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Biomechanical Comparison of subsidence of Trapeziectomy and Suture Button Suspension plasty versus Trapeziectomy and FCR Ligamentous Reconstruction for Thumb Carpometacarpal Arthritis
Benjamin Zellner, MD; Hani Matloub, MD; Cameron Best, MD; Monica Ramirez, MD; Samita Goyal, MD; Mei Wang, PhD
Medical College of Wisconsin, Milwaukee, WI

Purpose: Central to the treatment of thumb carpometacarpal arthritis is trapeziectomy, removing the articular surface on one side of the joint. Many advocate ligamentous suspension of the thumb metacarpal using various methods. A common method, FCR autograft suspension (LRTI) and a more novel method, suspension button (SB), have both demonstrated good results to date. Our goal was to compare the subsidence and real-time motion of a suspension button and an FCR LRTI.

Methods: Six fresh frozen match pairs of human forearms were used. Open trapeziectomy was performed in all specimens. Specimens were randomly assigned to one treatment group and the contralateral limb was used for the other procedure. The capsule was closed in similar fashion. A lateral pinch model was used via cyclic pinch for 1000 cycles at 2Hz via loading of the FPL, adductor pollicis and APL tendons. Fluoroscopic measurements of the scapho-metacarpal height were taken before and after pinch simulation. In addition, a unique method of evaluation (real time motion analysis) was performed during the pinch simulation.

Results: Student t-test evaluation showed no significant difference between the groups in post scapho-metacarpal space after 1000 cycles in fluoroscopic evaluation. Pre-trapeziectomy scaphometacarpal space was not significantly different between the groups. The subsidence in the FCR group was 3.13 +/- 1.70mm and for the SB group was 2.85 +/- 2.25mm for a p value of 0.21. In flexion the subsidence of the thumb measured 2.22 +/- 1.79mm in the FCR specimens changed and 1.80 +/- 1.30mm in the suspension button specimens for a p-value of 0.32. In extension the subsidence of the thumb measured 1.47mm +/- 1.10 in the FCR specimens changed and 1.57 +/- 1.10mm in the suspension button specimens for a p-value of 0.45.

Conclusion: Biomechanical evaluation using a lateral pinch model demonstrated no significant difference in subsidence on fluoroscopy and real time motion analysis between the tightrope and suspension button groups.

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