The bipolar head is recommended to treat femoral neck fractures and is a good choice to use it directly as sliding partner with the acetabulum.
The principle of having differing rotation centers in the bipolar head’s outer cup and inner head is established since many years as standard in treating femoral neck fractures. The high range of rotation and low relative motion between acetabulum and outer cup are central. This leads to a self-centering effect of the implant. The cartilage in the acetabulum is spared at best due to the large contact area and the highly polished metal surface of the bipolar head. The safety ring – once removed and correctly placed onto the femoral neck – builds a dislocation-proof connection.