Feasibility study of a mini, bone-attached, robotic system for spinal operations: analysis and experiments

Abstract

Study design: In this investigation, a new concept of a miniature, bone-attached, medical robotic system for spinal operations is presented. As part of the design parameters of the robot, the forces and moments applied by the physician during insertion of Kirschner wires to soft tissues and drilling in hard tissues were examined. A theoretical model for the expected error of the robotic system due to the applied force has been derived and verified experimentally. The results of a clinical experiment that was carried out on a cadaver support the theoretical model derived and the miniature, bone-attached, robotic concept.

Objectives: 1) Examining the concept of attaching a miniature robotic system to the spinous process of the operated vertebra. 2) Measuring the forces applied by the physician during insertion of Kirschner wires to soft tissues and drilling in hard tissues. 3) Evaluating the expected error of the robot due to mechanical and anatomic deflection caused by the forces applied by the physician during operation. 4) Testing and verifying the theoretical background by a clinical experiment.

Summary of background data: Spinal operations are reported in the literature to have a relatively low success rate (70%-90%). This low success rate is affected by misunderstanding of the disease and its indications, resulting in bad selection of patients. From the technical point of view, the low success rate is greatly affected by the physician's lack of experience and the complexity of the spinal anatomy. The development of a miniature bone-attached robotic system for spinal operations could improve the success rate of spinal operations, introduce new percutaneous procedures, and shorten recovery and hospitalization time. Moreover, it will reduce the use of fluoroscopic exposure during operation; consequently, it will decrease considerably exposure to radiation during spinal operations.

Methods: Forces and moments applied by the physician during operation were measured by a 6-DOF miniature sensor. The measurements were taken during K-wire insertion both to soft and to hard tissues of a sheep and a human cadaver. A theoretical model of the expected location error of a K-wire, inserted to selected vertebralanatomies by the robotic system, was derived and verified experimentally.

Results: The theoretical model agreed with the experimental results, meaning that the combination of the spinous process and the robotic structure is rigid enough to guide a K-wire accurately. The forces and moments were measured and analyzed, and the total expected error due to the forces and moments was calculated. The clinical experiments supported the theoretical model and proved the system's feasibility.

Conclusions: The given results support the theoretical model developed. Moreover, a miniature robotic guiding system can be attached to the spinous process of a given vertebra. The deflection and system error resulting from the forces and moments acting during operation are within the allowable errors.