New Radiographic Index for Evaluating Acetabular Version

Abstract

Background Several qualitative radiographic signs have been described to assess acetabular retroversion. However, quantitative assessment of acetabular version would be useful for more rigorous research purposes and perhaps to diagnose and treat hip disorders. Questions/purposes We developed a new quantitative index for acetabular version (p/a ratio). We determined the average p/a, compared it with previous radiographic signs for acetabular retroversion, and evaluated its relationship with anatomic acetabular version. Methods We calculated the p/a ratio by measuring p (distance from acetabular articular surface to posterior wall) and a (distance from acetabular articular surface to anterior wall) on plain hip AP radiographs and dividing p by a. P and a were assessed on the perpendicular bisector of the line between the teardrop and the lateral edge of the acetabulum. Using 185 hip radiographs from patients with suspected idiopathic osteonecrosis, we measured p/a and compared it with previous qualitative signs for acetabular retroversion. Using 62 hip CT images from patients with no osteoarthritis, we measured the anatomic anteversion at the height of the central femoral head and investigated its relationship with p/a. Results The average p/a was 2.05 in 185 hips, and most patients with a p/a greater than 2.05 had a negative qualitative retroversion sign. A correlation was observed between central anteversion and p/a (r = 0.84). Conclusions We believe this ratio can be considered a simple quantitative parameter to assess acetabular version using plain AP radiographs.

Mild or Borderline Hip Dysplasia: Are We Characterizing Hips With a Lateral Center-Edge Angle Between 18° and 25° Appropriately?

“…When defining the limits of normality for the radiographic parameters measured, we used a reference level at or near the 95% CI boundary for normal hip morphology. 5,11,22,43,48 For the FEAR index, we used the cutoff of 5°as described in the original description of the index (Table 2). 53 8 Hip arthroscopic surgery LCEA 18°-25°D wyer et al 10 Hip arthroscopic surgery LCEA 22°-28°F ukui et al 13 Hip arthroscopic surgery LCEA 18°-25°K alore and Jiranek 20 Hip arthroscopic surgery LCEA \25°, Sharp angle \40°, ACEA \25°L arson et al 23 Hip arthroscopic surgery LCEA \25°, Tönnis angle .10°M atsuda et al 29 Hip arthroscopic surgery LCEA 16°-24°M cCarthy and Lee 31 Hip arthroscopic surgery LCEA 22°-28°N awabi et al 34 Hip arthroscopic surgery LCEA 18°-25°R icciardi et al 39 Periacetabular osteotomy LCEA 18°-25°a…”

“…Preoperative anteroposterior pelvic and false profile radiographs were available in all patients, while Dunn lateral radiographs were available in 84% (81/98) of the patients. The following radiographic measurements of acetabular morphology were obtained on the anteroposterior pelvic radiograph: the LCEA of Wiberg, 51 the acetabular inclination angle as described by Tönnis, 47 the AWI and PWI, 43 the posterior to anterior wall (P/A) index, 22 and the FEAR index. 53 The ACEA was measured on the false profile radiograph.…”

Validation of neck axis distance as a radiographic measure for acetabular anteversion

“…Koyama et al . [ 11 ] examined the p/a ratio among a population of patients with idiopathic osteonecrosis. They measured the p/a ratio on digitally reconstructed radiographs and compared this to CT acetabular version.…”

Definition of a quantitative measurement method for acetabular version in a plain radiograph in the healthy adult hip

“…Instead of using a qualitative definition such as anteversion or retroversion, measuring the acetabular version using a quantitative method may provide important advantages. Koyama et al [10] recently defined a new quantitative index for evaluating the acetabular version in a plain radiograph. However, the defined quantitative ratio assesses whether or not an acetabular retroversion exists, not the exact quantity of acetabular version.…”