Two stage fracture of a polyethylene post in a 9-year-old posterior-stabilized knee prosthesis: a case report

<p>Abstract</p> <p>Introduction</p> <p>Several cases of tibial post breakage are reported in the literature. To the best of our knowledge, only three cases of NexGen knee prosthesis (Zimmer, Warsaw, Indiana, USA) tibial post failure have been reported.</p> <p>Case presentation</p> <p>In November 1999, a 63-year-old Caucasian woman from Italy with a history of symptomatic left knee osteoarthritis underwent a total knee arthroplasty. In March 2008, while rising from a chair, she felt a sudden pain and instability in her left knee. She reported a fracture of the polyethylene post of the tibial insert. No malposition or malalignment of either the femoral or tibial components were identified. The polyethylene tibial insert was studied under light microscopy and scanning electron microscopy. The fracture was also noted to have occurred without any notable polyethylene wear.</p> <p>Conclusion</p> <p>Scanning electron microscopy revealed two different damage patterns that could be explained with a two-stage rupture of our patient's polyethylene post. This could have been caused by a non-optimal ligamentous balancing during first implant surgery. Her knee probably developed a varus instability that weakened the post, and then a posterior anterior stress finally broke the polyethylene.</p

Increasing risk of revision due to deep infection after hip arthroplasty: A study on 97,344 primary total hip replacements in the Norwegian Arthroplasty Register from 1987 to 2007

Background and purpose Over the decades, improvements in surgery and perioperative routines have reduced the incidence of deep infections after total hip arthroplasty (THA). There is, however, some evidence to suggest that the incidence of infection is increasing again. We assessed the risk of revision due to deep infection for primary THAs reported to the Norwegian Arthroplasty Register (NAR) over the period 1987–2007

Optical Properties of DNA in Aqueous Solution

In the study of DNA electric birefringence, it is usual to use theories that consider that molecules in solution are small in relation to the light wavelength. In this work, we study the DNA electric birefringence using a broken-rod macroion (BRM) model composed of two cylindrical arms which does not restrict the size of the molecules. To achieve this, we include the inhomogeneity effect of the light electric field through the molecule and the interaction between its different parts. To analyze the interaction between a molecule and the incident beam of light, we apply the discrete dipole approximation (DDA), according to which each molecule is described as a finite array of electronic coupled oscillators. The electric birefringence is calculated from the oscillator polarizability. This is obtained from experimental data of electric birefringence saturation and from the increment of the solution refraction index in relation to that of the solvent. Furthermore, the oscillator polarizability is also estimated from DNA absorption spectrum using the Kronig–Kramers relations. This allows us to analyze the contributions of the different absorption bands of DNA to the electric birefringence. We analyze the influence of the inhomogeneity of the light electric field and of the intramolecular interactions in the characterization of DNA optical properties using electric birefringence measurements

Уральский рабочий. 1942. № 197

Theorists and activists favor empowering government agencies to regulate technology; but an examination of such regulation by the US government exposes the inadequacy of any such regimen. Vested interests routinely interfere, e.g., keeping administration of polio vaccine in the hands of physicians, political infighting with regard to cancer research funding, advantages gained from noncompliance with military technology-constraining treaties. Public/private salary differences limit availability of the best talents for government positions, nor are truly appropriate regulatory policies easily arrived at in the absence of meaningful funding. Solutions such as a Science Court are unreliable given the influences that would undermine neutrality as well as competence

Parental anxiety, parenting behavior, and infant anxiety: differential associations for fathers and mothers

Most studies investigating the role of parenting behavior in the intergenerational transmission of anxiety from parents to children have focused on mothers. However, recent research suggests that mothers and fathers may parent differently and may differentially affect the development of child anxiety. Theoretical models propose that anxious parents engage in more anxiety-provoking and less anxiety-reducing parenting behavior than non-anxious parents. However, findings are inconsistent, possibly because most studies have not differentiated between anxiety disorders. Therefore, it remains unclear which specific anxiety disorders are linked to parenting behavior. This study examined (1) whether symptoms of specific parental anxiety disorders are linked to overinvolvement and challenging parenting behavior towards infants; and (2) the differential relationship of maternal/paternal overinvolvement and challenging parenting behavior with infant anxiety. Parents of 81 infants (10-15 months) completed the Overinvolvement and Challenging parenting behavior (CPB) scales of the Comprehensive Parenting Behavior Questionnaire, the Screen for Child Anxiety Related Emotional Disorders-Adult version, and the Fear scale of the Infant Behavior Questionnaire-Revised. Linear regressions showed that mothers’ generalized anxiety disorder symptoms were associated with less CPB and more overinvolvement, whereas fathers’ social anxiety disorder symptoms were associated with less CPB and more overinvolvement. Moreover, paternal, but not maternal, CPB was associated with less infant anxiety, and overinvolvement with more infant anxiety. Findings suggest that (1) different dimensions of paternal/maternal anxiety are linked to their parenting behavior; (2) maternal/paternal parenting behaviors are differentially associated with infant anxiety

Does grassland vegetation drive soil microbial diversity?

Does plant diversity drive soil microbial diversity in temperate, upland grasslands? Plants influence microbial activity around their roots by release of carbon and pot studies have shown an impact of different grass species on soil microbial community structure. Therefore it is tempting to answer yes. However, evidence from field studies is more complex. This evidence is reviewed at three different scales. First, studies from the plant community scale are considered that have compared soil microbial community structure in pastures of different vegetation composition, as a consequence of pasture improvement. These show fungi dominating the biomass in unimproved pastures and bacteria when lime and fertilizers have been applied. Secondly, evidence for interactions between individual grass species and soil microbes is discussed at the level of the rhizosphere, by considering both pot experiments and field studies. These have produced contrasting and inconclusive results, often due to spatial heterogeneity of soil properties and microbial communities. In particular, increased soil pH and fertility in urine patches and other nutrient cycling processes interact to increase the spatially complexity of soil microbial communities. Finally three studies which have measured microbial community structure in the rhizoplane are considered. These show that bacterial diversity is not directly related to plant diversity, although fungal diversity is. In addition, the soil fungal community has been demonstrated to have an effect upon the composition of the bacterial community. We suggest that while current vegetation influences fungal communities (particularly mycorrhizae) and litter inputs fungal saprotrophs, bacterial community structure is influenced more by the quality or composition of soil organic matter, thereby reflecting carbon inputs to the soil over decades