L4-L5 Segments Research Articles

Effect of lumbar fasciae on the stability of the lower lumbar spine

The biomechanical effect of tensioning the lumbar fasciae (LF) on the stability of the spine during sagittal plane motion was analysed using a validated finite element model of the normal lumbosacral spine (L4-S1). To apply the tension in the LF along the direction of the fibres, a local coordinate was allocated using dummy rigid beam elements that originated from the spinous process. Up to 10 Nm of flexion and 7.5 Nm of extension moment was applied with and without 20 N of lateral tension in the LF. A follower load of 400 N was additionally applied along the curvature of the spine. To identify how the magnitude of LF tension related to the stability of the spine, the tensioning on the fasciae was increased up to 40 N with an interval of 10 N under 7.5 Nm of flexion/extension moment. A fascial tension of 20 N produced a 59% decrease in angular motion at 2.5 Nm of flexion moment while there was a 12.3% decrease at 10 Nm in the L5-S1 segment. Its decrement was 53 and 9.6% at 2.5 Nm and 10 Nm, respectively, in the L4-L5 segment. Anterior translation was reduced by 12.1 and 39.0% at the L4-L5 and L5-S1 segments under 10 Nm of flexion moment, respectively. The flexion stiffness shows an almost linear increment with the increase in fascial tension. The results of this study showed that the effect of the LF on the stability of the spine is significant.

Does stabilization of the degenerative lumbar spine itself produce multifidus atrophy?

The effect of stabilization of the degenerative segment on changes in the pattern of paraspinal muscle activity was investigated using a previously developed musculoskeletal model. Muscle activity change depending on L4-L5 segment stabilization with and without taking into account the presence of multifidus atrophy according to direct invasion of the back muscle during surgery (MADIBM) was analysed in erect standing and 20° flexed postures. For the stabilization of the degenerative segment, a fusion or non-fusion stabilization with a pedicle-based dynamic stabilization system (PBDS) was applied. During erect standing, fusion generated a 12% reduction in the total multifidus muscle force, while its reduction was 6.6% with PBDS application. The presence of MADIBM produced 23.0% and 22.5% reductions in fusion and with PBDS application, respectively. During 20° flexion, 10.5% and 9.3% reductions were produced for fusion and PBDS application, respectively, and the corresponding values were 23.4% and 23.0%, respectively, in the presence of MADIBM. Increased facet joint contact forces were produced at the non-stabilized levels after stabilization while in erect standing posture. Alterations in muscle activity, which could be regarded as adaptions to altered spinal stability, may generate unexpected secondary problems in the spine.

Limiting interpedicular screw displacement increases shear forces in screws: A finite element study

Background contextScrew loosening has been reported for non-fusion devices. Forces on pedicle screws could be related to kinematic parameters as the interpedicular displacement (ID), which consists of the displacement between superior and inferior screw heads from full extension to full flexion. PurposeTo investigate the relationship between ID and screw loosening for different designs of posterior implants using a finite element model. MethodsAn L3-sacrum previously validated spine FE model was used. Three-rod designs were considered in L4-L5 segment: a rigid screw-rod implant, a flexible one and a specific design with a sliding rod providing limited restrain in ID. In order to simulate intermediate configurations, the friction coefficient between the sliding rods and connectors were varied. The sacrum was rigidly fixed. Rotations (flexion-extension, lateral bending and axial rotation) were applied to L3, for each modeled configuration: intact, injured, injured with different implants. Model consistency was checked with existing experimental in vitro data on intact and instrumented segments. Screw loads were computed as well as ID. ResultsIn flexion-extension, the ID was less than 2mm for rigid (R) and flexible (F) constructs and 5.5mm for intact spine and the sliding implant (S3). Screw's shear forces were 272N, 153N, 43N respectively for R, F and S3 constructs. ConclusionsImplants that allow ID presented lower screws loads. A compromise between the ability of the implant to withstand compressive forces, which requires longitudinal stiffness, and its ability to allow ID could be important for future implant designs in order to prevent screw loosening.

A combined passive and active musculoskeletal model study to estimate L4-L5 load sharing

A number of geometrically-detailed passive finite element (FE) models of the lumbar spine have been developed and validated under in vitro loading conditions. These models are devoid of muscles and thus cannot be directly used to simulate in vivo loading conditions acting on the lumbar joint structures or spinal implants. Gravity loads and muscle forces estimated by a trunk musculoskeletal (MS) model under twelve static activities were applied to a passive FE model of the L4-L5 segment to estimate load sharing among the joint structures (disc, ligaments, and facets) under simulated in vivo loading conditions. An equivalent follower (FL), that generates IDP equal to that generated by muscle forces, was computed in each task. Results indicated that under in vivo loading conditions, the passive FE model predicted intradiscal pressures (IDPs) that closely matched those measured under the simulated tasks (R2=0.98 and root-mean-squared-error, RMSE=0.18MPa). The calculated equivalent FL compared well with the resultant force of all muscle forces and gravity loads acting on the L4-L5 segment (R2=0.99 and RMSE=58N). Therefore, as an alternative approach to represent in vivo loading conditions in passive FE model studies, this FL can be estimated by available in-house or commercial MS models. In clinical applications and design of implants, commonly considered in vitro loading conditions on the passive FE models do not adequately represent the in vivo loading conditions under muscle exertions. Therefore, more realistic in vivo loading conditions should instead be used.

АНАЛИЗ КЛИНИКО-СТРУКТУРНЫХ ИЗМЕНЕНИЙ ПРИ ОСТЕОХОНДРОЗЕ ПОЯСНИЧНОГО ОТДЕЛА ПОЗВОНОЧНИКА У ЛИЦ ТРУДОСПОСОБНОГО ВОЗРАСТА

Aim. To assess clinical and anatomical preconditions for relapsing course of lumbar spine osteochondrosis. Material and methods. 71 patients of working age with lumbar spine osteochondrosis were examined. Clinical manifestations, neurological status and magnetic resonance imaging of lumbar spine were analyzed. The analysis took into account gender characteristics and age subgroup. Results. Damage of L3L4 segment was registered in 17 cases (in 3 women and 14 men predominantly of 2 and 3 age subgroup), however all of them had combined character: 9 protrusions (average size – 2.6 ± 0.6 mm) and 8 hernias (average size – 5.6 ± 4.3 mm). Damage of L4L5 segment either isolated or combined is registered in 47 cases out of 71 (in 8 women and 39 men predominantly of 2 and 3 age subgroup): 15 protrusions (average size – 2.9 ± 1.0 mm) and 32 hernias (average size – 6.2 ± 1.8 mm). Damage of L5S1 segment – in 55 cases out of 71 (in 10 women and 45 men predominantly of 2 and 3 age subgroup): 15 protrusions (average size – 2.4 ± 0.8 mm) and 40 hernias (average size – 7.4 ± 2.8 mm). Conclusion. There was a lack of dependence between degenerative changes in L3L4, L4L5, L5S1 segments and age and gender. Statistically significant correlation between degree of spine degenerative changes and severity of clinical manifestations was found.

Is a gradual reduction of stiffness on top of posterior instrumentation possible with a suitable proximal implant? A biomechanical study

Background ContextProximal junctional kyphosis (PJK) is a challenging complication after rigid posterior instrumentation (RI) of the spine. Several risk factors have been described in literature so far, including the rigidity of the cranial aspect of the implant. PurposeThe aim of this biomechanical study was to compare different proximal implants designed to gradually reduce the stiffness between the instrumented and non-instrumented spine. Study Design/SettingThis is a biomechanical study. MethodsEight calf lumbar spines (L2–L6) underwent RI with a titanium pedicle screw rod construct at L4–L6. The proximal transition segment (L3–L4) was instrumented stepwise with different supplementary implants—spinal bands (SB), cerclage wires (CW), hybrid rods (HR), hinged pedicle screws (HPS), or lamina hooks (LH)—and compared with an all-pedicle screw construct (APS). The flexibility of each segment (L2–L6) was tested with pure moments of ±10.0 Nm in the native state and for each implant at L3–L4, and the segmental range of motion (ROM) was evaluated. ResultsOn flexion and extension, the native uninstrumented L3–L4 segment showed a mean ROM of 7.3°. The CW reduced the mean ROM to 42.5%, SB to 41.1%, HR to 13.7%, HPS to 12.3%, LH to 6.8%, and APS to 12.3%. On lateral bending, the native segment L3–L4 showed a mean ROM of 15°. The CW reduced the mean ROM to 58.0%, SB to 78.0%, HR to 6.7%, HPS to 6.7%, LH to 10.0%, and APS to 3.3%. On axial rotation, the uninstrumented L3–L4 segment showed a mean ROM of 2.7°. The CW reduced the mean ROM to 55.6%, SB to 77.8%, HR to 55.6%, HPS to 55.6%, LH to 29.6%, and APS to 37.0%. ConclusionsUsing CW or SB at the proximal transition segment of a long RI reduced rigidity by about 60% in relation to flexion and extension in that segment, whereas the other implants tested had a high degree of rigidity comparable with APS. Clinical randomized controlled trials are needed to elucidate whether this strategy might be effective for preventing PJK.

Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion: A finite element analysis

Background dataCombined usage of posterior lumbar interbody fusion and transpedicular fixation has been extensively used to treat the various lumbar degenerative disc diseases. The transpedicular fixator aims to increase stability and enhance the fusion rate. However, how the fused disc and bridged vertebrae respectively affect adjacent-segment diseases progression is not yet clear. MethodsUsing a validated lumbosacral finite-element model, three variations at the L4–L5 segment were analyzed: 1) moderate disc degeneration, 2) instrumented with a stand-alone cage and pedicle screw fixators, and 3) with the cage only after fusion. The intersegmental angles, disc stresses, and facet loads were examined. Four motion tests, flexion, extension, bending, and twisting, were also simulated. FindingsThe adjacent-segment disease was more severe at the cephalic segment than the caudal segment. After solid fusion and fixation, the increase in intersegmental angles, disc stresses and facet loads of the adjacent segments were about 57.6%, 47.3%, and 59.6%, respectively. However, these changes were reduced to 30.1%, 22.7%, and 27.0% after removal of the fixators. This was attributed to the differences between the biomechanical characteristics of the fusion and fixation mechanisms. InterpretationFixation superimposes a stiffer constraint on the mobility of the bridged segment than fusion. The current study suggested that the removal of spinal fixators after complete fusion could decrease the stress at adjacent segments. Through a minimally invasive procedure, we could reduce secondary damage to the paraspinal structures while removing the fixators, which is of utmost concern to surgeons.

Prevention of Remifentanil Induced Postoperative Hyperalgesia by Dexmedetomidine via Regulating the Trafficking and Function of Spinal NMDA Receptors as well as PKC and CaMKII Level In Vivo and In Vitro

Remifentanil-induced secondary hyperalgesia has been demonstrated in both animal experiments and clinical trials. Enhancement of N-methyl-D-aspartate (NMDA) receptor trafficking as well as protein kinase C (PKC) and calmodulin-dependent protein kinase II (CaMKII) have been reported to be involved in the induction and maintenance of central sensitization. In the current study, it was demonstrated that dexmedetomidine could prevent remifentanil-induced hyperalgesia (RIH) via regulating spinal NMDAR-PKC-Ca2+/ CaMKII pathway in vivo and in vitro. We firstly investigated the effect of dexmedetomidine, a highly selective α2-adrenergic receptor agonist, on mechanical and thermal hyperalgesia using a rat model of RIH. NMDA receptor subunits (NR1, NR2A and NR2B) expression and membrane trafficking as well as PKC and CaMKII expression in spinal cord L4–L5 segments were measured by Western blot analysis. The expression of NMDA receptor subunits (NR1, NR2A and NR2B) were also detected by immunohistochemistry. Further more, the effect of dexmedetomidine on NMDA receptor current amplitude and frequency in spinal cord slices were investigated by whole-cell patch-clamp recording. We found that remifentail infusion at 1.2 μg.kg−1.min−1 for 90 min caused mechanical and thermal hyperalgesia, up-regulated NMDA receptor subunits NR1 and NR2B expression in both membrane fraction and total lysate as well as increased PKC and CaMKII expression in spinal cord dorsal horn. Subcutaneously injection of dexmedetomidine at the dose of 50 μg/kg at 30 min before plantar incision significantly attenuated remifentanil-induced mechanical and thermal hyperalgesia from 2 h to 48 h after infusion, and this was associated with reversal of up-regulated NR1 and NR2B subunits in both membrane fraction and total lysate as well as increased PKC and CaMKII expression in spinal cord dorsal horn. Furthermore, remifentanil incubation increased amplitude and frequency of NMDA receptor-induced current in dorsal horn neurons, which was dose-dependently attenuated by dexmedetomidine. These results suggest that dexmedetomidine can significantly ameliorate RIH via modulating the expression, membrane trafficking and function of NMDA receptors as well as PKC and CaMKII level in spinal dorsal horn, which present useful insights into the mechanistic action of dexmedetomidine as a potential anti-hyperalgesic agents for treating RIH.

Intradural Schwannoma Exacerbating the Symptoms of Degenerative Lumbar Stenosis: Case Report

Introduction Schwannoma is a common intradural slow-growing, benign and encapsulated tumor that originates from the myelin sheaths of the nerve fibers. However, a lumbar schwannoma complicating the symptoms of spinal stenosis is an extremely rare association. Aim To describe the case of a woman presenting a lumbar schwannoma in association with spinal stenosis. Case Report A 53 year-old female was referred to neurosurgical evaluation due to the worsening of a lumbar pain that was irradiating to the left inferior leg along the anterolateral surface. A neurological examination revealed motor deficits for extension of the left leg and attenuation of the left patellar reflex. Magnetic resonance imaging (MRI) showed lumbar spinal stenosis due to flavum ligament hypertrophy and disc herniation in the L3L4 and L4L5 segments, and an expansive lesion with homogeneous contrast enhancement occupying the left neuroforamen of the L3L4 segment. The patient underwent surgical resection of the tumor and decompression of the stenotic segments with posterior screw instrumentation from L3 to L5. She presented an uneventful recovery and significant improvement of the lumbar pain, and was still free of symptoms 6 months after surgery. An anatomopathological examination defined the tumor as a schwannoma (Grade I – World Health Organization [WHO]). Conclusion The present study highlights that lumbar schwannoma is a possible etiology complicating the symptoms of patients with previous lumbar spinal stenosis. It is important to treat both pathologies to improve the patients' symptoms.

The Effects of Physiological Biomechanical Loading on Intradiscal Pressure and Annulus Stress in Lumbar Spine: A Finite Element Analysis.

The present study was conducted to examine the effects of body weight on intradiscal pressure (IDP) and annulus stress of intervertebral discs at lumbar spine. Three-dimensional finite element model of osseoligamentous lumbar spine was developed subjected to follower load of 500 N, 800 N, and 1200 N which represent the loads for individuals who are normal and overweight with the pure moments at 7.5 Nm in flexion and extension motions. It was observed that the maximum IDP was 1.26 MPa at L1-L2 vertebral segment. However, the highest increment of IDP was found at L4-L5 segment where the IDP was increased to 30% in flexion and it was more severe at extension motion reaching to 80%. Furthermore, the maximum annulus stress also occurred at the L1-L2 segment with 3.9 MPa in extension motion. However, the highest increment was also found at L4-L5 where the annulus stress increased to 17% in extension motion. Based on these results, the increase of physiological loading could be an important factor to the increment of intradiscal pressure and annulus fibrosis stress at all intervertebral discs at the lumbar spine which may lead to early intervertebral disc damage.

Elastic constants influence on the L4-L5-S1 annuli fibrosus behavior, a probabilistic finite element analysis.

A probabilistic finite element (FE) analysis of the L4-L5 and L5-S1 human annulus fibrosus (AF) was conducted to obtain a better understanding of the biomechanics of the AF and to quantify its influence on the range of motion (ROM) of the L4-L5 and L5-S1 segments. The FE models were composed of the AF and the upper and lower endplates. The AF was represented as a continuous material composed of a hyperelastic isotropic Yeoh matrix reinforced with two families of fibers described with an exponential energy function. The caudal endplate was fully restricted and 8 Nm pure moment was applied to the cranial endplate in flexion, extension, lateral flexion and axial rotation. The mechanical constants were determined randomly based on a normal distribution and average values reported. Results of the 576 models show that the ROM was more sensitive to the initial stiffness of the fibers rather than to the stiffening coefficient represented in the exponential function. The ROM was more sensitive to the input variables in extension, flexion, axial rotation and lateral bending. The analysis showed an increased probability for the L5-S1 ROM to be higher in flexion, extension and axial rotation, and smaller in lateral flexion, with respect to the L4-L5 ROM. An equation was proposed to obtain the ROM as a function of the elastic constants of the fibers and it may be used to facilitate the calibration process of the human spine segments and to understand the influence of each elastic constant on the ROM.

脊柱L3~L4段的一体化三维光学模型构建及其生物力学分析

脊柱L3~L4段的一体化三维光学模型构建及其生物力学分析

Torso Muscle Physical Capacity and Functional Movements Interfaces

Darbo tikslas – įvertinti liemens raumenų fizinį pajėgumą, funkcinių judesių atlikimą ir išanalizuoti sąsajas tarp šių komponentų. Dažniausiai vertinamas vienas segmentas: judesio amplitudė, asmens fiziniai duomenys, tam tikra raumenų grupė, tačiau nėra analizuojamos sąsajos tarp gautų rezultatų, o tai sunkina asmens fizinio parengtumo lygio ir atliekamo judesio kokybės visapusišką įvertinimą. Šis tyrimas apima kompleksinį požiūrį į žmogaus organizmą, jo fizinį pajėgumą ir funkcinius judesius. Lietuvos ir užsienio mokslininkai, pastaraisiais metais atlikę daug jauno amžiaus asmenų sveikatos tyrimų, teigia, kad mažėja žmonių, turinčių puikią sveikatą, kartu daugėja asmenų, turinčių įvairių sveikatos sutrikimų. Viena blogėjančios sveikatos priežasčių – mažas fizinis aktyvumas, prevencijos nebuvimas. Pasikeitė gyvenimo būdas, jis tapo sėslesnis, laisvalaikis leidžiamas pasyviau, taip pat pakito ir kasdieninės veiklos įpročiai, buvę prieš 15–20 metų. Prastėjant sveikatai, prastėja ir fizinis pajėgumas bei funkcinių judesių atlikimas. [...]

Effects of the level of mono-segmental dynamic stabilization on the whole lumbar spine

Little biomechanical data has been gathered for the biomechanical effects of pedicle-based dynamic stabilization system (PBDS) and fusion (a conventional titanium rod and cage) to the whole lumbar spine according to the instrumentation level. A previously validated three-dimensional, intact osteoligamentous L1-S1 finite element model was modified to incorporate three different PBDS (Dynesys, Nflex, or PEEK) and fusion at three different levels (L3-L4, L4-L5, and L5-S1). A new loading method that can create the segmental motion similar to an in-vivo measurement was applied to the model. The biomechanical changes in the stabilized models were compared with those of the intact model during sagittal plane motion. The simulation results demonstrated that Dynesys generated relatively larger motion when it was instrumented at the L3-L4 segment, whereas the Nflex was the most appropriate device for L4-L5 stabilization. Depending on the stabilization device and instrumented level, whole-lumbar segmental motion also varied. During flexion, stabilization at the L3-L4 level or L4-L5 level produced a relatively higher increase in the motion at all cranial levels. Stabilization at the L5-S1 level generated a slight decrease in the motion at the adjacent cranial level without respect to the type of fixation. In cases of fusion, the change in the motion was higher relative to that with PBDS. Given the biomechanical change at each level after stabilization, adjacent segment degeneration was expected cranially rather caudally, and the probability of this degeneration differed depending on the stabilization level and device.

Adult Spinal Deformity in the Elderly. Preliminary Clinical and Radiological Results in 22 Patients Treated by a Two Times Minimally Invasive Spine Surgery

Introduction The adult spinal deformity (ASD) seems, in the last years, in a progressive increment. It should be in relation to the aging of the population. This trend leads to a progression of the disability and the reduction of the quality of life of these patients. The surgical correction of the ASD obtained by a traditional “open” surgery can often be incompatible with the co-morbidities of these patients. The minimally invasive surgery for correction of the deformities (MISDEF) can offer technical nuances, such as reduce of intraoperative blood loss and quickly recovery, which can lead the opportunities for these patients to approach the surgery. We present the preliminary results of our observational study on the radiological correction and clinical results of old patients affected by ASD treated by MISDEF. Methods Observational study with 20 months of follow-up. Twelve patients affected by low-back pain, sciatalgia and/cruralgia, neurological claudication were enrolled in this study. All the patients underwent to a MISDEF based on a percutaneous transpedicular stabilization plus a lateral or transforaminal interbody fusion. We collected all the radiological datas, such as sagittal vertical axis (SVA), sacral slope (SS), pervic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL) and coronal cob (CC) and the clinical status, oswestry disability index (ODI) and SF-36. Results The mean age was 70 years (65 – 78 years), 3 men and 9 women. 7 patients presented a lumbar left side convex scoliosis, while 5 patients presented a right side one. All the patients underwent to a 2 times surgery: the first time was a lateral access, the second time was the posterior access. The side for the lateral interbody fusion was the concave side of the scoliosis. L4L5 segment was always been approached for a transforaminal interbody fusion. The proximal strumental vertebra was T10. The mean intraoperative blood loss was 500 cc. All the patients were mobilized within 2 days. The ODI and SF36 evidenced a statistically improvement ( p < 0,05). No evidence of infections, neurological deficit, failure of the implant and/or loosening of correction were documented in the follow up. Conclusions The MISDEF offers, even for elderly patients with co-morbidities, a valid and secure surgical solution for the correction of the ASD. From the results of our study appeared a good compliance of these techniques for all the patients, with a good result even at 20 months of follow-up. We considered that the opportunity to separate the surgical correction of the deformity in 2 times surgery seems to be a better and secure solution especially for elderly patients.

Transforaminal Lumber Interbody Fusion (TLIF) Clinical and Radiological Outcome

Objective To evaluate the clinical and radiological outcome of TLIF in the treatment of Spondylolisthesis, degenerative disc disease and recurrent herniation of lumber disc. Methodology: A retrospective study, between Jan 2009 and December 2011.The patients with chronic back pain (more than 6 months of disability and refractory to conservative management) with or without leg pain / neurological deficit due to degenerative spondylolisthesis, degenerative disc disease and recurrent lumber disc herniation treated with Transforaminal Lumber Interbody Fusion (TLIF) were included. It was a retrospective review of the patient files to assess the pre and postoperative symptomatology, findings on clinical examination, radiological characteristics. The same procedure was performed in all cases by a single spine surgeon. The clinical outcome was assessed using Oswestry Disability Index (ODI) scoring system. Bony fusion was assessed based on a pre-set criteria on plain radiographs at 18 months postoperatively. Results Of 25 there were 16 male (64%) and 9 female (36%) patients with a mean age of 40 years (range: 20–60), who underwent TLIF (Transforaminal Lumber Interbody Fusion). 9 patients diagnosed as degenerative disc disease, 12 with spondylolisthesis and 4 having recurrent disc herniation. Of the 25 patients who underwent TLIF, in 14 (56%) cases fusion was performed at L5-S1, in 9 (36%) at segment L4-L5 and in 2 (8%) at L3-L4. We found subjective improvement in symptoms of back pain in 19 (76.0%) of 25 patients, leg pain in 15 (83.3%) of 18, and 04 (66.67%) & 02(40.0%) improvement in sensory and motor deficit respectively postoperatively. Based on the Oswestry Disability Index (ODI) and Visual Analog Pain Scale (VAS), showed significant improvement from preoperative 7.1 & 42.3 to 2.5 & 17.5 ODI and VAS scores at 18 months postoperatively respectively, with an overall improvement of 4.6 VAS and 24.8 ODI scores. A radiological fusion was observed at 18 months postoperatively on anterio-posterior (AP) and lateral X-rays following the pre set criteria in 23 of 25 patients (92.00%). Conclusion TLIF is a safe and effective method to treat chronic low back pain in patients with spondylolisthesis, degenerative disc disease and recurrent disc herniation. Our results confirm that TLIF is an option that is associated with good clinical and radiological outcome.

Characterization of the L4–L5–S1 motion segment using the stepwise reduction method

The two aims of this study were to generate data for a more accurate calibration of finite element models including the L5–S1 segment, and to find mechanical differences between the L4–L5 and L5–S1 segments. Then, the range of motion (ROM) and facet forces for the L4–S1 segment were measured using the stepwise reduction method. This consists of sequentially testing and reducing each segment in nine stages by cutting the ligaments, facet capsules, and removing the nucleus. Five L4–S1 human segments (median: 65 years, range: 53–84 years, SD=11.0 years) were loaded under a maximum pure moment of 8Nm. The ROM was measured using stereo-photogrammetry via tracking of three markers and the facet contact forces (CF) were measured using a Tekscan system. The ROM for the L4–L5 segment and all stages showed good agreement with published data. The major differences in ROM between the L4–L5 and L5–S1 segments were found for lateral bending and all stages, for which the L4–L5 ROM was about 1.5–3 times higher than that of the L5–S1 segment, consistent with L5–S1 facet CF about 1.3 to 4 times higher than those measured for the L4–L5 segment. For the other movements and few stages, the L4–L5 ROM was significantly lower that of the L5–S1 segment. ROM and CF provide important baseline data for more accurate calibration of FE models and to understand the role that their structures play in lower lumbar spine mechanics.

Crosstalk between astrocytic CXCL12 and microglial CXCR4 contributes to the development of neuropathic pain.

Background Chemokine axis chemokine C-X-C motif ligand 12/C-X-C chemokine receptor type 4 (CXCL12/CXCR4) is an emerging pain modulator, but mechanisms for its involvement in neuropathic pain remain unclear. Here, we aimed to study whether CXCL12/CXCR4 axis modulated the development of neuropathic pain via glial mechanisms. In this study, two mouse models of neuropathic pain, namely partial sciatic nerve ligation (pSNL) model and chronic post-ischemia pain (CPIP) model, were used.Results In the dorsal horn of L3–L5 segment of spinal cord, CXCL12 and CXCR4 were expressed in both astrocyte and microglia in normal mice. In the pSNL or CPIP model, the expression level of CXCL12 in the ipsilateral L3–L5 segment of mice spinal cord was increased in an astrocyte-dependent manner on post-operative day (POD) 3. Intrathecal administration of CXCL12 with AMD3100 (CXCR4 antagonist) or minocycline (microglia activation inhibitor), but not fluorocitrate (astrocyte activation inhibitor), reversed CXCL12-indued mechanical allodynia in naïve mice. In these models, AMD3100 and AMD3465 (CXCR4 antagonist), administered daily from 1 h before surgery and up to POD 3, attenuated the development of mechanical allodynia. Moreover, AMD3100 administered daily from 1 h before surgery and up to POD 3 downregulated mRNA levels of tumor necrosis factor alpha, interleukin 1β, and interleukin 6 in the ipsilateral L3–L5 segment of spinal cord in the pSNL and CPIP models on POD 3.Conclusion This study demonstrates the crosstalk between astrocytic CXCL12 and microglial CXCR4 in the pathogenesis of neuropathic pain using pSNL and CPIP models. Our results offer insights for the future research on CXCL12/CXCR4 axis and neuropathic pain therapy.

Sagittal plane rotation center of lower lumbar spine during a dynamic weight-lifting activity

This study investigated the center of rotation (COR) of the intervertebral segments of the lower lumbar spine (L4-L5 and L5-S1 segments) in sagittal plane during a weight-lifting (3.6kg in each hand) extension activity performed with the pelvis constrained. Seven healthy subjects were studied using a dual fluoroscopic imaging technique. Using the non-weightbearing, supine position during MRI scan as a reference, the average intervertebral flexion angles of the L4-L5 and L5-S1 were 6.6° and 5.3° at flexion position of the body, respectively, and were −1.8° and −3.5° at extension position of the body, respectively. The CORs of the lower lumbar spine were found segment-dependent and changed with the body postures. The CORs of the L4-L5 segment were at the location about 75% posterior from the anterior edge of the disc at flexion positions of the body, and moved to about 92% of the posterior portion of the disc at extension positions of the body. The CORs of the L5-S1 segment were at 95% posterior portion of the disc at flexion positions of the body, and moved outside of the posterior edge of the disc by about 12% of the disc length at extension positions of the body. These results could help understand the physiological motion characters of the lower lumbar spine. The data could also provide important insights for future improvement of artificial disc designs and surgical implantation of the discs that are aimed to reproduce normal spinal functions.

MICROSURGICAL LANDMARKS IN MINIMALLY INVASIVE TRANSFORAMINAL LUMBAR INTERBODY FUSION

Microsurgical landmarks of the facet joint complex were defined to provide guidance and security within the tubular retractor during transforaminal surgery. A retrospective observational study was performed in segments L4-L5 by the left side approach. Microsurgical relevant photos, anatomical models and drawing were used to expose the suggested landmarks. The MI-TLIF technique has advantages compared with conventional open TLIF technique, however minimally invasive technique implies lack of security for the surgeon due to the lack of defined microanatomical landmarks compared to open spine surgery, and disorientation within the tubular retractor, the reason why to have precise microsurgical references and its recognition within the surgical field provide speed and safety when performing minimally invasive technique.