Ultrasound Morphometry and Mean Echogenicity of Digital Flexor Tendons, Suspensory Ligament, and Accessory Ligament of Digital Deep Flexor Tendon in Gaited Horses

SIMPLE SUMMARY: Breed variations related to the tendon and ligament dimensions of the palmar metacarpal region have been described in horses; however, they have not been demonstrated in gaited horses or between the fore- and hindlimbs. In this study, we evaluate and compare the sonographic characteristics of the digital flexor tendons and ligaments of the palmar/plantar of the metacarpal and metatarsal regions in gaited horses and also establish normal reference ultrasound values for Mangalarga Marchador and Campeiro horses. Thus, the values presented in this paper can be used as a reference for the ultrasound evaluation of the digital flexor tendons and ligaments in the limbs of horses of these breeds. ABSTRACT: The objective of this study was to evaluate and compare the sonographic characteristics of the digital flexor tendons and ligaments of the palmar/plantar of the metacarpal and metatarsal regions in gaited horses, as well as to establish normal reference ultrasound values for Mangalarga Marchador (MM) and Campeiro breeds. Transverse sonographic images were obtained of 50 adult and healthy horses from the MM (n = 25) and Campeiro (n = 25) breeds. The images were taken in six metacarpal/metatarsal zones, and the following measurements were taken: transverse area, circumference, dorsopalmar/plantar length, lateromedial length, and mean echogenicity. Differences were observed between breeds in the fore- and hindlimbs, and, even when not significant, the Campeiro breed tended to have higher values for most variables and structures. Variations between zones and between structures in the same zone followed a similar trend in both breeds for all variables. In addition, the dimensions and variations between zones and structures were different between the fore- and hindlimbs, highlighting the need for specific values for the digital flexor tendons and ligaments of the metatarsal plantar region. In conclusion, the digital flexor tendons, suspensory ligaments, and accessory ligaments of the digital deep flexor tendon are influenced by the breed factor in gaited horses, and they are different between the fore- and hindlimbs.