A compact hand-held continuum manipulator for minimally invasive neurosurgery

Minimally invasive neurosurgical procedures are widely popular for the excision of deep-seated brain tumours and skull-base lesions. However, the limited maneuverability of the instruments due to highly confined routes and spaces is a challenge for the neurosurgeons. Even robotic arm-based interventions are difficult to implement as these procedures typically require frequent tool changes. Therefore, a combination of human dexterity and robotic intervention can be a good alternative. Accordingly, we have developed a dedicated, robotically manipulated hand-held instrument prototype that could easily maneuver in confined surgical environments. The manipulator is a continuum-type robot developed by alternate stacking of stiff and flexible discs, actuated by tendon wires attached to a high torque reduction motor. The manipulator mechanics were simulated using Cosserat-rod theory and validated through finite element analysis, physical experiments with calibrated weights. The manipulator was then integrated with a hand-held operating unit and the functionality was tested in a neuro-endo-trainer, followed by functional validation on a human cadaver head. The simplistic design and compact actuation unit of the prototype exhibited ease of fabrication, enhanced maneuverability in confined spaces and a universal appeal to the surgeons. The prototype demonstrated a maximum tip angle of 42.2° under suspended weight of 2.943 N, and successfully supported payloads up to 50 g without structural damage. Functional trials in a neuro-endo-trainer and cadaver confirmed superior maneuverability and access compared to rigid instruments, enabling smooth approach to extended or off-axis skull base regions. As such, the presented manipulator meets key design criteria for a practical, hand-held tool in minimally invasive neurosurgery and serves as a platform for future clinical translation.