No linear correlation between pelvic incidence and acetabular orientation

Abstract

Links between sagittal spinal alignment and acetabular orientation attract considerable research attention with the goal of understanding “hip-spine syndrome.” However, whether pelvic incidence (PI) is related to acetabular orientation remains debatable. The purpose of the present study was to determine whether the correlation between PI and acetabular orientation is present in pelvises of young healthy adults, and whether the correlation is present in subgroups of sex, or between the left and right pelvis. We analyzed 100 abdominopelvic computed tomography (CT) scans of skeletally healthy young adults. We measured PI and acetabular orientation with three-dimensional (3D) measurements. The orientation of 200 acetabula was measured using 3D reconstructed models of 100 pelvises in the coordinate system based on the anterior pelvic plane (APP). To quantify the acetabular orientation, the radiographic definitions of anteversion and inclination were used. To examine the correlation between acetabular orientation and PI, Pearson's correlation was used. The mean PI was 46.9° ± 10.2°, and the mean acetabular orientation 15.3° ± 5.7° anteverted and 37.5° ± 3.9° inclined. While no significant difference in the PI was observed, the average acetabular orientation of female pelvises (anteversion, 17.5° ± 5.6°; inclination, 36.7° ± 3.7°) was more anteverted and less inclined compared to that of male pelvises (anteversion, 13.2° ± 4.9°; inclination, 38.3° ± 3.9°, respectively; P values < .05). The correlation between PI and acetabular orientation was statistically not significant. After division of study group by sex, the linear correlation between PI and acetabular orientation was not statistically supported. The asymmetry of the acetabular orientation between the left and right sides was not significant. The linear relationship between anatomical acetabular orientation and PI was not evident in the normal population. Our finding thus proves the absence of a linear relationship between the upper and lower articular orientation of the pelvic segment and deepens the understanding of the characteristics of acetabular orientation and PI.

Lumbosacral Transitional Vertebrae Influence on Acetabular Orientation and Pelvic Tilt

“…LSTV were associated with an increased pelvic incidence compared to control group, which significantly determined the pelvic geometry as presented by Haffer et al [ 6 ]. In line with the literature in our study, no correlation between acetabular orientation and pelvic incidence for the control group was observed [ 32 ]. Furthermore, for patients with LSTV, no correlation between pelvic incidence and acetabular orientation was found.…”

Assessment of the acetabular version in relation to sagittal sacropelvic parameters

“…CT scans were utilized in 2‐dimensions and arguably advanced 3‐dimension analysis may be more accurate (Lee et al, 2019). However, despite using 2‐dimensional analysis, we were able to validate findings from others that have utilized more advanced assessments (Kim et al, 2021). The scans assessed were also taken supine which arguably limits their clinical application—however, the measurement of fixed parameters in our experience and that of others remains more accurate on CT than plain radiographs.…”

“…They failed to find any relationship between either PI or sacral slope and the sagittal orientation of the acetabulum indicating significant variation between individuals. Kim et al developed a 3‐dimensional model based on 100 male and 50 female pelves to study the relationship between PI and both acetabular anteversion and inclination (Kim et al, 2021 ). The APP was defined, and the axial plane of the pelvis defined as perpendicular to the APP.…”

“…As a result of this interplay between the spine, pelvis and hip, attention has been given to analysis of the PI, and determining whether PI is associated with the normal orientation of the acetabulum—results have been variable. In part this is due to different techniques being utilized including analysis of 2‐dimensional and 3‐dimensional computed tomography (CT) imaging, magnetic resonance imaging with arthrography and plain radiographs (Hatem et al, 2020 ; Kim et al, 2021 ; Lee et al, 2019 ; Radcliff et al, 2014 ). Measures to define the sagittal orientation of the acetabulum have also varied meaning comparison of studies has been challenging if not impossible.…”

Lumbo-pelvino-azetabuläres Alignment – Grundlagen und klinische Konsequenzen

“…Hier gibt es Hinweise, dass Beckenformen mit niedriger Pelvic Incidence zur azetabulären Retroversion neigen, während solche mit hoher Pelvic Incidence stärker antevertierte Pfannen aufweisen und damit die azetabuläre Anteversion der kongenitalen Hüftdysplasie verstärken können [10,17,24,32]. Eine lineare Korrelation zwischen der Pelvic Incidence und der azetabulären Orientierung wird jedoch bestritten [11]. In klinischen Arbeiten war zu beobachten, dass Patienten mit einer symptomatischen azetabulären Retroversion überwiegend niedrige Pelvic Incidences aufweisen [10,17], dass es jedoch auch Patienten mit symptomatischer azetabulärer Retroversion und normaler Pelvic Incidence gibt [10].…”