Validation of CT image-based software for three-dimensional measurement of acetabular coverage profile.

BACKGROUND: Plain radiography, 2-dimensional (2D) magnetic resonance imaging (MRI), and computed tomography (CT) do not precisely display morphology and acetabular coverage in developmental dysplasia of the hip or pincer-type femoroacetabular impingement. Pelvic position and pelvic tilt affect assessment of the acetabular parameters, leading to misinterpretation.

OBJECTIVE: We tested a 3-dimensional (3D) CT evaluation script to calculate the crossover sign (COS), acetabular coverage and morphology.

METHODS: To test the method, we constructed a phantom pelvic model, in which the acetabulum was mounted at different coverages of the femoral head, and simulated a COS and the acetabular morphology. Additionally we examined the reliability and objectivity of this method in ten patients with CT scans of the pelvis for conditions unrelated to hip disorders.

RESULTS: We obtained an average accuracy of the 3D CT evaluation script of -0.37∘ (range -3.84 to 3.88; SD ± 1.43) for morphology, and 0.002% (range -7.28% to 6.90%; SD ± 1.60%) for coverage of the femoral head. Significant correlation between the expected and calculated COS (p= 0.01) was found.

CONCLUSIONS: Our 3D CT evaluation script permits precise evaluation of the acetabular coverage profile, the presence or absence of a COS and acetabular morphology, independent of patient positioning or pelvic tilt.