SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Fracture

478

To examine the evidence underpinning recommendations to increase calcium intake through dietary sources or calcium supplements to prevent fractures.

Concepts: Osteoporosis, Bone, Bone fracture, Fracture, Calcium

179

During the lifetime of a flying insect, its wings are subjected to mechanical forces and deformations for millions of cycles. Defects in the micrometre thin membranes or veins may reduce the insect’s flight performance. How do insects prevent crack related material failure in their wings and what role does the characteristic vein pattern play? Fracture toughness is a parameter, which characterises a material’s resistance to crack propagation. Our results show that, compared to other body parts, the hind wing membrane of the migratory locust S. gregaria itself is not exceptionally tough (1.04±0.25 MPa√m). However, the cross veins increase the wing’s toughness by 50% by acting as barriers to crack propagation. Using fracture mechanics, we show that the morphological spacing of most wing veins matches the critical crack length of the material (1132 µm). This finding directly demonstrates how the biomechanical properties and the morphology of locust wings are functionally correlated in locusts, providing a mechanically ‘optimal’ solution with high toughness and low weight. The vein pattern found in insect wings thus might inspire the design of more durable and lightweight artificial ‘venous’ wings for micro-air-vehicles. Using the vein spacing as indicator, our approach might also provide a basis to estimate the wing properties of endangered or extinct insect species.

Concepts: Blood, Fracture, Insect, Fracture mechanics, Locust, Insect wing, Fracture toughness, Orthoptera

174

Plastin 3 (PLS3), a protein involved in the formation of filamentous actin (F-actin) bundles, appears to be important in human bone health, on the basis of pathogenic variants in PLS3 in five families with X-linked osteoporosis and osteoporotic fractures that we report here. The bone-regulatory properties of PLS3 were supported by in vivo analyses in zebrafish. Furthermore, in an additional five families (described in less detail) referred for diagnosis or ruling out of osteogenesis imperfecta type I, a rare variant (rs140121121) in PLS3 was found. This variant was also associated with a risk of fracture among elderly heterozygous women that was two times as high as that among noncarriers, which indicates that genetic variation in PLS3 is a novel etiologic factor involved in common, multifactorial osteoporosis.

Concepts: Osteoporosis, Bone, Genetics, Natural selection, Bone fracture, Fracture, Actin, Osteogenesis imperfecta

168

Background: The purpose of this study was to compare the biomechanical properties of locked versus nonlocked lateral fibular bridge plating of comminuted, unstable ankle fractures in a mode of catastrophic failure. Methods: We created comminuted Weber C fractures in 8 paired limbs from fresh cadavers. Fractures were plated with either standard or locked one-third tubular bridge plating techniques. Specimens were biomechanically evaluated by external rotation to failure while subjected to a compressive load approximating body weight. We measured the angle to failure, torque to failure, energy to failure and construct stiffness. Results: There was no significant difference in construct stiffness or other biomechanical properties between locked and standard one-third tubular plating techniques. Conclusion: We found no difference in biomechanical properties between locked and standard bridge plating of a comminuted Weber C fibular fracture in a model of catastrophic failure. It is likely that augmentation of fixation with K-wires or transtibial screws provides a construct superior to locked bridge plating alone. Further biomechanical and clinical analysis is required to improve understanding of the role of locked plating in ankle fractures and in osteoporotic bone.

Concepts: Osteoporosis, Bone, Bone fracture, Fracture, Elasticity, Forensic engineering, Plating, Fibula

150

Vertebral fractures and trabecular bone loss have dominated thinking and research into the pathogenesis and the structural basis of bone fragility during the last 70 years. However, 80% of all fractures are non-vertebral and occur at regions assembled using large amounts of cortical bone; only 20% of fractures are vertebral. Moreover, ~80% of the skeleton is cortical and ~70% of all bone loss is cortical even though trabecular bone is lost more rapidly than cortical bone. Bone is lost because remodelling becomes unbalanced after midlife. Most cortical bone loss occurs by intracortical, not endocortical remodelling. Each remodelling event removes more bone than deposited enlarging existing canals which eventually coalesce eroding and thinning the cortex from ‘within.’ Thus, there is a need to study the decay of cortical as well as trabecular bone, and to develop drugs that restore the strength of both types of bone. It is now possible to accurately quantify cortical porosity and trabecular decay in vivo. The challenges still to be met are to determine whether measurement of porosity identifies persons at risk for fracture, whether this approach is compliments information obtained using bone densitometry, and whether changes in cortical porosity and other microstructural traits have the sensitivity to serve as surrogates of treatment success or failure.

Concepts: Osteoporosis, Bone, Bone fracture, Fracture, Skeletal system, Osseous tissue, Cortical bone, Cancellous bone

67

Background Romosozumab, a monoclonal antibody that binds sclerostin, increases bone formation and decreases bone resorption. Methods We enrolled 7180 postmenopausal women who had a T score of -2.5 to -3.5 at the total hip or femoral neck. Patients were randomly assigned to receive subcutaneous injections of romosozumab (at a dose of 210 mg) or placebo monthly for 12 months; thereafter, patients in each group received denosumab for 12 months, at a dose of 60 mg, administered subcutaneously every 6 months. The coprimary end points were the cumulative incidences of new vertebral fractures at 12 months and 24 months. Secondary end points included clinical (a composite of nonvertebral and symptomatic vertebral) and nonvertebral fractures. Results At 12 months, new vertebral fractures had occurred in 16 of 3321 patients (0.5%) in the romosozumab group, as compared with 59 of 3322 (1.8%) in the placebo group (representing a 73% lower risk with romosozumab; P<0.001). Clinical fractures had occurred in 58 of 3589 patients (1.6%) in the romosozumab group, as compared with 90 of 3591 (2.5%) in the placebo group (a 36% lower risk with romosozumab; P=0.008). Nonvertebral fractures had occurred in 56 of 3589 patients (1.6%) in the romosozumab group and in 75 of 3591 (2.1%) in the placebo group (P=0.10). At 24 months, the rates of vertebral fractures were significantly lower in the romosozumab group than in the placebo group after each group made the transition to denosumab (0.6% [21 of 3325 patients] in the romosozumab group vs. 2.5% [84 of 3327] in the placebo group, a 75% lower risk with romosozumab; P<0.001). Adverse events, including instances of hyperostosis, cardiovascular events, osteoarthritis, and cancer, appeared to be balanced between the groups. One atypical femoral fracture and two cases of osteonecrosis of the jaw were observed in the romosozumab group. Conclusions In postmenopausal women with osteoporosis, romosozumab was associated with a lower risk of vertebral fracture than placebo at 12 months and, after the transition to denosumab, at 24 months. The lower risk of clinical fracture that was seen with romosozumab was evident at 1 year. (Funded by Amgen and UCB Pharma; FRAME ClinicalTrials.gov number, NCT01575834 .).

Concepts: Osteoporosis, Pharmacology, Bone, Clinical trial, Bone fracture, Hip fracture, Fracture, Placebo

32

Hip fracture is the most severe bone fragility fracture among osteoporotic injuries. Family history is a known risk factor for fracture and now included among criteria for osteoporosis diagnosis and treatment; however, genetic factors underlying family history favoring fracture remain to be elucidated. Here we demonstrate that a missense SNP in the ALDH2 gene, rs671 (ALDH2*2), is significantly associated with hip fracture (odds ratio = 2.48, 95% confidence interval: 1.20-5.10, p = 0.021). The rs671 SNP was also significantly associated with osteoporosis development (odds ratio = 2.04, 95% confidence interval: 1.07-3.88, p = 0.040). For analysis we enrolled 92 hip fracture patients plus 48 control subjects without bone fragility fractures with higher than -2.5 SD bone mineral density. We also recruited 156 osteoporosis patients diagnosed as below -2.5 SD in terms of bone mineral density but without hip fracture. Association of rs671 with hip fracture and osteoporosis was significant even after adjustment for age and body mass index. Our results provide new insight into the pathogenesis of hip fracture.

Concepts: DNA, Osteoporosis, Bone, Genetics, Bone fracture, Fracture, SNP array, Body mass index

28

Osteopetrosis is a rare skeletal condition first described by German radiologist Heinrich Albers-Schonberg. The most important technical difficulty is drilling due to hard bone in patients with osteopetrosis; recommendations have been made to use high-speed electric drill bits. But, the unavailability of this special drill bit in most of the centres makes the job more difficult. The study was conducted from 2009 to 2012; the cases are selected from Outpatients Department of Postgraduate Institute of Medical Education and Research. The patients were in the age group of 10-50 years with a mean age of 26 years. Five cases were included in the study: four patients had subtrochanteric fractures, and one had segmental fracture of the humerus. Open reduction and internal fixation was done in all the fractures using metal-cutting drill bit. The use of metal-cutting drill bit in osteopetrosis not only made our job easy but also prevented thermal necrosis of the bone to a large extent. The union rate was 100 % in our series, and there was no infection in any of our cases. In the treatment for fractures in osteopetrosis, the use of a metal-cutting drill bit along with careful attention to drilling technique can help avoid bit breakage and thermal bone injury that may produce ring sequestrum or destroy the already scant osteogenic cells.

Concepts: Bone, Bone fracture, Fracture, Orthopedic surgery, Drill, Intramembranous ossification, Drill bit, Drilling and threading

28

The most stable pattern of internal fixation for fractures of the mandibular condyle is a matter for ongoing discussion. In this study we investigated the stability of three commonly used patterns of plate fixation, and constructed finite element models of a simulated mandibular condylar fracture. The completed models were heterogeneous in the distribution of bony material properties, contained about 1.2 million elements, and incorporated simulated jaw-adducting musculature. Models were run assuming linear elasticity and isotropic material properties for bone. This model was considerably larger and more complex than previous finite element models that have been used to analyse the biomechanical behaviour of differing plating techniques. The use of two parallel 2.0 titanium miniplates gave a more stable configuration with lower mean element stresses and displacements over the use of a single miniplate. In addition, a parallel orientation of two miniplates resulted in lower stresses and displacements than did the use of two miniplates in an offset pattern. The use of two parallel titanium plates resulted in a superior biomechanical result as defined by mean element stresses and relative movement between the fractured fragments in these finite element models.

Concepts: Bone fracture, Fracture, Mathematics, Finite element method, Materials science, Orientation, Elasticity, Finite element method in structural mechanics

28

The authors analyzed the effect of fatigue on the survival rate and fracture load of monolithic and bi-layer CAD/CAM lithium-disilicate posterior three-unit fixed dental prostheses (FDPs) in comparison to the metal-ceramic gold standard.

Concepts: Fracture, Fracture mechanics, Gold, Gold standard