Robotic creation of operating space for minimally invasive hip joint surgery

Hip joint surgeries are commonplace in our aging society. Robotic hip joint surgery is performed to cut bone precisely and is expected to be performed as minimally invasive treatment. Minimally invasive hip joint surgery needs operating space between muscle tissues and the bone around hip joint. In this paper a prototype of an articulated muscle-retracting robot for minimally invasive RAO (Rotational Acetabular Osteotomy and one of the hip joint surgeries) is described. The muscle-retracting robot's role is to create an operating space between muscles and the surface of the bone for the other robot, whose role is to cut bone. The mechanical structure is very thin to follow a narrow path and tough enough to scrape and retract muscles around a hip joint. The prototype is designed based on the required specification from the previous experiments data. The prototype has 9 DOF, in which 3 DOF arms are capable of controlling the tip position and the force between muscle tissues and the surface of the bone. 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 and on the living tissues of 27 mm in the crest of the Mum by magnitude of maximum force of 25 N. The scraped living tissues were a narrow part around the hip joint. We shall continue to research it and establish a stable control method to scrape tissues.