Computer assisted determination of acetabular cup orientation using 2D-3D image registration

Area of Science:

• Medical Imaging
• Orthopedic Surgery
• Biomedical Engineering

Background:

• Existing 2D-3D image-based registration methods for acetabular cup orientation in total hip arthroplasty (THA) require prosthesis CAD models and multiple radiographs.
• These requirements limit clinical application, especially in retrospective studies, due to proprietary concerns and data availability.

Purpose of the Study:

• To develop a new method for determining post-operative cup orientation that overcomes the limitations of existing 2D-3D registration techniques.
• To enable accurate measurement of acetabular cup orientation, pelvic tilt, and rotation without requiring CAD models or multiple radiographs.

Main Methods:

• A novel formulation coupling radiographic measurement with 2D-3D image matching was developed.
• A hybrid 2D-3D registration scheme, combining landmark-to-ray alignment and intensity-based registration, was employed.
• The method was validated using 2D adult cadaver hips.

Main Results:

• The hybrid 2D-3D registration scheme achieved a mean accuracy of 1.0 +/- 0.7 degrees for inclination and 1.7 +/- 1.2 degrees for anteversion.
• Measurements were validated against post-operative CT images, serving as the ground truth.
• The method demonstrated high precision in estimating cup orientation.

Conclusions:

• The proposed solution formulation and hybrid 2D-3D registration scheme effectively estimate post-operative cup orientation.
• The method facilitates accurate measurement of pelvic tilt and rotation.
• This advancement addresses key limitations in current clinical practice for THA outcome assessment.