Flexor Pollicis Longus Tendon Wear Associated With Volar Plating: A Cadaveric Study

Abstract

This study examined the effect of low-profile volar rim plates (VR), proximally placed standard variable-angle locking plates (pVA-LCP), and distally placed standard variable-angle locking plates (dVA-LCP) on the flexor pollicis longus (FPL) tendon in a cadaver model. We hypothesized that tendons from the VR and pVA-LCP groups would exhibit similar contact pressures, wear patterns, and post-fatigue testing mechanical properties, whereas dVA-LCP tendons would exhibit higher contact pressures, increased tendon wear patterns, and decreased mechanical properties. Nine matched pairs of cadaveric specimens were used in this study. Thin-film pressure sensors were used to measure the initial contact loads between plates and FPL tendons. Specimens were cyclically loaded for 10,000 cycles by actuating the FPL tendon. Cycled tendons were harvested, photographed with a stereomicroscope, and graded for wear on a Likert scale by 5 observers who were blinded to the study protocol. Uniaxial tensile testing measured mechanical properties of the tendon: ultimate failure load, ultimate stress, percent stress relaxation, elastic modulus, and stiffness. With regard to the cadaveric FPL tendon, VR and dVA-LCP had increased contact pressure and tendon wear compared with pVA-LCP. There were no significant differences in contact pressure or tendon wear between dVA-LCP and VR. There was no major difference in the tested mechanical properties of the FPL tendon among any of the groups. Plates placed directly on or beyond the volar rim demonstrate increased contact pressures and increased tendon wear in a cadaveric model. Although low-profile plates allow for fixation of smaller volar fragments in the distal radius, they cause substantial contact with the FPL tendon, which may rupture if the plate is not removed.