Innervation of thumb carpometacarpal joint: implications for diagnostic block and denervation procedures.

Introduction: Osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint is a common disorder that negatively impacts hand function. Denervation of the thumb CMC joint has emerged as a viable treatment option. However, the innervation pattern of the thumb CMC joint is controversial. Therefore, the objective of this study was to identify the articular branches supplying the thumb CMC joint and to document their relationship to anatomical landmarks to provide the foundation for image-guided diagnostic block and denervation procedures.

Methods: In 10 formalin-embalmed upper limb specimens articular branches supplying the thumb CMC joint were dissected from their origin to termination. A frequency map documenting the number of articular branches was generated. The frequency map enabled visualization and comparison of the relative area of innervation of the thumb CMC joint by each articular branch.

Results: The thumb CMC joint received innervation from six nerves. These were the deep branch of ulnar nerve (DBUN), dorsal articular nerve (DAN) of the first interosseus space, thenar branch of median nerve (TBMN), palmar cutaneous branch of median nerve (PCBMN), lateral antebrachial cutaneous nerve (LACN) and superficial branch of the radial nerve (SBRN) and/or their branches. Each nerve was found to innervate different aspects of the joint. The DBUN and DAN were found to innervate the posteromedial aspect of the thumb CMC joint, the TBMN and PCBMN anterior/anteromedial aspects, LACN posterolateral/lateral/anterior aspects and SBRN posterolateral/anterolateral aspects.

Conclusions: The thumb CMC joint was innervated by articular branches originating from the SBRN, DAN, LACN, PCBMN, TBMN and DBUN. The documented anatomical relationships provide the foundation to inform selective diagnostic block and denervation of the thumb CMC joint. Further investigations are needed to assess the clinical implications of the current study.