I had two cows that I dealt with sand cracks on. Both cows had really fast growing hooves.( shouldn't be from lack of circulation) Both had shown signs of lameness when the hoof needed trimming. By trimming and nipping the toe back will cause the foot to break over faster without putting as much pressure on the outer wall. Their is a noticeable improvement right away. While I'm at it I squirt a little topical fungicide in the crack. Copper or Zinc sulfate works. Just my two cents, for what it's worth.
Rod