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A latex surgical glove has been designed to have a textured surface that stimulates the surface of intact skin. This textured surface enhances security of grasp of surgical instruments under wet and dry conditions without altering tactile discrimination. The unique hydrogel polymer of this glove allows the glove to be donned with either wet or dry hands without the use of cornstarch lubricants.

It is a commonly held belief among physicians that powder free surgical gloves are more difficult to don than cornstarch powdered gloves. This difficulty is supposedly enhanced when the physician's hands are wet, a situation commonly encountered when regloving during surgical procedures. This investigation dispels these beliefs by demonstrating that the forces required to don powder free gloves do not differ significantly from those required to don gloves coated in cornstarch lubricant. Moreover, Biogel, a new powder free glove with an inner hydrogel lining, is shown to don easily and safely without ripping, even with wet hands, a circumstance not encountered with other gloves.

The history of powered surgical instruments has paralleled their need in surgery, particularly surgery involving hard tissue like bone or teeth. This development was of great importance, as the sophistication of procedures became more demanding, requiring the use of implants. The fields of neurosurgery, orthopaedics, otology, and dentistry have all played key roles in the development of the high-powered surgical instruments that are now used in every surgical and dental subspecialty. Power modalities that include pneumatic and electric sources along with the development of interchangeable accessories have revolutionized the surgical field, making procedures both safer and faster. Many physicians, dentists, and companies continue to contribute to this exciting and rapidly evolving industry.

Wound irrigation is an adjunct to all implant surgeries involving surgical incisions or arthroplasties. An understanding of the physics of wound irrigation provides a scientific basis for recommending wound irrigation systems for implant surgery. When inserting implants through surgical incisions, a low-pressure irrigation system is recommended for removing blood from the wound surface. In contrast, high-pressure irrigation systems are indicated to cleanse the intramedullary canal before cemented arthroplasty. With the advent of static and dynamic pressure transducers, irrigation systems can now be specifically designed to achieve these goals.

The purpose of this study was to measure the biomechanical performance for commercially available microsutures, nylon polypropylene, polyester, and polyglactin 910. The biomechanical performance was determined by reproducible, biomechanical parameters that included stiffness, elasticity, resistance to creep, secure knot construction, and knot breaking strength. On the basis of these comprehensive studies, the handling characteristics of the nylon microsutures were judged to be superior over the other microsutures. Knot security was achieved with a three-throw square (1 = 1 = 1) knot that allowed a preview of the ultimate apposition of the divided tissue. In addition, nylon microsutures were more supple than the other microsutures. The breaking strength of the knotted nylon microsutures was comparable with those of the knotted polyglactin 910 and polyester microsutures, and significantly greater than that of the knotted polypropylene sutures. Its resistance to creep was significantly greater than that of the polypropylene microsutures but less than those of polyglactin 910 and polyester microsutures.

In an effort to reduce the incidence of decubitus ulcers among wheelchair users, current work in cushion design concentrates on minimizing the pressure at the buttock-cushion interface. Finite element analysis can show the stress levels throughout the soft tissue between the cushion and the ischial tuberosity and give designers a better indication of the effects of a particular cushion. Finite element models were generated of the tissues around the ischial tuberosities of male and female subjects. Linear three-dimensional models were generated using a 386 computer and solved with infinitesimal deflection theory. The resulting minimal principal stresses were 17 kPa and 15 kPa at the buttock-cushion interface for seated male and female subjects, respectively. Computational results were verified experimentally with magnetic resonance imaging and interface pressure measurements.

The purpose of this study was to correlate the latex gloves' susceptibility to hydration to its development of glove expansion or irreversible elongation of the latex glove. During hydration, the Micro-Touch glove exhibited significantly more creep strain than did the Biogel gloves. Similarly, the Micro-Touch glove exhibited glove growth, while the Biogel glove maintained a uniform fit during hydration.

A new, innovative packaging system for surgical needles and sutures has been developed that meets the special needs of surgical technologists. This packaging system consists of an overwrap, or breather pouch, as well as an innerwrap containing the suture swaged to a surgical needle. 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.

During the last two decades, major advances in surgical needle and needle holder technology have markedly improved surgical wound repair. These advances include quantitative tests for surgical needle and needle holders performance, high nickel maraging stainless steels, compound curved needles, needle sharpening methods, laser-drilled holes for swages, needle:suture ratios of 1:1, and the atraumatic needle holder.

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.

Needle performance is primarily judged by its penetration through tissue. For detailed studies of needle performance, tissue is too heterogeneous and unstable and difficult to obtain. A homogeneous, stable, and readily available polyurethane substrate has been evaluated as a suitable alternative to biological tissue for evaluation of needle penetration. The needle penetration profiles through the synthetic substrate correlated very well with those through natural tissue. In addition, the synthetic substrate was sensitive enough to easily detect a 20% increase in the force necessary to penetrate natural tissue. This polyurethane substrate offers a valid alternative to biological tissue for the testing of needle penetration performance.

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)

The purpose of this study was to determine the mechanical performance of microsurgical spatula needles for repair of nail bed injuries. Standard biomechanical tests have been devised to evaluate the performance of microsurgical spatula needles. Two comparable groups of microsurgical spatula needles were selected from two different manufacturers for these biomechanical studies. The results of this testing demonstrated that needle point geometry and needle composition were important determinants of needle performance. When needles of comparable size were evaluated, the biomechanical performance of the CS160-8 spatula needle (Ethicon, Inc., Somerville, NJ) was superior to the C-5 spatula needles (Alcon, Inc., Fort Worth, TX). While the development of these biomechanical tests has allowed the evaluation of these microsurgical spatula needles, these same tests can be used to assess the performance of new microsurgical spatula 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.

Two wheelchairs, one manual, one electrically powered, were instrumented with strain gages and operated over various laboratory terrains. Both wheelchairs were folding models with cross tubes pinned together at the center. The wheelchairs were operated on a constant speed treadmill with no bump, and with 0.953 cm (0.375 in) and 1.6 cm (0.625 in) dowels simulating bumps. The wheelchairs were also rolled off a 10.8 cm (4.25 in) platform to simulate a curb drop. The von Mises stresses were computed from the recorded strains, and statistical hypothesis tests were performed to determine whether the stresses were consistent with a stationary, narrow-band Gaussian random process. Such a stress history has been used in random fatigue analyses. Summary data for two strain gage locations on each wheelchair, for the four different test terrains, suggest that the von Mises stress can be considered stationary, but neither narrow-banded, nor Gaussian distributed.

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.

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.

The mechanical performance of ophthalmic surgical needles is studied. Standard biomechanical tests, devised to evaluate the performance of ophthalmic surgical needles, are presented. Four comparable groups of ophthalmic surgical needles were selected from two different manufacturers for these biomechanical studies. The results of this testing demonstrate that needle point geometry and needle composition are important determinants of needle performance. When comparable size needles were evaluated, the biomechanical performance of the recently introduced CS160-6 ophthalmic needle (Ethicon, Inc) was superior to the AU-5, CU-5, and SU-5 needles (Alcon, Inc). Whereas the development of these biomechanical tests has allowed the evaluation of these ophthalmic needles, these same tests can be used to assess the performance of other new ophthalmic surgical needles.

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.

A new compound-curved needle has been designed and developed for microvascular surgery from a unique stainless steel alloy, American Society for Testing Materials 45500. This needle has two distinct radii of curvature and a short tapered point, followed by a curved distal section. Despite its geometry, it exhibits similar resistance to bending and breakage as a curved needle with a single radius of curvature manufactured from the same alloy. The design of this new needle enables plastic surgeons to pass it through vessel walls with greater accuracy to a controlled depth and length of bite than a curved needle with a single radius of curvature.

Standardized reproducible tests have been developed to determine the biomechanical performance of cardiovascular needles. The parameters used to assess performance were: 1) sharpness, 2) resistance to bending, and 3) ductility. Four comparable groups of tapercut and taper point cardiovascular needles were selected from different manufacturers for these biochemical studies. The results of this testing demonstrated that needle geometry, needle composition, and the manufacturer were important determinants of needle performance. When comparable needles were evaluated, the biochemical performance of cardiovascular needles manufactured by Ethicon, Inc. (Somerville, NJ) 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. This stainless steel alloy was ideal for the production of tapercut needles, which combined some of the features of a reverse cutting edge needle and taper point needle. Its very short cutting edges allowed it to penetrate the membrane at considerably lower penetration forces than were encountered with comparable taper point needles. In addition, the investigation indicated that the trocar point cardiovascular needles produced a large triangular defect whose diameter was much larger than that of the needle body. For this reason, the use of the trochar point needle is not recommended in cardiovascular surgery.

The purpose of this investigation was to determine the influence of knot configuration and tying technique on the mechanical performance of surgical sutures. Multifilament and monofilament nylon sutures were selected for this evaluation because they are commonly used in wound closure. The mechanical performance of these sutures was judged by the following parameters: knot breakage force, configuration of secure knots, and knot run down force. During each test, tension was applied at either rapid or slow rates, which correlates with the physician's speed of tying knots. On the basis of these mechanical performance tests, four throw square (1 = 1 = 1 =1) knots and five throw square (1 = 1 = 1 = 1 = 1) knots are recommended for monofilament nylon and multifilament nylon sutures, respectively, in which the speed of application of forces to the knots is relatively slow. Because these tests can easily be replicated in any laboratory, manufacturers now have a scientific basis for recommending specific tying techniques for their surgical sutures.

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 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.

Use of tape and skin staples has many important clinical applications for surgical wounds. During the past two decades, our research program has identified the optimal performance parameters of these wound closure devices. On the basis of their unique performance characteristics, specific staplers and tapes are recommended for wound closure. The scientific basis for selecting staples and tapes for wound closure is based on their influences on the biology of wound repair and infection.

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.

The biomechanical performance of polytetrafluoroethylene (PTFE) sutures has been compared with that of polypropylene sutures, the standard to which other sutures used in vascular and cardiac surgery are compared. The PTFE is supple and has no plastic memory, while the polypropylene suture is stiff and retains its plastic memory. In addition, the rate of creep encountered in the PTFE suture was significantly less than that of the polypropylene suture. The knotting profiles for knot security for either a square, granny, or surgeon's knot for polypropylene sutures were three throws each. In contrast, knot security with either a square or granny PTFE knot was accomplished with seven throws; six throws were needed for a secure surgeon's knot. The breaking strength of the unknotted and knotted PTFE sutures was approximately one half as great as that for the unknotted and knotted polypropylene sutures. Knot construction significantly reduced the breaking strength of polypropylene sutures but did not alter the breaking strength of PTFE sutures. The percent elongation experienced by both sutures before breakage did not differ significantly. The elasticity, as measured by work recovery, for the polypropylene suture was greater than that for the PTFE suture. On the basis of its unique biomechanical performance characteristics, the PTFE suture should have an important place in vascular and cardiac surgery.

A comprehensive analysis of the mechanical performance of sutures has been made to provide information concerning the reliability and security of knotted sutures. The tests utilized in this analysis were designed to be easily reproduced by other investigators. The construction of the knot and the knot performance analysis were undertaken utilizing an Instron Tensile Tester. The mechanical reliability of each knotted suture was determined by measuring the number of throws to reach knot break, the expected slippage of the knot when it reaches knot break, and the maximal holding force at knot break. On the basis of these measurements, recommendations are made for the use of a suture at operation.

The graduate rehabilitation engineering program of study at the University of Virginia is the first program of its type in the United States. The first students were admitted to the program in the fall of 1979. The program is designed to train students with engineering and clinical science backgrounds in the field of rehabilitation engineering. Emphasis is placed on practical training through internship activities at the University of Virginia Rehabilitation Engineering Center and Medical School Department of Orthopedics and Rehabilitation. Field experience is received at the Woodrow Wilson Rehabilitation Center and the University of Virginia Children's Rehabilitation Center.

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.

The performance of different disposable needle syringe systems was determined by measuring needle-puncture pain, needle-bending forces, and the fluid dynamics of the systems. Thirty-gauge needles cause less needle-puncture pain than any other needle. The force required to bend the 30-gauge needle irreversibly was lower than that for the other needles. Studies of the fluid dynamics of different needle syringe assemblies demonstrated that the flow rate can be limited by using large-size syringes (30 mL) and needles with the smallest internal diameter. On the basis of the results of this study, 30-gauge needles attached to 10-mL syringes are recommended for infiltration anesthesia, and 25-gauge needles with 10-mL syringes are advocated for regional nerve blocks. In infiltration anesthesia, the local anesthetic agent should be injected slowly into the subdermal tissue over a 10-second period. When performing regional nerve blocks, it is also advisable to inject the local anesthetic agent over a 10-second time interval.

A new, improved drainage system has been specifically designed to provide either closed suction drainage for the ambulating patient or sump drainage for the patient confined to bed. This drainage system is made of silicone that has a hydrogel coating with a low coefficient of friction. This coating facilitates removal of the drain from the wound cavity and reduces the adherence of blood clots in the drainage system. A filter assembly is attached to the air vent lumen to remove particulate matter and bacteria from the air. Clinical evaluation of the filtered sump drainage system has confirmed its superiority over closed suction in its efficiency of removing fluids from the wound.

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.

The performance characteristics of four 24-inch wheelchair tires are considered; one pneumatic and three airless. Specifically, two new airless polyurethane foam tires (circular and tapered cross-section) were compared to both a molded polyisoprene tire and a rubber pneumatic tire. Rolling resistance, coefficient of static friction, spring rate, tire roll-off, impact absorption, wear resistance, and resistance to compression set were the characteristics considered for the basis of comparison. Although the pneumatic tire is preferred by many wheelchair users, the two new polyurethane foam tires were found to offer a performance similar to the high-pressure pneumatic tire. In addition, the foam tires are less expensive and lighter in weight than the other tires tested.

The purpose of this study was to evaluate the mechanical performance of two new synthetic monofilament absorbable sutures. The polydioxanone sutures is prepared by polymerizing and extruding the monomer, paradioxanone, in the presence of a suitable catalyst. The other suture is a modified polyglycolic acid suture, made by reacting trimethylene carbonate and glycolide. The knot configuration (1 = 1 = 1, 1 x 1 x 1, and 2 = 1 = 1) required for knot security was identical for the two synthetic monofilament sutures. The mean knot breaking strengths for the polydioxanone and modified polyglycolic acid sutures did not differ significantly. The surfaces of these sutures exhibited a low coefficient of friction which was slightly increased by hydration. The most distinctive difference between the handling characteristics of these two sutures was their flexural rigidity. The stiffness of the polydioxanone suture was 60 percent greater than that of the modified polyglycolic acid suture.

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 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.

The purpose of this study was to evaluate the knotting and handling characteristics of the new coated synthetic absorbable sutures. When compared to the coated polyglactin 910 sutures, the coated polyglycolic acid sutures displayed a lower coefficient of friction, encountered less tissue drag forces, and exhibited less flexural rigidity. In the case of sizes O, 2-O, and 3-O coated polyglycolic sutures, knot security was achieved with one less throw than with similar sizes of coated polyglactin 910 sutures. On the basis of these comprehensive mechanical performance tests, the knotting and handling characteristics of the coated polyglycolic acid sutures were judged to be superior to that of the coated polyglactin 910 sutures.

The biomechanical properties of skin have an important influence on plastic surgical decisions. They aid the surgeon in planning elective incisions, excisions, or scar revisions. They provide insight into the most appropriate method of coverage of skin defects as well as the design of an artificial skin substitute. Skin biomechanics can, in part, be characterized in vivo by either a skin extensiometer or by studying the deformation of skin defects. These methods indicate the magnitude and directional orientation of skin tensions which are dependent partly on the mechanical characteristics of the dermal fibers and partly on the pattern in which they are woven. The tensions to which the skin are subjected can be classified as either static or dynamic in origin. Static skin tensions are the natural tensions existing in skin. The magnitude of static tensions varies between individuals, at different sites in the same person, and in different directions in many sites. The dynamic tensions are caused by a combination of forces which are associated with joint movement, mimetic and other voluntary muscle activity, and gravity. Knowledge of these tensions allows the surgeon to align the operative site in the direction of maximal tension and to approximate the wound with the least amount of tension. As a consequence of this, the scar healing between the cut edges of the wound should be narrow and inconspicuous.

The strain in thin flexible membranes representing human skin has been studied using moiré interferometry. A method of using a flexible coating of photographic emulsion was developed. The equations for use in differential interferometry were also derived for very large deformations. The method was applied to two types of cases: rectangular membranes subjected to a uniform axial strain, and membranes containing strain concentrators that represent bandages placed on the surface of the skin. Results for the former case were within 3% of exact results, while results near the concentrator indicate strain concentration factors ranging from -1.25 to 1.75.

The mechanical performance of polyglycolic acid and polyglactin 910 sutures has been assessed using standardized reproducible tests. The results of these studies demonstrated distinct differences in their performance that can be related, in part, to their structural configuration. The size of the 4-0 polyglactin suture was significantly larger than that of the 4-0 polyglycolic acid suture. Since the strength of any suture is proportional to its cross sectional area, the strength of unknotted and knotted polyglactin 910 sutures was signficantly greater than that of the polyglycolic acid sutures. The strength of both sutures was similarly diminished by the formation of the knot. When these sutures were added to tissue, the breaking strength was even further reduced. The rate of decline in breaking strength of the two absorbable sutures in healing skin wounds was comparable. These absorbable sutures displayed knot security with a two throw square knot, 1 = 1. The ability of these sutures to reach knot break with this knot configuration is characteristic of sutures in which the surface exhibits a high coefficient of friction. Their rough surface also caused them to drag through tissue, making difficult to adjust tension on a continuous running suture.

The equations for wheelchair caster wheel shimmy are presented along with experimental data. The report includes the theory and performance of single wheel casters for a variety of tires, and a new design for wheelchair casters using a grooved dual-tread tire or co-rotating caster wheels. The dual-tread tire was found to significantly inhibit caster shimmy. The turning resistance due to a grooved caster wheel tire with a 1/2-inch groove was found to be 10 percent greater than for an ungrooved caster wheel tire. The analysis includes the methodology and the results of experiments developed to measure the sliding friction turning moment of the wheelchair caster wheel. A number of commercial wheelchair caster wheels were tested and the results for shimmy are presented.

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.

Clamping surgical needles between the jaws of needle holders with teeth markedly weaken the needles, making them prone to breakage. In contrast, clamping surgical needles between either smooth needle holder jaws or jaws embedded with tungsten carbide particles did not alter the ductility of surgical needles.

The design and material properties of a surgical wire have been enhanced to improve its performance in surgery. One blunt end of the wire has been honed to a point to decrease the axial compressive force required to penetrate tissue. In addition, its sharp end has been work hardened to increase its yield strength. The mechanical performance of this wire has been characterized by a series of in vitro experiments and a clinical trial.