Search PubMed⌕ Search

Biomedical subjects

J G Thacker

Publications and source records attributed to J G Thacker.

At least 55 records · Page 3Linked to original sources
PubMed1990

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.

Equipment Design↗
PubMed1990

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.

Equipment Design↗
PubMed1989

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.

Alloys↗
PubMed1989

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.

Suture Techniques↗
PubMed1989

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.

Alloys↗
PubMed1989

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.

Humans↗
PubMed1989

Needle holder damage to surgical needles.

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.

Alloys↗
PubMed1989

Tests of two new polyurethane foam wheelchair tires.

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.

Equipment Design↗
PubMed1988

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.

Equipment Design↗
PubMed1988

Principles of emergency wound management.

Every traumatic wound treated in the emergency department is a result of a finite energy source that caused tissue disruption. The dynamics of this exchange of energy will determine the magnitude of injury. Disruption of the body covering leaves the once-sterile underlying integument exposed to contamination. The contaminants are derived from either the victim (endogenous) or the exogenous energy source. The presence of a contaminant such as bacteria makes the care of the wound an exercise in microbiology. Other contaminants, such as dirt, also may reside in the recesses of the wound. Emergency physicians must understand the consequences of tissue trauma. A study of the mechanism of injury will provide a reliable indication of damages. Whether the tissue injury will be limited to the initial wounding depends on the outcome of the interaction between the contaminants and the wound. In the event that the contaminants are very reactive, a relatively insignificant wound may become a catastrophe. This circumstance can be averted by the implementation of a well-devised plan based on the biology of wound healing and infection.

Anti-Bacterial Agents↗
PubMed1988

Automatic wire twister.

This automatic wire twister used in surgery consists of a 6-inch needle holder attached to a twisting mechanism. The major advantage of this device is that it twists wires significantly more rapidly than the conventional manual techniques. Testing has found that the ultimate force required to disrupt the wires twisted by either the automatic wire twister or manual techniques did not differ significantly and was directly related to the number of twists. The automatic wire twister reduces the time needed for wire twisting without altering the security of the twisted wire.

Bone Wires↗
PubMed1988

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.

Humans↗
PubMed1987

Mechanical performance of monofilament synthetic absorbable sutures.

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.

Polydioxanone↗
PubMed1987

Performance of disposable needle syringe systems for local anesthesia.

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.

Anesthesia, Local↗
PubMed1987

Considerations in the choice of sutures for wound closure of the genitourinary tract.

The ideal suture for use within the urinary tract should maintain its tensile strength until wound repair is satisfactory and then it should undergo rapid total absorption without promoting stone formation. The bladder has a great potential for repair, attaining 100 per cent of the strength of the unwounded tissue in 14 to 21 days. Braided synthetic absorbable sutures appear to be suited ideally for closure of incised wounds of a urinary conduit. They maintain their tensile strength for approximately 21 days, during which time the healing tissues regain strength rapidly. Because sutures are foreign bodies and have access to urine, they may serve as a nidus for stone formation. Several factors that have been identified as important determinants of foreign body urolithiasis include the presence of urine, urine volume and pH, infection, physical and chemical configuration of the foreign body, and animal species. The incidence of suture urolithiasis is related directly to the duration in which the sutures are present in the urinary tract. Consequently, absorbable sutures are preferred over nonabsorbable sutures for closure of wounds of the urinary conduit. In the absence of infection braided synthetic absorbable sutures have distinct advantages over gut sutures for closure of urinary tract wounds. They are absorbed by nonenzymatic hydrolysis in a predictable manner with limited inflammatory response. In contrast, gut sutures have an unpredictable absorption rate by enzymatic degradation and elicit an exaggerated inflammatory response. Because infected urine, especially Proteus species, accelerates the degradation of absorbable synthetic sutures to a greater degree than gut sutures, wound closure in the presence of infection should be accomplished with the absorbable natural fiber suture. Nonabsorbable sutures or staples should not be used in the urinary tract because they predictably promote urolithiasis.

Collagen↗
PubMed1987

Unique performance characteristics of Novafil.

Polybutester is a unique copolymer that can be extruded as a flexible monofilament nonabsorbable suture. The mechanical performance of this new suture material was compared with that of polypropylene and nylon. The results indicate that polybutester sutures are as strong, have the same degree of total elongation at break and knot as the other monofilament sutures. In contrast with polypropylene and nylon sutures, the polybutester sutures have a perceptible stretch, are more elastic and flexible, and exhibit less creep. Polybutester sutures appear to be an acceptable alternative to polypropylene and nylon sutures and their unique mechanical properties may even prove to be superior in vivo.

Elasticity↗
PubMed1987

A theory of wheelchair wheelie performance.

The results of this analytical study of wheelchair wheelie performance can be summarized into two wheelchair design equations, or rules of thumb, as developed in the paper. The equation containing the significant parameters involved in popping a wheelie for curb climbing is: fh = 0.8 mg theta c.g. [A] where fh is handrim force, m is the mass of the wheelchair + user less rear wheels, g is acceleration of gravity (9.807 m/s2), and theta c.g. is "c.g. angle," i.e., the angle between the vertical through the rear axle and a line connecting the rear axle and the system center-of-gravity. Equation [A] shows that reducing the mass and/or the c.g. angle will make it easier to pop a wheelie. The c.g. angle is reduced by moving the rear axle position forward on the wheelchair. Wheelie balance is the other aspect of performance considered; where the user balances the wheelchair on the rear wheels for going down curbs or just for fun. The ease with which a system can be controlled (balanced) is related to the static stability of the system. The static stability is defined as: omega 2 = mgl/J [B] where J is the mass moment of inertia at the center of gravity of the system about the direction perpendicular to the sideframe. For better wheelchair control during wheelchair balance the static stability should be reduced. Measurements of the value for the polar mass moment of inertia for a typical wheelchair + user of m = 90 kg was found to be J = 8.7 kg-m2. In order to decrease the value of the static stability, Equation [B], one can increase J or decrease m and/or l, where l is the distance from the rear axle to the c.g. of the system. It is also shown that balancing a rod in the palm of the hand (inverted pendulum) is a mathematical problem similar to the wheelie balance problem, and a rod of length 1.56 meters is similar to a wheelchair + user system mass of 90 kg. However, balancing a rod is done primarily by using visual perception, whereas wheelie balance involves human joint proprioceptors and visual plus vestibular (inner ear) perception. Thus, a simple test of determining the shortest length of rod one can balance in the palm of the hand (plus measuring handrim force capability and simple reaction time) may indicate if a wheelchair user will find it easy to do a wheelie balance.

Humans↗