FBG-Based Estimation of External Forces Along Flexible Instrument Bodies

A variety of medical treatment and diagnostic procedures rely on flexible instruments such as catheters and endoscopes to navigate through tortuous and soft anatomies like the vasculature. Knowledge of the interaction forces between these flexible instruments and patient anatomy is extremely valuable. This can aid interventionalists in having improved awareness and decision-making abilities, efficient navigation, and increased procedural safety. In many applications, force interactions are inherently distributed. While knowledge of their locations and magnitudes is highly important, retrieving this information from instruments with conventional dimensions is far from trivial. Robust and reliable methods have not yet been found for this purpose. In this work, we present two new approaches to estimate the location, magnitude, and number of external point and distributed forces applied to flexible and elastic instrument bodies. Both methods employ the knowledge of the instrument’s curvature profile. The former is based on piecewise polynomial-based curvature segmentation, whereas the latter on model-based parameter estimation. The proposed methods make use of Cosserat rod theory to model the instrument and provide force estimates at rates over 30 Hz. Experiments on a Nitinol rod embedded with a multi-core fiber, inscribed with fiber Bragg gratings, illustrate the feasibility of the proposed methods with mean force error reaching 7.3% of the maximum applied force, for the point load case. Furthermore, simulations of a rod subjected to two distributed loads with varying magnitudes and locations show a mean force estimation error of 1.6% of the maximum applied force.

Evaluation of a curved surgical prototype in a human larynx

Purpose It is not always possible to create linear access to the larynx using a rigid operating laryngoscope for microlaryngoscopy. In this study, we evaluate the usability of a novel curved surgical prototype with flexible instruments for the larynx (sMAC) in a simulation dummy and human body donor. Methods In a user study (n = 6), head and neck surgeons as well as medical students tested the system for visualization quality and accessibility of laryngeal landmarks on an intubation dummy and human cadaver. A biopsy of the epiglottis was taken from the body donor. Photographic and time documentation was carried out. Results The sMAC system demonstrated general feasibility for laryngeal surgery. Unlike conventional microlaryngoscopy, all landmarks could be visualized and manipulated in both setups. Biopsy removal was possible. Visibility of the surgical field remained largely unobstructed even with an endotracheal tube in place. Overall handling of the sMAC prototype was satisfactorily feasible at all times. Conclusion The sMAC system could offer an alternative for patients, where microlaryngoscopy is not applicable. A clinical trial has to clarify if the system benefits in clinical routine.

All Inside Intraepiphyseal ACL Reconstruction Using Flexible Curved Instrumentation and Intraoperative Fluoroscopy in a Skeletally Immature Patient

Case. A 13-year-old skeletally immature female presenting with an anterior cruciate ligament (ACL) rupture after a noncontact injury was treated with an intraepiphyseal ACL reconstruction. Flexible instrumentation was utilized to drill a femoral tunnel with an anatomic starting point, with a trajectory that curved inferolaterally away from the physis. At three years postoperatively, she had returned to her preinjury functioning and did not display any lower limb length growth abnormalities. Conclusions. The novel application of curved guides and flexible instruments, with intraoperative fluoroscopy, facilitated growth plate avoidance and a successful outcome of ACL reconstruction in a skeletally immature patient.

Design of Contact-aided Compliant Flexure Hinge Mechanism Using Superelastic Nitinol

This paper presents a novel miniature contact-aided compliant mechanism (CCM) that includes flexure hinges and contact-aided structures. This continuum mechanism comprises a nickel–titanium alloy (Nitinol) tube with CCM cut via laser micromachining and actuated using wires bending from −80° to +80° in four directions. The proposed CCM has the following merits: perfect capacity for deflection around the centroid, a self-backbone, and improved torsional as well as tensile strengths. Further, it is pre-assembled. First, kinematic and static models are used to predict the bending behaviour of the mechanism. Thereafter, the maximum strain is evaluated using finite element analysis (FEA) then compared with the static models. Finally, the performances of the mechanism are characterized by experiments. The results validate the proposed models and demonstrate that the torsional and tensile strengths of the proposed CCM increased by more than 100% and 30%, respectively, compared with those of conventional non-CCMs with a similar fatigue life. Moreover, with the integrated forceps and probe, the proposed mechanism can achieve object transfer and square trajectory scanning of the targeted location. These experimental results demonstrate the potential clinical value of the proposed mechanism and provide important insights into the design of long and flexible instruments for endoscopic surgery.

Force effects on anatomical structures in transoral surgery − videolaryngoscopic prototype vs. conventional direct microlaryngoscopy

Direct microlaryngoscopy is a frequently performed procedure in otorhinolaryngology, whereby considerable force is exerted on the patients’ teeth, as well as oropharyngeal and laryngeal structures. Especially in cases of a challenging exposure of the anterior commissure, the cervical spine needs to be brought into a hyperextended position, which is not possible in every patient. Therefore, the conflict between the straight rigid microlaryngoscope and the curvature of the oropharyngeal corridor frequently results in tissue trauma with the consequence of teeth fracture, hematoma or nerve injury. We have developed the s-MAC system, a hyper-angulated video laryngoscope with flexible instruments for transoral laryngeal surgery, which so far shows high feasibility in preclinical studies. Due to its curved shape it may exert less force on teeth and supraglottis as conventional direct microlaryngoscopy. We quantified the effects of these two surgical systems using flexible pressure sensors in two different scenarios: a mobile, hyperextended and an immobile cervical spine of the dummy, to simulate a challenging airway. We could demonstrate a 21% (40% with immobilized cervical spine) reduction of the average peak force acting on the maxillary incisors and a 55% (65% with immobilized cervical spine) reduction of the average intraoperative force on the supraglottis. The developed prototype applied therefore significantly less force on upper front teeth and supraglottis as compared to conventional direct microlaryngoscopy – especially in the case of an immobilized cervical spine.

Islamic Law in the jurisdiction of International Financial Centers: comparative legal analysis

The article analyzes the modern mechanisms and ways of adapting the Islamic law principles and norms to the regulation of financial relations. Taking into account the significance of fiqh as a legal doctrine that interprets religious prescriptions for law enforcement, the key features of the Islamic law institutions in the context of the Islamic economy model development are identified. The object of the comparative legal analysis in the article is the jurisdiction of international financial centers as territories with a special legal regime for conducting business. Its legal status is fixed in special legal acts, thus contributing to the formation of flexible instruments of legal regulation in view of the correlation with the norms of the national legal order. International financial centers are presented as an example of the formation of global legal institutions in Western countries as well as those in Southeast Asia and the Middle East. The author argues that Islamic financeas a way of adapting Islamic law principles to the regulation of business activitiesis a mandatory element of a legal environment for international financial centers.