Wedge Deformation Research Articles

Is kyphoplasty better than vertebroplasty at restoring form and function after severe vertebral wedge fractures?

Background contextThe vertebral augmentation procedures, vertebroplasty and kyphoplasty, can relieve pain and facilitate mobilization of patients with osteoporotic vertebral fractures. Kyphoplasty also aims to restore vertebral body height before cement injection and so may be advantageous for more severe fractures. PurposeThe purpose of this study was to compare the ability of vertebroplasty and kyphoplasty to restore vertebral height, shape, and mechanical function after severe vertebral wedge fractures. Study design/settingThis is a biomechanical and radiographic study using human cadaveric spines. MethodsSeventeen pairs of thoracolumbar “motion segments” from cadavers aged 70–98 years were injured, in a two-stage process involving flexion and compression, to create severe anterior wedge fractures. One of each pair underwent vertebroplasty and the other kyphoplasty. Specimens were then compressed at 1 kN for 1 hour to allow consolidation. Radiographs were taken before and after injury, after treatment, and after consolidation. At these same time points, motion segment compressive stiffness was assessed, and intervertebral disc “stress profiles” were obtained to characterize the distribution of compressive stress on the vertebral body and neural arch. ResultsOn average, injury reduced anterior vertebral body height by 34%, increased its anterior wedge angle from 5.0° to 11.4°, reduced intradiscal (nucleus) pressure and motion segment stiffness by 96% and 44%, respectively, and increased neural arch load bearing by 57%. Kyphoplasty caused 97% of the anterior height loss to be regained immediately, although this reduced to 79% after consolidation. Equivalent gains after vertebroplasty were significantly lower: 59% and 47%, respectively (p<.001). Kyphoplasty reduced vertebral wedging more than vertebroplasty (p<.02). Intradiscal pressure, neural arch load bearing, and motion segment compressive stiffness were restored significantly toward prefracture values after both augmentation procedures, even after consolidation, but these mechanical effects were similar for kyphoplasty and vertebroplasty. ConclusionsAfter severe vertebral wedge fractures, vertebroplasty and kyphoplasty were equally effective in restoring mechanical function. However, kyphoplasty was better able to restore vertebral height and reverse wedge deformity.

Expression of macrophage elastase (MMP12) in rat tail intervertebral disc and growth plate after asymmetric loading.

ObjectivesThe aim of this study was to examine whether asymmetric loading influences macrophage elastase (MMP12) expression in different parts of a rat tail intervertebral disc and growth plate and if MMP12 expression is correlated with the severity of the deformity.MethodsA wedge deformity between the ninth and tenth tail vertebrae was produced with an Ilizarov-type mini external fixator in 45 female Wistar rats, matched for their age and weight. Three groups were created according to the degree of deformity (10°, 30° and 50°). A total of 30 discs and vertebrae were evaluated immunohistochemically for immunolocalisation of MMP12 expression, and 15 discs were analysed by western blot and zymography in order to detect pro- and active MMP12.ResultsNo MMP12 expression was detected in the nucleus pulposus. Expression of MMP12 in the annulus progressively increased from group I to groups II and III, mainly at the concave side. Many growth plate chondrocytes expressed MMP12 in the control group, less in group I and rare in groups II and III. Changes in cell phenotype and reduction of cell number were observed, together with disorganisation of matrix microstructure similar to disc degeneration. ProMMP12 was detected at the area of 54 kDa and active MMP12 at 22 kDa.ConclusionsExpression of MMP12 after application of asymmetric loading in a rat tail increased in the intervertebral disc but decreased in the growth plate and correlated with the degree of the deformity and the side of the wedged disc.Cite this article: Bone Joint Res 2014;3:273–9.

Reconsideration of the relevance of mild wedge or short vertebral height deformities across a broad age distribution.

Based on an evaluation of vertebral fracture prevalence on lateral radiographs across all age groups in a large cohort, mild or wedge-shaped vertebral body changes identified among adults should be managed as osteoporosis or at least considered as a risk factor for osteoporotic fracture, since they are rare among young subjects. Radiographic assessment of vertebral fractures is limited by the inability to distinguish mild fractures from congenital mild wedge deformities or vertebrae of short vertebral height. We attempted to quantify the expected background prevalence of these deformities by measuring vertebral fracture prevalence across all age groups in a large hospital-based retrospective Chinese cohort. We reviewed eligible lateral chest radiographs from patients admitted to Peking Union Medical College Hospital during 2011 using the Genant semiquantitative method for vertebral fracture assessment (T4-L2). We evaluated fracture prevalence among subjects by sex, 10-year age group, and fracture severity grades subjectively. We further analyzed characteristics of subjects with mild (grade I) fractures to estimate the relative contribution of congenital mild wedge deformities. A total of 10,720 subjects (5,396 men and 5,324 women) with lateral chest radiographs were evaluated. Subjects ranged in age from 0.5 to 97 years with a mean of 51.8 ± 17.4 years (men 52.8 ± 17.6 years; women 50.8 ± 17.2 years). When stratified by 10-year age groups, the prevalence of vertebral fractures was relatively low until about 40 years of age, after which prevalence increased for both genders. Fractures (13 fractures for 9 males and 6 fractures for 5 females) seen in subjects younger than 40 years of age were almost exclusively mild grade fractures. No fractures were identified in subjects younger than 20 years of age. Mild or wedge-shaped vertebral body changes on lateral radiographs are rare among young subjects, indicating that when mild vertebral deformities are found among adults, they are likely to be the product of aging and not congenital variation. Clinically, therefore, mild vertebral body changes should be managed as osteoporosis or at least considered as a risk factor for osteoporotic fracture.

Wafer damage issue study by heavy Al wire wedge bonding

Purpose – The purpose of this paper was to attempt to confirm the root cause of wafer damage issue by heavy Al wire wedge bonding and propose some permanent solutions for it. Design/methodology/approach – The infra red–optical beam-induced resistance change (IR-OBIRCH) analysis defines the position of an abnormal hotspot. A cross section and an scanning electron microscope (SEM) confirmed the wafer damage issue and its position. Based on the position of wafer damage, the wedge tool with different life and Al buildup was checked found to be on the wedge tool. Finite element analysis (FEA) modeling analysis and simulation experiment guarantee the Al buildup, and low wedge deformation thickness (WDT) can cause the wafer damage issue. Finally, design of experiment (DOE) experiments are designed to optimize wedge tool dimension and wedge-bond parameters to eliminate wafer damage issue. Findings – Wafer damage issue caused the Vpwr-OUTPUT leakage issue by IR-OBIRCH analysis. Al buildup was found on wedge tool with different life and its size gets larger along with the increase in wedge tool life. Low WDT and bigger Al buildup can cause the wafer damage. Designing new wedge tool and parameters optimization can increase WDT. Research limitations/implications – Because of the limitation of time and resources, finite element method (FEM) modeling and wedge tool dimension could not be studied more deeply. Originality/value – This paper sets an example on how to find out the root cause of wafer damage by a step-by-step analysis and put forward a quick solution accordingly for the issue.

Paleomagnetic evidence for a post‐Eocene 90° CCW rotation of internal Apennine units: A linkage with Corsica‐Sardinia rotation?

AbstractWe report on an extensive paleomagnetic study (36 sites) of the Tuscan Nappe succession from the Northern Apennines Arc, aimed to reconstruct the tectonic evolution of the internal sector of this chain. We analyzed Eocene pelagic foreland ramp deposits (Scaglia Toscana Formation) and Oligocene–lower Miocene siliciclastic turbidites (Macigno and Falterona Formations). Paleomagnetic results show that the internal sector of the Northern Apennines underwent large counterclockwise (CCW) rotations with respect to the Adria‐Africa foreland. A decrease in the rotation magnitude was observed from the southern to the northern sector of the arc (from 91 to 36°). This trend is opposite to that observed in the more external units of Northern Apennines and demonstrates that the oroclinal bending model, which has been proposed for the external units of the chain, is not appropriate to explain the evolution of the internal sector of the arc. On the basis of the observed paleomagnetic pattern, we propose a new tectonic model in which the Tuscan and Falterona‐Cervarola units in the southern area were first rotated CCW along with the Corsica‐Sardinia block during its lower Miocene rotational drifting and were later involved in the main phases of rotational emplacement and translation toward the outermost sector (Umbria domain), thus yielding the final curved shape of the Northern Apennines chain. Data from this study represent the first paleomagnetic evidence of the influence of the Corsica‐Sardinia CCW rotation in the Apennines orogenic wedge deformation, in the general framework of the geodynamic evolution of the Central Mediterranean subduction system.

Middle to Late Cenozoic tectonic events in south and central Palawan (Philippines) and their implications to the evolution of the south-eastern margin of South China Sea: Evidence from onshore structural and offshore seismic data

Using recently gathered onland structural and 2D/3D offshore seismic data in south and central Palawan (Philippines), this paper presents a new perspective in unraveling the Cenozoic tectonic history of the southeastern margin of the South China Sea. South and central Palawan are dominated by Mesozoic ophiolites (Palawan Ophiolite), distinct from the primarily continental composition of the north. These ophiolites are emplaced over syn-rift Eocene turbidites (Panas Formation) along thrust structures best preserved in the ophiolite–turbidite contact as well as within the ophiolites. Thrusting is sealed by Early Miocene (∼20 Ma) sediments of the Pagasa Formation (Isugod Formation onland), constraining the younger limit of ophiolite emplacement at end Late Oligocene (∼23 Ma). The onset of ophiolite emplacement at end Eocene is constrained by thrust-related metamorphism of the Eocene turbidites, and post-emplacement underthrusting of Late Oligocene – Early Miocene Nido Limestone. This carbonate underthrusting at end Early Miocene (∼16 Ma) is marked by the deformation of a seismic unit corresponding to the earliest members of the Early – Middle Miocene Pagasa Formation. Within this formation, a tectonic wedge was built within Middle Miocene (from ∼16 Ma to ∼12 Ma), forming a thrust-fold belt called the Pagasa Wedge. Wedge deformation is truncated by the regionally-observed Middle Miocene Unconformity (MMU ∼12 Ma). A localized, post-kinematic extension affects thrust-fold structures, the MMU, and Late Miocene to Early Pliocene carbonates (e.g. Tabon Limestone). This structural set-up suggests a continuous convergent regime affecting the southeastern margin of the South China Sea between end Eocene to end Middle Miocene. The ensuing structures including juxtaposed carbonates, turbidites and shallow marine clastics within thrust-fold belts have become ideal environments for hydrocarbon generation and accumulation. Best developed in the Northwest Borneo Trough area, the intensity of thrust-fold deformation decreases towards the northeast into offshore southwest Palawan.

Exhumation of the southern Pyrenean fold‐thrust belt (Spain) from orogenic growth to decay

The deformation and exhumation history of an orogen reflects the interactions between tectonic and surface processes. We investigate orogenic wedge deformation, erosion, and sedimentation in the Pyrenees by (a) quantifying the spatiotemporal patterns of exhumation across the southern fold‐thrust belt (FTB) with bedrock apatite fission track (AFT) thermochronology and (b) comparing the results with existing deformation, exhumation, and sedimentation chronologies. Eighteen new samples record exhumation during and after orogenesis between 90 and 10 Ma. Rocks from the range core (Axial Zone) record rapid exhumation that progresses east to west and north to south, consistent with patterns of tectonically driven uplift. Synorogenic sediments shed into piggyback basins on the southern fold‐thrust belt during mountain building retain a detrital exhumation signal from the Axial Zone. In contrast, samples from other structural positions record exhumation of the thin‐skinned Pyrenean thrust sheets, suggesting sediment burial and heating of sufficient magnitudes to reset the AFT system (&gt;~3 km). In some locations, exhumation of these fold‐thrust structures is likely an erosional response to thrust‐driven rock uplift. We identify an exhumation phase ~25–20 Ma that occurs along the central and eastern Spanish Pyrenees at the boundary between thick‐ and thin‐skinned portions of the wedge. We suggest that this distributed exhumation event records (a) a taper response in the southern orogenic wedge to sediment loading and/or (b) a shift to wetter, stormier climate conditions following convergence‐driven uplift and full topographic development. A final exhumation phase between ~20 and 10 Ma may record the excavation of the southern fold‐thrust system following base level lowering in the Ebro Basin.

Fluid pressure control on splay fault activation in accretionary prism based on the maximum strength theorem with application to the Nankai wedge

The maximum strength theorem is applied to determine the pressure conditions in accretionary wedges responsible for the activation of splay faults (SF). This theorem, based on the limit analysis developed in soil mechanics, selects among several modes of deformation the one prevailing for a given pressure distribution. It applies for frictional rock properties and for an arbitrary wedge geometry. In particular, the décollement is assumed here to be partitioned into two mechanically distinct regions, the internal region being part of the seismogenic zone. The considered modes of deformation include the activation of a thrust fold rooting on the décollement and outcropping anywhere on the topography. This mode, if close to the transition between the seismic and the aseismic region of the décollement is in competition with the SF which constitutes also a potential mode of deformation. The dominance of the various modes of deformation is presented in stability maps in the plane spanned by the pressure ratios of the two regions of the décollement (pore pressure divided by lithostatic pressure, both referenced to the sea floor). Several maps are proposed for the particular case of the Kumano transect of Nankai wedge, South-West Japan, varying the SF pressure ratio, the position of the SF root on the décollement with respect to the transition between the seismic and aseismic regions as well as the respective length of these two regions. In addition, these stability maps are suggesting various scenarios to explain the changes through time in the prevailing mode of deformation in an accretionary wedges. For the Kumano transect, three scenarios could explain the observed deactivation of the SF, one of them being the seaward migration of the décollement transition point.

Balloon Kyphoplasty Versus KIVA Vertebral Augmentation—Comparison of 2 Techniques for Osteoporotic Vertebral Body Fractures

Prospective, parallel-group, controlled comparative randomized study. This study compares the efficacy in sagittal vertebral height and wedge deformity restoration, polymethylmethacrylate cement leakage safety, and functional outcome of balloon kyphoplasty (BK) versus KIVA (a novel vertebral augmentation technique) implant for the augmentation of fresh osteoporotic vertebral body fractures. Minimally invasive vertebral augmentation procedures have been widely used to treat vertebral compression fractures caused by osteoporosis. The results of these trials are encouraging in augmenting the vertebra and reducing the wedge deformity. However, after BK, polymethylmethacrylate leakage remains common after A3.1 AO type fractures, with a frequency per vertebra into the epidural space up to 9.8% but less common (0.03%-5.6%) in A1.1 AO type fracture. KIVA is a novel percutaneous uniportal vertebral augmentation device that is designed to restore the vertebral body and reduce polymethylmethacrylate leakage. From a total 190 patients with osteoporotic fractures who were initially enrolled in this prospective randomized study, 10 patients were excluded (5 met exclusion criteria, 5 with evidence of metastasis). This study examined 82 patients (69 ± 11 yr) with 133 fractures who received KIVA and 86 patients (72 ± 9 yr) with 122 fractures that were reinforced with BK. Anterior (anterior vertebral body height ratio [AVBHr]), midline (midline vertebral body height ratio [MVBHr]), and posterior (posterior vertebral body height ratio [PVBHr]) vertebral body height ratio and Gardner segmental vertebral wedge deformity were measured preoperatively to postoperatively. New fractures were recorded at the final observation. The baseline anthropometric and roentgenographic parameters did not differ between the 2 groups. Any cement leakage was examined on plain roentgenograms and computed tomographic scan. All patients were followed for an average of 14 months (range, 13-15 mo) postoperatively. RESULTS.: At the final observation, both KIVA and BK restored significantly AVBHr, PVBHr, and MVBHr. However, only KIVA device reduced significantly the Gardner angle (P = 0.002). Residual kyphosis of more than 5° was measured significantly more (P < 0.001) in the BK than in KIVA spines. KIVA showed significantly lower (3%, χ2, P ≤ 0.05) leakage) [corrected] (paravertebral, intradiscal) rate per vertebra than BK (0.098%) in which because of intracanal leakage 2 patients developed acute paraplegia and were reoperated in emergency. New fracture rate was similar in both groups. Back pain scores (visual analogue scale), 36-Item Short Form Health Survey (Physical Function and Mental Health domains), and Oswestry Disability Index scores improved significantly in the patients of both groups. Both KIVA and BK restored in short-term similarly vertebral body height, but only KIVA restored vertebral body wedge deformity. KIVA was followed by significantly lower and harmless always extracanal leakage rate than BK. Longer observation is needed to show whether these radiological changes have any functional impact.

Clinical progression of multiple myeloma presenting as parotid gland plasmacytoma

Plasmacytomas are tumors of plasma cells which can be divided into medullary or extramedullary type depending on the site where they arise. Parotid gland plasmacytoma is rarely described entity as initial presentation of multiple myeloma [1, 2]. Here we describe a patient who had clinical progression of multiple myeloma as parotid gland plasmacytoma. To our knowledge this is the first case described in literature where parotid gland plasmacytoma presented as clinical progression of multiple myeloma since parotid plasmacytoma was discovered before the diagnosis of multiple myeloma in all previous cases [3, 4]. Our patient is a 62-year-old female who was diagnosed with IgG kappa multiple myeloma 8 years ago and was previously treated with multiple chemotherapies including thalidomide, bortezomib and VAD (vincristine–adriamycin–dexamethasone) regimen, came to hematology clinic with slowly growing, painless mass in front of her right ear from past 3 months. On examination, this swelling was firm in consistency with smooth margins, non-tender, about 2 9 2 cm in size and appeared to be originating from parotid gland. No adenopathy was noted and examination of head and neck was otherwise unremarkable. A CT scan of soft tissue of neck was performed which showed a solid mass in right parotid gland which measured 2.5 9 2.0 cm with smooth margins and normal left parotid gland. Subsequently, a right superficial parotidectomy with conservation of facial nerve was performed. Histopathologic examination revealed glandular tissue with attached fibro-connective tissue with sheets of innumerous plasma cells consistent with extramedullary plasmacytoma (Fig. 1). Immunohistochemical studies for CD138, IgG and Kappa were strongly positive and were negative for IgM, IgA and Lambda consistent with previously diagnosed IgG kappa multiple myeloma (Fig. 2). Patient’s blood tests including immunoelectrophoresis and quantitative immunoglobulins did not show any significant differences when compared to the blood tests which were conducted 7 months ago. A total body skeletal survey was performed which showed generalized osteopenia, endosteal scalloping and wedge deformities in multiple vertebrae, but there was no evidence of bony lytic lesion or any other bony progression. This patient did not undergo chemotherapy or radiotherapy after parotidectomy as there was neither biochemical nor bony progression of multiple myeloma. Multiple myeloma can be present as plasmacytoma at the time of diagnosis [4] or at the time of subsequent relapse during the course of disease. Disease recurrence is commonly seen in medullary sites, but extramedullary sites are increasingly becoming common. To our knowledge this is the first case described in literature where parotid gland plasmacytoma presented as clinical progression of multiple myeloma. This case also reiterates the importance of physical exam in patients with hematological malignancies.

Steroid-induced Paraparesis: Spinal Epidural Lipomatosis Complicated by a Wedge Deformity of the Middle Thoracic Vertebrae

Steroid therapy is commonly prescribed, although a variety of complications have been reported. Among such complications, spinal epidural lipomatosis is rare and difficult to diagnose before paraparesis occurs. The purpose of this report is to present a rare but catastrophic complication of steroid therapy. A 64-year-old woman undergoing long-term steroid therapy suffered from an osteoporotic vertebral compression fracture and was unable to walk due to paraparesis. Magnetic resonance imaging (MRI) demonstrated a D7 compression fracture and stored epidural adipose tissue between D5 and D8. After surgery, the patient was able to walk with double canes. This case indicates that long-term steroid use has the potential to induce paraparesis.

Social disadvantage, bone mineral density and vertebral wedge deformities in the Tasmanian Older Adult Cohort

The relationship between social disadvantage and bone mineral density (BMD) is complex and remains unclear; furthermore, little is known of the relationship with vertebral deformities. We observed social disadvantage to be associated with BMD for females, independent of body mass index (BMI). A lower prevalence of vertebral deformities was observed for disadvantaged males. The relationship between social disadvantage and BMD appears complex and remains unclear, and little is known about the association between social disadvantage and vertebral wedge deformities. We examined the relationship between social disadvantage, BMD and wedge deformities in older adults from the Tasmanian Older Adult Cohort. BMD and wedge deformities were measured by dual-energy X-ray absorptiometry and associations with extreme social disadvantage was examined in 1,074 randomly recruited population-based adults (51% female). Socioeconomic status was assessed by Socio-economic Indexes for Areas values derived from residential addresses using Australian Bureau of Statistics 2001 census data. Lifestyle variables were collected by self-report. Regression models were adjusted for age, BMI, dietary calcium, serum vitamin D (25(OH)D), smoking, alcohol, physical inactivity, calcium/vitamin D supplements, glucocorticoids and hormone therapy (females only). Compared with other males, socially disadvantaged males were older (65.9years versus 61.9years, p = 0.008) and consumed lower dietary calcium and alcohol (both p ≤ 0.03). Socially disadvantaged females had greater BMI (29.9 ± 5.9 versus 27.6 ± 5.3, p = 0.002) and consumed less alcohol (p = 0.003) compared with other females. Socially disadvantaged males had fewer wedge deformities compared with other males (33.3% versus 45.4%, p = 0.05). After adjustment, social disadvantage was negatively associated with hip BMD for females (p = 0.02), but not for males (p = 0.70), and showed a trend for fewer wedge deformities for males (p = 0.06) but no association for females (p = 0.85). Social disadvantage appears to be associated with BMD for females, independent of BMI and other osteoporosis risk factors. A lower prevalence of vertebral deformities was observed for males of extreme social disadvantage. Further research is required to elucidate potential mechanisms for these associations.

Applying Wedge Theory to Dynamic Rupture Modeling of Fault Junctions

Wedges, such as accretionary prisms and thin‐skinned fold‐and‐thrust belts, occur frequently in nature and can be the site of devastating earthquakes. Critical wedge theory can be applied to these settings, but this steady‐state description of wedge deformation is at odds with the periodic occurrence of earthquakes. We discuss how critical wedge theory applies to the seismic cycle, and we use elastic wedge theory to constrain realistic stress states. Our goal is to determine the rupture behavior of an earthquake in a wedge. If rupture initiates on the basal sliding surface, will it stay confined to the basal surface, or will it propagate onto a fault branch interior to the wedge? This information can significantly alter the seismic hazard in areas where fault intersections occur. We answer this question using numerical models of dynamic rupture propagation through branched geometries for which the stress state is a pivotal input parameter. We apply wedge theory to constrain the stress state, but inherent to this theory is the assumption of a weak basal fault. We investigate the role of this assumption and determine that rupture is unlikely to propagate from a weak basal fault onto a strong branch fault without the aid of a physical process such as pore fluid migration along the branch. This framework is applied to the rupture of the 2008 Wenchuan earthquake. We find that we are able to reproduce the behavior at some fault intersections, but our 2D model is not able to reproduce all the behaviors, possibly due to the oblique nature of this event.

Associations of vertebral deformities and osteoarthritis with back pain among Japanese women: the Hizen-Oshima study

SummaryWe examined the spinal distribution of the types of vertebral deformities and the associations of vertebral deformities and osteoarthritis with back pain in Japanese women. Midthoracic and upper lumbar vertebrae were more susceptible to deformity. Vertebral deformity and osteoarthritis were frequent and were associated with back pain.IntroductionVertebral fractures due to osteoporosis and osteoarthritis are both common and significant health problems in aged people. However, little is known about the descriptive epidemiology of the individual deformity types and the relative clinical impact in women in Japan.MethodsLateral radiographs were obtained from 584 Japanese women ages 40 to 89 years old. Deformities were defined as vertebral heights of more than 3 standard deviations (SDs) below the normal mean. Osteoarthritis was defined as Kellgren–Lawrence (KL) grade 2 or higher. Information on upper or low back pain during the previous month was collected by questionnaire. We compared the spinal distribution of the three types of vertebral deformities (wedge, endplate, and crush) typical of fractures and examined the associations of number and type of vertebral deformities and osteoarthritis with back pain.ResultsFifteen percent of women had at least one vertebral deformity and 74% had vertebral osteoarthritis. The prevalence of upper or low back pain was 30.1%. Deformities were most common in the midthoracic and upper lumbar regions and wedge was the frequent type, followed by endplate and crush. Multiple logistic regression analysis showed that the odds of back pain was 3.0 (95% CI 1.5–6.3) times higher for women with a single wedge deformity and 3.2 (95% CI 1.0-–0.6) times higher for women with two or more wedge deformities, compared to women with no wedge deformity. Vertebral osteoarthritis was associated with back pain (OR 1.8, 95% CI 1.1–2.9), independent of other covariates including age and deformities.ConclusionOur results in this group of Japanese women are similar to and consistent with results reported previously in other populations of Japanese and Caucasians.

Vertebral deformity arising from an accelerated “creep” mechanism

Vertebral deformities often occur in patients who recall no trauma, and display no evident fracture on radiographs. We hypothesise that vertebral deformity can occur by a gradual creep mechanism which is accelerated following minor damage. "Creep" is continuous deformation under constant load. Forty-five thoracolumbar spine motion segments were tested from cadavers aged 42-92 years. Vertebral body areal BMD was measured using DXA. Specimens were compressed at 1 kN for 30 min, while creep in each vertebral body was measured using an optical MacReflex system. After 30 min recovery, each specimen was subjected to a controlled overload event which caused minor damage to one of its vertebrae. The creep test was then repeated. Vertebral body creep was measurable in specimens with BMD <0.5 g/cm(2). Creep was greater anteriorly than posteriorly (p < 0.001), so that vertebrae gradually developed a wedge deformity. Compressive overload reduced specimen height by 2.24 mm (STD 0.77 mm), and increased vertebral body creep by 800 % (anteriorly), 1,000 % (centrally) and 600 % (posteriorly). In 34 vertebrae with complete before-and-after data, anterior wedging occurring during the 1st creep test averaged 0.07° (STD 0.17°), and in the 2nd test (after minor damage) it averaged 0.79° (STD 1.03°). The increase was highly significant (P < 0.001). Vertebral body wedging during the 2nd creep test was proportional to the severity of damage, as quantified by specimen height loss during the overload event (r (2) = 0.51, p < 0.001, n = 34). Minor damage to an old vertebral body, even if it is barely discernible on radiographs, can accelerate creep to such an extent that it makes a substantial contribution to vertebral deformity.

Miocene thrusting in the eastern Sila Massif: Implication for the evolution of the Calabria-Peloritani orogenic wedge (southern Italy)

Alpine orogens in the central Mediterranean region have revealed the concomitance of crustal extension in back-arc domain and crustal shortening in frontal domain. Quantitative data of deformation in the frontal orogenic wedges are necessary to understand how the shortening-extension pair evolves in terms of structures, orogenic transport, timing, and exhumation rate. This paper deals with kinematics and ages of the frontal thrust systems of the Calabria-Peloritani Arc (Italy) exposed in the eastern Sila Massif. We first present structural fieldwork, onshore and offshore well log data, and new apatite fission-track (AFT) thermochronology. Then, we describe the structural architecture of the studied area as an ENE-verging stacking of thrust sheets involving basement units and syn-orogenic sediments. The AFT study documents that thrust sheets entered the partial annealing zone from 18Ma to 13Ma. This Early-Middle Miocene thrusting phase was coeval with exhumation of high-pressure/low temperature metamorphic rocks in the hinterland of the orogen (Coastal Chain area), mainly driven by top-to-the-W extensional tectonics. Opposite kinematic shear senses (contractional top-to-the-E and extensional top-to-the-W) and different exhumation rates (slow in the frontal, more rapid in the hinterland) are framed in a tectonic scenario of a critically tapered orogenic wedge during the eastward retreating of the Apennine slab.

Mantle wedge deformation recorded by high-temperature peridotite fabric superposition and hydrous retrogression (Limo massif, Cabo Ortegal, NW Spain)

The Limo harzburgites constitute a hm-thick tectonic stack where extremely elongated meter-scale sheath folds occur, bearing axes parallel to the macroscopic lineation recognized across the whole complex. They can be identified as close to L-type tectonites, with a weak foliation, a well-developed stretching, and a mineral lineation defined by the mineral assemblage in equilibrium. The linear fabric is recognizable at every scale, from aerial photos to the crystallographic orientation of the harzburgite-forming minerals measured by means of the electron back-scatter diffraction technique. These rocks registered initial deformation under high-temperature and low water fugacity conditions at low stress levels in an anhydrous mantle wedge context, as it is inferred from the activity of the [100](010) slip system in olivine. Then, the ongoing eo-Variscan subduction incorporated fluid/melts from the subducting plate into the suprasubduction mantle wedge zone. The variation in the ambient physicochemical conditions led to the operation of the [001](010) slip system in olivine, indicative of lower temperature and higher water fugacity and stress levels. These changes are recorded, too, by synkinematic recrystallization of oriented chlorite. The L-type fabric of clinopyroxene points to constriction conditions during deformation. The active deformational processes continued along the subduction conduit with the thrust of the peridotites onto the high-pressure granulites of the Bacariza Formation. Posteriorly, the whole ensemble would have shared a common deformational history related to exhumation and initial amphibolitization. Subsequent deformation processes under greenschist facies conditions took place until effective continental collision during the Early Carboniferous gave rise to the Variscan orogen.

Development of an electronic medical record based intervention to improve medical care of osteoporosis

Osteoporosis is infrequently addressed during hospitalization for osteoporotic fractures. An EMR-based intervention (osteoporosis order set) was developed with physician and patient input. There was a trend toward greater calcium supplementation from July 2008 to April 2009 (s = 0.058); however, use of antiresorptives (13%) or discharge instructions for BMD testing and osteoporosis treatment (10%) remained low. Osteoporosis is infrequently addressed during hospitalization for osteoporotic fractures. The study population consisted of patients over 50 years of age. Northwestern Memorial Hospital is a tertiary care academic hospital in Chicago. This study was conducted from September 1, 2007 through June 30, 2009. Physicians reported that barriers to care comprised nonacute nature of osteoporosis, belief that osteoporosis should be addressed by the PCP, low awareness of recurrent fractures, and radiographs with terms such as "compression deformity", "wedge deformity", or "vertebral height loss" which in their opinion were not clearly indicative of vertebral fractures. An EMR-based intervention was developed with physician and patient input. Over the evaluation period, 295 fracture cases in individuals over the age of 50 years in the medicine floors were analyzed. Mean age was 72 ± 11 years; 74% were female. Sites of fracture included hip n = 78 (27%), vertebral n = 87 (30%), lower extremity n = 61 (21%), upper extremity n = 43 (15%) and pelvis n = 26 (9%). There was no increase in documentation of osteoporosis in the medical record from pre- to post-EMR implementation (p = 0.89). There was a trend toward greater calcium supplementation from July 2008 to April 2009 (p = 0.058); however, use of antiresorptives (13%) or discharge instructions for BMD testing and osteoporosis treatment (10%) remained low. An electronic medical record intervention without electronic reminders created with physician input achieves an increase in calcium supplementation but fails to increase diagnosis or treatment for osteoporosis at the time of hospitalization for a fragility fracture.

The effect of vertebroplasty on costal pain related to osteoporotic thoracic compression fractures in elderly patients.

ObjectiveTo analyze the effect of vertebroplasty on costal pain which develops following osteoporotic thoracic compression fractures (OTCFs).MethodsThe authors reviewed the medical records of 35 patients who underwent vertebral augmentation for the treatment of OTCFs over a five year period. The patients were divided into two groups: the costalgia group included patientswho had costal pain after a vertebral fracture and the non-costalgia group included patients without costalgia. To evaluate the effect of vertebroplasty on costal pain and factors related to costal pain, several factors including: vertebral body fracture type, pedicle injury, bone mineral density, the fracture level and clinical outcome were confirmed with magnetic resonance imaging and chart reviews.ResultsAmong 35 patients, ten patients (28.6%) complained of costal pain with back pain. Only five of the ten patients (50%) had improved costal pain after a vertebroplasty. In the remaining 5 patients, the costal pain was improved through the use of medication including pain killers or a costal block during the follow-up period. Although the incidence of wedge deformity in the costal group was low(10%), there was no significant relationship to the incidence of costal pain statistically. Pedicle injury, bone mineral density and the fracture level had no significant relation to costal pain.ConclusionThe patients with wedge type, OTCFs may have a low incidence of costal pain as compared to those patients with bi-concave and crush deformities. The vertebroplasty effect on costal pain may not be effective. Therefore, before doing vertebroplasty, the surgeon should advise patients of this potential outcome in those treated for OTCFs.

A new experimental material for modeling relief dynamics and interactions between tectonics and surface processes

We developed a new granular material (MatIV) to study experimentally landscape evolution in active mountain belt piedmonts. Its composition and related physical properties have been determined using empirical criteria derived from the scaling of deformation, erosion-transport and sedimentation natural processes. MatIV is a water-saturated composite material made up with 4 granular components (silica powder, glass microbeads, plastic powder and graphite) whose physical, mechanical and erosion-related properties were measured with different laboratory tests. Mechanical measurements were made on a modified Hubbert-type direct shear apparatus. Erosion-related properties were determined using an experimental set-up that allows quantifying the erosion/sedimentation budget from tilted relaxation topographies. For MatIV, we also investigated the evolution of mean erosion rates and stream power erosion law exponents in 1D as a function of slope. Our results indicate that MatIV satisfies most of the defined criteria. It deforms brittlely according to the linear Mohr-Coulomb failure criterion and localizes deformation along discrete faults. Its erosion pattern is characterized by realistic hillslope and channelized processes (slope diffusion, mass wasting, channel incision). During transport, eroded particles are sorted depending on their density and shape, which results in stratified alluvial deposits displaying lateral facies variations. To evaluate the degree of similitude between model and nature, we used a new experimental device that combines accretionary wedge deformation mechanisms and surface runoff erosion processes. Results indicate that MatIV succeeded in producing detailed morphological and sedimentological features (drainage basin, channel network, terrace, syntectonic alluvial fan). Geometric, kinematic and dynamic similarity criteria have been investigated to compare precisely model to nature. Although scaling is incomplete, it yields particularly informative orders of magnitude. With all these characteristics, MatIV appears as a very promising material to investigate experimentally a wide range of scientific questions dealing with relief dynamics and interactions between tectonics, erosion and sedimentation processes.