Many of my patients with painful hips that have persisted despite non-surgical therapy are interested in exploring surgical options including total hip replacement, a remarkably successful procedure for the treatment of severe hip arthritis. A number of these patients, particularly those that are relatively young and/or very physically active, are also very interested in discussing the different types of implants that are available. One way to categorize these implants is by the type of bearing surfaces, that is the surfaces where the ball meets the socket. The bearing surface is the part of the implant that is subjected to the most wear and tear. Bearing surface options include advanced plastics (polyethylene) rubbing against a metal or ceramic surface, and so called hard-on-hard bearings such as metal rubbing on metal, metal-on-ceramic, and ceramic-on-ceramic combinations. Some of these patients have downloaded material from the internet and may have a specific request for a bearing surface combination based on what they have read.
In my view, the orthopaedic surgeon has an important role to play in patient education in this area. It is very difficult for the lay person to be able to unravel the complexities of the bearing surface debate. In fact, it is a challenge for orthoapedic surgeons at times. The orthopaedic surgeon can help the patient interpret what they have seen on the internet, what they have heard from their friends or what they have seen on TV or in print ads.
We orthopaedic surgeons are keenly interested in the outcomes of the surgeries that we perform, and it is our goal that any joint we replace will allow the patient to return to the activities that they desire and that this joint replacement will last for the rest of their lives. While this is a laudable goal, current materials are subject to a certain amount of wear and tear causing many of us to be conservative in our advice to patients regarding activities following joint replacement. In addition, we inform our patients that further surgery may be necessary in the future due to wear of the implants, particularly wear of the bearing surfaces. While research continues to find even better and longer lasting materials for bearing surfaces in joint replacement, we do advise our patients with the bearing surface options that are currently available.
At the end of the day, we should be guided by the evidence to make this decision. We are now approximately a decade into the “alternative bearing era” – that is, the period of time where orthopaedic surgeons have been using bearing surfaces other than the conventional plastic on metal implants of the past. We have robust clinical outcomes data from clinical research studies. We also have very helpful data from national joint replacement registries that specify what percentage of the implants last for a given period of time, now. We have learned that advanced polyethylenes used in total hip replacement outperform their predecessors. We have learned that some hard-on-hard bearings have not performed well and have been voluntarily recalled from the market, while others are performing well up to 10 years. We have also learned that there is a trade off when selecting the head size; large heads are helpful in minimizing postoperative dislocations, but may be associated with other complications.
Data from national joint replacement registries has been key in our understanding of the performance of implants with alternative bearing surfaces; having a national registry in the US that reflects the practice patterns and device usage in our country would be particularly helpful to orthopaedic surgeons and their patients who are making decisions about implant options. I look forward to a day when orthopaedic surgeons can download real-time data from the American Joint Replacement Registry (AJRR), which the AAOS was integral in establishing, to help guide their decisions, in collaboration with the patient, on the choice of implants and the choice of bearing surfaces. Until that time, evidence from other sources should be used.
Fortunately, the orthopaedic surgeon has multiple successful bearing surface options to choose from. It is unclear at this time which of the available options will last the longest – this answer will emerge through continued clinical outcomes research and information from national joint replacement registries.
For more information on total hip replacements, visit OrthoInfo.org.