The lab contracted by the site to complete specimen analysis backed out on their agreement to do so. At this time it is not feasible for a new contract to be entered into by the site.

The purpose of the study is to develop a biomarker assay to be used as a diagnostic tool for adverse local tissue reaction, or tissue necrosis, in a metal on metal total hip replacement.

A convenience sample of a total of 100 hip patients will be enrolled: 50 metal-on-metal revision hips, 25 metal-on-poly revision hips, and 25 pre-operative total hips (no implant, control group) will be enrolled. Preoperative blood serum samples and intraoperative synovial fluid will be obtained from all hips and used for biomarker testing. Additionally, intraoperative assessment of tissue necrosis will be assessed.

Well-functioning MoM implants have shown an increase in serum cobalt and chromium (CoCr) ion levels from the metal debris generated from the implant wear.However, the current evidence suggests that measuring ion levels is unreliable and that increasing ion levels do not correlate with tissue damage. In addition to measuring blood and synovial fluid metal ion levels, ultrasound and MRI with metal artifact reduction sequences (MARS) have been utilized to assess periarticular reactions secondary to metal wear debris. Despite metal reduction software these scans are frequently difficult to interpret. While each of these tests has merit, at the present time there is no single diagnostic test available which delineates the key issue that demands urgent surgical intervention, i.e. tissue necrosis. It is important to have a reliable test to guide surgeons and patients in the shared decision-making process of when surgical intervention is necessary to prevent disabling tissue damage. For this reason, the current study proposes an examination of preoperative serum samples of subjects in addition to synovial fluid collected during revision surgery for biomarkers that may indicate tissue necrosis. To maximize the chance of success of identifying serum biomarkers, all samples will be analyzed using multianalyte assay, biomarker tests. The purpose of the study is to develop a biomarker assay to be used as a diagnostic tool for adverse local tissue reaction, or tissue necrosis, in a metal on metal total hip replacement.

A convenience sample of a total of 100 hip patients will be enrolled: 50 metal-on-metal revision hips, 25 metal-on-poly revision hips, and 25 pre-operative total hips (no implant, control group) will be enrolled. Preoperative blood serum samples and intraoperative synovial fluid will be obtained from all hips and used for biomarker testing. Additionally, intraoperative assessment of tissue necrosis will be assessed.

Inclusion Criteria:

• Patients presenting for a metal on metal hip revision who have cobalt and chromium metal ion levels tested within 6 months of the date of the planned revision surgery.
• Patients presenting for a metal on poly hip revision
• Revision hip patients must be greater than one year postoperative
• The diagnosis at the time of the index, or primary, hip replacement was osteoarthritis.
• Patients who have hip osteoarthritis but have not had a total hip surgery (control)

Exclusion Criteria:

• Patients presenting for a metal on metal hip revision who have cobalt and chromium metal ion levels tested >6 months of the date of the planned revision
• Patients with a total hip on the contralateral side.
• Patients with a prior history of periprosthetic infection
• Revision cases where the diagnosis at the time of the index, or primary, hip replacement was not osteoarthritis.
• Prisoners
• Patients not willing to consent for the proposed treatment
• Patients with an altered mental status
• Active, concurrent metastatic infection
• Active, superficial infection
• Patients presenting for a metal on poly hip revision to treat trunionosis

A convenience sample of a total of 100 hip patients will be enrolled at orthopedic clinics.