Finite element simulation and clinical follow-up of lumbar spine biomechanics with dynamic fixations

PLOS ONE, Nov 2019

Arthrodesis is a recommended treatment in advanced stages of degenerative disc disease. Despite dynamic fixations were designed to prevent abnormal motions with better physiological load transmission, improving lumbar pain and reducing stress on adjacent segments, contradictory results have been obtained. This study was designed to compare differences in the biomechanical behaviour between the healthy lumbar spine and the spine with DYNESYS and DIAM fixation, respectively, at L4-L5 level. Behaviour under flexion, extension, lateral bending and axial rotation are compared using healthy lumbar spine as reference. Three 3D finite element models of lumbar spine (healthy, DYNESYS and DIAM implemented, respectively) were developed, together a clinical follow-up of 58 patients operated on for degenerative disc disease. DYNESYS produced higher variations of motion with a maximum value for lateral bending, decreasing intradiscal pressure and facet joint forces at instrumented level, whereas screw insertion zones concentrated stress. DIAM increased movement during flexion, decreased it in another three movements, and produced stress concentration at the apophyses at instrumented level. Dynamic systems, used as single systems without vertebral fusion, could be a good alternative to degenerative disc disease for grade II and grade III of Pfirrmann.

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Finite element simulation and clinical follow-up of lumbar spine biomechanics with dynamic fixations

November Finite element simulation and clinical follow- up of lumbar spine biomechanics with dynamic fixations Yolanda Ma s 0 1 2 Luis Gracia 0 1 2 Elena Ibarz 0 1 2 Sergio Gabarre 0 1 2 Diego Peña 0 2 Antonio Herrera 0 2 0 Abbreviations: 3D, Three-Dimensional; DDD , Degenerative disc disease; MRI, Magnetic Resonance Imaging; ALIF, Anterior lumbar 1 Department of Mechanical Engineering, University of Zaragoza , Zaragoza , Spain , 2 AragoÂn Institute of Engineering Research , Zaragoza , Spain , 3 Spine Unit, Department of Orthopaedic Surgery and Traumatology, Miguel Servet University Hospital , Zaragoza , Spain , 4 AragoÂn Health Research Institute , Zaragoza , Spain , 5 Department of Surgery, School of Medicine, University of Zaragoza , Zaragoza , Spain 2 Editor: Dragana Nikitovic, University of Crete , GREECE Arthrodesis is a recommended treatment in advanced stages of degenerative disc disease. Despite dynamic fixations were designed to prevent abnormal motions with better physiological load transmission, improving lumbar pain and reducing stress on adjacent segments, contradictory results have been obtained. This study was designed to compare differences in the biomechanical behaviour between the healthy lumbar spine and the spine with DYNESYS and DIAM fixation, respectively, at L4-L5 level. Behaviour under flexion, extension, lateral bending and axial rotation are compared using healthy lumbar spine as reference. Three 3D finite element models of lumbar spine (healthy, DYNESYS and DIAM implemented, respectively) were developed, together a clinical follow-up of 58 patients operated on for degenerative disc disease. DYNESYS produced higher variations of motion with a maximum value for lateral bending, decreasing intradiscal pressure and facet joint forces at instrumented level, whereas screw insertion zones concentrated stress. DIAM increased movement during flexion, decreased it in another three movements, and produced stress concentration at the apophyses at instrumented level. Dynamic systems, used as single systems without vertebral fusion, could be a good alternative to degenerative disc disease for grade II and grade III of Pfirrmann. - Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: The authors received no specific funding for this work. Competing interests: The authors have declared that no competing interests exist. Introduction A lot of patients suffer low back pain in some of them with chronic evolution. Lumbar pain can have multiple etiologies, in some cases unidentified. One of the most prevalent etiologies of lumbar pain is degenerative disc disease (DDD) [ 1 ]. The etiology of DDD is multifactorial, in its production they influence, among other: the age, sedentary lifestyle, toxic habits, obesity [ 2 ], loads supported [ 3 ] which in addition can activate the inflammatory and enzymatic processes which play an important role in the degeneration [4±6] movements during flexion [ 7 ] and the genetics of each individual [ 8, 9 ], with particular relevance of the genetic polymorphisms [ 10, 11 ]. Most patients exhibit grades IV and V of Pfirrmann [ 12 ] in magnetic resonance imaging (MRI) and evident signs of facet arthrosis leaving instability as the only remaining aspect to improve with surgical treatment. Lumbar spinal fusion is a standardized and widely accepted procedure for the treatment of discogenic back pain, showing good results in the long term. It can be achieved through anterior lumbar interbody fusion (ALIF), postero-lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), lateral lumbar interbody fusion (XLIF), non-instrumented posterolateral fusion and circumferential interbody fusion by double approach (anterior and posterior). The question which remains is if adjacent segment disease (ASD) is produced by agerelated degeneration or if it is a consequence of the previous fusion. [ 13 ]. As it has been reported, ASD has a multifactorial etiology [13±17]. In order to avoid or minimize the occurrence of ASD, several alternative techniques in the treatment of disc degeneration (DD) have emerged including: arthroplasty of facet joints [ 18 ], total disc replacement (TDR) and dynamic fixation (DF). Nowadays, DF is the most used among these techniques. Dynamic fixations can be used as a surgical treatment system for degenerative disc disease or as a hybrid system, combined with circumferential fusion, to reduce a further progression of degeneration in the adjacent discs to fusion [19±21]. During last years, the two most employed systems are: the DIAM fixator (Device for Intervertebral Assisted Motion) [ 22 ], used as an interspinous spacer and the dynamic neutralization system (DYNESYS) [ 21 ], although nowadays Dynesys continues being used and the use of interspinous spacers has diminished, including DIAM. Although in vitro and clinical studies in the mid-term (...truncated)


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Yolanda Más, Luis Gracia, Elena Ibarz, Sergio Gabarre, Diego Peña, Antonio Herrera. Finite element simulation and clinical follow-up of lumbar spine biomechanics with dynamic fixations, PLOS ONE, 2017, Volume 12, Issue 11, DOI: 10.1371/journal.pone.0188328