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PubMed1996

Predictors of ankle and foot fractures in older women. The Study of Osteoporotic Fractures Research Group.

To determine risk factors for ankle and foot fractures, data collected from 9704 women 65 years of age or older from four areas of the United States were analyzed. Self-reported baseline questionnaires covered areas such as lifestyle factors (physical activity, diet, and smoking habits) and functional impairment (history of fracture, falling, and other diseases). Bone mineral density (BMD) and performance on neuromuscular tests were also measured. During 5.9 years of follow-up, 191 women fractured an ankle and 204 women fractured a foot. Proportional hazard models were used to estimate relative risks. In multivariable models, factors associated with ankle fracture included one or more falls in the year prior to baseline (relative risk [RR] 1.5; 95% confidence interval [CI] 1.1-2.1), greater vigorous physical activity (RR per 2 times/week, 1.2; CI 1.1-1.3), weight gain since age 25 (RR per 20% gain, 1.4; CI 1.2-1.5), self-reported osteoarthritis (RR 0.5; CI 0.3-0.8), a sister's history of hip fracture after age 50 (RR 1.7; CI 1.0-3.0), out of house < or = 1 per week (RR 3.0; CI 1.4-6.6), and low distal radius BMD (RR per -0.1 g/cm2, 1.2; CI 1.0-1.4). Factors associated with foot fracture included insulin-dependent diabetes (RR 2.9; CI 1.2-7.2), use of seizure medications (RR 2.3; CI 1.0-5.7) or of benzodiazepines (RR 1.5; CI 1.1-2.2), history of hyperthyroidism (RR 0.5; CI 0.3-1.0), poor far depth perception (RR 0.7; CI 0.5-1.0), and low distal radius BMD (RR per -0.1 g/cm2, 1.3; CI 1.1-1.5). Ankle and foot fractures have different profiles of risk factors that are largely independent of low bone mass.

Aged↗
PubMed1986

Surgical aptitude test for otolaryngology-head and neck surgery resident applicants.

The search for a convenient, rapid manual dexterity examination, which could be used at the time of the otolaryngology resident applicant's interview, led us to assess the following areas: purposeful hand direction, depth perception, tactile discrimination, finger pressure coordination, finger visual tracking of moving objects, spatial visualization, finger strength, speed of movements, fine control precision, finger dexterity, steadiness during movement, steadiness without movement, and neatness. With the astronomical increase in applicants to a limited number of positions in the field of otolaryngology-head and neck surgery, the application of an accurate, efficient manual dexterity assessment at the time of applicant interview is desirable. Presently, dental school applicants are screened by a series of manual dexterity tests. To develop our screening test, we integrated manual performance tests currently in use by private industry, occupational therapists, and dental school admission committees. Thus, applicants who are able to master fine microsurgical and macrosurgical techniques common in our specialty will be preferentially selected.

Aptitude Tests↗
PubMed1994

A new 3-D laparoscope in gastrointestinal surgery.

This study was set up to compare three-dimensional imaging of a new three-dimensional laparoscope with two-dimensional imaging in the inanimate and clinical settings. In the clinical setting the laparoscope was used in a total of 50 different laparoscopic operations. It provided excellent depth perception, definition, and resolution. The relationships of structures were more easily defined, and instrument manipulation was easier, doing away with the need for "touch and feel" to determine instrument position. Three-D imaging made cannulation of the cystic duct for cholangiography or with a flexible choledochoscope easier. In the inanimate setting basic simple tasks took the same time in 2-D as in 3-D, whereas a more complicated procedure of passing a needle and suture through a series of hoops was 25% faster when performed in 3-D compared to 2-D. Three-D imaging may reduce operative time for laparoscopic procedures, particularly the more complicated operations.

Cholangiography↗
PubMed1991

Cognitive spatial-motor processes. 4. Specification of the direction of visually guided isometric forces in two-dimensional space: information transmitted and effects of visual force-feedback.

The information transmitted (Ti) by the direction of two-dimensional (2-D) isometric forces at different stereoscopic depths was studied in 50 naive human subjects using an isometric manipulandum and random dot stereograms generated in a color display (Massey et al. 1988). Subjects viewed the display through appropriate color filters and perceived the image of a disk rotated about a horizontal axis on the frontal plane; the top of the disk was rotated around that axis by 15, 45, 60 and 80 degrees away from the subject. Each of these disks involved a different amount of stereoscopic depth perception which was lowest for the 15 degrees and highest for the 80 degrees tilt. Subjects were instructed to exert force in the direction of a visual target presented on the disk in a reaction time task. The instantaneous force exerted by the subjects on the manipulandum was shown on the disk in the form of a feedback cursor. Information transmitted, reaction time (RT) and systematic directional deviations were calculated. We found the following. (a) Ti increased with input information but at a lower rate; at the highest level of input information studied (5.91 bits), Ti was 4.1 bits at the 15 degrees tilt. This high value of Ti suggests that directional information for isometric force is processed very efficiently. However, this Ti was consistently lower than that transmitted by the direction of movement (Georgopoulos and Massay, 1988). (b) Ti did not differ significantly among the 15-60 degrees tilt but was 0.19 bits less for the 80 degrees tilt. RT did not differ among the 15-80 degrees tilts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1999

[Virtual surgical planning in liver surgery].

UNLABELLED: The operability of a liver tumour depends on its three-dimensional relation to the intrahepatic vascular trees which define autonomously functioning liver (sub-)segments. The aim of our study was to establish a computer-based three-dimensional volumetric operation planning system for the liver. METHODS: Using data from routine helical CT scans the three tissue subclasses of liver parenchyma, liver vessels and liver tumour were segmented semiautomatically. A dedicated segmenting tool was established using region growing algorithms in combination with an "intelligent" border finder. Visualisation is performed by the "Heidelberg Raytracer". The vascular trees are visualised as 3D graphs. Pseudoconnections between portal and hepatic venous trees are separated automatically. Security margins are calculated and the system presents a virtual resection proposal. RESULTS: The 3D anatomy of the liver can be visualised in high quality resulting in good depth perception. Security margins are demonstrated. Dependent liver parenchyma can be recognized automatically on the basis of the vascular trees. The system offers a individualised resection proposal including the tumour, security margin and dependent liver parenchyma. CONCLUSION: Three-dimensional presentation of the individual liver anatomy of a given patient facilitates the perception of the pathology. Virtual reality combined with artificial intelligence allows calculation of complete resection protocols, which can be quantified and modified interactively. This will make operation planning more objective; patient selection may be improved, and in cases of difficult tumour localisation different resection strategies may be tested. Thus virtual reality in liver surgery will improve teaching, surgical training and planning. It may lead to improved surgical care.

Algorithms↗
PubMed2003

Incidence and risk factors for a second hip fracture in elderly women. The Study of Osteoporotic Fractures.

Women with hip fracture have an increased risk of second hip fracture but other risk factors for a second hip fracture have not been established. We sought to determine the incidence and risk factors for second hip fracture, in a prospective cohort study of community-dwelling postmenopausal women over 65 years: the Study of Osteoporotic Fractures. From a cohort of 9,704 women, 632 women with a documented first hip fracture during the study were followed up until a second hip fracture or the end of follow-up. Clinical risk factors and bone mineral density were assessed at the beginning of the study. Fifty-three second hip fractures were validated by radiographs. Women with hip fracture had a 2.3% per year risk of second hip fracture. Women who walked for exercise at baseline were less likely to sustain a second hip fracture with a relative risk (RR) of 0.5 [0.3-0.9], as were those who had normal depth perception (RR=0.5 [0.3-0.9]). Women who lost weight since age 25 years had an increased risk of second incident hip fracture (RR = 2.7 [1.6-4.6]), as did those who had a low calcaneal bone mineral density (RR=1.5 [1.1-2.0] per standard deviation decrease in bone mineral density). Current use of estrogen replacement therapy at baseline was protective (RR=0.5 [0.3-0.9]) up to 2 years of follow-up. We conclude that community-dwelling women with a first hip fracture have a high risk of second hip fracture, and risk factors for this second fracture are similar to those of first hip fracture.

Aged↗
PubMed2006

[Compensation for presbyopia using contact lenses].

Contact lens fitting for presbyotic patients needs more than simple fitting shill; patients need additional psychological support. The wearer has to accept optical quality reduction due to the multifocality of the lens design. In general, the technical fitting of presbyotic contact lenses is comparable to monofocal systems. They work with the same rules of performance. The difference lies in the principles of correction by the lens itself. Simple presbyotic systems use uncorrected optical aberration to widen depth perception. These lenses are suitable for young presbyopes, up to a need of 1 diopter plus power for near vision. Uncorrected aspherical designs have a multifocal effect which can be used for presbyotic lenses. There are contact lenses on the market with simultaneous imaging, which is based on concentric rings around the near or distance centre. Another principles are based on segmented reading portions in the lower part of the lens, also called alternating systems. These very few design variations are the basis for the various specific models which are sold on the market today. The results of the fitting can never be foreseen as subjective and psychological aspects of the wearer overlay the objective results. Thus, the fitter needs experience and patient understanding, combined with fundamental knowledge of the specific lens type used.

Contact Lenses↗
PubMed2003

Stimulus-response compatibility between stimulated eye and response location: implications for attentional accounts of the Simon effect.

One influential theory of the Simon effect, the attention-shift hypothesis, states that attention movements are the origin of spatial stimulus codes. According to this hypothesis, stimulus-response compatibility effects should be absent when attention shifts are prevented. To test this prediction, we used monocular patches of color that required left or right key-press responses. About half of the subjects could discriminate which eye was stimulated (in a subsequent task), and showed strong spatial compatibility effects between the stimulated eye and the response location. The other half of the subjects could not make a utrocular discrimination (i.e., they could not judge which eye had received monocular stimulation), but the pattern of results was the same: the fastest reaction times were observed when the stimulated eye corresponded spatially to the required response (i.e., a Simon effect). Since the subjects presumably did not move their attention (from the subject's point of view, the stimuli were presented centrally), our results indicate that spatial codes can be produced in the absence of attention shifts. These results also show that utrocular discrimination can be assessed via indirect measures that are much more sensitive than explicit measures.

Adult↗
PubMed2004

Computer-enhanced laparoscopic training system (CELTS): bridging the gap.

BACKGROUND: There is a large and growing gap between the need for better surgical training methodologies and the systems currently available for such training. In an effort to bridge this gap and overcome the disadvantages of the training simulators now in use, we developed the Computer-Enhanced Laparoscopic Training System (CELTS). METHODS: CELTS is a computer-based system capable of tracking the motion of laparoscopic instruments and providing feedback about performance in real time. CELTS consists of a mechanical interface, a customizable set of tasks, and an Internet-based software interface. The special cognitive and psychomotor skills a laparoscopic surgeon should master were explicitly defined and transformed into quantitative metrics based on kinematics analysis theory. A single global standardized and task-independent scoring system utilizing a z-score statistic was developed. Validation exercises were performed. RESULTS: The scoring system clearly revealed a gap between experts and trainees, irrespective of the task performed; none of the trainees obtained a score above the threshold that distinguishes the two groups. Moreover, CELTS provided educational feedback by identifying the key factors that contributed to the overall score. Among the defined metrics, depth perception, smoothness of motion, instrument orientation, and the outcome of the task are major indicators of performance and key parameters that distinguish experts from trainees. Time and path length alone, which are the most commonly used metrics in currently available systems, are not considered good indicators of performance. CONCLUSION: CELTS is a novel and standardized skills trainer that combines the advantages of computer simulation with the features of the traditional and popular training boxes. CELTS can easily be used with a wide array of tasks and ensures comparability across different training conditions. This report further shows that a set of appropriate and clinically relevant performance metrics can be defined and a standardized scoring system can be designed.

Clinical Competence↗
PubMed2004

Simulated laparoscopy using a head-mounted display vs traditional video monitor: an assessment of performance and muscle fatigue.

BACKGROUND: The direction of visual gaze may be an important ergonomic factor that affects operative performance. We designed a study to determine whether a head-mounted display (HMD) worn by the surgeon would improve task performance and/or reduce muscle fatigue during a laparoscopic task when compared to the use of a traditional video monitor display (VMD). METHODS: Surgical residents (n = 30) were enrolled in the study. A junior group, consisting of 15 postgraduate year (PGY) = 1 subjects with no previous laparoscopic experience, and a senior group, consisting of 15 PGY 4 and PGY 5 subjects with experience, completed a laparoscopic task that was repeated four times using the Computer Enhanced Laparoscopic Training System (CELTS). Groups alternated between using the HMD with the task placed in a downward frontal position and the VMD with the task at a 30 degrees lateral angle. The CELTS module assessed task completion time, depth perception, path length of instruments, response orientation, motion smoothness; the system then generated an overall score. Electromyography (EMG) was used to record sternocleidomastoid muscle activity. Display preference was surveyed. RESULTS: The senior residents performed better than the junior residents overall on all parameters (p < 0.05) except for motion smoothness, where there was no difference. In both groups, the HMD significantly improved motion smoothness when compared to the VMD (p < 0.05). All other parameters were equal. There was less muscle fatigue when using the VMD (p < 0.05). We found that 66% of the junior residents but only 20% of the senior residents preferred the HMD. CONCLUSIONS: The CELTS module demonstrated evidence of construct validity by differentiating the performances of junior and senior residents. By aligning the surgeon's visual gaze with the instruments, HMD improved smoothness of motion. Experienced residents preferred the traditional monitor display. Although the VMD produced less muscle fatigue, inexperienced residents preferred the HMD, possibly because of improved smoothness of motion.

Computer Simulation↗
PubMed2006

Validation of a new basic virtual reality simulator for training of basic endoscopic skills: the SIMENDO.

BACKGROUND: The aim of this study was to establish content, face, concurrent, and the first step of construct validity of a new simulator, the SIMENDO, in order to determine its usefulness for training basic endoscopic skills. METHODS: The validation started with an explanation of the goals, content, and features of the simulator (content validity). Then, participants from eight different medical centers consisting of experts (> or =100 laparoscopic procedures performed) and surgical trainees (<100) were informed of the goals and received a "hands-on tour" of the virtual reality (VR) trainer. Subsequently, they were asked to answer 28 structured questions about the simulator (face validity). Ratings were scored on a scale from 1 (very bad/useless) to 5 (excellent/very useful). Additional comments could be given as well. Furthermore, two experiments were conducted. In experiment 1, aimed at establishing concurrent validity, the training effect of a single-handed hand-eye coordination task in the simulator was compared with a similar task in a conventional box trainer and with the performance of a control group that received no training. In experiment 2 (first step of construct validity), the total score of task time, collisions, and path length of three consecutive runs in the simulator was compared between experts (>100 endoscopic procedures) and novices (no experience). RESULTS: A total of 75 participants (36 expert surgeons and 39 surgical trainees) filled out the questionnaire. Usefulness of tasks, features, and movement realism were scored between a mean value of 3.3 for depth perception and 4.3 for appreciation of training with the instrument. There were no significant differences between the mean values of the scores given by the experts and surgical trainees. In response to statements, 81% considered this VR trainer generally useful for training endoscopic techniques to residents, and 83% agreed that the simulator was useful to train hand-eye coordination. In experiment 1, the training effect for the single-handed task showed no significant difference between the conventional trainer and the VR simulator (concurrent validity). In experiment 2, experts scored significantly better than novices on all parameters used (construct validity). CONCLUSION: Content, face, and concurrent validity of the SIMENDO is established. The simulator is considered useful for training eye-hand coordination for endoscopic surgery. The evaluated task could discriminate between the skills of experienced surgeons and novices, giving the first indication of construct validity.

Adult↗
PubMed1997

The "knot before loop" technique for the endoscopic ligation and suture-instrument set. Knot formation and application.

BACKGROUND: In minimally invasive surgery intracorporal knot-tying is complicated by a limited field of vision and depth perception. METHODS: The "knot before loop" technique aims to reduce intraabdominal movements in number and space needed. A grasping instrument 3 mm in diameter guides a slipfit hollow knot pusher with a notch to hold the thread, when extracorporally forming the knot on the instrument tip and an axial slot. The loop is finished under endoscopic vision, yet a second loop is created along the thread. The knot is tightened and secured by closing the second loop without troublesome instrument change. RESULTS: The strength of the knot was tested and the feasibility of the instrument set was proven in pigs and 25 cholecystectomies and hernia repairs in humans. CONCLUSIONS: Endoscopic application of a secured slip knot is simplified by the "knot before loop" technique. The independent formation of the knot by the assisting personnel allows quick application, equivalent to the use of clips and staples. The benefit in cost saving is high.

Feasibility Studies↗
PubMed2004

Three-dimensional analysis of dentist's eye movements.

We measured the eye movements of a dentist while a pediatric patient walked toward a dental chair. Bilateral eye movements were measured and analyzed three-dimensionally based on the angle of convergence. The frequency of fixation points registered in each test ranged from 2 to 11, with an average of 6.6. No significant differences were observed when the experiments were grouped according to the age of the observed child. In 13 out of 74 experiments, the calculated distances between the observer and the fixation points corresponded to the actual distances. According to the patterns of where the fixation points occurred, 13 experiments had an "inside-outside" pattern and 61 had an "outside-only" pattern. None of the experiments had an "inside-only" pattern. The "outside-only" group was further subclassified into 50 "behind-only" patterns, 5 "in front-only" patterns, and 6 "in-front-and-behind" patterns. As far as depth perception is concerned, the angle of convergence determined by the eye movements would rarely correspond to the actual distance between the observer and the fixation point.

Accommodation, Ocular↗
PubMed2006

Remote non-invasive stereoscopic imaging of blood vessels: first in-vivo results of a new multispectral contrast enhancement technology.

We describe a contactless optical technique selectively enhancing superficial blood vessels below variously pigmented intact human skin by combining images in different spectral bands. Two CMOS-cameras, with apochromatic lenses and dual-band LED-arrays, simultaneously streamed Left (L) and Right (R) image data to a dual-processor PC. Both cameras captured color images within the visible range (VIS, 400-780 nm) and grey-scale images within the near infrared range (NIR, 910-920 nm) by sequentially switching between LED-array emission bands. Image-size-settings of 1280 x 1024 for VIS & 640 x 512 for NIR produced 12 cycles/s (1 cycle = 1 VIS L&R-pair + 1 NIR L&R-pair). Decreasing image-size-settings (640 x 512 for VIS and 320 x 256 for NIR) increased camera-speed to 25 cycles/s. Contrasts from below the tissue surface were algorithmically distinguished from surface shadows, reflections, etc. Thus blood vessels were selectively enhanced and back-projected into the stereoscopic VIS-color-image using either a 3D-display or conventional shutter glasses. As a first usability reconnaissance we applied this custom-built mobile stereoscopic camera for several clinical settings:* blood withdrawal;* vein inspection in dark skin;* vein detection through iodide;* varicose vein and nevi pigmentosum inspection. Our technique improves blood vessel visualization compared to the naked eye, and supports depth perception.

Blood Vessels↗
PubMed2003

Principles and advantages of robotics in urologic surgery.

Although the available minimally invasive surgical techniques (ie, laparoscopy) have clear advantages, these procedures continue to cause problems for patients. Surgical tools are limited by set axes of movement, restricting the degree of freedom available to the surgeon. In addition, depth perception is lost with the use of two-dimensional viewing systems. As surgeons view a "virtual" target on a television screen, they are hampered by decreased sensory input and a concurrent loss of dexterity. The development of robotic assistance systems in recent years could be the key to overcoming these difficulties. Using robotic systems, surgeons can experience a more natural and ergonomic surgical "feel." Surgical assistance, dexterity and precision enhancement, systems networking, and image-guided therapy are among the benefits offered by surgical robots. In return, the surgeon gains a shorter learning curve, reduced fatigue, and the opportunity to perform complex procedures that would be difficult using conventional laparoscopy. With the development of image-guided technology, robotic systems will become useful tools for surgical training and simulation. Remote surgery is not a routine procedure, but several teams are working on this and experiencing good results. However, economic concerns are the major drawbacks of these systems; before remote surgery becomes routinely feasible, the clinical benefits must be balanced with high investment and running costs.

Humans↗
PubMed2006

Methods for laparoscopic training using animal models.

To reduce the learning curves in humans, several training models have been developed for teaching laparoscopic surgery. The aim of various in vitro or in vivo training models is to help surgeons acquire basic laparoscopic skills such as hand-eye coordination, depth perception, and knot-tying, which should always be acquired prior to organ- or procedure-specific skills. Inexpensive video box trainers are best suited for this purpose. However, advanced laparoscopic skills, such as dissection, cutting, coagulation, and stitching, require more sophisticated animal or human cadaver models. The perfect training model should teach the skills required and should be inexpensive, universally available, and anatomically and physiologically identical to an anesthetized patient. In this paper, we review the different animal models for acquiring advanced laparoscopic skills and try to define their advantages and disadvantages.

Animals↗
PubMed1995

Three-dimensional video imaging for endoscopic surgery.

Recently a number of manufacturers have developed three-dimensional (3-D) video systems which significantly improve visualization and enhance the ability of the surgeon to perform delicate endoscopic dissection and suturing. These 3-D video systems may also improve the education of surgeons-in-training as they would have a better understanding of three-dimensional anatomy during laparoscopic surgery. Most of the 3-dimensional stereoendoscopic video systems currently available have four basic principles of stereoendoscopic image processing in common: image capture, conversion of 60-120 Hz images; presentation of left and right images on a single monitor; and separation of the left and right eye images. Skill tests performed assessing laparoscopic suturing and knot tying have demonstrated a 25% increase in speed and accuracy of these laparoscopic tasks when utilizing a three-dimensional video imaging greatly facilitates the efficiency of endoscopic reconstructive procedures. While three-dimensional video imaging systems are more costly than conventional two-dimensional video equipment, the enhanced depth perception produced by 3-D endoscopes has been demonstrated to improve the performance of minimally invasive surgical procedures.

Endoscopes↗