Radiographic Analysis of Simulated First Dorsal Interosseous and Opponens Pollicis Loading Upon Thumb CMC Joint Subluxation: A Cadaver Study

Julie E. Adams, Virginia O’Brien, Erik Magnusson, Benjamin Rosenstein, David J. Nuckley

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Background: Therapy programs to treat thumb carpometacarpal (CMC) arthritis may engage selective activation and reeducation of thenar muscles, particularly the first dorsal interosseous (FDI) and opponens pollicis (OP) to reduce subluxation of the joint. We describe the effect of simulated selective activation of the FDI and OP muscles upon radiographic subluxation of the thumb CMC joint. Methods: In a cadaver model of CMC subluxation, loads were applied to the FDI, the OP, and then concomitantly at 0%, 25%, 50%, 75%, and 100% maximal loads and radial subluxation of the joint and reduction in subluxation was measured. Results: Selective activation of the OP, alone, improved the subluxation ratio (SR) in a dose-dependent manner. Selective activation of FDI, alone, demonstrated minimal effects on SR. Concomitant activation of OP and FDI improved the SR across all loading states, and activation of 75% and greater, when compared with FDI activation alone, resulted in a statistically significant improvement in SR to within 10% of the presubluxed joint. Conclusions: Concomitant activation of the FDI and OP acts to reduce subluxation of the thumb CMC joint in a dose-dependent fashion. The OP is likely the predominant reducing force. Hand therapy programs that focus on selective strengthening programs likely function in part to encourage patients to activate the easily palpable and easily understood FDI. Concomitant coactivation of the OP may be the major reducing force to elicit clinical and radiographic reduction of subluxation, improved thumb positioning, and reduction of pain and arthritic symptoms.

    Original languageEnglish (US)
    Pages (from-to)40-44
    Number of pages5
    JournalHand
    Volume13
    Issue number1
    DOIs
    StatePublished - Jan 1 2018

    Bibliographical note

    Funding Information:
    The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by a grant from the Minnesota Medical Foundation.

    Publisher Copyright:
    © 2017, © The Author(s) 2017.

    Keywords

    • carpometacarpal
    • CMC
    • dynamic stability
    • first dorsal interosseous
    • opponens pollicis
    • selective strengthening
    • trapeziometacarpal

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