Single-baseline virtual progression modeling of Crowe type I-III developmental dysplasia of the hip: a finite element study of stress-location migration.

BACKGROUND: Developmental dysplasia of the hip alters acetabular morphology and load transfer, but classification-related changes in local stress distribution remain incompletely understood.

METHODS: A Crowe type I finite element model was directly reconstructed from one patient's pelvic computed tomography data. Crowe type II and III models were subsequently generated from the same anatomical baseline as standardized, classification-consistent virtual morphologies rather than independent patient-specific cases. This single-baseline, internally controlled design was used to reduce inter-individual anatomical variability and evaluate morphology-related changes in stress distribution and load-transfer pathways. A simplified 600 N axial load was applied to compare peak von Mises stress and stress distribution in the acetabular-side pelvic bone, acetabular/pseudoacetabular cartilage, proximal femur, and femoral head cartilage. To assess the influence of the simplified loading assumption, an additional loading-sensitivity analysis was performed using a 1,888 N resultant force inclined medially by 16° from the global vertical direction in the frontal plane.

RESULTS: Peak stress within the acetabular-side pelvic bone region increased from Crowe type I to III (2.41, 5.79, and 6.71 MPa, respectively), whereas acetabular/pseudoacetabular cartilage stress peaked in type II (3.54 MPa). Femoral head cartilage stress increased progressively from 1.23 MPa in type I to 2.08 MPa in type II and 3.42 MPa in type III. High-stress regions migrated from the superior true acetabulum to the true acetabulum-pseudoacetabulum transition region and then to the localized pseudoacetabular load-bearing region. Under the alternative loading scenario, the principal classification-dependent stress relationships and pelvic-side stress-location migration pattern were maintained. Material-property sensitivity analyses produced peak-stress changes of no more than 2.46% and similarly preserved these patterns.

CONCLUSION: Across the standardized Crowe type I-III virtual models, increasing classification severity was associated not only with changes in stress magnitude but also with spatial migration of the principal load-bearing regions. These findings provide an internally controlled biomechanical reference for understanding classification-related load-transfer patterns but should not be interpreted as patient-specific predictions or population-level stress thresholds. Independent patient datasets are required to validate these hypothesis-generating observations before clinical application.