Radiographic method for evaluation of tarsus morphometry

Abstract

The equine tarsus is the most common area of the hind limb associated with lameness. Tarsal function is probably directly related to its conformation. Previous conformational measurement methods and radiological data are either limited or too specific to explain the complex tarsus conformation in different loading conditions. This study aimed to develop a consistent method to evaluate equine tarsal conformation from lateromedial radiographs. Twenty cadaveric hind limbs from 15 adult horses of different breeds were cut at the distal one third of the tibia. Hind limbs mounted in a loading rig and positioned with the metatarsus vertical were digitally radiographed. The zero-degree lateromedial (ZLM) was defined by vertical and horizontal landmarks including overlapping of the lateral and medial trochlea of the talus and a contact point between the dorsal edges of lateral and medial borders of the distal central tarsal bone. Radiographs missing these features were retaken to achieve consistent ZLM views. Specific radiographic features were selected as landmarks to develop tarsal parameters based on their clarity and their being consistently identifiable. The intra-rater repeatability of ten measurable morphometric parameters was evaluated with each radiograph measured twice with an interval of at least one month and Bland-Altman plots developed from this data. Repeat measurements did not differ significantly (Intraclass correlation coefficients (ICC) ranged from 0.731-0.966). This study provides a base for evaluation of the tarsal conformation by radiography.