Evaluation of the relationship between L5-S1 spondylolysis and isthmic spondylolisthesis and lumbosacral-pelvic morphology by imaging via 2- and 3-dimensional reformatted computed tomography.

PURPOSE The purpose of this study was to investigate the differences in the axial and coronal parameters of lumbosacropelvic morphology among a population with spondylolysis and healthy individuals by using 2- and 3-dimensional (3D) reformatted computed tomographic images. Moreover, this study aimed to evaluate the differences in sagittal geometry. MATERIALS AND METHODS The stone protocol abdominal computed tomographic images of 386 patients were retrospectively analyzed. Thirty individuals who had spondylolysis at L5-S1 level were included in the study. Moreover, a control group of individuals free of spondylolysis and spondylolisthesis was formed, similar in age and sex to the study group. A number of linear and angular lumbosacral morphologic parameters were evaluated using 2D and 3D reformatted computed tomographic images. The data of the 2 groups were compared using a t test. RESULTS There was an association between spondylolysis and decreased interpedicular angle and S1 vertebra interfacet index, increased distance between the iliac crest and L5 vertebral transverse process, decreased L5 pedicle width, and increased height of the iliac crest and decreased L5 vertebra sagittal index. The paravertebral muscle area was larger in the lysis group when compared with the healthy individuals. CONCLUSIONS Multiple factors (eg, interpedicular angle, S1 vertebra interfacet index, the distance between the iliac crest and L5 vertebra transverse process, L5 pedicle width, height of the iliac crest and L5 vertebra sagittal index) in lumbosacropelvic morphology affect the defect development in pars interarticularis. In individuals with spondylolysis, paravertebral muscle hypertrophy develops as a secondary adaptive change.