Accurate radiological interpretation of a navicular bone requires at least a true lateromedial (LM) image, dorsoproximal-palmarodistal oblique (DPr-PaDiO) and palmaroproximal-palmarodistal oblique (PaPr-PaDIO) images. Additional information is sometimes acquired from a weightbearing dorsopalmar (DPa) image. The LM image is used to assess thickness of the palmar cortex, proximal or distal extension of the palmar cortex, demarcation between the cortex and spongiosa and the presence of periarticular osteophytes. The number, size, shape and position of radiolucent zones along the distal borders of the navicular bone are assessed in a PaPr-PaDiO image, together with the presence of central or acentric radiolucent osseous cyst-like lesions in the spongiosa, proximal or distal border entheseophytes, distal or proximal border fragments and a fracture. The PaPr-PaDiO image is used to identify radiolucent lesions in the palmar cortex and to confirm the thickness of the palmar cortex and the presence of a fracture, and to assess the trabecular architecture of the spongiosa. The presence of a bipartite or tripartite navicular bone is determined from DPr-PaDiO, PaPr-PaDiO and DPa images.
Equine Veterinary Education