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At least 487 records · Page 27Linked to original sources
PubMed2006

On the biomechanical stability of cementless straight conical hip stems.

The aim of the present study was to investigation in vitro the effect of deficient bone-implant contact on the primary stability of a straight conical stem. Various possible deficient contact patterns were derived from surgical simulations. The effect of stair climbing loads on the bone-implant micromotion was firstly investigated using a finite element model and then an in vitro test aimed at assessing primary stability. It was found that if the surface features are prevented from biting dense bone in a few small but critical regions, stem primary stability is completely lost. These results suggest that the surface features used in the axisymmetric stem under investigation can be too sensitive to deficient contact conditions, and thus should be augmented with additional antirotational fins. Preliminary tests showed that a stem with the addition of such fins presents good primary stability in all tested conditions.

Arthroplasty, Replacement, Hip↗
PubMed2004

Navigation as a tool to visualize bone-covered hidden structures in transfrontal approaches.

A retrospective analysis of 10 patients was performed to evaluate navigation systems in extranasal frontal skull base surgery. When performing a craniotomy following a bicoronal skin incision, the surgeon has to calculate the extent of the frontal sinus to avoid unnecessary damage to the dura or mucoceles later. Due to surgical morbidity including compression of the frontal lobe, many skull base surgeons have refused to use such an approach. Malformation or bone-destruction complicates the identification of the borders and increases the risk of side-effects. Navigation systems can be an alternative for calculating the frontal sinus outlines during surgery. In the authors' surgical procedure two different navigation systems were used. Conventional surgery using the transfrontal, transbasal or subcranial approach consisting of trepanation and craniotomy were performed, while the navigated surgical procedure was evaluated. The analysis showed that computer-assisted surgery (CAS) is applicable to extranasal frontal skull base surgery. In comparison to X-ray beam-controlled craniotomy, CAS is beneficial as it constitutes a noninvasive instrument of quality management. Furthermore, the analysis indicated that under the guidance of a navigation system a precise pre-surgical simulation is available in order to perform an optimal craniotomy and reconstruction of the frontal skull base.

Adult↗
PubMed2005

[Acute ischaemic appendicitis in rabbits: new model with histopathological study].

PURPOSE: To evaluate partial or total ischemia, through ligature with an unabsorbed thread of vessels from the vermiform appendix of rabbits, as well as the mechanical obstruction, through ligature with an unabsorbed thread at the basis of the vermiform appendix, at 1 cm from the cecum, of the acute appendicitis disease. To evaluate the histology of the appendix (normal and affected). To study the bacterium flora resident in the vermiform appendix (normal and affected) and the exudates peritonitis. METHODS: Seventy-two male rabbits (Oryctogalus cuniculus), from New Zealand lineage were used, weighing approximately 3,000 grams. The animals were divided into: pilot (A), bacterium flora (B), control (H) and experimental (C, D, E, F and G) groups, and were observed in periods of 96 and 192 hours. It was done the ligature with an unabsorbed thread of vessels from the meso appendix, and the base of the appendix within 1 cm from the cecal. In the (C) experimental group, the mechanical obstruction was carried out. In the (D, E, F and G) experimental groups, the ischemic model was used, and in the (H) control group, only the surgical simulation was done. RESULTS: In the control group (H), the acute appendicitis didn't happen. In the experimental group (C, D, E, F and G) the acute appendicitis happened. CONCLUSION: The method used causes acute appendicitis with distinct anatomopathological alterations. The main bacteria found at the physiological flora of the enteric juice from the vermiform appendix and at the exudates peritonitis was the Escherichia coli.

Acute Disease↗
PubMed1993

Modified coronal incision: distribution of stress in the scalp and cranium.

Coronal incision or bitemporal incision is useful for wider visualization in craniofacial surgery. In volume-expanding surgery such as fronto-orbital advancement, however, the incisional scar in the temporal scalp is often undesirably wide and conspicuous. We modified the coronal incision to avoid the widened scar. Further, we analyzed the resulting stress distribution using the finite element method (FEM) to determine whether or not the modification we adapted was effective. The modified method of coronal scalp incision that we used for craniofacial surgery is practical and technically easy. FEM analysis showed that our method was effective in terms of mechanical strength. The simulated surgical craft model is presented and is concluded to be beneficial for further analysis in craniofacial surgery.

Cicatrix↗
PubMed2003

"Real" three-dimensional constructive interference in steady-state imaging to discern microneurosurgical anatomy. Technical note.

Three-dimensional (3D) neuroimages are generally considered useful for neurosurgical practice. Nevertheless, neuroimaging modalities such as 3D digital subtraction angiography and 3D computerized tomography angiography are still insufficient because the resulting images fail to delineate neural structures. Complex neurosurgical procedures are mostly performed in the cerebrospinal fluid (CSF) space of the basal cistern, where vessels and neural structures are present along with the lesion. The magnetic resonance (MR) imaging-derived 3D constructive interference in steady-state (CISS) imaging displays the margin between the CSF and neural structures, vessels, and dura mater in detail, in a two-dimensional fashion. The authors know that volume-rendered 3D CISS images would be more useful for surgery than conventional ones. Although the usefulness of "virtual MR image endoscopy" was reported previously, the endoscopic view is different from the operative field because of the perspective being emphasized. Therefore, to simulate surgical views, the authors made 3D neuroimages from a 3D CISS MR sequence by using an advanced computer workstation. After generating volume images, a cutting method was used in the desired plane to visualize the lesion with reference to a multiplanar reformatted image. The authors call these "real" 3D CISS images, and they are more comparable to the operative field. This newly developed method of producing a real 3D CISS image was used in 30 cases and contributed to the understanding of the relationship between a lesion and surrounding structures before attempting neurosurgical procedures, with minimal invasiveness to the patient.

Basilar Artery↗
PubMed1996

Cranial base tumor visualization through high-performance computing.

Tumors of the skull base in general are considered among the more difficult head and neck pathological entities to treat surgically; some surgeons, in fact, consider lesions in this area inoperable. The most appropriate and safest surgical approach to lesions of the anterior and lateral skull base can be devised only with accurate and precise pre-operative assessment. The literature demonstrates the constant evolution of and search for more efficient less invasive, and safe surgical approaches to this region. With the development of a more exact three-dimensional, interactive anatomical "road map" for each patient's disease and anatomy, the skull base surgeon can not only achieve a more accurate pre-operative assessment leading to a less invasive and less morbid approach, but also can continue to develop and refine new approaches without fear of actual morbidity and mortality. An interdisciplinary team approach, the advent and continued development of faster high performance computers, and the development of new and innovative rendering algorithms can lead to surgical simulation. A prototype of an interactive system has been developed. The system will be iteratively modified through a stepwise evaluation of its clinical usefulness by continually reassessing the system with clinical trials. The current state of the system and the potential benefits are presented.

Brain Mapping↗
PubMed1998

The Virtual Instrumentation (VI) Laboratory facilitates customized on-site ergonomic analysis of minimally invasive surgery.

Ergonomic studies are needed to understand and improve the visual and physical interface that minimally invasive surgery methods interpose between the surgeon and the operating field. We used the Virtual Instrumentation (VI) Laboratory of the Biomedical Engineering Program at California State University, Sacramento to develop a portable ergonomic analysis system to compare the physical workloads imposed on the surgeon by tradition open and laparoscopic surgery techniques. We used the system at a national surgery conference to measure electromyogram (EMG) activity from thumb and forearm muscles of volunteer subjects as they performed simulated surgical tasks using open and laparoscopic techniques. We found that EMG activity was significantly greater for the laparoscopic than for the open surgery technique, suggesting that the laparoscopic technique was more physically demanding. The portable ergonomic analysis VI system was quick to set up and convenient to use. We are using the rapid prototyping and modular design capabilities of the VI Lab to develop additional ergonomic analysis VI systems.

Electromyography↗
PubMed1999

[The scientific bases of virtual endoscopy].

The recent advances in medical imaging, the avaibility of methods for image analysis and computer graphics, the technological resources provided by microdevices and the design of minimal access surgical procedures have open the road to new concepts. Virtual endoscopy represents one of these emerging areas and points out the applicative potential of three dimensional (3D) imaging. It leads to less invasive diagnosis and therapeutic achievements and provides important cues for education and interventional planning. Image segmentation, visualization, tissue modeling and interactions with surgical instruments are the fundamental components to build clinical applications. They are examined in this paper through 3D navigation systems, surgical simulations and image guided interventions.

Computer Simulation↗
PubMed2001

Trauma training: virtual reality applications.

Training medics, medical students, nurses, and residents to perform trauma care skills presents many obstacles. These include: emergent nature of the procedures, instructor time, availability of clinical material, and anatomic knowledge. Virtual Reality simulators address each of these obstacles. The National Capital Area Medical Simulation Center is a unique national asset that not only uses state-of-the-art simulators to teach trauma care skills to medical students and others, but adapts existing technology and develops new simulations to teach these skills. Most standard trauma training is performed on either mannequins or anesthetized animals and requires the constant presence of an instructor. VR applications can be stand-alone devices that have built-in scenarios and multiple patients to increase variation and/or level of technical expertise required to successfully complete the required steps of the trauma procedure. Commercial VR simulators to teach trauma skills include: CathSim Intravenous Simulator (HT Medical), UltraSim Ultrasound Simulator (MedSim), Limb Trauma Simulator (Musculographics/BDI), and the Human Patient Simulator (MedSim). Additionally, we have developed two additional simulators based on the HT CathSim; these are the pericardiocentesis simulator and the diagnostic peritoneal lavage simulator. Future applications include virtual environment triage simulation and surgical airway simulators.

Clinical Competence↗
PubMed2001

Objective laparoscopic skills assessments of surgical residents using Hidden Markov Models based on haptic information and tool/tissue interactions.

UNLABELLED: Laparoscopic surgical skills evaluation of surgery residents is usually a subjective process, carried out in the operating room by senior surgeons. By its nature, this process is performed using fuzzy criteria. The objective of the current study was to develop and assess an objective laparoscopic surgical skill scale using Hidden Markov Models (HMM) based on haptic information, tool/tissue interactions and visual task decomposition. METHODS: Eight subjects (six surgical trainees: first year surgical residents 2 x R1, third year surgical residents 2 x R3 fifth year surgical residents 2 x R5; and two expert laparoscopic surgeons: 2 x ES) performed laparoscopic cholecystectomy following a specific 7 steps protocol on a pig. An instrumented laparoscopic grasper equipped with a three-axis force/torque sensor located at the proximal end with an additional force sensor located on the handle, was used to measure the forces and torques. The hand/tool interface force/torque data was synchronized with a video of the tool operative maneuvers. A synthesis of frame-by-frame video analysis was used to define 14 different types of tool/tissue interactions, each one associated with unique force/torque (F/T) signatures. HMMs were developed for each subject representing the surgical skills by defining the various tool/tissue interactions as states and the associated F/T signatures as observations. The statistical distance between the HMMs representing residents at different levels of their training and the HMMs of expert surgeons were calculated in order to generate a learning curve of selected steps during laparoscopic cholecystectomy. RESULTS: Comparison of HMM's between groups showed significant differences between all skill levels, supporting the objective definition of a learning curve. The major differences between skill levels were: (i) magnitudes of F/T applied (ii) types of tool/tissue interactions used and the transition between them and (iii) time intervals spent in each tool/tissue interaction and the overall completion time. The objective HMM analysis showed that the greatest difference in performance was between R1 and R3 groups and then decreased as the level of expertise increased, suggesting that significant laparoscopic surgical capability develops between the first and the third years of their residency training. The power of the methodology using HMM for objective surgical skill assessment arises from the fact that it compiles enormous amount of data regarding different aspects of surgical skill into a very compact model that can be translated into a single number representing the distance from expert performance. Moreover, the methodology is not limited to in-vivo condition as demonstrated in the current study. It can be extended to other modalities such as measuring performance in surgical simulators and robotic systems.

Animals↗
PubMed1975

The abdominal cutaneous nerve entrapment syndrome.

Entrapment of the abdominal segmental nerves within the rectus abdominis muscle may produce abdominal pain simulating surgical or genito-urinary disease. The diagnosis can be made by localising with one finger an area of tenderness close to the lateral border of the muscle. Pressure at this site will usually reproduce the pain and precise injection of local anaesthetic will abolish the pain immediately. Effective long-term relief is usually obtained by the injection of long acting steroid or a small volume of 7 percent aqueous phenol.

Abdominal Muscles↗
PubMed1992

Retrograde is superior to antegrade continuous warm blood cardioplegia for acute cardiac ischemia.

BACKGROUND: Theoretically, the efficacy of continuous warm blood cardioplegia may be improved when administered retrogradely (RCWBC) rather than antegradely (ACWBC) in the setting of acute regional ischemia because of enhanced oxygen and substrate delivery to myocardial tissue distal to an acute coronary artery occlusion. METHODS AND RESULTS: Eighteen Yorkshire swine were instrumented for quantification of global left ventricular systolic, diastolic, and regional left anterior descending coronary artery (LAD) zone mechanics before and after 10 minutes of mid-LAD occlusion, followed by 60 minutes of cardiac arrest using continuous warm blood cardioplegia. Initially, 20 ml/kg of 37 degrees C oxygenated blood cardioplegia (hematocrit, 22 +/- 0.6%) was infused antegradely, followed by maintenance of 75 ml/min ACWBC (n = 9) or 60-100 ml/min of RCWBC (n = 9). LAD occlusion was released 20 minutes after cardiac arrest (30 minutes total LAD ischemia), simulating surgical revascularization. Postischemic recovery of global preload recruitable stroke work was nearly complete with RCWBC but significantly depressed with ACWBC (84.9 +/- 9.5% versus 52.4 +/- 5.1%, respectively; p < 0.01). LAD regional stroke work was also well preserved postischemically with RCWBC but showed no functional recovery and systolic bulging after ACWBC (87.4 +/- 13.7% versus -11.36 +/- 7.46% of control values; p < 0.01). Global diastolic stiffness calculated using the beta-coefficient of an exponential end-diastolic pressure-versus-volume relation was unchanged with ACWBC but increased significantly after RCWBC (from 0.027 +/- 0.002 to 0.028 +/- 0.003 mm Hg/ml and from 0.028 +/- 0.003 to 0.036 +/- 0.004 mm Hg/ml, respectively). CONCLUSIONS: These data suggest that with acute regional ischemia, both global and ischemic zone regional systolic function are depressed by ACWBC, whereas RCWBC affords adequate protection of contractile performance. However, a loss of diastolic compliance may result as a consequence of warm retrograde delivery.

Animals↗
PubMed2004

[Effect of intraoperative radiation therapy on enzyme histochemistry of expression muscle of guinea pigs after injury of facial nerve].

PURPOSE: To explore the mechanism of facial nerve recovery after radiotherapy by simulating surgical treatment of parotid gland carcinoma with reserving facial nerve and studying the ability of aerobic metabolism, transmission of neurotransmitter, variation of ultrastructure of motor end and mitochondrion after radiotherapy during operation. METHODS: Animal models of treatment group(15Gy) and lethal dose group(17Gy) were established. Succinic dehydrogenase(SDH) and acetylcholine lipase(AchE) of orbicularis oris were measured after radiotherapy. Student's t test was used for statistical analysis. RESULTS: The activity of SDH and AchE declined after radiotherapy. There was significant difference between treatment group and lethal dose group. One month later, there was a significant improvement in the activity of SDH and AchE in treatment group, while that of lethal dose group continued to decline. CONCLUSION: After radiotherapy during parotid gland surgery, the activity of SDH and AchE, transmission of neurotransmitter, and the ability of aerobic metabolism decreased. The ultrastructure of motor end and mitochondrion was destroyed. The variation returned to preoperative levels in treatment group, while did not in lethal dose group.

Acetylcholinesterase↗
PubMed2003

A haptic model of a bone-cutting burr.

We describe a strategy for collecting experimental data and validating a bone-burr haptic contact model developed in a virtual surgical training system for middle ear surgery. The validation strategy is based on the analysis of data acquired during virtual and real burring sessions. Our approach involves intensive testing of the surgical simulator by expert surgeons and trainees as well as experimental data acquisition in a controlled environment.

Computer Simulation↗
PubMed2002

In vivo measurement of solid organ visco-elastic properties.

To support the ongoing development of software-based surgical simulation systems, work is underway to acquire the mechanical properties of living tissue. When such simulations include force feedback, visco-elastic properties must be evaluated over a range of frequencies relevant to human perception and motor control. A minimally invasive instrument has been developed which can perform normal indentation on solid organs, and apply and measure deformations over a frequency range from DC to approximately 100Hz. Measurement performance was validated on a series of objects and materials with known properties, and the device was subsequently used in in vivo tests on porcine liver. Results of these validation tests as well as the data extracted from the in vivo experiments are presented. Testing in ongoing, and will be expanded to more completely characterize liver, as well as porcine spleen and other solid organ tissues. While these animal tissue property tests are valuable in and of themselves, they pave the way for the development of instruments and experimental protocols suitable for the measurement of human tissue properties.

Animals↗
PubMedDate not supplied

Three-dimensional accuracy of implant placement in a computer-assisted navigation system.

PURPOSE: To evaluate the 3-dimensional accuracy of dental implant drilling in a computer-assisted navigation (CAN) system using simulated mandible models. MATERIALS AND METHODS: Eight acrylic resin models were fabricated to simulate human mandibles containing mandibular canal (MC). Computerized tomography (CT) scans were obtained for each model, and the data were transferred to the system for dental implant planning. The models were mounted on a phantom head to simulate surgical situation. The assessment parameters included entry point localization, drill path angulation, and drilling depth, which were directly measured by sectioning of the models. RESULTS: Eighty drill holes were made on the 8 models. The entry point localization showed a mean deviation of 0.43 mm (range, 0 to 2.23 mm; SD, 0.56 mm) from the plan. The angulation showed a mean deviation of 4.0 degrees (range, 0 to 13.6 degrees; SD, 3.5 degrees). The drill aimed at stopping as close to the upper border of the MC as possible without perforating it, and 65% (52) of the drill holes managed to come within 1 mm. Another 5% of the holes stopped 1 to 2 mm above the MC. None of the drill holes stopped more than 2 mm above the MC. However, 30% (24 of 80) of the drill holes perforated the upper border of MC, and the mean depth of perforation was 0.37 mm (range, 0.01 to 1.04 mm; SD, 0.28 mm). DISCUSSION AND CONCLUSION: The CAN system identified the entry location and angulation with mean deviations of 0.43 mm and 4 degrees, respectively. About two thirds of the drillings achieved accuracy within 1 mm above the MC. Thirty percent perforated into the MC, and the maximal depth was 1.04 mm. In the planning stage, the maximal depth of the implant should be at least 1.1 mm above the superior border of MC as a safety margin.

Dental Implantation, Endosseous↗
PubMed1990

[Three-dimensional imaging in plastic surgery. Application to the carpal bones and skull].

Since 1987, the authors have developed three-dimensional (3D) imaging of the carpus. This new application of imaging allows spatial visualization of the complex shapes of the carpal skeleton from all angles and from all illuminations. The development of this technique should lead to a better understanding of the intimate physiology of the carpus, allowing the construction of a model of the wrist enabling precise planning of operative procedures. It also helps to elucidate complex pathological images which are sometimes difficult to interpret on computed tomography scans. In parallel, the same process has been developed for the skull. It is particularly useful in cranio-facial surgery, especially in congenital deformities. Progress in this technique should allow surgical simulation on a video screen in the very near future.

Carpal Bones↗