SIMULATION OF DISTAL TENDON TRANSFER OF THE BICEPS BRACHII AND THE BRACHIALIS MUSCLES

Rupture of the distal tendons of the biceps brachii and the brachialis often consists of a clean avulsion of the end of the tendons from the ir tuberosities. In most of the reattachment procedures these tendons are reinserted to the same tuberosities. The purpose of this study was to examine the kinetic activity in the upper limb when the insertion locations of the two prime elbow flexors are altered. The right upper limb was modeled as a two-bar linkage moving in the vertical plane of the scapula. Our Hill-type musculo-tendon actuation system was modeled in terms of five muscles moving in three-dimensional space. The prime elbow flexors, i.e. the biceps brachii and the brachialis, were excit ed maximally, while the other muscles were left passive and were inclu ded as such in the analysis. The limb kinetics was studied in four dif ferent insertion locations of the biceps brachii and the brachialis. D ata on the elbow kinematics, the muscle tension histories, the muscle length-tension and velocity-tension relationships and the joint constr aint forces were produced. The results indicate that when the new inse rtions of the biceps brachii and the brachialis are located further aw ay from the elbow joint axis, the moments of these muscles about the j oint axis increase. However, the shortening velocities of these muscle s are increased as well, which results in a reduced tension. In additi on, the magnitudes of the compressive force, the tangential forces and the torsional and bending moments are reduced. These results suggest that, whenever surgically possible, reinsertion of ruptured distal ten dons of the biceps brachii and the brachialis more distally to the loc ation of their tuberosities should be beneficial.