Dynamic Simulation of the Crossover Toe Deformity

INTRODUCTION: The “crossover toe deformity”, though incompletely defined, refers to an instable second metatarsophalangeal joint (MTPJ) that leads to a progressive migration of the second toe in a dorsal and medial direction [2,3]. The etiology is uncertain. One specific and controversial hypothesis states that a long second metatarsal causes abnormal loading beneath the second MTPJ during stance phase which over time causes the associated symptoms (i.e., increased plantar pressure) and observed toe migration [4]. A previous radiographic analysis study found no significant correlation between a long second metatarsal and the crossover toe deformity [4]. However, the inclusion of feet with a wide range of angular deformity may not be representative of subjects with severe changes. In the current study, we used a robotic gait simulator (RGS), cadaveric specimens and a surgical metatarsal lengthening process to further investigate this relationship. We hypothesize that increasing the length of the second metatarsal will increase plantar pressure beneath the second MTPJ, as well as cause the MTPJ angle to increase medially and dorsally in the frontal and sagittal plane respectively. Furthermore, the increased pressure on the second metatarsal head will subsequently unload the peak pressure underneath the first metatarsal.