TEMPORAL VARIATION OF APPLIED INTER FRAGMENTARY DISPLACEMENT AT A BONE-FRACTURE IN HARMONY WITH MATURATION OF THE FRACTURE CALLUS

The amplitude of inter fragmentary displacement in long bone fractures greatly influences the pattern and speed of healing. Unfortunately, t he amplitude of natural cyclical displacement arising from patient act ivity is random because of the inherent flexibility of fixation device s under natural loading. Although fixators may be designed to control the amplitude of this displacement, the amplitudes most beneficial to healing have not been determined. Furthermore, the appropriate amplitu de must vary during healing as the reparative tissue (callus) progress es histologically and stiffens during maturation. In this study on an experimental fracture, the amplitude of applied cyclical displacement is varied during healing to correspond with the inverse of the callus stiffness versus time curve. In vivo mechanical stiffness tests on the callus indicate that the end point of the fixation period is achieved more rapidly than with a constant level of applied displacement. (C) 1998 IPEM. Published by Elsevier Science Ltd. All rights reserved.