How is cartilage replaced during hip reconstructive surgery?

Assuming joint is : Being replaced for the reason the cartilage is no longer any good so a new hip joint is positioned which is generally a metal stem with a ball head that fits into the femur and fits into a cup usually made of a high density plastic on the pelvis side. This is the most common type of artificial joint. There are other materials that can be used such as ceramics & all metal ones.

It's not. : Cartilage is found at the ends of bones, where they articulate. When the hip is replaced, usually both sides of the joint are replaced. The hip joint is a ball and socket. The head of the femur is the ball and the acetabulum is the socket. The two replacement parts slide against each other, so there is no need for cartilage. If we replace cartilage, it might be simpler!