Geometric Transformation Algorithm for Acetabular Cup Orientation: Converting 2D Radiographic Projections to 3D...

Area of Science:

• Orthopedic surgery
• Medical imaging
• Computer vision

Background:

• Total hip arthroplasties are common, but inadequate acetabular cup positioning causes complications.
• Accurate measurement of cup inclination and anteversion is crucial for optimal surgical outcomes.
• Existing measurement systems often require extra hardware, specialized training, or lack integration.

Purpose of the Study:

• To develop and validate software for automated measurement of acetabular cup positioning.
• To compare the software's performance against standard computer-aided design (CAD) measurements.
• To enhance the accuracy and efficiency of postoperative assessments in hip replacements.

Main Methods:

• Developed Python-based software using computer vision for edge detection and ellipse fitting.
• Analyzed standard anteroposterior (AP) X-ray images of a pelvic phantom with a conventional acetabular cup.
• Validated the software against MediCAD (CAD software) measurements, using intraclass correlation coefficient (ICC).

Main Results:

• Analyzed 140 AP X-ray images.
• Inclination averaged 50.69°±15.86° (software) vs. 49.40°±15.24° (CAD).
• Anteversion averaged 14.36°±9.08° (software) vs. 14.75°±8.88° (CAD).
• Achieved excellent agreement: ICC=0.994 for inclination and ICC=0.992 for anteversion (p<0.001).

Conclusions:

• The computer-assisted measurement technique shows excellent concordance with standard methods.
• The software offers workflow advantages for automated spatial positioning recognition.
• Future work includes enhancing automation, validating on diverse populations/implants, and comparing with 3D CT measurements.