The effect of immobilization on ligamentous healing and strength of the medial collateral ligament of the rat knee

The purpose of this study was to determine the effects of varying periods of immobilization on ligamentous healing and strength in a rat experimental model. Sixty-one mature male Wistar rats were used. The left knee medial collateral ligament was surgically exposed, divided, and repaired. The rats were randomly placed into one of four groups: Group A, no immobilization, Group B, 2 weeks' immobilization, Group C, 6 weeks' immobilization, and Group D, 10 weeks' immobilization of the operated limb. The right knee served as a control. The ligaments were studied histologically and biomechanically at 2 weeks, 6 weeks, 10 weeks and 20 weeks post-operatively. Histologic samples were objectively evaluated with the light microscope using a Maturity Index Score and Scale that were devised based on the numbers and orientation of the fibroblasts and the amount and orientation of the collagen fibres. Ligament-bone preparations were studied using an Instron material testing machine to determine the biomechanical properties of the ligament until failure. Utilizing the Maturity Index Score and Scale, it was shown that Group A, with no immobilization, matured more rapidly than the other groups, and achieved full maturity at 20 weeks post-operatively. The other groups all showed a retarded rate of healing while immobilized. The electron microscopic study supported this data by demonstrating the level of metabolic activity of the fibroblasts which decreased with increasing maturity and by demonstrating that the size, amount and orientation of the collagen fibers increased with mobilization. The biomechanical testing showed that at 2 weeks post-operative, Group A had achieved a strength which was 46% of controls while Group B was only 29% of controls (p = 0.055). At 6 weeks Group A was 65% of controls, Group B was 56% of controls and Group C was 39% of controls (p = 0.0004). At 20 weeks Group A was 83% of controls, Group B was 71% of controls, Group C was 66% of controls and Group D was 48% of controls (p = 0.0005). Group A was 71% stronger than Group D at this time, indicating that the healing medial collateral ligament attained a greater strength and histologically matured more rapidly if mobilization is begun immediately.Science, Faculty ofBotany, Department ofZoology, Department ofGraduat

Adverse fibrosis remodeling and aortopulmonary collateral flow are associated with poor Fontan outcomes

Abstract Background The extent and significance in of cardiac remodeling in Fontan patients are unclear and were the subject of this study. Methods This retrospective cohort study compared cardiovascular magnetic resonance (CMR) imaging markers of cardiac function, myocardial fibrosis, and hemodynamics in young Fontan patients to controls. Results Fifty-five Fontan patients and 44 healthy controls were included (median age 14 years (range 7–17 years) vs 13 years (range 4–14 years), p = 0.057). Fontan patients had a higher indexed end-diastolic ventricular volume (EDVI 129 ml/m2 vs 93 ml/m2, p < 0.001), and lower ejection fraction (EF 45% vs 58%, p < 0.001), circumferential (CS − 23.5% vs − 30.8%, p < 0.001), radial (6.4% vs 8.2%, p < 0.001), and longitudinal strain (− 13.3% vs − 24.8%, p < 0.001). Compared to healthy controls, Fontan patients had higher extracellular volume fraction (ECV) (26.3% vs 20.6%, p < 0.001) and native T1 (1041 ms vs 986 ms, p < 0.001). Patients with a dominant right ventricle demonstrated larger ventricles (EDVI 146 ml/m2 vs 120 ml/m2, p = 0.03), lower EF (41% vs 47%, p = 0.008), worse CS (− 20.1% vs − 25.6%, p = 0.003), and a trend towards higher ECV (28.3% versus 24.1%, p = 0.09). Worse EF and CS correlated with longer cumulative bypass (R = − 0.36, p = 0.003 and R = 0.46, p < 0.001), cross-clamp (R = − 0.41, p = 0.001 and R = 0.40, p = 0.003) and circulatory arrest times (R = − 0.42, p < 0.001 and R = 0.27, p = 0.03). T1 correlated with aortopulmonary collateral (APC) flow (R = 0.36, p = 0.009) which, in the linear regression model, was independent of ventricular morphology (p = 0.9) and EDVI (p = 0.2). The composite outcome (cardiac readmission, cardiac reintervention, Fontan failure or any clinically significant arrhythmia) was associated with increased native T1 (1063 ms vs 1026 ms, p = 0.029) and EDVI (146 ml/m2 vs 118 ml/m2, p = 0.013), as well as decreased EF (42% vs 46%, p = 0.045) and worse CS (− 22% vs − 25%, p = 0.029). APC flow (HR 5.5 CI 1.9–16.2, p = 0.002) was independently associated with the composite outcome, independent of ventricular morphology (HR 0.71 CI 0.30–1.69 p = 0.44) and T1 (HR1.006 CI 1.0–1.13, p = 0.07). Conclusions Pediatric Fontan patients have ventricular dysfunction, altered myocardial mechanics and increased fibrotic remodeling. Cumulative exposure to cardiopulmonary bypass and increased aortopulmonary collateral flow are associated with myocardial dysfunction and fibrosis. Cardiac dysfunction, fibrosis, and collateral flow are associated with adverse outcomes

Incidence of Hospitalization for Respiratory Syncytial Virus Infection amongst Children in Ontario, Canada: A Population-Based Study Using Validated Health Administrative Data.

RSV is a common illness among young children that causes significant morbidity and health care costs.Routinely collected health administrative data can be used to track disease incidence, explore risk factors and conduct health services research. Due to potential for misclassification bias, the accuracy of data-elements should be validated prior to use. The objectives of this study were to validate an algorithm to accurately identify pediatric cases of hospitalized respiratory syncytial virus (RSV) from within Ontario's health administrative data, estimate annual incidence of hospitalization due to RSV and report the prevalence of major risk factors within hospitalized patients.A retrospective chart review was performed to establish a reference-standard cohort of children from the Ottawa region admitted to the Children's Hospital of Eastern Ontario (CHEO) for RSV-related disease in 2010 and 2011. Chart review data was linked to Ontario's administrative data and used to evaluate the diagnostic accuracy of algorithms of RSV-related ICD-10 codes within provincial hospitalization and emergency department databases. Age- and sex-standardized incidence was calculated over time, with trends in incidence assessed using Poisson regression.From a total of 1411 admissions, chart review identified 327 children hospitalized for laboratory confirmed RSV-related disease. Following linkage to administrative data and restriction to first admissions, there were 289 RSV patients in the reference-standard cohort. The best algorithm, based on hospitalization data, resulted in sensitivity 97.9% (95%CI: 95.5-99.2%), specificity 99.6% (95%CI: 98.2-99.8%), PPV 96.9% (95%CI: 94.2-98.6%), NPV 99.4% (95%CI: 99.4-99.9%). Incidence of hospitalized RSV in Ontario from 2005-2012 was 10.2 per 1000 children under 1 year and 4.8 per 1000 children aged 1 to 3 years. During the surveillance period, there was no identifiable increasing or decreasing linear trend in the incidence of hospitalized RSV, hospital length of stay and PICU admission rates. Among the Ontario RSV cohort, 16.3% had one or more major risk factors, with a decreasing trend observed over time.Children hospitalized for RSV-related disease can be accurately identified within population-based health administrative data. RSV is a major public health concern and incidence has not changed over time, suggesting a lack of progress in prevention

Incidence of hospitalized RSV (per 1000 children) 2005–2013 with 95% confidence intervals.

<p>Legend: Incidence per 1000 person years is given for each fiscal year from 2005 to 2013. Error bars shown are the calculated 95% confidence intervals. Closed circles (•) represent the incidence in the full Ontario cohort of children under 3 years of age. Closed triangles (▾) represent the incidence for children under 1 year of age. Open circles (ο) represent the incidence for children between 1 and 3 years of age.</p

Prevalence of major RSV risk factors in Ontario children less than 3 years.

<p>Prevalence of major RSV risk factors in Ontario children less than 3 years.</p