Relationship between Sacral Pelvic Incidence and Acetabular Orientation

Abstract

The importance of the sacral pelvic incidence (SPI) in relation to individual variations of sagittal spinal curvature has become well-recognised. We attempted to determine the relationship between SPI and acetabular orientation. The three-dimensional coordinates of 47 homologous points were observed on 51 adult anatomical pelvises (26 female and 25 male). The reference vertical plane was Lewinnek's anterior pelvic plane. 10 angular parameters and 11 linear parameters were defined and calculated. These were expressed both in absolute value (in millimetres) and in "acetabular unit" (relative to the mean value of the right and left acetabular rays). Mean values of the parameters were calculated for all pelvises and according to gender. There were two dominant parameters: the "sacral slope" and the "V pubic angle". "Acetabular tilting" was primarily dependent on the "sacral slope" and its intermediary on the "SPI", while "acetabular anteversion" dependent on the "V pubic angle" via the "angle of prow". It is recommended that positioning of the acetabular cup in total hip arthroplasty relates to anatomical parameters, and to the global sagittal balance of the pelvi-spinal unit.

Sexual Dimorphism of Acetabular Anatomy Based on Three-dimensional Computed Tomography Images of Pelvises

“…Assessment of acetabula relative to inner parameters of the pelvis rather than the patient's standing position aimed to eliminate external factors and place the focus on differences in the anatomy and orientation of acetabula themselves. Therefore, the sacrum base plane was accepted as the plane of reference since it represents a stable element of reference and the relation between the position of the base of the sacral bone and the hips is constant [11,[21][22][23][24]. In view of the on-going discussion on the incidence angle of the pelvis, the above-presented plane of reference seems even more important [21][22][23][24].…”

“…Tylko obliczenia w oparciu o rzeczywiste modele trójwymiarowe pozwolą znacznie ograniczać błąd pomiaru. Normy dotyczące orientacji prze strzennej panewek nie są jednak wystarczająco określone i często opierają się o płaszczyzny, których dokładność wyznaczania jest niepewna [4][5][6][7][8]11,[20][21][22][23][24]. Równocześnie różnice w strukturze i ustawieniu panewek stawu biodrowego w zależności od płci, choć już opisywane, wymagają nadal uwierzytelnienia naukowego [5][6][7][8], co istotnie może wpłynąć na zrozumienie problemu klinicznego i pośrednio na jakość wykonywanych zabiegów ortopedycznych.…”

“…Ocena panewek w stosunku do wewnętrznych parametrów miednicy, a nie w stosunku do pozycji stojącej człowieka, miała na celu wyłączenie czynników zewnętrznych i skupieniu się na różnicach w budowie i orientacji panewek per se. Jako płaszcyznę odniesienia wykorzystano więc podstawę kości krzyżowej, gdyż stanowi ona stabilny element odniesienia, a stosunek pomiędzy pozycją pod stawy kości krzyżowej a stawami biodrowymi jest stały [11,[21][22][23][24]. W świetle toczącej się dziś dyskusji na temat kąta incydencji miednicy, wydaje się, że zaprezentowana tu płaszczyzna odniesienia jest tym ważniejsza [21][22][23][24].…”

“…The measurement error may only be significantly reduced if calculations are based on actual three-dimensional models. However, the norms for spatial orientation of the acetabulum have not been determined sufficiently precisely and are based on planes the determination of which is of uncertain accuracy [4][5][6][7][8]11,[20][21][22][23][24]. At the same time, sex differences in the anatomy and orientation of the acetabulum, while already described, still require scientific evidence to be regarded as reliable [5][6][7][8], which may have a significant impact on the understanding of this clinical problem and, indirectly, on the quality of orthopaedic surgeries being performed.…”

Relationship Between Pelvic Tilt and Lumbar Disc Degeneration

“…6) Position of the acetabulum relates to the global sagittal balance of the spino-pelvic unit. 7) So pelvic tilt is a www.krspine.org 177 important parameter which determines relation between axial spine and lower limbs.…”