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. 2016 Feb;12(1):32-8.
doi: 10.1007/s11420-015-9472-6. Epub 2015 Oct 19.

Anteroposterior Radiographs Are More Accurate than Cross-Table Lateral Radiographs for Acetabular Anteversion Assessment: a Retrospective Cohort Study

Peter K Sculco  1 , Alexander S McLawhorn  1 , Kaitlin M Carroll  1 , Benjamin A McArthur  2 , David J Mayman  1
Affiliations

Anteroposterior Radiographs Are More Accurate than Cross-Table Lateral Radiographs for Acetabular Anteversion Assessment: a Retrospective Cohort Study

Peter K Sculco et al. HSS J. 2016 Feb.

Abstract

Background: Measuring acetabular anteversion is relevant to routine follow-up of total hip arthroplasties (THAs) and for malfunctioning THAs. Imageless navigation facilitates acetabular component orientation relative to the anterior pelvic plane (APP) or to the APP adjusted for sagittal pelvic tilt (PT). The optimal plain radiographic method for the postoperative assessment of anteversion is not agreed upon.

Questions/purposes: (1) Do anteversion measurements on plain radiographs correlate more with APP anteversion or PT-adjusted anteversion? (2) Do measurements of anteversion performed on supine anteroposterior (AP) radiographs more accurately reflect intraoperative anteversion values for navigated THA compared to anteversion measured on cross-table lateral (CL) radiographs?

Methods: Seventy patients receiving primary navigated THA were included. APP and PT-adjusted anteversion were recorded; the latter defined the intraoperative target for anteversion. Postoperative anteversion was measured on supine AP pelvis radiographs with computer software and CL radiographs with conventional methods. Intraoperative measurements were used as the reference standards for comparisons.

Results: Mean intraoperative APP anteversion was 20.6° ± 5.6°. Mean intraoperative PT-adjusted anteversion was 22.9° ± 4.5°. Mean anteversion was 22.7° ± 4.7° on AP radiographs and 27.2° ± 4.2° on CL radiographs (p < 0.001). Only correlations between PT-adjusted anteversion and radiographic assessments of anteversion were significant. The mean difference between PT-adjusted anteversion and anteversion on AP radiographs was -0.2° ± 4.3°, while the mean difference between the PT-adjusted anteversion and anteversion measured on CL radiographs was 4.3 ± 5.1° (p < 0.001).

Conclusion: Plain film assessment of anteversion was more accurate on supine AP radiographs than on CL radiographs, which overestimated acetabular anteversion.

Keywords: anteversion; computer-assisted surgery; diagnostic imaging; radiographic film; total hip replacement.

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Figures

Fig. 1
Fig. 1
A cross-table lateral radiograph of the patient from Fig. 1 is shown, illustrating the Woo and Morrey [28] method for assessing acetabular anteversion. The angle subtended by a vertical line and a second line parallel to the long axis of the ellipsoid projection of the component rim onto the plane of the radiograph is measured. In this case, acetabular anteversion measured 30°.
Fig. 2
Fig. 2
A supine anteroposterior pelvis radiograph with Ein-Bild-Röntgen-Analyse (EBRA; University of Innsbruck, Austria) grid lines and landmarks is shown. A horizontal baseline was set tangent to the transverse axis of the pelvis in the coronal plane; then, additional vertical grid lines were used to delineate the left and right inner boundaries of the pelvic brim, the medial boundary of the ipsilateral obturator foramen, and the pubic symphysis. Two more horizontal lines were used to delineate the superior and inferior boundaries of the pelvic brim. Multiple reference points were selected along the radiographic projections of the femoral head, the hemispherical contour of the acetabular component, and the acetabular rim. As determined by the EBRA software, acetabular component inclination was 43°, and anteversion was 22°.
See this image and copyright information in PMC

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