Biomechanical analysis of a magnesium plantar plate prototype system for the first tarsometatarsal joint fusion: a cadaveric study

Abstract Background Titanium plantar plates have proven successful in the fixation of the first tarsometatarsal arthrodesis (TMT). However, a second surgery is typically needed for implant removal, and potential adverse effects, carried by the conventional implantations, are not uncommon. The purpose of this study was to determine whether a novel magnesium-based plantar plate system provides similar fusion stability to a titanium-based plantar plate system under various loading conditions. Methods Six matched-pair human cadaveric specimens underwent TMT fusions using either a magnesium plantar plate system prototype or a titanium plantar plate system. Specimens were cyclically loaded with a force ranging from 5 N to 50 N for 5,000 cycles, and displacement was recorded. Axial stiffness (N/mm) was calculated from load-displacement curves. Each specimen was loaded to failure at a rate of 5 mm/min, and the ultimate load was recorded. Results No significant difference was found in the vertical displacement between Ti group and Mg group after 100 cycles (2.4 ± 1.0 mm vs. 1.3 ± 1.4 mm, p = 0.196), 500 cycles (3.3 ± 1.3 mm vs. 1.7 ± 1.7 mm, p = 0.142), 1,000 cycles (3.7 ± 1.5 mm vs. 1.9 ± 1.9 mm, p = 0.128), 2,500 cycles (4.2 ± 1.7 mm vs. 2.3 ± 2.2 mm, p = 0.172) and 5,000 cycles (4.5 ± 1.8 mm vs. 2.3 ± 3.3 mm, p = 0.125), Additionally, no significant differences were observed in initial stiffness (53.1 ± 19.2 N/mm vs. 82.2 ± 53.9 N/mm, p = 0.257), final stiffness (90.6 ± 48.9 N/mm vs. 120.0 ± 48.3 N/mm, p = 0.319), or maximum load-to-failure (259.8 ± 98.2 N vs. 323.9 ± 134.9 N, p = 0.369). Conclusions Based on the performed biomechanical testing, the magnesium plantar plate system provides mechanical stability equivalent to the titanium plantar plate system in fixation for the first TMT joint fusion.