Emergency reconstruction of extensor terminal slip defect by tendon plasty

INTRODUCTION

We report our experience with a tendon plasty technique to reconstruct extensor terminal slip defect, with results in 11 patients.

MATERIAL AND METHODS

The technique was proposed to 11 patients with mean tendon defects of 6 mm. Mean follow-up was 10.6 months. Clinical assessment comprised active distal interphalangeal (DIP) range of motion, active DIP extension and spontaneous DIP extension deficit.

RESULTS

Mean range of motion was 50 °. Active extension was restored in all cases. There was a mean 11 ° spontaneous DIP extension deficit.

DISCUSSION

The present results confirmed those in the literature for this type of tendon plasty. As well as these encouraging outcomes, the technique has the advantage of being simple, with low morbidity thanks to remote harvesting.

A 4He vector zero-field optically pumped magnetometer operated in the Earth-field

Low intrinsic noise, high bandwidth, and high accuracy vector magnetometers are key components for many ground or space geophysical applications. Here, we report the design and the test of a ⁴He vector optically pumped magnetometer specifically dedicated to these needs. It is based on a parametric resonance magnetometer architecture operated in the Earth magnetic field with closed-loop compensation of the three components of the magnetic field. It provides offset-free vector measurements in a ±70 μT range with a DC to 1 kHz bandwidth. We demonstrate a vector sensitivity up to 130 fT/√Hz, which is about ten times better than the best available fluxgate magnetometers currently available for the same targeted applications.

Total trapeziectomy

Total trapeziectomy has been extensively studied and has been used to treat thumb basal joint arthritis for decades. It remains a simple and reliable technique that every hand surgeon must learn and master, as a primary or revision procedure. Several techniques have been described, but none of them seems better than the others. Without the need for an implant and because of its long-lasting benefits, total trapeziectomy is currently the only surgical technique for thumb basal joint arthritis that can lay claim to being a potential life-long procedure.

Emergency metacarpophalangeal arthroplasty with bone grafting for traumatic joint destruction: a report on two cases

Traumatic destruction of the metacarpophalangeal joints with bone defect is a technical challenge for surgeons when maintaining joint mobility is a priority for the patient. An emergency metacarpophalangeal arthroplasty with bone graft has been described in the literature for dorsal defects in the proximal phalanx. We have adapted this technique to allow us to perform this arthroplasty with bone graft in all defects of the proximal phalanx.

All-optical isotropic scalar 4He magnetometer based on atomic alignment

We propose a helium scalar magnetometer based on a triple resonance setup, showing no dead angles, and which can be implemented in an all-optical way. This triple-resonance scheme involves optical pumping with amplitude-modulated light, complemented by a modulated light-shift. Both light beams propagate parallel so that a single optical access to the atomic cell is needed. Experimental results are in good agreement with our theoretical model. The main error sources affecting the magnetometer accuracy are discussed.

Juvenile food limitation in standardized tests: a warning to ecotoxicologists

Standard ecotoxicological tests are as simple as possible and food sources are mainly chosen for practical reasons. Since some organisms change their food preferences during the life-cycle, they might be food limited at some stage if we do not account for such a switch. As organisms tend to respond more sensitively to toxicant exposure under food limitation, the interpretation of test results may then be biased. Using a reformulation of the von Bertalanffy model to analyze growth data of the pond snail Lymnaea stagnalis, we detected food limitation in the early juvenile phase. The snails were held under conditions proposed for a standardized test protocol, which prescribes lettuce as food source. Additional experiments showed that juveniles grow considerably faster when fed with fish flakes. The model is based on Dynamic Energy Budget (DEB) theory, which allows for mechanistic interpretation of toxic effects in terms of changes in energy allocation. In a simulation study with the DEB model, we compared the effects of three hypothetical toxicants in different feeding situations. The initial food limitation when fed with lettuce always intensified the effect of the toxicants. When fed with fish flakes, the predicted effect of the toxicants was less pronounced. From this study, we conclude that (i) the proposed test conditions for L. stagnalis are not optimal, and require further investigation, (ii) fish flakes are a better food source for juvenile pond snails than lettuce, (iii) analyzing data with a mechanistic modeling approach such as DEB allows identifying deviations from constant conditions, (iv) being unaware of food limitation in the laboratory can lead to an overestimation of toxicity in ecotoxicological tests.

Elastic intramedullary nailing as a complement to Ilizarov's method for forearm lengthening: a comparative pediatric prospective study

PURPOSE

Most of the techniques for forearm lengthening involve external fixation to achieve stability and provide progressive distraction. We introduce the use of elastic stable intramedullar nailing (ESIN) in combination with external circular assembly for the procedure. The purpose of this prospective study was to compare Ilizarov's classical technique with this combined technique.

METHODS

Fifty-seven patients, with forearm length discrepancies or deformities either congenital or acquired, were prospectively followed-up. Patients were divided in two groups: 35 had only external fixation, and 22 had external fixation-ESIN combined techniques. Patients were assessed for clinical and radiographic outcome with a mean follow-up of 21 months after external device removal.

RESULTS

Overall lengthening was 45.0mm. Healing index (HI) was 22.2d/cm with the combined technique, and 32.0 d/cm with external fixation. HI was 30% better when ESIN was used, for congenital and for overall cases. Combined technique has a lower complication rate.

CONCLUSION

Although forearm lengthening still remains a time-consuming procedure, ESIN can shorten external fixator wearing time. No additional complication occurred and bony complications seem to be limited by the nails. We recommend this technique, which we now use for most of our patients undergoing limb lengthening.

LEVEL OF EVIDENCE

Level IV.

Is combining massive bone allograft with free vascularized fibular flap the children's reconstruction answer to lower limb defects following bone tumour resection?

PURPOSE OF THE STUDY

Bone tumours are frequent conditions in children, and their surgical resection may lead to extensive defects which reconstruction is often challenging. Indeed, local conditions do not promote bone healing, and the achieved surgical result requires to be life-lasting. Capanna suggested a reconstruction technique combining massive allograft and free vascularized fibular flap. The first one is intended to withstand mechanical stress, and the second one offers biological and vascular support to improve bone healing and prevent infections.

MATERIAL AND METHODS

We report our experience with this technique when applied to the lower limb in a prospective study including seven children, with a mean follow-up of 44 months.

RESULTS

Bone healing was achieved by one single procedure in 85.7% of the cases, usually 7 months after surgery. Six out of seven patients achieved a final and long-lasting outcome, five of them following a simple surgical history. Partial weight-bearing was post-operatively allowed at about 2 months, full weight-bearing was initiated at about 5.5 months.

DISCUSSION

A low complication rate was reported despite the extent of the disease and the type of the surgical procedure. Capanna's combined reconstructive technique appears very efficient in the management of massive bone defects following tumour resection in children's lower limb.

LEVEL OF EVIDENCE

Level IV. Retrospective therapeutic study.

Prediction of daphnid survival after in situ exposure to complex mixtures

We applied a mechanistically based model to predict the effects of complex mixtures as occurring in the field on the survival of Daphnia magna. We validated the model by comparing predicted survival with observed survival of in situ exposed laboratory cultured daphnids to polluted surface waters, in which over 90 chemical contaminants were measured. Using the chemical composition of the surface water at each sampling site, we calculated whether or not any of the individual or shared no effect concentrations were exceeded. If they were, we calculated the effect on survival. In 34 out of 37 cases (92%) we correctly predicted daphnid survival in surface waters. In the case of mortality we could also appoint the compound or group of compounds causing the effect. It is concluded that the proposed mechanistically based model accurately predicts effects on daphnids in the field, given the chemical composition of the water. Hence it is a powerful tool to link the chemical and ecological status of surface waters.

A pictorial overview of ultrasound of tendon disorders

A variety of terms that is often confusing is used to describe tendon changes at ultrasound.The classification of tendon disorders is often based on a combination of clinical and imaging findings. We present an overview of different categories of tendon disorders where ultrasound may contribute to the diagnosis and classification. We suggest the following categories: overuse, traumatic, inflammatory, and metabolic.The differentiation is not always possible and the importance of clinical data must be taken into account.The spectrum of tendon abnormalities is illustrated with clinical examples.

Scaling relationships based on partition coefficients and body sizes have similarities and interactions

The LC(50) of compounds with a similar biological effect, at a given exposure period, is frequently plotted log-log against the octanol-water partition coefficient and a straight line is fitted for interpolation purposes. This is also frequently done for physiological properties, such as the weight-specific respiration rate, as function of the body weight of individuals. This paper focuses on the remarkable observation that theoretical explanations for these relationships also have strong similarities. Both can be understood as result of the covariation of the values of parameters of models of a particular type for the underlying processes, while this covariation follows logically from the model structure. The one-compartment model for the uptake and elimination of compounds by organisms is basic to the BioConcentration Factor (BCF), or the partition coefficient; the standard Dynamic Energy Budget model is basic to the (ultimate) body size. The BCF is the ratio of the uptake and the elimination rates; the maximum body length is the ratio of the assimilation (i.e. uptake of resources) and the maintenance (i.e. use of resources) rates. This paper discusses some shortcomings of descriptive approaches and conceptual aspects of theoretical explanations. The strength of the theory is in the combination of why metabolic transformation depends both on the BCF and the body size. We illustrate the application of the theory with several data sets from the literature.

The relationship between elimination rates and partition coefficients

Rate constants for uptake and elimination of chemicals in organisms are often related to partition coefficients (typically the octanol-water partition coefficient). We show that the well-mixed one-compartment model for toxico-kinetics implies that the elimination rate is inversely proportional to the square root of the partition coefficient. When chemical exchange is limited by diffusion in the boundary layers adjacent to the interface, two-film models are appropriate, which have more complex implications for the relationships between the exchange rates and the partition coefficient. We also show that the popular steady-flux approximation of the two-film model is not a conceptual generalization of the one-compartment model, although it shares the first-order kinetics. We compare the kinetics of a series of models with an increasing number of well-mixed compartments for exchange, such that the two-film model results for an infinite number of compartments. The latter model formulation in terms of partial differential equations, and more in particular its boundary condition at the interface of the two media, is believed to be new. In the steady-flux approximation and in the model with single well-mixed boundary layers and low diffusivities, the elimination rate depends hyperbolically on the partition coefficient. The available data for abiotic systems (SPME fibers) supports a hyperbolic relationship, whereas the data for aquatic biota are less discriminating between a hyperbolic or a square root relationship with the partition coefficient. The daphnia data showed less scatter than the fish data, possibly due to the small variance in body sizes, since elimination rates are inversely proportional to body length. The square root relationship fitted these data best.

Modeling ingestion as an exposure route for organic chemicals in earthworms (Oligochaeta)

Earthworms take up chemicals from both soil pore water and food, but the quantitative contribution of each route is unclear. In this paper, a model is presented for the accumulation of organic chemicals in earthworms, including a compartment for the gut contents. A Monte Carlo screening method is used to calibrate the model simultaneously to four experimental data sets for hexachlorobenzene (HCB) in the compost worm (Eisenia andrei). The calibration procedure shows that the dominant route of exposure is across the gut wall. Nevertheless, predicted body residues of HCB are generally no more than 20% higher than the estimate based on equilibrium partitioning (EP), independent of the uncertainties in all of the model parameters. The deviation from EP is mainly related to the digestive efficiency of the earthworm. Body residues are not expected to exceed the EP estimate by more than 50% for other chemicals or other earthworm species. The model is particularly useful when the organism's food source is specifically contaminated and EP cannot be applied.

Monitoring approaches to assess bioaccessibility and bioavailability of metals: matrix issues

Bioavailability and bioaccessibility are complex issues that determine whether or not adverse effects are to be expected when organisms or plants are exposed to contaminants. Clearly, the determinants of bioavailability and bioaccessibility must be understood if one is to monitor or, ultimately, predict the effects of metals. On the basis of a dynamic conceptual model, this article offers an analysis of the physicochemical and biological determinants underlying bioavailability and bioaccessibility. This analysis is used as the basis for a general monitoring strategy for assessing potentially and actually available and accessible metal fractions in the environmental matrices of water, soil, and sediment. We conclude that, lack of a universal expression of bioavailable and bioaccessible metal fractions precludes the presentation of a detailed monitoring strategy that is broadly applicable. Instead, we recommend that a critical assessment of the endpoints of determination become the basis for a need-specific monitoring strategy.

Opportunities for a probabilistic risk assessment of chemicals in the European Union

In risk assessment of new and existing substances, it is current practice to characterise risk using a deterministic quotient of the exposure concentration, or the dose, and a no-effect level. A sense of uncertainty is tackled by introducing worst-case assumptions in the methodology. Since this procedure leads to an assessment with an unknown degree of conservatism, it is advisable to deal quantitatively with uncertainties. This paper discusses the advantages and possibilities of a probabilistic risk assessment framework, illustrated with an example calculation. Furthermore, representatives of EU Member States and the chemical industry were interviewed to find out their views on applying uncertainty analysis to risk assessment of industrial chemicals.

Impact of metal pools and soil properties on metal accumulation in Folsomia candida (Collembola)

Soil-dwelling organisms are exposed to metals in different ways. Evidence exists for predominant pore water uptake of metals by soft-bodied oligochaete species. In the present research, uptake kinetics of metals and the metalloid As by the semi-soft-bodied springtail Folsomia candida were studied, for which uptake via the pore water is less obvious. Springtails were exposed in 16 field soils and in metal-spiked artificial Organization for Economic Cooperation and Development (Paris, France) soil (OECD soil). Subsequently, accumulation parameters were statistically related to soil metal pools and soil properties. In Cd-spiked OECD soil, internal Cd levels were linearly related to external Cd concentrations, whereas the springtails maintained fixed internal levels of Cu and Zn regardless of spiked concentrations. In the field soils, all body concentrations of the elements As, Cr, and Ni were below detection limit. The essential metals Cu and Zn were presumably regulated, and no influence of soil characteristics could be demonstrated. For Cd and Pb, accumulation patterns were correlated mainly to solid-phase soil characteristics. The presence of these explanatory variables in the multiple correlations suggests that an uptake mechanism that is solely determined by pore water concentrations should not be taken as a universally applicable principle in risk assessments of metals for soil invertebrates. Cadmium in OECD soils was more available for uptake than in the field soils. The difference remained when extractability was taken into account. The results suggest that experiments in OECD soil cannot be used directly in risk assessment for nonessential metals (at least for F. candida), although a reduction of uncertainties in metal risk assessment can be reached by consistent use of body residues rather than external concentrations.

Quantification of metal bioavailability for lettuce (Lactuca sativa L.) in field soils

Understanding metal bioavailability of plants in soils requires, apart from physiological processes and symbiosis with arbuscular mycorrhizal fungi, the consideration of the chemical availability in the soil solution (the intensity of the toxic exposure) and the soil's capacity to supply the metal (capacity). In this contribution we report on the time-dependent accumulation of As, Cd, Cr, Cu, Ni, Pb, and Zn in lettuce (Lactuca sativa L.). Bioassays with 17 Dutch field soils and two artificially metal-contaminated soils were carried out. Phytotoxicity was observed in soils with pH (pore water) <4.8. Metal uptake is shown to be both metal- and soil-dependent and strongly depends on the amount of water the plant transpired and the available concentration in the water. No net accumulation of As, Pb, Ni, and especially Cr was observed in most soils tested. The latter observation is in agreement with findings of Zayed et al. (Planta, 1998 206:293-299), who reported that translocation of Cr from roots to shoots is extremely limited. Internal Cd levels in the plants varied greatly among soils, whereas plant tissue concentrations of Zn and especially Cu appear to be regulated at more or less fixed levels. The 0.01 M CaCl(2)-extractable metal pool provides the best descriptor for the capacity of the soil to supply Cd and Zn. This enabled the development of models that are suited to predict Zn and Cd uptake by lettuce in both field soils (weathered soils) and soils to which metal salts were added, which is common practice in toxicity testing of chemicals. It is concluded that of all metals included in this study, Cd is the metal of most concern due to bioaccumulation through the soil-plant-animal food chain as Cd is the only metal that might pose human or animal health risks at plant tissue concentrations that are not directly phytotoxic. Finally, application of the models for risk assessment purposes is discussed.

Priority assessment of toxic substances in life cycle assessment. Part II: assessing parameter uncertainty and human variability in the calculation of toxicity potentials

Toxicity potentials are standard values used in life cycle assessment (LCA) to enable a comparison of toxic impacts between substances. This paper presents the results of an uncertainty assessment of toxicity potentials that were calculated with the global nested multi-media fate, exposure and effects model USES-LCA. The variance in toxicity potentials resulting from input parameter uncertainties and human variability was quantified by means of Monte Carlo analysis with Latin Hypercube sampling (LHS). For Atrazine, 2,3,7,8-TCDD and Lead, variation, expressed by the ratio of the 97.5%-ile and the 2.5%-ile, ranges from about 1.5 to 6 orders of magnitude. The major part of this variation originates from a limited set of substance-specific input parameters, i.e. parameters that describe transport mechanisms, substance degradation, indirect exposure routes and no-effect concentrations. Considerable correlations were found between the toxicity potentials of one substance, in particular within one impact category. The uncertainties and correlations reported in the present study may have a significant impact on the outcome of LCA case studies.

Priority assessment of toxic substances in life cycle assessment. Part I: calculation of toxicity potentials for 181 substances with the nested multi-media fate, exposure and effects model USES-LCA

Toxicity potentials are standard values used in life cycle assessment (LCA) to enable a comparison of toxic impacts between substances. In most cases, toxicity potentials are calculated with multi-media fate models. Until now, unrealistic system settings were used for these calculations. The present paper outlines an improved model to calculate toxicity potentials: the global nested multi-media fate, exposure and effects model USES-LCA. It is based on the Uniform System for the Evaluation of Substances 2.0 (USES 2.0). USES-LCA was used to calculate for 181 substances toxicity potentials for the six impact categories freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, freshwater sediment ecotoxicity, marine sediment ecotoxicity, terrestrial ecotoxicity and human toxicity, after initial emission to the compartments air, freshwater, seawater, industrial soil and agricultural soil, respectively. Differences of several orders of magnitude were found between the new toxicity potentials and those calculated previously.

Relating environmental availability to bioavailability: soil-type-dependent metal accumulation in the oligochaete Eisenia andrei

Body residues are often better estimates of the amount of a chemical at the sites of toxic action in an organism than ambient soil concentrations, because bioavailability differences among soils are explicitly taken into account in considerations of body residues. Often, however, insufficient attention is paid to the rate and extent at which tissue concentrations respond to soil concentrations and soil characteristics. In this contribution the impact of soil characteristics on the environmental bioavailability of heavy metals for the oligochaete worm Eisenia andrei is reported. Uptake of As, Cd, Cr, Cu, Ni, Pb, and Zn in 20 Dutch field soils and in OECD artificial soil was quantified as a function of time. Internal metal concentrations varied less than the corresponding external levels. Metal uptake and elimination were both metal- and species-dependent. Worms typically attained steady-state concentrations rapidly for Cr, Cu, Ni, and Zn. Internal concentrations similar to those in the cultivation medium, linearly increasing body concentrations, or steady-state internal concentrations well above those in the cultivation medium were found for As, Cd, and Pb. Multivariate expressions were derived to describe uptake rate constants, steady-state concentrations, and bioaccumulation factors as a function of soil characteristics. Soil acidity is the most important solid-phase characteristic modulating the availability of As, Cd, and Pb. Although additional semimechanistic calculations yielded evidence of pore-water-related uptake of Cd and Pb modulated by competition between H(+) and metal ions at the active sites of the membranes, the findings for Cr, Cu, Ni, and Zn point to additional influences, among which is probably regulation.

Prediction of metal bioavailability in Dutch field soils for the oligochaete Enchytraeus crypticus

Current risk assessment procedures ignore that variation in soil properties results in substantial differences for uptake and effects in organisms in different soils. In this contribution is presented the results of a study on the soil-related factors that modulate metal uptake and elimination by the oligochaete worm Enchytraeus crypticus. Uptake of Cd, Cu, Pb, and Zn was quantified in 20 Dutch field soils as a function of time. Uptake rate constants and equilibrium concentrations were estimated using compartment modeling. Internal metal concentrations varied less than the corresponding external levels. Zn and especially Cu provided the most extreme examples of this general behavior, which suggests regulation by the organism. Body residues by Cd increased linearly over time in 11 of the 20 soils studied, whereas in the remaining 9 soils equilibration of internal Cd levels was observed. CaCl2 extraction could be used to discriminate the 9 soils in which there is Pb accumulation from the 11 soils in which bioavailable Pb levels were too low to allow for uptake. Multivariate expressions that describe uptake rate constants and bioaccumulation factors as a function of soil characteristics were derived. pH and cation exchange capacity were the most important parameters. The formulae were very similar to those describing partitioning of metals over the solid and liquid phase of the soils, which suggests pore water-mediated uptake. A semi-mechanistic approach yielded further evidence of pore water-related uptake, modulated by competition between H+ and metal ions at the active sites of the membranes.