Conclusions Current published evidence does not support survivorship differences among commonly used bearing surfaces in patients younger than age 65 years undergoing THA at short- to mid-term followup .
Background  Total hip arthroplasty ( THA )  is increasingly being performed in patients with long life expectancies and active lifestyles .
Newer implant bearing surfaces , with superior wear characteristics , often are used in this cohort with the goal of improving longevity of the prosthesis , but comparisons across the numerous available bearing surfaces are limited , so the surgeon and patient may have difficulty deciding which implants to use .
Questions / purpose sThe purpose of this study was to answer the following question : Is there a short- to mid-term survivorship difference between common THA bearings used in patients younger than age 65 years ?
Combination of direct and indirect evidence in mixed treatment comparisons.
Mixed treatment comparison ( MTC ) meta- analysis is a generalization of st and ard pairwise meta- analysis for A vs B trials , to data structures that include , for example , A vs B , B vs C , and A vs C trials . There are two roles for MTC : one is to strengthen inference concerning the relative efficacy of two treatments , by including both ' direct ' and ' indirect ' comparisons . The other is to facilitate simultaneous inference regarding all treatments , in order for example to select the best treatment . In this paper , we present a range of Bayesian hierarchical models using the Markov chain Monte Carlo software WinBUGS . These are multivariate r and om effects models that allow for variation in true treatment effects across trials . We consider models where the between-trials variance is homogeneous across treatment comparisons as well as heterogeneous variance models . We also compare models with fixed ( unconstrained ) baseline study effects with models with r and om baselines drawn from a common distribution . These models are applied to an illustrative data set and posterior parameter distributions are compared . We discuss model critique and model selection , illustrating the role of Bayesian deviance analysis , and node-based model criticism . The assumptions underlying the MTC models and their parameterization are also discussed
Conclusions Current published evidence does not support survivorship differences among commonly used bearing surfaces in patients younger than age 65 years undergoing THA at short- to mid-term followup .
Background  Total hip arthroplasty ( THA )  is increasingly being performed in patients with long life expectancies and active lifestyles .
Newer implant bearing surfaces , with superior wear characteristics , often are used in this cohort with the goal of improving longevity of the prosthesis , but comparisons across the numerous available bearing surfaces are limited , so the surgeon and patient may have difficulty deciding which implants to use .
Questions / purpose sThe purpose of this study was to answer the following question : Is there a short- to mid-term survivorship difference between common THA bearings used in patients younger than age 65 years ?