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.
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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)