Syndemic and syndemogenesis of low back pain in Latin-American population: a network and cluster analysis.

Introduction: Although low back pain (LBP) is a high-impact health condition, its burden has not been examined from the syndemic perspective.

Objective: To compare and assess clinical, socioeconomic, and geographic factors associated with LBP prevalence in low-income and upper-middle-income countries using syndemic and syndemogenesis frameworks based on network and cluster analyses.

Methods: Analyses were performed by adopting network and cluster design, whereby interrelations among the individual and social variables and their combinations were established.

Normalization of load and clearance effects in ball-in-socket-like replacements.

A normalizing loading parameter useful in summarising the mechanical response of plane pin-in-plate-like contacts is extended to axisymmetric ball-in-socket-like contacts. An example addressing a compliant layered artificial hip joint is presented, and the usefulness of the normalizing loading parameter is evidenced.

Analytical modelling of the elastomeric layer in soft layer hip replacements.

A mechanical analysis is carried out for a flat deformable layer, firmly anchored to a rigid substrate, and frictionlessly compressed by a rigid spherical indenter, with reference to the design of hip replacements whose cup is covered by an elastomeric layer. An available perturbation solution of differential character, developed for a layer subject to plane strain conditions, indented by a cylinder approximated as parabolic in shape and valid for high contact widths, is here extended to the axisymmetric problem of a layer compressed by a paraboloidal indenter. In addition to the paraboloidal idealization, an accurate mathematical description of the indenter spherical profile is incorporated into the modelling of this contact problem.

An appraisal of the paper by O'Carrol et al. (1990).

The paper by O'Carrol et al. (1), which addresses the problem of an elastomeric disc indented by a spherical punch, has been evaluated. The sources of disagreement between linear elastic numerical predictions and experimental measurements noted in this paper have been critically examined in the light of finite element forecasts obtained with a package which incorporates finite elasticity effects and incompressibility.

Axisymmetric finite element analysis of hip replacements possessing an elastomeric layer: the effects of clearance and Poisson's ratio.

A finite element analysis has been performed for a hip replacement incorporating an elastomeric surface layer. The effects of assuming the elastomer as incompressible have been examined for imposed loads, by comparing the incompressible solution to that using accurately measured values for Poisson's ratio, and while deflections were found to be significantly different, the changes in maximum pressure in the contact, maximum shear stress, contact angle and angular position to maximum shear stress were all small (less than 10 per cent). Comparisons have also been made between the finite element results for ABAQUS and an asymptotic solution, and it was found to be important to use the numerical model particularly at small values of clearance.