University of Pennsylvania. New Bolton Center

If pressed to pinpoint a single Achilles heel in the racehorse, it's probably a fair bet to assume many would zero in on the fetlock--the intricate joint mechanism that in a racehorse travelling at top speed proves especially vulnerable to system failure. Indeed, 19 of the 22 horses that suffered catastrophic musculoskeletal injuries at Santa Anita during its benighted winter-spring meet nearly two years ago had sesamoid fractures. In most cases, the prognosis for horses who suffer severe fetlock breakdowns is grim, but a procedure pioneered at the end of...