The material used in a hip replacement is almost always titanium. Once the metal (titanium) support structure is in place, materials can be snapped into that structure to serve as the bearing surface of the hip - the part that does the moving and turning. The inserts for the ball surface are typically metal or ceramic, and the inserts for the socket are usually composed of polyethylene, which looks like a hard and smooth plastic. There are, of course, always exceptions, and different materials for different situations.
Dr. Michael D. O'Brien performs Hip Replacements on a regular basis. He is certified by the American Board of Orthopaedic Surgery and is a fellow of the American Academy of Orthopaedic Surgeons. He is also a past president of the medical staff at St. Luke Hospital where he also served as Chief of Surgery.