The specific aim is to quantify the stability of the acetabular and femoral components of a revision total hip arthroplasty (THA) in vivo as currently performed at our institution. In this way, the investigators will gain insight into the outcome of the current state of the art of revision arthroplasty surgery. In the past, acetabular and femoral component stability has been measured using radiostereometric analysis (RSA) and when patients having revision total hip operations were compared to patients undergoing primary total hip operations it was possible to determine differences in stability and this was predictive of the intermediate to long-term performance of the acetabular and femoral reconstruction. The investigators propose to use this established, high resolution technique to assess and compare the stability of the revision implants.

Inclusion Criteria:

1. Male or female.
2. 25 to 75 years of age.
3. Subjects requiring revision total hip replacement.
4. Subjects who demonstrate the ability to return to MGH for follow-up for the next five years.

Exclusion Criteria:

1. Subjects with limited life span.

2. Subjects with difficulty in comprehending study protocol for any reason.

3. Subjects with complex disease entities which significantly increase the risks of the surgery such as any major platelet abnormality, hematological disorder, or any other major medical complication which could substantially reduce longevity, put them at further risk due to immunocompromisation or increase the risk of infection.

4. Female subjects that are pregnant or who may suspect they are pregnant or who plan to become pregnant while participating in this study.

   • A urine HCG will be done in all women of child bearing potential prior to RSA imaging at each follow-up visit. The result will be recorded in the research record.