GROSS, HISTOLOGICAL, AND MICROVASCULAR ANATOMY AND BIOMECHANICAL TESTING OF THE SPRING LIGAMENT COMPLEX

In recent years there has been an increased interest in the treatment of acquired pes planus, The breakdown of the medial longitudinal arch is most often seen at the talonaviculocalcaneal articulation. This sug gests a relationship between the ligamentous complex at this articulat ion and acquired pes planus. This study was undertaken to gain a bette r understanding of the gross, histologic, and microvascular anatomy, a s well as the biomechanics of the ligamentous structures surrounding t he talonaviculocalcaneal articulation. Cadaver dissections of 38 fresh -frozen feet were performed. Detailed descriptions of the gross anatom y of the superomedial calcaneonavicular ligament, inferior calcaneonav icular ligament, and the superficial deltoid ligament were recorded. T heir relationships to the posterior tibialis tendon and to the bones o f the talonaviculocalcaneal articulation are described. The histology and microvascularity of these structures were also studied. Preliminar y biomechanical testing was performed. It was found there are two defi nitive anatomic structures that are commonly called the spring ligamen t: the superomedial calcaneonavicular ligament (SMCN) and the inferior calcaneonavicular ligament (ICN). The SMCN ligament was found to have histologic properties that suggest significant load bearing. The hist ology of the ICN ligament suggests a pure tensile load function. The d eltoid ligament and the posterior tibialis tendon had direct attachmen ts to the SMCN ligament in all specimens, An articular facet composed of fibrocartilage was found in each SMCN ligament specimen. The microv ascular structures showed an avascular articular facet present in the ligament. The biomechanical testing showed that the SMCN ligament and ICN ligament had strength similar to ankle ligaments. This study sugge sts this ''spring ligament complex'' has more of a ''sling'' function for the talar head, It is hoped that the better understanding of this region will add to our understanding of the etiology of pes planus and possible treatment alternatives.