SMITH AJ, FELSTEAD CW, LAWSON JS, et al.
Radiography is the most commonly applied imaging modality in equine practice and forms an essential part of the diagnostic work-up of lame horses. Radiographic signs of musculoskeletal pathology are frequently localized at sites of soft tissue attachment, which are often not clearly visible on radiographs. Different lesions carry different prognoses and require a variety of treatments, and a good knowledge of the position of the synovial structures in the distal limb of the horse is essential for practitioners in the interpretation of radiographs. This study describes a new technique for creating three-dimensional (3D) models of the synovial structures and superimposing them onto radiographs for the purpose of teaching radiographic anatomy. A set of standard radiographs was acquired of the metacarpophalangeal and the distal interphalangeal joints of a fresh cadaver leg while the leg was positioned in a material-testing machine to mimic the weight-bearing horse. Computed tomography of the same regions was performed after injection of negative contrast medium into the joints. 3D reconstructions of the joints were created using grayscale thresholding and polynomial surface meshing in Mimics. The resulting 3D reconstructions were superimposed on top of the radiographs using Adobe© Photoshop© CS3 Extended, thus allowing the visualization of the joint anatomy in relation to the bone on all projections. The main advantage of this technique is that it allows synovial structures to be visualized on radiographs where they are normally indistinct, which will serve as a teaching aid for anatomy.