Low pelvic incidence is associated with Andersson lesions in ankylosing spondylitis patients with kyphosis

Relationship between spinal structural damage and sagittal balance in axial spondyloarthritis: Is the thoracic spine the starting point?

OBJECTIVES

To assess the relationship between spinal structural damage, sagittal balance parameters and spine curvatures in patients with axial spondyloarthritis (axSpA).

MATERIAL AND METHODS

In this cross-sectional study, the pelvic and sagittal balance parameters were obtained through EOS® (Biospace, Paris, France). Patients were divided into three groups according to the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) tertiles (G1 ≤6, n = 36; G2: 6.1-31, n = 36; G3 >31, n = 35) and pelvic and sagittal parameters were compared across them. Multivariable regression analysis was performed to analyze the impact of spinal structural damage and of other factors on sagittal vertical axis (SVA), an important sagittal balance parameter.

RESULTS

A total of 107 patients was included. G2 and 3 exhibited higher mean values of thoracic kyphosis T1-T12 when compared to G1 (10.5°(12.3) vs. 22.3°(17.3) vs. 35.2°(14.6), p < 0.001), and G3 demonstrated lumbar L1-S1 straightening compared to the other groups (55.7°(9) and 50.7°(19.8), G1 and G2, respectively, vs. 35.7°(13.2), p < 0.001). Mean SVA values showed an increasing gradient from G1 to G3 (21.6(25.1) vs. 41(44.3) vs. 84.3(47.2)mm, p < 0.001). In the multivariable regression, a one-unit increase in total mSASSS was associated with an average 0.8 mm higher SVA.

CONCLUSIONS

Our data showed that more spinal structural damage is associated with a higher SVA, reflecting poorer sagittal balance. Patients with increasing spinal damage have an important increase in thoracic kyphosis suggesting that postural modifications in patients with axSpA might have their origin in the thoracic spine.

Case Report: Identifying Andersson-Like Lesions in Diffuse Idiopathic Skeletal Hyperostosis

Andersson lesions (ALs) in ankylosing spondylitis (AS) pose a severe risk to the stability of ankylosed spine, which might result in significant deterioration of spinal cord function after traumatic or inflammatory causes. Herein, erosive discovertebral lesions in diffuse idiopathic skeletal hyperostosis (DISH) presented important clinical similarities to AL in AS, but failed to completely recognize unstable spinal lesions. Therefore, we pioneered to identify spinal discovertebral lesions similar to Andersson-like lesions (ALLs) in DISH, followed by the characterization and summarization of the etiology, radiology, laboratory results, clinical symptoms, and treatment strategies for AL in AS with ALL in DISH. By characterizing the ALL in DISH cases, we showed that the ALL was mainly traumatic and established at the junction of focal stress between two adjacent ossified level arms. Erosive discovertebral ALLs were formed after trivial stress of direct impact and could be subdivided into transdiscal, transvertebral, and discovertebral types radiologically. Patients who presented with ALL frequently suffered from consistent back pain clinically and experienced a decrease in motion ability that could reflect skeletal stability, which received treatment effectiveness after conservative external spinal immobilization or further surgical internal fixation, indicating the significance of recognizing ALL in the ankylosed DISH spine to further maintain spinal stability in order to prevent catastrophic neurologic sequelae. Our work highlighted the clinical relevance of ALL in DISH in comparison with AL in AS, which provided broader insight to identify ALL in DISH, thus facilitating early intervention against DISH deterioration.