Novel CT-based three-dimensional software improves the characterization of cam morphology

Area of Science:

• Orthopedic surgery
• Medical imaging
• Biomechanical analysis

Background:

• Femoroacetabular impingement (FAI) revision surgery often results from incomplete correction of femoral offset and sphericity.
• Accurate preoperative assessment of hip morphology is crucial due to the technical challenges of arthroscopic exploration.

Purpose of the Study:

• To characterize cam deformity size and location using prototype CT-based software.
• To compare alpha angles from the software with those from plain radiographs and CT scans.
• To determine if measurement location variations explain differences in alpha angles.

Main Methods:

• Retrospective review of 100 preoperative plain radiographs and CT scans from patients with symptomatic cam lesions.
• Measurement of alpha angle and clockface location using novel CT-based software, CT, and Dunn lateral radiographs.
• Ordinary least squares regression analysis to assess the relationship between alpha angle and measurement location.

Main Results:

• The software identified a mean alpha angle of 70.8° at 1:23 o'clock, with 60% of maximum angles between 12:45 and 1:45.
• CT and plain radiographs underestimated alpha angles by 5.7° and 8.2°, respectively.
• Software-based measurements were anterosuperior to CT and radiograph locations; regression confirmed correlation between angle differences and measurement locations.

Conclusions:

• Three-dimensional (3-D) software-based imaging yields larger alpha angles than conventional radiographs and CT.
• Differences in measured alpha angles are attributed to variations in measurement location.
• Automated 3-D assessment is necessary for precise characterization of preoperative FAI deformity.