Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration
BACKGROUND CONTEXT: Manual contouring of spinal rods is often required intraoperatively for proper alignment of the rods within the pedicle screw heads. Residual misalignments are frequently reduced by using dedicated reduction devices. The forces exerted by these devices, however, are uncontrolled...
| Autores: | , , , , , , , |
|---|---|
| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | Universitat Pompeu Fabra |
| Repositorio: | Repositorio Digital de la UPF |
| OAI Identifier: | oai:repositori.upf.edu:10230/53504 |
| Acceso en línea: | http://hdl.handle.net/10230/53504 http://doi.org/10.1016/j.spinee.2020.09.010 |
| Access Level: | acceso abierto |
| Palabra clave: | Finite element analysis Pedicle screw Rod contouring Spine biomechanics Spinal fusion |
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Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degenerationLoenen, Arjan C. Y.Noriega, David C.Ruiz Will, CarlosNoailly, JérômeNunley, Pierce D.Kirchner, RainerIto, Keitavan Rietbergen, BertFinite element analysisPedicle screwRod contouringSpine biomechanicsSpinal fusionBACKGROUND CONTEXT: Manual contouring of spinal rods is often required intraoperatively for proper alignment of the rods within the pedicle screw heads. Residual misalignments are frequently reduced by using dedicated reduction devices. The forces exerted by these devices, however, are uncontrolled and may lead to excessive reaction forces. As a consequence, screw pullout might be provoked and surrounding tissue may experience unfavorable biomechanical loads. The corresponding loads and induced tissue deformations are however not well identified. Additionally, whether the forced reduction alters the biomechanical behavior of the lumbar spine during physiological movements postoperatively, remains unexplored. PURPOSE: To predict whether the reduction of misaligned posterior instrumentation might result in clinical complications directly after reduction and during a subsequent physiological flexion movement. STUDY DESIGN: Finite element analysis. METHODS: A patient-specific, total lumbar (L1−S1) spine finite element model was available from previous research. The model consists of poro-elastic intervertebral discs with Pfirrmann grade-dependent material parameters, with linear elastic bone tissue with stiffness values related to the local bone density, and with the seven major ligaments per spinal motion segment described as nonlinear materials. Titanium instrumentation was implemented in this model to simulate a L4, L5, and S1 posterolateral fusion. Next, coronal and sagittal misalignments of 6 mm each were introduced between the rod and the screw head at L4. These misalignments were computationally reduced and a physiological flexion movement of 15˚ was prescribed. Non-instrumented and wellaligned instrumented models were used as control groups. RESULTS: Pulling forces up to 1.0 kN were required to correct the induced misalignments of 6 mm. These forces affected the posture of the total lumbar spine, as motion segments were predicted to rotate up to 3 degrees and rotations propagated proximally to and even affect the L1−2 level. The facet contact pressures in the corrected misaligned models were asymmetrical suggesting nonphysiological joint loading in the misaligned models. In addition, the discs and vertebrae experienced abnormally high forces as a result of the correction procedure. These effects were more pronounced after a 15˚ flexion movement following forced reduction. CONCLUSIONS: The results of this study indicate that the correction of misaligned posterior instrumentation can result in high forces at the screws consistent with those reported to cause screw pullout, and may cause high-tissue strains in adjacent and downstream spinal segments. CLINICAL SIGNIFICANCE: Proper alignment of spinal posterior instrumentation may reduce clinical complications secondary to unfavorable biomechanicsElsevier202220222021info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionapplication/pdfapplication/pdfhttp://hdl.handle.net/10230/53504http://doi.org/10.1016/j.spinee.2020.09.010reponame:Repositorio Digital de la UPFinstname:Universitat Pompeu FabraInglésThe Spine Journal. 2021;21(3):528-37.© 2020 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY licensehttp://creativecommons.org/licenses/by/4.0/info:eu-repo/semantics/openAccessoai:repositori.upf.edu:10230/535042026-06-12T07:21:37Z |
| dc.title.none.fl_str_mv |
Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration |
| title |
Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration |
| spellingShingle |
Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration Loenen, Arjan C. Y. Finite element analysis Pedicle screw Rod contouring Spine biomechanics Spinal fusion |
| title_short |
Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration |
| title_full |
Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration |
| title_fullStr |
Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration |
| title_full_unstemmed |
Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration |
| title_sort |
Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration |
| dc.creator.none.fl_str_mv |
Loenen, Arjan C. Y. Noriega, David C. Ruiz Will, Carlos Noailly, Jérôme Nunley, Pierce D. Kirchner, Rainer Ito, Keita van Rietbergen, Bert |
| author |
Loenen, Arjan C. Y. |
| author_facet |
Loenen, Arjan C. Y. Noriega, David C. Ruiz Will, Carlos Noailly, Jérôme Nunley, Pierce D. Kirchner, Rainer Ito, Keita van Rietbergen, Bert |
| author_role |
author |
| author2 |
Noriega, David C. Ruiz Will, Carlos Noailly, Jérôme Nunley, Pierce D. Kirchner, Rainer Ito, Keita van Rietbergen, Bert |
| author2_role |
author author author author author author author |
| dc.subject.none.fl_str_mv |
Finite element analysis Pedicle screw Rod contouring Spine biomechanics Spinal fusion |
| topic |
Finite element analysis Pedicle screw Rod contouring Spine biomechanics Spinal fusion |
| description |
BACKGROUND CONTEXT: Manual contouring of spinal rods is often required intraoperatively for proper alignment of the rods within the pedicle screw heads. Residual misalignments are frequently reduced by using dedicated reduction devices. The forces exerted by these devices, however, are uncontrolled and may lead to excessive reaction forces. As a consequence, screw pullout might be provoked and surrounding tissue may experience unfavorable biomechanical loads. The corresponding loads and induced tissue deformations are however not well identified. Additionally, whether the forced reduction alters the biomechanical behavior of the lumbar spine during physiological movements postoperatively, remains unexplored. PURPOSE: To predict whether the reduction of misaligned posterior instrumentation might result in clinical complications directly after reduction and during a subsequent physiological flexion movement. STUDY DESIGN: Finite element analysis. METHODS: A patient-specific, total lumbar (L1−S1) spine finite element model was available from previous research. The model consists of poro-elastic intervertebral discs with Pfirrmann grade-dependent material parameters, with linear elastic bone tissue with stiffness values related to the local bone density, and with the seven major ligaments per spinal motion segment described as nonlinear materials. Titanium instrumentation was implemented in this model to simulate a L4, L5, and S1 posterolateral fusion. Next, coronal and sagittal misalignments of 6 mm each were introduced between the rod and the screw head at L4. These misalignments were computationally reduced and a physiological flexion movement of 15˚ was prescribed. Non-instrumented and wellaligned instrumented models were used as control groups. RESULTS: Pulling forces up to 1.0 kN were required to correct the induced misalignments of 6 mm. These forces affected the posture of the total lumbar spine, as motion segments were predicted to rotate up to 3 degrees and rotations propagated proximally to and even affect the L1−2 level. The facet contact pressures in the corrected misaligned models were asymmetrical suggesting nonphysiological joint loading in the misaligned models. In addition, the discs and vertebrae experienced abnormally high forces as a result of the correction procedure. These effects were more pronounced after a 15˚ flexion movement following forced reduction. CONCLUSIONS: The results of this study indicate that the correction of misaligned posterior instrumentation can result in high forces at the screws consistent with those reported to cause screw pullout, and may cause high-tissue strains in adjacent and downstream spinal segments. CLINICAL SIGNIFICANCE: Proper alignment of spinal posterior instrumentation may reduce clinical complications secondary to unfavorable biomechanics |
| publishDate |
2021 |
| dc.date.none.fl_str_mv |
2021 2022 2022 |
| dc.type.none.fl_str_mv |
info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion |
| format |
article |
| status_str |
publishedVersion |
| dc.identifier.none.fl_str_mv |
http://hdl.handle.net/10230/53504 http://doi.org/10.1016/j.spinee.2020.09.010 |
| url |
http://hdl.handle.net/10230/53504 http://doi.org/10.1016/j.spinee.2020.09.010 |
| dc.language.none.fl_str_mv |
Inglés |
| language_invalid_str_mv |
Inglés |
| dc.relation.none.fl_str_mv |
The Spine Journal. 2021;21(3):528-37. |
| dc.rights.none.fl_str_mv |
http://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess |
| rights_invalid_str_mv |
http://creativecommons.org/licenses/by/4.0/ |
| eu_rights_str_mv |
openAccess |
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application/pdf application/pdf |
| dc.publisher.none.fl_str_mv |
Elsevier |
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Elsevier |
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reponame:Repositorio Digital de la UPF instname:Universitat Pompeu Fabra |
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Universitat Pompeu Fabra |
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Repositorio Digital de la UPF |
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Repositorio Digital de la UPF |
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