Validation of the use of radiographic bone aluminum equivalence to measure bone mineral content in the equine coffin bone

Abstract

Musculoskeletal injuries are the most common cause of lost training days in the athletic horse. Catastrophic bone failure is the most devastating of these injuries, and is a leading reason for racetrack euthanasia. As a result, interventions focusing on increasing bone quality in the equine athlete are the subject of much research. Techniques for non-invasive and economical measurement of bone health are lacking. One such technique involves the use of digital radiography, where optical density from the radiograph is compared to that of a known density of aluminum. This technique, known as radiographic bone aluminum equivalence (RBAE), has been used to measure bone mineral density (BMD) in the equine third metatarsal (cannon bone). However, this technique so far has been limited to only the cannon bone and, therefore, is in need of validation, in terms of reliability and repeatability, for other locations. This study began the validation of the use of Radiographic Bone Aluminum Equivalence (RBAE) on the equine coffin bone, as a non-invasive estimate of BMD. The first objective was simply to determine repeatability. To evaluate bone density in the equine coffin bone (distal phalanges), digital radiographs were taken of equine coffin bones from at least 20 cadaver limbs. The dorsal and palmer locations on the bone were chosen to determine RBAE according to previously published techniques. Each location was analyzed independently two times to determine the coefficient of variation of the technique, as well as the relationship between the two locations. As a follow-up to this project, the coffin bones then will be harvested from the limb and subjected to ashing to ascertain the actual bone mineral content. This value from ashing will be correlated to the RBAE values in this study to determine the accuracy of the RBAE technique and help identify the most accurate measurement location. This project provides an initial step into expanding our technique for non-invasive measurement of bone quality in the equine athlete.