Measuring Acetabular Version after Total Hip Arthroplasty: A Comparison of Two Radiographic Methods.

The objective of the present work was to compare the measurement of acetabular component version on anteroposterior (AP) and on cross-table radiographs after total hip arthroplasty (THA).  Radiographs of 60 hips with a primary THA were selected. Version was calculated on the AP radiograph using the Lewinnek method and, on the cross-table, using the Woo and Morrey direct method.  Mean and standard deviation (SD) were different on both radiographs, being 9.7° ± 5.5° on the AP, whereas in the cross-table the measurements were 20.6° ± 8.4° (  < 0.001). Minding our aim of 10°, the cross-table measurements were statistically different from it (  < 0.001), while the AP measurement did not differ (  = 0.716).  The present study showed that the best way to correctly evaluate the acetabular component positioning following a THA is by measuring anteversion and abduction on an AP radiograph after confirming, in a cross-table radiograph, that the component is not retroverted.