Does hemipelvis structure and position influence acetabulum orientation?

Abstract

BackgroundAlthough acetabulum orientation is well established anatomically and radiographically, its relation to the innominate bone has rarely been addressed. If explored, it could open the discussion on patomechanisms of such complex disorders as femoroacetabular impingement (FAI). We therefore evaluated the influence of pelvic bone position and structure on acetabular spatial orientation. We describe this relation and its clinical implications.MethodsThis retrospective study was based on computed tomography scanning of three-dimensional models of 31 consecutive male pelvises (62 acetabulums). All measurements were based on CT spatial reconstruction with the use of highly specialized software (Rhinoceros). Relations between acetabular orientation (inclination, tilt, anteversion angles) and pelvic structure were evaluated. The following parameters were evaluated to assess the pelvic structure: iliac opening angle, iliac tilt angle, interspinous distance (ISD), intertuberous distance (ITD), height of the pelvis (HP), and the ISD/ITD/HP ratio. The linear and nonlinear dependence of the acetabular angles and hemipelvic measurements were examined with Pearson’s product − moment correlation and Spearman’s rank correlation coefficient. Correlations different from 0 with p < 0.05 were considered statistically significant.ResultsComparison of the axis position with pelvis structure with orientation in the horizontal plane revealed a significant positive correlation between the acetabular anteversion angle and the iliac opening angle (p = 0.041 and 0.008, respectively). In the frontal plane, there was a positive correlation between the acetabular inclination angle and the iliac tilt angle (p = 0.025 and 0.014, respectively) and the acetabular inclination angle and the ISD/ITD/HP ratio (both p = 0.048).ConclusionsThere is a significant correlation of the hemipelvic structure and acetabular orientation under anatomic conditions, especially in the frontal and horizontal planes. In the anteroposterior view, the more tilted-down innominate bone causes a more caudally oriented acetabulum axis, whereas in the horizontal view this relation is reversed. This study may serve as a basis for the discussion on the role of the pelvis in common disorders of the hip.

Variation in pelvic shape and size in Eastern European males: a computed tomography comparative study

“…Our measurements were performed using an original method of evaluation based on 3D CT reconstruction, a precise measurement tool whose reliability has been confirmed by previous studies (Jóźwiak et al, 2015; Musielak et al, 2016) as well as by high ICC values for intra- and inter-rater reliability. Geometric morphometric analysis was also carried out on 3D CT pelvis reconstructions using the Thin Plate Spline function, which enabled the interpolation of semilandmarks between the template and each sample.…”

“…We therefore considered it appropriate to define and precisely measure these distances to obtain high-quality results. All of the above-mentioned parameters were used recently by Musielak et al (2016) to evaluate the intrinsic relationship between the structures and positions of the pelvis and acetabulum.…”

“…The results of our study may help in the interpretation of functional variation of the pelvis due to different physical activities and body mass. Moreover, specific variations in the pelvic shape are associated with hip pain and its pathologies (Lewis et al, 2017); thus, understanding the influence of body mass on the pelvic shape may help in medical studies (e.g., Musielak et al, 2016). In order to achieve the main purposes presented above, we analyzed CT images of pelvic bones, using traditional measurements and geometric morphometrics.…”

Retroversion of the hemipelvis rather than hypoplastic posterior wall decreases acetabular anteversion in hips affected by Perthes disease

“…The results showed that both measurements had good reliability for one observer and between observers, and simultaneously using the IWAA and the AWDI has good predictive value for the AAA. Similar to this study, Musielak et al 32 used the iliac opening angle to indicate the opening direction of the hemipelvis in the horizontal plane, but the morphological analysis of the open angle of the ilium for the acetabulum part of the hemipelvis was insufficient. Fuji et al 33 also analyzed the rotation of the ilium on three levels, but his measurement method failed to analyze the influence of the development of the anterior and posterior walls of the acetabulum on the acetabular opening.…”

“…This suggests that acetabular retroversion in Perthes disease may be caused by hemipelvic retroversion. Musielak et al 32 also found that the structure of the hemipelvis is closely related to the direction of the acetabulum, and the acetabulum will also be rotated back in proportion when the hemipelvis is rotated back in the horizontal plane. In this study, the AAA of the affected side of the case group was smaller than that of the contralateral side, and the IWAA of the affected side was smaller than that of the contralateral side.…”