Analysis of the asymmetrically loaded spine by means of a continuum beam model.

A continuum beam model of the human spine, proposed by Hjalmars (Proceedings of the Fourth International Conference on Continuum Models of Discrete Systems, 1981), and earlier used by the present author as a tool for the analysis of mild functional scoliosis, is here used for the study of a spine, asymmetrically loaded in the frontal plane. In order to validate the theoretical predictions of the model, preliminary experiments are carried out, which show that the model fairly well describes the lateral curvatures that occur when, for various loading conditions, the spine is adjusted into a muscle-relaxed state of equilibrium. Values of the flexural rigidity estimated from the experiments are found to be in reasonable agreement with values, estimated from earlier observations on dead material, reported in the literature. The experiments also indicate that the model may be developed to a tool for estimations of the effective flexural rigidity of the spine in vivo.