Imaging features of lumbar spinal stenosis in patients with diffuse idiopathic skeletal hyperostosis

English Keywords:Lumbar spinal stenosis  Diffuse idiopathic skeletal hyperostosis  Imaging features

English Abstract:

  【Abstract】 Objectives: To investigate the imaging features of lumbar spinal stenosis(LSS) in patients with diffuse idiopathic skeletal hyperostosis(DISH). Methods: The preoperative imaging data of 96 DISH patients complicated with LSS at L4/5 who underwent operation in our hospital from June 2017 to October 2021 were retrospectively reviewed. The patients were divided into T-DISH group(n=49) with ossification limited only to thoracic vertebrae and L-DISH group(n=47) with ossification involving thoracic and lumbar vertebrae; And LSS patients without DISH treated surgically in our hospital during the same period were recruited as control, the N-DISH group(n=125), by matching gender, age, and stenosis segments. The thoracic kyphosis(TK), lumbar lordosis(LL), sacral slope(SS), pelvic incidence(PI), pelvic tilt(PT), and sagittal vertical axis(SVA) were measured of all groups of patients, the numbers of ossified ligament were counted, and the degenerative conditions of intervertebral disc and facet joint were evaluated with Pfirrmann grade and Weishaupt grade respectively. Additionally, the anteroposterior diameter, cross-sectional area, and dural sac area of L4/5 vertebral canal were measured to evaluate spinal stenosis. The differences in sagittal morphology, intervertebral disc and facet joint degeneration, and spinal canal stenosis were compared between the three groups, and correlation analyses between the number of ossified ligament segments, dural sac area, cross-sectional area of the spinal canal, Pfirrmann grade of intervertebral disc degeneration, and Weishaupt grade of facet joint degeneration were performed. Results: SVA and TK in DISH group were significantly higher than those in N-DISH group(P<0.05), and SVA in L-DISH group was significantly higher than that in N-DISH group, while no significant difference of SVA was found between T-DISH group and N-DISH group. Although there was no significant difference in LL, SS, PI and PT between DISH group and N-DISH group, LL and SS of L-DISH group were significantly lower than those of N-DISH group(P<0.05). LL and SS in L-DISH group were significantly smaller than those in T-DISH group, but there was no significant difference in SVA, TK, PI and PT between groups. The degeneration grades of disc and facet joint in DISH group were higher than those in N-DISH group with significant differences(P<0.001); The Pfirrmann grade of disc degeneration in L-DISH group was significantly higher than that in T-DISH group(P<0.001), while there was no significant difference in Weishaupt grade of facet joint degeneration between groups(P=0.08). N-DISH group wasn′t different significantly from DISH group in the anteroposterior diameter of spinal canal at L4/5, and was significantly larger in the dural sac area. Correlation analyses showed that the number of ossified ligament segments was moderately positively correlated with Pfirrmann grade of disc degeneration(r=0.440, P<0.001), while strongly positively correlated with Weishaupt grade of small joint degeneration(r=0.661, P<0.001); Dural sac area wasn′t significantly correlated with Pfirrmann grade of disc degeneration, and it was negatively correlated with Weishaupt grade of small joint degeneration(r=-0.323, P<0.001); Cross-sectional area of spinal canal wasn′t significantly correlated with Pfirrmann grade of disc degeneration or Weishaupt grade of small joint degeneration(P>0.05); And Pfirrmann grade of disc degeneration was significantly correlated with Weishaupt grade of small joint degeneration(P<0.001). Conclusions: Heterotopic ossification of the spine affecting the lumbar in DISH patients can significantly change the sagittal morphology, resulting in trunk anteversion, reduced LL, and loss of SS. DISH patients have obvious degeneration of intervertebral disc and facet joint and serious spinal stenosis.