Mechanical effects of Botulinum toxin treatment on isolated mucsle: assessment of theoretical paralyzation patterns via finite element modeling

Abstract

Thespecific goal of the present study was to take an initial step in explaining the effects of Botulinum toxin treatment used for muscle pathologies such as spasticity on muscle mechanics via myofascial force transmission, which we believe is a major determinant. For this purpose an isolated EDL muscle model generated using the finite element method was used. In order to determine the effects of paralyzation location three cases were studied: Proximal half passive, middle half passive and distal half passive. Strain and stress distributions and length-force relationships of these cases were compared. Length-force relationship showed about 50% foce drop at optimum length for all three cases whereas at low lengths, distal half paralyzed case showed up to 15% more force reduction than other two cases. This result may be significant for spastic muscles since they are reported to operate at low muscle lengths. Also range of active force exertion decreased up to 23%. A significant result obtained from strain distributions is that the mechanically operational parts, i. e. parts that are not affected by Botulinum toxin showed less shortening compared to their counterparts in the non-paralyzed muscle. It is evident that this effect arises from the interaction between mechanically operational and paralyzed muscle portions. Such effect is a clear indication of intramuscular myofascial force transmission pathways.|Keywords: Botulinum toxin, Myofascial force transmission, Isolated muscle, Finite element modeling, Sarcomere length distribution.