Epidemiology and site specificity of stress fractures

Clinically, stress fractures appear to be a common overuse injury among athletes and in military recruits undertaking basic training; however, there is a lack of sound epidemiologic studies describing stress fracture occurrence in athletes. Few have directly compared stress fracture rates between sports to establish which poses the greatest risk for this injury. Furthermore, incidence rates, expressed in terms of exposure, have rarely been reported for stress fractures in athletes. Nevertheless, available data suggest that runners and ballet dancers are at relatively high risk for stress fractures. Although a gender difference in rates is clearly evident in military populations, this is less apparent in athletes. Other participant characteristics, such as age and race, may also influence stress fracture risk. The most common site of stress fracture in athletes is the tibia, although the site reflects the nature of the load applied to the skeleton. Stress fracture morbidity, expressed as the time until return to sport or activity, varies depending on the site. Generally, a period of 6 to 8 weeks is needed for healing; however, stress fractures at certain sites, such as the navicular and anterior tibial cortex, are often associated with protracted recovery and, in some cases, termination of sporting pursuits.     

Early confirmation of stress fractures in joggers

Four joggers had early confirmation of clinically suspected stress fractures by radionuclide bone scans. The radioactive bone scan was abnormal as early as six weeks prior to the appearance of conventional roentgenographic changes. The stress fractures involved the bones of the lower extremities and included the femur, tibia, and calcaneus. Radioactive bone scanning also correctly identified stress fractures with bilateral involvement and referred pain. In joggers, when a stress fracture is clinically suspected and the conventional radiographs are negative, a radioactive bone scan is indicated for early confirmation and institution of appropriate treatment.     

Stress fractures of the femoral neck

Stress fractures of the femoral neck are uncommon injuries. In general these injuries are seen in two distinct populations: (1) young, healthy, active individuals such as recreational runners, endurance athletes, or military recruits; and (2) the elderly who have osteoporosis. Stress fractures can be classified as either fatigue or insufficiency fractures and result from untoward cyclic loading or impaired bone quality. The key to treatment is early diagnosis, which may require scintigraphy or magnetic resonance imaging. Nondisplaced compression type stress fractures can be treated nonoperatively with protected weight-bearing and frequent radiographic followup. Tension type stress fractures should be stabilized internally to prevent the adverse consequences of fracture displacement.     

多形态裂隙砂岩水力耦合破坏过程与增透机理试验研究

水力耦合激活岩石天然裂隙,诱导裂隙扩展形成复杂裂隙网络,增加岩石渗透性是矿产地热共采体系中的关键技术。本文通过预制含单裂隙、T型裂隙和Y型裂隙的砂岩试样,进行三轴水力耦合试验,研究多形态裂隙砂岩的关键阈值（闭合应力、起裂应力、损伤应力、峰值强度）、弹性模量、泊松比以及破坏模式等力学特性,同时开展裂隙渐进演化过程中声发射和渗透率的演化规律研究,进一步分析水力耦合作用下裂隙岩石增透机理。结果表明:多形态预制裂隙砂岩试样在水力耦合作用下,既有裂隙均通过拉伸、剪切或混合模式扩展形成次生裂纹,构成裂隙网络,试样渗透率显著增加。单裂隙试样的次生裂隙以剪切破坏为主,T型和Y型裂隙试样的次生裂隙为剪切破坏和张拉-剪切破坏两类。此外,多形态裂隙对试样强度的影响大于水的弱化作用。随着轴压增大,岩石渗透率峰前阶段先减小后增大,达到强度破坏时突跳增大。当试样达到峰值后应力突然下降时,渗透率达到最大值,渗透率增透效果最好。预制裂隙角度和形态的变化对突跳系数的影响幅度较小,单裂隙的平均突跳系数值大于Y型裂隙大于T型裂隙。研究结果有助于理解裂隙破坏和流体流动行为,进而指导矿产地热共采的工程。      

Fractures of the metatarsal bones caused by fatigue

The term stress (marching) fracture relates to a fracture provoked without acute trauma, on healthy bone and as a consequence of repeated, long-term, rhythmic load [4, 5]. Stress fractures are mostly observed in young people (12-25 years of age) [15]. The course of this phenomenon we found by medical examination; this means that it is found either by detection or spontaneous ambulance reports. The aim of this study is to point at a possible appearance of these fractures at young soldiers and sportsmen. MATERIAL AND METHOD: During the routine ambulance practice, and by the prospective study on 29 subjects, the study was performed by using oral inquiry [9]. The studied individuals were soldiers who were complaining of pain, swellings and redness of the feet. Except clinical orthopedic examination, additional laboratory analysis was made. RESULTS: The results are shown in tables. Table 1 shows that stress fractures of metatarsus bones usually appear during the period of first thirty days of the military service, i.e. during the days of the hardest exertion. The most frequent training absence, which is caused by stress fractures, is during this period of time (Table 2). Of all military duties, marching had the biggest influence on appearance of this disease (Table 3). DISCUSSION: On the basis of available literature it is evident that there are factors which might have the influence on the occurrence of the disease (hypovitaminosis, foot-wear, foot deformation, body weight, muscle fatigue, etc.). Stress fractures are mentioned in connection with some diseases or special clinical deformations such as rheumatoid arthritis, chronic bronchitis, arthrosis deformities, after arthroplastics, Mb. Bechterew, etc. Consequently, stress fractures do not appear only in a healthy bone, as it is defined [4, 5]. In the clinical practice it was established that the diagnosis of this pathology had, in a few cases, the same clinical picture. On the basis of our experience, by observing, we have concluded that stress fractures occur on healthy or changed bones as the result of physical fatigue of the material, and repeated movements. It is still unclear why these changes are unilateral. CONCLUSION: a) Stress fractures are frequently appearing at young soldiers. b) Most frequently they appear in beginning of hard and exhaustible training.     

Normal Transmission of S-Wave Across Parallel Fractures with Coulomb Slip Behavior

When an elastic wave propagates through a rock mass, its amplitude is attenuated and velocity is slowed due to the presence of fractures. During wave propagation, if the shear stress at a fracture interface reaches the fracture shear strength, the fracture will experience a large shear displacement. This paper presents a study of the normal transmission of S-waves across parallel fractures with Coulomb slip behavior. In our theoretical formulation, the method of characteristics combined with the Coulomb slip model is used to develop a set of recurrence equations with respect to particle velocities and shear stress. These equations are then solved numerically. In a comparison with the theoretical study, numerical modeling using the universal distinct element code (UDEC) has been conducted. A general agreement between UDEC modeling and theoretical analysis is achieved. The magnitude of the transmission coefficient is calculated as a function of shear stress ratio, nondimensional fracture spacing, normalized shear stiffness, and number of fractures. The study shows that the shear stress ratio is the most important factor influencing wave transmission, and the influence of other factors becomes more apparent when the shear stress ratio is small.     

A study of intrinsic factors in patients with stress fractures of the tibia

We aimed to study intrinsic factors in 29 consecutive patients with well-documented unilateral stress fractures of the tibia. Anthropometry, range of motion, isokinetic plantar flexor muscle performance, and gait pattern were analyzed. The uninjured leg served as the control. A reference group of 30 uninjured subjects was compared regarding gait pattern. Anterior stress fractures of the tibia (N = 10) were localized in the push-off/ landing leg in 9/10 athletes, but were similarly distributed between legs in posteromedial injuries (N = 19). Ten (30%) of the stress fracture subjects had bilateral high foot arches, similar to those found in the reference group. There were no other systematic differences in anthropometry, range of motion, gait pattern, or isokinetic plantar flexor muscle peak torque and endurance between injured and uninjured legs. No other differences were found between anterior and posteromedial stress fractures. We conclude that anterior stress fractures of the tibia occur mainly in the push-off/landing leg in athletes. Within the limitations of our protocol, no registered intrinsic factor was found to be directly associated with the occurrence of a stress fracture of the tibia.     

Classification of ankle fractures in children

The roentgenograms of 310 children treated for ankle fractures were evaluated for grouping according to the classifications of Ashhurst-Bromer-Weber, Lauge-Hansen, and Salter-Harris. The mean age of the children at the time of injury was 11.1 years (range 2-14 years). Two hundred twenty-one (71.3%) children had malleolar fractures, 71 (22.9%) had tibial epiphyseal fractures, and 18 (5.8%) had syndesmotic lesions. The age distribution of fractures was typical: malleolar fractures predominated among the younger children, epiphyseal fractures among the older. Only the oldest children had avulsion fractures of the syndesmosis. Grouping of the fractures according to Lauge-Hansen and Ashhurst-Bromer-Weber, classifications suited to adults was largely unsuccessful. Epiphyseal fractures, moreover, were easily classified according to Salter-Harris. In spite of their complexity, ankle fractures in children can be roughly divided into avulsional and epiphyseal fractures. Adequately reduced avulsional fractures can be expected to heal well; epiphyseal fractures, however, may five rise to late complications. We propose, therefore, that ankle fractures in children be classified on the basis of roentgenological findings with respect primarily to epiphyseal lesions as well as on an additional simple grouping as to risk for clinical purposes: Group I, low risk, avulsional fractures and epiphyseal separations; Group II, high risk, fractures through the epiphyseal plate.     

Simultaneous bilateral tibial stress fractures in a 15-year-old milkman--a case report

Although stress fractures are well recognized, their frequency, sequelae and complex aetiology are often under-rated. In this case report, we describe an unusual case of simultaneous bilateral stress fractures of the proximal tibial shaft in a young man, exposed to a sudden increase in unaccustomed joint loading due to his part-time occupation. The pathogenesis is discussed.     

高碳钢盘条在拉拔前发生脆断的原因分析

通过SEM电子显微镜观察了不同牌号的高碳钢盘条在使用前或机械剥壳过程中发生脆断的断口形貌,利用光学显微镜检验了脆断盘条断口处对应的金相组织,分析了盘条发生脆断的原因。结果表明,盘条在吊装或运输过程中,由于碰撞或摩擦等机械外力作用造成盘条表面局部金属发生剧烈变形,导致盘条表面组织发生变化,形成应力集中从而诱发裂纹,最终造成盘条在使用前或机械剥壳过程中发生脆断。     

Estimating Pressure Losses in Interconnected Fracture Systems: Integrated Tensor Approach

A significant number of petroleum reservoirs and almost all geothermal reservoirs are characterized by high in situ stress and fractures, and fractures act as major flow paths for fluids. An integrated tensor model is proposed to solve three tasks: characterization of a heterogeneous fracture network, simulation of fluid flow through a complex system for estimation of the grid-based permeability tensor, and unsteady-state fluid flow simulation for estimation of production and pressure losses. Deformation of the matrix and fractures are solved separately and used to compute their dynamic porosity and permeability. Finite-element methods and boundary element methods are used for numerical modeling. The results of this study show that the proposed model can overcome problems requiring excessive computational resources, flow interactions between the matrix and fracture, and the effect of matrix deformation on fluid flow. Results also show that the integrated tensor model serves as an efficient tool for predicting the effect of stress on fracture deformation and consequent productivity and/or injectivity of naturally fractured reservoirs.     

Applying an empty-chair monologue paradigm to examine unresolved grief

The thoracic bellows mechanism consists of the rib cage and the diaphragm. The purpose of this study was to determine if nontraumatically acquired lesions of the bellows were secondary to underlying disease. Abnormalities of the bellows, specifically stress fractures of the ribs and hiatal hernia, were found in 21 dogs and cats with underlying cardiopulmonary disease, neuromuscular disease, or metabolic disease. A case-control study of Bulldogs demonstrated that hiatal hernia was associated with the more severe manifestations of brachycephalic syndrome. Stress fractures occurred mostly in females and in cats, and involved multiple ribs. Fractures were usually related to severe respiratory effort, but also occurred in association with metabolic disease. Hiatal hernia was also associated with severe respiratory effort, but may be exacerbated if a neuromuscular disorder affecting the diaphragm is present. Abnormalities of the thoracic bellows, such as rib stress fractures and hiatal hernia, may be signs of underlying disease, rather than being primary causes of disease.     

Anorectal diseases

Fracture of the tibia is a well-known, often occult cause of limping and leg pain in young children. This fracture is typically a hairline, oblique fracture of the shaft of the tibia, and in some cases the fracture can be so subtle that bone scintigraphy or follow-up radiography may be required for its detection. In addition, a variety of other fractures that are less well known and just as difficult to detect can occur in the tibia and the foot in young children. These fractures include plastic bowing and buckle-type fractures, especially of the fibula; impaction, compression, or stress (fatigue) fractures of the tibia and fibula; and fractures of the metatarsal and tarsal bones. All of these fractures can be remarkably similar to the non-displaced spiral tibial fracture in their clinical appearance and should be included under the rubric of "toddler's fracture."     

Jones' fractures and related fractures of the proximal fifth metatarsal

At least three fracture types occur in the proximal fifth metatarsal: the Jones' fracture, the proximal diaphysial stress fracture, and the tuberosity avulsion fracture. Each has distinct characteristics. The diaphysial stress fracture is commonly confused with the Jones' fracture, thereby obscuring vital differences in prognosis and treatment. Anatomical and biomechanical characteristics, as well as vascular studies of the proximal portion of the fifth metatarsal, are discussed in an attempt to better understand their diverse healing potentials. Guidelines for treatment are controversial, and must frequently be individualized. Although surgical intervention for certain proximal fifth metatarsal fracture types may speed recovery time, most fractures heal with immobilization. Treatment of displaced, intra-articular fractures, delayed unions, and nonunions usually requires operative methods.     

Risk factors for stress fractures in track and field athletes. A twelve-month prospective study

The aim of this 12-month prospective study was to investigate risk factors for stress fractures in a cohort of 53 female and 58 male track and field athletes, aged 17 to 26 years. Total bone mineral content, regional bone density, and soft tissue composition were measured using dual-energy x-ray absorptiometry and anthropometric techniques. Menstrual characteristics, current dietary intake, and training were assessed using questionnaires. A clinical biomechanical assessment was performed by a physical therapist. The incidence of stress fractures during the study was 21.1% with most injuries located in the tibia. Of the risk factors evaluated, none was able to predict the occurrence of stress fractures in men. However, in female athletes, significant risk factors included lower bone density, a history of menstrual disturbance, less lean mass in the lower limb, a discrepancy in leg length, and a lower fat diet. Multiple logistic regression revealed that age of menarche and calf girth were the best independent predictors of stress fractures in women. This bivariate model correctly assigned 80% of the female athletes into their respective stress fracture or nonstress fracture groups. These results suggest that it may be possible to identify female athletes most at risk for this overuse bone injury.     

Delayed cortical blindness and recurrent quadriplegia after cervical trauma

There are various osseous pathologies that afflict the tarsal navicular. These range from stress fractures and coalitions to overt fractures. In certain instances there is an interruption of its vascular supply. If this occurs in childhood, it is called Koehler's disease. Spontaneous osteonecrosis of the navicular in the adult is a rare entity and is known as Mueller-Weiss syndrome. There is little English literature available on the latter. A review of the literature and a case report are presented here.     

复杂应力路径下裂隙泥岩渗透演化规律试验研究

油气主要储集在岩石孔隙和缝洞内,深部复杂应力环境下储层岩石裂隙渗透演化直接影响油气的运移规律,是油气勘探开发的重要研究对象。为了解复杂应力路径下含裂隙岩石的渗透演化特性,利用高精度渗流?应力耦合三轴实验设备,对含随机分布裂隙泥岩开展了单试样?复杂应力路径加卸载过程中的渗透性演化试验研究,试验方案依次为:(i) 围压递增条件下渗透性测试;(ii) 渗透压力递增条件下渗透性测试;(iii) 偏应力循环加卸载条件下渗透性测试;(iv) 围压、偏应力同步增长条件下渗透性测试。结果表明裂隙泥岩中的渗流可视为低渗流速度的层流;裂隙发育丰富岩样（R2）渗透率及应力敏感性明显较高。渗透率随渗透压力、围压分别呈正、负的指数函数变化。偏应力加载导致渗透率降低,卸载引起渗透率上升,但整体呈不可逆降低;围压、偏应力同步增长引起渗透率呈下降趋势,并逐步趋于稳定;围压10.3 MPa作用下,渗透率基本保持恒定。由此,基于裂隙双重介质模型,考虑泥岩变形过程中裂隙系统和基质系统的相互作用以及外部应力作用下的裂隙膨胀变形,构建了裂隙泥岩渗透率演化力学模型;模型模拟结果与试验结果具有较好的一致性。相关成果可为裂隙泥岩渗透性演化预测和油气高效开采提供重要的理论依据。      

The Troms? Study: physical activity and the incidence of fractures in a middle-aged population

We have studied the relation of occupational and recreational physical activity to fractures at different locations. All men born between 1925 and 1959 and all women born between 1930 and 1959 in the city of Troms? were invited to participate in surveys in 1979-1980 and 1986-1987 (The Troms? Study). Of 16,676 invited persons, 12,270 (73.6%) attended both surveys. All nonvertebral fractures (n = 1435) sustained from 1988 to 1995 were registered in the only hospital in the area. Average age in the middle of the follow-up period (December 31, 1991) was 47.3 years among men and 4501 years among women, ranging from 32 to 66 years. Fracture incidence increased with age at all locations among women, but it decreased with or was independent of age among men. Low-energetic fractures constituted 74.4% of all fractures among women and 55.2% among men. When stratifying by fracture location, the most physically active persons among those 45 years or older suffered fewer fractures in the weight-bearing skeleton (relative risk [RR] 0.6, confidence interval [CI] 0.4-0.9, age-adjusted), but not in the non-weight-bearing skeleton (RR 1.0, CI 0.7-1.2, age-adjusted) compared with sedentary persons. The relative-risk of a low-energetic fracture in the weight-bearing skeleton among the most physically active middle-aged was 0.3 (CI 0.1-0.7) among men and 0.9 (CI 0.4-1.8) among women compared with the sedentary when adjusted for age, body mass index, body height, tobacco smoking, and alcohol and milk consumption. It seems that the beneficial effect on the skeleton of weight-bearing activity is reflected also in the incidence of fractures at different sites.     

Multiple stress fractures in a scleroderma patient on methotrexate therapy

A patient on methotrexate therapy for scleroderma developed four stress fractures within a period of 13 months. She was not on steroid therapy and had no risk factors for osteoporosis. A review of the literature found 13 cases of stress fractures under methotrexate therapy. Whether methotrexate can induce bone changes remains controversial.     

Drug interactions as a cause of overanticoagulation and bleedings in Chinese patients receiving warfarin

Stress fractures in children are rare compared with the incidence in adults. This report describes an 11-year-old girl with stress fractures of the acromion, clavicle, and first rib on the left and contralateral fractures of the first and second ribs. It was eventually discovered that these fractures were caused by a nervous tic consisting of repetitive, vigorous shrugging and translation of the shoulders.