Design of Dexterous Mechanical Systems for Intuitive Telemanipulation in Minimally Invasive Surgery

Major progress in abdominal surgery has occurred over the last decades with the introduction of laparoscopic and minimally invasive techniques in the operating room. These innovative procedures attracted much attention due to several advantages: the need for smaller abdominal incisions resulting in faster recovery of the patient, improved cosmetics, shorter hospitalization and a significant reduction of costs. However, surgical instrumentation for this type of intervention still remains non-intuitive and much more difficult to use than tools for open surgical procedures. As a consequence, these minimally invasive techniques are limited to fairly simple procedures. Due to the landscape of medical reimbursement, there is a substantial push by insurance companies, health care organizations and hospitals to extend minimally invasive techniques to a wider range of surgical procedures in order to reduce hospital stays and therefore costs. In order to respond to these demands, a strong research effort has been made over the past years on the development of enabling minimally invasive technologies, mainly through the introduction and development of robotic systems. Surgical robots significantly contribute to the improvement of the surgical performance by increasing the dexterity and user-friendliness of surgical procedures through the use of robotic telemanipulation. However, despite years of research, the field of surgical robotics is still only at the beginning of a very promising large scale development. Although a large number of systems have been developed, several issues are not yet addressed, limiting the adoption of surgical robots by a broader range of hospitals. A major limitation is related to the lack of internal dexterity, caused by the mobility constraints imposed by the small entry port. On one hand, it is important to increase the dexterity of the end-effectors inside the body, overcoming the issues of limited manoeuvrability in the abdominal cavity. On the other hand, the system must be introduced through conventional trocars, which are small in diameter. The management of this trade-off is extremely challenging, making the development of dexterous micro-manipulators one of the most important issues in the field of robotic systems for surgery. Another limitation is that the current surgical robots are voluminous, competing for precious space within the operating room and significantly increasing the complexity of operating room logistics. Access to the patient is thus impaired, which raises safety concerns. Furthermore, due to the physical separation from the operating area and lack of force-feedback on the existing surgical systems, surgeons cannot feel the contact forces between instruments and tissue. This limitation may cause long operating times and unintentional damage of tissue and suturing material. Although bringing several technical advantages for surgeons, current robotic systems are extremely expensive in acquisition, maintenance, disposable tools and training, representing much higher direct costs compared with open surgery and laparoscopic instrumentation. For this reason, access to robotic surgery is limited to a minority of hospitals that can afford to purchase such systems and have enough patient volume to justify the acquisition. This tendency towards centralisation of complex minimally invasive surgeries draws patients from hospitals without surgical robots and places a significant burden on the healthcare system. This thesis investigates novel mechanical systems to be used in different surgical telemanipulators, solving the limitations of existing robotic and manual surgical equipment, in three main areas: patient safety, surgical dexterity and health care cost. This can be achieved by providing the surgeon with more compact systems comprising new multi-DOF micromanipulators, and new mechanical telemanipulators able to deliver dexterous manipulation through a more affordable technology. These objectives implied not only an investigation of technical aspects such as the performance requirements of surgical tools, but also the investigation of the different medical procedures and surgical tasks used by doctors during minimally invasive interventions. Although, the solutions studied in this thesis have been applied in the context of surgical systems for minimally invasive surgery, the outcome of this research can be extended to several other application fields. From a general perspective, the goal of this thesis is to propose a document which may be useful and inspiring for machine designers, developers, or scientists who wish to create efficient remotely controlled manipulators for several applications involving multi-DOF manipulation.