A Talus Implant in Patients Between 20-60 Years of Age Followed up for a Minimum of 2 Years After Surgery

Localized cartilage injuries in the ankle occur when distinct areas of the cartilage in the ankle joint become damaged or worn down. This can lead to pain, swelling, reduced mobility and function, and an increased risk of osteoarthritis over time. The challenge with these injuries is that cartilage has a limited capacity for self-healing due to its lack of direct blood supply. Treatment options remain limited, as conventional methods such as physiotherapy or anti-inflammatory medications only address symptoms rather than the underlying damage. More invasive procedures, such as joint replacement or extensive reconstructive surgery, are associated with prolonged rehabilitation periods and variable success rates, particularly in younger, active patients. This highlights the need for precise, customized treatment solutions that can directly repair the damage and effectively restore joint function. A patient-specific implant has been designed to address focal cartilage injuries in joints, primarily in the knee but also in the ankle. The implant is based on advanced imaging and 3D modeling to adapt to the patient's unique joint anatomy and extent of injury. The method involves open surgery to replace the damaged cartilage and adjacent bone with a metal implant (cobalt-chromium) that mimics the patient's original joint surface. This facilitates targeted pain relief and improved joint function, offering a personalized treatment alternative for patients with localized cartilage defects. Compared to traditional ankle joint replacements or arthrodesis, the use of this implant is considered less invasive and associated with a shorter recovery period, reducing patient burden and allowing for a quicker return to daily activities. Additionally, the patient-specific design of the implant has the potential to minimize implant-related complications, such as implant wear and implant-related pain. Early clinical studies on this implant have shown promising results regarding pain relief, improved joint function, and patient satisfaction. However, only a limited number of reports exist to date, and further studies are needed to assess the long-term effects of the implant on pain, function, and quality of life.

The implant may represent a significant advancement in orthopedic surgery and has the potential to improve the quality of life for patients suffering from ankle joint injuries and osteochondral lesions.

In conjunction with the introduction of this method and implant, particularly in younger patients, the investigators aim to conduct a pilot study on the early outcomes of the first ten patients, focusing on safety, feasibility, and efficacy.

This project aims to evaluate the surgical outcomes in patients aged 20 to 60 years with challenging cartilage injuries in the ankle, two years postoperatively following implantation of a custom-made talus implant. The study focuses on safety, feasibility, and efficacy. Complications and adverse events will be recorded.

Clinical function will be assessed using the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score, a well-validated and reliable scoring system, while HRQoL will be assessed using the EQ-5D-5L score.

Ten patients with osteochondral lesions will be included in the study. Patients will be selected from a clinical population with moderate to severe symptoms and will be treated at an orthopedic clinic (DS) with expertise in managing ankle osteoarthritis/cartilage injuries and performing the talus implant implantation. Through this recruitment process, the investigators aim to establish a cohort that reasonably reflects the patient population with ankle osteoarthritis at our clinic, thereby enhancing the quality and relevance of the research.

Upon inclusion, patients will undergo a clinical examination, X-ray, and MRI imaging of the foot to assess the extent of the injury and joint geometry. The Berndt-Harty classification system will be used to categorize the injury based on radiographic images, and the Bristol-Hepple classification will be employed to describe lesion size, edema, displacement, and cyst formation based on MRI images. Patients will undergo implantation of the talus implant performed by a qualified orthopedic surgical team. Pre- and postoperative pain management protocols will be implemented. Standard postoperative follow-up plans, including rehabilitation and physiotherapy, will be provided. Patients will be followed up clinically at 6 weeks, 6 months, 1 year, and 2 years postoperatively.

Additional data collected include: Demographic data: Age, sex, surgical time (minutes).

Clinical data: Time of diagnosis, treatment initiation, treatment type, and treatment course.

Patients will be informed about the study and will provide written consent before inclusion. To ensure ethical and legal informed consent, patients will receive a detailed consent form explaining the nature of the study, what participation entails, and how patient data will be managed to protect confidentiality. Only after obtaining written consent will patients be included in the study.

In this study, the power calculation is challenged by a limited patient sample, which affects the potential for statistical significance. With a single cohort of 10 patients over a two-year period, the sample size restricts the ability to detect statistically significant differences in AOFAS and EQ-5D-5L scores. Reduced statistical power is an inherent consequence of the small sample size. The results, primarily descriptive and exploratory, must be interpreted with caution and regarded as a foundation for further research. Alternative analytical approaches will be considered to maximize the value of the collected data.

The following data processing and statistical analysis methods are planned:

• Descriptive statistics to summarize demographic and baseline clinical characteristics of participants.
• T-tests or Wilcoxon signed-rank tests to compare pre- and postoperative outcomes on continuous variables such as pain (NRS), AOFAS scores, and HRQoL (EQ-5D-5L), depending on data distribution.
• ANOVA or Kruskal-Wallis tests for comparisons across multiple time points or groups.
• Linear regression models to analyze relationships between predictors (e.g., age, sex, injury severity) and outcome variables (e.g., pain, function, HRQoL).
• Calculation of the Minimum Clinically Important Difference (MCID) for EQ-5D-5L to establish the smallest score change perceived as clinically meaningful by patients.
• Kaplan-Meier survival analysis to estimate revision rates over time.
• Cox proportional hazards models to assess risk factors for potential implant revisions. A detailed analysis plan will be developed before data collection begins to ensure that the study has sufficient power to detect any significant differences or associations.