Abstract
Metal-on-metal hip resurfacing enjoyed a period of increased global clinical application beginning in the early to mid-2000's. This tapered off quickly, to the point that it is now a niche surgery. One naturally asks the question, why?
The answers are quite simple: 1) There are no clinical benefits when compared with total hip replacements (THA). While many authors have tried valiantly to demonstrate a benefit clinically to performing a resurfacing over a THA, they have simply been unable to convincingly do so. The procedures produce equivalent clinical results. Many claims, such as allowing a patient greater activity levels and return to sports are clearly heavily biased depending on patient selection. The only credible claim to an advantage over THA that can be made regarding resurfacing implants is indeed there is preservation of host bone of the femoral head and neck. However, this retained bone also reduces the femoral head-to-neck ratio compared to a THA and leads to the potential for bone-on-bone impingement that would not be seen if the neck was resected. Additionally the clinician needs to carefully question the true clinical relevance of this preserved bone. One need only think of all of the isolated acetabular component revisions, or polyethylene liner exchanges, that are performed while retaining solidly ingrown femoral components with good preservation of calcar bone years following the index procedure.
2) Resurfacing implants are much more costly than conventional THA implants. In an era of increased cost constraints, parties are willing to pay more only when there is a proven benefit. Resurfacing implants offer no such benefit.
3) There is a well-documented higher revision rate with resurfacing implants over THA.
While the previous claim was that this wasn't seen in younger males, that too has been disproven. The latest data from the Australian Joint Replacement Registry demonstrates the 15-year cumulative percentage revision rates for conventional total hip at 9.7% and resurfacing at 13.3%.
4) There is the significant risk of metal ions and local hypersensitivity secondary to the metal-on-metal bearing. Again, this risk is significantly limited with the use of a THA with a polyethylene insert.
5) There is a significant incidence of femoral neck fractures.
6) The overall femoral component loosening rates are higher than for total hip replacements.
7) There is a clear learning curve with resurfacing implants with most series showing increased complications in the first fifty cases, and depending on a surgeons overall clinical practice, it may be quite a challenge to ever really overcome this learning curve issue.
8) There is difficulty restoring offset and leg length discrepancies in certain cases when trying to utilise a resurfacing implant.
