Transient cognitive changes after surgery may be due to many different factors. It is estimated that between 5-29% of patients undergoing orthopedic surgery experience a transient decline in their cognition. Fat and bone marrow debris embolization can cause cognitive changes if they enter the cerebral circulation in significant numbers. During total hip arthroplasty the placement of the femoral stem leads to a rise in intramedullary pressure which can cause fat and bone marrow debris to embolize into the systemic circulation. Total hip resurfacing arthroplasty avoids entrance into the femoral canal. The purpose of this study is to assess transient cognitive changes after total hip arthroplasty and compare them to patients undergoing total hip resurfacing arthroplasty. We hypothesize that patients undergoing total hip resurfacing arthroplasty will experience less transient cognitive changes due to the avoidance of violating the femoral canal during the procedure.

Inclusion Criteria:

1. Male and non-pregnant, non-lactating, female subjects who are 18 and older
2. Subjects who are able and willing to provide informed consent
3. Subjects deemed able to comply with study schedule visits and procedures
4. Subjects undergoing elective THA procedures
5. Subjects undergoing elective total hip resurfacing arthroplasty
6. Subjects in satisfactory health as determined by the investigator on the basis of medical history and physical examination.

Exclusion Criteria:

1. Subjects with or with a history of Parkinson's Disease
2. Subjects with a history of depression as reported in their past medical history
3. Subjects with a history of dementia as reported in their past medical history
4. Subjects currently using antidepressants
5. Subjects currently using antipsychotic medications

Patients undergoing either Total Hip Arthroplasty or Total Hip Resurfacing Arhtroplasty at our Institution