Kmc Cheung

Age-related degeneration of lumbar intervertebral discs in rabbits revealed by deuterium oxide-assisted MRI

OBJECTIVES Intervertebral disc (IVD) degeneration is associated with a loss of disc water content and change in biochemical composition of the disc. Rabbit is a frequently used model to evaluate the efficacy of therapeutics for disc degeneration. This study addresses whether rabbits undergo age-related disc degeneration, assessed using deuterium oxide-assisted magnetic resonance imaging (MRI) of the lumbar IVDs. MATERIALS AND METHODS The lumbar spines of adolescent, adult, and aged rabbits (6-36 months) were subjected to T2-weighted/short-tau inversion recovery (STIR) MRI scan along with water-deuterium oxide (H(2)O:D(2)O) dilutions. The total and maximum H(2)O:D(2)O index (HDi) of the lumbar IVDs were determined and compared between disc levels at different ages. RESULTS Adolescent rabbit lumbar discs had similar total HDi, suggesting the hydration and biochemical composition was similar among the lumbar levels. With the use of H(2)O:D(2)O reference, the discs were shown to undergo continual decrease in signal with aging which non-calibrated measurement method could not reveal. The HDi decrease rate was higher at the caudal than cranial levels. CONCLUSION This study provided in vivo evidence of age-related progressive disc degenerative change in rabbit lumbar discs, suggesting aged rabbits can be considered as a natural disc degeneration model in disc regeneration studies. However, it is important to select proper disc levels as intra-subject controls due to different rates of degenerative changes between caudal and cranial levels.

Atypical focal cortical dysplasia in a patient with Cowden syndrome.

A macrocephalic girl presented with generalised epilepsy due to focal cortical dysplasia. She later developed multiple hamartomatous lesions and was diagnosed to have Cowden syndrome. The diagnosis was confirmed by identification of a novel frameshift mutation in the PTEN gene of the patient.

Approach-related complications of open versus thoracoscopic anterior exposures of the thoracic spine.

This article reviews the approach-related complications of open versus thoracoscopic anterior exposures of the thoracic spine and suggests possible ways to avoid them.

Cost of school scoliosis screening: a cohort analysis of 306,144 students followed until skeletal maturity

Introduction: Palliative posterior decompression and instrumentation surgeries for spinal metastasis are effective in improving quality of life by providing good pain control and neurologic improvement. Preoperative embolization is usually performed because excessive blood loss is one of the main complications during the surgery. However, none of these studies have measured the effect of embolization on intraoperative blood loss in a single operative procedure. Aim: The purpose of this study was to evaluate the effectiveness of preoperative embolization in palliative posterior decompression and instrumentation surgery for spinal metastasis. Patients and methods: Forty-five patients were included in this study. Between 2000 and 2010, the patients underwent a palliative posterior decompression and instrumentation as the primary surgery for spinal metastasis in thoracolumbar spine. Not all of the patients had bleeding diathesis. One to three vertebral levels were decompressed by laminectomy and aggressive debulking of vertebral tumor. Five to seven vertebrae were stabilized using posterior instrumentation. Preoperative embolization was carried out on 23 patients (embolization group). In the embolization group, the primary tumors were in lung (7 patients), breast (4 patients), kidney (4 patients), prostate (2 patients) and the others (6 patients). The surgeries were carried out within 3 days after the embolization. The embolic materials were gelatin sponge, polyvinyl alcohol foam and metallic coils. The other 22 patients did not have the embolization (no embolization group). In the no embolization group, the primary tumor were in lung (8 patients), prostate (3 patients), colon (3 patients), breast (2 patients), the others (6 patients). Results: Angiographyandembolizationwasperformed inall 23patients in the embolization group without causing neurologic deficit. The pain and neurologic symptoms in all 45 patients were relieved after their surgery. The average intraoperative blood loss was 520 ml (140-1380 ml) in the embolization group. This was significantly lower than 1059 ml (100-3260 ml) in the no embolization group (p\0.05). In the embolization group, the intraoperative blood loss was not correlated with tumor vascularization degree, embolization degree and time between embolization and surgery. Conclusion: The intraoperative blood loss, after preoperative embolization, was measured to be about the half of that without preoperative embolization.

Right hip adduction deficit and adolescent idiopathic scoliosis

Purpose. To determine whether right hip adduction deficit is associated with adolescent idiopathic scoliosis. Methods. 102 adolescents (mean age, 14 years) with idiopathic scoliosis were prospectively studied. Their spinal curve pattern (according to Lenkes classification), curve severity (by Cobbs angle), and hip adduction ranges of both sides were recorded. Additional factors that may affect hip adduction range including the preferred leg during standing, the presence of hip flexor tightness, and the side of the dominant leg were also assessed. Results. The mean Cobbs angle was 27°. The difference in hip adduction range between the right and left hips was 5° (p<0.05). Of 102 patients, 64 had an adduction range deficit of the right hip, 4 of the left hip, and 34 had no difference. Patients with >10° of right hip adduction deficit were associated with a higher proportion of left leg dominance than those with ≤10° of right hip adduction deficit (18% vs 4%). Conclusion. Left leg dominance may play a role in right hip adduction deficit and scoliosis.

Chemical Exchange Saturation Transfer and T2 Mapping in Subjects with Intervertebral Disk Degeneration

Introduction Intervertebral disk degeneration (IVD) on magnetic resonance imaging (MRI) is an etiological factor associated with low back pain. The (IVD) has been well acknowledged to degenerate as characterized by biochemical and morphological changes. T2 relaxation time has been suggested to be sensitive to changes in collagen and water content in cartilage and in the IVD. In the disk, the investigators have quantified chemical exchange saturation transfer (CEST) and its specificity as well as its correlation capacity for glycosaminoglycan (GAG) content (gagCEST). However, the correlation between conventional qualitative MRI assessment (T2-weighted) and quantitative MRI measurement, such as T2 and CEST, remains unknown. In this study, we aimed to investigate the association between CEST, T2 and degenerative grades in IVD using T2-weighted MRI in human subjects. Materials and Methods Total 21 subjects (8 females, 13 males; median age 34; age range: 24 to 58 years) with no prior spine surgery were recruited. Sagittal T2-weighted, CEST, and T2 MRI of the lumbar spine were obtained. All images of the lumbar spine were acquired using a 3T Achieva scanner. High-resolution T2-weighted disks were qualitatively graded according to Schneidermans classification (score range: 0 to 3). CEST and T2 maps were quantitatively assessed based on a voxel-by-voxel basis. Results A decreasing trend of CEST and T2 values with increasing grade of degeneration was noted. The mean CEST values in L3/4, L4/5 and L5/S1 discs with Schneiderman grades 0 (n = 41), 1 (n = 10), 2 (n = 7) and 3 (n = 5) were 7.17 ± 1.10%, 6.00 ± 0.83%, 2.85 ± 0.39%, and 1.84 ± 0.27%, respectively. The mean T2 values in discs with Schneiderman grades 0 (n = 41), 1 (n = 10), 2 (n = 7) and 3 (n = 5) were 109.74 ± 12.40 ms, 83.84 ± 6.19 ms, 71.70 ± 3.44 ms, and 65.16 ± 2.97 ms, respectively. Schneiderman grade was correlated with both CEST (r = -0.67, p < 0.001) and T2 (r = -0.71, p) Conclusion Our results showed that CEST and T2 decreases with increasing grade of disk degeneration and that CEST values significantly correlated with T2. Our findings propose useful quantitative imaging tools with discriminatory capacity to assess early and end-stage IVD degeneration. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared

Engineering a Multicomponent Spinal Motion Segment-Like Construct from Mesenchymal Stem Cells

Introduction The task of engineering the intervertebral disc is challenging as the complex tissue needs to integrate with the host tissue and perform its function after the implantation. The vertebrae connected to the endplates are essential to integrate with the host vertebrae tissue which had been shown by Luk et al in whole disc transplantation.1 Hence, engineering the complex tissue needs to integrate the different components of the vertebrae (VB), cartilaginous endplate (CEP), nucleus pulposus (NP), and annulus fibrosus (AF); both biologically and mechanically. In this study, the multiple component spinal motion segments were fabricated by integrating these components. The construct was then loaded in a bioreactor and supplied with mechanical and biological stimulation. The functional aspect of the fabricated endplate-like construct was evaluated by a permeability test. Materials and Methods Rabbit mesenchymal stem cells (rMSCs) were encapsulated in collagen and induced to differentiate toward osteogenic and chondrogenic lineages before fabricating trilayered osteochondral (OC) constructs as previously mentioned. To test the nutritional function of the OC construct which acts as the endplate, rabbit nucleus pulposus cells (rNPCs)-encapsulated collagen microspheres were trapped in a sealed chamber formed with the OC construct such that the nutrients have to diffuse through the OC construct to reach the inside of the chamber. Cell viability of the rNPCs was then evaluated. To fabricate the multiple component construct, a rMSCs encapsulated collagen-GAG precipitate was added in between two OC construct and placed in between the shaft of the bioreactor. Then a layer of rMSC encapsulated collagen was formed around the construct to form the AF-like lamella. Torsional loading was applied onto the construct to study its effect on cell alignment in the AF-like lamella. Finally, one to three layers of AF-like lamellae were added to the spinal motion segment construct and cultured in the bioreactor with complex loading for 14 days. Histological, ultrastructural, and mechanical evaluation was done on the construct. Results In the custom developed functionality test for nutrient transport, the rNPCs in the chamber were viable at the end of the culture showed that nutrients were able to diffuse through the OC construct. For the effect of torsional loading on cell alignment in the AF-like lamella, alignment analysis showed that the cells were aligned along a preferred axis under torsional loading compared with control group without loading. However, no collagen fibers alignment was found in this study. The multiple component construct was fabricated with each component similar to the spinal motion segment. The different components of the construct were well integrated throughout the culture and were shown by histology. Mean torsional stiffness of the constructs significantly increased as the number of rMSC encapsulated AF-like layer increased. Conclusion This study demonstrated the feasibility to engineer a spinal motion segment-like tissue with collagen and MSC. The OC constructs demonstrated its nutritional function and can be used as a vertebra-endplate construct in this model. rMSC encapsulated in collagen gel can be induced to re-orientate and align in a certain direction by applying cyclic torsional force on the tubular structure. This can be a tissue engineered model to study the effects of various strategies in functional remodeling and maturation of the intervertebral disc. Disclosure of Interest None declared Reference Luk KD, Ruan DK. Intervertebral disc transplantation: a biological approach to motion preservation. Eur Spine J 2008;17(Suppl 4):504–510

The Association of Modic Changes and MRI Phenotypes of the Lumbar Spine: A Population-Based Study

Introduction Low back pain is the worlds most disabling condition. Modic changes (MC) are associated with low back pain. These changes are spinal phenotypes that represent vertebral endplate and adjacent marrow changes on MRI. MC are classified into three main types (type I, type II, and type III) and mixed types (type I/II and II/III). Due to methodological biases in previous studies, the morphology, involvement of MC, and their association with other spinal phenotypes remain speculative. As such, the aim of this study was to evaluate the relationship of MC with other spinal MRI phenotypes in a large-scale population-based study. Materials and Methods Based on the Hong Kong Disc Degeneration Cohort of Southern Chinese, we assessed the T1- and T2-weighted MRIs of 1,604 subjects (62.4% females; mean age: 49 years) from L1 to S1. The MC assessment included the presence, type, vertical height, and axial area of MC. MC were evaluated as type I, type I/II, type II, type II/III, and type III. Types were regrouped in the analyses as “type I” (types I and I/II) and “type II” (types II and II/III). Very small MC, such as MC in only one sagittal plane, were excluded. Additional imaging phenotype findings were assessed (disc bulges/extrusions, Schmorl nodes, disc degeneration). Disc degeneration was based on the Pfirrmann classification. A degenerative disc disease (DDD) score was tabulated, which represented the global severity of disc degeneration of the lumbar spine. The lumbar spine was further stratified to upper (L1-L4) and lower (L4-S1) regions. Results The prevalence of MC was 24.7% (“type I”: 6.3%, “type II”: 15.5%). Of all MC, 77% were at L4-S1. Subjects with MC were older (mean age: 53 vs. 48 years, p < 0.001) and had higher DDD scores (p < 0.001). “Type I” MC were more common at lower lumbar levels (p = 0.021), were less likely to be located only in the anterior region (p = 0.017), and were more associated with disc bulges/extrusions (p < 0.001) in comparison to “type II” MC. MC of the lower lumbar levels were not commonly noted only in the anterior region, involved more likely only the left or right endplate and had a higher prevalence of disc bulges/extrusions and disc degeneration in comparison to upper lumbar levels (p < 0.001). Large MC (≥2/3 of the axial area) were more likely located at lower lumbar levels (83 vs. 73%, p = 0.001) and had a higher prevalence of disc bulge/extrusion (83 vs. 72%, p = 0.001) and Schmorl node at the affected level (52 vs. 39%, p < 0.001) compared with smaller MC. Conclusion Based on one of the largest population-based studies, our findings strengthen the belief that MC are clearly associated with disc pathology, such as disc degeneration, disc bulges/extrusions, and endplate abnormalities (e.g., Schmorl nodes). MC type- and level-related findings in relation to additional MRI phenotypes were also identified. This study further refines the phenotypic classification of MC, which if standardized can have immense utility in studies assessing the role of biomarkers (e.g., genetics) in relation to clinically relevant spinal changes. Acknowledgments The study has been supported by AOSpine Research Network Exchange Award. Disclosure of Interest None declared

Hif-αs Modulation of Sox9-Dependent Extracellular Matrix Production: Insight into Intervertebral Disc Cell Activity under Hypoxia

Introduction Intervertebral disc (IVD) degeneration leads to loss of mechanical function of motion segment and is attributed to deregulated extracellular matrix components in the nucleus pulposus (NP). The NP is rich in type II collagen (encoded by COL2A1) and aggrecan (encoded by AGC1), which are known to be regulated by the master chondrogenic transcription factor, Sox9.1 In situ studies of human degenerated NP illustrated a reduction of COL2A1 and absence of AGC1 expression, whereas SOX9 expression level remained high.2 This indicates that there may be other factors in the IVD that can regulate the Sox9-dependent matrix expression. Recent studies in aged rabbit IVD suggest that the abnormal NP cells may be contributed by a migration of the Sox9-expressing prechondrocytic cells from the annulus fibrosus (AF) adjacent to the endplate (EP).3, 4 Among the hypoxia inducible factor-α subunits (Hif-α), Hif-1α and Hif-2α (EPAS1) have been illustrated as important transcription factors in maintaining disc cell and matrix homeostasis, particularly in the hypoxic NP region.5-7 We hypothesized that Hif-αs may regulate the Sox9-dependent transcription of the extracellular matrix genes in response to IVD degeneration. First, we aimed at identification of Sox9 and Hif-αs co-expression in cells of non-degenerated and degenerated IVD. Second, we tested the modulatory effects of Hif-1α/Hif-2α on the expression of Col2a1 and Agc1 using Sox9-expressing mouse prechondrocytic cells as a model. Materials and Methods IVD were harvested from wild-type C57BL/6N mice at 3 and 6 month old. Disc degeneration was induced by an insertion of 25G needle into contralateral AF of 4-month old Lewis rat and discs were harvested post 2 to 4 weeks of operation. Lumbar IVD of scoliosis patients and degenerative disc disease patient were collected. All animal and human works were approved by local ethical committee. Comparative immunohistochemistry staining of Hif-1α, Hif-2α and Sox9 were studied in parrafilm sections of IVD. Luciferase-based promoter assays based on specific Col2a1 or Agc1 cis-acting elements via the overexpression for each of the HIF-α subunits and/or for Sox9 in ATDC5 cells were performed. Results Relative co-expression patterns of Hif-1α, Hif-2α and Sox9 were detected in AF, NP and EP of the mouse, rat and human IVD. Intracellular expression of Hif-1α, Hif-2α, and Sox9 were confirmed by immunofluorescence, indicating a possible role for Hif-αs-Sox9 tonic activity in the IVD. By luciferase-based promoter assay, Sox9 is demonstrated as a dominant transcription factor in the activation of transcription of Col2a1 and Agc1 in mouse chondroprogenitor cells. Overt additive transcriptional upregulation of Col2a1 and Agc1 was observed with a co-expression of HIF-1α and Sox9. Strikingly, Hif-2α inhibited the Sox9-dependent transcriptional upregulation of Col2a1 and Agc1. Conclusion Our findings indicate the presence of Hif-αs/Sox9 expressing cells in IVD. In addition, our data suggest that Hif-αs can modulate Sox9-mediated transcriptional regulation of Col2a1 and Agc1 in prechondrocytic cells, implicating a possible role of dynamic Hif-αs-Sox9 interaction in the IVD degeneration process. Further investigations of the orchestration mechanisms of Hif-αs/Sox9 in the IVD may provide insights in potential strategies to alleviate disc degeneration. Disclosure of Interest None declared References Richardson SM, Hoyland JA, Mobasheri R, Csaki C, Shakibaei M, Mobasheri A. Mesenchymal stem cells in regenerative medicine: opportunities and challenges for articular cartilage and intervertebral disc tissue engineering. J Cell Physiol 2010;222(1):23–32 Sive JI, Baird P, Jeziorsk M, Watkins A, Hoyland JA, Freemont AJ. Expression of chondrocyte markers by cells of normal and degenerate intervertebral discs. Mol Pathol 2002;55(2):91–97 Henriksson H, Thornemo M, Karlsson C, et al. Identification of cell proliferation zones, progenitor cells and a potential stem cell niche in the intervertebral disc region: a study in four species. Spine 2009;34(21):2278–2287 Henriksson HB, Svala E, Skioldebrand E, Lindahl A, Brisby H. Support of concept that migrating progenitor cells from stem cell niches contribute to normal regeneration of the adult mammal intervertebral disc: a descriptive study in the New Zealand white rabbit. Spine 2012;37(9):722–732 Rajpurohit R, Risbud MV, Ducheyne P, Vresilovic EJ, Shapiro IM. Phenotypic characteristics of the nucleus pulposus: expression of hypoxia inducing factor-1, glucose transporter-1 and MMP-2. Cell Tissue Res 2002;308(3):401–407 Risbud MV, Guttapalli A, Stokes DG, et al. Nucleus pulposus cells express HIF-1 alpha under normoxic culture conditions: a metabolic adaptation to the intervertebral disc microenvironment. J Cell Biochem 2006;98(1):152–159 Agrawal A, Gajghate S, Smith H, et al. Cited2 modulates hypoxia-inducible factor-dependent expression of vascular endothelial growth factor in nucleus pulposus cells of the rat intervertebral disc. Arthritis Rheum 2008;58(12):3798–3808

Comprehensive Analysis of MRI-Phenotypes Provides New Insights into Lumbar Disc Degeneration for Genetic Studies

Introduction For the past two decades, numerous genetic association studies addressing lumbar disc degeneration (LDD) have been performed, but few of them can be replicated. The possible reasons could be the phenotype definition of LDD was highly variable between studies and level-specific variations were not addressed. As such, this study addressed the relationship between MRI features of the discs at different lumbar levels to explore the etiology of LDD; thereby, providing new insights and measurements for genetic studies. Materials and Methods Sagittal T2-weighted MRI of the lumbar spine was assessed in a population sample of 2,952 Southern Chinese (mean age, 41.1 years; range, 15.0-65.4 years; 40.7% males; 59.3% females). Loss of disc signal intensity, disc bulges/extrusions, Schmorl nodes, high-intensity zones, and bone marrow changes were assessed on imaging. Subject demographics, environmental, and lifestyle factors were also evaluated. Pair-wised polychoric correlations between phenotypes in all five lumbar discs were performed using R v3.01 Heritability was estimated by Genome-wide Complex Trait Analysis (GCTA) using genotype data to identify phenotypes shared common genetic factors. Local regressions were performed between conditions and risk factors, such as age and body mass index, to distinguish the relationship between phenotypes and environmental factors. Phenotypes which were highly correlated and shared common genetic factors were grouped to form a new measurement. Results Analyses suggested distinct genetic etiologies for the upper (L1-L2) versus lower regions (L3-S1). Estimation of heritability showed the upper (L1-L2) and lower regions (L3-S1) of the lumbar spine shared common genetics factors, respectively; but upper and lower regions could present independent genetic features. Regression between phenotype and age denoted that age-related condition was restricted to lower regions while the upper region suggests developmental characters. By combining highly correlated MRI phenotypes in the upper and lower regions separately, two composite scores were generated: a degenerative score (DgS) (represents age-related disc changes) and a developmental score (DvS) (represents congenital variations). Conclusion Based on one of the largest population-based MRI studies of LDD, comprehensive analyses of MRI phenotypes provided new insights into its etiology. Our study proposes a novel phenotype scoring system to assess disc changes on MRI. This scoring system can be used as the basis to promote a standardization of phenotype delineation, maximizing the potential of replication and meta-analysis studies of genetic risk factors for LDD. Disclosure of Interest None declared