Now are about 0 anyways, so he should market the bejeebers out of the people he was already treating...let all the parents know he is leaving and why so they can seek him out for the care of any future children since they are likely tied to him more than the office for their Ortho care. Maybe even be willing to accept them as "transfer" patients and resume whatever financial arrangements they already had (if he has all that info on them).

If he does have a non-compete, he can't take them as transfer pts if they fall within the limitations of the contract. But he could still treat any future siblings/friends/etc.

I was in shoes similar to his once. Getting out was the best move I made in hindsight.