A spine compression fracture is a very common form of fracture in elderly with osteoporosis. Injection of polymethyl methacrylate (PMMA) to fracture sites is a minimally invasive surgical treatment, but PMMA has considerable clinical risks. We develop a novel type thermoplastic injectable bone substitute contains the proprietary composites of synthetic ceramic bone substitute and absorbable thermoplastic polymer. We used thermoplastic biocompatible polymers Polycaproactone (PCL) to encapsulate calcium-based bone substitutes hydroxyapatite (Ca10(PO4)6(OH)2, HA) and tricalcium phosphate (TCP) to form a biodegradable injectable bone composite material. The space occupation ration PCL:HA/TCP is 1:9. After heating process, it can be injected to fracture site by specific instrument and then self-setting to immediate reinforce the vertebral body. The thermoplastic injection bone substitute can obtain good injection properties after being heated by a heater at 90˚C for three minutes, and has good anti-washout property when injected into normal saline at 37˚C. After three minutes, solidification is achieved. Mechanical properties were assessed using the material compression test system and the mechanical support close to the vertebral spongy bone. In vitro cytotoxicity MTT assay (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) was performed and no cell cytotoxicity was observed. In vivo study with three New Zealand rabbits was performed, well bone growth into bone substitute was observed and can maintain good mechanical support after three months implantation. The novel type thermoplastic injection bone substitute can achieve (a) adequate injectability and viscosity without the risk of cement leakage; (b) adequate mechanical strength for immediate reinforcement and prevent adjacent fracture; (c) adequate porosity for new bone ingrowth; (e) biodegradability. It could be developed as a new option for treating vertebral compression fractures

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

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

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

Multiple myeloma (MM) is a chronic, malignant B-cell disorder, with a less than 50% 5-year survival rate [1]. This disease is responsible for vertebral compression fractures (VCFs) in 34 to 64% of diagnosed patients [1], and at least 80% of MM patients experience pathological fractures [3]. Even though reduced DXA-derived bone mineral density (BMD) has been observed in MM patients with vertebral fractures [4], the current quantitative standard method is insufficient in MM due to the osteo-destructive bone changes. Finite-element (FE) analysis is a computational and non-destructive modeling and testing approach to determine bone strength using 3D bone models from CT images. Thus, this study aimed to assess the differences in FE-predicted critical fracture load in MM patients with and without VCFs in the thoracic and lumbar segments of the spine. Multi-detector CT (MDCT) images of two radiologically assessed MM patients (1 with VCFs and 1 without VCFs) were used to generate three-dimensional (3D) models of the whole spine. For each subject, the thoracic segments, 1 to 12 (T1-T12) and lumbar segments, 1 to 5 (L1-L5) were segmented and meshed. Heterogeneous, non-linear anisotropic material properties were applied by discretizing each vertebral segment into 10 distinct sets of materials. A compressive load was simulated by constraining the surface nodes on the inferior endplate in all directions, and a displacement load was applied on the surface nods on the superior endplate [2]. This analysis was performed using ABAQUS version 6.10 (Hibbitt, Karlsson, and Sorensen, Inc., Pawtucket, RI, USA). The MM subject with VCFs had originally experienced fractures in the T4, T5, T12, L1, and L5 segments whereas the MM subject without VCFs experienced none. The former displayed large and abrupt differences in fracture loads between adjacent vertebrae segments, unlike the latter, which exhibited progressive differences instead (no abrupt changes between adjacent vertebrae segments observed). Results from this preliminary study suggest that segments at high risk of fracture are collectively involved in an unstable network, which place the vertebral segments with high values of fracture loads (peaks) as well as the adjacent segments at risk of VCF. For instance, the high fracture load at T11 places T10, T11 and T12 at risk of fracture. Accordingly, T12 has already fractured, and T10 and T11 remain at risk. The relative changes between adjacent vertebrae segments that indicate instability (extremely high fracture load values) enables ease of identification of segments at high fracture risk. Clinicians would be able to work with pre-emptive treatment strategies in future as they can focus on more targeted therapy options at the high-risk vertebrae segments [3]

Calcium phosphate cements (CPC) are used as biocompatible and bioactive bone void fillers. Ideally, the mechanical properties of these cements should match those of the surrounding bone. The knowledge of the real mechanical properties of the material is important in the decision-making process regarding possible use of the CPCs in different anatomical sites. Although it is generally recognized that these cements are stiffer and more brittle than desired, there is a limited amount of data about the possible deformation of this class of material before failure. The focus of this study was to determine these properties of injectable CPCs. Two different types of self-setting CPCs were investigated in this study: i) hydroxyapatite (HA), that historically has been the most widely studied CPC; ii) brushite, that recently has attracted attention due to its faster resorption than that of HA in vivo. Specimens of both cement types were prepared by mixing a powder phase with a liquid phase that were left to harden in phosphate buffered saline at 37°C. Once set, the specimens underwent a quasi-static compressive test to determine the compressive strength, the elastic modulus and the maximum deformation of the two materials. The material testing machine was equipped with a digital image correlation system, which allows accurate measurement of material deformation directly on the specimen surface. Brushite was found to be significantly more stiff (+80%) and resistant (+84%) than HA. Similar findings were found for the energy needed to create a first crack on the specimen surface. However, the first crack appeared on the specimen surface at the same low deformation level (∼0.15%) independently of the type of material tested. Complete failure of both materials occurred, on average, before reaching 0.25%. It has been demonstrated that the compressive behaviour of CPCs depends on their composition and porosity [1]. One of the main reasons for the high strength and stiffness of the brushite studied here was its low porosity (∼12%). However, the maximum deformation is not positively affected by this decrease in porosity. In fact, both materials show the same brittle behaviour, i.e. they undergo comparably little deformation before they break. Under these conditions, increasing the compressive strength may not always be beneficial clinically, e.g. in the treatment of vertebral compression fractures, where the high stiffness of the bone cements used has been identified as a risk factor for adjacent-level fractures [2]. However, it is not clear whether a 20-fold higher stiffness than the trabecular bone would give a different clinical outcome than a 10-fold higher stiffness. These high-strength, high-stiffness cements may also be used as a basis for further biomaterial development, e.g. in the creation of macro-porous scaffolds, which is usually challenging due to the commonly low mechanical properties of the base CPC material

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

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

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

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).