actually it wasnt a "ufc" fight, but another mma event that it happened at... also, the break might heal fine or not... it depends on what may have caused the break. muay thai fighters will "condition" thier shins by beating them against trees, bags, each other, ect...
by hitting things repeatedly you create tiny hairline fractures that will build up more calcium when the bone heals, thus making it thicker and harder... this particular guy may have had unhealed fractures which actually weakened the bone since it wasnt healed yet... if it broke because of this, then it probably means that the bone was shattered, in which case, he probably wont be able to heal completely from it...
if it was a "clean" break, then he will probably recover to some extent... the kick was not executed wrong... in muay thai you use the actual shin as a weapon to strike your opponent...
i would say that it is a case of someone being able to throw a good shin kick, but not spending enough time conditioning them... he probably was hitting too many bags, and not enough actual bone conditioning.
edited to say: reguardless of why, it still is some pretty scary shit to think about happening to you
