The sagittal morphology of sacrum in adolescents with L5/S1 dysplastic spondylolisthesis

English Keywords:Adolescent  Spondylolisthesis  Dysplastic  Sagittal plane  Sacral morphology  Balance

English Abstract:

  【Abstract】 Objectives: To evaluate the sagittal morphology ofsacruminadolescents with L5/S1 dysplastic spondylolisthesis. Methods: 13 adolescent patients with L5/S1 dysplastic spondylolisthesis(2 males and 11 females; mean age, 12.2±3.1 years; range, 9 to 18 years) and age-matched control group of 30 normal adolescents were recruited in this retrospective study. All patients received surgical intervention from May 2002 to March 2016 in our hospital. Radiographic measurements including sacral morphology parameters, postural parameters were carried out on the standing upright lateral radiographs of the spine and pelvis.Independent samples t tests was used to analyze the differences of radiographic parameters. Results: Adolescent patients with L5/S1 dysplastic spondylolisthesis had significant morphologic difference in segmental sacrum morphology and global sacral configuration. There were 10 domed sacrums, 6 wedged L5 vertebral bodys and 9 lumbosacral kyphosis among 13 dysplastic patients. The sacral angle and S1 superior angle of dysplastic groups were much lower, but both sacral kyphosisin Cobb method(50.1°±10.6° versus 18.1°±10.4°) and in Ferguson method(40.5°±9.9° versus 23.1°±11.5°) were higher than those in control group, which meant that dysplastic patients characterized with a more vertical S1 vertebrae and much severer global sacral kyphosis. Compare to control group, the lumbosacral angle, sacral table angleand S1 index of dysplastic group were extremely lower(P＜0.01). While sagittal vertical axis(46.5±42.3mm versus -25.6±21.8mm), L5 incidence, pelvic tiltand sagittal pelvic thicknessin dysplastic group were significantly higher than those in control group(P＜0.05), sacral slope were much lower. The dysplastic patients had aabmormal posture containing trunk forward leaning, pelvic retroversion and vertical sacrum. In comparison with the mild dysplastic spondylolisthesis group(5 cases), thehigh group(8 cases) were significantly higher on slip percentage[(67.3±18.6)% versus (45.4±12.5)%], sacral kyphosisin Ferguson method(45.8±8.4 versus 32.2±5.1) and sagittal vertical axis(52.6±24.7 versus 21.6±9.5)(P＜0.05). Conclusions: Adolescents with dysplastic spondylolisthesis not only present with lumbosacral malformation but also characterized with severe global sacral kyphosis. To compensate sagittal imbalance, pelvic retroversion and vertical sacrum occur secondary to trunk forward leaning. And these abmormal morphology are influenced by the degree of dysplastic.