Abstract. Objectives. To evaluate the safety and efficacy of vertebroplasty with short segmented cement augmented pedicle screws fixation for severe osteoporotic vertebral compression fractures (OVCF) with posterior/anterior wall fractured patients. Methods. A retrospective study of 24 patients of DGOU type-4 (vertebra plana) OVCF with posterior/anterior wall fracture, were treated by vertebroplasty and short segment PMMA cement augmented pedicle screws fixation. Radiological parameters (kyphosis angle and compression ratio) and clinical parameters Visual analogue scale (VAS) and Oswestry disability index (ODI) were analysed. Results. A significant improvement was noted in VAS (preoperative, 7.90 ± 0.60; final follow-up 2.90 ± 0.54) and ODI (77.10 ± 6.96 to 21.30 ± 6.70), (P < 0.05). Neurological improvement was noted in all patients. Kyphosis corrected significantly from preoperative 23.20 ± 5.90 to 5.30 ± 1.40 postoperative with 5% (3.30 ± 2.95) loss of correction at final follow-up. Anterior vertebral height restored significantly from 55.80 ± 11.9% to 87.6 ± 13.1% postoperative with 4.5 ± 4.0% loss at final follow-up. One case had cement leakage was found, but the patient is asymptomatic. No implant-related complication was seen. No iatrogenic dural or nerve injury. Conclusions. Treatment with vertebroplasty with cement augmented screw fixation and direct decompression is a great option in treating such a complex situation in fragile age with fragile bones because. Vertebroplasty is viable option for restoring vertebral anterior column in patients who are considered as contraindications for vertebroplasty, like DGOU-4. It provides anterior support avoiding corpectomy, minimise blood loss and also duration of surgery. Addition of short segment fixation gives adequate support with less stress risers at the junctional area

Abstract. Objectives. The principle of osteoporotic vertebral compression fracture (OVCF) is fixing instability, providing anterior support, and decompression. Contraindication for vertebroplasty is anterior or posterior wall fracture. The study objectives was to evaluate the efficacy and safety of vertebroplasty with short segmented PMMA cement augmented pedicle screws for OVCF with posterior/anterior wall fracture patients. Methods. A retrospective study of 24 patients of DGOU type-4 (vertebra plana) OVCF with posterior/anterior wall fracture, were treated by vertebroplasty and short segment PMMA cement augmented pedicle screws fixation. Radiological parameters (kyphosis angle and compression ratio) and clinical parameters Visual analogue scale (VAS) and Oswestry disability index (ODI) were analysed. Results. A significant improvement was noted in VAS (preoperative, 7.90 ±0.60; final follow-up 2.90 ± 0.54) and ODI (77.10 ± 6.96 to 21.30 ± 6.70), (P < 0.05). Neurological improvement was noted in all patients. Kyphosis corrected significantly from preoperative 23.20±5.90 to 5.30±1.40 postoperative with 5% (3.30± 2.95) loss of correction at final follow-up. Anterior vertebral height restored significantly from 55.80±11.9% t0 87.6±13.1% postoperative with 4.5±4.0% loss at final follow-up. One case had cement leakage was found, but the patient is asymptomatic. No implant-related complication was seen. No iatrogenic dural or nerve injury. Conclusions. Treatment with vertebroplasty with cement augmented screw fixation and direct decompression is a great option in treating such a complex situation in fragile age with fragile bones because It provides anterior support with cementing that avoids corpectomy. Short segment fixation has less stress risers at the junctional area

Introduction. Vertebral osteoporotic fracture increases both elastic and time-dependent ('creep') deformations of the fractured vertebral body during subsequent loading. The accelerated rate of creep deformation is especially marked in central and anterior regions of the vertebral body where bone mineral density is lowest. In life, subsequent loading of damaged vertebrae may cause anterior wedging of the vertebral body which could contribute to the development of kyphotic deformity. The aim of this study was to determine whether gradual creep deformations of damaged vertebrae can be reduced by vertebroplasty. Methods. Fourteen pairs of spine specimens, each comprising three vertebrae and the intervening soft tissue, were obtained from cadavers aged 67-92 yr. Specimens were loaded in combined bending and compression until one of the vertebral bodies was damaged. Damaged vertebrae were then augmented so that one of each pair underwent vertebroplasty with polymethylmethacrylate cement, the other with a resin (Cortoss). A 1kN compressive force was applied for 1 hr before fracture, after fracture, and after vertebroplasty, while creep deformation was measured in anterior, middle and posterior regions of each vertebral body, using a MacReflex optical tracking system. Results. Cement type had little influence on creep deformation, so data from all 28 specimens were pooled. After fracture, creep in the anterior vertebral body increased from 4,513 (STD 4766) to 54,107 (STD 54,845) microstrains (P<0.001), and creep in the central region of the vertebral body increased from 885 (STD 5,169) to 34,378 (STD 40,762) microstrain (P<0.001). (10,000 microstrains = 1% deformation.) Following vertebroplasty, creep deformations were reduced by 61% (P=0.002) and 66% (P=0.006) in anterior and central regions respectively. Conclusion. Creep deformations of the anterior and central regions of vertebral bodies increase markedly as a result of fracture but are then reduced by vertebroplasty. In life, vertebroplasty could help to slow or prevent the gradual development of kyphotic deformity following vertebral osteoporotic fracture, as well as increase vertebral stiffness and strength

Background. Fracture of an osteoporotic vertebral body reduces vertebral stiffness and decompresses the nucleus in the adjacent intervertebral disc. This leads to high compressive stresses acting on the annulus and neural arch. Altered load-sharing at the fractured level may influence loading of neighbouring vertebrae, increasing the risk of a fracture ‘cascade’. Vertebroplasty has been shown to normalise load-bearing by fractured vertebrae but it may increase the risk of adjacent level fracture. The aim of this study was to determine the effects of fracture and subsequent vertebroplasty on the loading of neighbouring (non-augmented) vertebrae. Methods. Fourteen pairs of three-vertebra cadaver spine specimens (67-92 yr) were loaded to induce fracture. One of each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Specimens were then creep loaded at 1.0kN for 1hr. In 17 specimens where the upper or lower vertebra fractured, compressive stress distributions were measured in the disc between adjacent non-fractured vertebrae by pulling a pressure transducer through the disc whilst under 1.0kN load. These ‘stress profiles’ were obtained at each stage of the experiment (in flexion and extension) in order to quantify intradiscal pressure (IDP), the size of stress concentrations in the posterior annulus (SP) and compressive load-bearing by anterior (FA) and posterior (FP) halves of the vertebral body and by the neural arch (FN). Results. No differences were found between Cortoss and PMMA so all data were pooled. Following fracture, IDP fell by 26% in extension (P=0.004) and SP increased by more than 200% in flexion (P=0.01). FA decreased from 55% to 36% of the applied load in flexion (P=0.002) and from 36% to 27% in extension (P=0.002). FN increased from 17% to 31% in flexion (P=0.006) and from 22% to 37% in extension (P=0.008). Vertebroplasty reduced stress concentrations in the disc and restored load-bearing towards pre-fracture values. Conclusion. Vertebral fracture transfers compressive load from the anterior vertebral body to the posterior vertebral body and neural arch of adjacent (non-fractured) vertebrae. Vertebroplasty largely restores normal load-sharing at both the augmented and adjacent levels and in doing so may help reduce the risk of a spinal fracture cascade

Summary. Time-lapsed CT offers new opportunities to predict the risk of cement leakage and to evaluate the mechanical effects on a vertebral body by monitoring each incremental injection step in an in-vitro vertebroplasty procedure. Introduction. Vertebroplasty has been shown to reinforce weak vertebral bodies and to prophylactically reduce fracture risks. However, bone cement leakage is a major vertebroplasty related problem which can cause severe complications. Leakage risk can be minimised by injecting less cement into the vertebral body, inevitably compromising the mechanical properties of the augmented bone, as a proper endplate-to-endplate connection of the injected cement is needed to obtain a mechanical benefit. Thus the cement flow in a vertebroplasty procedure requires a better understanding. This study aimed at developing a method to monitor the cement flow in a vertebral body and its mechanical effect. Materials and Methods. Eight fresh frozen human cadaveric vertebrae were prepared for augmentation by performing a bitrans- or bipedicular approach. Following they were XTremeCT-scanned (Scanco, Switzerland) at a nominal resolution of 82µm. A custom made setup enabled to fix the vertebrae in the CT bore (Siemens Emotion6) centrically. Bone cement (Vertecem V+, Synthes GmbH, Switzerland) was injected monopedicularly via a syringe driver (Harvard Apparatus, USA). Injection forces were recorded through a load cell (Type 9211, Kistler Instrumente AG, Switzerland) placed on the driver. Either a custom PEEK cannula or a trocar was inserted into each pedicle of a vertebra to allow artifact-free CT scanning. After each milliliter of injection a CT scan of the vertebra was performed at a nominal resolution of 0.63mm. Subsequently, the CT images were resampled to the original XTremeCT image and the cement cloud was segmented. The image data were then further processed for micro finite element (microFE) modeling (FAIM, Numerics88, Canada). The models were then solved for axial stiffness and Von Mises Stress (VMS) distribution. Finally, the vertebrae underwent a biomechanical quasistatic axial compression test (Mini Bionix II 858, MTS Systems Corp., USA). Results. Endplate-to-endplate connection of the cement was reached in 4 vertebrae. The average volume needed to reach the connection was 5.0±1.2 ml. Cement leakage occurred in all vertebrae, whereby in 4 cases the cement leaked into the spine channel. Each successive cement injection step was characterised with an increase of peak injection forces (16.5±12.7N at 1ml to 70.82±21.14N at 6ml). With respect to axial stiffness the mechanical tests and the microFE models correlated well (R. 2. = 0.778). Analyzing the top 100 VMS an elevated stress concentration between the endplate and the cement was observed unless the endplate was in direct contact with the cement. Conclusion. Cement flow can be monitored precisely at each injection step using the time-lapsed CT approach. Combined with microFE modeling the mechanical properties of the augmented bone can be evaluated for different incremental cement volumes injected. Our results suggest augmenting the bone until an endplate-to-endplate connection is established as otherwise partial filling would increase the risk of failure in the trabecular bone structure. This is in close agreement to other studies

Introduction. Vertebroplasty helps to restore mechanical function to a fractured vertebra. We investigated how the distribution of injected cement benefits both fractured and neighbouring vertebrae. Methods. Nine pairs of three-vertebra cadaver spine specimens (aged 67–90 yr) were compressed to induce fracture. One of each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Specimens were then creep-loaded at 1.0kN for 1hr. Before and after vertebroplasty, compressive stiffness was determined, and stress profilometry was performed by pulling a pressure-transducer through each disc whilst under 1.0kN load. Profiles indicated intradiscal pressure (IDP) and compressive load-bearing by the neural arch (F. N. ) at both disc levels. Micro-CT was used to quantify cement fill in the anterior and posterior halves of each augmented vertebral body, and also in the region immediately adjacent to the fractured endplate. Results. Fracture reduced stiffness and IDP, and increased F. N. Following vertebroplasty, anterior fill was greater for Cortoss (30%) than PMMA (17%) (P<0.01). With Cortoss, increased posterior fill was associated with a greater restoration of IDP in the adjacent disc (P<0.05). Furthermore, specimen stiffness increased in proportion to cement fill adjacent to the fractured end-plate. With PMMA, increased anterior fill caused a greater reduction in F. N. in the non-adjacent disc (P<0.05), whereas increased posterior fill and increased fill adjacent to the fracture caused a greater restoration of IDP in the adjacent disc (P<0.05). Conclusion. Cement distribution varied between the two cements. However, increased filling immediately adjacent to the fractured endplate was linked most consistently to improved mechanical function. Conflicts of Interest. None. Source of Funding. This work was funded by Action Medical Research. Vertebroplasty materials were provided by Stryker and by Orthovita. We can confirm that this abstract has not been published previously in whole or substantial part, and the findings have not been presented previously at a national meeting

Summary Statement. There are no standardised methods for assessing the cement flow behaviour in vertebroplasty. We propose a novel methodology to help understand the interaction of cement properties on the underlying displacement of bone marrow by bone cement in porous media. Introduction. Concerns related to cement extravasation in vertebroplasty provide the motivation for the development of methodologies for assessing cements (novel and commercially available) and delivery systems. Reproducible and pathologically representative three-dimensional bone surrogates are used to understand the complex rheology underlying the two-phase flow in porous media. Patients & Methods. The bone surrogates were achieved by first developing CAD models then manufacturing the physical models through a suitable rapid prototyping technique. MicroCT 100 (Scanco Medical, Switzerland) was used to assess the variability in the model morphology (n=8). Contact angle measurements were performed on the material to compare the surface wettability to that of bone. The surrogates were filled with bone marrow substitute (Carboxymethyl cellulose 2.5 % in water, 0.4 Pa.s) then 5 ml of silicone oil (Dow Corning Corp. 200® Fluid, 60 Pa.s) was injected at a constant flow rate (3mL/min) using a syringe pump. The injection was radiographically monitored and the video sequences were captured. Experiments were repeated three times. The displacement of the syringe plunger and the force applied on the plunger were recorded. Image processing was performed on the video sequences to quantitatively describe the resulting flow patterns and calculate parameters including the time of leakage and the mean spreading distance. Results. The variability in the model morphology was very low with a strut thickness of 0.253 ± 0.010 mm and a pore spacing of 0.83 + 0.01 mm. The surface wettability was very similar between all materials with a contact angle around 65°. The measured displacement of the syringe plunger confirmed the flow rate to be constant at 3 ml/min. The peak injection pressure was 0.443 ± 0.013 MPa which is well below the reported clinical measurement of injection pressure during vertebroplasty. 1. Anterior oil leakage occurred at 34.6 ± 4.71 seconds. The oil never reached the posterior wall and the mean spreading distance at the end of the injection was 23.39 ± 1.11 mm. Discussion/Conclusion. These complex three-dimensional bone surrogates provide a clinically relevant representation of the in vivo situation in terms of geometry, porosity and permeability. They overcome limitations of previous models by being constant in terms of both porosity and geometry which is crucial to reduce the variability, render the experiments reproducible and shift the focus onto understanding the cement flow behaviour. The proposed methodology will help study cement-fluid interaction to get better representation of in vivo cement flow patterns and provide a tool for validating computational simulations. Funding was provided by the EU under the FP7 Marie Curie Action (PITN-GA-2009-238690-SPINEFX)

Introduction. Osteoporotic vertebral fractures can cause severe vertebral wedging and kyphotic deformity. This study tested the hypothesis that kyphoplasty restores vertebral height, shape and mechanical function to a greater extent than vertebroplasty following severe wedge fractures. Methods. Pairs of thoracolumbar “motion segments” from seventeen cadavers (70–97 yrs) were compressed to failure in moderate flexion and then cyclically loaded to create severe wedge deformity. One of each pair underwent vertebroplasty and the other kyphoplasty. Specimens were then creep loaded at 1.0kN for 1 hour. At each stage of the experiment the following parameters were measured: vertebral height and wedge angle from radiographs, motion segment compressive stiffness, and stress distributions within the intervertebral discs. The latter indicated intra-discal pressure (IDP) and neural arch load-bearing (F. N. ). Results. Fracture and cyclic loading reduced anterior vertebral height by 34%, increased wedge angle from 5.0° to 11.4°, increased F. N. by 58% and reduced IDP and compressive stiffness by 96% and 44% respectively. Kyphoplasty restored anterior height to a greater extent than vertebroplasty (p<0.001), by 96% versus 59% immediately after augmentation, and by 79% versus 47% after subsequent creep loading. Wedge angle was also reduced to a greater extent following kyphoplasty than vertebroplasty (p<0.02) by 7.2° vs 4.2° after augmentation and 6.6° vs 4.0° after creep loading. IDP, F. N. and compressive stiffness were restored to a similar extent by both procedures. Conclusion. Kyphoplasty and vertebroplasty were equally effective in restoring mechanical function following severe wedge fractures, but kyphoplasty was better able to correct deformity by restoring vertebral height and reducing wedging. No conflicts of interest. Sources of funding: Funding was provided by a Royal College of Surgeons of England Research Fellowship and the Gloucestershire Arthritis Trust. Materials were provided by Medtronic and Depuy. This abstract has not been previously published in whole or substantial part nor has been presented previously at a national meeting

Vertebroplasty is a minimal invasive surgical procedure for treatment of vertebral compressive fractures, whereby cement is injected percutaneously into a vertebral body. Cement viscosity is believed to influence injectability, cement wash-out and leakage. Altering the liquid to powder ratio can affect the viscosity, level of cohesion and extent cement fill within the vertebral body and the ultimately strength and stiffness of the cement-vertebra composite. The association of these combined factors remains unclear. The aim of this study was to determine the relationship between cement viscosity and the potential augmentation of strength and stiffness in a model simulating in-vitro prophylactic vertebroplasty of osteoporotic vertebral bodies. Samples of synthetic bone (Sawbone) representing osteoporotic bone were manually injected with 1mL of calcium phosphate cement using a 11G cannulated needle. Calcium phosphate cement was produced by mixing alpha-tricalcium phosphate, calcium carbonate and hydroxyapatite with an aqueous solution of 5 wt% disodium hydrogen phosphate. Three liquid to powder ratio (LPR) representing different viscosity levels were used; i.e. 0.5mL/g (low viscosity), 0.45mL/g (medium viscosity) and 0.35mL/g (high viscosity). Cement filled samples were then placed in an oven (37oC) for 20 min and then immersed in Ringer's solution (37oC) for 3 days. Samples of synthetic bone without cement injection were used as controls. Potential for leakage and wash-out was determined using gravimetric analysis. Extent of cement fill was determined using computer tomography (CT). Samples were tested under axial compression at a rate of 1 mm/min and the strength and stiffness determined. Statistical significance against controls was determined using a one-way analysis of variance (p<0.05). Low viscosity cement showed more cement leakage (p=0.512) and increased cement wash-out after 3 days in Ringer's solution (p=0.476). Qualitative assessment of cement fill within the vertebral body using CT imaging supported the wash-out results. The strength (p<0.05-0.01) and stiffness (p<0.01) of samples significantly increased by cement injection in comparison to control, the extent of this increase was greater with increasing cement viscosity. Linear correlation analysis showed a definite association between the mechanical properties and viscosity of injected cement and was dependent on the amount of cement retained within the synthetic bone post-setting

Vertebroplasty, which is the percutaneous injection of bone cement into vertebral bodies has recently been used to treat painful osteoporotic compression fractures. Early clinical results have been encouraging, but very little is known about the consequences of augmentation with cement for the adjacent, non-augmented level. We therefore measured the overall failure, strength and structural stiffness of paired osteoporotic two-vertebra functional spine units (FSUs). One FSU of each pair was augmented with polymethyl-methacrylate bone cement in the caudal vertebra, while the other served as an untreated control. Compared with the controls, the ultimate failure load for FSUs treated by injection of cement was lower. The geometric mean treated/untreated ratio of failure load was 0.81, with 95% confidence limits from 0.70 to 0.92, (p < 0.01). There was no significant difference in overall FSU stiffness. For treated FSUs, there was a trend towards lower failure loads with increased filling with cement (r. 2. = 0.262, p = 0.13). The current practice of maximum filling with cement to restore the stiffness and strength of a vertebral body may provoke fractures in adjacent, non-augmented vertebrae. Further investigation is required to determine an optimal protocol for augmentation

Background. Percutaneous vertebroplasty (PVP) is a well established procedure with respect to improved pain and function following vertebral compression fracture. Currently, there is no consensus on the optimal cement distribution within a treated vertebral body. The aim of this study was to determine the influence of two distinct patterns of cement distribution following PVP on patient reported outcome measures up to 1 year post procedure. Methods. A retrospective study was undertaken of 42 patients consecutively undergoing PVP of up to 3 levels by a sole operator. Immediate post-procedural CT scans were analysed with VOXAR MPR software to determine cement distribution in each treated vertebrae as one of two defined patterns -“anterolateral” or “diffuse”. Patients completed an EQ-5D questionnaire pre-procedure and at 1, 2, 6 and 12 months from the procedure. Results. A 97% follow up rate of questionnaire completion was achieved for 30 patients. There were 58 treated levels with PVP performed at all levels between T6 and L5. Twelve patients had an anterolateral fill pattern and 18 patients had a diffuse fill pattern. Statistically significant improvement occurred in in all EQ-5D domains except self care at almost all timepoints in the study group. In the anterolateral group, pain was significantly improved at 1 week, 2months, 6 months and 1 year compared with only at 1 year in the diffuse group. Conclusion. PVP leads to immediate and sustained improvement in quality of life. Lateral cement placement leads to greater pain relief in the short term compared with diffuse cement filling. Conflicts of Interest. None. Source of Funding. None. This abstract has not been previously published in whole or in part; nor has it been presented previously at a national meeting

Prophylactic augmentation is meant to reinforce the vertebral body (VB), but in some cases it is suspected to actually weaken it. To elucidate the biomechanical efficacy of prophylactic augmentation, the full-field three-dimensional strain distributions were measured for the first time inside prophylactic-augmented vertebrae. Twelve thoracic porcine vertebrae were assigned to three groups: 4 were augmented with bone cement for vertebroplasty (Mendec-Spine, Tecres), 4 were treated with another bone cement for vertebroplasty (Calcemex-Spine, Tecres) while the other 4 were tested untreated as a control. Destructive tests were carried out under axial compression, in a step-wise fashion (unloaded, 5%, 10% and 15% compression). At each loading step, μCT-images were acquired. The internal strain distribution was investigated by means of DVC analysis. Some augmented specimens were stronger than the respective control, while others were weaker. In most of the specimens, the strain distribution in the elastic regime (5% compression) seemed to predict the location of the micro-damage initiation before it actually became identifiable (at 10% and 15% compression). The measured strain had the same order of magnitude for all groups. However, in the control vertebrae, the highest strain would unpredictably appear at any location inside the VB. Conversely, for both augmentation groups, the highest strains were measured in the regions adjacent to the injected cement mass, whereas the cement-interdigitated-bone was less strained. Localization of high strains and failure was consistent between specimens, but different between the two cement types: with Mendec-Spine failure the highest strains were mainly localized at mid-height and at the same level where the cement mass was localized; with Calcemex-Spine failure the highest strains were mainly cranial and caudal to the cement mass. Both the micro-CT images, and the DVC strain analysis highlighted that:. The cement mass was less strained than any other regions in the vertebra. Failure never started inside the cement mass. This can be explained with the additional stiffening and reinforcement associated with the infiltration of the cement inside the trabecular bone. The highest strains and failure were localized in the bone adjacent to the cement-bone interdigitated region. This can be explained by the strain concentration between the cement-interdigitated bone (stiffer and stronger), and the adjacent non-augmented trabecular bone. The strain maps in the elastic regime and the localization of failure was different in the augmented vertebrae, when compared to the natural controls. This suggests an alteration of the load sharing in the augmented structure where the load is mostly carried by the cement region. The different localization of failure initiation between the two augmented groups could be explained by the different mechanical properties of the two cements. This study has demonstrated the potential of DVC in measuring the internal strain and failure in prophylactic-augmented vertebrae. It has been shown that failure starts inside the augmented VB, next to the injected cement mass. This can help establishing better criteria (in terms of localization of the cement mass) in order to improve clinical protocols for vertebroplasty surgical procedures

Summary Statement. Prophylactic vertebroplasty treatment of ‘at-risk’ vertebrae may reduce fracture risk, however which areas weaken, thus providing surgical targets? Direct spatial 3D mapping of ReTm overcomes the constraints of 2D histology, and by application may provide insight into specific regional atrophy. Introduction. Insidious bone loss with age makes the skeleton fracture-prone in the rapidly expanding elderly population. Diagnosis of osteoporosis is often made after irreversible damage has occurred. There are over 300,000 new fragility fractures annually in the UK, more than 120,000 of these being vertebral compression fractures (VCF). Some VCFs cause life-altering pain, requiring surgical intervention. Vertebroplasty is a minimally invasive procedure whereby bone cement is injected into the damaged vertebral body with the aim of stabilisation and pain alleviation. However, vertebroplasty can alter the biomechanics of the spine, apparently leaving adjacent vertebrae with an increased VCF risk. Prophylactic augmentation of intact, though ‘at-risk’, vertebrae may reduce the risk of adverse effects. The question therefore arises as to which areas of a non-fractured vertebral body, structurally weakened with age, and thus should be targeted. Frequent reports of an overlap in BMD (bone mineral density) between fracture and non-fracture subjects suggest the combination of bone quantity and its ‘quality’ (microarchitectural strength) may be a more reliable fracture predictor than BMD alone. Providing a reliable method of cancellous connectivity measurement (a highly significant bone strength factor) is challenging. Traditional histological methods for microarchitectural interconnection are limited as they usually indirectly extrapolate 3D structure from thin (8 µm) 2D undecalcified sections. To address this difficulty, Aaron et al (2000) developed a novel, thick (300 µm) slicing and superficial staining procedure, whereby unstained real (not stained planar artifactual) trabecular termini (ReTm) are identified directly within their 3D context. The aim of this study was to automate a method of identifying trabecular regions of weakness in vertebral bodies from ageing spines. Patients and methods. 27 Embalmed cadaveric vertebral bodies (T10-L3) from 5 women (93.2±8.6 years) and 3 men (90±4.4 years) were scanned by µCT (micro-computerised tomography; µCT80, Scanco Medical, Switzerland, 74 µm voxel size), before plastic-embedding, slicing (300µm thick), and surface-staining with the von Kossa (2% silver nitrate) stain. The ReTm were mapped using light microscopy, recording their coordinates using the integrated stage, mapping them within nine defined sectors to demonstrate any apparent loci of structural disconnectivity that may cause weakness disproportionate to the bone loss. A transparent 3D envelope corresponding to the cortex, was constructed using code developed in-house (Matlab 7.3, Mathworks, USA), and was modulated and validated by overlay of the previous µCT scan and the coordinate data. Results. The ReTm distribution was found to be remarkably heterogeneous (p<0.05) and independent of the bone volume (p<0.05). For example, there was preliminary evidence of central endplate disconnection predominantly in the selected preparations. Discussion/Conclusion. Such automated spatial mapping of the ReTm within a 3D framework overcomes the constraints of 2D histology. By application of this new automated method, patterns of trabecular disconnection in the spine may now provide insight into specific regional atrophy, perhaps explaining why some vertebrae fracture while others with the same BMD do not, and indicating better targets for prophylactic vertebroplasty

Introduction. Polymethylmethacrylate(PMMA) bone cement has been used in joint reconstruction surgery and recently introduced for treatment of osteoporotic vertebral compression fracture. However, the use of PMMA bone cement in vertebroplasty leads to extensive bone stiffening and high rate of adjacent vertebrae fracture. Aim. The purpose of this study was to investigate the properties of PMMA bone cement augmented with collagen and assess its characteristics and relevance for the reduction of complication rate associated with vertebroplasty. Methods. Bone cement was produced using 2 types of PMMA based bone cement. Augmented groups were prepared using 40g of bone cement with 1% of rat tail liquid collagen. Mixing was conducted in controlled laboratory environment and at room temperature. The working and setting time and the mechanical properties were determined in accordance to ASTM standards for acrylic cements. The effect of ageing in simulated body fluid(SBF) on mechanical properties of these cements and the microstructure were studied. Results. Addition of collagen to bone cement has shown no marked effect on the working and setting time and produces bone cement with good injectability. The compressive strength is not affected but the modulus shows the material is less brittle than PMMA. Conclusion. Addition of liquid collagen to PMMA based bone cement does not necessarily compromise the properties of the cements and produce cement with good injectability and less brittle than PMMA based bone cement alone. However, bone cement augmented with different concentration of collagen need to be studied further in order to assess its clinical relevance especially in vertebroplasty

Balloon kyphoplasty (BKP) is a minimally invasive surgical technique used to correct kyphosis and vertebral compression fractures. BKP uses cement to fill a void created by the inflation of a balloon in a vertebra, it can be used as an alternative to vertebroplasty to reduce cement extravasation. Issues such as poor inter digitisation of the cement and the trabecular bone can arise with the BKP method. This can be due to a compacted layer created during the procedure which can cause complications post-surgery. The primary aim of this study was to investigate alternative cement application methods which could improve the mechanical strength of the bone-cement interface. Three alternative methods were investigated, and cylindrical bone-cement specimens were created for all methods (BKP and three alternatives). An important part of this study was to replicate the compacted layer created by the inflation of the balloon tamp in BKP. Synthetic trabecular bone specimens (Sawbones®, Pacific Research Laboratories, Vashon Island, Washington, USA) were pre-loaded in compression and the resultant compacted layers were found to replicate the compacted layers found in surgery. Mechanical testing was carried out with an MTS Model 858 Bionix. ®. Servohydraulic load frame using static tensile and torsion loads. Static tests revealed that two of the three alternative methods were an improvement on BKP, with a high statistical significance in relation to the mechanical performance of the bone-cement interface (P < 0.001). This data illustrates the potential to improve the standard BKP technique, in terms of bone-cement interface performance

INTRODUCTION. Over 85% of patients with multiple myeloma (MM) have bone disease, mostly affecting thoraco-lumbar vertebrae. Vertebral fractures can lead to pain and large spinal deformities requiring application of vertebroplasty (PVP). PVP could be enhanced by use of Coblation technique to remove lesions from compromised MM vertebrae prior to cement injection (C-PVP). METHODS. 28 cadaveric MM vertebrae, were initially fractured (IF) up to 75% of its original height on a testing machine, with rate of 1mm/min. Loading point was located at 25% of AP-diameter, from anterior. Two augmentation procedure groups were investigated: PVP and C-PVP. All vertebrae were augmented with 15% of PMMA cement. At the end of each injection the perceived injection force (PIF) was graded on a 5-point scale (1 very easy to 5 almost impossible). Augmented MM vertebrae were re-fractured, following the same protocol as for IF. Failure load (FL) was defined as 0.1% offset evaluated from load displacement curves. RESULTS. Mean initial FL was 2.5kN (STD=1.8kN) and 2.7kN (STD=1.8kN) for PVP and C-PVP, respectively. Mean augmented FL was 3.5kN (STD=3.1kN) and 4.2kN (STD=2.3kN)for PVP and C-PVP, respectively. Only the effect of augmentation was significant(p=0.006). Median PIF on the RIGHT side of vertebrae was 3.0 in PVP group and 2.5 in C-PVP (p=0.054). On the LEFT side it was 3.5 in PVP group and 3.0 in C-PVP (p=0.028). DISCUSSION. Results suggest that Coblation did not compromise strength of augmented MM vertebrae. The PIF was lower for C-PVP, as compared to PVP group, probably due to removal of lesion tissue

We performed a biomechanical study to compare the augmentation of isolated fractured vertebral bodies using two different bone tamps. Compression fractures were created in 21 vertebral bodies harvested from red deer after determining their initial strength and stiffness, which was then assessed after standardised bipedicular vertebral augmentation using a balloon or an expandable polymer bone tamp.

The median strength and stiffness of the balloon bone tamp group was 6.71 kN (sd 2.71) and 1.885 kN/mm (sd 0.340), respectively, versus 7.36 kN (sd 3.43) and 1.882 kN/mm (sd 0.868) in the polymer bone tamp group. The strength and stiffness tended to be greater in the polymer bone tamp group than in the balloon bone tamp group, but this difference was not statistically significant (strength p > 0.8, and stiffness p = 0.4).

Several experimental models have been used to produce intravascular fat embolism. We have developed a simple technique to induce fat embolism using corn oil emulsified with distilled water to form fatty micelles. Fat embolism was produced by intravenous administration of these fatty micelles in anaesthetised rats, causing alveolar oedema, haemorrhage and increased lung weight.

Histopathological examination revealed fatty droplets and fibrin thrombi in the lung, kidney and brain. The arteriolar lumen was filled with fatty deposits. Following fat embolism, hypoxia and hypercapnia occurred. The plasma phospholipase A₂, nitrate/nitrite, methylguidanidine and proinflammatory cytokines were significantly increased. Mass spectrometry showed that the main ingredient of corn oil was oleic acid.

This simple technique may be applied as a new animal model for the investigation of the mechanisms involved in the fat embolism syndrome.