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Finite element simulation of various strategies for CD correction.

The scoliosis surgery using the Cotrel-Dubousset instrumentation is a complex three dimensional correction. This surgery was first simulated for a given patient using a personalized finite element model: the geometry was extracted from a 3D stereoradiographic reconstruction and mechanical properties were personalized using lateral bending tests. Finally, three alternative surgical strategies were simulated in order to analyze their effects on spine postoperative configuration. First results are promising and should allow surgeons to objectively analyze various strategies or techniques.

Biomechanical Phenomena↗

The Eindhoven laparoscopic cholecystectomy training course--improving operating room performance using virtual reality training: results from the first E.A.E.S. accredited virtual reality trainings curriculum.

BACKGROUND: This study was undertaken to investigate operating room performance of surgical residents, after participating in the Eindhoven virtual reality laparoscopic cholecystectomy training course. This course is the first formal surgical resident trainings course, using a variety of complementary virtual reality (VR) skills training simulation in order to prepare surgical residents for their first laparoscopic cholecystectomy. The course was granted EAES certification. METHODS: The four-day course is based on multimedia and multimodality approach. A variety of increasingly difficult simulation training sessions, next to intimate focus-group "knowledge sessions" are included. Both basic and procedural VR simulation is featured, using MIST-VR and the Xitacts' LapChol simulation software. The operating room performance of twelve surgical residents who participated in the course and twelve case-control counterparts were compared. The case-control group was matched for clinical number laparoscopic cholecystectomy performance (maximum of 4 procedures). Two observers analyzed a randomly mixed videotape, featuring the part of the "clip-and-cut" procedure of the laparoscopic cholecystectomy, and were blinded for participants' group status. Structured questionnaires including multiple observation scales were used to assess performance. RESULTS: Residents of both the experimental and control group did not differ in demographic parameters, except for number of laparoscopic cholecystectomies in favor of the control group (p-value 0.008). Both observers judge the experimental group to perform significantly better (p-value 0.004 and 0.013). Experimental group residents valued their course highly in terms of their laparoscopic surgical skills improvement and the use of VR simulators in the surgical curriculum. CONCLUSIONS: The Eindhoven Virtual Reality laparoscopic cholecystectomy training course improves surgical skill in the operating room above the level of residents trained by a variety of other training methods.

Adult↗

A haptics based simulator for laparoscopic pyeloplasty.

We present a methodology for modeling the surgical procedures involved in robotics-assisted Pyeloplasty, which is a minimally invasive surgical procedure for correcting a kidney ureteropelvic junction obstruction. The simulator facilitates surgical training of laparoscopic pyeloplasty by providing both visual and haptic feedback to the trainee.

Canada↗

Construct validity: experts and novices performing on the Xitact LS500 laparoscopy simulator.

BACKGROUND: This study was undertaken to establish construct validity of the Xitact LS500, a virtual reality laparoscopic cholecystectomy simulator. The primary research statement is: "The clip-and-cut task on the Xitact LS500 virtual reality laparoscopic cholecystectomy simulator mimics the surgical procedure of the clipping and cutting of the cystic duct and artery during the laparoscopic cholecystectomy adequately." METHODS: According to the level of experience of the surgeon, an "expert group opinion" was formed resulting from 37 surgeons having performed over 100 laparoscopic cholecystectomies, and a "novice group opinion" was formed resulting of 37 surgeons having no experience at all with performing laparoscopic cholecystectomy. Participants received an instructed hands-on "tour" on the Xitact simulator and performed three formal simulation runs. RESULTS: The "novice group" is younger and more surgeons are female. Performance scores in the "expert" group are significantly higher on the second (p value 0.011) and third (p value 0.005) run, compared to the novices' scores. Experts are significantly faster on completion of all three runs. There is an increase in score over runs in both groups, which is statistically significant in the "expert group." Less than one-third of surgeons in either group are able to correctly predict their performance score as generated by Xitact. Both "experts" and "novices" feel it is useful to train with Xitact LS500 in the surgical curriculum. CONCLUSIONS: Three hypotheses, formulated to operationalize the primary research statement, could be answered affirmatively. Although further validation studies are needed, the Xitact LS500 simulator seems to be able to discriminate between expert and novice surgeons in this research setting, and thus the construct for this setting is considered to be valid.

Adult↗

Noninvasive three-dimensional assessment of femoroacetabular impingement.

A CT-based method ("HipMotion") for the noninvasive three-dimensional assessment of femoroacetabular impingement (FAI) was developed, validated, and applied in a clinical pilot study. The method allows for the anatomically based calculation of hip range of motion (ROM), the exact location of the impingement zone, and the simulation of quantified surgical maneuvers for FAI. The accuracy of HipMotion was 0.7 +/- 3.1 degrees in a plastic bone setup and -5.0 +/- 5.6 degrees in a cadaver setup. Reliability and reproducibility were excellent [intraclass correlation coefficient (ICC) > 0.87] for all measures except external rotation (ICC = 0.48). The normal ROM was determined from a cohort of 150 patients and was compared to 31 consecutive hips with FAI. Patients with FAI had a significantly decreased flexion, internal rotation, and abduction in comparison to normal hips (p < 0.001). Normal hip flexion and internal rotation are generally overestimated in a number of orthopedic textbooks. HipMotion is a useful tool for further assessment of impinging hips and for appropriate planning of the necessary amount of surgical intervention, which represents the basis for future computer-assisted treatment of FAI with less invasive surgical approaches, such as hip arthroscopy.

Acetabulum↗

[IMOLA -- a new larynx model for surgical training. Education in transoral laser microsurgery of the upper airways].

BACKGROUND: Education in laser microsurgery is generally acquired under the supervision of an experienced surgeon. During training phases, however, increased complication rates may occur. Viable models for training are therefore important. METHODS: Larynx models should be anatomically accurate in size, form and texture, and be able to simulate normal as well as pathological findings. RESULTS: The main component is gelatin. Elasticity and thermal qualities can be modified by additives. We have been able to develop a synthetic larynx model for CO(2)-laser surgery that closely resembles the physical and tactile qualities of human tissue. Further modification of the material produced cutting characteristics for CO(2)-laser similar to human tissue. CONCLUSION: The new larynx model allows the simulation of typical surgical situations. Surgeons in training can practice even difficult surgical procedures at low costs and without putting patients at risk, before carrying out the procedure on patients.

Biomimetics↗

Emerging technologies for surgery in the 21st century.

Laparoscopic surgery is a transition technology that marked the beginning of the information age revolution for surgery. Telepresence surgery, robotics, tele-education, and telementoring are the next step in the revolution. Using computer-aided systems such as robotics and image-guided surgery, the next generation of surgical systems will be more sophisticated and will permit surgeons to perform surgical procedures beyond the current limitations of human performance, especially at the microscale or on moving organs. More fundamentally, there will be an increased reliance on 3-dimensional images of the patient, gathered by computed tomography, magnetic resonance imaging, ultrasound, or other scanning techniques, to integrate the entire spectrum of surgical care from diagnosis to preoperative planning to intraoperative navigation to education through simulation. By working through the computer-generated image, first with preoperative planning and then during telepresence or image-guided procedures, new approaches to surgery will be discovered. These technologies are complemented by new educational opportunities, such as tele-education, surgical simulation, and a Web-based curriculum. Telementoring will permit further extension of the educational process directly into the operating room.

Forecasting↗

The value of virtual reality-simulator training in the development of laparoscopic surgical skills.

OBJECTIVE: To determine the effectiveness of virtual reality (VR) training in improving the surgical skills of medical students and gynecologic trainees. DESIGN: A prospective observational study to assess the changes observed in objectively measured surgical performance after VR training. SETTING AND POPULATION: University teaching hospital and the laboratories of the University of Western Australia. PARTICIPANTS: Fifteen 5th-year medical students, six junior-doctor trainees (years 1-3), and eight senior trainees (years 4-6). INTERVENTIONS: Standard gynecologic procedures before and after VR training were undertaken on sheep. The procedures were video-recorded and edited to blind the scorer as to identity and seniority of the operator. The procedures were scored using a combination of operative time and penalties for surgical errors. The surgical scores were correlated with the VR scores. MEASUREMENTS AND MAIN RESULTS: Operative skills were assessed using a combination score compiled from scores obtained while undertaking salpingectomy, salpingotomy, and tubal clipping. Virtual reality scores were also a combination score derived from summation of various computer-calculated measures of time and accuracy in undertaking two standardized exercises. RESULTS: The baseline VR scores were significantly related to the overall pre-training scores (salpingectomy p = .032). A better initial VR score was also predictive of better surgical performance. The initial VR score was also predictive of improvement observed between baseline and post-training (p = .004). CONCLUSION: Virtual reality training is of value in improving surgical skills in the clinical environment. It appears to be of most value in the earliest stages of training. These data suggest that serious consideration should be given to incorporating VR training into the training program of obstetricians and gynecologists at an early stage.

Adult↗

Deep pectoral myopathy: an experimental simulation in the fowl.

Surgical occlusion of the subclavian artery of domestic fowls has been found to induce a condition closely resembling, in location and histopathology, the deep pectoral myopathy of turkeys. The operative procedure is described and the significance of the collateral blood supply in the pathogenesis of the lesion is briefly discussed.

Animals↗

Modeling biologic soft tissues for haptic feedback with an hybrid multiresolution method.

The simulation of realistic surgical procedures requires specialized optimized algorithms for the models of organs and tissues, which should comply both with accuracy of results and run-time computation. This paper provides a numerical method for implementing deformation of soft tissues for haptic feedback that makes use of a hybrid pre-computation scheme.

Algorithms↗

VIRGY: a virtual reality and force feedback based endoscopic surgery simulator.

This paper describes the VIRGY project at the VRAI Group (Virtual Reality and Active Interface), Swiss Federal Institute of Technology (Lausanne, Switzerland). Since 1994, we have been investigating a variety of virtual-reality based methods for simulating laparoscopic surgery procedures. Our goal is to develop an endoscopic surgical training tool which realistically simulates the interactions between one or more surgical instruments and gastrointestinal organs. To support real-time interaction and manipulation between instruments and organs, we have developed several novel graphic simulation techniques. In particular, we are using live video texturing to achieve dynamic effects such as bleeding or vaporization of fatty tissues. Special texture manipulations allows us to generate pulsing objects while minimizing processor load. Additionally, we have created a new surface deformation algorithm which enables real-time deformations under external constraints. Lastly, we have developed a new 3D object definition which allows us to perform operations such as total or partial object cuttings, as well as to selectively render objects with different levels of detail. To provide realistic physical simulation of the forces and torques on surgical instruments encountered during an operation, we have also designed a new haptic device dedicated to endososcopic surgery constraints. We are using special interpolation and extrapolation techniques to integrate our 25 Hz visual simulation with the 300 Hz feedback required for realistic tactile interaction. The fully VIRGY simulator has been tested by surgeons and the quality of both our visual and haptic simulation has been judged sufficient for training basic surgery gestures.

Algorithms↗

The role of atrial vessels in aortic root and mitral valve operations.

BACKGROUND: For the last 90 years, several authors have focused on studying the blood supply to the conduction system in the human heart. However, an important gap has been maintained between this topic and cardiac surgical procedures when they should have been closely matched. This paper is aimed at clarifying the morphology of the conduction system and its blood supply and assessing its role in cardiac surgical procedures. METHODS: Twenty human hearts were dissected after antegrade and retrograde injection. After dissection, different surgical procedures were simulated. Finally, we assessed the damage that these procedures might have caused either to the conduction system or to the vessels supplying it. RESULTS: Kügel's artery, the right superior descending artery, and the sinoatrial node artery were found to be harmed by the surgical procedures performed. In all these cases, these vessels were supplying part of the conduction system. CONCLUSIONS: All the vascular structures described in the paper play a very important role in the blood supply to the conduction system, and they become vulnerable during aortic root and mitral valve surgical procedures.

Adolescent↗

Biomechanical simulations of scoliotic spine correction due to prone position and anaesthesia prior to surgical instrumentation.

BACKGROUND: The positioning of patients during scoliosis surgery has been shown to affect the scoliosis curve, yet positioning has not been exploited to help improve surgical outcome from a biomechanics point of view. Biomechanical models have been used to study other aspects of scoliosis. The goal of this study is to simulate the specific influence of the prone operative position and anaesthesia using a finite element model with patient personalized material properties. METHODS: A finite element model of the spine, ribcage and pelvis was created from the 3D standing geometry of two patients. To this model various positions were simulated. Initially the left and right supine pre-operative bending were simulated. Using a Box-Benkin experimental design the material properties of the intervertebral disks were personalized so that the bending simulations best matched the bending X-rays. The prone position was then simulated by applying the appropriate boundary conditions and gravity loads and the 3D geometry was compared to the X-rays taken intra-operatively. Finally an anaesthesia factor was added to the model to relax all the soft tissues. FINDINGS: The behaviour of the model improved for all three positions once the material properties were personalized. By incorporating an anaesthesia factor the results of the prone intra-operative simulation better matched the prone intra-operative X-ray. However, the anaesthesia factor was different for both patients. For the prone position simulation with anaesthesia patient 1 corrected from 62 degrees to 47 degrees and 43 degrees to 31 degrees. Patient 2 corrected from 70 degrees to 55 degrees and 40 degrees to 32 degrees for the thoracic and lumbar curves respectively. INTERPRETATION: Positioning of the patient, as well as anaesthesia, provide significant correction of the spinal deformity even before surgical instrumentation is fixed to the vertebra. The biomechanical effect of positioning should be taken into consideration by surgeons and possibly modify the support cushions accordingly to maximise 3D curve correction. The positioning is an important step that should not be overlooked by when simulating surgical correction and biomechanical models could be used to help determine optimal cushion placement.

Adolescent↗

Robotics for surgery.

Robotic technology is enhancing surgery through improved precision, stability, and dexterity. In image-guided procedures, robots use magnetic resonance and computed tomography image data to guide instruments to the treatment site. This requires new algorithms and user interfaces for planning procedures; it also requires sensors for registering the patient's anatomy with the preoperative image data. Minimally invasive procedures use remotely controlled robots that allow the surgeon to work inside the patient's body without making large incisions. Specialized mechanical designs and sensing technologies are needed to maximize dexterity under these access constraints. Robots have applications in many surgical specialties. In neurosurgery, image-guided robots can biopsy brain lesions with minimal damage to adjacent tissue. In orthopedic surgery, robots are routinely used to shape the femur to precisely fit prosthetic hip joint replacements. Robotic systems are also under development for closed-chest heart bypass, for microsurgical procedures in ophthalmology, and for surgical training and simulation. Although results from initial clinical experience is positive, issues of clinician acceptance, high capital costs, performance validation, and safety remain to be addressed.

Biomedical Engineering↗

The influence of surgical malalignment on the contact pressures of fixed and mobile bearing knee prostheses--a biomechanical study.

OBJECTIVE: To investigate the effect of surgical malalignment on contact pressures of fixed and mobile bearing knee prostheses. DESIGN: An experimental set-up was used to measure contact pressure on the tibial component of fixed and mobile bearing knee prostheses subjected to a compression load and surgical malalignment situations were simulated. BACKGROUND: Mobile bearing knee prostheses were designed to decrease tibiofemoral contact pressure by providing both high congruity and mobility. It was also assumed to accommodate surgical malalignment. However, few studies have reported the effect of malalignment of the tibiofemoral joint on contact pressure of fixed and mobile bearing knee prostheses. METHODS: Surgical malalignment situations were simulated to evaluate contact characteristics of tibial component of fixed and mobile bearing knee prostheses. The simulated malalignment conditions include the medial-lateral translation (0.5 and 1 mm), anterior-posterior translation (2 and 4 mm) and internal-external rotation (1 degrees, 3 degrees, 5 degrees and 10 degrees ) of the femoral component relative to the tibial component. Fuji pressure sensitive film was used to measure the contact pressure. RESULTS: The greatest increase of maximum contact pressure in the anterior-posterior maltranslation was 7.63% and 7.62% relative to the neutral contact situation in the fixed and mobile bearing designs respectively. In the medial-lateral maltranslation, there was 23.3% in the fixed bearing design and was 22.0% in the mobile bearing design. In the internal/external malrotation, the greatest increase of maximum contact pressure in the fixed bearing design was 27.1%, which was much higher than the mobile bearing design (22.4%). CONCLUSIONS: The mobile bearing design can reduce maximum contact pressure more significantly than the fixed bearing design when malalignment conditions of the tibiofemoral joint occurs, especially in the internal/external malrotation. The mobile bearing design offers the advantage of self-adjusting over the fixed bearing design to accommodate surgical malalignment. RELEVANCE: This study revealed that the mobile bearing design has smaller maximum contact pressures than the fixed bearing design in knee prosthesis under malalignment biomechanical tests. This result indicates that there is an advantage for a mobile bearing design over a fixed bearing design to accommodate malalignment conditions caused by surgical technique or soft tissues imbalance in total knee arthroplasty.

Arthroplasty, Replacement, Knee↗