r (DB) is yet another soft-tissue parameter that Dr. Redden measures as part of his radiographic protocol. It is easily measured on a true lateral radiograph taken with soft tissue detail. This particular measurement is important because digital breakover directly effects the tension on the deep digital flexor tendon, and subsequently the laminae, sole corium, navicular bone, navicular bursa and surrounding ligaments.
Follow these steps to accurately measure digital breakover:
Locate the apex (tip) of PIII and draw a vertical line to the ground surface.
Locate where the horse's toe or the shoe no longer touches the ground.
Measure the horizontal distance between these two points in millimeters.
In this case, the digital breakover measures 16mm.
If the breakover is behind the apex of PIII, then it is referred to as a negative digital breakover.