Bone Cylinders Research Articles

The TD6.3 faunal assemblage of the Gran Dolina site (Atapuerca, Spain): a late Early Pleistocene hyena den

Ethological studies have shown that besides human groups, large-medium carnivores have bone-collecting habits. The research developed since the last half of the twentieth century has attempted to characterise the carnivore’s accumulations and to identify them in the archaeo-paleontological record. At present, we have diagnostic criteria that define the accumulations produced by hyenids (mainly, Crocuta crocuta), thereby allowing us to differentiate them from the other accumulating agents. The faunal assemblage recovered at the Early Pleistocene TD6.3 layer of the Gran Dolina site is characterised by the presence of typical elements described in hyena dens: presence of small carnivores remains, high bone breakage, low epiphysis survival and a high frequency (>30%) of specimens with carnivore induced modifications, including large amounts of digested bones. However, attritional mortality profiles, hyena’s cubs remains, mid-shaft bone cylinders or differential anatomical composition among different weight-sizes, have not been observed or are ambiguous. In addition, anthropic evidences are scarce and concentrated in the uppermost section of the layer. TD6.3 is the result of an accumulation produced by hyenas using the cave as a den, in alternation with sporadic occupations by hominin groups. TD6.3 shows that hyena fossil accumulations may present great anatomical and taxonomic variability.

Engineered, axially-vascularized osteogenic grafts from human adipose-derived cells to treat avascular necrosis of bone in a rat model.

Avascular necrosis of bone (AVN) leads to sclerosis and collapse of bone and joints. The standard of care, vascularized bone grafts, is limited by donor site morbidity and restricted availability. The aim of this study was to generate and test engineered, axially vascularized SVF cells-based bone substitutes in a rat model of AVN. SVF cells were isolated from lipoaspirates and cultured onto porous hydroxyapatite scaffolds within a perfusion-based bioreactor system for 5days. The resulting constructs were inserted into devitalized bone cylinders mimicking AVN-affected bone. A ligated vascular bundle was inserted upon subcutaneous implantation of constructs in nude rats. After 1 and 8weeks in vivo, bone formation and vascularization were analyzed. Newly-formed bone was found in 80% of SVF-seeded scaffolds after 8weeks but not in unseeded controls. Human ALU+cells in the bone structures evidenced a direct contribution of SVF cells to bone formation. A higher density of regenerative, M2 macrophages was observed in SVF-seeded constructs. In both experimental groups, devitalized bone was revitalized by vascularized tissue after 8 weeks. SVF cells-based osteogenic constructs revitalized fully necrotic bone in a challenging AVN rat model of clinically-relevant size. SVF cells contributed to accelerated initial vascularization, to bone formation and to recruitment of pro-regenerative endogenous cells. Avascular necrosis (AVN) of bone often requires surgical treatment with autologous bone grafts, which is surgically demanding and restricted by significant donor site morbidity and limited availability. This paper describes a de novo engineered axially-vascularized bone graft substitute and tests the potential to revitalize dead bone and provide efficient new bone formation in a rat model. The engineering of an osteogenic/vasculogenic construct of clinically-relevant size with stromal vascular fraction of human adipose, combined to an arteriovenous bundle is described. This construct revitalized and generated new bone tissue. This successful approach proposes a novel paradigm in the treatment of AVN, in which an engineered, vascularized osteogenic graft would be used as a germ to revitalize large volumes of necrotic bone.

A New Transalveolar Sinus Lift Procedure for Single Implant Placement: The Ebanist Technique. A Technical Description and Case Series.

Background:Nowadays, there are many techniques to compensate bone atrophies of the posterior maxilla in order to obtain an implant-supported rehabilitation.Objective:This case series describes the Ebanist technique: a sinus lift procedure to be used in case of extremely resorbed bone crests (≤3 mm) allowing simultaneous implant placement.Methods:With a dedicated cylindrical trephine bur, it is possible to harvest a cylinder of bone from a fresh mineralized frozen homologous bone block graft and to simultaneously create a trapdoor on the recipient site. The trapdoor cortical bone is detached from the sinus membrane and removed. Dental implant is placed into the graft before the grafting procedure since the cylindrical block, once inserted in the recipient area, is not able to oppose sufficient resistance to the torque needed for implant placement.Results:Second-stage surgery and following prosthetic rehabilitation were performed after 5 months. In all cases, implant stability was manually checked and no pathological symptoms or signs were recovered at any follow-up visit.Conclusion:This technique can be considered a valid procedure for implant therapy on atrophic posterior upper maxillae, when the residual bone crest is extremely resorbed.

Phase cancellation effect on broadband ultrasonic attenuation analysis for human trabecular bone assessment using a 2-D synthetic array

Quantitative ultrasound has been developed to evaluate trabecular BMD and structural integrity. The ultrasound parameters, i.e., normalized broadband attenuation (nBUA), have been widely used for bone health status. However, the reproducibility and accuracy of nBUA are influenced by the phenomena of phase cancellation. The objectives of this study have two folds, 1) to accurately investigate the effects of phase cancellation on BUA calculation using an ultra-small receiver (aperture size: 0.2 mm) in a newly developed 2-D synthetic array-system, and 2) to evaluate the effects of phase cancellation on human trabecular bones. Most energy was located within a circle with a diameter of 12.70 mm corresponding to the transmitter aperture size. The tests of ultrasound BUA and micro-CT on the trabecular bone cylinders with a diameter of 25 mm. Both phase sensitive (PS) detection and phase insensitive (PI) detections were performed. The data indicated that the average nBUA is 24.8±9.5 dB/MHz/cm and 19.2±5.5 dB/MHz/...

The chorioallantoic membrane (CAM) assay for the study of human bone regeneration: a refinement animal model for tissue engineering.

Biomaterial development for tissue engineering applications is rapidly increasing but necessitates efficacy and safety testing prior to clinical application. Current in vitro and in vivo models hold a number of limitations, including expense, lack of correlation between animal models and human outcomes and the need to perform invasive procedures on animals; hence requiring new predictive screening methods. In the present study we tested the hypothesis that the chick embryo chorioallantoic membrane (CAM) can be used as a bioreactor to culture and study the regeneration of human living bone. We extracted bone cylinders from human femoral heads, simulated an injury using a drill-hole defect, and implanted the bone on CAM or in vitro control-culture. Micro-computed tomography (μCT) was used to quantify the magnitude and location of bone volume changes followed by histological analyses to assess bone repair. CAM blood vessels were observed to infiltrate the human bone cylinder and maintain human cell viability. Histological evaluation revealed extensive extracellular matrix deposition in proximity to endochondral condensations (Sox9+) on the CAM-implanted bone cylinders, correlating with a significant increase in bone volume by μCT analysis (p < 0.01). This human-avian system offers a simple refinement model for animal research and a step towards a humanized in vivo model for tissue engineering.

Mechanical Properties of Gamma Irradiated Versus Non-Gamma Irradiated Dense Cancellous Bone

Category: Basic Sciences/Biologics Introduction/Purpose: Allograft bone is used for a myriad of purposes in the foot and ankle, not limited to: restoring bone length at an arthrodesis site, correction of an angular deformity or filling a bone defect. The processing techniques between tissue banks vary and may include gamma irradiation, use of hydrogen peroxide, ethylene oxide, or strict aseptic processing of allograft bone. The purpose of this pilot study is to determine if using gamma irradiation during processing will significantly decrease the modulus, maximum compression strain and stress and energy during static testing of dense cancellous bone. The purpose is to also determine if using gamma irradiation during processing will significantly decrease the strain energy of the allograft during dynamic testing in dense cancellous bone. Methods: Cylinders of bone were harvested from cadaveric male specimens age 18-55 with no history of skeletal disease, abnormality or trauma to the lower extremities. Bone cylinders were harvested from the femoral head, femoral condyle and proximal tibia and were separated into right and left. All right bone cylinder specimens were processed aseptically. All left bone cylinder specimens were processed using low-dose gamma irradiation (12.7-13 kGy). Following processing, 36 bone cylinder specimens underwent static testing of right (N=18, aseptic processing) versus left (N=18, low-dose gamma irradiated) in equal amounts to determine modulus, maximum compression stress and strain and energy. 36 bone cylinders underwent dynamic testing of right (N=18, aseptic processing) versus left (N=18, low dose gamma irradiated) for strain energy. Results: Static testing results demonstrated a 27% reduction in modulus (p=.18), a 26% reduction in maximum stress (p=.20), a 15% reduction in strain at maximum stress and a 37% reduction in energy (p=0.05) in the gamma irradiated specimens versus aseptically processed specimens. Energy is the area under a stress strain curve and represents the ability of a material to resist impact. Dynamic testing results include a 36% reduction in cumulative energy in gamma irradiated specimens versus aseptically processed specimens at the 1000th cycle (p=0.02), a 37% reduction at the 2500th cycle (p=0.03), and a 39% reduction at the 5000th cycle (p=0.05). Six samples in the irradiated group failed before 10,000 cycles and one sample in the aseptic group failed before 10,000 cycles. Conclusion: This pilot study confirms previous studies using cortical bone that gamma irradiation degrades the structural properties of cancellous allograft bone. Statistically significant differences in cumulative energy absorption were observed between treatment groups during dynamic testing. Energy absorption decreased by 36-39% in the gamma irradiated group. Differences in the average between the two treatment groups were observed for all static material properties, though not statistically significant: modulus, maximum stress, strain at maximum stress and energy. The most drastic difference was observed in energy, which represents the ability of allograft to plastically deform without fracturing or failing.

Effect of thermodisinfection on mechanic parameters of cancellous bone.

Revision surgery of joint replacements is increasing and raises the demand for allograft bone since restoration of bone stock is crucial for longevity of implants. Proceedings of bone grafts influence the biological and mechanic properties differently. This study examines the effect of thermodisinfection on mechanic properties of cancellous bone. Bone cylinders from both femoral heads with length 45mm were taken from twenty-three 6-8months-old piglets, thermodisinfected at 82.5°C according to bone bank guidelines and control remained native. The specimens were stored at -20°C immediately and were put into 21°C Ringer's solution for 3h before testing. Shear and pressure modulus were tested since three point bending force was examined until destruction. Statistical analysis was done with non-parametric Wilcoxon, t test and SPSS since p<0.05 was significant. Shear modulus was significantly reduced by thermodisinfection to 1.02±0.31GPa from 1.28±0.68GPa for unprocessed cancellous bone (p=0.029) since thermodisinfection reduced pressure modulus not significantly from 6.30±4.72 GPa for native specimens to 4.97±2.23 GPa and maximum bending force was 270.03±116.68N for native and 228.80±70.49N for thermodisinfected cancellous bone. Shear and pressure modulus were reduced by thermodisinfection around 20% and maximum bending force was impaired by about 15% compared with native cancellous bone since only the reduction of shear modulus reached significance. The results suggest that thermodisinfection similarly affects different mechanic properties of cancellous bone and the reduction of mechanic properties should not relevantly impair clinical use of thermodisinfected cancellous bone.

Effect of two different soft liners and thicknesses mediating stress transfer for immediately loaded 2-implant supported mandibular overdentures: A finite element analysis study

Statement of problemThe use of soft liners as female receptacles for ball attachments retaining immediately loaded implant overdenture has been recommended to enhance osseointegration and provide a shock absorbing effect. However, which liner and which thickness is still unclear. PurposeThe purpose of this finite element analysis (FEA) study was to evaluate the effect of a 2- and 4-mm thickness of thermoplastic resin (TRL) and silicone-based liners (SBL) on the displacement and stresses transmitted to immediately loaded implants retaining a mandibular overdenture. Material and methodsFour 3-dimensional (3D) FEA models of a mandibular implant overdenture retained by 2 ball attachments (2 models for each lining material with 2- or 4-mm liner thicknesses) were developed. Implants were placed in the canine regions and surrounded by a 1-mm cylinder of immature bone simulating immediate loading. A vertical and an oblique load of 150 N were applied in the right premolar molar regions. Stresses and displacement were set as output variables. ResultsReplacing the TRL by the SBL was associated with a decrease in stresses by 73% and in displacement by at least 46%. Increasing the thickness of any liner decreases stresses by 45% during vertical loading and by 25% during oblique loading and decreases displacement by 61.5% during vertical loading and by an average of 32.5% during oblique loading. None of the liners exceeded the experimental risk limits for micromotion at the bone-implant interface (50 μm). ConclusionIn immediately loaded mandibular implant overdentures, both SBL and TRL decrease the micromotion of implants and the stresses at the bone-implant interface. However, SBL is more effective. The thickness of both liners seems to play a major role in decreasing the stresses and displacement of periimplant tissues.

Biomechanical Analysis of Locking Reconstruction Plate Using Mono- or Bicortical Screws

This experimental in vitro study evaluated the influence of screw length on the mechanical properties of a locking reconstruction plate designed with locking rings inserted into plate holes. Synthetic bone cylinders with 10 mm fracture gap and seven-hole locking reconstruction plates were used. Two groups of bone-plate constructs were assembled: Group 1 – three monocortical screws on each fracture side, Group 2 - three bicortical screws on each fracture side. In each group nine bone-plate constructs were tested until failure, three each in bending, compression and torsion. In each group, 21 bone-plate constructs were tested for failure in fatigue testing, seven each for bending, compression and torsion. In all static testing no significant differences were found between G1 and G2, except ultimate moment in torsion test (G2>G1; P=0.008). Statistical analysis revealed significant differences between groups in axial compression fatigue testing (G1>G2; P<0.05) and four-point bending fatigue testing (G1<G2; P<0.05) in maximum load, minimum load, maximum moment, and minimum moment. In conclusion, screw length can affect the mechanical properties of locking reconstruction plate. Compared to bicortical screws, monocortical screws were less resistant to bending than axial compression. This must be considered when choosing implant, particularly in fractures under high axial loads.

Ceramic cement as a potential stand-alone treatment for bone fractures: An in vitro study of ceramic–bone composites

BackgroundA vertebral burst fracture (VBF) treated with vertebroplasty using a ceramic cement consists of four regions; native bone fragments, native ceramic cement, ceramic cement–trabecular bone (ceramic–bone) composite and ceramic–bone interface. Although the mechanical properties of native bone and native ceramic cements have been well investigated, the mechanical properties of ceramic–bone composite and ceramic–bone interface remain unknown. Therefore, the aim of this study was to determine the mechanical properties of ceramic–bone composites and ceramic–bone interfaces. Two types of ceramic cement, calcium aluminate (CAC) with (w/F) and without (wo/F) fiber reinforcement, were investigated. MethodsCeramic–bone composite (Full, wo/F and w/F) and ceramic–bone interface (Fract, wo/F and w/F) groups were tested to determine their compressive and tensile properties. While a continuous bone cylinder was used for samples in the Full groups, each bone cylinder for the samples in the Fract groups contained a 3mm geometrical discontinuity to mimic the fracture gaps in VBFs. Two Cement groups (wo/F and w/F) and a Bone group were included in the study as controls. Micro-CT images were used to determine the bone morphological parameters, as potential predictors of the mechanical properties of Full and Fract groups. ResultsThe compressive strengths of Full and Fract groups were substantially lower than native CAC, but higher than bone. The tensile strength of the Full group was equal to bone, while the tensile strength of the Fract group was equivalent to CAC. Variable relationships between the bone morphological parameters and mechanical properties of Full and Fract groups were observed. Fiber reinforcement at an injectable level had a minimal influence on the mechanical properties. ConclusionsCAC augmentation does not provide adequate stabilization of bone fragments. The interface between bone and cement represents a weak point. The effect of cement augmentation cannot be predicted by bone morphological properties.

Evaluation of standardized porcine bone models to test primary stability of dental implants, using biomechanical tests and Micro-CT. An in vitro pilot study

Aim This study evaluated a new porcine bone model to test the primary stability of different implants, analyzing Micro-CT, insertion torque, and pull-out strength. Materials and methods Bone cylinders were prepared from porcine bone and separated into 2 groups: 10 high density bone cylinders (HDB), and 10 low density bone cylinders (LDB). Then, 3D pre-implant analyses were performed, evaluating tridimensional bone density (ratio of trabecular bone volume and total tomographic volume, BV/TV), trabecular separation; percentage of closed pores; percentage of open pores; percentage of total porosity, in 3 bone levels (L1 bone volume corresponding to the internal part of the threads; L2 corresponding to the area between 0 to 0.5 mm from the end of threads; L3 corresponding to the area between 0.5 to 1.5 mm from the end of threads). Twenty implants of two different macrostructures were inserted in the bone cylinders, and divided into 4 groups (5 implants each): Group 1, e-Fix HE implant placed in HDB cylinder; Group 2, e-Fix HE implant in LDB cylinder; Group 3, e-Fix HE Silver implant placed in HDB cylinder; Group 4, e-Fix HE Silver implant in LDB cylinder. The insertion torque was recorded and bone cylinders were re-evaluated by Micro-CT (post-implant analysis). Then a pull-out strength test was performed. Results 3D analysis showed that pre- and post-implants intragroups evaluation had statistically significant differences in Group 3 and 4, for all tomographic parameters assessed. Group 3 showed the best values for biomechanical tests (Friedman Test, p<0.05). Conclusion This methodology can produce standardized bone cylinders of high and low bone density, in which different implant designs are able to promote different effects, evidenced by biomechanical and image analysis.

Bactericidal efficacy of cold plasma in processed bone. A new approach for adjuvant therapy of medication-related osteonecrosis of the jaw?

BackgroundMedication-related osteonecrosis of the jaw is a difficult to treat side effect of antiresorptive therapy. Despite intensive efforts in the treatment of this disease, therapy continues to be prolonged, burdensome and sometimes insufficient. Since bacterial contamination of the necrotic bone is a major factor in these problems, we have examined the antibacterial effect of physical cold atmospheric pressure plasma on contaminated bone. MethodsA total of 72 cortico-cancellous porcine bone cylinders were processed and incubated in Streptococcus mitis broth and afterwards treated with cold atmospheric plasma, chlorhexidine or sodium chloride solution (control). After grinding up the specimens, the bacteria were transferred to aqueous solution and a colony-forming unit count was performed. ResultsPhysical cold atmospheric pressure plasma showed the best results in terms of reduction in colony-forming unit count in porcine bone: overall median in colony-forming unit/ml was significantly below that for chlorhexidine (p=0.004) and control (p=0.008). ConclusionThese results suggest that cold atmospheric pressure plasma has profound effectiveness on the bacterially contaminated bone in vitro. The use on cancellous bone is possibly a promising technique and could be a useful tool in the therapeutic range for the treatment of medication-related osteonecrosis of the jaw.

3D Porous Architecture of Stacks of β-TCP Granules Compared with That of Trabecular Bone: A microCT, Vector Analysis, and Compression Study.

The 3D arrangement of porous granular biomaterials usable to fill bone defects has received little study. Granular biomaterials occupy 3D space when packed together in a manner that creates a porosity suitable for the invasion of vascular and bone cells. Granules of beta-tricalcium phosphate (β-TCP) were prepared with either 12.5 or 25 g of β-TCP powder in the same volume of slurry. When the granules were placed in a test tube, this produced 3D stacks with a high (HP) or low porosity (LP), respectively. Stacks of granules mimic the filling of a bone defect by a surgeon. The aim of this study was to compare the porosity of stacks of β-TCP granules with that of cores of trabecular bone. Biomechanical compression tests were done on the granules stacks. Bone cylinders were prepared from calf tibia plateau, constituted high-density (HD) blocks. Low-density (LD) blocks were harvested from aged cadaver tibias. Microcomputed tomography was used on the β-TCP granule stacks and the trabecular bone cores to determine porosity and specific surface. A vector-projection algorithm was used to image porosity employing a frontal plane image, which was constructed line by line from all images of a microCT stack. Stacks of HP granules had porosity (75.3 ± 0.4%) and fractal lacunarity (0.043 ± 0.007) intermediate between that of HD (respectively 69.1 ± 6.4%, p < 0.05 and 0.087 ± 0.045, p < 0.05) and LD bones (respectively 88.8 ± 1.57% and 0.037 ± 0.014), but exhibited a higher surface density (5.56 ± 0.11 mm2/mm3 vs. 2.06 ± 0.26 for LD, p < 0.05). LP granular arrangements created large pores coexisting with dense areas of material. Frontal plane analysis evidenced a more regular arrangement of β-TCP granules than bone trabecule. Stacks of HP granules represent a scaffold that resembles trabecular bone in its porous microarchitecture.

Cylindrical Ringbone Allograft to Restore Atrophic Implant Sites: A Pilot Study.

Atrophic or severely deficient edentulous single tooth dental implant sites require osseous augmentation before any dental implant surgery. This may be accomplished by several procedures, allowing for several months of healing in order to achieve osteogenesis. After the initial site preparation, an implant may be placed and then allowed to heal for 3-6 months before the prosthetics are placed. This entire procedure may take several months to a year to complete. With the technique described herein, these cases were treated with an allograft ring or cylinder of bone that allowed for immediate placement of an implant. The allograft augmentation and implant placement are done at the same appointment. This technique shortens treatment time and may be valuable in treatment of failed implant sites. Further study is needed to refine and improve this technique.

Mechanical Evaluation of Locking, Nonlocking, and Hybrid Plating Constructs Using a Locking Compression Plate in a Canine Synthetic Bone Model.

To evaluate the mechanical properties of locking screw placement in hybrid plating in comparison to all-locked and all nonlocked constructs. Completely randomized design. Forty-eight synthetic bone cylinders (4th generation composite Sawbones(®)) across 6 construct types (n = 8 each). An 8-hole 3.5 mm LCP was placed across a 2 mm cylinder gap to mimic an unstable fracture model. The plates were secured with all locking screws, all nonlocking screws, or a combination of locking screws and nonlocking screws in the hybrid constructs. Constructs were cyclically tested nondestructively in 4-point bending, axial compression, and torsion, and then tested to failure in torsion. The stiffness and strength of each construct were calculated and compared across construct types. Constructs with a locking screw located adjacent to the fracture gap were stiffer in bending and stronger in torsion to failure than constructs without an adjacent locking screw. Hybrid and nonlocking screw constructs more frequently failed by catastrophic breakage of the bone cylinder, compared to all locking screw constructs that failed by plastic deformation of the plate. Mechanical testing of synthetic bone model constructs shows that hybrid constructs are at least as stiff and strong as entirely nonlocked constructs, and with some screw configurations, are not statistically different from entirely locked constructs.

Regional Heterogeneity in the Configuration of the Intracortical Canals of the Femoral Shaft.

Three-dimensional (3D) characterization of cortical porosity, most of which is under 100 µm in diameter, is usually confined to measurements made in 3-4 mm diameter cylinders of bone. We used micro-computed tomography (micro-CT) scanning of entire transaxial cross sections of human proximal femoral shafts (30-35 mm diameter) to quantify regional variation in porosity within the same scan. Complete, up to 10-mm-thick, transaxial slices of femoral upper shafts from 8 female cadavers were studied (n = 3 aged 29-37 years, n = 5 aged 72-90 years). Scanning was performed using high-resolution micro-CT (8.65 µm/voxel). Micro-CT volumes (10 × 10 × 5 mm) were selected via software in the anterior, medial and lateral regions. Images were segmented with voids appearing as 3D-interconnected canals. The percent void-to-tissue volume (Vo.V/TV) and the corresponding void surface area/TV were 86-309% higher in older than younger subjects in anterior (p = 0.034), medial (p = 0.077), and lateral aspects (p = 0.034). Although not significant, void separation was reciprocally lower by 19-39%, and void diameter was 65% larger in older than younger subjects; void number tended to be 24-25% higher medially and laterally but not anteriorly. For all specimens combined, medially there was higher Vo.V/TV and void surface area/TV than anteriorly (+48%, p = 0.018; +33%, p = 0.018) and laterally (+56%, p = 0.062; +36%, p = 0.043). There is regional heterogeneity in the 3D microarchitecture of the intracortical canals of the femoral shaft. The higher void volume in advanced age appears to be due to larger, rather than more, pores. However, creation of new canals from existing canals may contribute, depending on the location. High-resolution micro-computed tomography scanning of entire bone segments enables quantification of the 3D microanatomy of the intracortical void network at multiple locations.

Using Micro-CT Derived Bone Microarchitecture to Analyze Bone Stiffness – A Case Study on Osteoporosis Rat Bone

Micro-computed tomography (Micro-CT) images can be used to quantitatively represent bone geometry through a range of computed attenuation-based parameters. Nonetheless, those parameters remain indirect indices of bone microarchitectural strength and require further computational tools to interpret bone structural stiffness and potential for mechanical failure. Finite element analysis (FEA) can be applied to measure trabecular bone stiffness and potentially predict the location of structural failure in preclinical animal models of osteoporosis, although that procedure from image segmentation of Micro-CT derived bone geometry to FEA is often challenging and computationally expensive, resulting in failure of the model to build. Notably, the selection of resolution and threshold for bone segmentation are key steps that greatly affect computational complexity and validity. In the following study, we evaluated an approach whereby Micro-CT derived grayscale attenuation and segmentation data guided the selection of trabecular bone for analysis by FEA. We further correlated those FEA results to both two- and three-dimensional bone microarchitecture from sham and ovariectomized (OVX) rats (n = 10/group). A virtual cylinder of vertebral trabecular bone 40% in length from the caudal side was selected for FEA, because Micro-CT based image analysis indicated the largest differences in microarchitecture between the two groups resided there. Bone stiffness was calculated using FEA and statistically correlated with the three-dimensional values of bone volume/tissue volume, bone mineral density, fractal dimension, trabecular separation, and trabecular bone pattern factor. Our method simplified the process for the assessment of trabecular bone stiffness by FEA from Micro-CT images and highlighted the importance of bone microarchitecture in conferring significantly increased bone quality capable of resisting failure due to increased mechanical loading.

Bone matrix vesicle-bound alkaline phosphatase for the assessment of peripheral blood admixture to human bone marrow aspirates

PurposePeripheral blood (PB) admixture should be minimized during numerical and functional, as well as cytokinetic analysis of bone marrow (BM) aspirates for research purposes. Therefore, purity assessment of the BM aspirate should be performed in advance. We investigated whether bone matrix vesicle (BMV)-bound bone alkaline phosphatase (ALP) could serve as a marker for the purity of BM aspirates. ResultsTotal ALP activity was significantly higher in BM serum (97 (176–124)U/L, median (range)) compared to PB serum (63 (52–73)U/L, p<0.001). Agarose gel electrophoresis showed a unique bone ALP fraction in BM, which was absent in PB. Native polyacrylamide gel electrophoresis revealed the high molecular weight of this fraction, corresponding with membrane-bound ALP from bone matrix vesicles (BMV), as evidenced by electron microscopy. A serial PB admixture experiment of bone cylinder supernatant samples, rich in BMV-bound ALP, confirmed the sensitivity of this proposed quality assessment method. Furthermore, a BMV ALP fraction of ≥15% is suggested as cut-off value for minimal BM quality. Moreover, the BM purity declines rapidly with larger aspirated BM volumes. ConclusionThe exclusive presence of BMV-bound ALP in BM could serve as a novel marker to assess purity of BM aspirates.

Dynamic in vitro analysis of tractile forces of the anterior cruciate ligament (ACL) transplant using patellar and semitendinosus muscle tendon: a cadaver study.

The presented biomechanical study focused on the in vitro analysis of tractile forces working on the anterior cruciate ligament (ACL) and the ACL transplants, respectively, using a semitendinosus and/or patellar tendon during a passive flexion-extension movement (150-0°). Overall, 15 fresh frozen human knee joint pairs were examined. At first during arthroscopy, the tibial insertion of the ACL was drilled using a special hollow drill. Thereby, a bone cylinder was exposed at which a dynamometer was attached to enable for direct registration of tractile forces on the ACL via the connection between ACL-dynamometer and computer. The ACL transplant was fixed at the femur using a so-called endo-button, whereas the dynamometer was attached to the tibial end of the ACL transplant. The dynamic part of the examination was performed using the knee kinemator device developed by Plitz and Wirth et al. using different preload. The curves of the tractile forces of the ACL were qualitatively homogeneous with only low force values in the middle flexion position, whereas during maximum flexion and extension the forces increased reaching a maximum in the 0° position. Also, in testing the ACL transplants a force decrease between 0 and 50° flexion was recognized with even greater forces resulting at the 150° position depending on the anterior position of the femoral drill channel for implanting the ACL transplant. The amount of pre-loading showed no influence on the form of the tractile force curve. However, by enhancing the preload to 70 N, the maximal force in the ACL transplant increased significantly. The tractile forces assessed within the ACL during passive flexion movements between 10 and 90° were not greater than the forces measured in the ACL transplants. Thus, the clinical consequence is that in the early postoperative phase passive mobilization might be performed in this motion range without putting the ACL transplant at risk for damage.

Influence of the implant drill design and sequence on temperature changes during site preparation.

The purpose of this study was to compare bone temperature changes during implant drilling with two drill designs employed in three different drilling sequences. Two implant drill designs and three drilling sequences were evaluated in vitro using artificial bone cylinders. The evaluated drills were different only in the cutting-surface length (control, 16 mm; test, 4 mm). Three drilling sequences (control A, test B1, and test B2) were evaluated with and without irrigation. Temperatures were measured with thermocouple technology. The temperature changes generated by the final drill of each sequence were recorded as the experimental results and were subjected to the Student t test. There were statistically significant differences in temperature changes when comparing the control group A with the test groups B1 (P = .001) and B2 (P = .01) during drilling without coolant. The mean temperature changes were 12.4°C, 6.5°C, and 13.7°C for groups A, B1, and B2, respectively. The Student t test showed statistically significant differences between temperature changes of the control group A and the test groups B1 (P < .01) and B2 (P < .05) during drilling with coolant. The mean temperature changes were 0.9°C, 0.7°C, and 1.9°C for groups A, B1, and B2, respectively. Reduction in length of the cutting surface of the drill may limit frictional heat. Drills with the same length of cutting surface may induce lower bone temperature changes, when considering a preliminary drilling step with a pilot drill.