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A Biomechanical Comparison of Suture-Button Suspensionplasty and LRTI for Basilar Thumb Arthritis
Mihir J. Desai, MD1; David M. Brogan, MD2; David S. Ruch, MD3
1Vanderbilt University, Nashville, TN; 2University of Missouri, Columbia, MO; 3Duke University, Durham, NC

Introduction: The use of a suture-button (SB) suspensionplasty with trapeziectomy has been described in the treatment of basilar thumb arthritis as an alternative to the ligament reconstruction and tendon interposition (LRTI). Advocates of the suture button technique cite safety, ease of use, early mobilization, and good early results. However, it is not known how effectively the SB suspensionplasty withstands metacarpal subsidence under loaded conditions. The purpose of this study was to compare the initial strength of the LRTI procedure to SB suspensionplasty in preventing first metacarpal subsidence in a cadaveric model.
Methods: We used eight matched pairs of below-elbow cadaveric arms for this study. Each specimen was randomly assigned to either receive a trapeziectomy and LRTI (LRTI Group) or trapeziectomy and SB suspensionplasty (SB Group). Using previously described and validated testing protocols; physiological key pinch was simulated in each specimen. We then incrementally loaded only the thumb metacarpal from 5 to 20 pounds, using 5-pound increments. Metacarpal subsidence during physiological key pinch and incremental loading was determined using radiographic measurements of trapezial space height.
Results: The pre-loading trapezial space height did not differ significantly between the SB (11.9 mm) and LRTI group (13.7 mm, p =0.4). Metacarpal subsidence was evident at all testing loads in each group. After simulated physiological key pinch, the SB group had significantly greater trapezial space height compared to the LRTI group (8.0 mm vs. 5.5 mm, p <0.05). For each incremental metacarpal load from 5 to 20 pounds, the SB group had significantly greater trapezial space height than the LRTI group. Figure 1 demonstrates the decrease in trapezial height as a percent of the initial post-operative value for the SB and LRTI groups.
Conclusion: SB suspensionplasty is biomechanically superior in resisting metacarpal subsidence compared to LRTI in a cadaveric model following trapeziectomy.

Figure 1: Comparison of average change in trapezial space height between the LRTI and SB group after simulated pinch and incrementally increasing axial loads to the first metacarpal. (Higher percentage indicates a greater loss of trapezial space height and collapse of the first ray).

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