Patient Specific Talus Spacer Post Approval Study

Inclusion Criteria:

1. Subject plans to undergo implantation of the Patient Specific Talus Spacer foravascular necrosis of the ankle joint independent of this research protocol;

2. Avascular necrosis of the ankle joint;

3. Age 21 years old or older;

4. Subject has good general health; and

5. Subject signs a written informed consent form (ICF) prior to the surgical procedure.

Exclusion Criteria:

1. Presence of any contraindication identified in the device Instructions for Use;

2. Surgeon determines that the patient is not appropriate for the Talus Spacerprocedure based on the device IFU (including the enumerated Warnings andPrecautions);

3. Based on the medical opinion of the surgeon, the patient is not appropriate for theTalus Spacer procedure;

4. For female subjects, pregnancy;

5. Active systemic disease, such as AIDS, HIV, or active infection;

6. Active infection or the skin is compromised at the surgical site; and

7. Systemic disease that would affect the subject's welfare;

8. Is a prisoner, incarcerated, or has been coerced to participate in the study thatcould impact the validity of results;

9. Is currently participating in an investigational therapy (device and/orpharmaceutical) within 30 days prior to entering the study or such treatment isplanned during the time course of follow-up.

10. If the Sponsor has notified the site that 30 subjects have been enrolled in thestudy with a Cobalt Chromium Patient Specific Talus Spacer, and the surgeon believesthat a Cobalt Chromium Patient Specific Talus Spacer is the best option for thepatient.

11. If the Sponsor has notified the site that 30 subjects have been enrolled in thestudy with a Titanium (Ti6Al4V) with Titanium Nitride (TiN) coating Patient SpecificTalus Spacer, and the surgeon believes that a Titanium (Ti6Al4V) with TitaniumNitride (TiN) coating Patient Specific Talus Spacer is the best option for thepatient.