<p> New Delhi, Sep 17 (PTI): In a first-of-its-kind procedure, doctors in Delhi have combined an active robotic surgical system with a non-metallic, ceramic knee implant, a development they said could mark a new direction in knee replacement surgery.</p><p> The procedure was performed using active robotic assistance and was described by the doctors as the world's first active robot-assisted surgery involving a non-metallic/ceramic knee replacement, according to a statement issued on Wednesday.</