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Testing the impact of discoplasty on the biomechanics of the intervertebral disc with simulated degeneration: An in vitro study

Experimental workflow of the study. The arrow represents the applied load and the resulting moment M.

The intervertebral discs are soft tissues of the spine that are between vertebrae.  In the healthy condition they allow smooth motion.  In case of degeneration, the patient experiences severe pain and motion is hindered. Percutaneous Cement Discoplasty is a surgical technique that has recently been developed to relieve pain in highly degenerated intervertebral discs in patients that cannot undergo major surgery. Little is currently known about the biomechanical effects of discoplasty.

This study aimed at investigating the effects of discoplasty surgery and measuring its impact over the specimen geometry and mechanical behaviour. Tests were performed on porcine specimens in three conditions for each specimen: with intact disc, after simulating disc degeneration, and after discoplasty. An optical system (3D Digital Image Correlation, DIC) was used to measure the surface displacements and strains.

The posterior disc height, range of motion (ROM), and stiffness were measured at the peak load. The specimens were scanned with medical imaging (Computed Tomography, CT) to confirm that the cement distribution was acceptable. Discoplasty recovered the height loss caused by disc degeneration with respect to the intact condition, but it did not impact significantly either the ROM or the stiffness. The strains over the disc surface increased after nucleotomy, while discoplasty concentrated the strains on the endplates.

In conclusion, this preliminary study has shown that discoplasty has the potential of restoring the intervertebral height, opening the neuroforamen as clinically observed, without compromising the spine mobility. This study confirms that this in vitro approach can be used to further investigate discoplasty.

Chloé Techens, Marco Palanca, Peter Endre Éltes, Áron Lazáry, Luca Cristofolini, Testing the impact of discoplasty on the biomechanics of the intervertebral disc with simulated degeneration: An in vitro study, Medical Engineering & Physics,
Volume 84, (2020), Pages 51-59, ISSN 1350-4533.
https://doi.org/10.1016/j.medengphy.2020.07.024

Complicated Postoperative Flat Back Deformity Correction with the Aid of Virtual and 3D Printed Anatomical Models: Case Report

Definition of virtual 3D geometry from CT scan

The number of patients with iatrogenic spinal deformities is increasing with the global increase in the number of instrumented spinal operations. Correcting such a deformity could prove to be challenging due to the complex anatomical structure of the spine caused by previous surgeries. For these cases, extensive preoperative planning and proper implementation of the surgical plan are vital for surgical success.

The aim of this study was to generate a virtual and 3D printed patient-specific model to understand the complex anatomical-geometrical problem presented in a patient with severe sagittal and coronal malalignment due to repetitive surgical interventions over a 39-year period; and to develop the optimal plan for the deformity correction.

A patient-specific virtual geometry was defined using segmentation based on the preoperative CT scan. A 3D virtual plan was created with a cut out wedge shape of the L4 vertebrae to simulate a 3-column pedicle subtraction osteotomy (PSO) surgery with 20° of correction in the sagittal plane. In parallel, the developed virtual geometry was printed using a fused deposition modelling device to help the surgeon visualize deformed spine and provide guidance in the preoperative planning phase but also aid the surgeon in understanding the complex anatomy of the surgery.

The surgery was performed successfully, and no complications were registered. Using the preoperative and 6-month follow-up x-ray scans, the spinopelvic parameters were measured to calculate the amount of correction the surgery provided. The sagittal vertical axis decreased by 7cm, while the distance between the C7 plumb line and the sacral vertical line in the coronal plane was reduced by 4cm. A 30° correction was achieved for the lumbar lordosis following the PSO at the L4 vertebrae.

Fayad Jennifer, Turbucz Mate, Hajnal Benjamin, Bereczki Ferenc, Bartos Marton, Bank Andras, Lazary Aron, Eltes Peter Endre (2021). Complicated Postoperative Flat Back Deformity Correction with the Aid of Virtual and 3D Printed Anatomical Models: Case Report. Frontiers in Surgery, 8, 157.

https://doi.org/10.3389/fsurg.2021.662919

Spinner’s Third Training Event

Spinner Training Event 3 Montage: Top Row: Ansys’s Twin Builder; Spine Models from Yohan Payan; Prof Yohan Payan, CNRS, Bottom Row: Prof Damien Lacroix, Spine models from Damien Lacroix, Adagos’s NeurEco

At the end of April, Spinner held its third training event. In response to the current travel restrictions this was held online, over five mornings. The focus of the training was modelling and simulation and involved:

  • An introduction to the parsimonious approach to deep learning by Adagos, illustrated with a workshop using their NeurEco neural network package.
  • An introduction to reduced order modelling by Ansys, illustrated with a workshop using their Twin Builder.
  • Lectures on using finite element models to simulate the spine as an aid for surgery from Marie-Line Pissonier, Hôpital Pitie Salpêtrière, Prof Yohan Payan, CNRS and Prof Damien Lacroix, University of Sheffield.

The lectures were open to staff and students of the Universities of Sheffield and Bologna.

Some comments from the Spinner Fellows:

Ansys workshops were hands on training sessions on software for reduced order modelling. The training material was clear and allowed us to do the training smoothly.

Despite the remote conference, it was very easy to ask questions during the different talks and to interact, so that was a very good point.

Neural-networks can be a great tool to help creating models that accurately predict the evolution of patients, and even to predict how successful a procedure/strategy can be before actual surgery.

The hands-on workshops were very nice to try, the lectures on the application of spine modelling were also very interesting.

Spinner Fellows