Incidence of healed fracture in the skeletons of birds, molluscs and primates

The incidences of healed fracture in the limb bones of birds and the shells of molluscs were estimated by the examination of samples of bones and shells. The results are compared to published data on fracture incidence in molluscs and in primates and other mammals. The relationship between observed incidence of healed fracture, costs of growth and use of the skeleton, and the costs associated with its failure are discussed in terms of a theory of factors of safety.     

Chondrocyte apoptosis enhanced at the growth plate: a physeal response to a diaphyseal fracture

Post-traumatic overgrowth of growing long bones is a common clinical phenomenon in paediatric traumatology and is the result of an enhanced stimulation of the nearby growth plate after fracture. To date, the exact post-fractural reactions of the growth plate are poorly understood. The aim of this study has been to determine the impact of fracture on the frequency of chondrocyte apoptosis of the growth plate. Rats sustained a mid-diaphyseal closed fracture of the left tibia or were left untreated. All animals were killed 3, 10, 14 or 29 days after trauma. The left and right tibiae were harvested and apoptotic chondrocytes of the proximal tibial growth plate were detected by TUNEL staining. The apoptosis percentage of physeal chondrocytes was statistically compared among fractured bones, intact contra-lateral bones and control bones. The physeal apoptosis rate of the fractured bone was significantly higher than that of the contra-lateral intact bone (valid for all evaluated days) and the control bone (valid from day 10 onwards). Contra-lateral intact tibiae never showed significantly higher apoptosis rates compared with control tibiae. Thus, mid-diaphyseal fracture influences the nearby growth plate by stimulating chondrocyte programmed cell death, which is associated with cartilage resorption and bone replacement. The lack of a significant difference between the intact contra-lateral and the intact control bone suggests that fracture only has a local effect that contributes to the greater apoptosis rate of the adjacent physis.     

Specifications for machining the bovine cortical bone in relation to its microstructure

Until date, many devices have been developed for cutting human bones during orthopedic surgeries. However, bones are anisotropic material, and their machining characteristics depend on the tool feed direction. In this study, microcutting of the bovine cortical bone is performed and its structure observed under a microscope. Furthermore, the formation of cutting chips and measurement of the cutting force during bone machining are dynamically observed while considering the anisotropy of bone tissue. In particular, the fracture of secondary osteons and crack propagation in bones are observed and analyzed. The results indicate that when the cut depth exceeds 20 μm and is greater than the interval of concentric lamellae, cracks are formed together with chips. A new method for bone machining is proposed. This method is based on the characteristics of crack propagation in bones and is expected to produce low mechanical stress and realize highly efficient and precise machining of living tissues such as bones.     

Finite element analysis of acetabular fractures—development and validation with a synthetic pelvis

Acetabular fracture presents a challenging situation to trauma surgeons today due to its complexity. Finite element (FE) models can be of great help as they can improve the surgical planning and post surgery patient management for those with acetabular fractures. We have developed a non-linear finite element model of the pelvis and validated its fracture prediction capability with synthetic polyurethane pelves. A mechanical experiment was performed with the synthetic bones and fracture loads and patterns were observed for two different loading cases. Fracture loads predicted by our FE model were within one standard deviation of the experimental fracture loads for both loading cases. The incipient fracture pattern predicted by the model also resembled the actual pattern from the experiment. Although it is not a complete validation with human cadaver bones, the good agreement between model predictions and experimental results indicate the validity of our approach in using non-linear FE formulation along with contact conditions in predicting bone fractures.     

多排螺旋CT后处理技术对不规则骨骨折的诊断价值

目的:探讨多排螺旋CT及其后处理技术在诊断不规则骨骨折中的诊断价值。方法:用16排螺旋CT对25例怀疑颅骨、脊柱或关节附近骨折的外伤患儿进行扫描并进行后处理(MPR、VR)。结果:25例病例中颅骨骨折15例,脊柱骨折5例,四肢关节骨折5例(其中3例关节内骨折伴有骺软骨损伤)。结论:对于不规则骨骨折,多排螺旋CT及其后处理重建具有很大的优越性,应横断位、MPR及VR三者相结合判断,为临床提供丰富的、科学的、准确的信息依据。     

Emerging evidence that adaptive bone formation inhibition by non-steroidal anti-inflammatory drugs increases stress fracture risk

There is mounting evidence suggesting that the commonly used analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), may inhibit new bone formation with physical training and increase risk of stress fractures in physically active populations. Stress fractures are thought to occur when bones are subjected to repetitive mechanical loading, which can lead to a cycle of tissue microdamage, repair, and continued mechanical loading until fracture. Adaptive bone formation, particularly on the periosteal surface of long bones, is a concurrent adaptive response of bone to heightened mechanical loading that can improve the fatigue resistance of the skeletal structure, and therefore may play a critical role in offsetting the risk of stress fracture. Reports from animal studies suggest that NSAID administration may suppress this important adaptive response to mechanical loading. These observations have implications for populations such as endurance athletes and military recruits who are at risk of stress fracture and whose use of NSAIDs is widespread. However, results from human trials evaluating exercise and bone adaptation with NSAID consumption have been less conclusive. In this review, we identify knowledge gaps that must be addressed to further support NSAID-related guidelines intended for at-risk populations and individuals.     

Metacarpal morphometry in adults with osteogenesis imperfecta.

Osteogenesis imperfecta is often regarded as a form of osteoporosis. In many cases, particularly those in whom the first fracture occurs outside the neonatal period, bones that have not been fractured may appear radiologically normal. In a group of 24 adults with osteogenesis imperfecta the thickness of the metacarpal cortex was normal but their bones were often slender. Osteoporosis is probably not an inevitable feature of such cases, and some of the radiological abnormalities reported may be the results of previous fractures and their treatment.     

Finite element modeling for strain rate dependency of fracture resistance in compact bone

Crack growths in compact bones driven by various strain rate levels were studied using finite element modeling. The energy resistance curves in bovine femur cortical bones were characterized, whereas the orthotropic viscoelasticity in bone materials was accounted for to assess the effect of strain rate on the energy resistance curve. The models were also used to justify the anticipated plane strain response as a result of rather thick specimens used in experiments. Similarities were found between the experimental and model results when crack resistance ability exhibited in bones with slow loading rates, while unstable crack growth existed in bones with rapid loading rates. The critical energy release rates slightly decreased with the increase in strain rates. The hybrid experimental and computational method introduced in this study could be beneficial for application in fracture study in which standard experiments cannot be validly performed.     

Yeast-Incorporated Gallium Promotes Fracture Healing by Increasing Callus Bony Area and Improving Trabecular Microstructure on Ovariectomized Osteopenic Rats

The purpose of this study was to analyze the impact of yeast-incorporated gallium on fracture healing in ovariectomized osteopenic rats. Forty Wistar female rats used were divided into three groups: sham-operated rats (SHAM), ovariectomized (OVX) rats, and ovx rats treated with yeast-bound gallium (YG). A standardized fracture-healing model with stable plate fixation was established for rat femoral. After 4-week stable fixation, animals were killed to prepare bones for Micro-CT, biomechanical testing, and histomorphometry. In addition, bone samples were obtained to evaluate the content of mineral substances in bones. Quantitative analysis of the bones from animals in the organic gallium group revealed significantly increased mineral contents compared to bones from OVX and SHAM groups. Micro-CT showed that treatment with yeast-incorporated gallium increased BV/TV and trabecular thickness and decreased trabecular separation in ovx animals. Histomorphometric evaluation demonstrated that YG increased callus area and callus bone formation. Yeast-bound gallium also improved the biomechanical properties of bone healing. In conclusion, this study suggests that yeast-incorporated gallium could promote fracture healing in ovariectomized rats.     

Subject-specific finite element models implementing a maximum principal strain criterion are able to estimate failure risk and fracture location on human femurs tested in vitro

No agreement on the choice of the failure criterion to adopt for the bone tissue can be found in the literature among the finite element studies aiming at predicting fracture risk of bones. The use of stress-based criteria seems to prevail on strain-based ones, while basic bone biomechanics suggest using strain parameters to describe failure. The aim of the present combined experimental-numerical study was to verify, using subject-specific finite element models able to accurately predict strains, if a strain-based failure criterion could identify the failure patterns of bones. Three cadaver femurs were CT-scanned and subsequently fractured in a clinically relevant single-stance loading scenario. Load-displacement curves and high-speed movies were acquired to define the failure load and the location of fracture onset, respectively. Subject-specific finite element models of the three femurs were built from CT data following a validated procedure. A maximum principal strain criterion was implemented in the finite element models, and two stress-based criteria selected for comparison. The failure loads measured were applied to the models, and the computed risks of fracture were compared to the results of the experimental tests. The proposed principal strain criterion managed to correctly identify the level of failure risk and the location of fracture onset in all the modelled specimens, while Von Mises or maximum principal stress criteria did not give significant information. A maximum principal strain criterion can thus be defined a suitable candidate for the in vivo risk factor assessment on long bones.     

A fractographic study of human long bone

Based on the assumption that bone breaks where it is weakest, so that the fracture surface represents the weakest area locally, a fractographic study was made of a series of accidental and experimental fractures of human long bones. The architecture of the fracture surfaces as a whole, and of the local morphology of the fractured microstructure, was examined. This led to a classification of the fractographic features observed. Several quantitative characteristics of the experimental fracture surfaces were explored, including the number (no), volume fraction (po), and average cross-sectional area (Ao) of the osteons. These parameters were compared with the same data for cross-sections of the bone beneath the fracture surfaces. The results show a short-range fluctuation in the microstructural constitution of the diaphysis close to the fracture surface, with lower values of no, po and Ao at the fracture surface.     

Electro-mechanical behavior of wet bone--Part II: Wave propagation

In this study, a general mixture model, which was developed for wet bone, has been used to analyze the flexural wave propagation in long bones. The electrical conduction is taken into account as well as the piezo-electric properties of bone tissue. The general formulation is simplified and certain assumptions made to yield a particular set of equations. The solution of the magnetic induction vector outside the bone due to the mechanical wave propagation is obtained. The results are compared with a similar problem using dry bone. The results indicate that the electro-mechanical properties of bone tissue could be used for monitoring the rate of fracture healing in long bones.     

Load transfer analysis of the distal radius from in-vivo high-resolution CT-imaging.

Prevention of osteoporotic bone fractures requires accurate diagnostic methods to detect the increase in bone fragility at an early stage of osteoporosis. However, today's bone fracture risk prediction, primarily based on bone density measurement, is not sufficiently precise. There is increasing evidence that, in addition to bone density, also the bone microarchitecture and its mechanical loading conditions are important factors determining the fracture risk. Recently, it has been shown that new high-resolution imaging techniques in combination with new computer modeling techniques based on the finite-element (FE) method can account for these additional factors. These techniques might provide information that is more relevant for the prediction of bone fracture risk. So far, however, these new imaged-based FE techniques have not been feasible in-vivo. The objectives of this study were to quantify the load transfer through the trabecular network in a distal radius using a computer model based on in-vivo high-resolution images and to determine if common regions of fractures can be explained as a result of high tissue loading in these regions. The left distal radius and the two adjacent carpal bones of a healthy volunteer were imaged using a high-resolution three-dimensional CT system providing an isotropic resolution of 165 microm. The bone representation was converted into a FE-model that was used to calculate stresses and strains in the trabecular network. The two carpal bones were loaded using different load ratios (for each load case 1000 N in total) representing impact forces on the hand either in near-neutral position or ulnar/radial deviation. The load transfer through the trabecular network of the radius was characterized by the tissue strain energy density (SED) distribution for all load cases. It was found that the distribution of the tissue loading depends on the ratio of the forces acting on the carpal bones. For all load cases the higher SED values (on average: 0.02 +/- 0.08 (S.D.) N mm(-2)) are found in a 10 mm region adjacent to the articular surface which corresponds well with the region where Colles- or Chauffeur-fractures occur. We expect that, eventually, this new approach can lead to a better prediction of the fracture risk than methods based on bone density alone since it accounts for the bone microstructure as well as its loading conditions.     

ABC of emergency radiology. The ankle.

The os trigonum is a common normal variant of the talus and is due to a separate ossification centre arising from the posterior tubercle. The appearance may resemble an old ununited fracture fragment. However, it is triangular, well corticated, in a classic location, and usually bilateral, which enables it to be distinguished from a fracture. Transverse, sclerotic, linear lines located at the metaphysis of growing long bones are due to short periods of growth arrest and have no clinical importance (fig 5). They may be confused with compression fractures, but again these lines are usually bilateral. Fibrous cortical defects are the most commonly seen benign lesions of long bones and are usually identified incidentally in radiographs taken for another reason. The defect is limited to the cortex, commonly found at the metaphysis, but may be located in the diaphysis as the bone grows. The lesion is well corticated (sclerotic margins) and usually does not produce signs or symptoms.     

生物力学测试中小梁骨试件的保存和制备方法

骨骼在平时发挥的是支撑和运动作用,在受到撞击后保护脏器的同时自身也会断裂、受损,这都是骨与力之间相互作用产生的结果。如果可以知道骨的力学属性,并带入有限元模型计算,就可以个体化地预测其生活中的各种动作是否会导致急慢性创伤、协助判断暴力事件(如交通事故、坠落等)对其骨骼造成的破坏、在术前对骨骼质量给予指导性的评估[1]等。但是人类的骨骼看似简单,却千变万化,想要确切了解其各项属性的内在联系很困难。骨骼并不是几种材料的简单堆积,如骨骼整体的强度要大于其所有部位累计的强度[2]就是一个证明。一开始,骨的测试方法遵循普通材料的测试方法,随着研究的深入,对于骨的各个部位、各个类型的属性又有了很多新的探索。寻求最佳的试件保存、制作方法是后期测试获得成功的前提,试件保存的温度、水合状态、取材方向、形状和大小都会引起误差,多因素干扰也使分析结果变得更加困难。也正是因为如此,不同学者测得的数据差异往往比较明显。本研究旨在提炼、归纳一些通用、成熟、合理的方法,为后来的研究者在实验技术方面提供参考,让研究结果更有比较意义。     

Immunolocalization of IL-17A, IL-17B, and their receptors in chondrocytes during fracture healing.

Fracture healing in long bones is a sequential multistep cascade of hemostasis, transient inflammation, chemotaxis of progenitor cells, mitosis, differentiation of cartilage, and replacement with bone. This multistep cascade is orchestrated by cytokines and morphogens. Members of the interleukin (IL)-17 family, including IL-17B, have been identified in cartilage, but their expression during fracture healing is unknown. In this study, we determined the immunolocalization of cytokines IL-17A and IL-17B, along with the IL-17 receptor (IL-17R) and IL-17 receptor-like protein (IL-17RL), during the sequence of fracture repair in a standard model. The results were extended to developmental changes in the epiphyseal growth plate of long bones. Members of the IL-17 family were localized in chondrocytes in the fracture callus. Moreover, we found significant parallels to the localization of these cytokines and their receptors in chondrocytes during an endochondral differentiation program in the epiphyseal growth plate.     

Vibrational characteristics of bone fracture and fracture repair: application to excised rat femur

BACKGROUND: The vibrational characteristics of any object are directly dependent on the physical properties of that object. Therefore, changing the physical properties of an object will cause the object to adopt changed natural frequencies. A fracture in a bone results in the loss of mechanical stability of the bone. This change in mechanical properties of a bone should result in a change of the resonant frequencies of that bone. A vibrational method for bone evaluation has been introduced. METHOD OF APPROACH: This method uses the radiation force of focused amplitude-modulated ultrasound to exert a vibrating force directly, and remotely, on a bone. The vibration frequency is varied in the range of interest to induce resonances in the bone. The resulting bone motion is recorded and the resonance frequencies are determined. Experiments are conducted on excised rat femurs and resonance frequencies of intact, fractured, and bonded (simulating healed) bones are measured. RESULTS: The experiments demonstrate that changes in the resonance frequency are indicative of bone fracture and healing, i.e., the fractured bone exhibits a lower resonance frequency than the intact bone, and the resonance frequency of the bonded bone approaches that of the intact bone. CONCLUSION: It is concluded that the proposed radiation force method may be used as a remote and noninvasive tool for monitoring bone fracture and healing process, and the use of focused ultrasound enables one to selectively evaluate individual bones.     

Structural properties of fourth-generation composite femurs and tibias

The purpose of this study was to measure the structural properties of the latest design (fourth-generation) of composite femurs and tibias from Pacific Research Laboratories, Inc. Fourth-generation composite bones have the same geometries as the third-generation bones, but the cortical bone analogue material was changed to one with increased fracture and fatigue resistance, tensile and compressive properties, thermal stability, and moisture resistance. The stiffnesses of the femurs and tibias were tested under bending, axial, and torsional loading, and the longitudinal strain distribution along the proximal-medial diaphysis of the femur was also determined. The fourth-generation composite bones had average stiffnesses and strains that were for the most part closer to corresponding values measured for natural bones, than was the case for third-generation composite bones; all measurements were taken by the same investigator in separate studies using identical methodology. For the stiffness tests, variability between the specimens was less than 10% for all cases, and setup variability was less than 6%.     

Taphonomic evidence of a Paleogene mammalian predator–prey interaction

A taphonomic study has been undertaken on an assemblage of bones and teeth of Isoptychus sp. and Thalerimys fordi (extinct rodent family Theridomyidae) from a single bed in a coastal plain setting, in the Late Eocene (Priabonian) Osborne Member, Headon Hill Formation (Hampshire Basin, UK). The vertebrate fossils show good preservation and do not bear the marks of obvious long distance transport. The two theridomyid species show similar patterns of mortality, element representation and surface modifications, which indicate similar mechanisms of accumulation. There is high mortality of juvenile and old individuals indicating accumulation of the assemblage by the action of attritional not catastrophic agents. The postcranial elements show fragmentary states and very low relative abundances. The vast majority of elongate bones (limb bones, phalanges and metapodials) are broken and exhibit a spiral irregular type of fracture with rounded fracture edges indicating that the bones were broken when they were fresh and have subsequently undergone additional modification. The enamel of most of the cheek teeth and incisors shows localized etching to various degrees and most of the bones show etching. By elimination of other modifying agents the observed etching is attributed to digestive corrosion. Collectively, these data indicate that the majority of the theridomyid individuals were eaten and digested by an animal that could cause high fragmentation during ingestion and with stomach juices of relatively high acidity. Both these features characterize mammalian carnivores. The presence of puncture marks on bones of both theridomyid species and comparisons with sizes of bite marks caused by extant mammalian carnivores suggest predation by a small mammalian carnivore about the size of an arctic fox. The extinct amphicyonid carnivoran Cynodictis cf. lacustris occurs in the same bed and the sizes of some of its teeth match well with the sizes of the puncture marks on the theridomyid bones. A predator–prey interaction is, therefore, deduced for the amphicyonid and the two theridomyid species, thereby reconstructing a small part of the continental Paleogene food chain.     

The effect of strain rate on the failure stress and toughness of bone of different mineral densities

The risk of low energy fracture of the bone increases with age and osteoporosis. This paper investigates the effect of strain rate and mineral level on the peak stress and toughness of whole ovine bones.