Study staff was unable to collect proper samples to meet study goals

Previous studies have shown an increase in the concentration of mesenchymal stem cells (MSC's) in the setting of osteoarthritis of the knee and its correlation to severity. Researchers have shown that as there is an increase in the severity of the disease, the concentration of stem cells also increases. The purpose of this study is to determine if there is the same increase in stem cell concentration in patients with osteonecrosis (ON) of the femoral head.

Since the treatment of osteonecrosis is related to the severity of disease, namely articular cartilage collapse, the purpose of this study is to determine if the MSC concentration in synovial fluid can be correlated to disease stage. In order to do this the investigators will:

Milestone #1:

Determine the concentration of MSC's in the synovial fluid in patients with osteonecrosis. This work will be carried out utilizing FACS-based technique to synovial fluid stem cell sub-population.

Milestone #2:

Compare concentrations of MSC's in patients with pre collapse, post collapse osteonecrosis and "normal" hips. Patient-derived MSC will be quantified at the different stages of disease and assays will be performed in order to assess their viability. A control group will be selected in patients undergoing hip arthroscopy for femoral/acetabular impingement (FAI). Since FAI does not affect the intraarticular environment of the hip, theoretically these patients would have a "normal" concentration of synovial stem cells.

Inclusion Criteria:

• Patients consented to undergo a THA (post-collapse osteonecrosis), hip arthroscopy or minimally invasive core decompression
• Preoperative radiographic diagnosis of ON or FAI (femoral/acetabular impingement)

Exclusion Criteria:

• Pregnant females
• Active infection, HIV, Hepatitis C or B, syphilis Immunodeficiency
• Patients receiving hematopoetic growth factors or anti-angiogenesis products

Patients will be identified in clinic as scheduled for total hip arthroplasty, hip arthroscopy or minimally invasive core decompression of the femoral head after granting consent.