Abstract
The use of hard-on-hard bearings, including ceramics peaked in the mid 2000's and has seen rapid decline since that time. Ceramics are not new to the market place but have had a 40 year history outside the U.S. The basis for renewed enthusiasm for ceramics included improved manufacturing, improved taper tolerances, higher strength, and lower wear. In spite of the major improvements concerns have been expressed with new generation ceramics by the experts and thought leaders in the field. The major concerns included complications related to modularity, continued problems with fracture and consequences of fracture, limited surgical options, and squeaking and impingement. The conclusion of one review article was that “although ceramics show promise as a lower wear articulation, manufacturing and design modifications and improvements will continue in an attempt to address the substantial concerns that persist”. Modifications have indeed occurred. The question is rather all of these concerns have been addressed and the answer is no. One proposed solution was a hybrid material of Alumina and Zirconia (Delta Ceramic). The advantages included higher strength, lower wear, more options and possibly less squeaking. Unfortunately the modest material improvements did not begin to overcome the obstacles to adopting this technology. High on this list is the problem with cost with the current health care environment unwilling to pay for expensive new technology that does not have proven value. A 2nd major issue is new technology must account for variability in surgeon performance in maximising margin for error. The medical legal environment is unforgiving of failure of new unproven options. Most of the old issues with ceramics have not been completely resolved. Delta Ceramic in particular, has increased cost with no demonstrated benefit.
A major problem is there is no known problem with metal or ceramic against cross-linked polyethylene bearing in terms of wear or osteolysis in the 10–15 year time frame. Among all the bearing articulations, metal-on-cross-linked performs the best. The persistent vexing problems with ceramics include impingement, liner breakage, and squeaking. Ceramic components do not tolerate component malposition which increases wear and squeaking. The problem is that a substantial percentage of hip replacements are put in outside of the ideal radiographic zone even at specialty centers. Breakage continues to be a problem especially with liners. There is also a need for complete rim exposure for concentric placement with impaction of liners which makes ceramics less compatible with small incision surgery. The problem of squeaking has not been solved by Delta Ceramic. Originally a case report appeared in the literature of squeaking with Delta Ceramic. Since that time a large scale study has showed that only 69% of Delta Ceramic hips were silent with up to 13% being associated with reproducible squeaking.
While a new generation of ceramics are better than the earlier generation and have lowered the fracture risk and increased intraoperative options, the current generation ceramics still provide far fewer options than a standard metal-on-cross-linked total hip. The current generation metal-on-cross-linked total hips have 10–15 year results that cannot be improved upon in terms of wear and osteolysis. Other unsolved problems include breaking, chipping and squeaking. Ceramic-on-ceramic is less tolerant of suboptimal position which leads to impingement, edge loading, and an increased incidence of squeaking. Until all of these problems are successfully addressed, ceramic-on-ceramic cannot be advocated for widespread use.
