The association between sacral morphology and sacroiliac joint conformity demonstrated on CT‐based bone models

Abstract

IntroductionKnowledge of the stress distribution on structures around the sacroiliac joint (SIJ) is required to treat or prevent SIJ disorders. The purpose of this study was to reveal the association between sacral morphology and SIJ conformity.Materials and methodsThis cross‐sectional study included 11 adult patients with unilateral SIJ pain who underwent computed tomography (CT) imaging of the pelvis. Bony coordinate systems for the sacrum and innominates were embedded using anatomical landmarks. Local coordinate systems for the auricular surfaces of the sacrum and innominate were also defined. Conformity of the SIJ was quantified by the offset of the coordinate systems between the auricular surfaces of the sacrum and innominate. Repeated measure ANOVA and multiple regression analysis were used for statistical analyses.ResultsThere were large variations across subjects in sacral morphology and SIJ conformity. There were no differences in any of the six degrees‐of‐freedom positions or orientations of the bilateral sacral and innominate auricular surfaces between the symptomatic and asymptomatic sides. The SIJ downward rotation on the asymptomatic and symptomatic sides were 0.0 [−1.0, 1.1]° and 2.1 [1.2, 3.0]°, respectively. Smaller downward rotation of the sacral auricular surface based on the sacral bony coordinate system had significant association with the greater SIJ downward rotation (standard partial regression coefficient: −.44, p = .043).ConclusionsThe results indicate that the morphology of the sacrum is associated with poor SIJ conformity and that separation of the superior portion of the SIJ can be a risk factor for SIJ pain.

Auricular surface morphology and surface area does not influence subchondral bone density distribution in the dysfunctional sacroiliac joint

“…This draws the ilia and sacrum firmly together via the “force‐closure” and “form‐closure” phenomena (Booth & Morris, 2019; Dontigny, 1985; Jordan, 2006; Snijders et al, 1993; Vleeming et al, 2012; Zlomislic & Garfin, 2019). In the dysfunctional state, this homeostasis is affected: the sacrum tends to “counter‐nutate,” with innominate anterior rotation impacting the overall stability of the pelvic girdle (Hungerford & Gilleard, 2007; Ito et al, 2020; Lee, 2007).…”