Employing direct electromagnetic coupling to assess acute fracture healing: An ovine model assessment.

OBJECTIVES: This study explored the efficacy of collecting temporal fracture site compliance data via an advanced direct electromagnetic coupling (DEC) system equipped with a Vivaldi-type antenna, novel calibration technique, and multi-antenna setup (termed maDEC) as an approach to monitor acute fracture healing progress in a translational large animal model. The overarching goal of this approach was to provide insights into the acute healing dynamics, offering a promising avenue for optimizing fracture management strategies. METHODS: A sample of twelve sheep, subjected to ostectomies and intramedullary nail fixations, was divided into two groups, simulating normal and impaired healing scenarios. Sequential maDEC compliance or stiffness measurements and radiographs were taken from the surgery until euthanasia at four or eight weeks and were subsequently compared with post-sacrifice biomechanical, micro-CT, and histological findings. RESULTS: The results showed that the maDEC system offered straightforward quantification of fracture site compliance via a multiantenna array. Notably, the rate of change in the maDEC-measured bending stiffness significantly varied between normal and impaired healing groups during both the 4-week (p = 0.04) and 8-week (p = 0.02) periods. In contrast, radiographically derived mRUST healing measurements displayed no significant differences between the groups (p = 0.46). Moreover, the cumulative normalized stiffness maDEC data significantly correlated with post-sacrifice mechanical strength (r2 = 0.80, p < 0.001), micro-CT measurements of bone volume fraction (r2 = 0.60, p = 0.003), and density (r2 = 0.60, p = 0.003), and histomorphometric measurements of new bone area fraction (r2 = 0.61, p = 0.003) and new bone area (r2 = 0.60, p < 0.001). CONCLUSIONS: These data indicate that the enhanced maDEC system provides a non-invasive, accurate method to monitor fracture healing during the acute healing phase, showing distinct stiffness profiles between normal and impaired healing groups and offering critical insights into the healing process's progress and efficiency.

Direct electromagnetic coupling to determine diagnostic bone fracture stiffness.

Background: Rapid prediction of adverse bone fracture healing outcome (e.g., nonunion and/or delayed union) is essential to advise adjunct therapies to reduce patient suffering and improving healing outcome. Radiographic diagnostic methods remain ineffective during early healing, resulting in average nonunion diagnosis times surpassing six months. To address this clinical deficit, we developed a novel diagnostic device to predict fracture healing outcome by noninvasive telemetric measurements of fracture bending stiffness. This study evaluated the hypothesis that our diagnostic antenna system is capable of accurately measuring temporal fracture healing stiffness, and advises the utility of this data for expedited prediction of healing outcomes during early (≤3 weeks) fracture recovery. Methods: Fracture repair was simulated, in reverse chronology, by progressively destabilizing cadaveric ovine metatarsals (n=8) stabilized via locking plate fixation. Bending stiffness of each fracture state were predicted using a novel direct electromagnetic coupling diagnostic system, and results were compared to values from material testing (MT) methods. While direct calculation of fracture stiffness in a simplistic cadaver model is possible, comparable analysis of the innumerable permutations of fracture and treatment type is not feasible. Thus, clinical feasibility of direct electromagnetic coupling was explored by parametric finite element (FE) analyses (n=1,632 simulations). Implant mechanics were simulated throughout the course of healing for cases with variations to fracture size, implant type, implant structure, and implant material. Results: For all fracture states, stiffness values predicted by the direct electromagnetic coupling system were not significantly different than those quantified by in vitro MT methods [P=0.587, P=0.985, P=0.975; for comparing intact, destabilized, and fully fractured (FF) states; respectively]. In comparable models, the total implant deflection reduction (from FF to intact states) was less than 10% different between direct electromagnetic coupling measurements (82.2 µm) and FE predictions (74.7 µm). For all treatment parameters, FE analyses predicted nonlinear reduction in bending induced implant midspan deflections for increasing callus stiffness. Conclusions: This technology demonstrates potential as a noninvasive clinical tool to accurately quantify healing fracture stiffness to augment and expedite healing outcome predictions made using radiographic imaging.

Vivaldi Antennas for Contactless Sensing of Implant Deflections and Stiffness for Orthopaedic Applications.

The implementation of novel coaxial dipole antennas has been shown to be a satisfactory diagnostic platform for the prediction of orthopaedic bone fracture healing outcomes. These techniques require mechanical deflection of implanted metallic hardware (i.e., rods and plates), which, when loaded, produce measurable changes in the resonant frequency of the adjacent antenna. Despite promising initial results, the coiled coaxial antenna design is limited by large antenna sizes and nonlinearity in the resonant frequency data. The purpose of this study was to develop two Vivaldi antennas (a.k.a., "standard" and "miniaturized") to address these challenges. Antenna behaviors were first computationally modeled prior to prototype fabrication. In subsequent benchtop tests, metallic plate segments were displaced from the prototype antennas via precision linear actuator while measuring resultant change in resonant frequency. Close agreement was observed between computational and benchtop results, where antennas were highly sensitive to small displacements of the metallic hardware, with sensitivity decreasing nonlinearly with increasing distance. Greater sensitivity was observed for the miniaturized design for both stainless steel and titanium implants. Additionally, these data demonstrated that by taking resonant frequency data during implant displacement and then again during antenna displacement from the same sample, via linear actuators, that "antenna calibration procedures" could be used to enable a clinically relevant quantification of fracture stiffness from the raw resonant frequency data. These improvements mitigate diagnostic challenges associated with nonlinear resonant frequency response seen in previous antenna designs.

Diagnostic prediction of ovine fracture healing outcomes via a novel multi-location direct electromagnetic coupling antenna.

BACKGROUND: Expedient prediction of adverse bone fracture healing (delayed- or non-union) is necessary to advise secondary treatments for improving healing outcome to minimize patient suffering. Radiographic imaging, the current standard diagnostic, remains largely ineffective at predicting nonunions during the early stages of fracture healing resulting in mean nonunion diagnosis times exceeding six months. Thus, there remains a clinical deficit necessitating improved diagnostic techniques. It was hypothesized that adverse fracture healing expresses impaired biological progression at the fracture site, thus resulting in reduced temporal progression of fracture site stiffness which may be quantified prior to the appearance of radiographic indicators of fracture healing (i.e., calcified tissue). METHODS: A novel multi-location direct electromagnetic coupling antenna was developed to diagnose relative changes in the stiffness of fractures treated by metallic orthopaedic hardware. The efficacy of this diagnostic was evaluated during fracture healing simulated by progressive destabilization of cadaveric ovine metatarsals treated by locking plate fixation (n=8). An ovine in vivo comparative fracture study (n=8) was then utilized to better characterize the performance of the developed diagnostic in a clinically translatable setting. In vivo measurements using the developed diagnostic were compared to weekly radiographic images and postmortem biomechanical, histological, and micro computed tomography analyses. RESULTS: For all cadaveric samples, the novel direct electromagnetic coupling antenna displayed significant differences at the fracture site (P<0.05) when measuring a fully fractured sample versus partially intact and fully intact fracture states. In subsequent in vivo fracture models, this technology detected significant differences (P<0.001) in fractures trending towards delayed healing during the first 30 days post-fracture. CONCLUSIONS: This technology, relative to traditional X-ray imaging, exhibits potential to greatly expedite clinical diagnosis of fracture nonunion, thus warranting additional technological development.

Utilizing Multiple BioMEMS Sensors to Monitor Orthopaedic Strain and Predict Bone Fracture Healing.

Current diagnostic modalities, such as radiographs or computed tomography, exhibit limited ability to predict the outcome of bone fracture healing. Failed fracture healing after orthopaedic surgical treatments are typically treated by secondary surgery; however, the negative correlation of time between primary and secondary surgeries with resultant health outcome and medical cost accumulation drives the need for improved diagnostic tools. This study describes the simultaneous use of multiple (n = 5) implantable flexible substrate wireless microelectromechanical (fsBioMEMS) sensors adhered to an intramedullary nail (IMN) to quantify the biomechanical environment along the length of fracture fixation hardware during simulated healing in ex vivo ovine tibiae. This study further describes the development of an antenna array for interrogation of five fsBioMEMS sensors simultaneously, and quantifies the ability of these sensors to transmit signal through overlaying soft tissues. The ex vivo data indicated significant differences associated with sensor location on the IMN (p < 0.01) and fracture state (p < 0.01). These data indicate that the fsBioMEMS sensor can serve as a tool to diagnose the current state of fracture healing, and further supports the use of the fsBioMEMS as a means to predict fracture healing due to the known existence of latency between changes in fracture site material properties and radiographic changes. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1873-1880, 2019.

Ex vivo evaluation of a novel surgical guide on the accuracy of closing wedge osteotomies.

OBJECTIVE: To determine the influence of a novel surgical guide on the accuracy and technical difficulty of closing wedge osteotomies (CWO). STUDY DESIGN: Ex vivo experimental study. SAMPLE POPULATION: Canine tibia models (n = 40). METHODS: A 20° cranial CWO (CCWO) was created without (standard procedure; STCCWO) or with the aid of a novel wedge osteotomy guide (WOCCWO). Procedures were performed by diplomate (n = 4) and resident (n = 6) surgeons, with each performing 2 STCCWO followed by 2 WOCCWO. To prevent bias, surgeons were unaware of the study purpose until after completing the STCCWO. The wedges were evaluated by comparing the deviation from the 20° target angle, divergence of the 2 osteotomies (osteotomy divergence angle [ODA]), and measurements of the wedge height at the caudomedial cortex (CMC) and caudolateral cortex (CLC). Technique difficulty was explored through a surgeon questionnaire. RESULTS: The WOCCWO resulted in smaller mean ODA (WOCCWO = 0.86°, SD ± 0.38°, P < .001), and smaller mean difference between CMC and CLC (WOCCWO = 0.29 mm, SD ± 0.19, P < .001) than for the STCCWO (4.22°, SD ± 2.16° and 1.39 mm, SD ± 0.65 respectively). Deviation from the target 20° wedge angle was greater after STCCWO (1.46°, SD ± 1.27°) than after WOCCWO (0.53°, SD ± 0.33°, P = .004). No difference was reported regarding the difficulty of the procedures, but resident surgeons stated that they were more likely to use the guide in a clinical setting compared with diplomates. CONCLUSION: The wedge osteotomy guide improved the accuracy of CCWO compared with standard technique. CLINICAL SIGNIFICANCE: The clinical significance of the differences detected in this study is unclear and warrants in vivo investigation.

Epidemiological study of failures of the Jaipur Foot.

OBJECTIVE: The purpose of this study was to examine effects of usage and demographics on damage to the Jaipur Foot prosthesis as well as the epidemiology and etiology of amputations performed at Santokba Durlabjhi Memorial Hospital (SDMH) in Jaipur, India. DESIGN: Total time spent standing, total time spent wearing and total distance walked were compared against severity and location of damage to the prosthesis. Time between initial fitting and follow-up visit for damaged prosthetic was also considered in this analysis. A novel damage severity scale based on prosthesis functionality is presented along with a damage location legend. RESULTS: Patients from 10 different states and two territories throughout India were included in the study. No main effects were found to be statistically significant in predicting severity or location of damage. Only the interaction between a patient's total time spent standing and their total time spent wearing the prosthesis as well as the interaction between a patient's total time spent standing and total distance walked was significant in predicting location of damage to the Jaipur Foot (p = .0327, p = .0278, respectively). CONCLUSIONS: The lack of significant usage factor effect on damage severity or location could support previous findings that lack standardization in materials and manufacturing processes, which is the major drawback of the Jaipur Foot. Implications for Rehabilitation The Jaipur Foot is a safe, reliable and stable product as no abrupt breakage or sudden falls causing injury to the patient were noted. Hence, it is a safe rehabilitation device for lost limbs. The population can squat and sit cross-legged while wearing the prosthetic foot and it does not affect damage severity or location of damage, allowing for these activities to be performed while rehabilitating. The manufacturing of the foot needs to be standardized to improve life of foot. Total time spent standing, total time spent wearing and total distance walked were not predictive of severity or location of damage to the prosthesis, hence providing patient guidelines for activity during rehabilitation.