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PubMed2001

The usefulness of 3D MR angiography in surgery for ruptured cerebral aneurysms.

BACKGROUND: We have used magnetic resonance angiography (MRA) in screening for unruptured cerebral aneurysms since 1993. The development of high-resolution magnetic resonance (MR) imaging has led to a remarkable improvement in image quality. Three-dimensional (3D) MRA can be used for surgical simulation. Here, we report on the usefulness of and problems associated with 3D MRA for the surgery of ruptured cerebral aneurysms. METHODS: Between June 1998 and June 2000, 106 patients with SAH diagnosed by 3D MRA underwent surgery. We compared 3D MRA images with operative findings and investigated the usefulness of this assessment tool. RESULTS: In 48 of 106 cases (45.3%), we were able to perform surgery based on 3D MRA alone. By using the 3D images, we could easily detect the relative location of the aneurysm, its neck and the surrounding arteries. The remaining cases required further examinations because of uncertainty of diagnosis or insufficient information. CONCLUSION: 3D MRA is a safe and useful procedure for the diagnosis and surgery of ruptured cerebral aneurysms. However, in approximately half of all cases, 3D computed tomographic angiography (CTA) or digital subtraction angiography (DSA) is required in addition for the planning of surgery. It is important to use 3D MRA for surgery only after taking sufficient consideration of certain limitations peculiar to MRA.

Adult↗

PubMed2001

Advances in camera, video, and imaging technologies in laparoscopy.

The introduction of technological advances, such as HDTV, three-dimensional laparoscopy, and further miniaturization of high-resolution digital video cameras, will allow significantly enhanced opportunities for laparoscopic surgical proficiency and further broadening of laparoscopic applications in urology. These enhancements, coupled with the recent advances in telemedicine and surgical simulation, will improve laparoscopic training and skill acquisition, decrease operative times and costs, minimize morbidity, and improve overall patient care.

Equipment Design↗

PubMed2003

Computer-assisted distal radius osteotomy.

PURPOSE: To establish the accuracy, precision, and clinical feasibility of a novel technique of computer-assisted distal radius osteotomy for the correction of symptomatic distal radius malunion. METHODS: Six patients underwent a computer-assisted distal radius osteotomy and were followed-up for an average of 25 months. Objective radiographic measurements and functional outcomes, as measured by clinical examination including grip strength and range of motion, and Disability of the Arm, Shoulder and Hand (DASH) questionnaires, were used. RESULTS: The mean radiographic parameters included an increase of radial inclination to 21 degrees from 12 degrees (normal, 23 degrees ). Dorsal and volar tilt (malunion) were corrected to 9 degrees from -30 degrees and 21 degrees, respectively (normal, 10 degrees ). Ulnar variance was corrected to 1.9 mm from 7.5 mm (normal, +1.5 mm). Normal is defined as the average of the contralateral limb radiographs. The mean clinical outcome measures at an average of 25 months included a DASH global score of 14, a DASH individual item average score of 1.6, and an average affected side grip strength of 79% when compared with the unaffected side. CONCLUSIONS: The results of the computer-assisted technique were comparable with published results of traditional non-computer-assisted opening wedge osteotomy techniques. This technique allows a surgeon to accurately and precisely recognize and correct 3-dimensional deformities of the distal radius including axial malalignment (supination). The technique has the added benefit of reducing radiation exposure to the patient and surgical team because fluoroscopy is not used during the procedure. Additional benefits of the computer-assisted technique include the ability to perform multiple surgical simulations to optimize the alignment plan, and it serves as an excellent teaching tool for less-experienced surgeons.

Adult↗

PubMed2002

Endoscopic approach to the pituitary lesions: contemporary method and review of the literature.

The present status of endoscopic transsphenoidal surgery is introduced and reviewed. The difference between endoscopic and microscopic transsphenoidal surgery is explained and also the characteristics of the transnostril approach is mentioned. The advantages of endoscopic surgery are (1) good anatomical orientation with wider view, (2) tumors at the dead angle can be removed under the direct visualization, and (3) the patients can drink, eat and even brush their teeth just after surgery. Short hospital stay and even day-surgery could be possible when a patient is carefully selected. The disadvantages and the limitation of endoscopic surgery have been solved and improved with several new instruments and ideas. Moreover, we have made use of the surgical simulation with the three-dimensional (3-D) CT virtual navigation endoscopic image and the navigation system with the ENT application and the SureTrak of the Stealth Station. There is no need for head fixation with a Mayfield clamp or a C-arm intraoperative fluoroscopic image. This image guidance enabled a correct and smooth approach even in those patients with complicated and abnormal anatomical structures by prior surgery such as for sinusitis. The sellar floor can be safely and correctly opened even in patients with conchal type sphenoid sinus using a navigation system that helps to understand the locations of the cavernous sinus and the internal carotid arteries. The overall result by endoscopic transsphenoidal surgery is as good as or better than that by the traditional microscopic transsphenoidal surgery.

Endoscopy↗

PubMed1993

Clinical application of a solid three-dimensional model for orbital wall fractures.

Orbital wall fractures have been diagnosed conventionally by plain X-rays, CT imaging, and more recently by three-dimensional CT imaging. However, it is not easy to know the three-dimensional appearances of orbital wall fractures. Anatomically precise reconstruction of the orbital wall is essential for the appearance and function of the eyes. Life-size solid models of fractured orbital walls and also solid models of bone grafts for the reconstruction were produced by milling polyurethane foam on the basis of CT data. These models are very valuable because they provide not only satisfactory understanding of the three-dimensional morphology, but the models at hand are the ideal guides during the operation, and the prefabricated bone grafts, based on the models make a complete surgical simulation.

Adolescent↗

PubMed2003

Epicardial radiofrequency applications: in vitro and in vivo studies on human atrial myocardium.

OBJECTIVES: To obtain a better understanding of tissue damage induced in human atria by epicardial radiofrequency ablation and its correlation with intra-tissue temperatures measured sub-epicardially and sub-endocardially. METHODS: Radiofrequency (RF) currents were delivered to human atrial tissues using experimental set-ups to simulate surgical RF epicardial ablation at 80, 85 and 90 degrees C. Sub-endocardial and sub-epicardial temperatures were measured with thermocouples during the ablations. Twelve samples from in vitro epicardial ablations were histologically assessed. Localized RF epicardial ablations at same temperatures were performed on 38 mitral patients with concomitant atrial fibrillation (AF) before full cardiopulmonary bypass and samples histologically assessed. All patients had endocardial RF ablation at 70 degrees C to treat AF. RESULTS: In vitro Sub-endocardial temperatures were lower than 50 degrees C except on thin atria (approximately 2-3 mm) in ablations at 80 and 85 degrees C and on thicker atria (approximately 5 mm) in ablations at 90 degrees C. Lesions measured 0.85-1.98 mm, all showed epicardial and myocardial damage but none were transmural. Mitral patients: Lesions measured 0.38-3.25 mm and 13/25 induced at 70 degrees C, 2/8 at 80 degrees C, 1/4 at 85 degrees C and 0/1 at 90 degrees C were confined to the epicardium leaving the myocardium undamaged. The remaining had damage of the epicardium and of variable portions of the myocardium, and three were transmural. CONCLUSIONS: The application temperature and the intra-tissue temperature are not the sole factors that determine lesion depth. The thickness and the composition of the epicardium and of the myocardium are major determinants in the formation of the lesion.

Adolescent↗

PubMed1998

Aerosol exposure from an ultrasonically activated (Harmonic) device.

STUDY OBJECTIVE: To determine the distribution and concentration of aerosol particles caused by an ultrasonic (Harmonic) scalpel during simulated surgical use. DESIGN: Prospective experimental analysis (Canadian Task Force classification II-1). SETTING: Standard operating room. MATERIALS: Lean pork, lean beef, water, and blood, and the Harmonic scalpel with ball, curved scalpel, and cutting tips. INTERVENTIONS: Real-time sampling of airborne aerosols was performed over 6-second sampling periods. MEASUREMENTS AND MAIN RESULTS: Blood and tissue particles increased significantly during use of the Harmonic scalpel. Local exhaust evacuation methods diminished these concentrations. CONCLUSIONS: The Harmonic scalpel causes formation of bioaerosols that are composed of material of respirable size. When this device is used, a local exhaust system or smoke-evacuation method should be activated to reduce exposure to blood, blood by-products, and potentially infectious materials.

Aerosols↗

PubMed2000

Fast re-rendering of volume and surface graphics by depth, color, and opacity buffering.

A method for quickly re-rendering volume data consisting of several distinct materials and intermixed with moving geometry is presented. The technique works by storing depth, color and opacity information, to a given approximation, which facilitates accelerated rendering of fixed views at moderate storage overhead without re-scanning the entire volume. Storage information in the ray direction (what we have called super-r depth buffering), allows rapid transparency and color changes of materials, position changes of sub-objects, dealing explicitly with regions of overlap, and the intermixing or separately rendered geometry. The rendering quality can be traded-off against the relative storage cost and we present an empirical analysis of output error together with typical figures for its storage complexity. The method has been applied to the visualization of medical image data for surgical planning and guidance, and presented results include typical clinical data. We discuss the implications of our method for haptic (or tactile) rendering systems, such as for surgical simulation, and present preliminary results of rendering polygonal objects in the volume rendered scene.

Algorithms↗

PubMed2002

Evaluation in an anaesthetic simulator of a prototype of a new drug administration system designed to reduce error.

Ten anaesthetists were observed while providing anaesthesia for two simulated surgical procedures, twice using conventional methods and twice using a prototype of a new drug administration system designed to reduce error. Aspects of each method were rated by users on 10-cm visual analogue scales (10 being best) and comments were invited. Median safety scores were 7.7 cm (range 4.3-8.9) for the new system and 4.6 cm (1.3-8.2) for conventional methods (p = 0.009). The new system was compared favourably with conventional methods in respect of safety (p = 0.005), clinical acceptability (p = 0.008), organisation and layout (p = 0.047), and acceptability for use on patients (p = 0.005). The new system saved time in the preparation of drugs both before anaesthesia (105 vs. 346 s; p < 0.001) and during anaesthesia (20 vs. 104 s; p < 0.001). Comments facilitated development of the system and the evaluation endorsed proceeding to a clinical trial.

Anesthesiology↗

PubMed1990

Physiologic effects of acute anemia: implications for a reduced transfusion trigger.

The risks of transfusion-associated infectious disease have led to a reassessment of transfusion practice, which in turn has resulted in a trend toward the reduction of homologous transfusion. This reduction is primarily due to the initiation of hemotherapy at more severe levels of anemia. The optimum threshold for the initiation of transfusion therapy, or the transfusion trigger (TT), is unknown. The purpose of this study is to evaluate the effects of withholding transfusion or lowering the TT to a hematocrit (Hct) of 15 percent in unanesthetized animals. Nineteen adult baboons underwent a laparotomy to simulate surgical stress. Upon their recovery from anesthesia, hemodynamic measurements were obtained, and the animals underwent an exchange transfusion (ET) with 6-percent hetastarch to a final Hct of 15 percent. After ET, hemodynamic measurements were repeated, and the animals were followed for 2 months. There was no morbidity after ET or during the 2-month observation period. After ET, there was a significant increase in both the cardiac output (3.3 vs. 2.5 L/min, p less than 0.001) and the oxygen extraction ratio (59.9 vs. 38.2%, p less than 0.0001). Oxygen delivery fell after ET (18.9 vs. 11.1 cc/kg/min, p less than 0.001), but there was no significant change in oxygen consumption after ET. The unanesthetized animals adapted well to severe anemia and experienced no adverse effects on their long-term survival in this setting, which suggests that the reduction of the TT to a Hct of 15 percent in normal animals is safe. Adoption of this TT could result in a significant reduction in the requirements for homologous transfusion with its attendant risks.

Acute Disease↗

PubMed2003

Comparison of different distal radius dorsal and volar fracture fixation plates: a biomechanical study.

PURPOSE: To compare the biomechanical properties of 6 dorsal and volar fracture fixation plate designs in a cadaver model. METHOD: Six different plating techniques were used on surgically simulated, unstable, extra-articular distal radius fractures in fresh-frozen cadavers. Specimens were tested to failure in axial compression with the Materials Testing System machine, and were analyzed with a motion analysis system. The 6 different fixation systems studied included an AO stainless steel Pi plate (group 1), an AO titanium Pi plate (group 2), a Forte plate (group 3), a dorsally placed Symmetry plate (group 4), a volarly placed Symmetry plate (group 5), and a volarly placed SCS/V plate (group 6). RESULTS: All dorsal plates (groups 1, 2, 3, 4) failed in apex dorsal angulation and all volar plates (groups 5, 6) failed in apex volar angulation. No group developed an average angular deformity greater than 5 degrees with a load of 100 N, which compares with the physiologic loads expected with active wrist motion. Only the volarly placed SCS/V plated specimens (group 6) resisted deformation of 5 degrees or more at loads up to 250 N, which compares with the physiologic loads expected with active finger motion, and was significantly stronger and more rigid than the other 5 plate groups. CONCLUSIONS: The SCS/V plate fixation system is the most rigid of the systems tested and may offer adequate stability for the treatment of the distal radius fracture in which the anterior and/or posterior metaphyseal cortex is comminuted severely.

Adolescent↗

PubMedDate not supplied

Comparison of skin staples with sutures for anastomosis of the small intestine in dogs.

OBJECTIVES: To develop a technique for approximation of end-to-end intestinal anastomoses by using a disposable skin stapler and to compare the stapling technique with an interrupted hand-sewn approximating end-to-end anastomosis of the canine jejunum. STUDY DESIGN: In vitro evaluation of the stapling technique, followed by an in vivo study of healing and clinical response in dogs. ANIMAL POPULATION: 18 mixed-breed adult dogs. METHODS: The anastomotic technique was developed and tested in fresh canine jejunum. Fourteen stapled approximating anastomoses (SAA) and 14 hand-sewn approximating anastomoses (HAA) were performed in 6 cadavers under simulated surgical conditions. Anastomotic construction times, initial bursting strengths, initial lumen diameters, and gross appearance of the 2 techniques were compared. Healing and clinical response were evaluated in 12 purpose-bred dogs assigned to 2 groups of 6 animals each. Each dog had 1 SAA and 1 HAA performed in the jejunum, 50 cm apart. Six dogs were killed on postoperative day 4, and 6 dogs were killed on postoperative day 21. Anastomotic construction time, gross and histological healing, bursting strength, lumen diameter, and circumference were compared between techniques. RESULTS: Mean construction time for SAA was significantly faster than for HAA (P = .0001). None of the anastomoses leaked, and there were no major clinical complications in any dog. Bursting strengths were not significantly different at any time for the 2 techniques. Initial bursting strength was 31% to 35% of the normal jejunum. A nonsignificant decrease in bursting strength was observed by postoperative day 4 (26% to 28% of normal), and a significant increase in bursting strength was observed by postoperative day 21 (100% to 109% of normal). Neither technique decreased the initial lumen diameter. However, both techniques resulted in a similar degree of luminal stenosis as the anastomoses healed. Anastomotic lumen diameter was significantly decreased from normal in both groups at day 4 (86% to 88% of normal) and day 21 (90% to 91% of normal). There was no significant difference between the circumference of the anastomoses and normal jejunum at any time. Histological analysis showed similar healing for the hand-sewn and stapled techniques at 4 and 21 days after surgery. For both surgical techniques, day 21 anastomoses had significantly less inflammation and necrosis, significantly more fibrosis, and significantly better continuity of histological layers when compared with day 4 anastomoses. CONCLUSION: Approximating end-to-end intestinal anastomosis with a skin stapler is equivalent in bursting strength, lumen diameter, lumen circumference, and healing characteristics to the traditional hand-sewn technique, but it can be performed in significantly less time. CLINICAL RELEVANCE: Skin stapling devices can be used to create technically simple, rapid, and safe end-to-end anastomoses in canine jejunum.

Anastomosis, Surgical↗

PubMed1999

Biomodelling of skull base tumours.

Stereolithographic (SL) biomodelling is a new technology that allows three-dimensional computed tomography magnetic resuance data to be used to generate solid plastic replicas of anatomical structures (biomodels). A prospective trial of 11 patients to assess the utility of SL biomodelling in skull base tumour surgery has been performed. Biomodels were manufactured and used for patient education, diagnosis and operative planning. The results suggest that biomodelling has significant utility in skull base tumour surgery and is a cost-effective technology. Biomodels were found to be particularly effective for surgical simulation and the production of customised cranioplastic implants for reconstruction after tumour resection. Copyright 1999 Harcourt Publishers Ltd.

Journal Article↗

PubMed1995

Three-dimensional reconstruction of the biliary tract from two-dimensional biliary images.

To make conventional two-dimensional cholangiography easier and more precise to read, we used techniques in computer vision to reconstruct the images in three dimensions. A 72-year-old man and a 70-year-old woman suffering from acute cholangitis were treated using endoscopic nasobiliary drainage. Their cholangiograms, from two orthogonal views, were used for three-dimensional reconstruction. We used video image-grabber and film scanner methods to digitize the original conventional biliary radiographs, and applied two different image processing methods to show the biliary structure. Both methods of three-dimensional reconstruction of the biliary tract were highly useful in evaluating the biliary tracts in these two patients, especially when a semitranslucence overlapping display technique was applied in the second patient. With this technique, the biliary tree itself and the stones inside the common bile duct can be clearly delineated. The technique of three-dimensional reconstruction of biliary images can make the conventional cholangiographs more lifelike and has great potential in surgical simulation in the near future.

Aged↗

PubMed1994

[Experimental laser surgery of the ossified cochlea].

A pulsed holmium: YAG-laser (lambda = 2120 nm) was used to reopen the basal turn of artificially obliterated human cochleas in freshly dissected cadavers for intracochlear insertion of the stimulation electrode of a cochlear implant under simulated surgical conditions. Laser energy was transmitted through a 400 microns nylon fibre via the opened facial recess directly to the round window niche. At an energy level of 500 mJ/2.5 microseconds pulse, a repetition rate of 2 Hz, and an exposure time of 20-30 s, the photo-ablative mechanism of laser-bone interaction, which has only a limited thermal component, led to recanalisation of the basal turn of the cochlea in a length of 8-10 mm without damaging the surrounding structures. Light microscopic changes in the cochlea were evaluated following laser recanalisation. The artificial bony occlusion and the recanalised basal turn of the cochlea were visualised by means of computed tomography and histological thin section technique.

Cochlea↗

PubMed2002

Reliability of a 3D surface laser scanner for orthodontic applications.

A device for recreating three-dimensional (3D) objects on a computer is the surface laser scanner. By triangulating distances between the reflecting laser beam and the scanned surface, the surface laser scanner can detect not only an object's length and width but also its depth. The scanner's ease of use has opened various possibilities in laboratory research and clinical investigation. We assessed the reliability of generating 3D object reconstructions using the Minolta Vivid700 3D surface laser scanner (Minolta USA, Ramsey, NJ). Accuracy and reproducibility were tested on a geometrical calibrated cylinder, a dental study model, and a plaster facial model. Tests were conducted at varying distances between the object and the scanner. It was found that (1) in the calibrated cylinder tests, spatial distance measurement was accurate to 0.5 mm (+/- 0.1 mm) in the vertical dimension and 0.3 mm (+/- 0.3 mm) in the horizontal dimension; (2) in the study model test, molar width was accurate to 0.2 mm (+/- 0.1 mm, P >.05), and palatal vault depth could be measured to 0.7 mm (+/- 0.2 mm, P > 0.05); and (3) for the facial model, an accuracy of 1.9 +/- 0.8 mm was obtained. The findings suggest that the surface laser scanner has great research potential because of its accuracy and ease of use. Treatment changes, growth, surgical simulations, and many other orthodontic applications can be approached 3-dimensionally with this device.

Cephalometry↗

PubMed2000

Effect of crown lengthening and ferrule placement on static load failure of cemented cast post-cores and crowns.

STATEMENT OF PROBLEM: Restoration of mandibular second premolars with completely missing clinical crowns in the Kennedy Class I and II arches is costly and the risk of failure is high. Should the dentist choose crown-lengthening to allow the addition of a ferrule, despite incurring the disadvantage of an increased crown/root ratio? PURPOSE: This in vitro study determined the combined effect of crown lengthening and placement of a ferrule on the failure resistance to static load of decoronated and restored mandibular second premolar analog teeth. MATERIAL AND METHODS: An extracted mandibular second premolar of average dimensions was selected to form molded composite root analogs and metal crowns. Ten specimens prepared with no-ferrule root and negligible axial wall lengths and 10 specimens with ferrule root, apically repositioned finish lines, were made. Cast gold alloy post and cores and complete crowns were made and cemented. Each root was placed in bone-simulating resin located 3 mm from the finish line. Crown lengthened/ferrule and no-crown lengthened/no-ferrule groups were equally subdivided, whereby 5 crowns were compressively loaded on the buccal cusp tip and 5 were compressively loaded on the mesial marginal ridge. A testing machine applied force until failure occurred. Failure loads were examined with 2-way ANOVA. Significant differences were accepted at P </=.05. RESULTS: Mean failure loads for the crown lengthened/ferrule and no-crown lengthened/no-ferrule groups were as follows: buccal load, 0.61 kN (SD +/- 0.11) and 0.83 kN (SD +/- 0.08); mesial load, 0.70 kN (SD +/- 0.08) and 1.00 kN (SD +/- 0.15), respectively. Crown lengthened/ferrule and no-crown lengthened/no-ferrule groups were significantly different (P <.001). CONCLUSION: The combination of simulated surgical crown-lengthening and more apical crown margin placement to provide a 2-mm crown ferrule on a decoronated mandibular second premolar analog resulted in a reduction of static load failure for the restored analog tooth.

Analysis of Variance↗

PubMed2005

An evaluation of image-guided technologies in the placement of anterior thoracic vertebral body screws in spinal trauma: a cadaver study.

BACKGROUND: Image guidance provides additional anatomic information to the surgeon, which may allow more accurate insertion of spinal implants. Imprecise placement of anterior thoracic screws places the spinal cord and paraspinal structures at risk for injury. Image guidance may afford a safety benefit to patients when anterior thoracic screws are required in the setting of spinal stabilization after trauma. OBJECTIVES: To compare the accuracy of anterior thoracic screw placement using standard fluoroscopy, computer-assisted fluoroscopic image guidance, Iso-C3D image guidance, and electromagnetic fluoroscopic image guidance. STUDY DESIGN: A surgical simulation study in human cadaver spine specimens. METHODS: After an open thoracotomy approach, anterior thoracic screws were placed by experienced spine surgeons using 4 different image-guided techniques in 4 human cadaver thoracic spines. Screws were placed in the 9th, 10th, and 11th thoracic vertebrae of each specimen. The specimens were then examined with thin-cut computed tomography (CT) scans, and with sagittal and coronal reconstructions. Measurements included the distance of the screw from the spinal canal, the angle of the screw path in relation to a perpendicular to a line that bisects the spinous process, and the angle of screw divergence from the superior endplate. RESULTS: There was no evidence of spinal canal penetrance with any of the image-guided techniques used to place anterior thoracic vertebral body screws. Screws inserted with standard fluoroscopy tended to aim anterolaterally by 18 degrees. The image-guidance systems allowed more accurate placement of anterior thoracic screws in the transverse plane compared with standard fluoroscopy. There was no statistically significant difference in coronal plane screw angulation (angle of divergence with the superior endplate) between any of the imaging methods. CONCLUSIONS: Spinal image-guidance systems may allow spine surgeons to place anterior thoracic screws more precisely, particularly in the axial plane. The improved accuracy of spinal implant insertion could ultimately provide a benefit to patient safety, especially in the setting of malaligned vertebral bodies after trauma.

Aged↗