Archives of Orthopaedic and Trauma Surgery

, Volume 131, Issue 9, pp 1187–1194

Biomechanical rationale of sacral rounding deformity in pediatric spondylolisthesis: a clinical and biomechanical study

  • Tomoya Terai
  • Koichi Sairyo
  • Vijay K. Goel
  • Nabil Ebraheim
  • Ashok Biyani
  • Faizan Ahmad
  • Ali Kiapour
  • Kosaku Higashino
  • Toshinori Sakai
  • Natsuo Yasui
Orthopaedic Surgery

DOI: 10.1007/s00402-010-1257-2

Cite this article as:
Terai, T., Sairyo, K., Goel, V.K. et al. Arch Orthop Trauma Surg (2011) 131: 1187. doi:10.1007/s00402-010-1257-2

Abstract

Aim

Rounding surface of the sacral dome and wedging deformity of the vertebral body are commonly observed in patients with isthmic spondylolisthesis. Recently, an animal study showed that the deformity can be caused by the growth plate involvement in the immature pediatric vertebral body after biomechanical alteration due to the pars defects. However, the pathomechanism and biomechanics of these deformities have yet to be clarified. To demonstrate that the sacral rounding deformity observed in pediatric patients with spondylolisthesis can be reversed, and to understand the pathomechanism of the deformity from the biomechanical standpoint by analyzing changes of stress around the growth plate of the vertebral body due to spondylolysis.

Method

Three-dimensional finite element pediatric lumbar models of the L3–L5 segment were utilized. Unlike the adult model, this pediatric model had growth plates and apophyseal rings. We analyzed stress distribution in response to 351°N axial compression and 10 N m moment in flexion, extension, lateral bending, and axial rotation. Bilateral spondylolysis was created in the model at the L4 level. The stress in the bilateral defect model was compared to the intact model predictions and the results obtained in the pediatric patients with sacral rounding deformity.

Results

Two patients presented rounding deformity of the anterior upper corner at S1 at the initial visit. They were asked to stop sports activities and use a soft trunk brace. Twelve months later, no rounding deformity was observed on the radiographs indicating that this deformity was reversible in pediatric cases. The biomechanical study indicated that in the pediatric spondylolytic spine, mechanical stress increased at the anterior upper corner during lumbar motion.

Conclusion

In the presence of spondylolysis, mechanical stress increases in the growth plate at the anterior upper corner. Repetitive increases of mechanical stress may cause rounding deformity of the sacral dome mediated by growth plate involvement. When mechanical stress at the growth plate is reduced by wearing a brace, the proper functioning of the growth plate can help to remodel the sacral dome to its normal shape.

Keywords

SpondylolisthesisGrowth plateBiomechanicsFinite element analysisRounding deformity

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Tomoya Terai
    • 1
    • 2
  • Koichi Sairyo
    • 2
  • Vijay K. Goel
    • 1
  • Nabil Ebraheim
    • 1
  • Ashok Biyani
    • 1
  • Faizan Ahmad
    • 1
  • Ali Kiapour
    • 1
  • Kosaku Higashino
    • 2
  • Toshinori Sakai
    • 2
  • Natsuo Yasui
    • 2
  1. 1.Engineering Center for Orthopaedic Research Excellence (E-CORE), Departments of Bioengineering and Orthopaedic Surgery, Colleges of Engineering and MedicineUniversity of ToledoToledoUSA
  2. 2.Department of OrthopedicsUniversity of Tokushima School of MedicineTokushimaJapan