Micromotion and Migration of Cementless Tibial Trays Under Functional Loading Conditions

BackgroundThe outcome of cementless total knee arthroplasty (TKA) relies on successful bony ingrowth into the implant surfaces. Failures due to aseptic loosening are still reported, especially in younger and more active patients. The objective of this study is to quantify the micromotion of a commercially available design of cementless tibial tray under loading conditions simulating walking and stair descent.MethodA commercially available design of cementless total knee arthroplasty was implanted in 7 cadaveric knees which were preconditioned with 500 cycles of 0°-100° flexion under a vertical load of 1050 N in a custom-built, multiaxial functional activity simulator. This was followed by application of the peak forces and moments occurring during walking and stair descent. During each loading procedure, 3-dimensional motion at the bone-prosthesis interface was measured using digital image correlation.ResultsThe tray migrated 101 ± 25 μm on average during preconditioning, which was dominated by rotation in the sagittal plane (92% of total migration), combined with posterior translation (28%) and minimal rotation in the transverse plane (14%). The migration varied 2.7-fold (61-167 μm) between the 6 measurement zones. Stair descent produced significantly higher total micromotion than walking in zone #5 (62 ± 9 vs 51 ± 10 μm, P < .05) and zone #6 (68 ± 17 vs 37 ± 10 μm, P < .05). In addition, during stair descent, the tray exhibited significantly more tilting (anterior zones: 31 ± 17 vs ?16 ± 20 μm, P < .05; posterior zones: ?60 ± 8 vs ?40 ± 7 μm, P < .05) and more anteroposterior displacement in the anterior zones (?25 ± 3 vs ?13 ± 2 μm, P < .05) when compared to walking.ConclusionThe relative motion at the bone-prosthesis interface varied substantially around the periphery of the cementless tray. Under the loading conditions evaluated, the tray primarily underwent a rocking motion in the sagittal plane. Compared with walking, stair descent produced significantly more micromotion, especially in the posterior zones.     

Building related illnesses and indoor air pollution

Building related illnesses are a common problem in developed countries and are expected to increase rapidly in urban India. Although objective physical abnormalities are not generally found except in a few specific diseases like Legionnaires' disease, the symptoms can be uncomfortable and even disabling. In this review we initially introduce the concept of indoor air pollution and building related illnesses. Subsequently we review the sources of and exposure to the pollutants along with their health effects and the approach to a patient of suspected building related illness. We conclude by discussing the measures for the control of indoor air pollution.     

Rapid glucose-dependent increases in phosphatidic acid and phosphoinositides in rat pancreatic islets

Glucose effects on islet phospholipids were examined during direct incubation or after 3 days of 32P prelabeling in primary culture. In both cases, glucose increased the 32P content of phosphatidic acid (PA), phosphatidylinositol (PI), and polyphosphoinositides (PPI). Glucose-induced increases in PA, PI, and PPI in the culture-prelabeling experiments were evident within 1 min, dose related, and reflective of increases in phospholipid mass, which was confirmed in direct incubations by measurement of PI phosphorus. Thus, in addition to increasing PI-PPI hydrolysis, glucose increases de novo phospholipid synthesis in pancreatic islets. The latter may result from enhanced glycolysis and substrate availability for PA-PI-PPI synthesis, since glyceraldehyde and pyruvic acid also increased PI levels. Our findings raise the possibility that increases in PA, PI, and PPI synthesis could serve as a mechanism to enhance the generation of intracellular mediators, which are purported to regulate insulin secretion.     

Irritant and cytotoxic coumarins from Angelica glauca Edgew roots

Irritant and cytotoxic potentiality of six coumarins, isolated for the first time from the roots of Angelica glauca identified as 5,6,7-trimethoxycoumarin, 6-methoxy-7,8-methylenedioxycoumarin, bergapten, decursinol angelate, decursin, and nodakenetin, were investigated. The irritant potential was explored by open mouse ear assay, evaluating their ID(50) after acute and by IU (Irritant units) after chronic effects, while the cytotoxic capability was explored by their LC(50), using brine shrimp (Artemia salina) larvae (nauplii). All the coumarins exhibited well-defined irritancy on mouse's ears, compared with the positive controlled euphorbium reaction and cytotoxic response against brine shrimp larvae, compared with the positive control colchicine. Decursinol angelate and decursin were the most potent and persistent irritant compounds with least ID(50), whose reactions lasted for 48 h. 6-Methoxy-7,8-methylenedioxycoumarin and bergaten revealed an intermediate irritant reactions, while 5,6,7-trimethoxycoumarin and nodakenetin displayed the least irritant and least persistent reactions on mouse ears. Both decursin and decursinol angelate also appeared to be the stronger cytotoxic agents than other coumarins. 5,6,7-trimethoxycoumarin displayed an intermediate cytotoxic behaviour, while other three coumarins, i.e., 6-methoxy-7,8-methylenedioxycoumarin, bergapten, and nodakenetin, exhibited the least cytotoxic capacity against brine shrimp larvae.     

Hypothermia is not neuroprotective after infection-sensitized neonatal hypoxic–ischemic brain injury

Background

Therapeutic hypothermia (HT) is the standard treatment after perinatal hypoxic–ischemic (HI) injury. Infection increases vulnerability to HI injury, but the effect of HT on lipopolysaccharide (LPS) sensitized HI brain injury is unknown.

Design/methods

P7 rat pups were injected either with vehicle or LPS, and after a 4 h delay they were exposed to left carotid ligation followed by global hypoxia inducing a unilateral stroke-like HI injury. Pups were randomized to the following treatments: (1) vehicle treated HI-pups receiving normothermia treatment (NT) (Veh-NT; n = 30); (2) LPS treated HI-pups receiving NT treatment (LPS-NT; n = 35); (3) vehicle treated HI-pups receiving HT treatment (Veh-HT; n = 29); or (4) LPS treated HI-pups receiving HT treatment (LPS-HT; n = 46). Relative area loss of the left/right hemisphere and the areas of hippocampi were measured at P14.

Results

Mean brain area loss in the Veh-NT group was 11.2 ± 14%. The brain area loss in LPS-NT pups was 29.8 ± 17%, which was significantly higher than in the Veh-NT group (p = 0.002). The Veh-HT group had a significantly smaller brain area loss (5.4 ± 6%), when compared to Veh-NT group (p = 0.043). The LPS-HT group showed a brain area loss of 32.5 ± 16%, which was significantly higher than in the Veh-HT group (p < 0.001). LPS-HT group also had significantly smaller size of the left hippocampus, which was not found in other groups. LPS-sensitization significantly decreased the sizes of the right, unligated-hemispheres, independent of post-HI treatment.

Conclusions

Therapeutic hypothermia is not neuroprotective in this LPS-sensitized unilateral stroke-like HI brain injury model in newborn rats. Lack of neuroprotection was particularly seen in the hippocampus. Pre-insult exposure to LPS also induced brain area loss in the unligated hemisphere, which is normally not affected in this model.     

Association of gut microbiome dysbiosis with the progression of atrial fibrillation: A systematic review

Objective

Many clinical and preclinical studies have implicated an association between atrial fibrillation (AF) and its progression to imbalances in the gut microbiome composition. The gut microbiome is a diverse and complex ecosystem containing billions of microorganisms that produce biologically active metabolites influencing the host disease development.

Methods

For this review, a literature search was conducted using digital databases to systematically identify the studies reporting the association of gut microbiota with AF progression.

Results

In a total of 14 studies, 2479 patients were recruited for the final analysis. More than half (n = 8) of the studies reported alterations in alpha diversity in atrial fibrillation. As for the beta diversity, 10 studies showed significant alterations. Almost all studies that assessed gut microbiota alterations reported major taxa associated with atrial fibrillation. Most studies focused on short-chain fatty acids (SCFAs), whereas three studies evaluated TMAO levels in the blood, which is the breakdown product of dietary l -carnitine, choline, and lecithin. Moreover, an independent cohort study assessed the relationship between phenylacetylglutamine (PAGIn) and AF.

Conclusion

Intestinal dysbiosis is a modifiable risk factor that might provide newer treatment strategies for AF prevention. Well-designed research and prospective randomized interventional studies are required to target the gut dysbiotic mechanisms and determine the gut dysbiotic-AF relationship.