ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

DOWNSIZING THE VEPTR DESIGN TO AVOID COMPLICATIONS
M. Reimeringer 1 , N. Nuño 2 and J. Ouellet 3
1. ABSTRACT
Vertical expandable prosthetic titanium rib (VEPTR) is a device used to treat early
onset scoliosis. Some complications such as wound breakdown or deep infections were
related due to its rather prominent size. Finite element analyses were carried on different
VEPTR designs and compared to the standard design subjected to compressive load
in order to analyze if its design could be downsized. Our results show that overall Von
Mises stress distribution within VEPTR remains below the titanium yield stress.
Thus, this study indicates the VEPTR design could be optimized.
2. INTRODUCTION
Idiopathic scoliosis can be classified into two categories: early and late onset. Late onset
scoliosis, the prevalent form, is associated with severe deformity without organic
consequences to the patient, whereas early onset scoliosis (EOS) refers to scoliosis
present on child aged at an early age and associated with severe deformity and
cardiopulmonary morbidity [1, 2].
There are different surgical and non-surgical options to manage EOS [3, 4], mainly
depending on the etiology of the EOS and always with the intention of preventing curve
progression while maintaining longitudinal growth of the spine. Among the nonsurgical
options, the use of casting followed by bracing is recommended until spinal
deformities reach a critical level. Once these critical levels of deformation is reached
(critical curve > 50° [5]), surgical management of the EOS is warranted, either by
fusion or fusionless technique. Fusionless technique involves implantation of
instrumentation of rod adjacent to the spine such as single or dual rod, vertical
expandable prosthetic titanium rib (VEPTR), or Luque Trolley, to correct and control
the curvature. Once growth is completed, definitive fusion is performed to achieve
permanent correction. Debnath [3] underlines that spinal fusion before the age of 10
years is discouraged for fear of compromising spinal growth and final height [6].
More recently, some surgeons have used VEPTR as a fusionless technique to treat
spinal deformity. This device was developed by Dr. Campbell. It is composed of two
sliding sleeves: the distal extension (Fig. 1a) and the proximal extension (Fig. 1b) held
in place by a distraction lock (Fig. 1c) and fixed either to rib, pelvis or vertebra. It was
approved by Food and Drug Administration (FDA) in 2004 especially to treat thoracic
1 PhD., Laboratoire de recherche en imagerie et orthopédie, Département de génie de la production
automatisée, École de technologie supérieure, 1100, rue Notre-Dame Ouest, Montréal. QC, H3C 1K3,
Canada
2 Professor, Laboratoire de recherche en imagerie et orthopédie, Département de génie de la production
automatisée, École de technologie supérieure, 1100, rue Notre-Dame Ouest, Montréal, QC, H3C 1K3,
Canada
3 MD, FRCSC, McGill Scoliosis & Spinal Research Group, Montréal Shriners Hospital, 1529 Cedar
Avenue, Montréal, QC, H3G 1A6, Canada