Navicular Bone



Proliferative Changes

Also important is the proliferative or productive bone change, most frequently seen along the wings of the navicular bone. Initially, the normally rounded wing of the navicular bone begins to develop a pointed appearance. It looks like the bow of a canoe and becomes more and more sharply delineated. Subsequently, bone spurs begin to form on the wing and often become quite large.

Formation of bone spurs can progress independent of the osteolytic changes in the navicular bone. It is unusual, however, for bone spurs to form without lollipop destructive lesions along the distal border of the navicular bone. The reverse is not true. It is not at all unusual to see lollipop destructive lesions along the distal border of the navicular bone without formation of bone spurs on the wings. It is therefore necessary to evaluate all areas of the navicular bone, and this can be done only if all radiographic views (dorsoventral, anteroposterior and lateral) are obtained.

The second type of degenerative change described consists of proliferative changes along the wings of the navicular bone, which are called bone spur formations (Figs. 33 to 39). All views of the navicular bone are necessary to permit evaluation of the presence and extent of bone spur formation.

Figure 33. Figure 34.
Dorsoventral radiograph of the foot demonstrating spur formation on the wing of the navicular bone, resulting in the appearance of the bow of a canoe. Anteroposterior radiograph of the foot demonstrating an early bone spur along the wing of the navicular bone.


Figure 35. Figure 36.
Dorsoventral radiograph of the foot demonstrating a bone spur along the wing of the navicular bone. Lateral radiograph of the foot demonstrating a bone spur involving the wing of the navicular bone.


Figure 37. Anteroposterior radiograph of the foot demonstrating a bone spur along the wing of the navicular bone.

Figure 38 illustrates the spatial relationship of bone spurs along the wing of the navicular bone to the ossified collateral cartilage. Figure 39 depicts rather pronounced formation of bone spurs along the wings of the navicular bone, however, there is also a separate ossification center or an old fracture of the navicular bone. Even though the horse may be currently sound, any evidence of a separate ossification center or fracture of the navicular bone can be considered radiographically significant. I have seen only a few sound, competitive horses (usually 5 years of age or less) that perform with this type of bone defect. However, when one is dealing with a great number of horses, the prognosis for future soundness must be uniformly poor.
Figure 38. Figure 39.
Anteroposterior radiograph of the foot demonstrating significant ossification of the collateral cartilage with a bone spur along the wing of the navicular bone. There are degenerative changes present involving the proximal interphalangeal articulation. Anteroposterior radiograph of the foot demonstrating an old fracture or separate ossification center of the navicular bone with bone spur formation involving the wings of the navicular bone.