The Diagnostic Utility of Midcarpal Anesthetic Injection in the Evaluation of Chronic Wrist Pain

Abstract

The evaluation of chronic wrist pain can be a diagnostic dilemma. Lidocaine injections combined with corticosteroids are often used for both diagnosis and therapy. The purpose of this study was to determine if a midcarpal injection of lidocaine could serve as a diagnostic tool in patients with chronic wrist pain. Specifically, the relationship of pain relief from the injection and improvement of grip strength were compared to the presence of intracarpal pathology as confirmed by wrist arthroscopy. Forty-five patients with chronic wrist pain underwent a midcarpal injection of lidocaine with or without corticosteroids. Forty of the 45 underwent comcomitant steroid injections; a majority of the 40 patients reported relief of pain for two or more weeks. Improvement of pain and improvement of grip strength were determined. Each of these patients subsequently underwent a radiocarpal and midcarpal arthroscopy, and the pathologic findings of arthroscopy were compared to the improvement of pain and grip strength. These data were compared to a cohort of six volunteers without history of wrist pain or trauma that underwent midcarpal injection of lidocaine. Statistical analysis was performed using Reciever-Operator-Characteristic analysis. The average age of patients with chronic pain was 30.3 years, with an average of 9.8 months of wrist pain. The ultimate diagnoses included 35 patients with carpal instability dissociative, two with nondissociative instability, seven with complex instability of the carpus, three with extensor carpi ulnaris tendonitis and one with deQuervain's tenosynovitis. After lidocaine injection, the normal cohort had a mean loss of 2 kg (-5.3%) (p=0.02) in grip strength, whereas the experimental cohort had a mean improvement in grip strength of 5.73 kg (34.4%). Improvement of pain after injection did not correlate with pathologic arthroscopic findings (p=0.92). Improvement in grip strength after midcarpal lidocaine injection of 6 kg or 28% had a 73% sensitivity and a 70% specificity (p=0.02) of having intracarpal pathology at the time of arthroscopy. Of the chronic wrist pain patients, only four had a normal arthroscopy, and the remainder had at least one area of significant pathology attributing to their pain. We conclude that a midcarpal injection of lidocaine can serve as an effective diagnostic tool in the evaluation of the patient with chronic wrist pain. Improvement of grip of 28% with or without relief of pain is highly correlated with intracarpal pathology.