Metal-on-metal total hip arthroplasty: the concerns.
The metal-on-metal bearing couple is having a resurgence in clinical applications seen in total hip and hip resurfacing technologies. The most noteworthy advantage of a metal-on-metal implant is the improved wear characteristics seen in vitro on wear simulators and in vivo with retrieved implants. All bearings have disadvantages, and a metal-on-metal bearing is no exception. Concerns exist regarding the generation of metal ions seen in the blood and urine of patients with metal-on-metal implants. These elevated metal ions have theoretical, although not proven, risks related to carcinogenic and biologic concerns. Additionally, concerns exist regarding hypersensitivity, increased incidence of instability and increased costs. Specific patient selection issues arise with metal-on-metal implants. The current generation of implants has only early and mid-term results available, with no long-term series yet published. Therefore, although a metal-on-metal bearing may be considered a viable alternative to either polyethylene or ceramic implants, outstanding and unresolved issues continue to exist with this bearing, as they do with the alternatives.
MacDonald
S J
SJ
Division of Orthopaedic Surgery, University of Western Ontario & London Health Sciences Centre, University Campus, 339 Windermere Rd., London, Ontario N6A 5A5, Canada. steven.macdonald@lhsc.on.ca
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods; D002516:Ceramics / Q000009:adverse effects / Q000737:chemistry; D019245:Compressive Strength; D005260:Female; D017276:Friction; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008422:Materials Testing / Q000379:methods*; D008670:Metals / Q000009:adverse effects / Q000737:chemistry*; D008875:Middle Aged; D018579:Patient Selection; D011379:Prognosis; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016032:Randomized Controlled Trials as Topic; D016059:Range of Motion, Articular / Q000502:physiology; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013997:Time Factors; D016896:Treatment Outcome
D008670:Metals