Assessment of participation biases for a confidential non-anonymous adolescent study: A based population study.

A prospective study often receives a low participation rate that may alter the results quality. This study assessed the participation bias for a confidential non-anonymous adolescent survey among 1559 middle-school adolescents from north-eastern France (mean age 13.5 ±â€¯1.3). They completed an anonymous questionnaire gathering demographic/socioeconomic features as well as school, behavior and health-related difficulties, and adolescent's assent to participate with perceived parents' consent (APC) if they were contacted for a confidential non-anonymous survey at home. Such a survey received an APC of 60%. The logistic model including all socioeconomic factors and school, behavior and health-related difficulties showed that the adolescents with APC were less often male (adjusted odds ratio = 0.77, p = 0.014), non-European immigrant (0.48, p = 0.016), living with a single parent (0.72, p = 0.046), in manual-worker families (0.69, p = 0.007), had less often low parents' education (0.70, p = 0.002), body-mass-index measurement refusal (0.60, p = 0.010), no regular physical/sports activity (0.70, p = 0.035), poor social relationships (0.73, p = 0.046) and poor living environment (0.63, p = 0.007). The percentage of subjects with APC steadily decreased with the number of these criteria: from 74% for 0 criterion to 19% for 6-8 criteria. Because of these possible strong participation biases the construction of adolescent cohorts and the results interpretation should be made with prudence.

The normal radiological anteroposterior alignment of the lower limb in children.

INTRODUCTION: The development of reconstructive surgery of the lower limbs aimed at multilevel correction demands a precise knowledge of the physiological variations in general radiological parameters of the lower limbs in children of various age groups. It is crucial in systemic skeletal diseases, when deformities affect limbs and the surgeon does not have an intact limb as a reference. The aim of this retrospective study was to establish the normal radiological values of lower limb parameters used in the surgical correction of deformities in children of various age groups. MATERIAL AND METHODS: Teleradiographs of the lower limbs taken in children with unilateral congenital or posttraumatic deformity were retrospectively reviewed. Weight-bearing full-length anteroposterior radiographs of the entire lower extremities were taken in a standing position. The study involved 215 extremities of 208 children (93 girls and 115 boys); the ages ranged from 2 years 1 month to 15 years 11 months old. Key variables included the anatomic medial proximal femoral angle (aMPFA), anatomic lateral distal femoral angle (aLDFA), anatomic medial proximal tibial angle (aMPTA), anatomic lateral distal tibial angle (aLDTA), mechanical axis deviation (MAD), the angle formed by the femoral anatomical axis and the mechanical axis of the lower limb. RESULTS: The means and dynamics of variations, standard deviations (SD) and 95% confidence intervals of each parameter were calculated for each age and gender group. Simple regression analysis was performed to determine the relationship between the patient's age and the magnitude of aMPFA, aLDFA, aMPTA and aLDTA. Simple regression analysis showed a significant inverse correlation between patient age and the magnitude of aMPFA: the correlation coefficient was -0.77. A statistically significant inverse correlation between the MAD and the angle between the anatomic femoral axis and mechanical limb axis was found: the correlation coefficient was -0.53. CONCLUSION: In general, the received values were concordant to results of other studies. It concerned the MAD, aLDFA, aMPTA and angle between the mechanical limb axis and anatomic femoral axis. This is the first chronological evaluation of aMPFA and aLDTA from a relavively large series of patients. These normative data should be taken into consideration when evaluating lower limb alignment in children or applied in practice for planning and evaluation of the quality of surgical correction of complex deformities.