A Quantitative Method to Assess Focal Acetabular Overcoverage Resulting From Pincer Deformity Using CT Data

Abstract

Background Current assessment techniques for focal acetabular overcoverage are neither consistent nor quantitatively accurate. Questions/purposes We propose: (1) a method to precisely quantify the amount of focal acetabular overcoverage in a patient's pincer deformity based on CT data; (2) to evaluate the consistency of this method; and (3) to compare the method with conventional radiographic assessments.Methods We developed a method to assess focal acetabular overcoverage using points selected from CT scans along the acetabular rim after realigning the pelvis into a neutral position. Using four resampled and segmented pelvic CT scans of cadaveric specimens with virtually induced impingement, two observers independently tested the algorithm's consistency. Our algorithm assessed the amount of focal acetabular overcoverage using CT data and projected data from reconstructed radiographs. Results (1) We successfully showed the feasibility of the software to produce consistent, quantitative measurements. (2) Testing showed the average difference between observers in aligning the pelvis was 0.42°, indicative of a consistent approach. (3) Differences between measurements on three-dimensional (3-D) CT and simulated radiographs were significant. Conclusions The proposed method represents a new avenue in consistently quantifying focal acetabular overcoverage using CT models while correcting for pelvic tilt and rotation. Our analysis confirms AP hip radiograph simulations overestimate the amount of overhanging acetabular rim in a pincer deformity. Clinical Relevance This technique has potential to improve preoperative diagnostic accuracy and enhance surgical planning for correction of a pincer deformity resulting from focal acetabular overcoverage.

The Effect of Pelvic Tilt on Radiographic Markers of Acetabular Coverage

“…Using these techniques, acetabular coverage has been characterized in cadaveric specimens with high interobserver reliability (intraclass correlation coefficient of 0.98). 11 These results suggest that CT may be a more reliable method to definitively quantify acetabular coverage in the setting of FAI.…”

Variability of Acetabular Coverage Between Supine and Weightbearing Pelvic Radiographs

“…These modalities are reported to exhibit superior interobserver reliability (intraclass correlation coefficient = 0.98) and may be a more reliable method to quantify acetabular coverage in the setting of FAI. 10 We recognize limitations to this study. The population of young adults with hip pain represents a diverse spectrum of acetabular morphologic characteristics.…”

Bony abnormalities of the hip joint: a new comprehensive, reliable and radiation-free measurement method using magnetic resonance imaging

“…Specific guidelines have been developed to assess pelvic orientation prior to performing measurements of acetabular coverage using radiographs. (15) Methods to correct pelvic orientation using CT have been introduced, (16) but are not widely used. The 3D nature of MRI allows for standardization of pelvic orientation using specific bony landmarks after images have been acquired, however methods to standardize pelvic orientation have not been described in previous studies using MRI.…”