Accuracy and Safety of Carpometacarpal Joint Injection Using Anatomical Landmarks: A Cadaver Study and Review of Literature Running title: Carpometacarpal Joint Injection Using Anatomical Landmarks

Abstract

Abstract Background: Intra-articular corticosteroid injection is one of the non-operative treatments for carpometacarpal (CMC) joint osteoarthritis that can performed with or without imaging guidance. Objective: To evaluate the effectiveness and safety of carpometacarpal joint injection regarding anatomical landmarks in a cadaveric investigation and reviewing the current literature about this issue. Materials and methods: Forty wrist specimens from 20 fresh cadavers without any gross scar or deformity in their wrists were recruited. We applied four palpation-based techniques for CMC joint injection using the anatomical snuffbox or the most proximal margin of the metacarpal in neutral or ulnar deviation position of the wrist. After intra-articular injection of methylene blue, the specimens were dissected and checked for accuracy of injection (staining of the CMC joint) and safety of the injection (staining of adjacent neurovascular structures). Results: The specimens that injections were performed at the proximal part of 1st metacarpal bone, CMC joint was stained accurately in nine specimens in neutral position and seven specimens in ulnar deviated position of the wrist. The specimens that injections were performed at the distal part of anatomical snuffbox, CMC joint was stained accurately in 8 specimens in neutral position and six specimens in ulnar deviated position of the wrist. Comparison of each methods of injection (in both wrist position) did not show significant difference (P=0.478). Also, comparison of each wrist position during injection did not show significant difference between two methods of injection (P=0.152). Neurovascular structures had not been stained after injections. Conclusion: The results reveal that CMC joint injection without imaging guidance using anatomical landmarks is a safe; however different methods of injection or wrist position did not significantly affect the accuracy of injection.