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This paper proposes a detection method to identify the drill bit position during assisted bone drilling. A platform has been developed to support the surgeon in the planning of the drilling path. Albeit constrained along a fixed trajectory, the advancement of the drilling tool is manual, in order to preserve the natural haptic perception of the surgeon, who remains in charge of modulating the drilling force and the feeding rate according to the position of the drill bit in the bone. This paper describes a custom drill, embedded with force and position sensors, which allows the evaluation of a new parameter, referred to as Average Impedance (AI), that is related to the mechanical properties of the tissues in contact with the drill bit. An algorithm for layer identification has been implemented based on the variability of the AI signal. In perspective, the AI can provide the surgeon with additional information about the position of the drill bit in the bone, in order to increase the safety level of the procedure. The algorithm has been tested ex-vivo on swine bones. The tests demonstrated a reliability better than 80% in the discrimination of bone tissues.

This paper proposes a novel control algorithm for torque-controlled exoskeletons assisting cyclic movements. The control strategy is based on the injection of energy parcels into the human-robot system with a timing that minimizes perturbations, i.e., when the angular momentum is maximum. Electromyographic activity of main flexor-extensor knee muscles showed that the proposed controller mostly favors extensor muscles during extension, with a statistically significant reduction in muscular activity in the range of 10–20% in 60 out of 72 trials (i.e., 83%), while no effect related to swinging speed was recorded (speed variation was lower than 10% in 92% of the trials). In the remaining cases muscular activity increment, when statistically significant, was less than 10%. These results showed that the proposed algorithm reduced muscular effort during the most energetically demanding part of the movement (the extension of the knee against gravity) without perturbing the spatio-temporal characteristics of the task and making it particularly suitable for application in exoskeleton-assisted cyclic motions. Published version

The electromagnetic stimulation of nervous tissue has represented an alternative to electrical stimulation since the 1980s. The growing number of potential applications has led to an increasing interest in the development of modeling tools that can help the design of novel electromagnetic stimulators. In this context, the aim of this paper is to provide a versatile calculation framework to investigate the properties of the electric field generated by a plurality of miniature coils, arranged in cuff configuration. Furthermore, the capability of the miniature coils to elicit a neuronal response in specific portions of the (peripheral) nerve will be investigated. Starting from Jefimenko's equations, a model was implemented in MATLAB. It calculates the electromagnetic field induced by coils, with arbitrary shape and spatial orientation, and the activating function around the coils through simple numerical integration. By studying the activating functions, it is possible to determine where the neurons can be excited. The model was validated by comparison with FEM simulations. A dimensional analysis was conducted to compare in terms of shape and depth of the stimulation volumes different coil geometries, regardless of design parameters such as current, number of turns and coil sizes.The dimensionless groups identified according to Buckingham's theorem provide a direct estimate of the stimulation depth reached within the nerve.The calculation tools developed in this paper can be used in the design of coils to quickly compare different geometries and spatial distribution of coils in order to identify the optimal configurations for the specific application addressed by the designer.

This paper presents the design of a surgical positioning system conceived to handle and orient a cannula for Minimally Invasive Spine Surgery (MISS) keeping fixed a remote center of rotation during the orientation procedure. Specifically, many MISS treatments require the use of a transpedicular cannula as a guiding tool for spine fixation or for delivering biomaterials to the vertebral body or to the disc space. We designed a cannula orientation mechanism able to percutaneously guide the insertion towards the intervertebral space based only on the acquisition of a few fluoroscopic images. The insertion orientation, and therefore the regulation of the system joints configuration, can be planned by a software based on two perpendicular C-arm fluoroscopic images and starting from the identification of the insertion point and of the insertion direction drawn on the images by the surgeon. We present the software for the orientation planning and a simple kinematic structure with remote center of motion that allows the positioning and orientation of the guiding cannula. The system was dimensioned so to be compatible with the size of C-arm workspace and to minimally interfere with the surgical procedure and with the work of the medical staff.

In this paper we present a model for calculating the electric field, and its spatial derivatives, produced by arbitrarily shaped, oriented and placed coils carrying time-varying currents. The model has been validated by comparing its results with those obtained using FEM simulations. The model provides a simple and fast computation framework to investigate the electromagnetic stimulation of neural tissues. Some example applications are also provided.