Biomechanical Comparison of Volar Locked Plate Constructs Using Smooth and Threaded Locking Pegs

Abstract

The goal of this study was to determine whether there is any biomechanical difference in terms of construct strength with axial loading between volar fixed-angle locking plates with threaded locking vs smooth locking pegs. The control group comprised 7 cadaveric specimens with threaded locking pegs, and the test group comprised 7 cadaveric specimens from the same donor with smooth locking pegs. The DVR plate (Biomet, Warsaw, Indiana) was applied to the volar surface. A 15-mm dorsal wedge osteotomy was created near the level of Lister's tubercle. The radii were potted in polymethylmethacrylate for biomechanical testing. The loading protocol consisted of 3 parts: ramp loading, cyclic loading, and failure loading. The outcome measures of stiffness and failure were used to test the plates fixed with threaded and smooth locking pegs. When comparing each cycle, the difference in mean stiffness between threaded and smooth locking pegs was as follows: 122 N/mm, -9.09 N/mm, -14.7 N/mm, 49.4 N/mm, 57.4 N/mm, 71.9 N/mm, 52.3 N/mm, 35.8 N/mm. The difference in mean failure load between the threaded and smooth locking pegs was -11.3 N. There was no difference in stiffness throughout all cycles. Failure analysis showed no significant difference between the smooth (962 N) and threaded (951 N) locking pegs. The difference in stiffness between the 2 constructs (smooth minus threaded locking pegs) in ramp loading ranged from -122 to 15 N/mm. The results of this study showed no significant differences in stiffness and failure load between constructs consisting of threaded locking pegs or smooth locking pegs in the distal rows of the DVR distal radius volar locking plate. Based on the results of this study, there may be no benefit to using threaded locking pegs vs smooth locking pegs when treating distal radius fractures with a volar locking plate.