On February 17th, 2021, the FDA officially approved the use of the first patient-specific 3D-printed talar implant for compassionate use. This is a patient-specific talar spacer designed to completely replace the talus for the treatment of talar avascular necrosis. The implant represents an alternative to other surgical procedures that allows joint preservation.

Recently, at the First Clinic of the Rizzoli Orthopaedic Institute, a prosthetic device has been developed that combines the tibial and meniscal components of a FAR-type ankle prosthesis (Adler Ortho) with a total talus replacement implant. Since the device is patient-specific and implanted using custom-made cutting guides, it reduces surgical invasiveness on surrounding bone structures as well as on ligamentous and tendinous structures, thereby preserving ankle function as much as possible.

The customization is based on a next-generation prosthetic model produced using additive manufacturing technology and featuring hypoallergenic properties, as it is made of a titanium alloy and treated with a nitriding process.

The aim of this study is therefore to evaluate the outcomes of this prosthetic device over time.

**INCLUSION CRITERIA:**

1. Male or female patients aged between 35 and 75 years.
2. Pathology of the tibiotalar joint requiring surgical intervention with prosthetic replacement.
3. Severe cases of bone loss or talar bone compromise.
4. Customisation performed at the Rizzoli Orthopaedic Institute.
5. Signed informed consent for participation in the study.
6. Patients must be prepared and motivated to comply with preoperative and postoperative investigations, rehabilitation protocols, follow-up schedules, and study questionnaires.

**EXCLUSION CRITERIA:**

1. Patients unable to understand or provide informed consent.
2. Pregnant women.
3. Body mass index (BMI) > 40.
4. Refusal to sign the informed consent form for study participation.
5. Substance abuse or psychological disorders that may interfere with adherence to rehabilitation and postoperative assessment protocols.
6. Known hypersensitivity to device materials.
7. Active or suspected latent infection in or around the affected ankle joint.
8. Previous orthopaedic surgery on the lower limbs within the last year, or planned orthopaedic surgery within one year (excluding ankle replacement).
9. Presence of neuromuscular or neurosensory deficits limiting the ability to assess device safety and efficacy.
10. Diagnosis of systemic disease (e.g., systemic lupus erythematosus) or metabolic disorder (e.g., Paget's disease of bone) leading to progressive bone deterioration.
11. Immunosuppression or excessive steroid therapy beyond physiological requirements (e.g., >30 days).
12. Pregnant and/or fertile women.

Patients with degenerative pathology of the tibiotalar joint associated with significant bone loss or talar bone compromise, for whom further diagnostic evaluation using CT imaging is required to determine a potential surgical indication, will be included in this pilot study. In the case of confirmation of the indication for total ankle replacement with total talar substitution, patients will undergo a CT scan of the contralateral ankle for implant design (as per standard clinical practice for the development of patient-specific implants) and surgical planning. Following surgery, patients will be evaluated at subsequent follow-up visits according to routine clinical practice.

All study procedures will be conducted at Clinic I of the Rizzoli Orthopaedic Institute (patient selection and enrolment, and diagnostic imaging).

The study population consists of patients aged between 35 and 75 years affected by degenerative disease of the tibiotalar joint associated with severe bone loss or tala