Development of an experimental model of burst fracture with damage characterization of the vertebral bodies under dynamic conditions.

BACKGROUND: Burst fractures represent a significant proportion of fractures of the thoracolumbar junction. The recent advent of minimally invasive techniques has revolutionized the surgical treatment of this type of fracture. However mechanical behaviour and primary stability offered by these solutions have to be proved from experimental validation tests on cadaveric specimens. Therefore, the aim of this study was to develop an original and reproducible model of burst fracture under dynamic impact. METHODS: Experimental tests were performed on 24 cadaveric spine segments (T11-L3). A system of dynamic loading was developed using a modified Charpy pendulum. The mechanical response of the segments (strain measurement on vertebrae and discs) was obtained during the impact by using an optical method with a high-speed camera. The production of burst fracture was validated by an analysis of the segments by X-ray tomography. FINDINGS: Burst fracture was systematically produced on L1 for each specimen. Strain analysis during impact highlighted the large deformation of L1 due to the fracture and small strains in adjacent vertebrae. The mean reduction of the vertebral body of L1 assessed for all the specimens was around 15%. No damage was observed in adjacent discs or vertebrae. INTERPRETATION: With this new, reliable and replicable procedure for production and biomechanical analysis of burst fractures, comparison of different types of stabilization systems can be envisaged. The loading system was designed so as to be able to produce loads leading to other types of fractures and to provide data to validate finite element modelling.

A novel approach for biomechanical spine analysis: Mechanical response of vertebral bone augmentation by kyphoplasty to stabilise thoracolumbar burst fractures.

Kyphoplasty has been shown as a well-established technique for spinal injuries. This technique allows a vertebral bone augmentation with a reduction of morbidity and does not involve any adjacent segment immobilisation. There is a lack of biomechanical information resulting in major gaps of knowledge such as: the evaluation of the "quality" of stabilisation provided by kyphoplasty as a standalone procedure in case of unstable fracture. Our objective is to analyse biomechanical response of spine segments stabilised by Kyphoplasty and PMMA cement after experiencing burst fractures. Six fresh-frozen cadaveric spine specimens constituted by five vertebra (T11-L3) and four disks were tested. A specific loading setup has been developed to impose pure moments corresponding to loadings of flexion-extension, lateral bending and axial rotation. Tests were performed on each specimen in an intact state and post kyphoplasty following a burst fracture. Strain measurements and motion variations of spinal unit are measured by a 3D optical method. Strain measurements on vertebral bodies after kyphoplasty shows a great primary stabilisation. Comparisons of mobility and angles variations between the intact and post kyphoplasty states do not highlight significant difference. Percutaneous kyphoplasty offers a good primary stability in case of burst fracture. Kinematics analysis during physiological movements shows that this stabilisation solution preserve disk mobility in each adjacent spinal unit.

Multicolumn spinal cord stimulation for significant low back pain in failed back surgery syndrome: design of a national, multicentre, randomized, controlled health economics trial (ESTIMET Study).

BACKGROUND: Many studies have demonstrated the efficacy of spinal cord stimulation (SCS) for chronic neuropathic radicular pain over recent decades, but despite global favourable outcomes in failed back surgery syndrome (FBSS) with leg pain, the back pain component remains poorly controlled by neurostimulation. Technological and scientific progress has led to the development of new SCS leads, comprising a multicolumn design and a greater number of contacts. The efficacy of multicolumn SCS lead configurations for the treatment of the back pain component of FBSS has recently been suggested by pilot studies. However, a randomized controlled trial must be conducted to confirm the efficacy of new generation multicolumn SCS. Évaluation médico-économique de la STImulation MEdullaire mulTi-colonnes (ESTIMET) is a multicentre, randomized study designed to compare the clinical efficacy and health economics aspects of mono- vs. multicolumn SCS lead programming in FBSS patients with radicular pain and significant back pain. MATERIALS AND METHODS: FBSS patients with a radicular pain VAS score≥50mm, associated with a significant back pain component were recruited in 14 centres in France and implanted with multicolumn SCS. Before the lead implantation procedure, they were 1:1 randomized to monocolumn SCS (group 1) or multicolumn SCS (group 2). Programming was performed using only one column for group 1 and full use of the 3 columns for group 2. Outcome assessment was performed at baseline (pre-implantation), and 1, 3, 6 and 12months post-implantation. The primary outcome measure was a reduction of the severity of low back pain (bVAS reduction≥50%) at the 6-month visit. Additional outcome measures were changes in global pain, leg pain, paraesthesia coverage mapping, functional capacities, quality of life, neuropsychological aspects, patient satisfaction and healthcare resource consumption. TRIAL STATUS: Trial recruitment started in May 2012. As of September 2013, all 14 study centres have been initiated and 112/115 patients have been enrolled. Preliminary results are expected to be published in 2015. TRIAL REGISTRATION: Clinical trial registration information-URL: www.clinicaltrials.gov. Unique identifier NCT01628237.

The Franco-Canadian multicolumn spinal cord stimulation prospective study: a subgroup analysis focusing on the decisive role of lead positioning.

INTRODUCTION: Multicolumn spinal cord stimulation (SCS) is now considered to be effective for the treatment of the radicular and back component in refractory Failed Back Surgery Syndrome (FBSS) patients. The relationship between the paresthesia coverage of the back and clinical outcomes has recently been confirmed by an international prospective study. However, significant disparities in outcomes were identified and could result from the heterogeneity of lead implantation parameters which are dependant on local practices and experience. We therefore sought to analyse the impact of lead implantation level and its lateralization on the ability to address back pain with multicolumn SCS leads. STUDY OBJECTIVES, MATERIALS AND METHODS: The present study was a retrospective subgroup analysis from an observational, prospective non-randomized trial that included 76 patients with refractory FBSS, implanted with multicolumn SCS between 2008 to 2011 in three neurosurgical pain centres (Poitiers, France, Montreal, Canada and Regina, Canada). A subgroup of 21 patients with "optimized lead positioning" (OLP) was identified, distinguished from the rest of the main study population (NON OLP subgroup; n=51) and submitted to specific data analysis. Baseline characteristics of both groups were strictly comparable. Our primary objective was to analyse the impact of lead positioning (vertebral level and lateralization) on the back paresthesia coverage. The secondary objectives were to compare the analgesic and functional efficacy of multicolumn stimulation in these OLP and NON OLP subgroups and to determine if a paresthesia coverage improvement leads to better clinical outcomes in these difficult-to-treat patients. RESULTS: In this subgroup analysis, unilateral coverage of the low back area was achieved in 85.0% of OLP patients vs. 76.5% in the NON OLP group. Bilateral and complete coverage of the low back area was achieved in 60% of OLP patients vs. 51% in the NON OLP group but these differences were not statistically significant. At 6months, 81.0% of OLP patients vs. 69.4% in the NON OLP group presented at least 30% improvement of the low back VAS, while 52.4% of them achieved at least 50% improvement of the low back VAS vs. 38.8% in the NON OLP group. Functional improvement at 6months, available and calculated only in the French group of OLP patients (n=14) by the Oswestry Disability Index, was significant, decreasing from 60.67% to 33.43%. CONCLUSION: Despite limitations in this retrospective subgroup analysis, this study suggests that the vertebral level (T8-T9) and midline positioning of the lead during implantation could be decisive factors to optimize paresthesia coverage and finally, clinical and functional outcomes. While sophistication has been responsible for an increase of the size and the programming possibilities of surgical SCS leads during the past years, multicolumn SCS lead implantation should in fact be considered as a "functional neurosurgical" procedure and could benefit from intraoperative patient cooperation, as in the case for deep brain stimulation procedures, due to minimally invasive implantation techniques.

A prospective study evaluating sleep quality in Failed Back Surgery Syndrome patients treated by multicolumn spinal cord stimulation: study design protocol and presentation of the study population.

BACKGROUND AND PURPOSE: One of the main consequences of chronic pain syndrome is major impairment of the quality of sleep. Chronic pain and insomnia are independently linked to significant reductions in quality of life and psychiatric morbidity. Recent studies have suggested the efficacy of spinal cord stimulation (SCS) for the treatment of the back pain component in failed back surgery syndrome (FBSS) patients using a multicolumn lead. The main aim of this pilot study is to assess the influence and potential benefits of SCS on sleep quality in refractory FBSS patients implanted with multicolumn SCS and enrolled in the French multicentre ESTIMET study. METHODS: This is a single-centre, comparative, exploratory, pilot study. Sixteen FBSS patients enrolled in the ESTIMET study and implanted with multicolumn SCS will be monitored for 6months after implantation. Sleep parameters will be recorded by polysomnography, Psychomotor Vigilance Test and Osler tests, actigraphy, sleepiness scales, and sleep quality testing. Sleep will be evaluated before (at the inclusion visit) and after SCS implantation (at the 6-month visit). Secondary objectives will also assess the impact of SCS lead programming (mono vs. multicolumn SCS) and the influence of position-adaptive stimulation at night on sleep quality. TRIAL STATUS: The first patient of this ancillary study was enrolled on 21 May, 2012 and recruitment has now been achieved. Primary endpoint findings are expected to be available in 2015. CONCLUSION: By providing an analysis of the quality of sleep in chronic pain patients who are candidates for implanted neurostimulation, this new approach focuses on an important aspect of quality of life often overlooked in these poly-medication patients. It could show a real clinical benefit and underestimation of these analgesic innovative expensive techniques, where medico-economic analysis, would or would not promote access.

"MAST" prospective study: value of minimal access spine technologies technique for multicolumn spinal cord stimulation surgical lead implantation in the context of a French multicentre randomized controlled trial (ESTIMET study).

BACKGROUND AND PURPOSE: Spinal cord stimulation (SCS) has been demonstrated to be an effective treatment for postoperative persistent leg pain after spine surgery, but treatment of the back pain component remains much more difficult, as it comprises mixed neuropathic and mechanical pain mechanisms. Moreover, these patients could present damaged tissues at the site of SCS lead implantation as a result of previous spine surgery. It can therefore be logically assumed that minimizing the surgical invasiveness of SCS implantation would be beneficial for these patients. Several studies have demonstrated the value of Minimal Access Spine Technologies (MAST) in spine surgery, but only a few case reports have been published concerning the use of MAST techniques for SCS. Therefore, we were prompted to conduct a second ESTIMET ancillary study to prospectively analyse the potential impact and benefits of MAST technique during SCS lead implantation versus an open surgical approach. METHODS: This is a multicentre, comparative, ancillary study conducted in 61 patients among the 115 enrolled patients ESTIMET study. One arm comprises patients undergoing multicolumn lead implantation via a Conventional Open Approach (COA) and the other arm comprises patients implanted by a MAST approach. Patients will be followed for 12 months after lead implantation. The following data will be collected: elevation of muscle enzymes (serum CPK), scar size, blood loss, infection rate, operating time and global, leg, back and scar NPRS. TRIAL STATUS: The first patient of this ancillary study was enrolled on 21 May 2012 and recruitment has now been achieved. Primary endpoint findings are expected to be available in 2015. CONCLUSION: Minimally invasive techniques have now been used for spine surgery for the past 12 years, and could also be useful in the context of SCS lead implantation, especially in patients with chronic back pain prior to implantation.

A novel, objective, quantitative method of evaluation of the back pain component using comparative computerized multi-parametric tactile mapping before/after spinal cord stimulation and database analysis: the "Neuro-Pain't" software.

INTRODUCTION: One of the major challenges of neurostimulation is actually to address the back pain component in patients suffering from refractory chronic back and leg pain. Facing a tremendous expansion of neurostimulation techniques and available devices, implanters and patients can still remain confused as they need to select the right tool for the right indication. To be able to evaluate and compare objectively patient outcomes, depending on therapeutical strategies, it appears essential to develop a rational and quantitative approach to pain assessment for those who undergo neurostimulation implantation. OBJECTIVES, MATERIAL AND METHODS: We developed a touch screen interface, in Poitiers University Hospital and N(3)Lab, called the "Neuro-Pain'T", to detect, record and quantify the painful area surface and intensity changes in an implanted patient within time. The second aim of this software is to analyse the link between a paraesthesia coverage generated by a type of neurostimulation and a potential analgesic effect, measured by pain surface reduction, pain intensity reduction within the painful surface and local change in pain characteristics distribution. The third aim of Neuro-Pain'T is to correlate these clinical parameters to global patient data and functional outcome analysis, via a network database (Neuro-Database), to be able to provide a concise but objective approach of the neurostimulation efficacy, summarized by an index called "RFG Index". RESULTS AND DISCUSSION: This software has been used in more than 190 patients since 2012, leading us to define three clinical parameters grouped as a clinical component of the RFG Index, which might be helpful to assess neurostimulation efficacy and compare implanted devices. CONCLUSION: The Neuro-Pain'T is an original software designed to objectively and quantitatively characterize reduction of a painful area in a given individual, in terms of intensity, surface and pain typology, in response to a treatment strategy or implantation of an analgesic device. Because pain is a physical sensation, which integrates a psychological dimension, its assessment justifies the use of multidimensional and global evaluation scales. However, in the context of neurostimulation and comparative clinical trials designed to test the technical efficacy of a given device, a simple, objective and quantitative evaluation tool could help to guide tomorrow's treatment options by transforming personal convictions into a more robust scientific rationale based on data collection and data mining techniques.