Partial fasciotomy has major effects on muscular mechanics due to altered epimuscular myofascial force transmission

Abstract

In remedial orthopedic surgery (e.g., aponeurotomy), partial fasciotomy is widely applied; however, is seen as a preliminary step to the main operation only. It is aimed at studying the effects of partial fasciotomy on muscular mechanics on the basis of epimuscular myofascial force transmission. Before (intact condition) and after proximal partial fasciotomy, isometric muscle forces of the rat were measured at proximal and distal tendons of extensor digitorum longus (EDL) muscle as well as at the tied distal tendons of tibialis anterior (TA) and extensor hallucis longus (EHL) muscles in two different conditions: after distal lengthening of (1) EDL exclusively and (2) EDL and TA+EHL muscles simultaneously. Secondary goal was to test the role of increased recovery time on history effects. For EDL lengthening exclusively (1) at lower muscle lengths, partial fasciotomy removed distally directed net epimuscular loads acting on EDL (2) at intermediate and higher lengths, proximally directed epimuscular loads measured in intact condition decreased; however, remained after partial fasciotomy. Moreover, partial fasciotomy caused major changes in EDL length-force characteristics: EDL active forces decreased substantially and muscle optimum length shifted to a higher muscle length distally. Simultaneous muscle lengthening changed intact EDL forces substantially: net epimuscular loads as well as most active and passive forces decreased, optimum length shifted to a lower length and optimal force changed Added partial fasciotomy caused further force decreases and additional shift of optimum force to a lower length. Increase in recovery time increased the differences between control and actual forces i.e., history effects. Yet, history effects themselves were affected by epimuscular myofascial force transmission: partial fasciotomy reduced the force difference between control and actual forces. We conclude that partial fasciotomy alone has major effects on muscular mechanics which may be highly important for a full control over the outcome of the actual operation.