Table 1.

Change in penetration rate or steady-state rate and wear rate in MOP THA from reports with duration of 9 years or greater

Study	Number of hips	Type of implant	Average age (years)	Duration (years)	Penetration or wear rate	Method of measurement	Findings
Charnley and Halley [2]	72	Charnley	63	9–10	Penetration	Charnley	Progressive decrease in rate until Year 4 and no increase thereafter
Issac et al. [8]	87	Charnley	55	9.25	Penetration	Shadowgraph of explants	No increase in penetration rate with time after the initial peak
Pedersen et al. [22]*	197	Charnley	66.3	10+	Wear	Iowa	No evidence of mid- or late-term acceleration of polyethylene wear; essentially constant wear rates for individual patients
Orishimo et al. [20]	31	AML® gamma sterilized	51.9	17	Wear	Martell	No evidence to support that wear rates were increasing for individual patients
	28	AML® ETO sterilized	54.7	14	Wear	Martell	No evidence to support that wear rates were increasing for individual patients
Dai et al. [3]	38	Omnifit®	56.7	10.9	Penetration	Two-dimensional computer method	No evidence to support that wear rates were increasing for individual patients
Goosen et al. [4]	93	Biomet® gamma-in-air sterilized	50	8.2 (3–12)	Wear	Livermore	Increase in wear rates after Year 6
Goosen et al. [5]	79	Biomet® gamma-in-argon sterilized	55	7.5 (3–12)	Wear	Livermore	No evidence to support that wear rates were increasing for individual patients

* Steady state refers to the rate after the bedding-in period; MOP = metal-on-polyethylene; AML^® = Anatomic Medullary Locking; ETO = ethylene oxide.