Hip replacement

Today, the stem portions of most hip implants are made of titanium- or cobalt/chromium-based alloys; they come in different shapes and degrees of roughness. Cobalt/chromium-based alloys or ceramic materials (aluminum oxide or zirconium oxide) are used in making the ball portions, which are polished smooth to allow easy rotation within the prosthetic socket. The acetabular socket can be made of metal, ultrahigh molecular weight polyethylene, or a combination of polyethylene backed by metal. All together, these components weigh between 14 and 18 ounces, depending on the size needed.
Hip replacements may be "cemented," "cementless" or "hybrid," depending on the type of fixation used to hold the implant in place. Although there are certain general guidelines, each case is individual and your surgeon will evaluate your situation carefully before making any decisions. Do not hesitate to ask what type of implant will be used in your situation and why that choice is appropriate for you. (http://orthoinfo.aaos.org/)

Data from: http://en.wikipedia.org/wiki/Hip_replacement