Gauging electrical properties of bone with a bioimpedance-sensing drill

Review of Enhanced Handheld Surgical Drills

The handheld drill has been used as a conventional surgical tool for centuries. Alongside the recent successes of surgical robots, the development of new and enhanced medical drills has improved surgeon ability without requiring the high cost and consuming setup times that plague medical robot systems. This work provides an overview of enhanced handheld surgical drill research focusing on systems that include some form of image guidance and do not require additional hardware that physically supports or guides drilling. Drilling is reviewed by main contribution divided into audio-, visual-, or hardware-enhanced drills. A vision for future work to enhance handheld drilling systems is also discussed.

Design of electrical impedance spectroscopy sensing surgical drill using computational modelling and experimental validation

Electrical Impedance Spectroscopy (EIS) sensing surgical instruments could provide valuable and real-time feedback to surgeons about hidden tissue boundaries, therefore reducing the risk of iatrogenic injuries. In this paper, we present an EIS sensing surgical drill as an example instrument and introduce a strategy to optimize the mono-polar electrode geometry using a finite element method (FEM)-based computational model and experimental validation. An empirical contact impedance model and an adaptive mesh refinement protocol were developed to accurately preserve the behaviour of sensing electrodes as they approach high impedance boundaries. Specifically, experiments with drill-bit, cylinder, and conical geometries suggested a 15%-35% increase in resistance as the sensing electrode approached a high impedance boundary. Simulations achieved a maximum mean experiment-to-simulation mismatch of +1.7% for the drill-bit and +/-11% range for other electrode geometries. The simulations preserved the increase in resistance behaviour near the high impedance boundary. This highly accurate simulation framework allows us a mechanism for optimizing sensor geometry without costly experimental evaluation.

Novel Pedicle Navigator Based on Micro Inertial Navigation System (MINS) and Bioelectric Impedance Analysis (BIA) to Facilitate Pedicle Screw Placement in Spine Surgery: Study in a Porcine Model

STUDY DESIGN

A porcine model.

OBJECTIVE

The study aims to design a novel pedicle navigator based on micro-inertial navigation system (MINS) and bioelectrical impedance analysis (BIA) to assist place pedicle screw placement and validate the utility of the system in enhancing pedicle screw placement.

SUMMARY OF BACKGROUND DATA

The incidence of pedicle screw malpositioning in complicated spinal surgery is still high.Procedures such as computed tomography image-guided navigation, and robot-assisted surgery have been used to improve the precision of pedicle screw placement, but it remains an unmet clinical need.

METHODS

The miniaturized integrated framework containing MINS was mounted inside the hollow handle of the pedicle finder. The inner core was complemented by a high-intensity electrode for measuring bioelectric impedance. Twelve healthy male Wuzhishan minipigs of similar age and weight were used in this experiment and randomized to the MINS-BIA or freehand (FH) group. Pedicle screw placement was determined according to the modified Gertzbein-Robbins grading system on computed tomography images. An impedance detected by probe equal to the baseline value for soft tissue was defined as cortical bone perforation.

RESULTS

A total of 216 screws were placed in 12 minipigs. There were 15 pedicle breaches in the navigator group and 31 in the FH group; the detection rates of these breaches were 14 of 15 (93.3%) and 25 of 31 (80.6%), respectively, with a statistically significant difference between groups. The mean offsets between the planned and postoperatively measured tilt angles of the screw trajectory were 4.5° ± 5.5° in the axial plane and 4.8° ± 3.3° in the sagittal plane with the navigator system and 7.0° ± 5.1° and 7.7° ± 4.7°, respectively, with the FH technique; the differences were statistically significant.

CONCLUSION

A novel and portable navigator based on MINS and BIA could be beneficial for improving or maintaining accuracy while reducing overall radiation exposure.

Bioimpedance Sensing Surgical Drill - In Vivo Porcine Model

Surgical drilling to place dental implants in the mandible and maxilla is associated high risk of iatrogenic injuries to inferior alveolar nerve and maxillary sinus. Real-time tissue margin sensing at the drill-tip using electrical impedance spectroscopy (EIS) could reduce this risk by providing feedback to surgeons. Studies with saline analogues, ex-vivo tissues, in-situ tissues and computer models have been previously conducted to evaluate these impedance sensors. Understanding in-vivo electrical properties of tissues in the mandible and maxilla is critical to further develop the sensor and tissue margin sensing algorithms. In this paper, we propose an in-vivo animal model using pigs and discuss methods to test the sensor. Intra-operative imaging and optical tracking systems to assist in surgical navigation are described. The process of registering imaging and tracking information to localize impedance measurement sites within the anatomy are detailed. Results from one in-vivo case of drilling through the mandible are presented and discussed. Clinical Relevance- This model is crucial for characterizing in-vivo electrical properties of mandibular and maxillary tissues encountered during dental implant surgical drilling and for translating bioimpedance sensing drill technology to clinical space.

Split electrodes for electrical-conductivity-based tissue discrimination

This work presents a method to minimize the inadvertent cutting of tissues in surgeries involving bone drilling. We present electrical impedance measurements as an assistive technology to image-guided surgery to achieve online guidance. Proposed concept is to identify and localize the landmarks via impedance measurements and then use this information to superimpose the estimated drilling trajectory on the offline maps obtained by pre-operative imaging. To this end., we propose an asymmetric electrode geometry., split electrodes., capable of distinguishing impedance variations as a function of rotation angle. The feasibility of the proposed approach is verified with numerical analysis. A probe with stainless steel electrodes has been fabricated and tested with a technical phantom. Although the results are impacted by a non-ideality in the phantom., we could show that the variation of impedance as a function of rotation angle can be used to localize the regions with different impedivities. Clinical Relevance- Presented approach may be used to minimize the inadvertent cutting of tissues in surgeries involving bone drilling.

Power-Tool Use in Orthopaedic Surgery: Iatrogenic Injury, Its Detection, and Technological Advances: A Systematic Review

Power tools are an integral part of orthopaedic surgery but have the capacity to cause iatrogenic injury. With this systematic review, we aimed to investigate the prevalence of iatrogenic injury due to the use of power tools in orthopaedic surgery and to discuss the current methods that can be used to reduce injury.

Bioimpedance Sensing Surgical Drill - Computational Modelling and Experimental Validation

Surgical drilling to fixate dental implants is associated with high risk of injury to the inferior alveolar nerve (IAN) and the maxillary sinus. Current common practice is to use pre-operative radiographs to plan and drill with no real-time feedback of drill tip position with respect to these critical structures. Real-time proximity sensing of the IAN and maxillary sinus by measuring the electrical impedance properties of tissues, directly from the drill tip, while drilling may reduce and eventually eliminate this risk. Sensing impedance to detect tissue boundaries needs sensor geometry optimization for maximum detection distance. We have created a finite element method (FEM) based simulation platform that yields accurately impedances for different conductivities, frequencies and sensor geometries.