Spinal shape modulation in a porcine model by a highly flexible and extendable non-fusion implant system

Abstract

Purpose In vivo evaluation of scoliosis treatment using a novel approach in which two posterior implants are implanted: XSLAT (eXtendable implant correcting Scoliosis in LAT bending) and XSTOR (eXtendable implant correcting Scoliosis in TORsion). The highly flexible and extendable implants use only small, but continuous lateral forces (XSLAT) and torques (XSTOR), thereby allowing growth and preventing fusion. Methods Since (idiopathic) scoliosis does not occur spontaneously in animals, the device was used to induce a spinal deformity rather than correct it. Six of each implants were tested for their ability to induce scoliotic deformations in 12 growing pigs. Each implant spanned six segments and was attached to three vertebrae using sliding anchors. Radiological and histological assessments were done throughout the 8-week study. Results In all animals, the intended deformation was accomplished. Average Cobb angles were 19°for XSLAT and 6°for XSTOR. Average apical spinal torsion was 0°f or XSLAT and 9°for XSTOR. All instrumented segments remained mobile and showed 20 % growth. Moderate degeneration of the facet joints was observed and some debris was found in the surrounding tissue.Conclusions The approach accomplished the intended spinal deformation while allowing growth and preventing fusion.

Induction of a representative idiopathic-like scoliosis in a porcine model using a multidirectional dynamic spring-based system

“…We did investigate a previous version of the torsional device in domestic pigs, where it was used stand alone. In that study we similarly found rotation, but limited to 9 degrees and only minimal coronal deformation of 6 degrees, which cannot be regarded as a suitable model for scoliosis [7]. In the current mini-pig model, including a contralateral tether, the mean coronal curves were 19 degrees, which we consider as relevant although smaller than other studies where more aggressive techniques were used in faster growing animals [14,15,[30][31][32].…”

“…In the current mini-pig model, including a contralateral tether, the mean coronal curves were 19 degrees, which we consider as relevant although smaller than other studies where more aggressive techniques were used in faster growing animals [14,15,[30][31][32]. However, more important than coronal curve size is that the curves are consistent, the spine remains mobile and includes all 3D characteristics, including axial rotation and anterior lengthening in the disk, of idiopathic scoliosis [7].…”

“…1a). The torsional device is a further development of a previously used version [7]. The device consists of two medical grade Titanium (Ti6Al4V) U-loops with sliding connectors that contain type PA2200 nylon bearings and two torsion springs in series, made of a nickel-cobalt alloy (MP35N) with a lockable connector in between (Fig.…”

“…Furthermore, the implant should be flexible to keep the spine mobile and allow for growth. Based on our previously developed torsional device [7]. and our experience with posterior spring distraction in early onset scoliosis treatment [8], we developed a combination of these devices to generate both posterior distraction and axial plane rotational force.…”

Growth modulation and remodeling by means of posterior tethering technique for correction of early-onset scoliosis with thoracolumbar kyphosis

“…Though they are fundamentally different in geometry and loading from human spine [22], it may not be true to compare these findings with wedging modulation in the sagittal plane in thoracolumbar kyphosis deformities. Also, many of their outcomes were mostly illustrated as a change in the wedging angle, which is hard to compare with absolute growth values as in our study.…”