Survival of hard-on-hard bearings in total hip arthroplasty: a systematic review.
BACKGROUND
Improvements in prosthetic materials, designs, and implant fixation for THA have led to bearing surface wear being the limitation of this technology. Hard-on-hard bearings promise decreased wear rates and increased survival. However, there may be different survival rates based on bearing materials, manufacturing technologies, and femoral component designs. Additionally, survival rate variability may be based on study design.


OBJECTIVE
We determined survival rates and study levels of evidence and quality for the following bearings: stemmed metal-on-metal THA, metal-on-metal hip resurfacing, ceramic-on-ceramic THA, and ceramic-on-metal THA.


METHODS
We performed a systematic review of the peer-reviewed literature addressing THA hard-on-hard bearings. Quality for Level I and II studies was assessed.


RESULTS
The four Level I or II second-generation stemmed metal-on-metal THA studies reported between 96% and 100% mean survival at 38 to 60 months. The two Level I hip resurfacing studies reported 94% and 98% mean survival at 56 and 33 months. The four Level I studies of ceramic-on-ceramic THA reported survival from 100% at mean 51 months to 96% at 8 years.


CONCLUSIONS
While hard-on-hard bearing survival rates have generally been variable with earlier designs, contemporary implants have demonstrated survival of 95% or greater at followup of between 3 and 10 years. Some variability in survival may be due to differences in surgical technique, component positioning, and implant designs. As bearing designs continue to improve with modified materials and manufacturing techniques, use will increase, especially in young and active patients, though concerns remain about the increased reports of adverse events after metal-on-metal bearings.
Center for Joint Preservation and Replacement, The Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, 2401 West Belvedere Avenue, Baltimore, MD 21215, USA.
Michael G
MG
Zywiel
Siraj A
SA
Sayeed
Aaron J
AJ
Johnson
Thomas P
TP
Schmalzried
Michael A
MA
Mont
D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D020099:Coated Materials, Biocompatible / Q000592:standards; D019544:Equipment Failure Analysis; D006244:Hardness; D006622:Hip Prosthesis / Q000592:standards*; D006801:Humans; D008422:Materials Testing; D011474:Prosthesis Design; D011475:Prosthesis Failure; D033081:Shear Strength; D013499:Surface Properties; D016474:Weight-Bearing
D020099:Coated Materials, Biocompatible