Interspinous Process Devices Research Articles

Current concepts of spondylosis and posterior spinal motion preservation for radiologists.

Spinal fusion is performed to eliminate motion at a degenerated or unstable segment. However, this is associated with loss of motion at the fused levels and increased stress on adjacent levels. Motion-preserving implants have been designed in effort to mitigate the limitations of fusion. This review will focus on posterior spinal motion-preserving technologies. In the cervical spine, laminoplasty is a posterior motion-preserving procedure used in the management of myelopathy/cord compression. In the lumbar spine, motion-sparing systems include interspinous process devices (also referred to as interspinous process spacers or distraction devices), posterior dynamic stabilization devices (also referred to as pedicle screw/rod fixation-based systems), and posterior element replacement systems (also referred to as total facet replacement devices). Knowledge of the intended physiologic purpose, hardware utilized, and complications is important in the assessment of imaging in those who have undergone posterior motion preservation procedures.

Biomechanical analysis of lumbar fusion with proximal interspinous process device implantation.

Lumbar spinal fusion may cause adjacent segment degeneration (ASD) in the long term. Recently, inserting an interspinous process device (IPD) proximal to the fusion has been proposed to prevent ASD. The aim of this study was to investigate the biomechanics of lumbar fusion with proximal IPD implantation (LFPI) under both static loads and whole body vibration (WBV). A previously validated finite element (FE) model of the L1-5 lumbar spine was modified to simulate L4-5 fusion. Three different IPDs (Coflex-F, Wallis and DIAM) were inserted at the L3-4 segment of the fusion model to construct the LFPI models. The intact and surgical FE models were analyzed under static loads and WBV, respectively. Under static loading conditions, LFPI decreased range of motion (ROM) and intradiscal pressure (IDP) at the transition segment L3-4 compared with the fusion case. At the segment (L2-3) adjacent to the transition level, LFPI induced higher motion and IDP than rigid fusion. Under WBV, vibration amplitudes of the L3-4 IDP and L4-5 facet joint force (FJF) decreased by more than 54.3% after surgery. The LFPI model with the DIAM system offered the most comparable biomechanics to the intact model under static loads, and decreased the dynamic responses of the L4-5 FJF under WBV. The LFPI model with the Wallis and Coflex-F systems could stabilize the transition segment, and decrease dynamic responses of the L3-4 IDP. The DIAM system may be more suitable in LFPI.

Real world adverse events of interspinous spacers using Manufacturer and User Facility Device Experience data.

BackgroundLumbar spinal stenosis is a condition of progressive neurogenic claudication that can be managed with lumbar decompression surgery or less invasive interspinous process devices after failed conservative therapy. Popular interspinous process spacers include X-Stop, Vertiflex and Coflex, with X-Stop being taken off market due to its adverse events profile.MethodsA disproportionality analysis was conducted to determine whether a statistically significant signal exists in the three interspinous spacers and the reported adverse events using the Manufacturer and User Facility Device Experience (MAUDE) database maintained by the US Food and Drug Administration.ResultsStatistically significant signals were found with each of the three interspinous spacer devices (Coflex, Vertiflex, and X-Stop) and each of the following adverse events: fracture, migration, and pain/worsening symptoms.ConclusionsFurther studies such as randomized controlled trials are needed to validate the findings.

Interspinous Process (ISP) Devices in Comparison to the Use of Traditional Posterior Spinal Instrumentation.

A systematic literature review was conducted on studies comparing interspinous process (ISP) devices to traditional methods of posterior spinal instrumentation (pedicle screw-rod construct), in terms of indications of use, complications, pain assessment, estimated blood loss, length of hospital stay, reoperation rates, and return to work. The objective was to analyze, evaluate and summarize the current published literature on the proposed efficacy and clinical and surgical long-term outcomes of the ISP device in comparison to the traditional posterior spinal instrumentation (pedicle screw-rod construct). The ISP device is a minimally invasive and less disruptive alternative to traditional methods of posterior spinal instrumentation (pedicle screw-rod construct). However, very few published literature studies to date have reported the comparison of ISPs in terms of efficacy and clinical and surgical outcomes, to traditional posterior spinal instrumentation.A systematic literature review was performed in PubMed and Google Scholar to evaluate the results of published research that meet the defined inclusion and exclusion criteria and to analyze clinical indications and surgical outcomes of the ISP device compared to traditional methods of posterior spinal instrumentation (pedicle screw-rod construct). Inclusion criteria included keywords such as “ISP device, ISP, posterior spinal instrumentation, pedicle screw fixation, bilateral pedicle screws, interbody fusion with posterior spinal instrumentation, lumbar spinal stenosis, and posterior lumbar stability.” No exclusion criteria keywords were included in this literature review.ISPs provide a high degree of spinal stability in multiple planes, including a decreased range of motion restriction in flexion-extension, and comparable results to bilateral pedicle screw (BPS) in axial rotation. The use of the ISP device in adjunct with an interbody fusion, ensures less estimated operative blood loss (EBL), shorter operative time, less bony exposure without the need for extensive soft tissue or muscle retraction, a decrease in the rate of pseudoarthrosis, and a shorter length of hospital stay (LOHS) when compared to the traditional posterior instrumentation (pedicle screw-rod construct).Based on the various published literature reviews noted throughout this research paper, it is safe to conclude, that an ISP device that is accompanied by interbody fusion, including posterior approaches posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF); anterior approaches such as anterior interbody fusion (ALIF), and lateral approaches including direct lateral interbody fusion (DLIF), lateral lumbar interbody fusion (LLIF), extreme lateral interbody fusion (XLIF), is considered a credible and an effective minimally invasive option for the treatment of mild to moderate lumbar stenosis and stable low-grade spondylolisthesis (less than two) when compared to the traditional posterior spinal instrumentation of a pedicle screw-rod construct. Surgeons that are relatively new to the ISP technologies for spinal instrumentation would likely benefit from more clinical and surgical evidence of safety and efficacy in published peer-reviewed medical literature. Further clinical trials are needed to manifest the efficacy of ISPs regarding postoperative outcomes when compared to traditional posterior instrumentation techniques (pedicle screw-rod construct) with adjunct interbody fusions.

Effect of different designs of interspinous process devices on the instrumented and adjacent levels after double-level lumbar decompression surgery: A finite element analysis.

Recently, various designs and material manufactured interspinous process devices (IPDs) are on the market in managing symptomatic lumbar spinal stenosis (LSS). However, atraumatic fracture of the intervening spinous process has been reported in patients, particularly, double or multiple level lumbar decompression surgery with IPDs. This study aimed to biomechanically investigate the effects of few commercial IPDs, namely DIAMTM, CoflexTM, and M-PEEK, which were implanted into the L2-3, L3-4 double-level lumbar spinal processes. A validated finite element model of musculoskeletal intact lumbar spinal column was modified to accommodate the numerical analysis of different implants. The range of motion (ROM) between each vertebra, stiffness of the implanted level, intra stress on the intervertebral discs and facet joints, and the contact forces on spinous processes were compared. Among the three implants, the Coflex system showed the largest ROM restriction in extension and caused the highest stress over the disc annulus at the adjacent levels, as well as the sandwich phenomenon on the spinous process at the instrumented levels. Further, the DIAM device provided a superior loading-sharing between the two bridge supports, and the M-PEEK system offered a superior load-sharing from the superior spinous process to the lower pedicle screw. The limited motion at the instrumented segments were compensated by the upper and lower adjacent functional units, however, this increasing ROM and stress would accelerate the degeneration of un-instrumented segments.

Three-Dimensional Volumetric Changes and Clinical Outcomes after Decompression with DIAM™ Implantation in Patients with Degenerative Lumbar Spine Diseases.

Background and objectives: The prevalence of degenerative lumbar spine diseases has increased. In addition to standard lumbar decompression and/or fusion techniques, implantation of interspinous process devices (IPDs) can provide clinical benefits in highly selected patients. However, changes in spinal structures after IPD implantation using magnetic resonance imaging (MRI) have rarely been discussed. This volumetric study aimed to evaluate the effect of IPD implantation on the intervertebral disc and foramen using three-dimensional assessment. Materials and Methods: We retrospectively reviewed patients with lumbar degenerative disc diseases treated with IPD implantation and foraminotomy and/or discectomy between January 2016 and December 2019. The mean follow-up period was 13.6 months. The perioperative lumbar MRI data were processed for 3D-volumetric analysis. Clinical outcomes, including the Prolo scale and visual analog scale (VAS) scores, and radiographic outcomes, such as the disc height, foraminal area, and translation, were analyzed. Results: Fifty patients were included in our study. At the one-year follow-up, the VAS and Prolo scale scores significantly improved (both p < 0.001). The disc height and foraminal area on radiographs also increased significantly, but with limited effects up to three months postoperatively. MRI revealed an increased postoperative disc height with a mean difference of 0.5 ± 0.1 mm (p < 0.001). Although the mean disc volume difference did not significantly increase, the mean foraminal volume difference was 0.4 ± 0.16 mm3 (p < 0.05). Conclusions: In select patients with degenerative disc diseases or lumbar spinal stenosis, the intervertebral foramen was enlarged, and disc loading was reduced after IPD implantation with decompression surgery. The 3D findings were compatible with the clinical benefits.

Biomechanical analysis of a newly developed interspinous process device conjunction with interbody cage based on a finite element model.

PurposeThis study aimed to investigate the biomechanical effects of a newly developed interspinous process device (IPD), called TAU. This device was compared with another IPD (SPIRE) and the pedicle screw fixation (PSF) technique at the surgical and adjacent levels of the lumbar spine.Materials and methodsA three-dimensional finite element model analysis of the L1-S1 segments was performed to assess the biomechanical effects of the proposed IPD combined with an interbody cage. Three surgical models—two IPD models (TAU and SPIRE) and one PSF model—were developed. The biomechanical effects, such as range of motion (ROM), intradiscal pressure (IDP), disc stress, and facet loads during extension were analyzed at surgical (L3-L4) and adjacent levels (L2-L3 and L4-L5). The study analyzed biomechanical parameters assuming that the implants were perfectly fused with the lumbar spine.ResultsThe TAU model resulted in a 45%, 49%, 65%, and 51% decrease in the ROM at the surgical level in flexion, extension, lateral bending, and axial rotation, respectively, when compared to the intact model. Compared to the SPIRE model, TAU demonstrated advantages in stabilizing the surgical level, in all directions. In addition, the TAU model increased IDP at the L2-L3 and L4-L5 levels by 118.0% and 78.5% in flexion, 92.6% and 65.5% in extension, 84.4% and 82.3% in lateral bending, and 125.8% and 218.8% in axial rotation, respectively. Further, the TAU model exhibited less compensation at adjacent levels than the PSF model in terms of ROM, IDP, disc stress, and facet loads, which may lower the incidence of the adjacent segment disease (ASD).ConclusionThe TAU model demonstrated more stabilization at the surgical level than SPIRE but less stabilization than the PSF model. Further, the TAU model demonstrated less compensation at adjacent levels than the PSF model, which may lower the incidence of ASD in the long term. The TAU device can be used as an alternative system for treating degenerative lumbar disease while maintaining the physiological properties of the lumbar spine and minimizing the degeneration of adjacent segments.

Which is the most effective treatment for lumbar spinal stenosis: Decompression, fusion, or interspinous process device? A Bayesian network meta-analysis.

SummaryObjectiveTo compare the clinical efficacy, complications, and reoperation rates among three major treatments for lumbar spinal stenosis (LSS): decompression, fusion, and interspinous process device (IPD), using a Bayesian network meta-analysis.Materials and methodsDatabases including Pubmed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science were used for the literature search. Randomized Controlled Trials (RCTs) with three treatment methods were reviewed and included in the study. R software (version 3.6.0), Stata (version 14.0), and Review Manager (version 5.3) were used to perform data analysis.ResultsA total of 10 RCTs involving 1254 patients were enrolled in the present study and each study met an acceptable quality according to our quality assessment described later. In direct comparison, IPD exhibited a higher incidence of reoperation than fusion (OR ​= ​2.93, CI: 1.07–8.02). In indirect comparison, the rank of VAS leg (from best to worst) was as follows: IPD (64%) ​> ​decompression (25%) ​> ​fusion (11%), and the rank of ODI (from best to worst) was: IPD (84%) ​> ​fusion (13%) ​> ​decompression (4%). IPD had the lowest incidence of complications; the rank of complications (from best to worst) was: IPD (60%) ​> ​decompression (27%) ​> ​fusion (14%). However, for the rank of reoperation, fusion showed the best results (from best to worst): fusion (79%) ​> ​decompression (20%) ​> ​IPD (1%). Consistency tests at global and local level showed satisfactory results and heterogeneity tests using loop text indicated a favorable stability.ConclusionThe present study preliminarily indicates that non-fusion methods including decompression and IPD are optimal choices for treating LSS, which achieves favorable clinical outcomes. IPD exhibits a low incidence of complications, but its high rate of reoperation should be treated with caution.The translational potential of this articleFor the treatment of LSS, several procedures including decompression, fusion, and IPD have been reported. However, each method has its own advantages and disadvantages. To date, the golden standard treatment for LSS is still controversial. In this network meta-analysis, our results demonstrate that both decompression and IPD obtain satisfactory clinical effects for LSS. IPD is accompanied with a low incidence of complications, however, its high rate of reoperation should be acknowledged with discretion.

Nerve Root Sedimentation Sign: Can It Predict the Success for Surgical Intervention in Patients With Symptomatic Lumbar Spinal Stenosis?

Introduction: The use of interspinous process devices are less invasive surgical methods designed to manage mild to moderate lumbar spinal stenosis symptoms. Symptomatic relief may not be seen in all patients undergoing this procedure. Magnetic resonance imaging (MRI) parameters have been used to predict the success of clinical outcomes in patients with symptomatic lumbar spinal stenosis for decompressive surgeries. The purpose of this study was to determine the feasibility of using nerve root sedimentation sign to predict mid- to long-term clinical outcomes of patients treated with interspinous spacers for lumbar spinal stenosis.Methods: This was a retrospective study using prospective multicenter Food and Drug Administration Investigational Device Exemption (FDA IDE) trial (Superion™ and X-STOP®) data. Inclusion criteria were patients treated with interspinous spacers, aged 45 or older with lumbar spinal stenosis at one or more contiguous levels from L1 to L5 and symptoms of neurogenic claudication. Preoperative axial T2 weighted MRI images were used to determine nerve root sedimentation sign. Preoperative, six-week, one- and two-year postoperative clinical outcomes were measured using Oswestry Disability Index (ODI) scores. Clinical outcomes were compared between positive and negative nerve root sedimentation sign groups; p ≤0.05 was considered significant.Results: This study included n=374 patients; 40 excluded; 334 included (113=positive nerve root sedimentation sign (NRSS) (34%) and 221=negative NRSS (66%)). At six weeks, significant postoperative ODI correction was noted in both groups (p<0.001). No significant differences in ODI scores were identified between groups. A subgroup analysis with MRI image quality grade 3 and certainty determination grade 5, six-week postoperative ODI correction was significant in both groups. Six-week, one- and two-year postoperative ODI scores were greater by 6 points in the positive nerve root sedimentation sign group compared to the negative nerve root sedimentation sign group.Conclusions: Although satisfactory postoperative improvement occurred in both groups, there were statistically significant differences noted in certain sub-categories. The subgroup analysis indicated MRI image quality and nerve root sedimentation sign certainty of determination may be factors that may aid with planning the surgical management of lumbar spinal stenosis.

Are Outcomes of Studies of Interspinous Process Devices Biased by Industry Funding?

Are Outcomes of Studies of Interspinous Process Devices Biased by Industry Funding?

Adult lumbar spondylolisthesis: Interspinous devices

As minimally invasive surgery has become increasingly popular, interspinous process devices (IPDs) have evolved beyond cases of simple focal spinal stenosis. Despite design differences, all IPDs aim to achieve indirect decompression of the nerve roots by enlarging the caliber of the neural foramina via distraction of the adjacent spinous processes. Whether IPDs reduce the risk of adjacent level stenosis compared to decompression and fusion for degenerative spondylolisthesis remains unclear. Ultimately, the paucity of high-quality, long-term, comparative, clinical studies precludes any strong recommendation for the use of IPDs for the treatment of degenerative spondylolisthesis.

Functional and radiographic evaluation of an interspinous device as an adjunct for lumbar interbody fusion procedures.

In the last decades, several interspinous process devices were designed as a minimally invasive treatment option for spinal stenosis. In order to minimise surgical trauma, interspinous process devices were recently discussed as an alternative posterior fixation in vertebral interbody fusions. Therefore, the purpose of this study was to evaluate the effect of a newly designed interspinous device with polyester bands (PBs) on range of motion (RoM) and centre of rotation (CoR) of a treated motion segment in comparison with an established interspinous device with spikes (SC) as well as with pedicle screw instrumentation in lumbar fusion procedures. Flexibility tests with an applied pure moment load of 7.5 Nm were performed in six monosegmental thoracolumbar functional spinal units (FSUs) in the following states: (a) native, (b) native with PB device, (c) intervertebral cage with PB device, (d) cage with SC and (e) cage with internal fixator. The resulting RoM was normalised to the native RoM. The CoR was determined of X-ray images taken in maximal flexion and extension during testing. In flexion and extension, the PB device without and with the cage reduced the RoM of the native state to 58% [standard deviation (SD) 17.8] and 53% (SD 15.7), respectively. The SC device further reduced the RoM to 27% (SD 16.8), while the pedicle screw instrumentation had the most reducing effect to 17% (SD 17.2) (p < 0.01). In lateral bending and axial rotation, the interspinous devices had the least effect on the RoM. Compared to the native state, for all instrumentations the CoR showed a small shift towards cranial. In the anterior-posterior direction, the SC device and the pedicle screw instrumentation shifted the CoR towards the posterior wall. The interspinous devices significantly reduced the RoM in flexion/extension, while in axial rotation and lateral bending only the internal fixator had a significant effect on the RoM.

Mobility-Preserving Surgery for Lumbar Spinal Stenosis: WFNS Spine Committee Recommendations

BackgroundAlthough decompression is the basis of surgical treatment for lumbar spinal stenosis (LSS), under various circumstances instrumented fusion is performed as well. The rationale for mobility-preserving operations for LSS is preventing adjacent segment disease (ASD). We review the rationale for mobility preservation in ASD and discuss related topics such as indications for fusion and the evolving role of minimally invasive approaches to lumbar spine decompression. Our focus is on systematic review and consensus discussion of mobility-preserving surgical methods as related to surgery for LSS.MethodsGroups of spinal surgeons (members of the World Federation of Neurosurgical Societies Spine Committee) performed systematic reviews of dynamic fixation systems, including hybrid constructs, and of interspinous process devices; consensus statements were generated based on the reviews at 2 voting sessions by the committee several months apart. Additional review of background data was performed, and the results summarized in this review.ResultsDecompression is the basis of surgical treatment of LSS. Fusion is an option, especially when spondylolisthesis or instability are present, but indications remain controversial. ASD incidence reports show high variability. ASD may represent the natural progression of degenerative disease in many cases. Older age, poor sagittal balance, and multilevel fusion may be associated with more ASD. Dynamic fixation constructs are treatment options that may help prevent ASD.

Minimally Invasive Lumbar Decompression and Interspinous Process Device for the Management of Symptomatic Lumbar Spinal Stenosis: a Literature Review

Symptomatic lumbar spinal stenosis (LSS) is a condition affecting a growing number of individuals resulting in significant disability and pain. Traditionally, treatment options have consisted of conservative measures such as physical therapy, medication management, epidural injections and percutaneous adhesiolysis, or surgery. There exists a treatment gap for patients failing conservative measures who are not candidates for surgery. Minimally invasive lumbar decompression (MILD®) and interspinous process device (IPD) with Superion® represent minimally invasive novel treatment options that may help fill this gap in management. We performed a literature review to separately evaluate these procedures and assess the effectiveness and safety. The available evidence for MILD and Superion has been continuously debated. Overall, it is considered that while the procedures are safe, there is only modest evidence for effectiveness. For both procedures, we have reviewed 13 studies. Based on the available evidence, MILD and Superion are safe and modestly effective minimally invasive procedures for patients with symptomatic LSS.It is our recommendation that these procedures may be incorporated as part of the continuum of treatment options for patients meeting clinicalcriteria.

Axial loading during MRI reveals insufficient effect of percutaneous interspinous implants (Aperius\u2122 PerCLID\u2122) on spinal canal area

PurposeTo evaluate the effect on the spinal canal at the treated and adjacent level(s), in patients treated for lumbar spinal stenosis (LSS) with percutaneous interspinous process device (IPD) Aperius™ or open decompressive surgery (ODS), using axial loading of the spine during MRI (alMRI).MaterialsNineteen LSS patients (mean age 67 years, range 49–78) treated with IPDs in 29 spine levels and 13 LSS patients (mean age 63 years, range 46–76) operated with ODS in 22 spine levels were examined with alMRI pre- and 3 months postoperatively. Radiological effects were evaluated by measuring the dural sac cross-sectional area (DSCSA) and by morphological grading of nerve root affection.ResultsFor the IPD group, no DSCSA increase was observed at the operated level (p = 0.42); however, a decrease was observed in adjacent levels (p = 0.05). No effect was seen regarding morphological grading (operated level: p = 0.71/adjacent level: p = 0.94). For the ODS group, beneficial effects were seen for the operated level, both regarding DSCSA (p < 0.001) and for morphological grading (p < 0.0001). No changes were seen for adjacent levels (DSCSA; p = 0.47/morphological grading: p = 0.95). Postoperatively, a significant difference between the groups existed at the operated level regarding both evaluated parameters (p < 0.003).ConclusionsWith the spine imaged in an axial loaded position, no significant radiological effects of an IPD could be detected postoperatively at the treated level, while increased DSCSA was displayed for the ODS group. In addition, reduced DSCSA in adjacent levels was detected for the IPD group. Thus, the beneficial effects of IPD implants on the spinal canal must be questioned.Graphic abstractThese slides can be retrieved under Electronic Supplementary Material.

Percutaneous Interspinous Spacer in Spinal-Canal-Stenosis Treatment: Pros and Cons.

A comprehensive description of the literature regarding interspinous process devices (IPD) mainly focused on comparison with conservative treatment and surgical decompression for the treatment of degenerative lumbar spinal stenosis. Recent meta-analysis and articles are listed in the present article in order to establish IPD pros and cons.

An Affordable and Feasible Technique for Minimally Invasive Tubular Lumbar Discectomy

The benefits of minimally invasive spine surgery are attainable only if hospitals have the financial resources to acquire essential equipment. We present a surgical approach readily available to countries where unacceptably expensive materials are the main limitation for use of minimally invasive spine surgery. This retrospective study included 30 patients who underwent minimally invasive spine surgery using syringes as dilators and retractors for posterior lumbar approaches. Inclusion criteria were lumbar radicular/back pain, degenerative disc, spondylolysis, unilateral approach, and maximum of 2 affected spine levels. Demographic characteristics, affected radicular level, diagnosis, type and length of surgery, hospital length of stay, MacNab criteria, complications, and resumption of daily activities were analyzed. Of 30 patients, 17 (56.6%) presented with S1 radicular pain. Pain was mainly due to posterolateral hernia (70%; n= 21) requiring 1-level discectomy. In 6 patients (20%), discectomy and an interspinous process device were required. One patient (3.33%) underwent 2-level discectomy. All surgeries were performed using syringes as dilators and retractors. Maximum syringe diameter used was 2 cm (20-mL syringes) in 29 patients (96.6%) and 3 cm (60-mL syringe) in 1 patient. Average length of surgery was 1.5 hours, and average hospital stay was 1.8 days. Based on MacNab criteria, excellent, good, and fair outcomes were achieved in 25 patients (83%), 3 patients (10%), and 2 patients (6.7%). Complications were observed in 5 patients (16.7%). This is a safe and feasible technique with excellent results obtained at low cost and is becoming an attractive surgical option in developing countries.

Application of an interspinous process device after minimally invasive lumbar decompression could lead to stress redistribution at the pars interarticularis: a finite element analysis

BackgroundAn interspinous process device, the Device for Intervertebral Assisted Motion (DIAM™) designed to treat lumbar neurogenic disease secondary to the lumbar spinal stenosis, it provides dynamic stabilization after minimally invasive (MI) lumbar decompression. The current study was conducted using an experimentally validated L1-L5 spinal finite element model (FEM) to evaluate the limited decompression on range of motion (ROM) and stress distribution on a neural arch implanted with the DIAM.MethodsThe study simulated bilateral laminotomies with partial discectomy at L3-L4, as well as unilateral and bilateral laminotomies with partial discectomy combined with implementation of the DIAM at L3-L4. The ROM and maximum von Mises stresses in flexion, extension, lateral bending, and axial torsion were analyzed in response to the hybrid protocol in comparison with the intact model.ResultsThe investigation revealed that decreased ROM, intradiscal stress, and facet joint force at the implant level, but considerably increased stress at the pars interarticularis were found during flexion and torsion at the L4, as well as during extension, lateral bending, and torsion at the L3, when the DIAM was implanted compared with the defect model.ConclusionThe results demonstrate that the DIAM may be beneficial in reducing the symptoms of stress-induced low back pain. Nevertheless, the results also suggest that a surgeon should be cognizant of the stress redistribution at the pars interarticularis results from MI decompression plus the application of the interspinous process device.

Biomechanical Analysis of Different Lumbar Interspinous Process Devices: A Finite Element Study

Recently, interspinous stabilization with the interspinous process device (IPD) has become an alternative to treat lumbar spinal stenosis. The biomechanical influence of different design features of IPDs on intradiscal pressure (IDP) and facet joint force (FJF) has not been fully understood. The aim of this study was to investigate the biomechanical performance of different IPDs using finite element (FE) method. A FE model of the L1-5 segments was developed and validated. Four surgical FE models were constructed by inserting different implants at the L3-4 segment (Coflex-F, DIAM, Wallis, and pedicle screw system). The 4 motion modes were simulated. The IPDs decreased range of motion (ROM) at the surgical level substantially in flexion and extension, but little influence was found in lateral bending and torsion. Compared with the DIAM and Wallis devices, the Coflex-F device showed advantages in stabilizing the surgical level, especially in flexion and extension, while it increased FJF at adjacent levels by 26%-27% in extension. Among the 3 IPDs, the DIAM device exhibited the most comparable ROM, IDP, and FJF at adjacent levels compared with the intact lumbar spine. The influence of the Wallis device was between that of the Coflex-F and DIAM devices. Compared with rigid fixation, the IPDs demonstrated less compensation at adjacent levels in terms of ROM, IDP, and FJF, which may lower the incidence of adjacent segment degeneration in the long term.

Interspinous process devices for treatment of degenerative lumbar spine stenosis: A systematic review and meta-analysis.

BackgroundDegenerative lumbar spinal stenosis is a condition related to aging in which structural changes cause narrowing of the central canal and intervertebral foramen. It is currently the leading cause for spinal surgery in patients over 65 years. Interspinous process devices (IPDs) were introduced as a less invasive surgical alternative, but questions regarding safety, efficacy, and cost-effectiveness are still unanswered.ObjectivesThe aim of this study was to provide complete and reliable information regarding benefits and harms of IPDs when compared to conservative treatment or decompression surgery and suggest directions for forthcoming RCTs.MethodsWe searched MEDLINE, EMBASE, Cochrane Library, Scopus, and LILACS for randomized and quasi-randomized trials, without language or period restrictions, comparing IPDs to conservative treatment or decompressive surgery in adults with symptomatic degenerative lumbar spine stenosis. Data extraction and analysis were conducted following the Cochrane Handbook. Primary outcomes were pain assessment, functional impairment, Zurich Claudication Questionnaire, and reoperation rates. Secondary outcomes were quality of life, complications, and cost-effectiveness. This systematic review was registered at Prospero (International prospective register of systematic reviews) under number 42015023604.ResultsThe search strategy resulted in 17 potentially eligible reports. At the end, nine reports were included and eight were excluded. Overall quality of evidence was low. One trial compared IPDs to conservative treatment: IPDs presented better pain, functional status, quality of life outcomes, and higher complication risk. Five trials compared IPDs to decompressive surgery: pain, functional status, and quality of life had similar outcomes. IPD implant presented a significantly higher risk of reoperation. We found low-quality evidence that IPDs resulted in similar outcomes when compared to standard decompression surgery. Primary and secondary outcomes were not measured in all studies and were often published in incomplete form. Subgroup analysis was not feasible. Difficulty in contacting authors may have prevented us of including data in quantitative analysis.ConclusionsPatients submitted to IPD implants had significantly higher rates of reoperation, with lower cost-effectiveness. Future trials should improve in design quality and data reporting, with longer follow-up periods.