There are basically two types of rare medical operations. Type one are well known operations but very hard to perform, such as brain or spine surgeries. it requires professional physicians with many years of experience in that field, otherwise the risk of performing such surgeries will be very high.
Second types of rare operations are the ones that need to be done by an advanced method or using a specific medical equipment. Since, there are different treatment options for one disease, some of them can be performed through the best way but only certain individuals who are pioneer in that method are able to do that.