Interspinous Device Research Articles

Why Do Interspinous Motion Preservation Devices (ISDs) Show Unfocused Results? Clinical Anatomy of Lumbar Lamina and Spinous Process

IntroductionInterspinous motion preservation technique for various spondylotic conditions has been supposed to be useful as a time-sparing technique before rigid instrumentation with a potential se...

Device-Related Complications of the Coflex Interspinous Process Implant for the Lumbar Spine

Introduction Coflex, a type of interspinous process implant, can provide intervertebral dynamic stability for surgical segments and relieve lumbocrural pain effectively. However, few studies have described the avoidance and therapeutic strategies of Coflex implant complications. Materials and Methods Coflex implant complications included intraoperative or postoperative spinous process fracture, aggravated postoperative lumbocrural pain, dislodgment, and malposition in this study. The complications were analyzed, and therapeutic strategies were applied according to the specific complication. The Visual Analogue Scale and Oswestry Disability Index scores were evaluated by using the paired-samples test of SPSS 12.0 Results Conservative treatment was provided to seven patients who experienced aggravated lumbocrural pain even though their devices remained in the correct position, and pedicle screw treatment was used as an alternative in four cases. The Visual Analogue Scale and Oswestry Disability Index scores showed evident improvement in these patients. The Visual Analogue Scale and Oswestry Disability Index scores of two patients who underwent revision also improved. Conclusion Coflex implants should be avoided in patients with osteoporosis, a narrow interspinous space and intervertebral coronal spondylolysis, or sagittal instability; furthermore, the device choice, depth of implantation, and clamping intensity should be appropriate. Conservative treatment can be provided to patients with symptoms if the device remains in the correct position; however, revisions and salvages should be undertaken with internal fixation of pedicle screws for patients with device malposition, intraoperative implantation failure, or device intolerance. Disclosure of Interest None declared References Richards JC, Majumdar S, Lindsey DP, Beaupré GS, Yerby SA. The treatment mechanism of an interspinous process implant for lumbar neurogenic intermittent claudication. Spine 2005;30(7):744–749 Siddiqui M, Nicol M, Karadimas E, Smith F, Wardlaw D. The positional magnetic resonance imaging changes in the lumbar spine following insertion of a novel interspinous process distraction device. Spine 2005;30(23):2677–2682 Lee J, Hida K, Seki T, Iwasaki Y, Minoru A. An interspinous process distractor (X STOP) for lumbar spinal stenosis in elderly patients: preliminary experiences in 10 consecutive cases. J Spinal Disord Tech 2004;17(1):72-77, discussion 78 Kong DS, Kim ES, Eoh W. One-year outcome evaluation after interspinous implantation for degenerative spinal stenosis with segmental instability. J Korean Med Sci 2007;22(2):330–335 Errico TJ, Kamerlink JR, Quimo M, et al. Survivorship of coflex interlaminar-interspinous implant. SAS J 2009;3(2):59–67 Park SC, Yoon SH, Hong YP, Kim KJ, Chung SK, Kim HJ. Minimum 2-year follow-up result of degenerative spinal stenosis treated with interspinous u (coflex). J Korean Neurosurg Soc 2009;46(4):292–299 Bono CM, Vaccaro AR. Interspinous process devices in the lumbar spine. J Spinal Disord Tech 2007;20(3):255–261 Trautwein FT, Lowery GL, Wharton ND, Hipp JA, Chomiak RJ. Determination of the in vivo posterior loading environment of the Coflex interlaminar-interspinous implant. Spine J 2010;10(3):244–251 Tsai KJ, Murakami H, Lowery GL, Hutton WC. A biomechanical evaluation of an interspinous device (Coflex) used to stabilize the lumbar spine. J Surg Orthop Adv 2006;15(3):167–172 Christie SD, Song JK, Fessler RG. Dynamic interspinous process technology. Spine 2005; 30 (16, Suppl)S73-S78 Lindsey DP, Swanson KE, Fuchs P, Hsu KY, Zucherman JF, Yerby SA. The effects of an interspinous implant on the kinematics of the instrumented and adjacent levels in the lumbar spine. Spine 2003;28(19):2192–2197 Swanson KE, Lindsey DP, Hsu KY, Zucherman JF, Yerby SA. The effects of an interspinous implant on intervertebral disc pressures. Spine 2003;28(1):26–32 Bowers C, Amini A, Dailey AT, Schmidt MH. Dynamic interspinous process stabilization: review of complications associated with the X-Stop device. Neurosurg Focus 2010;28(6):E8 Chao S, Malloy JP, Bono CM. Complications specific to motion-sparing devices in the lumbar spine. Semin Spine Surg 2011;23(2):123–134 Kim DH, Tantorski M, Shaw J, et al. Occult spinous process fractures associated with interspinous process spacers. Spine 2011;36(16):E1080-E1085 Barbagallo GM, Olindo G, Corbino L, Albanese V. Analysis of complications in patients treated with the X-Stop Interspinous Process Decompression System: proposal for a novel anatomic scoring system for patient selection and review of the literature. Neurosurgery 2009;65(1):111-119, discussion 119–120 Barbagallo GM, Corbino LA, Olindo G, Foti P, Albanese V, Signorelli F. The “sandwich phenomenon”: a rare complication in adjacent, double-level X-stop surgery: report of three cases and review of the literature. Spine 2010;35(3):E96-E100 Anderson PA, Tribus CB, Kitchel SH. Treatment of neurogenic claudication by interspinous decompression: application of the X STOP device in patients with lumbar degenerative spondylolisthesis. J Neurosurg Spine 2006;4(6):463–471 Zucherman JF, Hsu KY, Hartjen CA, et al. A multicenter, prospective, randomized trial evaluating the X STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication: two-year follow-up results. Spine 2005;30(12):1351–1358 Siddiqui M, Smith FW, Wardlaw D. One-year results of X Stop interspinous implant for the treatment of lumbar spinal stenosis. Spine 2007;32(12):1345–1348

DIAM Implantation for Degenerative Disc Disease

Introduction Lumbar disc degeneration (LDD) is among the most common causes of low back pain. Typical symptoms include axial low back pain, buttock pain, with or without radiation to posterior thighs or legs, and intolerance to upright positions. Several surgical treatment options are available, including intradiscal injections, intradiscal electrothermal therapy, discectomy, total disc arthroplasty, and fusion. Recently, implantation of interspinous process devices has been shown to decrease low back pain, and provide morphological alterations of the degenerative discs, resulting in satisfactory clinical outcomes. This study was conducted to review our results of using stand-alone DIAM implantation as the treatment for symptomatic LDD. Materials and Methods A total of 24 selected cases of LDD were treated surgically with stand-alone DIAM implantation. In 20 patients, the presenting symptoms were predominantly axial low back/buttock pain with little leg pain, while in 4 patients there was only axial pain. Motor weakness and sensory disturbance involving the corresponding nerve roots were present in eight cases. Three patients had undergone previous lumbar discectomy of the afflicted discs. Typical MRI findings included loss of height, signal changes, and/or annular tear of the discs. On the basis of Pfirrmann grading scale for disc degeneration, three cases were categorized as Grade II, and 21 cases as Grade III. Our exclusion criteria included intermittent claudication due to lumbar spinal stenosis, severe disc space collapse with Modic changes, greater than Grade II spondylolisthesis, facet ankylosis, and L5-S1 pathology. Provocative test with intradiscal injection of normal saline-induced concordant pain in all cases. Results All patients reported significant symptom relief after surgery, as reflected by VAS and ODI improvements. The final outcomes were excellent in 19, good in 2, fair in 2, and poor in 1 cases. Segmental flexion/extension mobility was maintained in 20, and restricted or lost in 2, of 22 cases with preoperative mobility. In the other two cases with no preoperative mobility, DIAM implantation did not change the status. MRI was repeated in the two cases showing fair, and the one case showing poor outcomes. In all of them, enlargement of neuroforamens at the implanted levels were found. In one fair case, disappearance of annular tear was observed. In the other fair case (L4-5 implantation), L5-S1 disc herniation was disclosed, and removed in a second operation. The case with poor outcome was diagnosed with depression, having concomitant multiple joint pain, dysmenorrhea, sleep disorder, despite normal findings on different exams ordered by different specialists. Conclusion In highly selected cases with symptomatic LDD, stand-alone interspinous DIAM implantation is effective for alleviation of symptoms, and stabilization of disc status. Disclosure of Interest None declared References Sandu N, Schaller B, Arasho B, Orabi M. Wallis interspinous implantation to treat degenerative spinal disease: description of the method and case series. Expert Rev Neurother 2011;11(6):799–807 Buric J, Pulidori M, Sinan T, Mehraj S. DIAM device for low back pain in degenerative disc disease : 24 months follow-up. Acta Neurochir Suppl (Wien) 2011;108:177–182 Pfirrmann CW, Metzdorf A, Zanetti M, Hodler J, Boos N. Magnetic resonance classification of lumbar intervertebral disc degeneration. Spine 2001;26(17):1873–1878

Clinical Results of Interspinous Dynamic Stabilization with STENOFIX Device

Introduction The objective of our study was to evaluate the efficacy of STENOFIX interspinous dynamic stabilization device in different spinal conditions including discectomies and central and foraminal spinal stenoses, with minimum of 1 year of patient follow-up. Materials and Methods We performed a prospective case series on 64 patients over a period of 3 years who underwent spinal surgeries in our institutions with a minimum of 1 year follow-up. Spinal procedures included discectomies, one or two level Stenofix implant insertions for patients with central spinal stenosis and one or two level Stenofix implant insertions for patients with lateral recess foraminal stenosis. Pre- and postoperatively disability and pain scores were measured using the Oswestry Disability Index (ODI), visual analogue scale (VAS), SF 36 scores, and EQ-5D-3L scores in conjunction with radiographic evaluation of disc height and sagittal alignment. Results All follow-up patients demonstrated significant improvement in ODI, VAS, SF 36, and EQ-5D-3L pain scores in comparison to those of preoperation ( p < 0.05). We observed no significant difference in sagittal alignment post-interspinous dynamic stabilization with Stenofix implant. No complications such as implant loosening, immigration, and spinal process fracture were observed. Conclusion The STENOFIX implant demonstrates significant improvement in clinical outcomes when used as the treatment of choice in patients with central and/or lateral recess lumbar spinal stenosis, as well as when used as a supplement to discectomies. Disclosure of Interest None declared

Interspinous Dynamic Stabilization with DIAM (Silicone) or InSWing (PEEK) Interspinous Implants

Introduction Foraminal and spinal canal stenosis causes neurogenic claudication. Interspinous devices provide an indirect decompression by distracting the involved vertebrae, thereby tightening the buckled flavum and opening the foramina and attempting to restore normal loading patterns in the lumbar spine which have altered due to disc degeneration. When used for indirect decompression alone, they avoid scar tissue formation in the canal. The DIAM (Medtronic, United States) is made of silicone and therefore conforms more to the interspinous space. The InSWing (Orthofix, United States) is made of PEEK (polyether ether ketone) and is noncompressible. We report the outcomes between these devices and between direct and indirect decompressions. Materials and Methods Retrospective analysis performed for surgery in July 2009 to 2011. Paired and unpaired t-test used to assess statistical significance ( p < 0.05). Results A total of 60 patients were included (22 females, 38 males), age 46 (21-78) years. Preoperative duration of symptoms was 65 (4-420) months. The numbers in each implant/decompression group and follow-up are shown in Table 1. Statistically significant improvement observed in all outcome measures in direct and InSWing groups and all outcomes except MCS in DIAM group. Indirect group improved in all outcomes, but these were significant only in VAS Back/Leg. InSWing and direct group scores improved more than the DIAM and indirect groups, respectively, but these differences were only significant in Oswestry in the decompression group. All five patients requiring revision surgery were in the DIAM group. Conclusion Statistically significant improvement was seen in all outcome measures in patients undergoing direct decompressions or implantation with InSWing implants. Improvement in scores was greater in these groups compared with the indirect decompression or DIAM groups. Disclosure of Interest A. Berg: None declared J. Tankel: None declared M. Hernandez: None declared C. Jensen: None declared B. Purushothaman: None declared G. Reddy: None declared T. Friesem: Conflict with RTI Surgical, Globus Medical

Lumbar spine stability after combined application of interspinous fastener and modified posterior lumbar interbody fusion: a biomechanical study

Posterior lumbar interbody fusion (PLIF) and internal fixation are commonly performed for the treatment of lower back pain due to lumbar spinal degeneration. We have developed a novel interspinous fixation device, the interspinous fastener (ISF) for potential use in the surgical management of degenerative spinal disease. The aim of this study was to assess the in vitro biomechanical characteristics of calf lumbar spine specimens after ISF fixation with modified PLIF. Ten lumbar spine (L3-L6) specimens from ten fresh calf cadavers (8-10weeks of age) were used. Each specimen underwent sequential testing for each of the following four groups: no instrumentation (INTACT); interspinous fusion device fixation+PLIF (ISF); unilateral pedicle screw and titanium rod fixation+PLIF (UPS); bilateral pedicle screw and titanium rod fixation+PLIF (BPS). Outcome measures included angular range of motion (ROM) during unloaded and loaded (8Nm) flexion, extension, left bending, right bending, left torsion and right torsion. For all unloaded and loaded assessments, ROM was significantly higher in the INTACT group compared with all other groups (P<0.05). Similarly, ROM was significantly higher in the UPS group (indicating decreased stability) compared with the ISF and BPS groups (P<0.05). The only significant difference between the ISF and BPS groups was in the ROM with unloaded extension (higher in the BPS group, P=0.006). We found that ISF fixation with PLIF of the lower lumbar spine provided biomechanical stability that was equivalent to that associated with bilateral pedicle screw/rod fixation with PLIF. The ISF shows potential as an alternative means of fixation in the surgical management of degenerative spinal disease.

Application of the Restoring Force Method for Identification of Lumbar Spine Flexion-Extension Motion Under Flexion-Extension Moment

The restoring force method (RFM), a nonparametric identification technique established in applied mechanics, was used to maximize the information obtained from moment-rotation hysteresis curves under pure moment flexion-extension testing of human lumbar spines. Data from a previous study in which functional spine units were tested intact, following simulated disk injury, and following implantation with an interspinous process spacer device were used. The RFM was used to estimate a surface map to characterize the dependence of the flexion-extension rotation on applied moment and the resulting axial displacement. This described each spine response as a compact, reduced-order model of the complex underlying nonlinear biomechanical characteristics of the tested specimens. The RFM was applied to two datasets, and successfully estimated the flexion-extension rotation, with error ranging from 3 to 23%. First, one specimen, tested in the intact, injured, and implanted conditions, was analyzed to assess the differences between the three specimen conditions. Second, intact specimens (N = 12) were analyzed to determine the specimen variability under equivalent testing conditions. Due to the complexity and nonlinearity of the hysteretic responses, the mathematical fit of each surface was defined in terms of 16 coefficients, or a bicubic fit, to minimize the identified (estimated) surface fit error. The results of the first analysis indicated large differences in the coefficients for each of the three testing conditions. For example, the coefficient corresponding to the linear stiffness (a01) had varied magnitude among the three conditions. In the second analysis of the 12 intact specimens, there was a large variability in the 12 unique sets of coefficients. Four coefficients, including two interaction terms comprised of both axial displacement and moment, were different from zero (p < 0.05), and provided necessary quantitative information to describe the hysteresis in three dimensions. The results suggest that further work in this area has the potential to supplement typical biomechanical parameters, such as range of motion, stiffness, and neutral zone, and provide a useful tool in diagnostic applications for the reliable detection and quantification of abnormal conditions of the spine.

Biomechanics of interspinous devices.

A number of interspinous devices (ISD) have been introduced in the lumbar spine implant market. Unfortunately, the use of these devices often is not associated with real comprehension of their biomechanical role. The aim of this paper is to review the biomechanical studies about interspinous devices available in the literature to allow the reader a better comprehension of the effects of these devices on the treated segment and on the adjacent segments of the spine. For this reason, our analysis will be limited to the interspinous devices that have biomechanical studies published in the literature.

Experience with the second-generation Wallis interspinous dynamic stabilization device implanted in degenerative lumbar disease: a case series of 50 patients.

This study aimed to evaluate the short- to medium-term outcomes of the second-generation Wallis interspinous dynamic stabilization device for treatment of lumbar degenerative disease. Fifty patients with lumbar degenerative disease treated from August 2007 to September 2009 were included in this retrospective study. The Japanese Orthopedic Association (JOA) score and the Oswestry Disability Index (ODI) were used for therapeutic efficacy evaluation. Odom's criteria were used to evaluate postoperative outcome with regard to symptoms. Anteroposterior X-rays were obtained after surgery. All patients were followed up for 2 years. Based on Odom's criteria, 22, 24 and 4 patients had excellent, good, and fair results respectively. The JOA score at 3, 12, and 24 months after surgery was significantly higher than before surgery (all p < 0.001), and the ODI score at 3, 12, and 24 months after surgery was significantly lower than before surgery (all p < 0.001). The posterior intervertebral disc height and the neural foramina height at 12 and 24 months after surgery was significantly higher than before surgery (both p < 0.001). Implantation of the second-generation Wallis interspinous dynamic stabilization device produced satisfactory clinical outcome at short- and medium-term follow-up in patients with lumbar degenerative disease.

Controversies about Interspinous Process Devices in the Treatment of Degenerative Lumbar Spine Diseases: Past, Present, and Future

A large number of interspinous process devices (IPD) have been recently introduced to the lumbar spine market as an alternative to conventional decompressive surgery in managing symptomatic lumbar spinal pathology, especially in the older population. Despite the fact that they are composed of a wide range of different materials including titanium, polyetheretherketone, and elastomeric compounds, the aim of these devices is to unload spine, restoring foraminal height, and stabilize the spine by distracting the spinous processes. Although the initial reports represented the IPD as a safe, effective, and minimally invasive surgical alternative for relief of neurological symptoms in patients with low back degenerative diseases, recent studies have demonstrated less impressive clinical results and higher rate of failure than initially reported. The purpose of this paper is to provide a comprehensive overview on interspinous implants, their mechanisms of action, safety, cost, and effectiveness in the treatment of lumbar stenosis and degenerative disc diseases.

Percutaneous interspinous distraction device for the treatment of lumbar spinal canal stenosis: clinical and radiographic results at 2-year follow-up.

ObjectiveTo evaluate the effectiveness of the In- space (Synthes, Umkirch, Germany) and the correlation between radiographic parameters and clinical outcome in patients with lumbar spinal canal stenosis (LSS).MethodsBetween June 2009 and May 2013, 56 patients with LSS underwent In-space by one senior surgeon. All of the patients were evaluated both clinically and radiographic measurements before the procedure and each visit at the postoperative follow-up. Preoperative and postoperative X-ray imaging was performed before the procedure and at follow-up to assess the correlation with the clinical outcome. Radiological measurements and clinical outcomes were recorded to establish a relationship between the radiographic parameters and clinical outcome of this procedure. All patients had at least 2 years of follow-up.ResultsThe mean VAS score of back pain decreased significantly (p < 0.05).ConclusionsOur data suggest that percutaneous interspinous devices are a good alternative to treat LSS. The device offers significant decrease in back pain, leg pain and ODI score with 2-year lasting relief from symptoms. The increased intervertebral foramenal space explains the improvement of leg pain, but the mechanism of back pain relief remains unclear. A very weak correlation between the radiographic changes and improvement of pain was found.

Interspinous posterior devices: What is the real surgical indication?

Interspinous posterior device (IPD) is a term used to identify a relatively recent group of implants used to treat lumbar spinal degenerative disease. This kind of device is classified as part of the group of the dynamic stabilization systems of the spine. The concept of dynamic stabilization has been replaced by that of dynamic neutralization of hypermobility, with the intention of clarifying that the primary aim of this kind of system is not the preservation of the movement, but the dynamic neutralization of the segmental hypermobility which is at the root of the pathological condition. The indications for the implantation of an IPD are spinal stenosis and neurogenic claudication, assuming that its function is the enlargement of the neural foramen and the decompression of the roots forming the cauda equina in the central part of the vertebral canal. In the last 10 years, use of these implants has been very common but to date, no long-term clinical follow-up regarding clinical and radiological aspects are available. The high rate of reoperation, recurrence of symptoms and progression of degenerative changes is evident in the literature. If these devices are effectively a miracle cure for lumbar spinal stenosis, why do the utilization and implantation of IPD remain extremely controversial and should they be investigated further? Excluding the problems related to the high cost of the device, the main problem remains the pathological substrate on which the device is explicit in its action: the degenerative pathology of the spine.

Role of coflex as an adjunct to decompression for symptomatic lumbar spinal stenosis.

Study DesignProspective cohort study.PurposeTo assess whether additional implantation of Coflex following spinal decompression provided better clinical outcomes compared to decompression alone for symptomatic lumbar spinal stenosis (LSS) and to determine whether improvement in clinical outcomes correlated with changes in the radiological indices studied.Overview of LiteratureLiterature on benefits of additional Coflex implantation compared to decompression alone for symptomatic LSS is limited.MethodsPatients with symptomatic LSS who met the study criteria were offered spinal decompression with Coflex implantation. Those patients who accepted Coflex implantation were placed in the Coflex group (n=22); while those opting for decompression alone, were placed in the comparison group (n=24). Clinical outcomes were assessed preoperatively, six-months, one-year and two-years postoperatively, using the Oswestry disability index, 100 mm visual analogue scale (VAS)-back pain and VAS-leg pain, and short form-36 (SF-36). Radiological indices (disc height, foraminal height and sagittal angle) were assessed preoperatively, six months, one year, and two years postoperatively.ResultsBoth groups showed statistically significant (p<0.001) improvement in all the clinical outcome indicators at all points in time as compared to the preoperative status. However, improvement in the Coflex group was significantly greater (p<0.001) than the comparison group. Changes in the radiological indices did not correlate significantly with the improvement in clinical outcome indicators.ConclusionsAdditional Coflex implantation after spinal decompression in symptomatic LSS offers better clinical outcomes than decompression alone in the short-term. Changes in radiological indices do not correlate with the improvements in clinical outcomes after surgery for symptomatic LSS.

Interspinous Posterior Devices IPD: A Miracle Cure for the Lumbar Spinal Stenosis?

Interspinous Posterior Device (IPD) is a term used to identify a relatively recent group of implants used to treat lumbar spine stenosis with the presumed aim of a dynamic motion control systems. In the last 10 years there was a very large use of these implants. Despite this, no long-term clinical follow-up are available. In the literature is evident the high rate of reoperation, recurrence of symptoms and progression of degenerative changes. But his main question is: if these devices are effectively a miracle cure for the common problem of the lumbar spinal stenosis, why actually the use of IPD remains extremely controversial and should be investigated further?

One-year follow-up of a series of 100 patients treated for lumbar spinal canal stenosis by means of HeliFix interspinous process decompression device.

Purpose. New interspinous process decompression devices (IPDs) provide an alternative to conservative treatment and decompressive surgery for patients with neurogenic intermittent claudication (NIC) due to degenerative lumbar spinal stenosis (DLSS). HeliFix is a minimally invasive IPD that can be implanted percutaneously. This is a preliminary evaluation of safety and effectiveness of this IPD up to 12 months after implantation. Methods. After percutaneous implantation in 100 patients with NIC due to DLSS, data on symptoms, quality of life, pain, and use of pain medication were obtained for up to 12 months. Results. Early symptoms and physical function improvements were maintained for up to 12 months. Leg, buttock/groin, and back pain were eased throughout, and the use and strength of related pain medication were reduced. Devices were removed from 2% of patients due to lack of effectiveness. Conclusions. Overall, in a period of up to 12-month follow-up, the safety and effectiveness of the HeliFix offered a minimally invasive option for the relief of NIC complaints in a high proportion of patients. Further studies are undertaken in order to provide insight on outcomes and effectiveness compared to other decompression methods and to develop guidance on optimal patient selection.

Clinical application of an interspinous device (CoflexTM) for for lumbar disc herniation

Objective To compare the long-term clinical effects between lumber discectomy (LD) and the Coflex interspinal dynamic fixation system in the treatment of lumbar disc herniation.Methods From January 2009 to May 2013,80 cases of lumbar disc herniation were enrolled in our study,including 37 cases subject to lumber discectomy,and 43 cases subject to Coflex system.All patients received visual analogue scale (VAS),lumbar Japanese Orthopaedic Association (JOA) score and the Owestry disability index (ODI) assessment before and 12,24,36 and 48 months after operation.Surgically resected segmental dorsal disc height,the ventral disc height and spinal canal area were also measured through X-ray film and CT.Results The scores of JOA and VAS were significantly higher in Coflex group than in LD group 48 months after surgery (P ＜ 0.05).Coflex system treatment also showed advances in ODI assessment during the follow-up period of 12 months (P ＜ 0.05).There was significant difference in the surgically resected segmental dorsal disc height,the ventral disc height and spinal canal area between preoperation and the last follow-up,and there was also significant difference in the above parameters between the two groups at the last follow-up (P ＜ 0.05).Conclusion Forty-eight-month follow-up showed that patients subject to Coflex system had advantages in long-term clinical efficacy over LD. Key words: Lumbar disc herniation; Coflex; Lumbar discectomy

Surgical Role of Interspinous Distraction Devices (Coflex, DIAM) for the Treatment of Neurologic Pain and Intermittent Claudication Due to Lumbar Spinal Stenosis

Neurogenic intermittent claudication and degenerative low back pain caused by lumbar spinal stenosis (LSS) often occur after the age of 50 years and represent one of the most common degenerative spinal diseases of the elderly. We reviewed medical records and radiographs for patients with LSS who received an interspinous process device (IPD) between October 2009 and December 2010. The aim of the study was to evaluate surgical outcomes for decompressive surgery involving IPD implantation. We reviewed data for 62 patients who were treated with decompressive surgery and IPD (Coflex or DIAM). Neurogenic signs after surgery are important indicators. The patients were examined the day before, 2 weeks after, and 3 months after surgery. Pain was measured according to a visual analog scale (VAS) and neurologic changes were recorded. Postoperative assessments at 2 weeks and 3 months after surgery included pain and neurologic scores and a patient satisfaction survey. For some groups we observed a significant improvement ( p < 0.05) in back pain according to the VAS. Symptom relief on forward flexion is a key indicator for prognosis. Interspinous implants offer significant, long-lasting symptom control and IPDs are safe and effective devices for LSS.

Biomechanical analysis of an interspinous fusion device as a stand-alone and as supplemental fixation to posterior expandable interbody cages in the lumbar spine

In this paper the authors evaluate through in vitro biomechanical testing the performance of an interspinous fusion device as a stand-alone device, after lumbar decompression surgery, and as supplemental fixation to expandable cages in a posterior lumbar interbody fusion (PLIF) construct. Nine L3-4 human cadaveric spines were biomechanically tested under the following conditions: 1) intact/control; 2) L3-4 left hemilaminotomy with partial discectomy (injury); 3) interspinous spacer (ISS); 4) bilateral pedicle screw system (BPSS); 5) bilateral hemilaminectomy, discectomy, and expandable posterior interbody cages with ISS (PLIF-ISS); and 6) PLIF-BPSS. Each test consisted of 100 N of axial preload with ± 7.5 Nm of torque in flexion-extension, right/left lateral bending, and right/left axial rotation. Significant changes in range of motion (ROM), neutral zone stiffness (NZS), elastic zone stiffness (EZS), and energy loss (EL) were explored among conditions using nonparametric Friedman test and Wilcoxon signed-rank comparisons (p ≤ 0.05). The injury increased ROM in flexion (p = 0.01), left bending (p = 0.03), and right/left rotation (p < 0.01) and also decreased NZS in flexion (p = 0.01) and extension (p < 0.01). Both the ISS and BPSS reduced flexion-extension ROM and increased flexion-extension stiffness (NZS and EZS) with respect to the injury and intact conditions (p < 0.05), but the ISS condition provided greater resistance than BPSS in extension for ROM, NZS, and EZS (p < 0.01). The BPSS increased the rigidity (ROM, NZS, and EZS) of the intact model in lateral bending and axial rotation (p ≤ 0.01), except in EZS for left rotation (p = 0.23, Friedman test). The incorporation of posterior cages marginally increased (p = 0.05) the EZS of the BPSS construct in flexion but these interbody devices provided significant stability to the ISS construct in lateral bending and axial rotation for ROM (p = 0.02), in lateral bending for NZS (p = 0.02), and in flexion/axial rotation for EZS (p ≤ 0.03); however, both PLIF constructs demonstrated equivalent ROM and stiffness (p ≥ 0.16), except in lateral bending where the PLIF-BPSS was more stable (p = 0.02). In terms of EL, the injury increased EL in flexion-extension (p = 0.02), the ISS increased EL for lateral bending and axial rotation (p ≤ 0.03), and the BPSS decreased EL in lateral bending (p = 0.02), with respect to the intact condition. The PLIF-ISS decreased lateral bending EL with respect to the ISS condition (p = 0.02), but not enough to be smaller or, at least, equivalent, to that of the PLIF-BPSS construct (p = 0.02). The ISS may be a suitable device to provide immediate flexion-extension balance after a unilateral laminotomy, but the BPSS provides greater immediate stability in lateral bending and axial rotation motions. Both PLIF constructs performed equivalently in flexion-extension and axial rotation, but the PLIF-BPSS construct is more resistant to lateral bending motions. Further biomechanical and clinical evidence is required to strongly support the recommendation of a stand-alone interspinous fusion device or as supplemental fixation to expandable posterior interbody cages.

Interspinous process device versus standard conventional surgical decompression for lumbar spinal stenosis: randomized controlled trial

Objective To assess whether interspinous process device implantation is more effective in the short term than conventional surgical decompression for patients with intermittent neurogenic claudication due to lumbar spinal stenosis....

Interspinous Distraction in Lumbar Spinal Stenosis

Prospective neurophysiological study. To identify and quantify the neurophysiological effects of interspinous distraction during spine surgery for lumbar spinal stenosis (LSS). Interspinous devices have been introduced as an alternative treatment of LSS in selected patients aiming at obtaining indirect decompression. Nevertheless, there is no data on the immediate neurophysiological effect of distraction. Thirty patients with LSS undergoing decompression (14 at single level, 16 at multiple levels) were enrolled, resulting in a total of 48 levels to be analyzed. Before decompression, calibrated incremental distraction simulating interspinous device implantation of 8, 10, 12, 14, and 16 mm was performed. Intraoperative motor evoked potentials were acquired before any distraction, during distraction at each incremental value and after bilateral decompression. We evaluated relative changes of motor evoked potentials normalized to hand muscles and related them to the number of affected levels, LSS radiological severity based on the A to D grading, lordosis, and disc height. For single-level disease, 8-mm distraction and open decompression yielded similar improvement in motor evoked potentials not only in levels with morphological grades A or B, but also in levels with morphological grades C or D (i.e., severe or extreme stenosis) (P = 0.32). In contrast, distraction superior to 8 mm was less effective (P ≤ 0.05). In multiple-level stenosis, decompression was significantly more effective than any degree of distraction (P < 0.001). No correlation of those results to disc height or lordosis was observed. Using χ trend test to analyze the effect of distraction, a linear trend favoring moderate over severe stenotic morphology was observed (P = 0.0349). Interspinous distraction of 8 mm is sufficient to replicate electrophysiological improvements obtained during full decompression even in severe single-level stenosis but not in multilevel disease. Interspinous distraction has therefore an immediately measurable neurophysiological effect. 4.