Figure 1.
Concept of incompatible surgery. Illustration of a tendon transfer surgery that makes a putative muscle synergy unable to generate any force. A, An idealized arm with two pairs of antagonist muscles at two joints (m1 to m4), each generating a force in a specific direction at the end point (f1 to f4), is controlled by a muscle synergy recruiting two muscles simultaneously (m1 and m2). The activation of the synergy generates a force that is the sum of the forces generated by each constituent muscle (fsyn = f1 + f2). B, A tendon transfer surgery affecting the force generated by two muscles. C, After the surgery, one of the muscles participating to the synergy (m1′) generates a force in a direction that cancels the force of the other synergistic muscle (m2). The synergy no longer generates any force (f′syn = f′1 + f′2 = 0).