New approach to evaluation of orthopaedic supports compression properties

This research was carried out to investigate behaviour of a knitted orthopaedic knee support in simulated real conditions as well as to propose a new approach to compression evaluation to preclude the possibility of any error in designing of new orthopaedic supports with exact compression level. Fully finished supports with all additional non-textile elements were analysed in this research. The support is defined as a corrective or orthopaedic item intended to grip or support any movable part of the body in the correct position and allows movement of that body part. The ways how textile material deforms under applied stresses as well as relaxation processes over the time play an important role in its processing and end use. A strong linear dependence between elongation of the support and compression generated by the support was found in this research. However, investigation on stress relaxation over the time showed that stress decrease over 36,000 s coincides with ranges of one full compression class, and the highest change (approx. 50%) in tensile force occurs during the first 100–200 s of relaxation. Such a change of compression has significant influence on the predictive pressure value generated by the compression garment and undermines its functionality. The obtained results indicate that a new approach to compression evaluation methodology must be adopted for theoretical compression value computation. Consequently, evaluation of the compression according to the tensile force must be performed not earlier than after at least 120 s relaxation.