Each surgeon has his or her own patient criteria for the new minimally invasive surgery for joint replacement. This is common practice when a new approach is being used. It's better to hand pick patients who are "safe" and most likely to have a good result.
Right now patients are chosen on the basis of weight first. Overweight or obese patients don't qualify for the new method. A previous surgery on that joint may also disqualify you.
Major arthritic changes or damages from any disease to the joint might require the standard surgery with a larger incision. Some surgeons start out using a smaller incision and then only extend it if needed. The decision isn't made until the middle of the operation.
You'll have to find out what kind of patient your surgeon is willing to use the new shorter incision on. You may not know if you're a candidate until the doctor has examined you and taken X-rays.