Corey McGee1, Virginia O'Brien2, Sara Van Nortwick3, Julie Adams4, Ann Van Heest3. 1. University of Minnesota, Program in Occupational Therapy, 300 University Square, 111 South Broadway, Rochester, MN 55904, USA. Electronic address: mcge0062@umn.edu. 2. University Orthopaedics Therapy Center, Fairview, 2450 Riverside Ave., Suite R102, Minneapolis, MN 55454, USA. 3. University of Minnesota, Department of Orthopaedic Surgery, 2450 Riverside Ave. South, Suite 200, Minneapolis, MN 55454, USA. 4. Mayo Clinic, Department of Orthopedic Surgery, 200 First St. SW, Rochester, MN 55905, USA.
Abstract
INTRODUCTION: Hand therapists selectively strengthen the first dorsal interosseus (FDI) to stabilize arthritic joints yet the role of the FDI has not yet been radiographically validated. PURPOSE: To determine if FDI contraction reduces radial subluxation (RS) of the thumb metacarpal (MC). METHODS: Fluoroscopy was used to obtain true anterior-posterior radiographs of non-arthritic CMC joints: 1) at rest, 2) while stressed and 3) while stressed with maximal FDI contraction. Maximal FDI strength during CMC stress and thumb MC RS and trapezial articular width were measured. The ratio of RS to the articular width was calculated. RESULTS: Seventeen participants (5 male, 12 female) participated. Subluxation of a stressed CMC significantly reduced and the subluxation to articular width ratio significantly improved after FDI activation. CONCLUSIONS: Contraction of the FDI appears to radiographically reduce subluxation of the healthy thumb CMC joint. Further exploration on the FDI's reducibility and its carry-over effects in arthritic thumbs is needed. LEVEL OF EVIDENCE: 4.
INTRODUCTION: Hand therapists selectively strengthen the first dorsal interosseus (FDI) to stabilize arthritic joints yet the role of the FDI has not yet been radiographically validated. PURPOSE: To determine if FDI contraction reduces radial subluxation (RS) of the thumb metacarpal (MC). METHODS: Fluoroscopy was used to obtain true anterior-posterior radiographs of non-arthritic CMC joints: 1) at rest, 2) while stressed and 3) while stressed with maximal FDI contraction. Maximal FDI strength during CMC stress and thumb MC RS and trapezial articular width were measured. The ratio of RS to the articular width was calculated. RESULTS: Seventeen participants (5 male, 12 female) participated. Subluxation of a stressed CMC significantly reduced and the subluxation to articular width ratio significantly improved after FDI activation. CONCLUSIONS: Contraction of the FDI appears to radiographically reduce subluxation of the healthy thumb CMC joint. Further exploration on the FDI's reducibility and its carry-over effects in arthritic thumbs is needed. LEVEL OF EVIDENCE: 4.