Abstract
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.
Highlights
A lot of patients suffer low back pain in some of them with chronic evolution
Results for Interdiscal pressure (IDP) are in good agreement with previous published results: dynamic neutralization system (DYNESYS) decreased IDP at the instrumented level and the facet joint forces at implant level [34] with no significant changes in IDP seen in the adjacent discs [20]
IDP decrease and the stabilization of the stresses on adjacent vertebrae is a positive factor in avoiding the appearance of adjacent segment disease (ASD)
Summary
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 [4,5,6] movements during flexion [7]. 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 FE simulation and clinical follow-up of lumbar spine dynamic fixations interbody fusion; PLIF, Postero-lumbar interbody fusion; TLIF, Transforaminal lumbar interbody fusion; XLIF, lateral lumbar interbody fusion; ASD, Adjacent Segment Disease; DD, Disc Degeneration; TRD, Total disc replacement; DF, Dynamic fixation; DIAM, Device for intervertebral assisted motion; ROM, Range of motion; FE, Finite element; PEEK, Polyether ether ketone; PCU, Polycarbonateurethane; PET, Polyethylene-terephthalate; IDP, Interdiscal Pressure; L1, First lumbar vertebrae; L2, Second lumbar vertebrae; L3, Third lumbar vertebrae; L4, Fourth lumbar vertebrae; L5, Fifth lumbar vertebrae; S1, First sacral vertebrae; SASD, Symptomatic Adjacent Segment Disease; RASD, Radiographic Adjacent Segment Disease.
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