No linear correlation between pelvic incidence and acetabular orientation: Retrospective observational study

Analyzing Pelvic Asymmetry by Sex and Ancestry: Insights From an Osteological Collection

INTRODUCTION

Pelvic asymmetry has been noted in pelvic imaging, and might influence the development of various spinal pathologies, most notably scoliosis. There is a limited understanding of the relationship between pelvic asymmetry and sex and ancestry, and limited use of 3D modeling. The purpose of this study was to identify pelvic asymmetry and morphology differences between sex and ancestry utilizing 3D modeling on young adults in an osteological collection.

METHODS

Thirty-three osteological pelvic specimens aged 18-25 years (average age 21.4 ± 2.0 years) were scanned to create virtual 3D models for analysis. Pelvic asymmetry and morphology were measured and compared across sex (male and female) and ancestry (European American and African American). Multivariate regression analysis was performed to examine the relationship between the variables measured.

RESULTS

Multivariate regression analysis demonstrated statistically significant relationships between innominate-pelvic ring ratio and both sex (p < 0.001) and ancestry (p= 0.003) with larger ratios in male and African American specimens respectively. There was also a statistically significant relationship of greater sacral 1 coronal tilt in European American specimens (p= 0.042). There were no statistically significant differences with sex or ancestry in terms of innominate or sacral asymmetry.

CONCLUSION

Although there are differences in overall pelvic shape between sex and ancestry, there is no relationship between these two variables versus pelvic asymmetry in the axial or sagittal planes in young adult osteological specimens.

Assessment of the acetabular version in relation to sagittal sacropelvic parameters

The relationship between acetabular orientation and the sacropelvic parameters is of interest to both hip and spine surgeons as it is increasingly clear disease in one area can affect the other, including the outcome of surgical procedures. The aim of this study was to further clarify the relationship between measures of acetabular orientation and sacropelvic parameters. This study utilized a trauma CT database. A total of 100 scans on adult patients without overt hip or spinal disease were included. Measures of acetabular orientation included the acetabular sagittal angle (ASA) which uses the anterior pelvic plane as a reference and sacroacetabular angle which uses the sacral endplate as a reference (SA); spinopelvic parameters include the pelvic incidence (PI), sacral anatomic orientation (SAO) and pelvic thickness (PTH). Mean age 48.2 years (SD 18.0), 62% male. Mean values were: PI 50.5, SAO 50.7, PTH 106.4 mm, ASA-right 62.1, ASA-left 64.0, SA-right 67.2, and SA-left 65.4. There was substantial correlation between PI and SA (r = 0.628-0.630) and also between SAO and SA (-0.657 to -0.692). Liner regression determined SA was best predicted by the model: SA = 81 × SAO + 0.36 × PI. When using the anterior pelvic plane as a reference to define acetabular orientation, there does not appear to be any significant relationship between the sagittal orientation of the acetabulum and sacropelvic parameters. Using the sacrum as a common point of reference allows some further understanding of the interplay between pelvic parameters and the orientation of the acetabulum.

Lumbosacral Transitional Vertebrae Influence on Acetabular Orientation and Pelvic Tilt

Lumbosacral transitional vertebrae (LSTV) are common congenital variances with a prevalence found in the population up to 35.6%. The literature demonstrates an influence of LSTV on bony pelvic anatomy. The influence on the anatomical acetabular orientation, which is important for cup positioning in total hip arthroplasty, has not yet been described for patients with LSTV. A total of 53 patients with LSTV were identified from a CT Database including 819 subjects. Fifty patients with LSTV could be included and were matched for age and sex against a control group. We examined the influence of LSTV, classified according to Castellvi, on acetabular orientation and pelvic tilt in the supine position. Functional acetabular anteversion and inclination, assessed against the table plane, were compared against anatomical acetabular anteversion and inclination, assessed against the anterior pelvic plane. The anatomical acetabular inclination correlated with the pelvic tilt (r = 0.363, p < 0.001). The anatomical acetabular inclination was significantly larger than the functional acetabular inclination in the supine position (p < 0.001). Castellvi grading of LSTV correlated negatively with pelvic tilt (ρ = −0.387, p = 0.006). Castellvi grading correlated significantly with functional acetabular anteversion (ρ = 0.324, p = 0.022) and anatomical acetabular anteversion (ρ = 0.306, p = 0.022). A higher Castellvi grading was accompanied by a reduced pelvic tilt in the supine position. The functional acetabular anteversion and anatomical acetabular anteversion increased in parallel to the higher Castellvi grading. Therefore, LSTV and Castellvi grading might be assessed on pre-operative X-rays prior to hip arthroplasty and surgeons might consider adjusting cup positioning accordingly.

[Lumbo-pelvino-acetabular alignment-basics and clinical consequences]

The spinal shape and the pelvic ante-/retroversion of an individual are determined by its innate, genetically fixed lumbosacral angulation. This can be measured with little effort in the lateral standing radiograph of the patient. In spinal surgery, there are a lot of original papers on the topic. In hip surgery, however, the individual pelvic version and its consequences for the acetabular orientation have not received the same attention so far.This review focuses on previous data on the relationship between lumbosacral angulation and pelvic ante-/retroversion. Four anatomically definable pelvic types can be distinguished; three of those have to be considered as facultatively pathogenetic. Clinical consequences arise for the clinical pictures of spondylolisthesis, non-specific lower back pain, acetabular retroversion and developmental dysplasia of the hip, as well as for acetabular cup positioning in total hip arthroplasty.