Total hip replacement surgery, introduced in the United States in the early 1970s, is one of the most frequently performed orthopaedic procedures. According to the University of Pennsylvania Orthopaedic Journal (UPOJ), excellent function is achieved in 95 per cent of patients who undergo total hip arthroplasty, with few complications.
Total hip arthroplasty replaces the "ball and socket" joint of the hip with artificial parts (prostheses). Hip replacement prostheses now often use ceramic balls and cups. Since total hip arthroplasty is an expensive surgery, understanding the advantages and risks of the new option is important for candidates considering the procedure.
The use of ceramics in hip replacement prostheses was introduced to avoid problems associated with using metal and polythene. Ceramic hip replacements have the advantage of using an extremely hard substance that is smoother than metal and has other friction-reducing properties.
True Ceramic Hips
True ceramic total hips, or ceramic-on-ceramic total hips, have cups and balls both made from aluminium oxide ceramics. Ceramic-on-ceramic hip prostheses produce the lowest quantity of wear particles of any materials combination used to manufacture total hip joints. This is significant because, according to the current theory, risk of total hip replacement failure depends directly on the amount of wear particles produced inside the joint. Nevertheless, there are problems with ceramic-on-ceramic hip prostheses.
Extreme movements and exercises can cause impingement of the total hip joint in which the ceramic cup receives a weakening blow. Repeated impingement can cause the ceramic cup to splinter and fracture. More careful placement of the cups during surgery and patient awareness of the inadvisability of extreme movements with this kind of hip replacement can reduce the risk of impingement.
When ceramic hip replacements were first introduced, there were concerns about incidents of fracture. With improvements in manufacturing, however, this cause for concern has been greatly reduced. In a 2009 article in the UOPJ, Marvin E. Steinberg, MD, reported that the incidence of fracture is "in the order of 1 in 60,000." In "The Journal of Bone and Joint Surgery (American)," Christine Heisel, MD, et al., give the incidence of ceramic ball fracture as 4 in 100,000. The more common ceramic liner fracture can be caused by repeated impingement and is often diagnosed too late.
Ceramic Ball Fracture
Although rare, fracture of the ceramic ball can have serious consequences. When the ball explodes, microscopic fragments are dispersed in soft tissues around the hip. The mixture of fragments, soft tissues and possibly polythene particles can form an abrasive paste. If the paste and soft tissues are left in place during revision surgery, there is a good chance that the revised hip replacement will fail.
Although wear is minimal with ceramic hip prostheses, chemical properties of ceramics over time may create problems over the long term. Since the use of ceramics in total hip arthroplasty is relatively new, the long-term outlook remains to be seen. Together with the possibility of ceramic ball fracture, the newness of the procedure is one of the most important considerations to weigh in deciding whether to go with a ceramic hip replacement.