Lack of enrollment interest.

The purpose of this study is to determine if avascular necrosis of the acetabulum is present in metal-on-metal revisions and to what depth this dead avascular bone occurs.

A convenient sample of a consecutive series of 15 patients treated for metal on metal acetabular revision surgery will be included.

Patients being treated for metal on metal acetabular revision surgery by a physician at OrthoCarolina, PA will be screened for eligibility. These patients will be approached by their surgeon and asked to volunteer their participation in the study. Potential subjects will meet with a research coordinator to discuss details of the study and those you volunteer participation will be asked to sign an informed consent prior to the collection of study data. . Basic demographic information (initials, age, gender, height, weight, BMI), dates of original index surgery, reason for revision, type of implant being removed, and standard of care cobalt and chromium metal ion levels will be collected via chart review.

Patients who meet all eligibility criteria will have three biopsies performed at the time of their revision surgery. A pathologist will note the presence or absence of bone necrosis and will measure the length (mm) of necrosis, acute inflammation, chronic inflammation, normal bone, and entire bone specimen in order to obtain a ratio.

Biopsy Protocol:

A bone biopsy is a procedure in which bone samples are removed (with a special instrument during surgery) and looked at under a microscope for necrosis (tissue death), infection, or other bone disorders. Once the acetabular hip replacement implants have been removed the following steps will occur:

• The biopsy needle will be inserted into the bone (3 locations; 2 from ilium, 1 from pubis or ischium = 3 total).
• The biopsy needle will be withdrawn and firm pressure will be applied to the biopsy site for a few minutes, until the bleeding has stopped.
• Each bone biopsy sample will be labeled sequentially and by anatomic location (i.e., ilium #1, ilium #2)
• The normal bone will be marked on the bone sample.
• The bone biopsy sample will be sent to the lab for examination.
• The acetabulum bone will be reamed so the new implant can be seated.

Inclusion Criteria:

• Patients being revised for an aseptic metal on metal acetabular revision.
• Patient is greater than one year postoperative.
• Patient has had cobalt and chromium metal ion levels tested within 6 months of the planned revision surgery.
• Understands the local language and is willing and able to follow the requirements of the protocol.
• Understands the informed consent and signs the institutional review board or independent ethics committee (IRB/IEC) approved informed consent form.

Exclusion Criteria:

• History of infection
• Evidence of current substance or alcohol abuse
• Being treated with radiation, chemotherapy, immunosupression, or chronic steroid therapy (prednisone use up to 5 mg/qd or its equivalent is allowed)
• Is a prisoner

A convenience sample of a total of 15 patients will be enrolled at OrthoCarolina.