The influence of pelvic incidence on slip degree and sagittal spino-pelvic alignment of adult lumbosacral isthmic spondylolisthesis

English Keywords:Lumbosacral isthmic spondylolisthesis  Pelvic incidence  Slip degree  Sagittal balance

English Abstract:

  【Abstract】 Objectives: To evaluate the distribution of pelvic incidence(PI) and its influence on sagittal alignment of lumbosacral isthmic spondylolisthesis(IS). Methods: The consecutive lumbosacral IS patients(Meyerding grade Ⅰ or Ⅱ) between January 2012 and Ａugust 2017 were retrospectively reviewed. According to SDSG slippage PI grouping standard, the enrolled patients were divided into the low PI group(PI<45°), the normal PI group(45°－60°) and the high PI group(PI＞60°). Parameters were measured, including slip percentage, disc height, pelvic incidence, pelvic tilt(PT), sacral slope(SS), lumbar lordosis(LL), lower lumbar lordosis, upper lumbar lordosis, thoracic kyphosis, sagittal vertical axis(SVA). Meanwhile, lordosis distribution index(LDI=lower lumbar lordosis/LL) and PT/PI were calculated. The above parameters were compared among groups. Results: Totally, 153 patients(50 males and 103 females) were enrolled, with a mean age of 51.7±10.4 years(range, 31-71 years). The PI of cohort had a normal distribution(P=0.2０) and the mean PI was 59.9°±10.5°. There were 12(8%), 67(44%) and 74(48%) patients assigned in the low PI, normal PI and high PI group respectively. The slip degree of low PI group was significantly lower than that of normal PI group and high PI group(P<0.001). The L5/S1 disc height of high PI group was higher than that of the other two groups(P<0.05). PI, PT, SS, PT/PI, LL, lower lumbar lordosis, upper lumbar lordosis in low PI group were statistically lower than that of normal PI group and high PI group(P<0.01). However, LDI of low PI group was significantly higher than that of normal PI and high PI group(P=0.001). Meanwile, SVA of high PI group was higher than that of the other two groups(P<0.05). Positive correlations were found between PI and slip percentage, PT, SS, PT/PI, LL, upper lumbar lordosis, lower lumbar lordosis and SVA, and negative correlations were noted between PI and LDI(P<0.05). Conclusions: The PI of lumbarsacral low-grade IS was normally distributed. The slip degree of lumbarsacral isthmic spondylisthesis is positively correlated with PI. Patients with low PI have mild degree of spondylolisthesis. Patients with high PI have severe degree of spondylolisthesis and remarkable disc collapse, as well as pelvic retroversion.