Biomechanical performance of new vascular sutures and needles for use in polytetrafluoroethylene grafts

Two new cardiovascular monofilament sutures attached to taper point needles have been developed for use in expanded polytetrafluoroethylene (PTFE) grafts. One monofilament suture made of PTFE has a microporous structure that allows it to be channel swaged to a needle that closely approximates its suture diameter. The other suture is a monofilament polypropylene suture that has been extruded to produce a tapered swage end, which was significantly smaller than that of the remainder of the suture in order to be channel swaged to smaller diameter needles. On the basis of comprehensive biomechanical performances, the performance of the new needle suture products with needle/suture diameter ratios approaching 1:1 was superior to needle suture products with 2:1 needle/suture diameter ratios for use in PTFE vascular grafts, regardless of the suture material.

Laser-drilled cardiovascular surgical needles

Surgical sutures that are directly attached to the surgical needle ends are called swaged sutures. A forming tool has been used to split one-half of the wire diameter of cardiovascular needles that forms a channel or receptacle for the suture. With the advent of lasers, uniform holes can now be produced in the ends of small-diameter cardiovascular needles. An advantage of the laser-produced hole is that its outer circumference is smooth; the channel swage has a linear slit that interrupts its smooth outer circumference. A standardized reproducible test has been developed that quantitates the force required to pull the needle end through a synthetic membrane that simulates vascular tissue. A swage produced by a laser encountered significantly less drag forces than that noted with a comparable size channel swage of cardiovascular needles.

Influence of surgeon's tying technique on knot security

The purpose of this study was to determine the influence of the surgeon's tying technique on knot security using 0 and 2-0 monofilament and multifilament nylon sutures. Using an Instron Tensile Tester and a portable tensiometer, knot security was achieved with these sutures using four-throw square knots (1 = 1 = 1 = 1). After didactic and psychomotor skill training, medical students were taught to construct the four-throw square knot using either a two-hand tie or an instrument tie. Using the portable tensiometer, their knot tying techniques were judged to be superior to those used by surgeons. The surgeon's faulty technique can easily be corrected by didactic information and psychomotor skill training.

Does a focal neurologic deficit contraindicate operation in a patient with endocarditis?

BACKGROUND

As many as 40% of patients with left-sided bacterial endocarditis will sustain a neurologic insult. The importance of a neurologic change as an indication or a contraindication for valve replacement remains controversial.

METHODS

We performed a retrospective analysis of the records of 33 patients admitted to the University of Virginia Health Sciences Center between January 1, 1978, and June 30, 1996, with a diagnosis of endocarditis and a neurologic change.

RESULTS

All 33 patients had echocardiographic or pathologic evidence of left-sided endocarditis; 23 were seen with focal neurologic findings and had a mortality rate of 22% (5 of 23), and 10 patients were seen with nonfocal, diffuse encephalopathy and had a mortality rate of 60% (6 of 10) (p<0.05). Of the 33 patients, 14 underwent operation and 19 were treated medically. The mortality rate was 21.4% (3 of 14) in the surgical group and 42.1% (8 of 19) in the medical group (p = not significant). In 71% (10 of 14) of the surgical patients, the operation was done within 1 week of the neurologic event. Additional neurologic deterioration occurred in 18.2% (2 of 11) of survivors in the surgical group and 9.1% (1 of 11) in the medical group (p = not significant).

CONCLUSIONS

Choosing therapy for a patient with endocarditis and a neurologic change remains a difficult challenge. Initial findings of nonfocal, global dysfunction on examination are a predictor of a poor outcome. By comparing surgical and medical groups derived from the same series of patients, it is clear that patients with bacterial endocarditis and central nervous system changes face substantial mortality regardless of intervention. However, these data demonstrate that when compared with a similar group of medical patients, surgical patients who require and receive operation early in the course of their illness do comparatively well. Improving outcomes by delaying surgical intervention may serve to "select out" hardier patients but will lead to the death of patients who might benefit from such intervention.

Edlich's academical village

Dr. Richard F. Edlich, Distinguished Professor of Plastic Surgery and Biomedical Engineering, recently received the Thomas Jefferson Award, the highest honor that can be bestowed upon a faculty member at the University of Virginia. Reflections of his "Academical Village" are presented to share ideas from the teaching environment he has created.

New advances in automatic disposable rotating cartridge skin staplers

This report describes the design, operation, and mechanical performance of Auto Suture Multifire Premium disposable skin staplers and staples in a biomechanical laboratory investigation and a clinical evaluation. The performance of this reloadable stapler has been compared with that of a new disposable skin stapler with a rotating cartridge, the Proximate RH stapler. The latter exemplifies a disposable skin stapler whose cartridge cannot be reloaded. The Auto Suture Multifire Premium disposable skin stapler has been designed so that its cartridge can be reloaded during a single surgical procedure. The most obvious advantage of this new device is that it substantially reduces the cost of skin stapling during surgery. Another unique benefit of this stapler is that it can accommodate either regular or wide staples, allowing the surgeon to use both size of staples without discarding the stapler. On the basis of this investigation, the Auto Suture Multifire Premium disposable skin stapler is recommended for skin incision and graft closure, since it provides maximal visualization of the wound as well as the staple during its formation. It delivers the staple into the skin or skin graft so that the topspan of the staple is above the skin or wound surface. In addition, the Auto Suture Multifire Premium disposable skin stapler has a prepositioning (precocking mechanism) that is controlled by the surgeon with minimal force, a mechanism which allows the stapler to hold its staple securely, even when its pointed legs extend beyond the delivery end of the stapler. The force required to form its staples is so low that the surgeon can staple repetitively without fatigue.(ABSTRACT TRUNCATED AT 250 WORDS)

Technical considerations in the selection and performance of walkers

The walker is a mobility aid that provides a portable base of support. People of all ages use different kinds of walkers for a variety of reasons. With the correct walker, many people stroll along at the same pace as their companion. Today, walkers are available in a variety of styles and colors and have numerous accessories. It is the purpose of this article to describe the various types and models of walkers and accessories that are available. Our goal is not to recommend or rate the walkers but to help you find the right walker. The ultimate selection of a walker will depend on a cooperative effort between the physiatrist, physical therapist, and medical equipment supplier. Before you purchase a walker you should test it out to decide if it is the right one for you. The physical therapist who supplies your walker should adjust for your height and should check the physical fit of the equipment. Moreover, the physical therapist should demonstrate the proper gait for walking. During the past few years radical changes have occurred in the design and style of walkers. We expect this trend to continue with more attractive, easier-to-use products to be introduced regularly. If you think that your walker is outdated and is not adapting to your lifestyle, talk with your physiatrist regarding alternatives. Today, walkers are as different as their users. Find the best one for you by taking a test walk in your home and community.

New, innovative packaging system for surgical sutures and needles

A new, innovative packaging system for surgical needles and sutures has been developed that meets the special needs of emergency physicians, surgeons, and operating personnel. This packaging system consists of an overwrap, or breather pouch, as well as an innerwrap containing the needle swaged to a surgical suture. The flaps of the overwrap are offset and serrated to facilitate the opening and sterile transfer of the inner packet to the sterile field. The inner packet contains either a plastic labyrinth or craft board that maintains the suture as straight as possible until knot construction. The needle swaged to a suture is parked in foam to protect its sharp cutting edges and point.

A portable tensiometer for assessing surgeon's knot tying technique

The purpose of this study was to determine the influence of surgeon's tying technique on knot security using O and 2-O monofilament and multifilament nylon sutures. By use of an Instron Tensile Tester and a portable tensiometer, knot security was achieved with these sutures using four-throw square knots (1 = 1 = 1 = 1). After didactic and psychomotor skill training, medical students were taught to construct the four-throw square knot using either a two-hand tie or an instrument tie. By use of the portable tensiometer, their knot tying techniques were judged to be superior to those used by a cohort of obstetricians and gynecologists. The surgeon's faulty technique can easily be corrected by didactic information and psychomotor skill training.

A new compound curved needle for skin and skin-graft closure

A new compound curved needle has been developed for skin and skin-graft closure from a unique stainless steel alloy, American Society for Testing Materials (ASTM) 45500. This needle has a short, straight, sharpened point with a reverse cutting edge and a curved distal section. In spite of its geometry, it exhibits sharpness and resistance to bending and breakage similar to that of a needle with a single radius of curvature that is manufactured from the same alloy. The design of this new needle enables the surgeon to pass it through the skin with greater accuracy to a controlled depth and length of bite.

Biomechanical performance of laser-drilled and channel taper point needles

The purpose of this study is to evaluate the biomechanical performance of laser-drilled and channel needle swages. The laser-drilled swages have a more uniform circumference that encounters lower drag forces than the channel needle swages. In addition, the length of the laser-drilled hole is shorter than that of the channel needles, allowing the physician to grasp the laser-drilled needle close (3 mm) to the needle end without deformation. These benefits of laser-drilled swages indicate that they should replace all channel needles.

A new, compound-curved needle for vascular surgery

A new, compound-curved needle has been designed and developed for vascular surgery from a unique stainless steel alloy, American Society for Testing Materials (ASTM) 45500. This needle has two different radii of curvature and a relatively straight body followed by a short, curved tapered point. Despite its geometry, it exhibits a similar sharpness, as well as resistance to bending and breakage, as did a curved needle with a single radius of curvature manufactured from the same alloy. The design of this new needle enabled the surgeon to pass it through the vessel wall with greater accuracy to a controlled depth and length of bite than the curved cutting edge needle with a single radius of curvature.

Functional urinary outlet obstruction causing urosepsis in a male multiple sclerosis patient

Detrusor-external sphincter dyssynergia (DESD) is a neuropathic disorder of micturition that exists when the simultaneous contractions of the detrusor muscle and external urethral sphincter oppose each other. When the external urethral sphincter contracts during a detrusor contraction, functional urinary outflow obstruction occurs by the increased urethral resistance. This loss of coordination between the bladder and its outlet is associated with a high risk for serious urologic complications, such as vesicoureteral reflux, hydronephrosis, and urosepsis. This report describes a male multiple sclerosis patient with DESD who developed functional outlet obstruction with urosepsis and discusses the diagnosis and treatment of this potentially life-threatening voiding dysfunction.

Influence of emergency physician's tying technique on knot security

The purpose of this study was to determine the influence of emergency physician's tying technique on knot security using 2-0 and 4-0 monofilament and multifilament nylon sutures. Using an Instron Tensile Tester and a portable tensiometer, knot security was achieved with these sutures using four-throw square knots (1 = 1 = 1 = 1). After didactic and psychomotor skill training, medical students were taught to construct the four-throw square knot using either a two-hand tie or an instrument tie. Using the portable tensiometer, their knot tying techniques were judged to be superior to those used by emergency physicians. The emergency physician's faulty technique can easily be corrected by didactic information and psychomotor skill training.

Molten metal burn of the foot: A preventable injury

Molten metal burns of the feet remain a common injury to foundry workers. A case is reported of a foundry worker who sustained circumferential molten metal burns of the distal foot and toes necessitating amputation of four toes. This severe injury could easily have been prevented by the use of protective footwear and spats.

Mechanical performance of disposable surgical needle holders

The mechanical performance of disposable Webster surgical needle holders supplied by three different surgical instrument companies was determined by recording the forces (clamping moment) applied by the different needle holder jaws to curved surgical needles. This investigation demonstrated that there was a large variability in the mechanical performance of the disposable needle holders supplied by each surgical instrument company. In addition, the mechanical performance of the disposable needle holder of each surgical instrument company was distinctly different.

Biomechanics of a new atraumatic surgical needle holder

It is the purpose of this report to design, develop, and evaluate a needle holder whose jaws improve needle-holding security without altering the geometry of the curved surgical needle. The configuration of the jaws of this new needle holder is curved, conforming to the curvature of the surgical needle. A biomechanical study of this curved surgical needle holder demonstrates that it holds the curved needle securely without needle deformation.

Mechanical performance of surgical needle holders

A new quantitative measurement of surgical needle holder performance has been described that records the forces (clamping moment) applied by the needle holder jaws to curved surgical needles. This test has been used to determine the applied clamping forces of four different surgical needle holders made by one manufacturer. By relating the magnitude of the clamping moment of needle holder to the resistance to bending of curved surgical needles, we propose a new scientific basis for selecting surgical needle and needle holders for wound closure.

A new, improved flotation device for deep-water exercise

The purpose of this study was to determine the position and size of flotation devices that permit deep-water exercise with the exerciser's thoracolumbar spine in a vertical position and without restriction of movement of the arms and legs. The buoyant force of the flotation device had to be at least 94.0 N to allow the exerciser to be suspended in water with the head above water. The position of the flotation devices had considerable influence on the thoracolumbar angle. When the large pad with a buoyant force of 55.0 N covered the lower abdominal wall and the small pad with a buoyant force at 39.0 N was located over the lower back, the exerciser's thoracolumbar spine assumed an almost vertical position. Anterior placement of the flotation devices resulted in marked extension of the thoracolumbar spine. Conversely, posterior placement of the buoyant devices resulted in flexion of the thoracolumbar spine. On the basis of these results, an ideal flotation device for deep-water exercise can now be developed.

Biomechanical performance of devices that enhance joint extensibility in the behind-the-back reach test

Several devices (flexible ladder, towel, cord) have been recommended for use in physical therapy to enhance the range of motion of the joints involved in the behind-the-back reach test. The purpose of this study was to evaluate the biomechanical performance of these devices by measuring the maximum forces applied to the devices during the behind-the-back reach test. The performance of all of these devices during the behind-the-back reach test was remarkably similar.

Biomechanical performance of cardiovascular needles

Standardized reproducible tests have been developed to determine the biomechanical performance of cardiovascular needles. The parameters used to assess performance were sharpness, resistance to bending, and ductility. Three comparable groups of taper point cardiovascular needles were selected from different manufacturers for these biomechanical studies. The results of this testing demonstrated that needle geometry, needle composition, and the manufacturer were important determinants of needle performance. When needles of comparable size were evaluated, the biomechanical performance of cardiovascular needles manufactured by Ethicon, Inc., were superior to needles produced by other manufacturers. The superior performance characteristics of the cardiovascular needles produced by Ethicon, Inc., were related to their unique stainless steel alloy, American Society for Testing Materials 45500, which has greater yield and tensile strengths than the alloy used by the other manufacturers. Scanning electron microscopic photographs of the Ethicon, Inc., needle revealed a uniform taper point geometry without irregularities. The deformations of the points of cardiovascular needles produced by the other manufacturers could alter their performance.

Metallurgically bonded needle holder jaws. A technique to enhance needle holding security without sutural damage

A new needle holder jaw face has been specifically designed and developed to increase needle holding security without sutural damage. Tungsten carbide particles have been metallurgically bonded into the stainless steel jaw to create a fine granular surface. This bonded jaw enhances needle holding security by limiting either twisting or rotation of the clamped needle. In addition, compression of the monofilament synthetic sutures by the bonded jaws does not reduce suture breaking strength.

Scientific basis for selecting surgical needles and needle holders for wound closure

Standardized reproducible tests have been devised to determine surgical needle sharpness, resistance to bending, and ductility. Three comparable groups of reverse cutting edge needles were selected from different manufacturers for measurement of these needle performance parameters. This testing demonstrated that needle diameter, manufacturing process, needle material composition, cross-sectional design, and the manufacturer were all important determinants of surgical needle performance. In addition, the biomechanics of curved surgical needle bending has been related to the clamping moment of surgical needle holders. This relationship identifies the surgical needle holder that can be used with surgical needles without deformation. The results of these studies provide a scientific basis for the selection of surgical needles and needle holders for use in surgery.

A beveled, conventional cutting edge surgical needle: a new innovation in wound closure

A new beveled, conventional cutting edge needle has been developed with superior performance characteristics over those of other conventional cutting edge needles. It is composed of a unique stainless steel, ASTM 45500, that has been heat-treated after the curving process to enhance its resistance to bending. The angle of presentation of its cutting edges has been decreased to enhance needle sharpness. On the basis of the results of experimental and clinical investigations, this new needle is recommended for closure of lacerations.

Emergency physician's needle holder

A new needle holder is described that has jaws metallurgically bonded with tungsten carbide particles that enhance needle holding security without causing sutural damage during instrument ties. Scissors have also been incorporated into the needle holder to cut sutures. One ringlet on a handle has been offset to facilitate retrieval of the needle holder from a flat surface.

Biomechanics of curved surgical needle bending

Because needle bending resistance is such an important factor in the selection of surgical needles, a standard quantitative test of needle bending has been devised to study the biomechanics of deformation of needles from three different commercial manufacturers. The superior resistance to deformation of needles made by one manufacturer has been related to the specific alloy, ASTM 45500 stainless steel, employed in its production. The needles produced from ASTM stainless steel 45500 have stronger tensile and yield strengths than those of the other alloys, accounting for their greater resistance to bending.

Surgical needle sharpness

We developed a standard reproducible test to determine surgical needle sharpness. This parameter was measured by recording the maximum force required to push a curved surgical needle through a thin laminated synthetic membrane. Three comparable groups of reversed cutting-edge needles were selected from different manufacturers for needle penetration testing. The results of this testing demonstrated that the needle diameter, manufacturing process, and the manufacturer were all important determinants of needle sharpness. Needles with a smaller diameter were sharper than those with a larger diameter. In addition, electrohoned or hand-honed needles were sharper than those subjected to only machine grinding. When comparably sized needles were compared, Ethicon manufactured the sharpest needles, followed by Davis & Geck and Deknatel needles. Scanning electron microscopic photographs and elemental analysis of the surgical needles could be correlated with their sharpness. The sharper needles had long, narrow cutting edge geometries compared with the short wide geometries of duller needles. The sharpest needles were fabricated from an American Society for Testing and Materials (ASTM) 45500 stainless steel alloy that has stronger tensile and yield strengths than those of ASTM 42000 and 42020 alloys used in the creation of the other needles. This stronger alloy allows the manufacturer to produce a longer, narrower cutting point geometry with reduced danger of either bending or breakage during surgery compared with needles made from weaker alloys (ASTM 42000 and ASTM 42020), which accounts for the superior sharpness of the Ethicon surgical needles.

New atraumatic rounded-edge surgical needle holder jaws

A new atraumatic smooth needle holder jaw with rounded edges that does not damage synthetic monofilament sutures is described herein. These rounded edges were created by mechanical filing of the sharp edges of smooth needle jaws. Compression of the monofilament suture between the needle holder jaw with sharp edges reduces the suture breaking strength compared with that of control sutures. A quality control method has been devised to detect the potentially damaging sharp edges of smooth needle jaws that can be easily implemented by needle holder manufacturers.

A new quantitative measurement for surgical needle ductility

Because surgical needle ductility is such an important factor in the selection of surgical needles, a new curved needle ductility test instrument was devised to measure the ductility of needles from three commercial manufacturers. The superior ductility of needles made by one manufacturer was related to the specific alloy, stainless steel ASTM 45500, used in their production. The ASTM 45500 stainless steel has a significantly greater tensile and yield strength than the other stainless steel alloys, accounting for its superior ductility.

Influence of cutting edge configuration on surgical needle penetration forces

A standardized test for measuring the needle penetration forces has been developed that can be easily replicated in any laboratory. Using this test, conventional cutting edge needles utilized in the test produced lower penetration forces than reverse cutting edge needles. The lower penetration forces encountered by the conventional cutting edge needles imply that the physician should be able to handle these needles with more dexterity and precision than the reverse cutting edge needle.

Splayed handle surgical scissors

Splayed handle surgical scissors have distinct advantages over conventional scissors that limit hand fatigability. The ringlet configuration of the splayed scissors conforms to the normal resting posture of the hand. In addition, surgeons can apply greater force to the splayed scissor ringlets than that which could be applied to the ringlets of conventional scissors.

Surgical needle holder damage to sutures

Needle holder jaws with teeth produce distinct structural changes in synthetic sutures that cause a marked reduction in the suture breaking strength. This damage to the suture may account for disruptions of vascular and fascial wound closures in which continuous closure techniques are employed.

Evaluation of buoyant hydrofitness devices for leg musculoskeletal conditioning

Air splints have been used for immobilization of fractures, skin graft stabilization and preprosthetic rehabilitation of the amputated lower limb. The purpose of this clinical study was to assess its use as a hydrofitness device to facilitate walking reeducation, to produce muscle strengthening and to increase joint extensibility in patients with weak legs. The performance of the air splint as a hydrofitness device was compared to that of the new foam hydrofitness device. The parameters used to assess the performance of these devices included durability, application and removal times, joint extensibility and the magnitude of the fluid drag forces. On the basis of this evaluation, the performance of the foam hydrofitness device was judged to be superior to that of the air splint for leg musculoskeletal conditioning.

Bioengineering principles of hydrotherapy

Hydrotherapy is based on several important bioengineering principles that permit the design and development of aquatic exercise devices, techniques and programs. These principles involve several forces (buoyancy, drag, inertia), hydrostatic pressure and the specific heat of water. By acquiring a knowledge of these bioengineering principles, an individualized exercise program can be prescribed that will enhance physical fitness which is associated with desirable psychological changes.