Correlation study of sacral morphology and sagittal spino-pelvic alignment

English Keywords:Sacrum  Spino-pelvic parameters  Sagittal alignment

English Abstract:

  【Abstract】 Objectives: To explore the correlation of sacral morphology and sagittal spino-pelvic alignment. Methods: The full-length free-standing radiographs of 132 healthy adults aged from 18 to 35 were reviewed. Radiological parameters, including lumbar lordosis(LL), pelvic incidence(PI), sacral slope(SS), and pelvic tilt(PT) were measured. Ferguson method was used to measure the angle between T12, L1-L5, S1-S5, S5Co1 tilt and the vertical line of the upper endplate of S1. The sacral morphology parameters including the angle between S1-2 tilt and the vertical line of the upper end plate of S1(S1-2T), the angle between S1-2 tilt and S5Co1 tilt(sacral kyphosis, SK), the angle between the anterior edge of S2 and S4Co1 tilt (α), the upper endplate of S1 and the anterior edge of S2(β) and S4Co1 tilt and the upper endplate of S1(θ) were measured. The sacral position parameters including the horizontal angle of anterior edge of S2(S2HA) and the horizontal angle of S5Co1 tilt(S5Co1HA) were measured. Statistical methods included statistical description, correlation analysis, linear regression and paired t test. Results: S2 was the sagittal lumbo-sacral "end vertebra". The correlation between S1-2T and PI and LL was 0.656 and 0.260(P<0.01), and it was 0.527 and 0.434 between SK and PI and LL(P<0.01). The angle between S1-S5, S5Co1 tilt and the vertical line of the upper end plate of S1 were related to PI and LL; the difference of the tilt between S1 and S2 was related to the lower lumbar tilt. PI=35°+0.52×β-0.37×θ(R=0.87); LL=79°-0.45×θ（R=0.52）; PI=α±10°; LL=SK±12°; SS=S2AEHA+1.5°±12°; S5Co1HA=91°±11°. Conclusions: The degree of backward tilt of S1 and S2 are negatively correlated with PI and LL; SK is positively correlated with PI and LL; the difference of the tilt between S1 and S2 reflects the distribution of the lower lumbar spine to LL; the sacral morphology parameters could predict PI and LL, and sacral position parameters reflect pelvic tilted state.