Acetabular centre-edge angles revisited: applications and limitations in patients with acetabular dysplasia...

This study evaluates the application and limitations of the acetabular centre-edge angles as described by Wiberg (LCE) and Lequesne (VCA) in a group of adult patients with acetabular dysplasia that were treated with periacetabular osteotomy. Fifty hips in patients with a mean age of 30 years (range, 17-45) were identified and a number of radiographic indices were compared pre and post osteotomy. The potential for measurement variation in both the LCE and VCA angle was evaluated and relationships between the centre-edge angles and other radiographic indices were determined. While all hips displayed some degree of lateral deficiency only 19 (40%) of these cases displayed a ''classic'' lateral and anterior deficiency while 12 (20%) were in fact retroverted. The mean VCA in hips with primarily anterior and lateral deficiency (-6.712.5) was significantly lower (p<0.01) than those with uniform deficiency (5.18.3) or those with retroverted acetabuli (8.913.3). Overall the mean VCA angle of 2.3 (SD12.7) and LCE angle of 3.4 (SD9.3) was corrected to 25.8 (SD11.6) and 28.6 (SD8.7) following osteotomy. The VCA and LCE angles were not correlated (r=0.35) and the LCE angle showed no significant correlation to other lateral coverage indices (Tnnis, Sharp). No correlation was seen either in the post osteotomy values, or in the absolute degree of correction. An alternate VCA (aVCA), identifying the most anterior aspect of the acetabular margin as the reference point, was significantly larger (p<0.001) but did correlate (r=0.77) with the traditional VCA. Potential sources of error in measurement were identified and are reviewed.