In this study, the investigators seek to validate 3D model-based dGEMRIC (delayed gadolinium enhanced MRI of cartilage) values against histologic grading of cartilage quality, using osteochondral samples of the femoral head collected during hip replacement surgery.

For patients with advanced hip joint degeneration visible on pelvic radiographs, joint-preserving surgery is often not an option, making joint replacement the primary treatment choice. However, for those with moderate signs of degeneration, the choice between joint-preserving surgery and replacement can be challenging. This decision often relies on imaging techniques such as preoperative direct MR arthrography.

Recent developments in medical imaging have led to new biochemical MRI sequences, such as dGEMRIC. These sequences are valuable for assessing the condition of cartilage before significant morphologic changes occur. By measuring glycosaminoglycan (GAG) content in cartilage, dGEMRIC provides early insight into cartilage degradation. Incorporating these sequences into standard MRI protocols allows the generation of dGEMRIC indices and the creation of 3D models of hip cartilage, improving the overall assessment of the hip joint.

The purpose of this study is to validate 3D model-based dGEMRIC values by comparing them to histologic assessments of cartilage degeneration. The hypothesis is that the dGEMRIC indices from the 3D MRI model will correlate with the histologic grading of cartilage quality in femoral cartilage samples obtained during hip replacement surgery.

This study aims to enroll 25 patients scheduled for total hip arthroplasty. Each participant will undergo preoperative biplanar hip radiographs and direct MR arthrography at 3 Tesla, including the dGEMRIC sequence, according the hospital's standard protocol.

Surgeries will performed by an experienced orthopaedic hip surgeon. The procedure will involve the femoral neck osteotomy, followed by the removal of the head-neck fragment, and the implantation of the hip prosthesis. Osteochondral samples will be taken from four areas of the femoral head. These will be analyzed using toluidine blue and safranin-O staining to assess cartilage damage.

A validated artificial intelligence algorithm will be used for 3D segmentation, visualization and calculation of morphological and biochemical parameters, which will be compared with histological results to determine a dGEMRIC threshold for identifying cartilage damage.

Inclusion Criteria:

• Patients with advanced hip osteoarthritis.
• Preoperative hip MRI including biochemical sequence (MP2RAGE).
• Indication for hip replacement.

Exclusion Criteria:

• Patients without informed consent.
• Age under 18 years.
• Insufficient language understanding in German, French, or English.
• Previous hip surgeries.
• Neoplastic and inflammatory comorbidities of the hip.
• Post-traumatic or pediatric deformities.
• Avascular necrosis of the femoral head.
• Inadequate MRI image quality (motion artifacts, extra-articular contrast media administration, delay (>45 minutes) between contrast injection and MRI imaging).

Patients in the outpatient clinic who meet the inclusion criteria will be informed about the study during orthopaedic consultations. Screening is not required as all necessary information is available from standard diagnostics. Patients will be provided with study and surgical consent forms to be signed after an informed consent interview with one of the investigators. There is no financial compensation for participation in the study.