Use of instrumented pedicle screws to evaluate load sharing in posterior dynamic stabilization systems

Meyers, Kathleen N.; Tauber, Michael E.; Sudin, Yuri; Fleischer, Shai; Arnin, Uri; Girardi, Federico P.; Wright, Timothy M.

doi:10.1016/j.spinee.2007.08.008

Cited by 62 publications

(45 citation statements)

References 18 publications

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“…However, the ROM for the rigid instrumentation in the present study is comparable with the ROM reported for rigid instrumentation in the literature [20,25]. Meyers et al evaluated the load sharing in posterior dynamic stabilisation devices using instrumented pedicle screws [17]. They reported a marked interaction between the amount of constraint provided by the device and subsequent load sharing with the spine.…”

Section: Discussionsupporting

confidence: 82%

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Non-fusion instrumentation of the lumbar spine with a hinged pedicle screw rod system: an in vitro experiment

et al. 2009

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In advanced stages of degenerative disease of the lumbar spine instrumented spondylodesis is still the golden standard treatment. However, in recent years dynamic stabilisation devices are being implanted to treat the segmental instability due to iatrogenic decompression or segmental degeneration. The purpose of the present study was to investigate the stabilising effect of a classical pedicle screw/rod combination, with a moveable hinge joint connection between the screw and rod allowing one degree of freedom (cosmicMIA). Six human lumbar spines (L2-5) were loaded in a spine tester with pure moments of ±7.5 Nm in lateral bending, flexion/extension and axial rotation. The range of motion (ROM) and the neutral zone were determined for the following states: (1) intact, (2) monosegmental dynamic instrumentation (L4-5), (3) bisegmental dynamic instrumentation (L3-5), (4) bisegmental decompression (L3-5), (5) bisegmental dynamic instrumentation (L3-5) and (6) bisegmental rigid instrumentation (L3-5). Compared to the intact, with monosegmental instrumentation (2) the ROM of the treated segment was reduced to 47, 40 and 77% in lateral bending, flexion/ extension and axial rotation, respectively. Bisegmental dynamic instrumentation (3) further reduced the ROM in L4-5 compared to monosegmental instrumentation to 25% (lateral bending), 28% (flexion/extension) and 57% (axial rotation). Bisegmental surgical decompression (4) caused an increase in ROM in both segments (L3-4 and L4-5) to approximately 125% and approximately 135% and 187-234% in lateral bending, flexion/extension and axial rotation, respectively. Compared to the intact state, bisegmental dynamic instrumentation after surgical decompression reduced the ROM of the two-bridged segments to 29-35% in lateral bending and 33-38% in flexion/extension. In axial rotation, the ROM was in the range of the intact specimen (87-117%). A rigid instrumentation (6) further reduced the ROM of the two-bridged segments to 20-30, 23-27 and 50-68% in lateral bending, flexion/ extension and axial rotation, respectively. The results of the present study showed that compared to the intact specimen the investigated hinged dynamic stabilisation device reduced the ROM after bisegmental decompression in lateral bending and flexion/extension. Following bisegmental decompression and the thereby caused large rotational instability the device is capable of restoring the motion in axial rotation back to values in the range of the intact motion segments.

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Section: Discussionsupporting

confidence: 82%

“…They reported a marked interaction between the amount of constraint provided by the device and subsequent load sharing with the spine. An increasing constraint of the device (causing a reduction in ROM) resulted in higher pedicle screw loads and therefore a higher risk of loosening at the bone-screw interface [17].…”

Section: Discussionmentioning

confidence: 99%

Non-fusion instrumentation of the lumbar spine with a hinged pedicle screw rod system: an in vitro experiment

et al. 2009

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“…Through the development of new surgical devices, the concept of dynamic stabilization was proposed to reduce the mechanical loading across the intervertebral disc and posterior elements, to limit degeneration and to preserve motion (6,16,17) without the complete immobilization required by fusion surgery. One commonly used dynamic stabilization system is DynesysV R (Zimmer GmbH, Winterthur, Switzerland): it is composed of polyethylene terephthalate cords, polycarbonate urethane spacers of two possible sizes (short and long), and conical titanium alloy pedicle screws.…”

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confidence: 99%

Mid‐term evaluation of the effects of dynamic neutralization system on lumbar intervertebral discs using quantitative molecular MR imaging

Ciavarro

Caiani

Brayda-Bruno

et al. 2011

Magnetic Resonance Imaging

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Purpose: To evaluate the mid-term effects of implant of dynamic neutralization system (Dynesys) on disc tissue in patients with lumbar discopathy, through the quantification of glycosaminoglycans (GAG) concentration, both in treated and adjacent levels, by analysis of delayed gadolinium-enhanced MRI contrast (dGEMRIC) images. Materials and Methods:Ten patients with low back pain underwent the dGEMRIC diagnostic protocol before, 6-months and after 2 years from surgery. Each patient was also evaluated with visual analog (VAS), Oswestry, and Prolo scales both at presurgery and during follow-up. From dGEMRIC images, a DT1 parametric map was obtained for each disc, as quantitative indicator of its GAG concentration, and divided in 13 sectors, which were classified at presurgery as normal or abnormal, based on a 70-ms threshold. Evolution of DT1 was studied during the follow-up.Results: Nine of ten patients completed the follow-up. VAS, Oswestry, and Prolo grades showed an improvement. This was accompanied by a reduction of DT1 in abnormal segments while normal segments showed a pattern of initial worsening at 6 months, followed by an improvement after 2 years. Conclusion:Our study confirmed the improvement in clinical evaluation, and for the first time related this to the changes in discs GAG concentration.

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“…These methods reduce the loading across the intervertebral disk and posterior elements, which relieve pain, limit degeneration, and preserve motion [12,13,19]. DS does not harm the affected disk, and recently, it has been shown that it slows down degeneration by providing a favorable environment for disk regeneration [1,8].…”

Section: Introductionmentioning

confidence: 99%

Posterior dynamic stabilization of the lumbar spine with the Accuflex rod system as a stand-alone device: experience in 20 patients with 2-year follow-up

et al. 2010

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Decompression surgery for lumbar spinal stenosis is a common procedure. After surgery, segmental instability sometimes occurs, therefore, different methods for restabilization have been developed. Dynamic stabilization systems have been designed to improve segmental stability. In this study, clinical results of patients with lumbar spinal stenosis that underwent decompression and stabilization with the Accuflex dynamic system are presented; clinical, radiographic, and magnetic resonance imaging (MRI) findings are fully described. Improvements in all clinical measurements, including visual analog scale for back and leg pain, Oswestry disability index, and SF-36 health status survey were noticed. At a 2-year follow-up, 22.22% of patients required hardware removal due to fatigue while in 83% of them no progression of disk degeneration was observed after implantation of the Accuflex system. Additionally, as demonstrated by the MRI images at follow up, three patients (16%) showed disk rehydration with one grade higher on the Pfirmann classification. Although a relatively high hardware failure was observed (22.22%), the use of the dynamic stabilization system Accuflex posterior to decompression procedures, showed clinical benefits and stopped the degenerative process in 83% the patients.

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Use of instrumented pedicle screws to evaluate load sharing in posterior dynamic stabilization systems

Cited by 62 publications

References 18 publications

Non-fusion instrumentation of the lumbar spine with a hinged pedicle screw rod system: an in vitro experiment

Non-fusion instrumentation of the lumbar spine with a hinged pedicle screw rod system: an in vitro experiment

Mid‐term evaluation of the effects of dynamic neutralization system on lumbar intervertebral discs using quantitative molecular MR imaging

Posterior dynamic stabilization of the lumbar spine with the Accuflex rod system as a stand-alone device: experience in 20 patients with 2-year follow-up

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