This is a Post-Marketing Surveillance of Quadra-P anteverted stem prosthesis.

The primary objective of this study is to evaluate the 10-year survival of the anteverted Quadra-P stem in patients operated for primary total hip arthroplasty, according to the inclusion criteria.

Secondary objectives:

• To assess clinical performance by Harris Hip score collected during preoperative and postoperative visits at 3 months, 1, 2, 5, 7 and 10 years.
• Assess radiological performance by standard radiographic examination performed preoperatively, postoperatively before discharge and during postoperative visits at 3 months, 1, 2, 5, 7 and 10 years.
• Assessing the patient's perception of the prosthetic joint by means of FJS questionnaire collected during the preoperative visit and postoperative visits at 3 months and at 1, 2, 5, 7 and 10 years after surgery.
• Assessment of functional recovery by gait analysis study
• Collect the rate of complications throughout the course of the study

Inclusion Criteria:

• Subjects suffering from primary hip arthrosis, post-traumatic arthrosis, dysplasia or avascular necrosis of the femoral head, rheumatoid arthritis
• Adult subjects between 18 and 75 years of age on the date of surgery
• Subjects eligible for primary total hip arthroplasty surgery for whom the anterior Quadra-P femoral component will be implanted according to the indications for use of the implant
• Subjects who are willing and able to provide written informed consent for participation in the study. Written informed consent must be obtained prior to surgery.

For the anatomical-functional subgroup:

- Adult subjects aged between 18 and 65 years at the date of surgery who have agreed to undergo the gait analysis study.

Exclusion Criteria:

• Subjects with acute or chronic infection
• Subjects with a femoral neck fracture
• Subjects with mental conditions that impair their ability to consent to the study, to complete required questionnaires or to complete follow-up visits
• Subjects with severe deformities, at the discretion of the surgeon
• Subjects with metabolic disorders that may involve bone metabolism for which an uncemented implant would be contraindicated
• Subjects with muscular atrophy or neuromuscular diseases
• Subjects allergic to the materials used during surgery
• Subjects unable or unwilling to provide consent for participation in the study
• Any other condition not mentioned in the inclusion criteria

The aim of the study is to monitor the clinical performance and survival of the Quadra-P antevert stem when used according to its indications. Since patients are not subjected to additional risks or procedures compared to standard practice, the total number of patients was defined on the basis of the surgeon's potential and observational studies of the same type already published in the literature.

For the anatomical-functional subgroup, a sample size was defined to verify 10% speed increases between pre- and postoperative. Considering α = 5% and Power = 90%, 30 patients will be required.