Anterior Annulus Fibrosus Research Articles

Analysis of chronic low back pain with magnetic resonance imaging T2 mapping of lumbar intervertebral disc

BackgroundMagnetic resonance imaging (MRI) T2 mapping utilizes the T2 values for quantification of moisturecontent and collagen sequence breakdown. Recently, attempts at quantification of lumbar disc degeneration through MRI T2 mapping have been reported. We conducted an analysis of the relationship between T2 values of degenerated intervertebral discs (IVD) and chronic low back pain (CLBP). MethodsThe subjects who had CLBP comprised 28 patients (15 male, 13 female; mean age 48.9 ± 9.6 years; range 22–60 years). All subjects underwent MRI and filled out the low back pain visual analog scale (VAS) and Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ). The disc was divided into the anterior annulus fibrosus (AF), the nucleus pulposus (NP), and the posterior AF, and each T2 value was measured. This study involved 25 asymptomatic control participants matched with the CLBP group subjects for gender and age (13 male, 12 female; mean age 43.8 ± 14.5 years; range 23–60 years). These subjects had no low back pain, and constituted the control group. ResultsT2 values for IVD tended to be lower in the CLBP group than in the control group, and these values were significantly different within the posterior AF. The correlation coefficients between the VAS scores and T2 values of anterior AF, NP and posterior AF were r = 0.30,−0.15 and −0.50. The correlation coefficient between the JOABPEQ scores (low back pain) and T2 values of anterior AF, NP and posterior AF were r = −0.0041, 0.11 and 0.42.Similarly, the JOABPEQ scores (lumbar function) were r = −0.22, −0.12 and 0.57. ConclusionsThe results indicated a correlation between posterior AF degeneration and CLBP. This study suggeststhat MRI T2 mapping could be used as a quantitative method for diagnosing discogenic pain.

Age- and degeneration-related variations in cell density and glycosaminoglycan content in the human cervical intervertebral disc and its endplates.

The first aim of this study was to quantify cell density in cervical intervertebral discs (IVDs) and endplates of varying age and degeneration grade. The second aim was to analyze glycosaminoglycan (GAG) content in cervical IVDs and their endplates. Sixty cervical IVDs were excised from 30 human cadavers, not later than 24 hours post-mortem. Each sample underwent sectioning. Half of each sample underwent GAG content analysis using the dimethylmethylene blue binding assay. The other half underwent histological processing, histological degeneration grading, and cell density assessment using the Abercrombie method. The nucleus pulposus (NP) (4218 ± 417 cells/mm³) had significantly higher cell density than the anterior annulus fibrosus (AF) (3283 ± 438 cells/mm³; p < 0.0001), and similar cell density (4464 ± 551 cells/mm³; p = 0.36) to the posterior AF. Cell density was similar throughout the different regions of the endplate. The NP (619 ± 178 µg/mg dry weight) had a significantly higher GAG content than both the anterior (428 ± 199 µg/mg dry weight; p < 0.0001) and posterior AF (524 ± 218 µg/mg dry weight; p < 0.0001). In conclusion, this study introduces detailed 3D maps of cervical IVD and endplate cell density and GAG content. Furthermore, it shows that cervical IVDs and their endplates only slightly differ, in terms of cell density and GAG content, from lumbar IVDs.

Segmental quantitative MR imaging analysis of diurnal variation of water content in the lumbar intervertebral discs.

ObjectiveTo investigate the changes in water content in the lumbar intervertebral discs by quantitative T2 MR imaging in the morning after bed rest and evening after a diurnal load.Materials and MethodsTwenty healthy volunteers were separately examined in the morning after bed rest and in the evening after finishing daily work. T2-mapping images were obtained and analyzed. An equally-sized rectangular region of interest (ROI) was manually placed in both, the anterior and the posterior annulus fibrosus (AF), in the outermost 20% of the disc. Three ROIs were placed in the space defined as the nucleus pulposus (NP). Repeated-measures analysis of variance and paired 2-tailed t tests were used for statistical analysis, with p < 0.05 as significantly different.ResultsT2 values significantly decreased from morning to evening, in the NP (anterior NP = -13.9 ms; central NP = -17.0 ms; posterior NP = -13.3 ms; all p < 0.001). Meanwhile T2 values significantly increased in the anterior AF (+2.9 ms; p = 0.025) and the posterior AF (+5.9 ms; p < 0.001). T2 values in the posterior AF showed the largest degree of variation among the 5 ROIs, but there was no statistical significance (p = 0.414). Discs with initially low T2 values in the center NP showed a smaller degree of variation in the anterior NP and in the central NP, than in discs with initially high T2 values in the center NP (10.0% vs. 16.1%, p = 0.037; 6.4% vs. 16.1%, p = 0.006, respectively).ConclusionSegmental quantitative T2 MRI provides valuable insights into physiological aspects of normal discs.

In vivo morphological features of human lumbar discs.

Recent biomechanics studies have revealed distinct kinematic behavior of different lumbar segments. The mechanisms behind these segment-specific biomechanical features are unknown. This study investigated the in vivo geometric characteristics of human lumbar intervertebral discs.Magnetic resonance images of the lumbar spine of 41 young Chinese individuals were acquired. Disc geometry in the sagittal plane was measured for each subject, including the dimensions of the discs, nucleus pulposus (NP), and annulus fibrosus (AF). Segmental lordosis was also measured using the Cobb method.In general, the disc length increased from upper to lower lumbar levels, except that the L4/5 and L5/S1 discs had similar lengths. The L4/5 NP had a height of 8.6 ± 1.3 mm, which was significantly higher than all other levels (P < 0.05). The L5/S1 NP had a length of 21.6 ± 3.1 mm, which was significantly longer than all other levels (P < 0.05). At L4/5, the NP occupied 64.0% of the disc length, which was significantly less than the NP of the L5/S1 segment (72.4%) (P < 0.05). The anterior AF occupied 20.5% of the L4/5 disc length, which was significantly greater than that of the posterior AF (15.6%) (P < 0.05). At the L5/S1 segment, the anterior and posterior AFs were similar in length (14.1% and 13.6% of the disc, respectively). The height to length (H/L) ratio of the L4/5 NP was 0.45 ± 0.06, which was significantly greater than all other segments (P < 0.05). There was no correlation between the NP H/L ratio and lordosis.Although the lengths of the lower lumbar discs were similar, the geometry of the AF and NP showed segment-dependent properties. These data may provide insight into the understanding of segment-specific biomechanics in the lower lumbar spine. The data could also provide baseline knowledge for the development of segment-specific surgical treatments of lumbar diseases.

Differential gene expression in anterior and posterior annulus fibrosus.

Laboratory study. To evaluate the differential gene expression of cytokines and growth factors in anterior versus posterior annulus fibrosus (AF) intervertebral disc (IVD) specimens. Histological analysis has demonstrated regional differences in vascular and neural ingrowth in the IVD, and similar differences may exist for cytokine and growth factor expression in patients with degenerative disc disease (DDD). Regional expression of these cytokines may also be related to the pain experienced in DDD. IVD tissue was obtained from patients undergoing anterior lumbar interbody fusion surgery for back pain with radiological evidence of disc degeneration. For a control group, the discs of patients undergoing anterior lumbar discectomy for degenerative scoliosis were obtained as well. The tissue was carefully removed and separated into anterior and posterior AF. After tissue processing, an antibody array was completed to determine expression levels of 42 cytokines and growth factors. Nine discs from 7 patients with DDD and 5 discs from 2 patients with scoliosis were analyzed. In the DDD group, there were 10 cytokines and growth factors with significantly increased expression in the posterior AF versus the anterior AF ([interleukin] IL-4, IL-5, IL-6, M-CSF, MDC, tumor necrosis factor β, EGF, IGF-1, angiogenin, leptin). In the scoliosis group, only angiogenin and PDGF-BB demonstrated increased expression in the posterior AF. No cytokines or growth factors had increased expression in the anterior AF compared with posterior AF. The posterior AF expresses increased levels of cytokines and growth factors compared with the anterior AF in patients with DDD. This differential expression may be important for targeting treatment of painful IVDs. N/A.

Internal three-dimensional strains in human intervertebral discs under axial compression quantified noninvasively by magnetic resonance imaging and image registration.

Study objectives were to develop, validate, and apply a method to measure three-dimensional (3D) internal strains in intact human discs under axial compression. A custom-built loading device applied compression and permitted load-relaxation outside of the magnet while also maintaining compression and hydration during imaging. Strain was measured through registration of 300 μm isotropic resolution images. Excellent registration accuracy was achieved, with 94% and 65% overlap of disc volume and lamellae compared to manual segmentation, and an average Hausdorff, a measure of distance error, of 0.03 and 0.12 mm for disc volume and lamellae boundaries, respectively. Strain maps enabled qualitative visualization and quantitative regional annulus fibrosus (AF) strain analysis. Axial and circumferential strains were highest in the lateral AF and lowest in the anterior and posterior AF. Radial strains were lowest in the lateral AF, but highly variable. Overall, this study provided new methods that will be valuable in the design and evaluation surgical procedures and therapeutic interventions.

Confocal microscopy demonstrates association of LTBP-2 in fibrillin-1 microfibrils and colocalisation with perlecan in the disc cell pericellular matrix

Comparative immunolocalisations of latent transforming growth factor-beta-1 binding protein (LTBP)-2, fibrillin-1, versican and perlecan were undertaken in foetal human and wild type C57BL/6 mouse and Hspg2 exon 3 null HS deficient mouse intervertebral discs (IVDs). LTBP-2 was a prominent pericellular component of annular fibrochondrocytes in the posterior annulus fibrosus (AF), interstitial matrix adjacent to nucleus pulposus (NP) cells and to fibrillar and cell associated material in the anterior AF of the human foetal IVD and also displayed a pericellular localisation pattern in murine IVDs. Perlecan and LTBP-2 displayed strong pericellular colocalisation patterns in the posterior AF and to fibrillar material in the outer anterior AF in the foetal human IVD. Versican was a prominent fibril-associated component in the posterior and anterior AF, localised in close proximity to fibrillin-1 in fibrillar arrangements in the cartilaginous vertebral rudiments around paraspinal blood vessels, to major collagen fibre bundles in the anterior and posterior AF and shorter fibres in the NP. Fibrillin-1 was prominent in the outer anterior AF of the human foetal IVD and in fibres extending from the AF into the cartilaginous vertebral rudiments. LTBP-2 was prominently associated with annular fibrils containing fibrillin-1, versican was localised in close proximity to these but not specifically with LTBP-2. The similar deposition levels of LTBP-2 observed in the AF of the Hspg2 exon 3 null and wild type murine IVDs indicated that perlecan HS was not essential for LTBP-2 deposition but colocalisation of LTBP-2 with perlecan in the foetal human IVD was consistent with HS mediated interactions which have already been demonstrated in-vitro.

A Computational Model to Describe the Regional Interlamellar Shear of the Annulus Fibrosus

Interlamellar shear may play an important role in the homeostasis and degeneration of the intervertebral disk. Accurately modeling the shear behavior of the interlamellar compartment would enhance the study of its mechanobiology. In this study, physical experiments were utilized to describe interlamellar shear and define a constitutive model, which was implemented into a finite element analysis. Ovine annulus fibrosus (AF) specimens from three locations within the intervertebral disk (lateral, outer anterior, and inner anterior) were subjected to in vitro mechanical shear testing. The local shear stress-stretch relationship was described for the lamellae and across the interlamellar layer of the AF. A hyperelastic constitutive model was defined for interlamellar and lamellar materials at each location tested. The constitutive models were incorporated into a finite element model of a block of AF, which modeled the interlamellar and lamellar layers using a continuum description. The global shear behavior of the AF was compared between the finite element model and physical experiments. The shear moduli at the initial and final regions of the stress-strain curve were greater within the lamellae than across the interlamellar layer. The difference between interlamellar and lamellar shear was greater at the outer anterior AF than at the inner anterior region. The finite element model was shown to accurately predict the global shear behavior or the AF. Future studies incorporating finite element analysis of the interlamellar compartment may be useful for predicting its physiological mechanical behavior to inform the study of its mechanobiology.

Strain distribution in the intervertebral disc under unconfined compression and tension load by the optimized digital image correlation technique

The unconfined compression and tension experiments of the intervertebral disc were conducted by applying an optimized digital image correlation technique, and the internal strain distribution was analysed for the disc. It was found that the axial strain values of different positions increased obviously with the increase in loads, while inner annulus fibrosus and posterior annulus fibrosus experienced higher axial strains than the outer annulus fibrosus and anterior annulus fibrosus. Deep annulus fibrosus exhibited higher compressive and tensile axial strains than superficial annulus fibrosus for the anterior region, while there was an opposite result for the posterior region. It was noted that all samples demonstrated a nonlinear stress-strain profile in the process of deforming, and an elastic region was shown once the sample was deformed beyond its toe region.

Investigation of intervertebral disc and facet joint in lumbar spondylolisthesis using T2 mapping.

We measured T2 relaxation time of the intervertebral discs (IVD) and facet joints (FJ) in patients with degenerative spondylolisthesis (DS) and no spondylolisthesis (NS) and investigated the characteristics of these parts in DS. In 40 patients with DS and 40 patients with NS, we measured T2 relaxation time of the IVD and FJ and compared them between groups. In the group with DS, we also examined the relationship between the degree of slippage using Meyerding grade and T2 relaxation of each part in the IVD and FJ. T2 relaxation time of the IVD tended to be lower in the DS than NS group and differed significantly (P < 0.01) within the anterior annulus fibrosus. T2 relaxation time in the FJ was significantly higher in the DS than NS group. T2 relaxation time in the FJ was significantly higher for those assessed Meyerding Grade II than Grade I, although we observed no significant differences in T2 relaxation time in any area of the IVD. T2 relaxation time decreased in the anterior annulus fibrosus of the IVD and increased in the FJ in patients with DS, suggesting an association of IVD and FJ degeneration with the development of lumbar DS.

Accelerated T1rho relaxation quantification in intervertebral disc using limited spin-lock times.

T1rho relaxation measurement has the potential to identify early biochemical changes in the intervertebral disc. Traditionally, multiple spin-lock times (SLT), often ~5 SLTs, are used to ensure the accuracy and robustness of T1rho mapping. It will be advantageous to use fewer SLT points if comparable accuracy of T1rho mapping can be achieved. In this study, the feasibility of using 3 SLT points to measure intervertebral disc T1rho relaxation time is explored. The lumbar spine of 12 subjects (age range: 30-75 years, disc =60) were studied on 3-T MRI. For T1rho measurement, a rotary echo spin-lock pulse was implemented in a 3D balanced fast field echo (b-FFE) sequence. Spin-lock frequency was set as 500 Hz and the SLTs of 1, 10, 20, 40, and 60 ms were acquired. T1rho maps were generated by fitting each pixel's intensity as a function of SLT using a non-negative least-square fitting algorithm. Images were analysed in the mid-sagittal section. T1rho maps were re-constructed using all 5 SLT points of 1, 10, 20, 40, and 60 ms, and three SLT points of 1, 20, and 60 ms respectively. ROIs included nucleus pulposus (NP), anterior annulus fibrosus (AF) and posterior annulus fibrosus. Values of anterior AF and posterior AF were averaged as the value for AF. Agreement of T1rho measurements using different SLT points was assessed using intra-class correlation coefficient (ICC) on absolute agreement as well as Bland and Altman plot. There was no significant difference for T1rho values by 5-SLT measurement and 3-SLT measurement in both NP (P=0.63) and AF (P=0.31). The ICC for 5-SLT T1rho measurement vs. 3-SLT T1rho measurement was 0.991 and 0.981 respectively for NP and AF T1rho time. The Bland and Altman plots for the comparison showed a mean difference of 3.14 and 1.83 for NP and AF respectively. Polling the T1rho values for NP and AF in 60 discs together, the ICC for 5-SLT T1rho measurement vs. 3-SLT T1rho measurement was 0.993, and the Bland and Altman analysis showed a mean difference of 2.56. This study suggests that adopting 3 SLTs of 1, 20, and 60 ms can be an acceptable alternative for the disc T1rho measurement.

Comparative immunolocalisation of fibrillin-1 and perlecan in the human foetal, and HS-deficient hspg2 exon 3 null mutant mouse intervertebral disc

The aim of this study was to examine the comparative localisations of fibrillin-1 and perlecan in the foetal human, wild-type C57BL/6 and HS-deficient hspg2Δ³⁻/Δ³⁻ exon 3 null mouse intervertebral disc (IVD) using fluorescent laser scanning confocal microscopy. Fibrillin-1 fibrils were prominent components of the outer posterior and anterior annulus fibrosus (AF) of the foetal human IVD. Finer fibrillin-1 fibrils were evident in the inner AF where they displayed an arcade-type arrangement in the developing lamellae. Relatively short but distinct fibrillin-1 fibrils were evident in the central region of the IVD and presumptive cartilaginous endplate and defined the margins of the nuclear sheath in the developing nucleus pulposus (NP). Fibrillin-1 was also demonstrated in the AF of C57BL/6 wild-type mice but to a far lesser extent in the HS-deficient hspg2Δ³⁻/Δ³⁻ exon 3 null mouse. This suggested that the HS chains of perlecan may have contributed to fibrillin-1 assembly or its deposition in the IVD. The cell-matrix interconnections provided by the fibrillin fibrils visualised in this study may facilitate communication between disc cells and their local biomechanical microenvironment in mechanosensory processes which regulate tissue homeostasis. The ability of fibrillin-1 to sequester TGF-β a well-known anabolic growth factor in the IVD also suggests potential roles in disc development and/or remodelling.

Thermo-Reversible Hydrogel for Nucleus Pulposus Replacement: Feasibility under Static Loading in a mild Papain-induced Disk Degeneration Model

Introduction Nucleus pulposus (NP) replacement by the application of injectable hydrogels seems a straightforward approach for tissue engineering. We investigate a thermo-reversible hydrogel (TH-RHG), based on a modified polysaccharide with a thermo-reversible polyamide (poly(N-isopropylacrylamide = pNIPAM). Using “click chemistry” and reversible addition fragmentation transfer (RAFT) polymerization,2,3 the gel is made to behave as a liquid at room temperature and hardens at &gt;32°C. To inject the hydrogel, a mild papain disk degeneration model (PDDM) is employed that creates a cavity in the intervertebral disk. Here, we investigate the performance of the TH-RHG in situ in bovine IVD with preconditioned human mesenchymal stem cells (hMSC) with rhGDF-5. Materials and Methods IVDs were harvested from six calf tails, aged 6 to 9 months, which were received from a local abattoir within 3 to 5 hour of slaughter. The bovine IVDs of intermediate size (max. height of 2 cm and diameter of 1.5 cm) were used included the bony endplates and cultured in vitro for 16 days. Utilizing our previously established PDDM was necessary to create a cavity in the NP. For the papain injection, a 25 G needle was used to inject centrally the enzyme into the bovine IVD. Simultaneously, primary hMSCs expanded from bone marrow obtained from five patients undergoing spine surgery (ethically approved) were seeded at 4M cells/mL in 3-D in the TH-RHG and preconditioned with 100 ng/mL rhGDF-5 for 7 days. Afterwards, the TH-RHG was reversed to a fluid and injected into the IVD organ culture and kept under static loading of 0.1 MPa for 7 days using custom-designed specimen chambers.1 Experimental designs are as follows (i) fresh d0 control PBS injection (ii) PDDM + PBS injection (iii) PDDM + TH-RHG + bovine NPCs (Cell control) (iv) PDDM + TH-RHG + hMSC.4 Magnetic resonance imaging (MRI) was employed to image the hydrogel-filled cavity before and after loading at day 9 and day 16, and RT-PCR comparison of the hMSCs at day 1, 8, and 15 investigated the changes in gene expression. On the same days of cell sampling, cell viability (trypan blue) was determined. Sulfated glycosaminoglycan synthesis (DMMB assay) and DNA content (Picogreen assay) from anterior and posterior annulus fibrosus (AF) segments of each disk at day 16 were performed. Results MRI images confirmed a central positioning of the TH-RHG into the PDDM. A considerable drop in volume across all groups in the NP region and consequently of disk height was observed between day 9 and day 16. The RT-PCR results of injected hMSCs showed significant differences between day 8 and day 15 for versican and Sox9 relative to day 1 (Fig. 1). The results of bovine AF gene expression relative to control AF showed significant differences between groups for ACAN, Col1, Col2, IL-b1, versican, ADAMTS-4, Casp-8, MMP13, and MMP3. Cell viability of injected cells dropped from around ∼100% down to ∼87% for bovine cells and ∼86% for hMSC after 7 days in 3D culture. It further dropped to ∼72% after organ culture. GAG/DNA ratio showed significant difference across groups irrespective of posterior or anterior location. Conclusion MRI imaging of TH-RHG seems a promising protocol for noninvasively observing the gel performance in vitro. 10% TH-RHG is a feasible scaffold for in vitro 3D preconditioning of hMSCs and can be used at the same time for direct injection into the IVD. However, the TH-RHG has been shown to be unable to bare static load leading to a drop of cell viability. Relative gene expression of the hMSC phenotype after “co-culture”, however, points towards “discogenic” differentiation.5 Acknowledgements This project is funded by HansJörg Wyss Start up Award 2011/Project no. 102646/AOSpine International. I confirm having declared any potential conflict of interest for all authors listed on this abstract No Disclosure of Interest None declared Chan, et al. Spine 2011. Mortisen, et al. Biomacromolecules 2010;11(5):1261–1272 Mortisen, et al. PCT2009, 3-3-2009 2009;141 Gantenbein-Ritter, et al. European Spine Journal 2011;20:962–971 Peroglio, et al. European Spine Journal 2011;epub

Analysis of Degenerative Discs in Lumbar Spondylolisthesis Using MRI T2 Mapping

Background: Spinal instability, including lumbar degenerative spondylolisthesis (DS), mainly results from degeneration of intervertebral discs (IVD) and the facet joints (FJ). Characterization of the relationship between IVD degeneration in cases of lumbar degenerative spondylolisthesis (DS), and T2 values may be useful for accurate noninvasive evaluation and subsequent treatment. Thus, the goal of this study was to measure T2 values of IVDs in cases with (DS) and without (NS) spondylolisthesis, and to characterize changes of IVDs in DS. Methods: A total of 40 subjects who presented with L4 spondylolisthesis comprised the DS group. Another 40 subjects who did not have lumbar spondylolisthesis, constituted the NS group. T2 values of IVDs were measured and compared in these groups. Results: T2 values for IVDs tended to be lower in the DS group than in the NS group, and these values were significantly different (p < 0.01) within the anterior annulus fibrosus (AF). No significant differences in T2 values between Meyerding grades I and II were observed in any areas of IVDs. Conclusions: It is speculated that in the early stages, the degeneration of the anterior AF develops and is related to the onset of lumbar spondylolisthesis, while in later stages, degeneration of facet joints influences the progression of spondylolisthesis.

Quantitative in vivo MRI evaluation of lumbar facet joints and intervertebral discs using axial T2 mapping

To assess the feasibility of T2 mapping of lumbar facet joints and intervertebral discs in a single imaging slab and to compare the findings with morphological grading. Sixty lumbar spine segments from 10 low back pain patients and 5 healthy volunteers were examined by axial T2 mapping and morphological MRI at 3.0 Tesla. Regions of interest were drawn on a single slice for the facet joints and the intervertebral discs (nucleus pulposus, anterior and posterior annulus fibrosus). The Weishaupt grading was used for facet joints and the Pfirrmann score was used for morphological disc grading ("normal" vs. "abnormal" discs). The inter-rater agreement was excellent for the facet joint T2 evaluation (r = 0.85), but poor for the morphological Weishaupt grading (kappa = 0.15). The preliminary results show similar facet joint T2 values in segments with normal and abnormal Pfirrmann scores. There was no difference in mean T2 values between facet joints in different Weishaupt grading groups. Facet joint T2 values showed a weak correlation with T2 values of the posterior annulus (r = 0.32) This study demonstrates the feasibility of a combined T2 mapping approach for the facet joints and intervertebral discs using a single axial slab.

Correlation between T2 relaxation time and intervertebral disk degeneration

Magnetic resonance T2 mapping allows for the quantification of water and proteoglycan content within tissues and can be used to detect early cartilage abnormalities as well as to track the response to therapy. The goal of the present study was to use T2 mapping to quantify intervertebral disk water content according to the Pfirrmann classification. This study involved 60 subjects who underwent lumbar magnetic resonance imaging (a total of 300 lumbar disks). The degree of disk degeneration was assessed in the midsagittal section on T2-weighted images according to the Pfirrmann classification (grades I to V). Receiver operating characteristic (ROC) analysis was performed among grades to determine the cut-off values. In the nucleus pulposus, T2 values tended to decrease with increasing grade, and there was a significant difference in T2 values between each grade from grades I to IV. However, there was no significant difference in T2 values in the anterior or posterior annulus fibrosus. T2 values according to disk degeneration level classification were as follows: grade I (>116.8ms), grade II (92.7-116.7ms), grade III (72.1-92.6ms), grade IV (<72.0ms). T2 values decreased with increasing Pfirrmann classification grade in the nucleus pulposus, likely reflecting a decrease in proteoglycan and water content. Thus, T2 value-based measurements of intervertebral disk water content may be useful for future clinical research on degenerative disk diseases.

Human intervertebral disc internal strain in compression: The effect of disc region, loading position, and degeneration

The primary function of the disc is mechanical; therefore, degenerative changes in disc mechanics and the interactions between the annulus fibrosus (AF) and nucleus pulposus (NP) in nondegenerate and degenerate discs are important to functional evaluation. The disc experiences complex loading conditions, including mechanical interactions between the pressurized NP and the surrounding fiber-reinforced AF. Our objective was to noninvasively evaluate the internal deformations of nondegenerate and degenerate human discs under axial compression with flexion, neutral, and extension positions using magnetic resonance imaging and image correlation. The side of applied bending (e.g., anterior AF in flexion) had higher tensile radial and compressive axial strains, and the opposite side of bending exhibited tensile axial strains even though the disc was loaded under axial compression. Degenerated discs exhibited higher compressive axial and tensile radial strains, which suggest that load distribution through the disc subcomponents are altered with degeneration, likely due to the depressurized NP placing more of the applied load directly on the AF. The posterior AF exhibited higher compressive axial and higher tensile radial strains than the other AF regions, and the strains were not correlated with degeneration, suggesting this region undergoes high strains throughout life, which may predispose it to failure and tears. In addition to understanding internal disc mechanics, this study provides important new data into the changes in internal strain with degeneration, data for validation of finite element models, and provides a technique and baseline data for evaluating surgical treatments.

Small Bowel Injury as a Complication of Lumbar Microdiscectomy : Case Report and Literature Review

Small bowel injury resulting from unforeseen penetration of the anterior annulus fibrosus and longitudinal ligament is a rare complication of lumbar microdiscectomy. The patient complained of abdominal tenderness and distention immediately after microdiscectomy for L4-5 and L5-S1 disc herniation. Using abdominal computed tomography, we found several foci of air overlying the anterior aspect of the vertebral body at the L5-S1 level. Segmental resection of the small bowel including small tears and primary anastomosis of the jejunum were performed. Here, we present a case of intestinal perforation after lumbar microdiscectomy and discuss technical methods to prevent this complication with a review of literature.

Clinical investigation of high-intensity zone in anterior annulus fibrosus of lumbar disc: compared with high-intensity zone in posterior annulus fibrosus

To explore the prevalence, distribution and clinical significance of high-intensity zone (HIZ) in anterior annulus fibrosus (AF) in comparison with HIZ in posterior AF of lumbar disc. According to the diagnosis and location of HIZ, 610 lumbar magnetic resonance images with entire clinical materials were divided into control group (without HIZ), anterior AF group (HIZ), posterior AF group (HIZ) and anterior & posterior (AP) AF group (HIZ). The incidence of HIZ was summarized. The clinical data, such as male/female ratio, age, and body weight, prevalence of low back pain (LBP) and distribution of HIZ, were compared and analyzed between the groups. Three hundred and fifteen cases shown no HIZ (51.6%), 95 cases presented HIZ in anterior AF (15.6%, 119 discs), 159 cases presented HIZ in posterior AF (26.1%, 189 discs) and 41 cases presented HIZs in both anterior and posterior AF (6.7%, 96 discs). There was significant difference between the prevalence of HIZ in anterior AF and that in posterior AF (P < 0.01). The male/female ratio and body weight of each groups showed no difference (P > 0.05), and the age was proved to be statistically different between four groups (P < 0.01, control group < posterior AF group < AP AF group < anterior AF group). HIZs in anterior AF often occurred at L(1,2)-L(4,5), whereas, they usually developed at L(3,4)-L(5)S(1) in posterior AF. The incidence of LBP in control group, anterior AF group, posterior AF group, AP AF group were 40.0%, 52.6%, 55.4% and 65.8%, respectively. The LBP prevalence of control group was lower than that of other three groups (P < 0.05), and the prevalence of last three groups showed no difference (P > 0.05). Compared with HIZ in posterior AF, the HIZ in anterior AF of lumbar disc has a lower prevalence, often develops in elder patients and in upper motion segments. It also indicates an obvious relation to LBP as the former.

Growth factor expression in degenerated intervertebral disc tissue. An immunohistochemical analysis of transforming growth factor beta, fibroblast growth factor and platelet-derived growth factor.

Degenerated intervertebral disc has lost its normal architecture, and there are changes both in the nuclear and annular parts of the disc. Changes in cell shape, especially in the annulus fibrosus, have been reported. During degeneration the cells become more rounded, chondrocyte-like, whereas in the normal condition annular cells are more spindle shaped. These chondrocyte-like cells, often forming clusters, affect extracellular matrix turnover. In previous studies transforming growth factor beta (TGFbeta) -1 and -2, basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) have been highlighted in herniated intervertebral disc tissue. In the present study the same growth factors are analysed immunohistochemically in degenerated intervertebral disc tissue. Disc material was obtained from 16 discs operated for painful degenerative disc disease. Discs were classified according to the Dallas Discogram Description. Different disc regions were analysed in parallel. As normal control disc tissue material from eight organ donors was used. Polyclonal antibodies against different growth factors and TGFbeta receptor type II were used, and the immunoreaction was detected by the avidin biotin complex method. All studied degenerated discs showed immunoreactivity for TGFbeta receptor type II and bFGF. Fifteen of 16 discs were immunopositive for TGFbeta-1 and -2, respectively, and none showed immunoreaction for PDGF. Immunopositivity was located in blood vessels and in disc cells. In the nucleus pulposus the immunoreaction was located almost exclusively in chondrocyte-like disc cells, whereas in the annular region this reaction was either in chondrocyte-like disc cells, often forming clusters, or in fibroblast-like disc cells. Chondrocyte-like disc cells were especially prevalent in the posterior disrupted area. In the anterior area of the annulus fibrosus the distribution was more even between these two cell types. bFGF was expressed in the anterior annulus fibrosus more often in chondrocyte-like disc cells than in fibroblast-like disc cells. Control discs showed cellular immunopositivity for only TGFbeta-1 and -2 and TGFbeta receptor type II . We suggest that growth factors create a cascade in intervertebral disc tissue, where they act and participate in cellular remodelling from the normal resting stage via disc degeneration to disc herniation.