Extraosseous Talotarsal Stabilization Devices: A New Classification System

Displacement of the articular facets of talus on the tarsal mechanism, or partial talotarsal dislocation, is a condition seen in children, adult, and geriatric populations. A characteristic of this pathologic condition is a prolonged period of and excessive amount of pronation (hyperpronation) on weightbearing. The ill effects of this condition may lead to a multitude of other foot pathologies and to pathologies associated with the proximal lower extremity musculoskeletal structures. A variety of conservative and operative treatment options have been used to eliminate or minimize hyperpronation. Extraosseous talotarsal stabilization (EOTTS) devices have been used to realign and stabilize the articular facets of the talus on the tarsal mechanism, thereby attempting to restore the normal range of hindfoot motion while eliminating hyperpronation. A multitude of such devices, which are intended for the same purpose, are available for the surgeon to choose from. However, there is no literature discussing the differences among these devices, or the benefits of one device over the other. Based on current understanding and available knowledge base, the goal of this article was to classify EOTTS devices based on their design features and biomechanical functioning. A theoretical description of how these different types of devices function is laid out in an attempt to understand the reason for their success or failure. This new classification system is intended to help researchers and surgeons appreciate the subtle yet important differences among these devices, and to thus help them design future research studies when using these devices.