The patient population is being drawn for patients seen in the orthopedics department from (April. 2009 -December 2012) patients are selected based on implant type then further selection is based on inclusion and exclusion criteria. Exclusion criteria are specifically selected to exclude any pathologies, or environmental factors that would confound the study population. Once patients are initially selected they are contacted for participation and brought in for screening. Enrollment proceeds until enough patients have been recruited to meet statistical criteria and provide sufficient study power.