M.Sc Thesis

M.Sc StudentGertler Ifat
SubjectA Parallel Manipulator with Haptic Surface Scanning
and Milling Device for Registration-Free
DepartmentDepartment of Mechanical Engineering
Supervisor PROF. Alon Wolf
Full Thesis textFull thesis text - English Version


As orthopaedic implants become more sophisticated and complex, shaping the bone surface to match the implant becomes increasingly important. Development in tissue engineering field may provide in the near future amorfic organic cartilage implants, requiring virtuosic skills of free-hand sculpturing. This requirement will make robotic assistance a necessity.

Accurate bone machining contributes to success of the implant and can potentially increase the implant’s endurance and lifetime. Bone-mounted robots can eliminate intra-operative tracking errors during bone machining. However, registration errors still exist when aligning the pre-operative plan with the patient’s anatomy because the plan is based on pre-operative images. Thus, a robotic system that is capable of executing both surface acquisition and bone machining in a single procedure and within the same coordinate system is preferable to the current state of the art.

In this research we suggested conceptual robotic system and method for registration-free arthroplasty, and examined their feasibility. For this purpose, we used a mini bone-attached robotic system (MBARS) with a haptic interface. We performed force-controlled surface acquisition of a femur model, and validated its accuracy. The average distance error between acquired points and the surface model was less than 1 mm, which was further reduced by 5% with a compensation method which included curvature estimation of the reconstructed surface. An initial evaluation of in-situ bone milling included force and torque recording in real-time during the process, using haptic machining tool. The results may constitute a baseline for new, improved mechanical design.