Stability of Cefazolin in Polyisoprene Elastomeric Infusion Devices

Purpose

The aim was to investigate the stability of cefazolin in elastomeric infusion devices.

Dry granular flows can generate surface features resembling those seen in Martian gullies

Over the past decade or more, contradictory evidence of Martian climate, indicating that surface temperatures seldom if ever approach the melting point of water at midlatitudes, and geomorphic features, consistent with liquid flows at these same latitudes, have proven difficult to reconcile. In this article, we demonstrate that several features of liquid-erosional flows can be produced by dry granular materials when individual particle settling is slower than characteristic debris flow speeds. Since the gravitational acceleration on Mars is about one-third that on Earth, and since particle settling speeds scale with gravity, we propose that some (although perhaps not all) Martian geomorphological features attributed to liquid flows may in fact be associated with dry granular flows in the presence of reduced gravity.     

White matter alteration and cerebellar atrophy are hallmarks of brain MRI in alpha-mannosidosis

ObjectiveDespite profound neurological symptomatology there are only few MRI studies focused on the brain abnormalities in alpha-mannosidosis (AM). Our aim was to characterize brain MRI findings in a large cohort of AM patients along with clinical manifestations.MethodsTwenty-two brain MRIs acquired in 13 untreated AM patients (8 M/5F; median age 17 years) were independently assessed by three experienced readers and compared to 16 controls.ResultsFocal and/or diffuse hyperintense signals in the cerebral white matter were present in most (85%) patients. Cerebellar atrophy was common (62%), present from the age of 5 years. Progression was observed in two out of 6 patients with follow-up scans. Cortical atrophy (62%) and corpus callosum thinning (23%) were already present in a 13-month-old child. The presence of low T₂ signal intensity in basal ganglia and thalami was excluded by the normalized signal intensity profiling. The enlargement of perivascular spaces in white matter (38%), widening of perioptic CSF spaces (62%), and enlargement of cisterna magna (85%) were also observed. Diploic space thickening (100%), mucosal thickening (69%) and sinus hypoplasia (54%) were the most frequent non-CNS abnormalities.ConclusionWhite matter changes and cerebellar atrophy are proposed to be the characteristic brain MRI features of AM. The previously reported decreased T₂ signal intensity in basal ganglia and thalami was not detected in this quantitative study. Rather, this relative MR appearance seems to be related to the diffuse high T₂ signal in the adjacent white matter and not the gray matter iron deposition that has been hypothesized.     

Hamstrings Stiffness and Landing Biomechanics Linked to Anterior Cruciate Ligament Loading

Context:

Greater hamstrings stiffness is associated with less anterior tibial translation during controlled perturbations. However, it is unclear how hamstrings stiffness influences anterior cruciate ligament (ACL) loading mechanisms during dynamic tasks.

Objective:

To evaluate the influence of hamstrings stiffness on landing biomechanics related to ACL injury.

Design:

Cross-sectional study.

Setting:

Research laboratory.

Patients or Other Participants:

A total of 36 healthy, physically active volunteers (18 men, 18 women; age = 23 ± 3 years, height = 1.8 ± 0.1 m, mass = 73.1 ± 16.6 kg).

Intervention(s):

Hamstrings stiffness was quantified via the damped oscillatory technique. Three-dimensional lower extremity kinematics and kinetics were captured during a double-legged jump-landing task via a 3-dimensional motion-capture system interfaced with a force plate. Landing biomechanics were compared between groups displaying high and low hamstrings stiffness via independent-samples t tests.

Main Outcome Measure(s):

Hamstrings stiffness was normalized to body mass (N/m·kg⁻¹). Peak knee-flexion and -valgus angles, vertical and posterior ground reaction forces, anterior tibial shear force, internal knee-extension and -varus moments, and knee-flexion angles at the instants of each peak kinetic variable were identified during the landing task. Forces were normalized to body weight, whereas moments were normalized to the product of weight and height.

Results:

Internal knee-varus moment was 3.6 times smaller in the high-stiffness group (t₂₂ = 2.221, P = .02). A trend in the data also indicated that peak anterior tibial shear force was 1.1 times smaller in the high-stiffness group (t₂₂ = 1.537, P = .07). The high-stiffness group also demonstrated greater knee flexion at the instants of peak anterior tibial shear force and internal knee-extension and -varus moments (t₂₂ range = 1.729–2.224, P < .05).

Conclusions:

Greater hamstrings stiffness was associated with landing biomechanics consistent with less ACL loading and injury risk. Musculotendinous stiffness is a modifiable characteristic; thus exercises that enhance hamstrings stiffness may be important additions to ACL injury-prevention programs.Key Words: viscoelastic, musculotendinous, valgus, anterior tibial shear force

Key Points

• Individuals with greater hamstrings stiffness displayed more favorable landing biomechanics for anterior cruciate ligament (ACL) loading and injury risk than individuals with less hamstrings stiffness as evidenced by smaller frontal-plane knee moments and a more-flexed knee at the instants of critical biomechanical knee events.
• Greater hamstrings stiffness was associated with smaller anterior tibial shear forces.
• A high level of hamstrings stiffness may limit ACL injury risk by limiting frontal- and sagittal-plane ACL-loading mechanisms.

Anterior cruciate ligament (ACL) injury commonly occurs during landing,¹ and researchers have suggested that a landing biomechanics profile consisting of large ground reaction forces, anterior tibial shear force, knee-valgus angle, and external knee-flexion and -valgus moments increases ACL loading.^2–4 A more-extended knee during landing exacerbates this profile, whereas a more-flexed knee decreases these variables,^4–6 likely limiting ACL loading and injury risk. For example, Blackburn and Padua⁵ demonstrated that increasing knee-flexion angle during landing reduced ground reaction forces. Similarly, Pollard et al⁶ categorized participants into high- and low-flexion groups based on performance of a landing task and reported smaller knee-valgus angles and moments in the high-flexion group.Stiffness quantifies the resistance of the musculotendinous unit to lengthening, and hamstrings stiffness may have important implications for ACL loading and injury risk. Greater hamstrings stiffness is associated with greater function in ACL-deficient individuals.⁷ During controlled perturbations, healthy individuals with greater hamstrings stiffness also display less anterior tibial translation, which is an arthrokinematic motion that directly loads the ACL.⁸ Given that anterior tibial translation results from anterior tibial shear force, greater hamstrings stiffness seemingly would resist anterior tibial shear force during landing more effectively than less hamstrings stiffness. Greater hamstrings stiffness also is correlated with less hamstrings flexibility.⁹ This heightened resistance to knee extension may lead to a more flexed knee during landing, producing more favorable landing biomechanics for ACL loading and injury risk. This notion is supported by Boden et al,¹ who reported that participants with ACL injuries displayed greater hamstrings flexibility than an uninjured cohort, suggesting that “above-average” hamstrings flexibility and, therefore, less hamstrings stiffness may increase ACL injury risk.Musculotendinous stiffness is a modifiable neuromuscular property^10,11 that could be targeted in ACL injury-prevention programs. Whereas greater hamstrings stiffness appears to limit ACL loading during controlled perturbations,⁸ it is unclear how hamstrings stiffness influences biomechanical ACL-loading mechanisms during dynamic tasks in which ACL injury commonly occurs. Therefore, the purpose of our investigation was to evaluate the influence of hamstrings musculotendinous stiffness on lower extremity kinematics and kinetics during landing. We hypothesized that individuals with greater hamstrings stiffness would display greater knee flexion during landing, resulting in smaller peak ground reaction forces, anterior tibial shear forces, internal knee-extension and -varus moments (ie, the internal/muscular responses to external moments), and knee-valgus angles. We also hypothesized that individuals with greater hamstrings stiffness would display greater knee-flexion angles at the instants of peak kinetics.     

The Immediate Effects of Foam Rolling and Stretching on Iliotibial Band Stiffness: A Randomized Controlled Trial

BackgroundIliotibial Band Syndrome (ITBS) is a common clinical condition likely caused by abnormal compressive forces to the iliotibial band (ITB). Stretching interventions are common in ITBS treatment and may predominantly affect tensor fascia latae (TFL). Another ITBS treatment is foam rolling, which may more directly affect the ITB. Shear wave ultrasound elastography (SWUE) measures real-time soft tissue stiffness, allowing tissue changes to be measured and compared.PurposeTo examine effects of foam rolling and iliotibial complex stretching on ITB stiffness at 0˚ and 10˚ of hip adduction and hip adduction passive range of motion (PROM).Study DesignRandomized controlled trial.MethodsData from 11 males (age = 30.5 ± 9.0 years, Body Mass Index (BMI) = 27.8 ± 4.0) and 19 females (age = 23.5 ± 4.9, BMI = 23.2 ± 2.1) were analyzed for this study. Subjects were randomly assigned to one of three groups: control, stretching, and foam rolling. Shear wave ultrasound elastography measurements included ITB Young’s modulus at the mid-thigh, the distal femur and the TFL muscle belly. ITB-to-femur depth was measured at mid-thigh level. Hip adduction PROM was measured from digital images taken during the movement.ResultsNo significant interactions or main effects were found for group or time differences in ITB Young’s modulus at the three measured locations. The ITB stiffness at the mid-thigh and distal femur increased with 10° adduction, but TFL stiffness did not increase. A main effect for adduction PROM was observed, where PROM increased 0.8˚ post-treatment (p = 0.02).ConclusionA single episode of stretching and foam rolling does not affect short-term ITB stiffness. The lack of ITB stiffness changes may be from an inadequate intervention stimulus or indicate that the interventions have no impact on ITB stiffness.Levels of Evidence1b     

Comparative impacts of two major hurricane seasons on the Neuse River and western Pamlico Sound ecosystems

Ecosystem-level impacts of two hurricane seasons were compared several years after the storms in the largest lagoonal estuary in the U.S., the Albemarle-Pamlico Estuarine System. A segmented linear regression flow model was developed to compare mass-water transport and nutrient loadings to a major artery, the Neuse River Estuary (NRE), and to estimate mean annual versus storm-related volume delivery to the NRE and Pamlico Sound. Significantly less water volume was delivered by Hurricane Fran (1996), but massive fish kills occurred in association with severe dissolved oxygen deficits and high contaminant loadings (total nitrogen, total phosphorus, suspended solids, and fecal bacteria). The high water volume of the second hurricane season (Hurricanes Dennis, Floyd, and Irene in 1999) delivered generally comparable but more dilute contaminant loads, and no major fish kills were reported. There were no discernable long-term adverse impacts on water quality. Populations of undesirable organisms, such as toxic dinoflagellates, were displaced down-estuary to habitats less conducive for growth. The response of fisheries was species-dependent: there was no apparent impact of the hurricanes on commercial landings of bivalve molluscs or shrimp. In contrast, interacting effects of hurricane floodwaters in 1999 and intensive fishing pressure led to striking reductions in blue crabs. Overall, the data support the premise that, in shallow estuaries frequently disturbed by hurricanes, there can be relatively rapid recovery in water quality and biota, and benefit from the scouring activity of these storms.     

Patients' perspectives on the management of emotional distress in primary care settings

Objective  To investigate how important treatment for emotional distress is to primary care patients in general and to primary care patients with depression, and to evaluate the types of mental health interventions they desire. Design  Patient surveys. Setting  Five private primary care practices. Measurements and main results  Patients' desire for treatment of emotional distress and for specific types of mental health interventions were measured, as well as patients' ratings of the impact of emotional distress, the frequency of depressive symptoms, and mental health functioning. Of the 403 patients, 33% felt that it was “somewhat important” and 30% thought it was “extremely important” that their physician tries to help them with their emotional distress. Patient desire for this help was significantly related to a diagnosis of depression (P<.001), perceptions about the impact of emotional distress (p<.001), and mental health functioning (p<.001). Among patients with presumptive diagnoses of major and minor depression, 84% and 79%, respectively, felt that it was at least somewhat important that they receive this help from their physician. Sixty-one percent of all primary care patients surveyed and 89% of depressed patients desired counseling; 23% of all patients and 33% of depressed patients wanted a medication; and 11% of all patients and 5% of depressed patients desired a referral to a mental health specialist. Conclusions  A majority of these primary care patients and almost all of the depressed patients felt that it was at least somewhat important to receive help from their physician for emotional distress. The desire for this help seems to be related to the severity of the mental health problem. Most of the patients wanted counseling, but relatively few desired a referral to a mental health specialist. Funded by grant R01 MH51067 from the National Institute of Mental Health.