Smart bone plates can monitor fracture healing

Electrical impedance detects early stages of bone healing: An in vivo explanatory study of tibial fractures in rabbits

Purpose

Healing after bone fracture is assessed by clinical examination and frequent radiographs, which expose patients to radiation and lack standardisation. This study aimed to explore electrical impedance patterns during bone healing using electrical impedance spectroscopy in 18 rabbits subjected to tibial fracture stabilised with an external fixator.

Methods

Impedance was measured daily across the fracture site at a frequency range of 5 Hz to 1 MHz. Biweekly radiographs were analysed using modified anterior-posterior (AP) radiographic union score of the tibia (RUST). The animals were divided into three groups with different follow-up times: 1, 3 and 6 weeks for micro-computer tomography and mechanical testing.

Results

A decreasing trend in impedance was observed over time for all rabbits at lower frequencies. Impedance closest to 5 Hz showed a statistically significant decrease over time, with greatest decrease occurring during the first 7 postoperative days. At 5 Hz, a statistically significant correlation was found between impedance and the modified AP RUST score and between impedance and bone volume fraction.

Conclusions

This study showed that the electrical impedance can be measured in vivo at a distance from the fracture site with a consistent change in impedance over time and revealed significant correlation between increasing radiographic union score and decreasing impedance.

Level of Evidence

Not applicable.

Ultrasensitive capacitive sensing system for smart medical devices with ability to monitor fracture healing stages

Bone fractures are a global public health problem. A sustained increase in the number of incident cases has been observed in the last few decades, as well as the number of prevalent cases and the number of years lived with disability. Current monitoring techniques are based on imaging techniques, which are highly subjective, radioactive, expensive and unable to provide daily monitoring of fracture healing stages. The development of reliable, non-invasive and non-subjective technologies is mandatory to minimize non-union risks. Delayed healing and non-union conditions require timely medical intervention, such that preventive procedures and shortened treatment periods can be carried out. This work proposes the development of an ultrasensitive capacitive sensing system for smart implantable fixation implants with ability to effectively monitor the evolution of bone fractures. Both in vitro experimental tests and numerical simulations highlight that networks of co-surface capacitive systems are able: (i) to detect four different bone healing phases, capacitance decrease patterns occurring as the healing process progresses and (ii) to monitor the callus evolution in multiple target regions. These are very promising results that highlight the potential of capacitive technologies to minimize the individual and social burdens related to fracture management, mainly when delayed healing or non-union conditions occur.

Characterization of collagen response to bone fracture healing using polarization-SHG

In this study, we extend on the three parameter analysis approach of utilizing a noninvasive dual-liquid-crystal-based polarization-resolved second harmonic generation (SHG) microscopy to facilitate the quantitative characterization of collagen types I and II in fracture healing tissues. The SHG images under various linear and circular polarization states are analyzed and quantified in terms of the peptide pitch angle (PA), SHG-circular dichroism (CD), and anisotropy parameter (AP). The results show that the collagen PA has a value of 49.26° after 2 weeks of fracture healing (collagen type II domination) and 49.05° after 4 weeks (collagen type I domination). Moreover, the SHG-CD and AP values of the different collagen types differ by 0.05. The change tendencies of the extracted PA, SHG-CD, and AP parameters over the healing time are consistent with the collagen properties of healthy nonfractured bone. Thus, the feasibility of the proposed dual-liquid-crystal-based polarization-SHG method for differentiating between collagen types I and II in bone fracture healing tissue is confirmed.

Innovations in orthopaedic trauma: Top advancements of the past two decades and predictions for the next two

The first Trauma and Orthopaedic unit dates back to 1780, originally dedicated to the treatment of children's deformities. The specialty has subsequently become multifaceted, with a plethora of subspecialty areas of which orthopaedic trauma is the most commonly practiced. Recently there has been a significant demand for an evidence base with more than 130,000 of the 162,000 publications in the last century occurring within the past 20 years. This narrative review will summarise some of the more landmark changes within orthopaedic trauma that have been made within the past 20 years, whilst also attempting to predict where the specialty will continue to develop as we move forward.

Design and Manufacturing of Equipment for Investigation of Low Frequency Bioimpedance

The purpose of this study was to highlight a method of making equipment for the investigation of low frequency bioimpedance. A constant current with an average value of I = 100 µA is injected into the human body via means of current injection electrodes, and the biological signal is taken from the electrodes of electric potential charged with the biopotentials generated by the human body. The resulting voltage, ΔU is processed by the electronic conditioning system. The mathematical model of the four-electrode system in contact with the skin, and considering a target organ, was simplified to a single equivalent impedance. The capacitive filter low passes down from the differential input of the first instrumentation amplifier together with the isolated capacitive barrier integrated in the precision isolated secondary amplifier and maintains the biological signal taken from the electrodes charged with the undistorted biopotentials generated by the human body. Mass loops are avoided, and any electric shocks or electrostatic discharges are prevented. In addition, for small amplitudes of the biological signal, electromagnetic interferences of below 100 Hz of the power supply network were eliminated by using an active fourth-order Bessel filtering module. The measurements performed for the low frequency of f = 100 Hz on the volunteers showed for the investigated organs that the bioelectrical resistivities vary from 90 Ωcm up to 450 Ωcm, and that these are in agreement with other published and disseminated results for each body zone.

Non-destructive characterization of bone mineral content by machine learning-assisted electrochemical impedance spectroscopy

Continuous quantitative monitoring of the change in mineral content during the bone healing process is crucial for efficient clinical treatment. Current radiography-based modalities, however, pose various technological, medical, and economical challenges such as low sensitivity, radiation exposure risk, and high cost/instrument accessibility. In this regard, an analytical approach utilizing electrochemical impedance spectroscopy (EIS) assisted by machine learning algorithms is developed to quantitatively characterize the physico-electrochemical properties of the bone, in response to the changes in the bone mineral contents. The system is designed and validated following the process of impedance data measurement, equivalent circuit model designing, machine learning algorithm optimization, and data training and testing. Overall, the systematic machine learning-based classification utilizing the combination of EIS measurements and electrical circuit modeling offers a means to accurately monitor the status of the bone healing process.

Wireless Measurements Using Electrical Impedance Spectroscopy to Monitor Fracture Healing

There is an unmet need for improved, clinically relevant methods to longitudinally quantify bone healing during fracture care. Here we develop a smart bone plate to wirelessly monitor healing utilizing electrical impedance spectroscopy (EIS) to provide real-time data on tissue composition within the fracture callus. To validate our technology, we created a 1-mm rabbit tibial defect and fixed the bone with a standard veterinary plate modified with a custom-designed housing that included two impedance sensors capable of wireless transmission. Impedance magnitude and phase measurements were transmitted every 48 h for up to 10 weeks. Bone healing was assessed by X-ray, µCT, and histology. Our results indicated the sensors successfully incorporated into the fracture callus and did not impede repair. Electrical impedance, resistance, and reactance increased steadily from weeks 3 to 7-corresponding to the transition from hematoma to cartilage to bone within the fracture gap-then plateaued as the bone began to consolidate. These three electrical readings significantly correlated with traditional measurements of bone healing and successfully distinguished between union and not-healed fractures, with the strongest relationship found with impedance magnitude. These results suggest that our EIS smart bone plate can provide continuous and highly sensitive quantitative tissue measurements throughout the course of fracture healing to better guide personalized clinical care.

Effect of melatonin on electrical impedance and biomarkers of damage in a gastric ischemia/reperfusion model

The damage to the gastrointestinal mucosa induced by ischemia/reperfusion (I/R) is closely related to high mortality in critically ill patients, which is attributable, in part, to the lack of an early method of diagnosis to show the degree of ischemia-induced injury in this type of patients. Electrical Impedance Spectroscopy (EIS) has been shown to be a tool to early diagnose gastric mucosal damage induced by ischemia. A therapeutic alternative to reduce this type of injury is melatonin (MT), which has gastroprotective effects in I/R models. In this work, the effect of treatment with MT on the electrical properties of gastric tissue, biomarkers of inflammatory (iNOS and COX-2), proliferation, and apoptotic process under I/R conditions in male Wistar rats was evaluated through EIS, histological and immunohistochemical analysis. Treatment with MT prevents gastric mucosa damage, causing a decrease in gastric impedance parameters related to the inflammatory process and cellular damage. This suggests that EIS could be used as a tool to diagnose and monitor the evolution of gastric mucosal injury, as well as in the recovery process in critically ill patients.

A coupled computational framework for bone fracture healing and long-term remodelling: Investigating the role of internal fixation on bone fractures

In this study, a coupled computational modelling framework for bone fracture repair is presented that enables predictions of both healing and remodelling phases of the fracture region and is used to investigate the role of an internal fixation plate on the long-term healing performance of a fracture tibia under a range of different conditions. It was found that introduction of a titanium plate allowed the tibia to undergo successful healing at higher loading conditions and fracture gaps, compared with the non-plated versions. While these plated cases showed faster rates of repair in the healing phase, their performance was substantially different once they entered the remodelling phase, with substantial regions of stress shielding predicted. This framework is one of the few implementations of both fracture healing and remodelling phases of bone repair and includes several innovative approaches to smoothing, time-averaging and time incrementation in its implementation, thereby avoiding any unwanted abrupt changes between tissue phenotypes. This provides a better representation of tissue development in the fracture site when compared with fracture healing models alone and provides a suitable platform to investigate the long-term performance of orthopaedic fixation devices. This would enable the more effective design of permanent fixation devices and optimisation of the spatial and temporal performance of bioabsorbable implants.

Continuous Implant Load Monitoring to Assess Bone Healing Status—Evidence from Animal Testing

Background and Objectives: Fracture healing is currently assessed through qualitative evaluation of radiographic images, which is highly subjective in nature. Radiographs can only provide snapshots in time, which are limited due to logistics and radiation exposure. We recently proposed assessing the bone healing status through continuous monitoring of the implant load, utilizing an implanted sensor system, the Fracture Monitor. The device telemetrically transmits statistically derived implant parameters via the patient’s mobile phone to assist physicians in diagnostics and treatment decision-making. This preclinical study aims to systematically investigate the device safety and performance in an animal setting. Materials and Methods: Mid-shaft tibial osteotomies of different sizes (0.6–30 mm) were created in eleven Swiss mountain sheep. The bones were stabilized with either a conventional Titanium or stainless-steel locking plate equipped with a Fracture Monitor. Data were continuously collected over the device’s lifetime. Conventional radiographs and clinical CT scans were taken longitudinally over the study period. The radiographs were systematically scored and CTs were evaluated for normalized bone volume in the defect. The animals were euthanized after 9 months. The sensor output was correlated with the radiologic parameters. Tissue samples from the device location were histologically examined. Results: The sensors functioned autonomously for 6.5–8.4 months until energy depletion. No macroscopic or microscopic adverse effects from device implantation were observed. The relative implant loads at 4 and 8 weeks post-operation correlated significantly with the radiographic scores and with the normalized bone volume metric. Conclusions: Continuous implant load monitoring appears as a relevant approach to support and objectify fracture healing assessments and carries a strong potential to enable patient-tailored rehabilitation in the future.

On the Design and Development of Planar Monopole Antenna for Bone Crack/Void Detection

In this study, the design of a compact narrowband monopole antenna for bone crack detection is presented. The proposed antenna consists of a modified hexagon-shaped radiator with six triangular slits integrated on its bottom periphery, a rectangular-shaped ground plane, and a microstrip feed line of 50 Ω. The antenna is fabricated on the FR-4 substrate with a thickness of 1.6 mm, an overall size of 32 mm × 30 mm, and electrical dimensions of 0.13λ0 × 0.122λ0, where λ0 is the free space wavelength at 2.45 GHz. The resonant frequency of the designed antenna is 2.45 GHz. The antenna offers a gain of 1.68 dB and an efficiency of 85.3%. The presence of a crack in the bone is detected by observing the shift in the peak resonating frequency of the antenna. This method can detect bone fractures in a noninvasive manner. The human arm model is constructed, and the effect of bone cracks of different lengths on the resonating frequency is investigated. The pig bone and tissues are used to validate the simulated results. The simulated results are in agreement with the measured outcomes. Also, the specific absorption rate (SAR) of the antenna is calculated and found to be less than 0.57 W/kg. The designed monopole antenna has several advantages, including a small footprint, straightforward design, low cost, and easy integration with other devices. The proposed method is suitable for primary-level bone crack diagnosis.

Bone Healing Monitoring in Bone Lengthening Using Bioimpedance

The most common technique of orthopedic surgical procedure for the correction of deformities is bone lengthening by “distraction osteogenesis,” which requires periodic and ongoing bone assessment following surgery. Bone impedance is a noninvasive, quantitative method of assessing bone fracture healing. The purpose of this study was to monitor bone healing and determine when fixation devices should be removed. The left tibia of eight male New Zealand white rabbits (2.4 ± 0.4 kg) undergoing osteotomy was attached with a mini-external fixator. The bone length was increased by 1 cm one week after surgery by distracting it 1 mm per day. Before and after osteotomy, as well as every week after, bone impedance was measured in seven frequency ranges using an EVAL-AD5933EBZ board. Three orthopedic surgeons analyzed the radiographs using the Radiographic Union Scale for Tibial (RUST) score. The Kappa Fleiss coefficient was used to determine surgeon agreement, and the Spearman rank correlation coefficient was used to find out the relationship between impedance measurements and RUST scores. Finally, the device removal time was calculated by comparing the bone impedance to the preosteotomy impedance. The agreement of three orthopedic surgeons on radiographs had a Fleiss' Kappa coefficient of 49%, indicating a moderate level of agreement. The Spearman rank correlation coefficient was 0.43, indicating that impedance and radiographic techniques have a direct relationship. Impedance is expected to be used to monitor fractured or lengthened bones in a noninvasive, low-cost, portable, and straightforward manner. Furthermore, when used in conjunction with other qualitative methods such as radiography, impedance can be useful in determining the precise time of device removal.

Adapting non-medical applications for medical use: Ethical limits, coverage, and validation

The widespread adoption of smartphones and other mobile devices amongst healthcare providers opened new possibilities arising from the use of non-medical apps, social media, meeting platforms, and non-medical devices with intended medical purposes, thus expanding the communication and imaging chat systems between these professionals and their patients, as well as amongst healthcare professionals. However, adapting non-medical applications, social media, videoconference platforms and devices for medical use present potential limitations, barriers, and risks, which should be fully recognized to reduce crossing the fine line between ethical and unethical. In the herein study, we analyse the ethical limits, coverage, and validation of non-medical applications adapted for medical use. Level of evidence: IV (evidence from well-designed case-control or cohort studies).

Mixed oxide nanotubes in nanomedicine: A dead-end or a bridge to the future?

Nanomedicine has seen a significant rise in the development of new research tools and clinically functional devices. In this regard, significant advances and new commercial applications are expected in the pharmaceutical and orthopedic industries. For advanced orthopedic implant technologies, appropriate nanoscale surface modifications are highly effective strategies and are widely studied in the literature for improving implant performance. It is well-established that implants with nanotubular surfaces show a drastic improvement in new bone creation and gene expression compared to implants without nanotopography. Nevertheless, the scientific and clinical understanding of mixed oxide nanotubes (MONs) and their potential applications, especially in biomedical applications are still in the early stages of development. This review aims to establish a credible platform for the current and future roles of MONs in nanomedicine, particularly in advanced orthopedic implants. We first introduce the concept of MONs and then discuss the preparation strategies. This is followed by a review of the recent advancement of MONs in biomedical applications, including mineralization abilities, biocompatibility, antibacterial activity, cell culture, and animal testing, as well as clinical possibilities. To conclude, we propose that the combination of nanotubular surface modification with incorporating sensor allows clinicians to precisely record patient data as a critical contributor to evidence-based medicine.

The Life of a Fracture: Biologic Progression, Healing Gone Awry, and Evaluation of Union

New knowledge about the molecular biology of fracture-healing provides opportunities for intervention and reduction of risk for specific phases that are affected by disease and medications. Modifiable and nonmodifiable risk factors can prolong healing, and the informed clinician should optimize each patient to provide the best chance for union. Techniques to monitor progression of fracture-healing have not changed substantially over time; new objective modalities are needed.

Bone Fracture Sensing Using Ultrasound Pitch-Catch Measurements: A Proof-of-Principle Study

The most common imaging method used to diagnose and monitor bone fractures and healing is multiple radiographic images performed by highly trained professionals with expensive equipment that can expose patients to high levels of ionizing radiation. Here we introduce and illustrate proof-of-concept of a potential alternative method for measuring bone fractures: ultrasound pitch-catch measurement technique. Measurements are performed with two piezoelectric transducers, housed in standard orthopedic screws and fixed on either side of simulated fractures, with and without an orthopedic plate, in ex vivo pig limb bones. Using this measurement method, we were able to detect significant differences between uncut and 2-, 5- and 10-mm-deep bone cuts using a two-sided t-test with an α level of 5%.

Electrochemical methods to enhance osseointegrated prostheses

Osseointegrated (OI) prosthetic limbs have been shown to provide an advantageous treatment option for amputees. In order for the OI prosthesis to be successful, the titanium implant must rapidly achieve and maintain proper integration with the bone tissue and remain free of infection. Electrochemical methods can be utilized to control and/or monitor the interfacial microenvironment where the titanium implant interacts with the biological system (host bone tissue or bacteria). This review will summarize the current understanding of how electrochemical modalities can influence bone tissue and bacteria with specific emphasis on applications where the metallic prosthesis itself can be utilized directly as a stimulating electrode for enhanced osseointegration and infection control. In addition, a summary of electrochemical impedance sensing techniques that could be used to potentially assess osseointegration and infection status of the metallic prosthesis is presented.

Smart Bioimpedance Spectroscopy Device for Body Composition Estimation

The purpose of this work is to describe a first approach to a smart bioimpedance spectroscopy device for its application to the estimation of body composition. The proposed device is capable of carrying out bioimpedance measurements in multiple configurable frequencies, processing the data to obtain the modulus and the bioimpedance phase in each of the frequencies, and transmitting the processed information wirelessly. Another novelty of this work is a new algorithm for the identification of Cole model parameters, which is the basis of body composition estimation through bioimpedance spectroscopy analysis. Against other proposals, the main advantages of the proposed method are its robustness against parasitic effects by employing an extended version of Cole model with phase delay and three dispersions, its simplicity and low computational load. The results obtained in a validation study with respiratory patients show the accuracy and feasibility of the proposed technology for bioimpedance measurements. The precision and validity of the algorithm was also proven in a validation study with peritoneal dialysis patients. The proposed method was the most accurate compared with other existing algorithms. Moreover, in those cases affected by parasitic effects the proposed algorithm provided better approximations to the bioimpedance values than a reference device.