Mechanical characterization of fourth generation composite humerus

Mechanical data on upper extremity surrogate bones, supporting use as biomechanical tools, is limited. The objective of this study was to characterize the structural behaviour of the fourth-generation composite humerus under simulated physiologic bending, specifically, stiffness, rigidity, and mid-diaphysial surface strains. Three humeri were tested in four-point bending, in anatomically defined anteroposterior (AP) and mediolateral (ML) planes. Stiffness and rigidity were derived using load–displacement data. Principal strains were determined at the anterior, posterior, medial, and lateral surfaces in the humeral mid-diaphysial transverse plane of one specimen using stacked rosettes. Linear structural behaviour was observed within the test range. Average stiffness and rigidity were greater in the ML (918 ± 18 N/mm; 98.4 ± 1.9 Nm2) than the AP plane (833 ± 16 N/mm; 89.3 ± 1.6 Nm2), with little inter-specimen variability. The ML/AP rigidity ratio was 1.1. Surface principal strains were similar at the anterior (5.41 µε/N) and posterior (5.43 µε/N) gauges for AP bending, and comparatively less for ML bending, i.e. 5.1 and 4.5 µε/N, at the medial and lateral gauges, respectively. This study provides novel strain and stiffness data for the fourth-generation composite humerus and also adds to published construct rigidity data. The presented results support the use of this composite bone as a tool for modelling and experimentation.

Plant response traits mediate the effects of subalpine grasslands on soil moisture

* In subalpine grasslands, changes in abiotic conditions with decreased management intensity alter the functional composition of plant communities, leading to modifications of ecosystem properties. Here, it is hypothesized that the nature of plant feedbacks on soil moisture is determined by the values of key traits at the community level. * As community functional parameters of grasslands change along a gradient of land uses, those traits that respond most to differences in abiotic conditions produced by land use changes were identified. A vegetation removal experiment was then conducted to determine how each plant community affected soil moisture. * Soil moisture was negatively correlated with community root length and positively correlated with canopy height, whereas average leaf area was associated with productivity. These traits were successfully used to predict the effects on soil moisture of each plant community in the removal experiment. This result was validated using data from an additional set of fields. * These findings demonstrate that the modification of soil moisture following land use change in subalpine grasslands can be mediated through those plant functional traits that respond to water availability.

Cement penetration and primary stability of the femoral component after impaction allografting

This study explored the relationship between the initial stability of the femoral component and penetration of cement into the graft bed following impaction allografting.

Impaction allografting was carried out in human cadaveric femurs. In one group the cement was pressurised conventionally but in the other it was not pressurised. Migration and micromotion of the implant were measured under simulated walking loads. The specimens were then cross-sectioned and penetration of the cement measured.

Around the distal half of the implant we found approximately 70% and 40% of contact of the cement with the endosteum in the pressure and no-pressure groups, respectively. The distal migration/micromotion, and valgus/varus migration were significantly higher in the no-pressure group than in that subjected to pressure. These motion components correlated negatively with the mean area of cement and its contact with the endosteum.

The presence of cement at the endosteum appears to play an important role in the initial stability of the implant following impaction allografting.

Pregnancy in rheumatology patients exposed to anti-tumour necrosis factor (TNF)- therapy

OBJECTIVES

Anti-tumour necrosis factor (TNF)-alpha therapies are considered category B drugs for pregnancy. Although sometimes prescribed to women of reproductive age, data in humans are limited with regard to safety for a developing fetus. The objectives of the present article are to report experience of anti-TNF-alpha use in pregnancy, and review the international literature.

METHODS

Since 1999 the present authors have used anti-TNF-alpha (infliximab, etanercept, adalimumab) to treat patients with various chronic rheumatic conditions. All patients were prospectively followed during their treatment time and data were systematically collected.

RESULTS

In a group of 442 patients treated with anti-TNF, three women with RA unexpectedly became pregnant One treated with etanercept chose a therapeutic termination at two and a half months, despite of any ultrasound anomaly, and satisfactory fetal growth. The other two patients (one with adalimumab exposure and one with etanercept exposure) delivered healthy infants. The following perinatal complications were observed: prematurity, neonatal jaundice, neonatal urinary Escherichia coli infection and adrenal congenital hyperplasia of probable hereditary origin.

CONCLUSIONS

To date, there is no evidence that TNF-alpha antagonists are associated with embryo toxicity, teratogenicity or increased pregnancy loss. However, caution should be taken when anti-TNF agents are used during pregnancy, as human experience is still extremely limited, particularly in patients with rheumatic diseases among whom there are several alarming reports. The potential risk should be balanced against the known risks associated with DMARDs and steroid therapy. Large registries will be necessary before firm conclusions can be drawn.

Ghrelin gastrokinetic action in patients with neurogenic gastroparesis

Ghrelin has been shown to accelerate gastric emptying in animals where its effect appeared mediated through the vagus nerve. We aimed to verify the gastrokinetic capacity of ghrelin in human. Patients with gastroparesis attributed to a neural dysregulation by diabetes (n = 5) or surgical vagotomy (n = 1) were evaluated. The emptying of a test meal (420 kcal) was determined by the C13 octanoic acid breath test. Saline or synthetic ghrelin 1-4 microg/kg were given in 1 min bolus at the end of the meal. T-lag and T-1/2 were shorter during ghrelin than during saline administration [33 +/- 5 min versus 65 +/- 14 min (p < 0.01) and 119 +/- 6 min versus 173 +/- 38 min (p < 0.001)]. Ghrelin injection therefore accelerated gastric emptying of a meal in humans even in presence of a deficient gastric innervation.

Safety of anti-TNF-alpha therapy in rheumatoid arthritis and spondylarthropathies with concurrent B or C chronic hepatitis

OBJECTIVE

To assess the safety of anti-tumour necrosis factor (TNF)-alpha therapy in patients with rheumatoid arthritis (RA) or spondylarthropathies (SA) and concurrent chronic hepatitis B or C.

METHODS

Records concerning 480 outpatients attending the Rheumatology Department of the University Hospital of Nice (France) for RA or SA were retrospectively reviewed for the duration of disease, treatment, serological status and biological data.

RESULTS

Six relevant cases were identified: two of RA with chronic hepatitis B; one of SA with chronic hepatitis B and three of RA with chronic hepatitis C. Five patients had received etanercept and one infliximab; two had been given adalimumab after an unsuccessful trial of etanercept. Patients with concurrent chronic hepatitis B were also given lamivudine. In none of the cases had changes in serum aminotransferases or viral load been reported.

CONCLUSION

The use of anti-TNF-alpha therapy (plus lamivudine in the presence of concurrent underlying hepatitis B viral infection) appeared to be safe in that it had no effect on serum aminotransferases and/or viral load. However, repeated monitoring is necessary throughout the treatment period.