To overcome the physical limitations of mechanical bone cutting in minimally invasive surgery, we are developing a miniature parallel robot that enables positioning of a pulsed laser with an accuracy below 0.25 mm and minimizes the required manipulation space above the target tissue. This paper presents the design, control, device characteristics, functional testing, and performance evaluation of the robot. The performance of the robot was evaluated within the scope of a path-following experiment. The required accuracy for continuous cuts was achieved and reached 0.176 mm on the test bench.

Objective: Developing robotic tools that introduce substantial changes in the surgical workflow is challenging because quantitative requirements are missing. Experiments on cadavers can provide valuable information to derive workspace requirements, tool size, and surgical workflow. This work aimed to quantify the volume inside the knee joint available for manipulation of minimally invasive robotic surgical tools. In particular, we aim to develop a novel procedure for minimally invasive unicompartmental knee arthroplasty (UKA) using a robotic laser-cutting tool. Methods: Contrast solution was injected into nine cadaveric knees and CT scans were performed to evaluate the tool manipulation volume inside the knee joints. The volume and distribution of the contrast solution inside the knee joints were analyzed with respect to the femur, tibia, and the anatomical locations that need to be reached by a laser-cutting tool to perform bone resection for a standard UKA implant. Results: Quantitative information was determined about the tool manipulation volume inside these nine knee joints and its distribution around the cutting lines required for a standard implant. Conclusion: Based on the volume distribution, we could suggest a possible workflow for minimally invasive UKA, which provides a large manipulation volume, and deducted that for the proposed workflow, an instrument with a thickness of 5-8 mm should be feasible. Significance: We present quantitative information on the three-dimensional distribution of the maximally available volume inside the knee joint. Such quantitative information lays the basis for developing surgical tools that introduce substantial changes in the surgical workflow.

We are developing a robotic system for future application in minimally invasive laser osteotomy. This paper presents the mechanical system concept as a macro-milli-micro system and focuses on designing and evaluating the milli-system. The milli-system consists of an articulated tendon-driven robotic endoscope with seven rigid links with an outer diameter of 8mm connected by six discrete rotational joints (±30°). These joints can be controlled individually, however, controlling one joint’s motion influences all joints located more distally, making joint control an interesting challenge. Controlling each joint as desired will allow positioning the micro-system mounted at the endoscope’s tip. The micro-system is itself a robot that will accurately position the laser. The robotic endoscope incorporates a hollow core with a diameter of 4.8mm that holds a supply channel for the micro-system with the necessary means for actuation and surgical intervention. We demonstrated the functionality of the robotic endoscope in tracking experiments. Despite the joints’ mutual influence, the articulated robotic endoscope could be handled successfully and achieved an angular settling error of less than 1° in the individual joints. The overall robotic system’s functionality was successfully demonstrated with a time-synchronized joint movement of the macro-system (serial manipulator) and the robotic endoscope.

Within my thesis, I worked on the challenges of robotics in developing a system that enables minimally invasive bone-cutting with a laser. Knee replacement surgery was the first target application. One of the main challenges was achieving high positioning accuracy of the laser while maintaining a form factor that allows minimally invasive insertion of the robotic device and minimally invasive device manipulation during large-area surface treatments.

Advancements in personalized medicine, threedimensional (3D) printing, miniaturization, and robot-assisted surgery are driving innovation in tissue engineering. A novel approach, known as in situ printing, focuses on the direct deposition of materials at the surgical site. Using the in situ printing approach, bone and/or cartilage defects can be addressed with high precision. Furthermore, highly customized 3D printed tissue constructs or implants can be deposited directly inside the body. Currently, most applications of in situ printing are limited to areas near the skin or open surgeries. Even though a minimally invasive approach would bring clinical benefits, only a few research groups have focused on this field. In this scoping review, we provide an overview of the current state of in situ minimally invasive 3D printing technology for bone and cartilage regeneration and discuss its advantages and current challenges.