Anatomical changes in the pelvis after modified Chiari pelvic osteotomy

Area of Science:

• Orthopedic Surgery
• Radiology
• Biomedical Engineering

Background:

• Plain X-ray analysis of pelvic osteotomies is limited to the frontal plane.
• Chiari pelvic osteotomy aims to improve acetabular coverage for hip joint stability.
• Three-dimensional (3D) pelvic changes after osteotomy require advanced imaging techniques.

Purpose of the Study:

• To investigate 3D pelvic anatomical changes following Chiari pelvic osteotomy.
• To quantify fragment displacement and rotation in the sagittal and horizontal planes.
• To assess the impact of these changes on acetabular coverage of the femoral head.

Main Methods:

• Computed tomography (CT) scans of 22 patients before and after Chiari pelvic osteotomy.
• Analysis of 3D pelvic geometry, including fragment displacement (medialization/lateralization) and rotation.
• Superimposition of acetabular and femoral head regions to quantify coverage changes.

Main Results:

• Medial displacement of the distal fragment (average 0.4 cm) and lateral displacement of the proximal fragment (average 0.8 cm) were observed.
• Anterior/posterior displacement and anterior rotation of the distal fragment occurred.
• Acetabular coverage improved by approximately 30% anteriorly and 20% posteriorly, primarily attributed to proximal fragment lateralization.

Conclusions:

• Chiari pelvic osteotomy induces significant 3D pelvic remodeling.
• Proximal fragment lateralization is the key factor enhancing acetabular coverage of the femoral head.
• 3D CT analysis provides a comprehensive understanding of pelvic biomechanics post-osteotomy.