Nonanatomic versus anatomic techniques in spring ligament reconstruction: biomechanical assessment via a finite element model

BACKGROUND: Several approaches to spring ligament reconstruction have been reported. However, a comparative study of nonanatomic and anatomic techniques with respect to biomechanical responses, such as kinematics and contact characteristics, has not been previously performed via a finite element analysis. The purpose of this study was to evaluate the biomechanical results of such spring ligament reconstructions via a finite element analysis. METHODS: A three-dimensional finite element model of the foot was developed and validated, and four reconstruction methods were simulated. The talonavicular dorsiflexion and abduction, hindfoot valgus, and contact characteristics in the Chopart joints were quantified in each model. RESULTS: Nonanatomic reconstructions corrected the talonavicular and hindfoot deformities to a greater extent than the anatomic reconstructions. The anatomic techniques also corrected the abduction and dorsiflexion deformities, although they presented insufficient power to correct for hindfoot valgus. None of the procedures restored the contact characteristics of the talonavicular and calcaneocuboid joints to those of a normal condition. CONCLUSION: Nonanatomic reconstruction of the spring ligament complex provided the greatest correction for midfoot and hindfoot misalignments in flatfoot. Severe deformities with large amounts of midfoot pronation and hindfoot valgus may be better treated with nonanatomic reconstruction methods. The spring ligament reconstruction method may mitigate the need for nonanatomic bony procedures associated with complications and allows for the preservation of the triple joint complex.