Prospective Evaluation of Clinical and Radiographic Outcomes Following Total Talus Replacement (PROCLAIM)

Inclusion Criteria: * ≥22 Years of Age * Scheduled to receive TTR implant for one of the following indications: * Avascular necrosis of the talus * Avascular necrosis of the talus in addition to talar collapse, cysts or non-union * Large, uncontained, unstable, or cystic talar osteochondral defects with risk of collapse or talar osteochondral defects not responsive to traditional treatments * Nonunion following talar fracture or talar extrusion, unresponsive to more conservative treatments * Have not had a prior Total Talus Replacement device implanted * Not planning to receive bilateral Total Talus Replacement devices * Subject signs a written informed consent form (ICF) prior to the surgical procedure Exclusion Criteria: * Surgical procedures other than those listed in the indications for use. * Use of implant greater than 6 months from date of patient's preoperative CT scan. * Degenerative changes in the tibiotalar, subtalar or talonavicular joints. * Gross deformity in sagittal or coronal planes. More than 15 degrees of varus or valgus deformity in the coronal plane, or more than 50% subluxation anteriorly or posteriorly of the talus in the sagittal plane * Patients with an active local or systemic infection. * Osteonecrosis of the calcaneus, distal tibia or navicular. * Known history of existing malignancy, or any systemic infection, local infection, or skin compromise at the surgical site. * Blood supply limitations and previous infections that may prevent healing. * Physical conditions that would eliminate adequate implant support or prevent healing, including inadequate soft tissue coverage. * Conditions which may limit the patient's ability or willingness to restrict activities or follow directions postoperatively during the healing period. * Presence of neurological deficit which would prevent patient postoperative compliance. * Patients with foreign body sensitivity, suspected or documented material allergy or intolerance. Where material sensitivity is suspected, appropriate tests should be conducted, and sensitivity ruled out prior to implantation.