Muscle scraping manipulator for minimally invasive hip joint surgery (system design and evaluation of the workspace)

Hip joint surgeries are commonplace in our aging society. In this paper a prototype of a muscle scraping manipulator for minimally invasive RAO (Rotational Acetabular Osteotomy and one of the hip joint surgeries) is described. The muscle scraping manipulator's role is to make a surgical space between muscles and the surface of bone around hip joint for the other manipulator whose role is to cut bone. The mechanical structure is very thin to follow narrow path and tough enough to scrape and retract muscles around hip joint. The prototype is designed based on the required specification from the experiment data. The prototype has 9 DOF, in which 3 DOF manipulator are capable of controlling the tip position and the force between muscle tissues and the surface of the bone. 6 DOF manipulator's role is to position the 3 DOF manipulator. Evaluation of the prototype was done by using a compliant control as scraping method of muscle tissues from surface of the bone. The capability is revealed as a scraping length on a phantom of 140 mm around human hip joint model. We shall continue to study a stable control method to scrape tissues.