Electromyographic and magnetic resonance imaging evaluations of individuals with patellofemoral pain syndrome

OBJETIVOS: Analisar a atividade elétrica (EMG) dos músculos vasto medial oblíquo (VMO), vasto lateral longo (VLL) e vasto lateral oblíquo (VLO) de indivíduos com síndrome da dor femoropatelar (SDFP) durante contração isométrica voluntária máxima (CIVM) de extensão da perna com o joelho a 30(0), a dor por meio da Escala Visual Analógica (EVA) e o posicionamento da patela por meio da ressonância magnética nuclear por imagem (RMNI). MÉTODOS: Avaliaram-se 12 mulheres com SDFP e 12 clinicamente normais, que realizaram cinco CIVM de extensão da perna no ângulo de 30(0) para análise da EMG. Avaliou-se o ângulo do sulco (AS), ângulo de congruência (AC), ângulo de inclinação patelar (AIP) e deslocamento patelar (DP) pela RMNI. Utilizaram-se testes estatísticos: ANOVA, análise de variância de medidas repetidas para EMG; o teste Mann-Whitney U para análise da RMNI; o teste de correlação de Pearson (r) entre EMG e RMNI e análise de variância one-way para avaliação da dor (p<0,05). RESULTADOS: Verificou-se maior atividade elétrica do músculo VLL em relação ao VMO no grupo com SDFP. Em ambos os grupos, os músculos VMO e VLL apresentaram maior atividade elétrica que o VLO. Para o grupo SDFP, a RMNI revelou maiores valores do AS e menores do AC, e verificou-se uma correlação negativa entre VMO e AIP. CONCLUSÃO: Os dados sugerem que maior atividade elétrica do VLL, juntamente com o aumento do AS e diminuição do AC, possam ser fatores favorecedores da instabilidade patelar nos indivíduos com SDFP.OBJECTIVES: To analyze the electrical activity of the vastus medialis obliquus (VMO), vastus lateralis longus (VLL) and vastus lateralis obliquus (VLO) muscles of individuals with patellofemoral pain syndrome (PFPS) during maximum voluntary isometric contraction (MVIC) of lower leg extension with the knee at 30°; to assess pain using a visual analogue scale (VAS); and to assess patellar positioning using magnetic resonance imaging (MRI). METHODS: Twelve women with PFPS and 12 clinically normal women were evaluated. They performed five MVICs of lower leg extension at 30° for electromyographic (EMG) analysis. Using MRI, the sulcus angle (SA), congruence angle (CA), patellar tilt angle (PTA) and patellar displacement (PD) were obtained. The following statistical tests were used: analysis of variance (ANOVA) for repeated measurements to assess EMGs; Mann-Whitney U test to analyze MRIs; Pearson's (r) correlation test between EMGs and MRIs; and one-way ANOVA to evaluate pain (p<0.05). RESULTS: In the PFPS group, there was greater electrical activity in the VLL than in the VMO. In both groups, there was greater electrical activity in the VMO and VLL than in the VLO. In the PFPS group, the MRI showed higher SA and lower CA values, and there was a negative correlation between the VMO and the PTA. CONCLUSION: The data suggest that, in individuals with PFPS, greater electrical activity in the VLL combined with an increased SA and a decreased CA may contribute to patellar instability.Conselho Nacional de Pesquisa (CNPq

A note on model uncertainty in linear regression

We consider model selection uncertainty in linear regression. We study theoretically and by simulation the approach of Buckland and co-workers, who proposed estimating a parameter common to all models under study by taking a weighted average over the models, using weights obtained from information criteria or the bootstrap. This approach is compared with the usual approach in which the 'best' model is used, and with Bayesian model averaging. The weighted predictor behaves similarly to model averaging, with generally more realistic mean-squared errors than the usual model-selection-based estimator

Effect of tibia rotation on the electromyographical activity of the vastus medialis oblique and vastus lateralis longus muscles during isometric leg press

Objectives: To evaluate the electrical activity of the vastus medialis obliquus (VMO) and vastus lateralis longus (VLL) with the tibia in neutral, medial and lateral rotation on the horizontal leg press. Design: Repeated measures analysis of the effects of tibia rotation on VMO and VLL activity. Setting: Evaluation and intervention in orthopaedics and traumatology laboratory. Participants: Fifteen healthy participants, no previous musculoskeletal damage of the lower limb. Main outcome measures: Electrical activity (Root Mean Square) of the VMO and VLL was measured during submaximal isometric contractions (SIC) with the knee at 90 degrees of flexion. The effect of tibia rotation in electrical activity of the VMO and VLL was measured. Results: VLL activity was significantly higher than VMO activity with the tibia in medial rotation (p = 0.03). Tibia rotation did not influence the activity of the VMO muscle (p = 0.26). VLL activity was significantly higher with medial than neutral tibia rotation (p = 0.005). Conclusions: The results suggest that tibia rotation does not strengthen selectively the VMO muscle during isometric leg press at 90 degrees knee flexion. (c) 2004 Elsevier Ltd. All rights reserved.61152

Analysis on the activation of the VMO and VLL muscles during semisquat exercises with and without hip adduction in individuals with patellofemoral pain syndrome

Objective: The purpose of this study was to investigate the effect of hip adduction on the activity of the Vastus Medialis Obliquus (VMO) and Vastus Lateralis Longus (VLL) muscles during semisquat exercises. Methods: Twenty female subjects, divided into two groups comprising healthy and patellofemoral pain syndrome (PFPS) subjects (ten volunteers for each group), performed three double-leg semisquat exercise trials with maximum hip adduction isometric contraction (DLSS-HA) and three double-leg semisquat exercise trials without hip adduction (DLSS). The normalized electromyographic muscle data were analysed using Repeated Measure ANOVA (P <= 0.05). Results: The electrical activity of both VMO and VLL muscles was significantly greater during DLSS-HA exercise than during DLSS (p = 0.0002) for both groups. Additionally, an independent Repeated Measure ANOVA revealed that the electric activity of the VLL muscle was significantly greater (p = 0.0149) than that of the VMO muscle during DLSS exercises only for the PFPS group. However, no differences were found during DLSS-HA exercises. Conclusions: Although there was no preferential VMO muscle activation, the association of hip adduction with squat exercise promoted a greater balance between the medial and lateral portions of the quadriceps femoris muscle and could be indicated for the conservatory treatment of PFPS patients. The association of isometric hip adduction with isometric semisquat exercises produced a more overall quadriceps activity and could be indicated for clinical rehabilitation or muscle strengthening programs. (c) 2005 Elsevier Ltd. All rights reserved.15659660

The practical utility of incorporating model selection uncertainty into prognostic models for survival data

Predictions of disease outcome in prognostic factor models are usually based on one selected model. However, often several models fit the data equally well, but these models might differ substantially in terms of included explanatory variables and might lead to different predictions for individual patients. For survival data, we discuss two approaches to account for model selection uncertainty in two data examples, with the main emphasis on variable selection in a proportional hazard Cox model. The main aim of our investigation is to establish the ways in which either of the two approaches is useful in such prognostic models. The first approach is Bayesian model averaging (BMA) adapted for the proportional hazard model, termed ‘approx. BMA’ here. As a new approach, we propose a method which averages over a set of possible models using weights estimated from bootstrap resampling as proposed by Buckland et al., but in addition, we perform an initial screening of variables based on the inclusion frequency of each variable to reduce the set of variables and corresponding models. For some necessary parameters of the procedure, investigations concerning sensible choices are still required. The main objective of prognostic models is prediction, but the interpretation of single effects is also important and models should be general enough to ensure transportability to other clinical centres. In the data examples, we compare predictions of our new approach with approx. BMA, with ‘conventional’ predictions from one selected model and with predictions from the full model. Confidence intervals are compared in one example. Comparisons are based on the partial predictive score and the Brier score. We conclude that the two model averaging methods yield similar results and are especially useful when there is a high number of potential prognostic factors, most likely some of them without influence in a multivariable context. Although the method based on bootstrap resampling lacks formal justification and requires some ad hoc decisions, it has the additional positive effect of achieving model parsimony by reducing the number of explanatory variables and dealing with correlated variables in an automatic fashion

The H63D genetic variant of the HFE gene is independently associated with the virological response to interferon and ribavirin therapy in chronic hepatitis C

Background Conflicting results have been reported in studies evaluating the relationship between serum markers of iron overload, liver iron deposits, and HFE mutations (C282Y and H63D) in chronic hepatitis C patients, and also their impact on the response to therapy in these patients. Aim To evaluate the role of HFE mutations in the severity of liver disease and in the response to therapy in chronic hepatitis C. Methods Two hundred and sixty-four hepatitis C patients treated with standard interferon and ribavirin were divided into two groups according to type of antiviral response: sustained virological response (SVR) and nonresponse or relapse. We evaluated the relationship between HFE mutation and the type of antiviral response, clinical data, biochemical tests, liver histopathology, virological data, and HFE mutations. Results Of the 264 patients, 88 (32.1%) had SVR whereas 67.9% had nonresponse or relapse. Liver iron deposits were observed in 49.2% of the patients. The factors associated with SVR were hepatitis C virus genotype 2 or 3, transferrin saturation value of 45% or less, and detection of the H63D mutation. HFE mutation was more frequent in patients with iron deposits, but without association with serum iron biochemistry or severity of liver disease. Steatosis was more frequent in patients with liver iron deposits. Conclusion The H63D mutation was an independent factor associated with SVR in chronic hepatitis C patients, as also were hepatitis C virus genotype 2 or 3 and transferrin saturation value of 45% or less. Moreover, the H63D mutation was associated with liver iron deposits. Eur J Gastroenterol Hepatol 22: 1204-1210 (C) 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins