routinely used in North America. Anecdotally, patients report significantly decreased pain with the dorsal intrasynovial injection technique for trigger finger injections, but pain scores have not been quantitatively evaluated or compared to the pain scores of traditional palmar trigger finger injections. Furthermore, it is not known what distribution of digital sensory blockade is achieved with this intrasynovial technique, particularly on the dorsal surface of the digit which is discontinuous with the flexor tendon sheath and innervated by the sensory branch of the radial nerve. Accordingly, it is hypothesized that injecting corticosteroids into the synovial sheath of the flexor tendon will result in less pain over 24 hours if performed through the dorsal webspace versus the palmar side of the affected digit.