In vitro evaluation of different protective techniques to reduce titanium particle contamination during implantoplasty

OBJECTIVES

Our aim is to study titanium remains in a bone model during standardized implantoplasty under different isolation and protective modalities.

MATERIAL AND METHODS

Forty implants were placed in artificial spongy bone blocks mimicking a horizontal bone loss and implant neck protrusion of 5 mm. Samples were randomly divided into four groups (n = 10), which were treated as follows: rubber dam (A), a dental adhesive paste (B), bone wax (C), and an unprotected positive control (D). Implantoplasty was performed using carbide and diamond burs under strict water cooling and standardized suction. After removal of the respective isolation materials, the bone blocks were thoroughly rinsed with tap water for 3 min and titanium chips were collected using a filter integrated in the model. The filter paper was removed and dissolved in 37% hydrochloric acid for 2 h at 120 °C and the titanium remnants were quantified using atomic absorption spectrometry.

RESULTS

None of the test groups were able to completely prevent titanium particle contamination. Rubber dam (691 ± 249 µg) and bone wax (516 ± 157 µg) were found to be significantly more protective than the positive control (2313 ± 747 µg) (p < 0.001) with respect to the amount of titanium particles that remained in the bone model after implantoplasty. The adhesive paste group (1863.5 ± 538 µg) was not significantly different from the positive control (p = 0.19).

CONCLUSIONS

Despite some limitations of the present study, titanium particles resulting from a standardized implantoplasty can be assumed to be significantly reduced when the tissues/bone were protected with rubber dam and bone wax, or a combination, depending on individual accessibility.

CLINICAL RELEVANCE

Tissue protective measures to reduce or avoid particle contamination during implantoplasty is possible and should be considered and further clinically assessed to avoid iatrogenic inflammatory reactions.

Increased posterior tibial slope is an independent risk factor of anterior cruciate ligament reconstruction graft rupture irrespective of graft choice

INTRODUCTION

Anterior cruciate ligament (ACL) reconstruction failure remains a commonly seen complication despite advances in technique and graft options. Recently, several studies have shown that the inclination of the tibial plateau in the sagittal plane affects the stability of the knee joint. The purpose of this study was to determine if an increased posterior slope of the tibia is associated with failure of ACL reconstruction irrespective of the graft used.

METHODS

From June 2002 to August 2003, a total of 100 patients with a symptomatic ACL-deficient knee were randomised to receive either a hamstring autograft or posterior tibialis allograft. All allografts were from a single tissue bank, aseptically processed, and fresh-frozen without terminal irradiation. ACL graft failures requiring reoperation with a minimum of 10-year follow-up were identified via telephone survey. Lateral radiographs of the knee of all patients were reviewed, and the slope of the tibia was measured using a standardised technique. Two fellowship-trained orthopaedic sports medicine specialists, one board-certified general orthopaedic surgeon, and two fellowship-trained musculoskeletal radiologists measured the tibial slope in all patients.

RESULTS

At a minimum of 10-year follow-up, there were four (8.3%) autograft and 13 (26.5%) allograft failures that required revision reconstruction. The overall average tibial slope of the nonfailure cohort was 9.4°. The overall average tibial slope of the failure cohort was 11.9° (P ​= ​0.0002). The average slope of the allograft failures was 11.5°compared with an average slope of 9.6° in the nonfailures (P ​= ​0.01). The average slope of the autograft failures was 13.1° compared with 9.3° in the nonfailures (P ​= ​0.011). The mean difference in tibial slope measurements was 0.665 (95% confidence interval: 0.569-0.750). The interrater reliability, as measured by the intraclass correlation coefficient, for tibial slope was 0.898 (95% confidence interval: 0.859-0.928). The Cronbach α was 0.904.

CONCLUSION

In a prospective, randomised trial of ACL reconstructions using either autograft or allograft, failures were associated with a significantly increased slope of the tibia compared with the nonfailures at 10-year follow-up.

Historical changes in plant water use and need in the continental United States

A robust method for characterizing the biophysical environment of terrestrial vegetation uses the relationship between Actual Evapotranspiration (AET) and Climatic Water Deficit (CWD). These variables are usually estimated from a water balance model rather than measured directly and are often more representative of ecologically-significant changes than temperature or precipitation. We evaluate trends and spatial patterns in AET and CWD in the Continental United States (CONUS) during 1980-2019 using a gridded water balance model. The western US had linear regression slopes indicating increasing CWD and decreasing AET (drying), while the eastern US had generally opposite trends. When limits to plant performance characterized by AET and CWD are exceeded, vegetation assemblages change. Widespread increases in aridity throughout the west portends shifts in the distribution of plants limited by available moisture. A detailed look at Sequoia National Park illustrates the high degree of fine-scale spatial variability that exists across elevation and topographical gradients. Where such topographical and climatic diversity exists, appropriate use of our gridded data will require sub-setting to an appropriate area and analyzing according to categories of interest such as vegetation communities or across obvious physical gradients. Recent studies have successfully applied similar water balance models to fire risk and forest structure in both western and eastern U.S. forests, arid-land spring discharge, amphibian colonization and persistence in wetlands, whitebark pine mortality and establishment, and the distribution of arid-land grass species and landscape scale vegetation condition. Our gridded dataset is available free for public use. Our findings illustrate how a simple water balance model can identify important trends and patterns at site to regional scales. However, at finer scales, environmental heterogeneity is driving a range of responses that may not be simply characterized by a single trend.

Multistate occupancy modeling improves understanding of amphibian breeding dynamics in the Greater Yellowstone Area

Discerning the determinants of species occurrence across landscapes is fundamental to their conservation and management. In spatially and climatologically complex landscapes, explaining the dynamics of occurrence can lead to improved understanding of short- vs. long-term trends and offer novel insight on local vs. regional change. We examined the changes in occupancy for two species of anurans with different life histories over a decade using hundreds of wetland sites in Yellowstone and Grand Teton National Parks. To account for the joint dynamics of wetland drying and amphibian breeding, we adopted a multistate occupancy model as a means to investigate mechanistic relationships of observed occurrence patterns with climatological drivers of wetland hydrologic variability. This approach allowed us to decompose occupancy dynamics into habitat changes caused by wetland drying and amphibian breeding activity, conditional on available water and previous breeding state. Over our 10-yr time series, we observed considerable variability in climate drivers and the proportion of dry wetlands. Boreal chorus frogs (Pseudacris maculata) were more responsive to changes in wetland inundation status than Columbia spotted frogs (Rana luteiventris), as indicated by higher breeding colonization probabilities under favorable (wet) conditions. Both species had high probabilities of breeding persistence in permanently inundated wetlands with prior breeding. Despite the absence of multi-year drought in our time series, mechanistic relationships described here offer insights on how future climate variation may result in reduced and/or shifted occurrence patterns for pond-breeding anurans in the Greater Yellowstone Area. Further, our modeling approach may prove valuable in evaluating determinants of occurrence for other species that are dependent on wetlands or other dynamic habitats.

Morning glory disc anomaly with an ipsilateral enlargement of the optic nerve pathway

PURPOSE

To report three patients with an unilateral morning glory disc anomaly in association with an ipsilateral mild thickening of the optic nerve.

METHODS

Three children with a morning glory disc anomaly underwent a magnetic resonance imaging (MRI) of the brain. Ophthalmological, genetic and MRI findings at follow-up are reported. A literature search on the association of morning glory anomaly in association with optic nerve glioma is reported.¹ RESULTS: Three children with an unilateral morning glory anomaly and ipsilateral poor visual acuity were found to have an ipsilateral mild optic nerve enlargement on brain MRI. At serial MRI scanning, there was no progression of this finding.

CONCLUSIONS

The morning glory disc anomaly is a rare congenital malformation of the optic disc. It can be associated with central nervous system abnormalities. The association with an optic nerve glioma has been described once before.¹ Our three cases confirm the possible association between a morning glory disc anomaly and an ipsilateral optic nerve enlargement. Serial MRI showed no growth at follow-up. The awareness of this association by the ophthalmologists is important.

Echinococcus multilocularis--a zoonosis of anthropogenic environments?

Transmission of the fox tapeworm Echinococcus multilocularis, the causative agent of human alveolar echinococcosis, is known to depend on various environmental factors which are subject to human influence. Epidemiological data suggest that in most endemic regions anthropogenic landscape changes (e.g. deforestation and agricultural practices) have led to more favourable conditions for the parasite's animal hosts, especially arvicolid rodents, thereby increasing the risk for parasite transmission and human disease. Examples are the conversion of forests or crop fields into meadows and pastures in Europe, China and North America, and overgrazing of natural grassland in central Asia. Other anthropogenic factors include interference with host population densities by wildlife disease control, changing hunting pressure and provision of new habitats, e.g. in urban areas. Domestic dogs may, under certain conditions, get involved in the otherwise largely wildlife-based transmission, and thereby greatly increase the infection pressure to humans. The introduction of neozootic host species may increase transmission, or even initiate the parasite's life-cycle in previously non-endemic regions. Lastly, the parasite itself may be accidentally introduced into non-endemic areas, if suitable host populations are present (e.g. in northern Japan).