Wear Rates Between Different Clinical Studies

Comparing Wear Rates Between Different Clinical Studies 

Distribution of THA wear rates observed in two studies from Wrightington Hospital. 

Linear wear rate (mm/year) based on radiographs for Charnley components implanted between 1962 and 1968 

Percentiles Wear Rate (mm/year) Charnley (1973) Wear Rate (mm/year) Griffith (1978) 

The data indicates that the distribution of wear rates is more skewed by low-wearing patients in Griffith s study (1978) than in Chamley s study (1973). The distribution of linear wear data for the two studies, in terms of percentiles, is shown in Table 5.1. 

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COMPARING WEAR RATES BETWEEN DIFFERENT CLINICAL STUDIES... 

If two studies have different foUow-up periods, it should be possible to compare the wear rates. In practice, however, differences between patient groups, surgeon groups, and implant systems greatly complicate the task of reconciling differences in wear behavior observed in clinical studies. For example, consider studies published by Chamley and coworkers from Wrightington that describe the wear behavior of UHMWPE in two cohorts. The first cohort, which we have already discussed, consisted of 72 arthroplasties that were implanted between 1962 and 1963 and followed for 9-10 years [26]. The second cohort, described by Griffith et al., consisted of 493 arthroplasties implanted between 1967 and 1968 and followed for 7-9 years (mean, 8.3y) [28]. 

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