Biomedical subjects

T G Frank

Publications and source records attributed to T G Frank.

At least 19 recordsLinked to original sources

PubMed2005

Skin wound closure with a novel shape-memory alloy fixator.

BACKGROUND: Previously, we have described novel, thermally deployable tissue fixators based on the shape-memory properties of nickel titanium. The present study reports on the in vivo wound closure with these fixators as a preliminary to evaluating their use for bowel anastomoses. METHODS: Twenty adult Sprague-Dawley rats had 2.0-cm dorsal skin incisions approximated either with shape-memory alloy (SMA) fixators or conventional skin staples on a random basis. Electrical resistance heating was used to transform and deploy the SMA fixators into the wound. The rats were killed on day 14 or day 28 and wound specimens were harvested for force distraction studies and histologic examination. RESULTS: There was no incidence of wound dehiscence. 14- and 28-day wounds from both groups showed no significant difference in breaking force or energy. Histology revealed appropriate stages of wound healing for both SMA-closed and control wounds. CONCLUSIONS: The results confirm the efficacy and safety of tissue-edge approximation with SMA fixators.

Alloys↗

PubMed2005

Development of a shape memory alloy multiple-point injector for chemotherapy.

A medical needle is described that allows injection to take place at multiple sites through a single stab wound. This is achieved by extruding multiple, thin, and curved internal needles from a larger, straight, outer needle. The development and finite element modelling of the shape memory alloy (SMA) inner needles is presented in this paper. A non-linear elastic element model was used in this process to allow for the non-linear properties of the alloy and the large deformations that occur. The model provided maximum strain values and penetration forces for the inner needles. The deformation force on the tip of the needle was measured against displacement to confirm the predicted penetration force. Applications for the device include the treatment of liver cancer by direct injection of alcohol into the tumours.

Alloys↗

PubMed2004

Effect of fixation of shoulder and elbow joint movement on the precision of laparoscopic instrument manipulations.

BACKGROUND: Motion analysis of the upper limb and the surgical instruments is used for objective assessment of endoscopic manipulations. The aim of this study was to investigate the effect of fixation of shoulder and elbow joint movement on the precision of laparoscopic instrument manipulations. METHODS: Two experiments were conducted to correlate hand movement with instrument tip during free and restricted movement of the shoulder and elbow joints. A three-dimensional infrared optical tracking system has been used. Five subjects participated in the study, and each completed the range of movements twice. End points were velocity (m/s), angular velocity (r/s) and acceleration (m/s2). RESULTS: There was a weak correlation for all end points between the instrument tip and individual joint movement during free upper limb movement (r < 0.4). With restricted movement of the shoulder and elbow joints, the correlation between hand movement and instrument tip was found to be good for the velocity (r = 0.66 for flexion; r = 0.72 for abduction; r = 0.56 for supination) and angular velocity (r = -0.83 for flexion; r = -0.48 for abduction; r = -0.70 for supination), but weak for the acceleration (r < 0.4). CONCLUSIONS: The characteristics of hand movements do not correlate with movement of the laparoscopic instrument tip when the upper limb is unsupported. The precision of laparoscopic surgical manipulations is increased if both joints (shoulder and elbow) are supported.

Elbow Joint↗

PubMed2004

Improving the retention of suturing needles in surgical graspers.

BACKGROUND: Surgical needles are usually held using dedicated grasping instruments. When the tissue to be penetrated is resilient, or the grasping force is low, the needle can swivel, causing it to deviate from the intended path, resulting in suboptimal tissue approximation. Needle swivel is particularly prevalent when needles are not held transversely in the jaws, but it is difficult to maintain a transverse grasp during surgery. An improved swivel-resistant grasper design is proposed. METHODS: Conventional and swivel-resistant graspers were tested to quantify the benefits of the swivel-resistant design. Needles secured in the grasper were repeatedly distracted until swiveling occurred. The torque required to swivel the needles was statistically analyzed. RESULTS: The swivel-resistant grasper offers greatly improved resistance to swivel (p = 0.01) when the needle is not held transversely. CONCLUSIONS: The four-point contact afforded by the modified needle graspers imparts improved needle retention and resistance to swivel.

Equipment Design↗

PubMed2004

Characterizing the "gold standard" image for laparoscopic surgery.

BACKGROUND: The term "gold standard" is often used to describe preferred display devices, frequently without substantiating evidence. A meaningful and objective measure of display quality for endoscopic surgery is required. METHODS: Typical colors from five tissue types were arranged in a striped pattern and displayed on four devices: a medical-grade cathode ray tube monitor, a liquid crystal display, a digital light projection display, and an obsolete cathode ray tube (CRT) monitor. The breadth and color contrast of the stripes were adjusted until the patterns became indiscernible to 12 subjects. The data provide a discernibility threshold. RESULTS: The liquid crystal display (LCD) monitor provided the best image. The medical grade and obsolete CRTs were second and third, respectively, and the projection display provided the most inferior image. CONCLUSIONS: A meaningful and relevant measurement of image display quality for laparoscopic surgery based on the discernibility threshold is provided. Of the devices tested, the LCD is the best in terms of image, although the CRT may be preferred at off-axis viewing angles. The projection system, however, offers compensatory ergonomic advantages.

Benchmarking↗

PubMed2003

Real-time thermography during energized vessel sealing and dissection.

BACKGROUND: Energized dissection systems facilitate laparoscopic dissection and hemostasis and reduce instrument traffic. However, they can introduce undesirable thermal collateral/proximity damage to adjacent structures mainly by heat conduction, although other mechanisms may be involved. The latest generation devices have the potential to reduce the incidence of such problems through use of active feedback control over the power output. This effectively regulates the delivery of energy to the target tissue with minimal thermal collateral damage. In addition, innovative heat-sink engineering of the device head ensures that the surface of the instrument tip remains cool (<45 degrees C). In this study, we evaluated the performance of this technology (LigaSure) by using dynamic infrared thermography. The thermal imaging measurements were then correlated with histopathologic studies. The overall value of in situ thermography as an adjunct to energized surgical dissection systems was also assessed. METHODS: Eight anesthetized pigs underwent open surgery to mobilize eight target vessels/organs in a randomized fashion. The LigaSure vessel sealing system with Instant Response Technology was used with three different interchangeable heads. In situ dynamic thermography was undertaken with a thermal imaging camera operating in the mid-infrared (3-5 microm) waveband and with each fully digitized 12-bit thermographic frame acquired at a rate of 60 Hz. Following sacrifice at the end of the dissection, tissue from the dissected regions was harvested for histology by an independent pathologist who was blinded to the thermographic data. RESULTS: Seals made with both the LS1000 5-mm laparoscopic head (predominantly to the small bowel and colon) and the LS1100 10-mm (Atlas) device (on the liver and short gastric tissues) were outwardly satisfactory. The average thermal spread [see text] with the LS1000 was = [see text] 4.4 mm, and the exposed surface of the instrument tip developed a temperature of approximately 100 degrees C. This instrument thus has the potential, albeit small, for heat-related proximity iatrogenic injury. The more technologically advanced LS1100 10-mm laparoscopic instrument exhibited a superior performance, with [see text] = 1.8 mm, and with a maximal temperature on the exposed surface of the jaws well within tolerable limits (approximately 35 degrees C) for use during surgery (laparoscopic or open). This was confirmed by histological studies that demonstrated negligible evidence of thermal damage. CONCLUSIONS: In situ thermal imaging represents a powerful modality for the monitoring of energized dissection/coagulation during surgery. The LigaSure system used with the LS1100 head constitutes a very safe option for energized dissection and hemostasis of vessels with a diameter of up to approximately 7 mm.

Animals↗

PubMed2003

A new multitool for hand-assisted advanced laparoscopic surgery (HALS).

BACKGROUND: Hand-assisted laparoscopic surgery (HALS), which has become possible due to the introduction of effective hand-access devices, facilitates the execution of major operations. Over the past 2 years, we have been evaluating various designs for small instruments that can be used by the internal assisting hand. Here we report on the development, testing, and evaluation of a small reusable multitool that hangs from the little finger of the internal assisting hand of the surgeon when not in use. METHODS: The Dundee Multitool (DMT) was designed to enable the internal deployment (by thumb extrusion) of a small dissecting forceps (pickup), needle driver, and scissors. The multitool hangs from the little finger of the internal assisting hand when not in use. The instrument was subjected to beta testing in the laboratory using HALS trainers. When testing was completed, it was used in major HALS operations after approval by the hospital and consent of the individual patients. RESULTS: The DMT was found to work well. The various active instruments could be extruded from the casing with ease and functioned well in picking up tissues, intracorporeal suturing/tying, and the cutting of sutures and ligatures. Both in laboratory experiments and during clinical evaluation, suturing was easy when the active driving of the needle though the tissues was carried out by the external hand. The multitool needle driver, held by the internal hand as an assisting instrument in conjunction with active needle driving through the tissue edges by the dominant (external) hand, improved suturing efficiency (i.e., reduced execution time) by 30% when compared to total laparoscopic suturing. CONCLUSIONS: We have described a novel little-finger-hung multitool for HALS surgery that deploys with ease at any one time. It incorporates a needle driver, a dissecting forceps, and a suture scissors. The good functionality of the multitool has been confirmed by both laboratory experiments and clinical evaluation.

Animals↗

PubMed2003

Optimization of the projection screen in a display system for minimal access surgery.

BACKGROUND: The operative image for minimal access surgery currently is displayed on a monitor located outside the sterile field. It is ergonomically advantageous to locate the image adjacent to the surgeon's hands by projection onto a sterile screen, but there has been no research into the optimal screen material. METHODS: Several screen materials were compared for image resolution, brightness, variation of brightness with viewing angle, and image artifact. RESULTS: Glossy materials perform poorly, whereas finely grained surfaces improve image clarity. Excessive roughness and incomplete opacity limit the image resolution. Conventional screen fabrics are unsuitable in this application. Ambient lighting and projector brightness affect image contrast, but a correct choice of material can address this. Practical issues such as moisture absorbency and ease of sterilization are considered. CONCLUSIONS: Potential screen materials were rejected because of excessive glare, poor resolution, and image artifact. Finely textured surfaces (e.g., polystyrene sheeting) provide an acceptable screen.

Artifacts↗

PubMed2003

Comparison of conventional and gaze-down imaging in laparoscopic task performance.

BACKGROUND: In video-assisted laparoscopy, the image is usually displayed on a monitor placed at approximately eye level. Video projection systems project the image onto a screen placed close to the hands. This is said to be ergonomically superior. To evaluate this approach, a proprietary projection system (PS) was compared to a monitor display (MD). METHOD: The resolution, ghosting, flickering, glare, contrast, color smear, and color matching of the two modalities were compared. A bowel-suturing task was employed to evaluate performance differences. RESULTS: The image displayed by the first-generation PS is inferior to that of the MD in contrast and resolution measures, but it is comparable in the other image qualities. No significant differences in task performance were identified. CONCLUSIONS: The first-generation PS does not confer performance or comfort advantages over an MD. The theoretical advantages of the gaze-down stance are likely to be realized only if a high-quality projector is used.

Clinical Competence↗

PubMed2001

Influence of handle design on the surgeon's upper limb movements, muscle recruitment, and fatigue during endoscopic suturing.

BACKGROUND: Thus far, little has been done to investigate the kinematics (motion analysis) and kinetics (muscle work, muscle fatigue, comfort) of surgeons during laparoscopic surgery. Therefore, we set out to study these ergonomic aspects of task performance in the dominant upper limb of surgeons during endoscopic suturing. METHODS: Three different handles - conventional finger loop, rocker, and ball handle prototype - were compared in a study involving 10 surgeons suturing porcine enterotomies with each of the three instruments. The endpoints were performance parameters, motion analysis and muscle work, and fatigue of the surgeon's dominant upper limb; subjective scores for comfort level and maneuverability were also elicited from the subjects. RESULTS: Task quality and efficiency during endoscopic suturing, were significantly better with the ball and rocker handle needle drivers than with the finger loop instrument, with lower angular velocity at the elbow and shoulder joints, more pronation, and less supination. The integrated muscle work was much lower for both the rocker and the ball handles. Significant muscle fatigue, especially of the arm flexors and deltoid, was observed only with finger loop instruments. Comfort and maneuverability rating scores were higher with both handles than with the conventional finger loop. The ball handle was easier to maneuver, but it was somewhat less comfortable than the rocker system. CONCLUSION: A different pattern of joint movements, a reduction in muscle power exerted during endoscopic suturing, and hence an absence of muscle fatigue were documented with ergonomic needle drivers (rocker and ball) when compared to the conventional finger loop instruments. These differences translate to better and more efficient task performance with enhanced comfort.

Animals↗

PubMed2001

Measurements and modelling of the compliance of human and porcine organs.

Stress-strain data obtained from animal and human tissue have several applications including medical diagnosis, assisting in surgical instrument design and the production of realistic computer-based simulators for training in minimal access surgery. Such data may also be useful for corroborating mathematical models of tissue response. This paper presents data obtained from ex-vivo and in-vivo tissue indentation tests using a small indentor that is similar to instruments used in minimal access surgery. In addition, uniform stress tests provide basic material property data, via an exponential stress-strain law, to allow a finite element method to be used to predict the response for the non-uniform stresses produced by the small indentor. Data are obtained from harvested pig liver and spleen using a static compliance probe. Data for human liver are obtained from volunteer patients, undergoing minor open surgery, using a sterile hand-held compliance probe. All the results demonstrate highly non-linear stress-strain behaviour. Pig spleen is shown to be much more compliant than pig liver with mean elastic moduli of 0.11 and 4.0 MPa respectively. The right lobe of human liver had a mean elastic modulus of about 0.27 MPa. However, a single case of a diseased liver had a mean modulus of 0.74 MPa--nearly three times the stiffness. It was found that an exponential stress-strain law could accurately fit uniform stress test data and that subsequent finite element modelling for non-uniform stress around a small indentor matched measured force characteristics.

Animals↗

PubMed2001

Perceptual aspects of two-dimensional and stereoscopic display techniques in endoscopic surgery: review and current problems.

The aim of this review is to analyze the perceptual aspects of endoscopic imaging systems. After discussing depth perception in natural settings, the problems of perceiving depth in 2-dimensional representations are investigated. We discuss the impact of stereoscopic video systems on the cerebral perceptual system, emphasising the fact that despite the addition of binocular disparity information, existing stereoscopic video systems are still different from normal 3-dimensional vision. Both 2-dimensional and stereoscopic video systems require a rescaling of visual information to guide motor behavior. A review of the growing number of papers comparing 2-dimensional and stereoscopic video systems shows that only about 50% of investigators found a significant benefit for stereoscopic systems. It is unlikely that image display technology for endoscopic surgery can ever progress to the stage where it is equivalent to normal vision. Within this limitation, progress will result from a multidisciplinary approach, involving technological advances in the quality of the displayed image together with psychovisuomotor and ergonomics research, which facilitates the cerebral rescaling and perception process by the endoscopic surgeon.

Data Display↗

PubMed2000

Puncture forces of solid organ surfaces.

BACKGROUND: In this experimental study, we measured the force needed to puncture the liver (low elastin) and the spleen (high elastin). The surface displacement preceding puncture was also measured. These data are relevant to an understanding of surgical technique and are essential to the development of electronic surgical simulators. METHODS: Controlled puncture experiments were performed on intact organs harvested from pigs and sheep, as well as on their surface capsules following removal and suspension at zero strain and at three increasing levels of prestrain. The biomechanical data were compared with information obtained from histological studies. RESULTS: The spleen has a higher puncture force than the liver and suffers greater displacement before puncture (p < 0.05). Prestrain decreases displacement before puncture (p < 0.05) but has no effect on puncture force. CONCLUSION: The higher puncture force and displacement of spleen, as compared with liver, is probably due to its higher elastin content.

Animals↗

PubMed1999

Rocker handle for endoscopic needle drivers. Technical and ergonomic evaluation by infrared motion analysis system.

BACKGROUND: The design of the handle on instruments for endoscopic surgery determines comfort and efficiency of use by the surgeon. This applies particularly to needle drivers. METHODS: A novel rocker handle was designed to provide holding comfort and intuitive function. This rocker handle was compared with a finger-loop handle in a study involving 10 surgeons who tied a total of 360 intracorporeal surgeons' knots in a random sequence. The end points in this study were the execution time, knot quality, and motion analysis parameters of the surgeon's elbow and shoulder joints. RESULTS: Intracorporeal surgeon's knots tied with the rocker-handle driver exhibited a better knot quality, although this was not significant (p = 0.097). A significant improvement in the knot quality score (KQS) was observed between the first and the second sessions (p = 0.045) with the rocker handle, whereas no significant learning effect was observed for the finger-loop handle. During intracorporeal knot tying, the angular velocity at the elbow and shoulder joints was consistently lower with the rocker handle, suggesting that more controlled movements are enacted by the surgeon with this handle. Discomfort from finger-loop pressure on the thumb was reported by 3 of 10 surgeons with the finger-loop handle, whereas no discomfort was reported for the rocker handle. CONCLUSIONS: The new rocker handle improves the quality of task performance by eliminating discomfort and reducing angular velocities at the shoulder and elbow joints during use.

Endoscopes↗

PubMed1998

The Gupta-Frank clamp for salpingo-oophorectomy at vaginal hysterectomy.

BACKGROUND: When performing a vaginal hysterectomy, removal of the tubes and ovaries can be either necessary or desirable. We describe our experience with a new instrument called the Gupta-Frank clamp for performing vaginal salpingo-oophorectomy at the time of vaginal hysterectomy. INSTRUMENT: The stainless steel Gupta-Frank clamp is 260 mm long, and its shanks are curved to avoid impedance from the vaginal walls. The 70-mm jaws have a smooth curve, which allows both the round and infundibulopelvic ligaments to be incorporated into a single clamp bite. Each jaw has three serrated grooves, which interlock with the corresponding jaw grooves to give a 6-mm-wide atraumatic nonslip area. EXPERIENCE: We have used this instrument in 18 women undergoing bilateral salpingo-oophorectomy at the time of vaginal hysterectomy. A single clamp bite on each side was sufficient to accomplish salpingo-oophorectomy in all cases. There were no major complications. CONCLUSION: Salpingo-oophorectomy performed vaginally at the time of vaginal hysterectomy with the Gupta-Frank clamp is feasible and is accomplished easily and safely.

Equipment Design↗

PubMed1997

Prehensile atraumatic grasper with intuitive ergonomics.

BACKGROUND: Minimal access surgery (MAS) procedures that require tissue to be grasped are impeded by the design of current instruments. The use of graspers and forceps can result in tissue damage and is highly inappropriate when handling larger organs such as the bowel, liver, and spleen. In addition, current instruments have unnatural handling characteristics. A new type of tissue grasper is presented as a solution to these problems. METHODS: The new grasper design was evolved through a process of setting basic requirements and proceeding through cycles of design, construction, evaluation, and re-design. RESULTS: The main features of the new device are prehensile grasping by finger-like jaws, which retain tissue by 'capture,' and a novel handle design with intuitive ergonomics. The jaws are interchangeable to suit differing surgical tasks and the handle and trigger mechanism are designed so that the surgeon's forefinger movement mirrors the instrument jaw action. The grasper has been used in 32 MAS procedures with no indications of trauma. CONCLUSIONS: A grasper that functions by capture has been demonstrated to be an effective solution for atraumatic tissue handling during many MAS procedures.

Endoscopes↗

PubMed1997

Objective assessment of endoscopic knot quality.

BACKGROUND: Studies of the surgeon's skill and the ergonomics of task performance in endoscopic surgery can be based on knot-tying tasks. The aim of this study was to establish an objective method for assessing the quality of surgical knots for use in such studies. METHODS: In all, 2,700 surgeon's endoscopic knots were studied. Each knot was distracted using a tensiometer, and a computerized system analyzed force-extension curves. The breaking force was taken as an index of knot strength while the force integrated over the slope of the curve reflected knot tightening. A knot quality score (KQS) was obtained from the product of the knot-breaking force and the integrated force expressed as a percentage of the product for the untied ligature. RESULTS: The mean breaking force (24 Newton +/- 2.5) and integrated force (7.4 Newton +/- 2.8) for broken knots were 71% and 35%, respectively, of those for untied ligature. The integrated force yielded a narrower range of variability for untied ligature (SD 3.5% of mean) than for knots (SD 37% of mean). The KQS was higher for broken (25.3%+/-10.3%) than slipped knots (7.1%+/-5.1%). CONCLUSION: The KQS provides a reliable assessment of knot security and reflects the strength and degree of tightening of the knot.

Clinical Competence↗

PubMed1997

Technological aspects of minimal access surgery.

Minimal access surgery (MAS) is bringing about a revolution in surgical practice with certain operations being almost wholly carried out using MAS techniques in some countries. This paper describes the development, current status and future prospects of MAS from a technological perspective.

Biomedical Engineering↗