The goal of this observational study is to learn how four acetabular osteotomy techniques change the shape of the hip socket in children and adolescents with developmental dysplasia of the hip or residual acetabular dysplasia.

The main questions it aims to answer are:

How do virtual Salter, Dega, San Diego, and Pemberton osteotomies differ in acetabular volume and surface shape on participant-specific three-dimensional models? How closely does the virtual result of the osteotomy actually performed match the early postoperative magnetic resonance imaging (MRI)?

Participants will have a three-dimensional pelvis-acetabulum model created from preoperative MRI. Researchers will perform virtual Salter, Dega, San Diego, and Pemberton osteotomies on that model and measure the resulting acetabular morphology. The virtual result of the osteotomy actually performed will then be compared with the participant's early postoperative MRI.

This is a single-center, prospective, observational methodological validation study in children and adolescents with developmental dysplasia of the hip or residual acetabular dysplasia who are undergoing Salter, Dega, San Diego, or Pemberton acetabular osteotomy.

The study has two linked analytical components. First, participant-specific three-dimensional pelvis-acetabulum models will be generated from preoperative MRI obtained within 6 weeks before surgery. Standardized virtual Salter, Dega, San Diego, and Pemberton osteotomies will then be applied on each participant's preoperative model to compare the expected effect of each technique on acetabular volume, surface area, coverage distribution, and other predefined three-dimensional morphometric parameters.

Second, early postoperative MRI obtained 3 to 8 weeks after surgery will be used to derive actual postoperative three-dimensional morphology. The virtual output corresponding to the osteotomy actually performed clinically will then be compared with the postoperative MRI-derived morphology to quantify prediction accuracy using absolute difference, bias, and Bland-Altman limits of agreement.

Additional analyses will compare validation performance by osteotomy type, assess interobserver and intraobserver reliability, measure workflow feasibility, and explore associations between preoperative morphometric markers and prediction error.

Inclusion Criteria:

1. Age 2 to 18 years
2. Developmental dysplasia of the hip or residual acetabular dysplasia
3. Primary Salter, Dega, San Diego, or Pemberton acetabular osteotomy planned at Istanbul University, Istanbul Faculty of Medicine
4. Preoperative hip MRI available within 6 weeks before surgery
5. Early postoperative hip MRI available 3 to 8 weeks after surgery
6. MRI quality adequate for three-dimensional morphometric analysis
7. Unilateral or bilateral cases eligible

Exclusion Criteria:

1. Hip pathology not related to developmental dysplasia of the hip, including Perthes disease, slipped capital femoral epiphysis, neuromuscular dysplasia, or infection/trauma sequelae
2. Previous surgery on the same hip that significantly alters anatomy, including prior pelvic or femoral osteotomy or open reduction, or current metal implant/fusion
3. MRI contraindication or safety issue, including MR-incompatible implant/device, severe claustrophobia, or a medical barrier to sedation/anesthesia
4. MRI not compatible with protocol or inadequate for analysis

Children and adolescents with developmental dysplasia of the hip or residual acetabular dysplasia who are scheduled for primary Salter, Dega, San Diego, or Pemberton acetabular osteotomy at Istanbul University, Istanbul Faculty of Medicine

De-identified individual participant data are not planned to be shared with other researchers. Any future sharing would require additional review of participant confidentiality protections, institutional policy, and ethics approval. Aggregate study results may be reported in scientific publications and presentations.