Characterizing Shape Variations in Infant Hips Using Statistical Shape Modeling for Ultrasonic Diagnosis of Hip...

Area of Science:

• Medical imaging
• Orthopedics
• Biomechanical analysis

Background:

• Developmental dysplasia of the hip (DDH) in infants is diagnosed using Graf's alpha (α) angle via 2D ultrasound (US).
• The unidimensional Graf method may not capture complex iliac wing and bony acetabular roof (IW-AR) coronal outline variations influencing DDH.
• Understanding IW-AR shape variability is crucial for accurate DDH assessment.

Purpose of the Study:

• To analyze the mean shape and variations of infant hip IW-AR coronal outlines using ultrasound images.
• To investigate the impact of IW-AR shape variations on the Graf's α angle variability.
• To develop a statistical shape model (SSM) for characterizing IW-AR outlines.

Main Methods:

• Segmentation of 510 infant hip US images to extract IW-AR outlines in Graf's standard plane.
• Development of a statistical shape model (SSM) to analyze outline shapes and variations.
• Quantification of shape variations using global and local shape modes.

Main Results:

• A compact SSM effectively modeled IW-AR outline variations using a few global and local shape modes.
• Global shape modes significantly influenced the α angle across a wide range (38°-70°).
• Local shape modes, while having a smaller impact (up to 6°), may be relevant for DDH diagnosis and clinical outcomes.

Conclusions:

• IW-AR shape variations can be effectively modeled by SSMs, highlighting both global and local contributions.
• The influence of local shape modes on α angle variability in DDH assessment should not be underestimated.
• Advanced shape analysis provides a more comprehensive understanding of hip joint morphology in infants.