Three-Dimensional Quantification of Cam Resection Using MRI Bone Models: A Comparison of 2 Techniques

Area of Science:

• Orthopedic surgery
• Medical imaging
• Biomechanical analysis

Background:

• Current radiographic methods for evaluating cam deformity in femoroacetabular impingement syndrome (FAIS) have limitations in quantifying complex 3D proximal femur morphology.
• Advanced imaging techniques are needed to provide more precise measurements for FAIS evaluation and treatment.

Purpose of the Study:

• To compare magnetic resonance imaging (MRI)-based metrics for quantifying cam resection using the best-fit sphere alpha angle (BFS-AA) method versus 3D preoperative-postoperative surface model subtraction (PP-SMS).

Main Methods:

• Seven cadaveric hemipelvises underwent MRI before and after arthroscopic femoral osteochondroplasty.
• 3D bone models were reconstructed, and alpha angles were measured using the BFS-AA method.
• Cam resection was quantified using BFS-AA and PP-SMS metrics (surface area, volume, maximum/mean height).
• Bivariate correlation analyses compared the quantification methods.

Main Results:

• Both BFS-AA and PP-SMS methods demonstrated strong positive correlations in quantifying cam resection.
• Specific correlations: FSA (r=0.817), FV (r=0.888), FHmax (r=0.786), and FHmean (r=0.679).
• Mean alpha angle decreased from 59.73° to 48.02° postoperatively.

Conclusions:

• The BFS-AA and PP-SMS methods provide reliable and comparable quantification of cam resection in FAIS.
• These MRI-based techniques offer valuable tools for both preoperative planning and postoperative assessment of surgical outcomes.