Inclusion Criteria:  Patient aged 18 years or older, who has been informed of the research Patient who has had a fourth generation ceramic/ceramic hip replacement implanted for at least two years as a first-line replacement Patient who has had a three-dimensional preoperative examination leading to the design and implantation of a custom femoral stem Patient regularly monitored since surgery and for whom all clinical and radiological data are available at the three-month and two-year follow-up visits  Exclusion Criteria:  Patient operated for revision Patient under legal protection, guardianship or curators Patient who has indicated his opposition to the use of his medical data (by completing and returning the non-opposition form which will be sent to him)