REDAPT Retrospective-Prospective Modular Stem Study

Inclusion Criteria: Retrospective Limited Data Collection/Enrollment Phase: • Subject has undergone revision hip arthroplasty with the REDAPT™ Revision Femoral System modular stem with implantation from 2012 to the date of Institutional Review Board (IRB)/Ethics Committee (EC) approval ofthe original version 1.0 protocol at the study site. Retrospective Expanded Data Collection \& Prospective Follow-Up Phase: * Subject completed limited retrospective data collection phase and willing to consent to expanded retrospective data collection and the prospective phase of the study; * Subject is willing and able to participate in required follow-up visits at the investigational site and to complete study procedures. Exclusion Criteria:Retrospective Limited Data Collection/Enrollment Phase: • Not applicable Retrospective Expanded Data Collection \& Prospective Follow-Up Phase: * Subject, in the opinion of the PI, has an emotional or neurological condition that would pre-empt their ability or willingness to participate in the study including mental illness, mental retardation, drug or alcohol abuse; or * Subject is known to be at risk for lost to follow-up, or failure to return for scheduled visits.