Impacted bone stiffness measured during construction of morsellised bone samples

Impacted morsellised bone is widely used for filling bone deficiencies during revision of total hip arthroplasties. However, the physical properties and mechanical behaviour of this bone material are still not well understood. In this study we recorded the increase of stiffness in pellets of morsellised bone during their construction. The construction of bone pellets was measured stroke-by-stroke to ascertain optimal stiffness. We have derived an impact-constrained module of elasticity, which represents the dynamic resistance in the granulated bone mass to impaction. Drop level of the impaction slap hammer increases constrained bone stiffness during impaction and load. However, increasing the number of impaction strokes at the highest drop level does not improve stiffness properties; no significant increase in stiffness was achieved after five strokes on each layer of morsellised bone.     

Pressure during compaction of morsellised bone gives an increase in stiffness: an in vitro study

Morsellised bone impaction is used in joint prosthesis revision surgery to repair structural damage to the periarticular bone stock. The initial stiffness of the impacted bone is crucial for the survival of the revised hip joint. Impaction of morsellised bone in a femoral canal can cause fractures that may induce implant loosening in both femur and acetabulum. Alternative techniques to increase stiffness can therefore be of major interest. In this study we analyse whether applying a constant pressure during impaction can increase the stiffness of the morsellised bone. We constructed bone pellets by impaction with and without applying a constant pressure. The constrained stiffness and coefficient of secondary strain were determined by unidirectional load testing after construction of the pellets. A significant increase in constrained stiffness (P < 0.001) from 3.9 to 5.5 MPa and a decrease in the coefficient of secondary strain (P < 0.001) from 1.1 to 0.5 were found.     

Particle size influence in an impaction bone grafting model. Comparison of fresh-frozen and freeze-dried allografts

BackgroundImpaction bone grafting with large particles is considered as mechanically superior to smaller morsels. Interest of freeze-dried irradiated bone for impaction bone grafting has been observed with small particles. Influence of bone process on other particle sizes still needed to be assessed.Material and methodsTwenty-four osteoarthrotic femoral heads were used to prepare fresh-frozen and freeze-dried irradiated cancellous bone. Each group was divided into four batches of different particle sizes, each batch containing 18 samples. The different particle sizes were obtained with a Retsch Cross Beater Mill SK 100, Noviomagus rotating bone mills with two sizes of rasps and a Luer bone rongeur. Bone grafts were impacted in a contained cylinder. Stiffness was monitored during impaction.ResultsFreeze-dried irradiated grafts showed higher stiffness than fresh-frozen bone whatever the size of the particles. Large particles obtained with the rongeur and the large rasp from the Noviomagus bone mill were mechanically superior than small particles up to 30 impactions.InterpretationLarge particles offer better mechanical performance as a greater magnitude of force would be required to deform and break the particles. Freeze-dried irradiated bone brittleness reduces this advantage after 30 impactions. Large particles embrittlement leads to similar mechanical results as small particles at higher impaction rate. This may account for partial collapse of the graft layer in clinical situation when impaction rate is lower. This model supports the use of small particles obtained with thin rasp bone mill when freeze-dried irradiated bone for impaction bone grafting and large particles obtained with the Rongeur when fresh-frozen bone is available.     

Importance of Wet Packability of Component Particles in Pellet Formation

This work explored the importance of packability of component particles in the different wet processing steps of extrusion–spheronization and investigated different processing and formulation approaches for enhancing packing of component particles during extrusion–spheronization to produce spherical pellets with high yield and narrow size distribution. Various cross-linked polyvinyl pyrrolidone (XPVP) and lactose grades with different particle sizes were used as pelletization aid and filler in 1:3 binary powder blends. Loosely packed extrudates obtained from coarse XPVP/lactose blends possessed low cohesive strength and produced irregular shaped pellets with low yield whereas tightly packed, rigid extrudates obtained from XPVP/fine lactose grades possessed high cohesive strength and produced elongated pellets. Adjustment of spheronization tip speed to provide sufficient forces generated by the rotating frictional base plate for facilitating packing by rearrangement of component particles improved pellet quality. Double extrusion, decreasing particle size of the formulation component(s), and/or widening particle size distribution of the powder blend are approaches applicable to improve cohesiveness of moistened mass by closer packing of component particles for production of good quality pellets.     

Direct pelletization in a rotary processor controlled by torque measurements. III. Investigation of microcrystalline cellulose and lactose grade

The aim of the present study was to investigate the use of different grades of microcrystalline cellulose (MCC) and lactose in a direct pelletization process in a rotary processor. For this purpose, a mixed 2- and 3-level factorial study was performed to determine the influence of the particle size of microcrystalline cellulose (MCC), (≈60 and 105 μm) and lactose (≈30, 40, and 55 μm), as well as MCC type (Avicel and Emcocel) on the pelletization process and the physical properties of the prepared pellets. A 1∶4 mixture of MCC and lactose was applied, and granulation liquid was added until a 0.45 Nm increase in the torque of the friction plate was reached. All combinations of the 3 factors resulted in spherical pellets of a high physical strength. The particle size of MCC was found to have no marked effect on the amount of water required for agglomerate growth or on the size of the resulting pellets. An increasing particle size of lactose gave rise to more spherical pellets of a more narrow size distribution as well as higher yields. The MCC type was found to affect both the release of the model drug from the prepared pellets and the size distribution. Generally, the determined influence of the investigated factors was small, and direct pelletization in a rotary processor was found to be a robust process, insensitive to variations in the particle size and type of MCC and the particle size of lactose. Published: October 24, 2005     

Moistening Liquid-Dependent De-aggregation of Microcrystalline Cellulose and Its Impact on Pellet Formation by Extrusion–Spheronization

The wet-state particle size of microcrystalline cellulose (MCC) dispersed in different moistening liquids was characterized to elucidate the effect of moistening liquid type on the extent of MCC particle de-aggregation. Cohesive strength of moistened MCC masses was also assessed and pellet production by extrusion–spheronization attempted. MCC dispersed in alcohol or water–alcohol mixtures with higher alcohol proportions generally had larger particle sizes. Moistened mass cohesive strength decreased and poorer quality pellets were obtained when water–alcohol mixtures with higher alcohol proportions were used as the moistening liquid. MCC comprise aggregates of small sub-units held together by hydrogen bonds. As MCC particle de-aggregation involves hydrogen bond breaking, moistening liquids with lower polarity, such as water–alcohol mixtures with higher alcohol proportions, induced lesser de-aggregation and yielded MCC with larger particle sizes. When such water–alcohol mixtures were employed during extrusion–spheronization with MCC, the larger particle size of MCC and lower surface tension of the moistening liquid gave rise to moistened masses with lower cohesive strength. During pelletization, agglomerate growth by coalescence and closer packing of components by particle rearrangement would be limited. Thus, weaker, less spherical pellets with smaller size and wider size distribution were produced.     

3D non-linear analysis of the acetabular construct following impaction grafting

The study investigates the short-term behaviour of the acetabular construct following revision hip arthroplasty, carried out using the Slooff–Ling impaction grafting technique; using 3D finite element analyses. An elasto-plastic material model is used to describe the constitutive behaviour of morsellised cortico-cancellous bone (MCB) graft, since it has been shown that MCB undergoes significant plastic deformation under normal physiological loads. Based on previous experimental studies carried out by the authors and others, MCB is modelled using non-linear elasticity and Drucker Prager Cap (DPC) plasticity. Loading associated with walking, sitting down, and standing up is applied to the acetabular cup through a femoral head using smooth sliding surfaces. The analyses yield distinctive patterns of migration and rotation due to different activities. These are found to be similar to those observed in the clinical setting.     

Physical properties of peanut hull pellets

Peanut hull (peanut pods and waste materials from processing of peanuts) was pelleted through a 3/16-in. (4.76 mm) diameter die. The effect of change in moisture content (4.2-21.2%, wet basis) of the pellets (due to exposure of the pellets to low or high humidity storage environments) on physical properties were measured. Pelleting increased the bulk density of the peanut hull from 151 kg/m(3) to more than 600 kg/m(3). Bulk density, particle density and durability of the pelleted peanut hull of pellets were significantly affected by moisture content attained by the pellets during exposure to the low or high humidity environment. Air relative humidity significantly influenced the rate at which the pellets exchange moisture with the environment while air temperature did not. The values of the constants of the GAB model were obtained from moisture sorption isotherm at 25 degrees C.     

3D non-linear analysis of the acetabular construct following impaction grafting

The study investigates the short-term behaviour of the acetabular construct following revision hip arthroplasty, carried out using the Slooff-Ling impaction grafting technique; using 3D finite element analyses. An elasto-plastic material model is used to describe the constitutive behaviour of morsellised cortico-cancellous bone (MCB) graft, since it has been shown that MCB undergoes significant plastic deformation under normal physiological loads. Based on previous experimental studies carried out by the authors and others, MCB is modelled using non-linear elasticity and Drucker Prager Cap (DPC) plasticity. Loading associated with walking, sitting down, and standing up is applied to the acetabular cup through a femoral head using smooth sliding surfaces. The analyses yield distinctive patterns of migration and rotation due to different activities. These are found to be similar to those observed in the clinical setting.     

Lab and Bench-Scale Pelletization of Torrefied Wood Chips—Process Optimization and Pellet Quality

Combined torrefaction and pelletization is used to increase the fuel value of biomass by increasing its energy density and improving its handling and combustion properties. In the present study, a single-pellet press tool was used to screen for the effects of pellet die temperature, moisture content, additive addition, and the degree of torrefaction on the pelletizing properties and pellet quality, i.e., density, static friction, and pellet strength. Results were compared with pellet production using a bench-scale pelletizer. The results indicate that friction is the key factor when scaling up from single-pellet press to bench-scale pelletizer. Tuning moisture content or increasing the die temperature did not ease the pellet production of torrefied wood chips significantly. The addition of rapeseed oil as a lubricant reduced the static friction by half and stabilized pellet production; however, the pellet quality, strength, and density were negatively affected. The pellets produced from pine wood torrefied at 250 and 280 °C were shorter than pellets produced from untreated wood and their quality did not match conventional wood pellet standards. However, the heating value of the torrefied pellets was higher and the particle size distribution after grinding the pellets was more uniform compared to conventional wood pellets.     

Abrasion of suspended biofilm pellets in airlift reactors: effect of particle size

The detachment of biomass from suspended biofilm pellets in three-phase internal loop airlift reactors was investigated under non-growth conditions, and in the presence of bare carrier particles. In the experiments the size of biofilm pellets and bare carrier particles was varied. Results show that an increase in particle size drastically increases the abrasion rate caused by particle collisions. This increase is larger than predicted by conventional collision theory, which accounts for changes in collision frequency and collision impact. However, collision theory was formulated for neutrally buoyant particles which follow the liquid flow. This condition does not hold for biofilm pellets and carrier particles. The difference might therefore be caused by differences in particle responses to flow fluctuations. An empirical relationship, including this flow response, was formulated. The collision impact is also strongly affected by the roughness of a bare carrier particle: sharp and edgy particles cause much more damage than smoother ones. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 206-215, 1997.     

Influence of Starting Material Particle Size on Pellet Surface Roughness

The purpose of this study was to investigate the effect of pelletization aids, i.e., microcrystalline cellulose (MCC) and cross-linked polyvinyl pyrrolidone (XPVP), and filler, i.e., lactose, particle size on the surface roughness of pellets. Pellets were prepared from powder blends containing pelletization aid/lactose in 1:3 ratio by extrusion–spheronization. Surface roughness of pellets was assessed quantitatively and qualitatively using optical interferometry and scanning electron microscopy, respectively. Both quantitative and qualitative surface studies showed that surface roughness of pellets depended on the particle size of XPVP and lactose used in the formulation. Increase in XPVP or lactose particle size resulted in rougher pellets. Formulations containing MCC produced pellets with smoother surfaces than those containing XPVP. Furthermore, surface roughness of the resultant pellets did not appear to depend on MCC particle size. Starting material particle size was found to be a critical factor for determining the surface roughness of pellets produced by extrusion–spheronization. Smaller particles can pack well with lower peaks and valleys, resulting in pellets with smoother surfaces. Similar surface roughness of pellets containing different MCC grades could be due to the deaggregation of MCC particles into smaller subunits with more or less similar sizes during wet processing. Hence, for starting materials that deaggregate during the wet processing, pellet surface roughness is influenced by the particle size of the material upon deaggregation.     

Particle Deposition in Oral-tracheal Airway Models with Very Low Inhalation Profiles

Considerable progress has been made on modeling particle deposition in the oral-tracheal airway under some normal breathing conditions,i.e.,resting,light activity and moderate exercise.None of these standard breathing patterns correspond to very low inhalation profiles.It is known that particle deposition in the oral-tracheal airway is greatly influenced by flow and particle inlet conditions.In this work,very low inhalation flow rates are considered.Particle deposition is numerically investigated in different oral-tracheal airway models,i.e.,circular,elliptic and realistic oral-tracheal airway models.Both micro- and nano-particles that are normally present in cigarette smoke are considered.Results show that inhalation profiles greatly influence the particle deposition.Due to relatively low flow rate,for ultra-fine particles,the oral deposition is enhanced due to longer residence time in oral cavity and stronger Brownian motion.However,for larger particles,less particles deposit in the oral-tracheal airway due to the weaker impaction.The transition happens when particle size changes from 0.01 μm to 0.1 μm.The influence of the limited entrance area is shown and discussed.Under the low inhalation profiles,the highest deposition fraction could be in either circular or realistic models depending on the particle property and the geometric characteristic of oral cavity.The knowledge obtained in this study may be beneficial for the design of bionic inhaler and understanding of health effect from smoke particle on human being.     

Effect of mycelial morphology on ergothioneine production during liquid fermentation of Lentinula edodes

The morphological type of a microorganism generally influences its metabolite production. In the present study, we investigated the effects of the mycelial morphology of shiitake (Lentinula edodes) on the production of 2-mercaptohistidine trimethylbetaine (ergothioneine, ESH) during liquid fermentation. Analyses of the distribution of ESH in mycelial cells of different morphological types revealed that the ESH content of pellets obtained from the liquid fermentation media was much greater than the content in the free mycelia and clumps. The concentration of ESH in pellets on day 15 of liquid fermentation reached 0.79 mg/g dry weight (DW), which is approximately three times the concentration found in mycelia clumps (0.28 mg/g DW) and free mycelia (0.31 mg/g DW). Macroscopic image analysis of the development and morphological changes of the pellets during a liquid fermentation period of up to 25 days indicated that pellet growth showed a highly positive correlation with the increase in ESH concentration (r ² = 0.9851). A reduced agitation rate of 50 rpm for the culture medium was suitable for pellet formation and size enlargement. The results obtained in this work would be helpful in guiding the intentional manipulation of the distribution and enrichment of ESH in L. edodes through changes in liquid fermentation conditions.     

Post-irradiation thymocyte regeneration after bone marrow transplantation. II. Physical characteristics of thymocyte progenitor cells

Bone marrow cells were separated according to buoyant density, velocity sedimentation and cell surface charge. Fractionated (C3H x AKR)F1 bone marrow cells were transplanted into lethally-irradiated C3H recipients. In all fractions, the CFUs content and the capacity to restore the thymus cell population were determined. For all the physical parameters tested, the thymocyte progenitor cells show the same distribution as CFUs. The relationship between number of thymocyte progenitor cells and number of CFUs is dependent on density. Bone marrow progenitors of PHA responsive cells are of low buoyant density and show a distribution which resembles the distribution of the progenitors of Thy 1 positive cells. After transplantation of large numbers of bone marrow cells into irradiated mice, no significant change in the CFUs content of the thymus was observed.     

Characterization of the swelling of a size-exclusion gel.

The swelling of a dextran gel, Sephadex G-75, was observed in an aqueous environment at room temperature by a noninvasive technique that uses light microscopy coupled to an image analysis system via a video camera. The rate of swelling was found to follow the Tanaka and Fillmore theory, from which the overall gel diffusion coefficient was estimated as 6.3 x 10(-7) cm2/s. In addition to giving a quantitative measure of gel swelling that could be useful in the mechanical design of liquid chromatography columns, this approach provides data on wet particle size and particle size range, which is needed for the modeling of diffusional and mass transfer effects in size-exclusion chromatography. In this context, key observations are that the gel particles are nearly spherical with an elliptical shape factor of 0.98 (perfect sphere = 1) and that there is little difference between sizes of particles obtained in water, 50 mM Tris-glycine buffer (pH 10.2), and buffer containing 1 mg/mL protein. The diameter of the dry material ranged from 20 to 100 microns, while the hydrated particles had diameters of 40-350 microns. The rate of swelling is rapid, with 50% swelling occurring in about 10 s and swelling to 99% of the final wet particle size being obtained in less than 90 s.     

Bone marrow analysis of the myelodysplastic syndromes: histological and immunohistochemical features related to the evolution of overt leukemia

Bone marrow trephines from 31 patients with an initial diagnosis of myelodysplastic syndromes (MDS) were examined and analyzed histologically and immunohistochemically. In those cases terminating in overt leukemia (6/31, 19%), the number of bone marrow mast cells was significantly reduced, compared with those which did not evolve to overt leukemia. The bone marrow lymphoid cells that may participate in immunosurveillance against the proliferation of blast cells were also significantly reduced in cases terminating in overt leukemia. However, S-100 protein-positive cells, which include histiocytes and suppressor T-cells, were increased in cases terminating in overt leukemia. The results indicated that examination of the bone marrow to determine the proportions of mast cells and lymphoid cells which may be involved in host defense systems may be useful in predicting the evolution to overt leukemia in MDS. In the present series, patients with a hypocellular marrow (5/31, 16%) did not progress to overt leukemia and had a significantly lower bone marrow reticulin content, a significantly lower megakaryocyte count, a relatively higher mast cell count and a significantly higher lymphoid cell count than those with a normocellular or hypercellular marrow. These findings may reflect the initial features of MDS or, possibly, that hypocellular MDS is an independent entity with a low potential for blastic proliferation.     

Post-Irradiation Thymocyte Regeneration After Bone Marrow Transplantation Ii. Physical Characteristics of Thymocyte Progenitor Cells

Bone marrow cells were separated according to buoyant density, velocity sedimentation and cell surface charge. Fractionated (C3H × AKR)F₁ bone marrow cells were transplanted into lethally-irradiated C3H recipients. In all fractions, the CFUs content and the capacity to restore the thymus cell population were determined. For all the physical parameters tested, thymocyte progenitor cells show the same distribution as CFUs. the relationship between number of thymocyte progenitor cells and number of CFUs is dependent on density. Bone marrow progenitors of PHA responsive cells are of low buoyant density and show a distribution which resembles the distribution of the progenitors of Thy 1 positive cells. After transplantation of large numbers of bone marrow cells into irradiated mice, no significant change in the CFUs content of the thymus was observed.     

The bone behind a low areal bone mineral density: peripheral quantitative computed tomographic analysis in a woman with osteogenesis imperfecta

Areal bone mineral density (BMD) is the most widely used densitometric parameter. However, this approach makes it difficult to understand the structural basis of bone diseases, because a large number of bone properties are integrated into a single number. This is exemplified in the present case of a 27-year-old woman with osteogenesis imperfecta type I. Peripheral quantitative computed tomographic analysis at the radial metaphysis and at the radial diaphysis revealed a decreased areal BMD at both sites (z score -3.9 and -3.4, respectively). Yet, the structural basis for this decrease was different for the two locations: At the distal radius areal BMD was decreased because volumetric BMD was very low, whereas bone size was above the mean of the reference range. At the proximal radius areal BMD was decreased, because bone size was very low but volumetric BMD was above average. Bone mineral content of the radial diaphysis was very low for forearm muscle size, a finding which is compatible with Frost's hypothesis that the mechanostat setpoint is increased in osteogenesis imperfecta.     

Characteristics of mineral particles in the human bone/cartilage interface

Bone and cartilage consist of different organic matrices, which can both be mineralized by the deposition of nano-sized calcium phosphate particles. We have studied these mineral particles in the mineralized cartilage layer between bone and different types of cartilage (bone/articular cartilage, bone/intervertebral disk, and bone/growth cartilage) of individuals aged 54 years, 12 years, and 6 months. Quantitative backscattered electron imaging and scanning small-angle X-ray scattering at a synchrotron radiation source were combined with light microscopy to determine calcium content, mineral particle size and alignment, and collagen orientation, respectively. Mineralized cartilage revealed a higher calcium content than the adjacent bone (p<0.05 for all samples), whereas the highest values were found in growth cartilage. Surprisingly, we found the mineral platelet width similar for bone and mineralized cartilage, with the exception of the growth cartilage sample. The most striking result, however, was the abrupt change of mineral particle orientation at the interface between the two tissues. While the particles were aligned perpendicular to the interface in cartilage, they were oriented parallel to it in bone, reflecting the morphology of the underlying organic matrices. The tight bonding of mineralized cartilage to bone suggests a mechanical role for the interface of the two elastically different tissues, bone and cartilage.