Sidebones



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Are Sidebones Significant?

The single most frequent finding in radiographs of the feet of horses is ossification of the collateral cartilages (sidebones). This ossification is significant in that it is related to the conformation of the horse's foot. It has been my experience that a horse with a good, wide foot and heel is usually not affected even by advanced ossification of the collateral cartilages.

Figure 1 illustrates rather minimal ossification of both medial and lateral collateral cartilages, which I believe is of no radiographic significance with regard to the horse's soundness. Figure 2 demonstrates somewhat more advanced ossification of the collateral cartilages. If this horse has a good, wide foot with no contracture of the heels, I would not attach any radiographic significance to this change.

Figure 1. Figure 2.
Anteroposterior radiograph of the foot demonstrating minimal ossification of the medial and lateral collateral cartilages (minimal sidebones). Anteroposterior radiograph of the foot demonstrating moderate ossification of the medial and lateral collateral cartilages with more activity noted in one of the collateral cartilages (moderate sidebones).
Figures 3 and 4 demonstrate a marked degree of ossification of one of the collateral cartilages, and the oblique radiograph (Fig. 4) shows what appears to be a fracture of this collateral cartilage. This represents the junction between a separate ossification center of the collateral cartilage and the ossification occurring from the third phalanx, rather than a fracture. With this degree of ossification of the collateral cartilages, I might be somewhat more concerned and therefore would re-evaluate the horse's foot. If this horse had a good, wide foot and were a 12 or 14 year old driving horse, then I might not attach significance to this change, especially if the horse had been performing satisfactorily.

Probably the most important feature of ossification of the collateral cartilage is as an indication of an improperly balanced foot that concentrates stresses to one side of the foot.

Figure 3. Figure 4.
Anteroposterior radiograph of the foot demonstrating advanced ossification of one of the collateral cartilages (significant ossification of a collateral cartilage). Oblique radiograph of the foot of the same horse as seen in Figure 3, demonstrating significant ossification of a collateral cartilage. In addition, there is a suggestion of a fracture of this collateral cartilage. I believe that this is not a fracture but the area of incomplete fusion between a separate ossification center and the parent portion of the collateral cartilage.