The point of breakover is defined as that portion of the hoof last in contact with the ground during the terminal stance phase of a limb. Shortening the point of breakover essentially involves shortening the toe whilst maintaining a correct hoof pastern axis. This practice is encouraged by some veterinarians and farriers in order to hasten breakover speed and reduce the time the toe is in contact with the ground. This reduces tension on the deep digital flexor tendon and may therefor aid in the prevention of future lameness problems involving the lower limb. The aim is to keep the toe as short as possible within normal limits. Acute hoof angle i.e. long toes, prolongs hoof breakover time and increases strain on the soft tissues at the back of the leg namely the deep digital flexor tendon as well as the navicular bone.
The aim of this study was to quantify differences in stride kinematics (commonly referred to as gait quality e.g. range of motion, stride length, knee angle, hoof height, swing:stance ratio, etc) resulting from incremental shortening of the point of breakover.
Horses were fitted with aluminium plates adhered to their front hooves which were drilled and tapped to allow additional aluminium plates of varying lengths to be attached. The horses were then videoed at the walk and the trot to determine differences in gait quality attributable to differences in point of breakover.
Results of this study show significant changes in stride kinematics are caused by shortening the point of breakover. Retraction of the forelimbs was greatest when breakover was moved 1.27 cm back from the toe. The greater the retraction of the forelimb the more it sits under the body of the horse during the stance phase and this corresponds to better gait quality. Also, the minimum height of the fetlock at the trot was higher where the breakover point was shortened. At both the walk and the trot there was a higher swing:stance ratio (more cadence) when the shoe was placed 2.54cm caudal to the toe. However there does seem to be a limit to which the point of breakover can be shortened and still maintain gait quality and comfort for the horse.
No difference were noted between long toed and normal toed horses with regards to stride length, suspension, or flight arc of the hoof. This study showed there was no difference in breakover speed at the trot between rocker-toed shoes and flat shoes.
How is this useful:
Maintaining short toes and appropriate heel toe alignment is important for protecting lower limb structures and also has the added benefit of improving gait quality. However, if toe breakover is shortened too much then it can have a negative impact not only on stride kinematics (gait quality) but also on horse comfort. Maintaining short toes is a function of regular and diligent farriery.