During residency I was taught that hip surface replacement did not work because of the high rate of avascular necrosis (AVN) of the femoral head and a high rate of femoral neck fractures (over 30% in three years). However , we now know that this is not true. In the 70's and 80's hip surface replacement was done with metal-on plastic bearings. It is now clear that the failures in the past were primarily due to rapid wear of the plastic bearings resulting in extensive bone destruction (osteolysis). With modern cobalt chrome metal-metal bearings , the rate of femoral neck fractures has dropped to 1% and the rate of AVN to 2%. Most surgeons are not aware of this. The second reason is that the operation is much more difficult to master compared to total hip replacement. Many surgeons are simply not willing to learn these techniques and some just don't have the surgical skills to attempt learning this technique. Only those surgeons who already perform a high volume of hip surgery , and are willing to dedicate a lot of time and energy to master this procedure , should attempt hip surface replacement.