The goal of this observational study is to collect clinical and radiological data to monitor the safety and performance of the ROMAX hip resurfacing system. The main parameter that will be measured is the rate of revisions at 10 years.

This single-center, post-market, prospective, longitudinal, and uncontrolled cohort study aims to evaluate the survival rate of the Medacta ROMAX hip resurfacing system, particularly focusing on dislocations and the potential consequences of wear over a 10-year period. Additionally, the study will assess clinical performance through patient-reported outcomes (PROMs) and analyze the migration behavior of the device using the CTMA method in a subgroup of 40 patients. The study will include a total of 150 cases, with 40 patients undergoing CTMA analysis at 3 years post-surgery. Eligible patients will be informed during preoperative visits and included upon signing the consent form, prior to surgery. Participation in the CTMA subgroup is optional and does not affect overall study inclusion. Follow-ups will be conducted at 3 months, 1, 3, 5, and 10 years. Data collection will include clinical scores, clinical and radiological data related to preoperative and postoperative status, and perioperative surgical details.

Inclusion Criteria:

• Patients eligible for hip resurfacing, suitable for the implantation of a Medacta ROMAX hip resurfacing system according to the manufacturer's defined indication for use.
• Aged between 18 and 65 years at the time of surgery.
• Ability and willingness to provide written informed consent for participation.

Exclusion Criteria:

• Active infection
• BMI > 40
• Mental illness, when the known pathology is likely to compromise the patient's ability to consent, affect the patient's assessment of their progress, or complete follow-up appointments and exams.
• Significantly deformed anatomy (at the surgeon's discretion)
• Osteomalacia where the fixation of an uncemented implant is contraindicated
• Active rheumatoid arthritis
• Osteoporosis
• Metabolic disorders likely to impair bone formation and for which the fixation of an uncemented implant is contraindicated
• Muscle atrophy or neuromuscular disease
• Known allergy or hypersensitivity to the implant material
• Any patient who cannot or does not wish to give informed consent to participate in the study
• Patients whose chances of regaining independent mobility would be compromised by known concomitant medical issues.

150 patients undergoing hip resurfacing surgery and receiving the ROMAX system will be recruited consecutively by the study investigator. All patients will be offered to join the CTMA subgroup until the number of 40 subjects is reached. Choosing not to participate in the CTMA subgroup will not prevent the patient from participating in the study.