Aakash Agarwal1, Anand K Agarwal1, Arvind Jayaswal2, Vijay K Goel3. 1. Engineering Center for Orthopaedic Research Excellence, Department of Bioengineering and Orthopaedics Surgery, Colleges of Engineering and Medicine, University of Toledo, 5051 Nitschke Hall MS 3032801 W. Bancroft St., Toledo, OH 43606-3390, USA. 2. Department of Orthopaedics, All India Institute of Medical Sciences, Ansari Nagar East, Gautam Nagar, New Delhi, DL 110029, India. 3. Engineering Center for Orthopaedic Research Excellence, Department of Bioengineering and Orthopaedics Surgery, Colleges of Engineering and Medicine, University of Toledo, 5051 Nitschke Hall MS 3032801 W. Bancroft St., Toledo, OH 43606-3390, USA. Electronic address: Vijay.Goel@utoledo.edu.
Abstract
BACKGROUND: Growth rods are used to limit the progression of scoliosis without restraining the opportunity for the spine to grow. The growth is sustained by consecutive distraction at intervals of 6 months. The optimal distraction force for a scoliotic patient is not defined adequately and rod breakage, screw loosening, stimulation of growth and altered sagittal contour has been observed. HYPOTHESIS: The hypothesis of this study is that for every patient with dual growth rods treatment there exists a distraction force that will sustain the growth of that patient's spine equal to normal growth with minimum changes in sagittal contours, results in lower von Mises stresses on the rods and minimum force at the pedicle screw-bone interface at 6 months. OBJECTIVE: In this finite element study, we undertook an objective to identify the effect of magnitude of distraction forces on the T1-S1 growth, maximum von Mises stresses on the rods, sagittal contours, and the load at the pedicle screw-bone interface. RESULTS: An optimal distraction force exists for which the growth is sustained with minimum stress on the rod, lower loads at screw-bone interface and unaltered sagittal contours. Another observation was that higher distraction forces (in the given range) didn't produce stresses on rod or load on screw that could result in failure of the implant. CONCLUSION: Restoration of sagittal contour along with height restoration could guide the clinical practice, for the given range of distraction force. Published by Elsevier Inc.
BACKGROUND: Growth rods are used to limit the progression of scoliosis without restraining the opportunity for the spine to grow. The growth is sustained by consecutive distraction at intervals of 6 months. The optimal distraction force for a scoliotic patient is not defined adequately and rod breakage, screw loosening, stimulation of growth and altered sagittal contour has been observed. HYPOTHESIS: The hypothesis of this study is that for every patient with dual growth rods treatment there exists a distraction force that will sustain the growth of that patient's spine equal to normal growth with minimum changes in sagittal contours, results in lower von Mises stresses on the rods and minimum force at the pedicle screw-bone interface at 6 months. OBJECTIVE: In this finite element study, we undertook an objective to identify the effect of magnitude of distraction forces on the T1-S1 growth, maximum von Mises stresses on the rods, sagittal contours, and the load at the pedicle screw-bone interface. RESULTS: An optimal distraction force exists for which the growth is sustained with minimum stress on the rod, lower loads at screw-bone interface and unaltered sagittal contours. Another observation was that higher distraction forces (in the given range) didn't produce stresses on rod or load on screw that could result in failure of the implant. CONCLUSION: Restoration of sagittal contour along with height restoration could guide the clinical practice, for the given range of distraction force. Published by Elsevier Inc.
Entities:
Keywords:
Distraction; Finite element study; Growth rods; Juvenile scoliosis; Rod fracture