"niyao" meaning strong-armer?
I think it is mistyped. There is something called "医闹" (yinao), which inherently means affrays in hospitals made by some troublesome patients because of medical disputes.

However, the situation was, some patients hired some "agency" to make all the affrays for them. Before 2011, it was quite common, and those people get hired are called "职业医闹" (zhi ye yi nao). The payment is 100 Yuan per day.

In recent years, as most of the 职业医闹 get caught into prison, much fewer reports of that events are heard, but "医闹" still exists, though most of the events didn't cause very serious consequences. But recently, a patient killed a doctor in Zhejiang, which is an open book.