Coupled experimental–computational study of Lapidus plates for the high-performance of surgical techniques for hallux hypermobility correction

BACKGROUND: For the correction of Hallux hypermobility through surgery, Lapidus plates have been studied as surgical fixation devices to evaluate the procedure's success and its implications for biomechanical foot performance. However, significant knowledge gaps persist regarding the behavior of these devices and their biomechanical characteristics following implantation. METHODS: This work studies two types of Lapidus plates through a coupled experimental-computational analysis. The first is a plantar fixation device, and the second is a helical device; both are used as fixation tools in Cuneometatarsal Arthrodesis. For this, mechanical tests specifically compression and fatigue are conducted with specimens of cadaveric feet implanted in the first cuneometatarsal joint (FCMJ) with each of the Lapidus plates. To the knowledge of this research team, for the first time reported in literature, complete foot specimens are used for the experimental tests. At the same time, numerical foot models have been developed to generate numerical data validated against experimental results. This approach enables the identification of additional structural information, through numerical methods, which is then complemented by electron microscopy analyses of the plates after experimental testing. RESULTS: The highest micro-deformation was found in the first metatarsal of the foot with a helical plate ([Formula: see text] mm/mm) and in the fifth metatarsal of the foot with a plantar plate ([Formula: see text] mm/mm). Both numerical and experimental analyses agreed within 98%. A correction of Hallux hypermobility up to 82.28% was achieved with the Lapidus arthrodesis, and bone failure was recorded at forces of 425 N and 275 N at the helical and plantar insertions, respectively. CONCLUSIONS: The results suggest that the Lapidus plate's helical configuration is superior, both structurally and functionally, to the plantar-only configuration, indicating that multi-planar fixation provides better mechanical stability than single-plane plantar fixation.