Publications by authors named "Benjamin Hajnal"

4 Publications

  • Page 1 of 1

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

Glycine transporter inhibitors: A new avenue for managing neuropathic pain.

Brain Res Bull 2019 10 11;152:143-158. Epub 2019 Jul 11.

Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary.

Interneurons operating with glycine neurotransmitter are involved in the regulation of pain transmission in the dorsal horn of the spinal cord. In addition to interneurons, glycine release also occurs from glial cells neighboring glutamatergic synapses in the spinal cord. Neuronal and glial release of glycine is controlled by glycine transporters (GlyTs). Inhibitors of the two isoforms of GlyTs, the astrocytic type-1 (GlyT-1) and the neuronal type-2 (GlyT-2), decrease pain sensation evoked by injuries of peripheral sensory neurons or inflammation. The function of dorsal horn glycinergic interneurons has been suggested to be reduced in neuropathic pain, which can be reversed by GlyT-2 inhibitors (Org-25543, ALX1393). Several lines of evidence also support that peripheral nerve damage or inflammation may shift glutamatergic neurochemical transmission from N-methyl-D aspartate (NMDA) NR1/NR2A receptor- to NR1/NR2B receptor-mediated events (subunit switch). This pathological overactivation of NR1/NR2B receptors can be reduced by GlyT-1 inhibitors (NFPS, Org-25935), which decrease excessive glycine release from astroglial cells or by selective antagonists of NR2B subunits (ifenprodil, Ro 25-6981). Although several experiments suggest that GlyT inhibitors may represent a novel strategy in the control of neuropathic pain, proving this concept in human beings is hampered by lack of clinically applicable GlyT inhibitors. We also suggest that drugs inhibiting both GlyT-1 and GlyT-2 non-selectively and reversibly, may favorably target neuropathic pain. In this paper we overview inhibitors of the two isoforms of GlyTs as well as the effects of these drugs in experimental models of neuropathic pain. In addition, the possible mechanisms of action of the GlyT inhibitors, i.e. how they affect the neurochemical and pain transmission in the spinal cord, are also discussed. The growing evidence for the possible therapeutic intervention of neuropathic pain by GlyT inhibitors further urges development of drugable compounds, which may beneficially restore impaired pain transmission in various neuropathic conditions.
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http://dx.doi.org/10.1016/j.brainresbull.2019.07.008DOI Listing
October 2019
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