Publications by authors named "Peter Endre Eltes"

10 Publications

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

Front Surg 2021 28;8:662919. Epub 2021 May 28.

Department of Industrial Engineering, Alma Mater Studiorum, Universita di Bologna, Bologna, Italy.

The number of patients with iatrogenic spinal deformities is increasing due to the increase in instrumented spinal surgeries globally. Correcting a deformity could be challenging due to the complex anatomical and geometrical irregularities caused by previous surgeries and spine degeneration. Virtual and 3D printed models have the potential to illuminate the unique and complex anatomical-geometrical problems found in these patients. We present a case report with 6-months follow-up (FU) of a 71 year old female patient with severe sagittal and coronal malalignment due to repetitive discectomy, decompression, laminectomy, and stabilization surgeries over the last 39 years. The patient suffered from severe low back pain (VAS = 9, ODI = 80). Deformity correction by performing asymmetric 3-column pedicle subtraction osteotomy (PSO) and stabilization were decided as the required surgical treatment. To better understand the complex anatomical condition, a patient-specific virtual geometry was defined by segmentation based on the preoperative CT. The geometrical accuracy was tested using the Dice Similarity Index (DSI). A complex 3D virtual plan was created for the surgery from the segmented geometry in addition to a 3D printed model. The segmentation process provided a highly accurate geometry (L1 to S2) with a DSI value of 0.92. The virtual model was shared in the internal clinical database in 3DPDF format. The printed physical model was used in the preoperative planning phase, patient education/communication and during the surgery. The surgery was performed successfully, and no complications were registered. The measured change in the sagittal vertical axis was 7 cm, in the coronal plane the distance between the C7 plumb line and the central sacral vertical line was reduced by 4 cm. A 30° correction was achieved for the lumbar lordosis due to the PSO at the L4 vertebra. The patient ODI was reduced to 20 points at the 6-months FU. The printed physical model was considered advantageous by the surgical team in the pre-surgical phase and during the surgery as well. The model was able to simplify the geometrical problems and potentially improve the outcome of the surgery by preventing complications and reducing surgical time.
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http://dx.doi.org/10.3389/fsurg.2021.662919DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8192795PMC
May 2021

A novel three-dimensional volumetric method to measure indirect decompression after percutaneous cement discoplasty.

J Orthop Translat 2021 May 1;28:131-139. Epub 2021 Apr 1.

Department of Spine Surgery, Semmelweis University, Budapest, Hungary.

Purpose: Percutaneous cement discoplasty (PCD) is a minimally invasive surgical option to treat patients who suffer from the consequences of advanced disc degeneration. As the current two-dimensional methods can inappropriately measure the difference in the complex 3D anatomy of the spinal segment, our aim was to develop and apply a volumetric method to measure the geometrical change in the surgically treated segments.

Methods: Prospective clinical and radiological data of 10 patients who underwent single- or multilevel PCD was collected. Pre- and postoperative CT scan-based 3D reconstructions were performed. The injected PMMA (Polymethylmethacrylate) induced lifting of the cranial vertebra and the following volumetric change was measured by subtraction of the geometry of the spinal canal from a pre- and postoperatively predefined cylinder. The associations of the PMMA geometry and the volumetric change of the spinal canal with clinical outcome were determined.

Results: Change in the spinal canal volume (ΔV) due to the surgery proved to be significant (mean ΔV = 2266.5 ± 1172.2 mm, n = 16; p = 0.0004). A significant, positive correlation was found between ΔV, the volume and the surface of the injected PMMA. A strong, significant association between pain intensity (low back and leg pain) and the magnitude of the volumetric increase of the spinal canal was shown (ρ = 0.772, p = 0.009 for LBP and ρ = 0.693, p = 0.026 for LP).

Conclusion: The developed method is accurate, reproducible and applicable for the analysis of any other spinal surgical method. The volume and surface area of the injected PMMA have a predictive power on the extent of the indirect spinal canal decompression. The larger the ΔV the higher clinical benefit was achieved with the PCD procedure.

The Translational Potential Of This Article: The developed method has the potential to be integrated into clinical software's to evaluate the efficacy of different surgical procedures based on indirect decompression effect such as PCD, anterior lumbar interbody fusion (ALIF), lateral lumbar interbody fusion (LLIF), oblique lumbar interbody fusion (OLIF), extreme lateral interbody fusion (XLIF). The intraoperative use of the method will allow the surgeon to respond if the decompression does not reach the desired level.
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http://dx.doi.org/10.1016/j.jot.2021.02.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8050383PMC
May 2021

Development of a Computer-Aided Design and Finite Element Analysis Combined Method for Affordable Spine Surgical Navigation With 3D-Printed Customized Template.

Front Surg 2020 25;7:583386. Epub 2021 Jan 25.

National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary.

Revision surgery of a previous lumbosacral non-union is highly challenging, especially in case of complications, such as a broken screw at the first sacral level (S1). Here, we propose the implementation of a new method based on the CT scan of a clinical case using 3D reconstruction, combined with finite element analysis (FEA), computer-assisted design (CAD), and 3D-printing technology to provide accurate surgical navigation to aid the surgeon in performing the optimal surgical technique by inserting a pedicle screw at the S1 level. A step-by-step approach was developed and performed as follows: (1) Quantitative CT based patient-specific FE model of the sacrum was created. (2) The CAD model of the pedicle screw was inserted into the sacrum model in a bicortical convergent and a monocortical divergent position, by overcoming the geometrical difficulty caused by the broken screw. (3) Static FEAs (Abaqus, Dassault Systemes) were performed using 500 N tensile load applied to the screw head. (4) A template with two screw guiding structures for the sacrum was designed and manufactured using CAD design and 3D-printing technologies, and investment casting. (5) The proposed surgical technique was performed on the patient-specific physical model created with the FDM printing technology. The patient-specific model was CT scanned and a comparison with the virtual plan was performed to evaluate the template accuracy FEA results proved that the modified bicortical convergent insertion is stiffer (6,617.23 N/mm) compared to monocortical divergent placement (2,989.07 N/mm). The final template was created via investment casting from cobalt-chrome. The template design concept was shown to be accurate (grade A, Gertzbein-Robbins scale) based on the comparison of the simulated surgery using the patient-specific physical model and the 3D virtual surgical plan. Compared to the conventional surgical navigation techniques, the presented method allows the consideration of the patient-specific biomechanical parameters; is more affordable, and the intraoperative X-ray exposure can be reduced. This new patient- and condition-specific approach may be widely used in revision spine surgeries or in challenging primary cases after its further clinical validation.
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http://dx.doi.org/10.3389/fsurg.2020.583386DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7873739PMC
January 2021

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

Med Eng Phys 2020 10 30;84:51-59. Epub 2020 Jul 30.

Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Viale Risorgimento, 2, Bologna 40136, Italy. Electronic address:

Percutaneous Cement Discoplasty has recently been developed to relieve pain in highly degenerated intervertebral discs presenting a vacuum phenomenon in patients that cannot undergo major surgery. Little is currently known about the biomechanical effects of discoplasty. This study aimed at investigating the feasibility of modelling empty discs and subsequent discoplasty surgery and measuring their impact over the specimen geometry and mechanical behaviour. Ten porcine lumbar spine segments were tested in flexion, extension, and lateral bending under 5.4 Nm (with a 200 N compressive force and a 27 mm offset). Tests were performed in three conditions for each specimen: with intact disc, after nucleotomy and after discoplasty. A 3D Digital Image Correlation (DIC) system 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. CT scans were performed to confirm that the cement distribution was acceptable. Discoplasty recovered the height loss caused by nucleotomy (p = 0.04) 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 recovered the intervertebral posterior height, opening the neuroforamen as clinically observed, but it did not influence the spine mobility or stiffness. This study confirms that this in vitro approach can be used to investigate discoplasty.
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http://dx.doi.org/10.1016/j.medengphy.2020.07.024DOI Listing
October 2020

Geometrical accuracy evaluation of an affordable 3D printing technology for spine physical models.

J Clin Neurosci 2020 Feb 3;72:438-446. Epub 2020 Jan 3.

National Center for Spinal Disorders, Királyhágó u. 1-3, H-1126 Budapest, Hungary.

Objective: The aim of the study is to develop a workflow to establish geometrical quality criteria for 3D printed anatomical models as a guidance for selecting the most suitable 3D printing technologies available in a clinical environment.

Methods: We defined the 3D geometry of a 25-year-old male patient's L4 vertebra and the geometry was then printed using two technologies, which differ in printing resolution and affordability: Fused Deposition Modelling (FDM) and Digital Light Processing (DLP). In order to measure geometrical accuracy, the 3D scans of two physical models were compared to the virtual input model. To compare surface qualities of these printing technologies we determined surface roughness for two regions of interest. Finally, we present our experience in the clinical application of a physical model in a congenital deformity case.

Results: The analysis of the distribution of the modified Hausdorff distance values along the vertebral surface meshes (99% of values <1 mm) of the 3D printed models provides evidence for high printing accuracy in both printing techniques. Our results demonstrate that the surface qualities, measured by roughness are adequate (~99% of values <0.1 mm) for both physical models. Finally, we implemented the FDM physical model for surgical planning.

Conclusion: We present a workflow capable of determining the quality of 3D printed models and the application of a high quality and affordable 3D printed spine physical model in the pre operative planning. As a result of the visual guidance provided by the physical model, we were able to define the optimal trajectory of the screw insertion during surgery.
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http://dx.doi.org/10.1016/j.jocn.2019.12.027DOI Listing
February 2020

Attitude of spine surgeons towards the application of 3D technologies - a survey of AOSpine members.

Ideggyogy Sz 2019 Jul;72(7-8):227-235

National Center for Spinal Disorders, Budapest.

Background And Purpose: 3D technologies (3D virtual and physical model, 3D printing, computer aided engineering, finite element analysis based simulations) play an important role in personalized spine surgery. Objective - In collaboration with AOSpine a global, online survey-based study was performed in order to determine the acceptance rate and the factors which stand against the wider spread of 3D technologies.

Methods: A survey containing 21 questions was developed and divided into five pages, every page corresponding to one chapter. Our analysis is based on the responses of 282 spine surgeons from 57 countries. To interpret our results in a global context, we used the Human Development Index of the respondent's countries in comparisons.

Results: Significant difference between the AOSpine regions (p ≤ 0.05) was found, with the highest acceptance in Asia-Pacific region. There was no significant difference in acceptance score according to the field of spine surgery, or the surgical experience in years (p=0.77, and p=0.19). In the case of public practice, we found significantly higher acceptance compared to private and mixed (public and private) surgical practice (p ≤ 0.05). The acceptance of the technology varied based on the respondent's resident country's Human Development Index and was significantly different between "Medium" vs "Very high" (p = 0.0005) and "High" vs "Very high" (p=0.019) category. Significant positive correlation was found between the acceptance score and the HDI score (Spearman test, ρ = 0.37, p = 0.007). The main limitation factor was identified as the lack of information.

Conclusion: There is high interest among spine surgeons towards the incorporation of 3D technologies into the clinical practice. Education, the healthcare system, and the economic environment plays a major role in acceptance. Our results provide the basis of a strategy to promote the application of 3D technologies.
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http://dx.doi.org/10.18071/isz.72.0227DOI Listing
July 2019

Indirect foraminal decompression and improvement in the lumbar alignment after percutaneous cement discoplasty.

Eur Spine J 2019 06 20;28(6):1441-1447. Epub 2019 Apr 20.

National Center for Spinal Disorders, Buda Health Center, Királyhágó St. 1-3, Budapest, 1126, Hungary.

Purpose: Percutaneous cement discoplasty (PCD) is a minimally invasive surgical procedure, that can provide a segmental stabilizing and indirect decompression effect in case of severely degenerated discs characterized by vacuum phenomenon. The objective of this study was to evaluate the effects of PCD on spinopelvic radiological parameters and their associations with the clinical outcome.

Methods: Retrospective analysis of prospectively collected dataset of 28 patients (112 lumbar segments) who underwent single- or multilevel PCD was performed. Spinopelvic, intrasegmental and intersegmental parameters were measured on lumbar X-rays pre-, postoperatively and 6 months after the surgery. Correlations between radiological parameters and clinical outcome data were determined.

Results: Sacral slope significantly increased (p < .001), and pelvic tilt (p < .05) was decreased after the PCD procedure. Segmental and total lordosis (p < .05, p < .05) disc and foraminal height showed significantly increase (p < .001, p < .001) after procedure. Pain and disability (ODI) significantly decreased due to PCD. An association was found between postoperative increase in SS and improvement in ODI (r = 0.39, p < .05). The change in low back pain was correlated with segmental scoliosis correction (p < .001). Moderate correlation was detected between the increase in disc height and ODI (p < .05) as well as leg pain (p < .01).

Conclusion: PCD is an effective minimally invasive technique to treat axial pain and disability related to severe lumbar disc degeneration. Our study shows that an improvement in lumbar alignment and a significant indirect foraminal decompression could be achieved with the procedure. These changes can significantly contribute to the pain relief and increase in the patients' functional capacity. These slides can be retrieved under Electronic Supplementary Material.
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http://dx.doi.org/10.1007/s00586-019-05966-7DOI Listing
June 2019

[MEASURING THE FUNCTIONAL IMPAIRMENT OF THE LUMBAR SPINE].

Ideggyogy Sz 2015 Mar;68(3-4):135-41

Background And Purpose: The purpose of our study was to outline the Hungarian validation process of the Oswestry Disability Index, the Quebec Back Pain Disability Scale, the Roland-Morris Disability Questionnaire and the Core Outcome Measurement Index, as well as to draw up recommendations regarding their future applications.

Methods: The Hungarian versions were created after a cultural and linguistic adaptation. Next to the above-mentioned questionnaires, the questionnaire booklet used for validation also contained the WHOQoL-BREF general quality of life questionnaire and a pain measuring Visual Analog Scale. The data of low-back pain patients were registered twice in two weeks. We determined the internal homogeneity (Cronbach alpha), reproducibility, standard error of measurement and the minimal detectable change of the questionnaires. Patients were assigned into different two subgroups (surgical / non-surgical, with/without affection of nerve roots) and differences between the subgroups were examined with the help of the questionnaires. We determined the physical subscale of the WHOQoL-BREF and the correlation between the pain and the studied questionnaires.

Results: The value of Cronbach alpha was between 0.85 and 0.95. All four questionnaires showed significant differences (p<0.001) between the subgroups. The correlation studies brought strong and significant results (p<0.001, r>0.5) in every case. The values of reproducibility were between 0.93-0.92. The results of standard measurement error: 4.8 (Oswestry), 5.2 (Quebec), 1.6 (Roland-Morris), 0.59 (Core Index). The minimal detectable change was 13; 14; 4, and 2 points, respectively.

Conclusion: The Hungarian versions of all four questionnaires are valid. They can be applied with scientific certainty to measure low back pain patients. From the studied questionnaires, we especially recommend the wide-raging application of the Oswestry Disability Index and the Core Outcome Measurement Index based on their psychometric and application features.
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March 2015