- Email: [email protected]
Past, present, and future for surgical needles and needle holders
Past, Present, and Future for Surgical Needles and Needle Holders Richard F. Edlich, MD, PhD, John G. Thacker, PhD, Walter McGregor, MBA, George T. Rodeheaver, PhD, Charlottesville, Virginia
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 needie 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 atraumatie needle holder.
1972, Van Winkle and Hastings [1] published a colItheynlective review of surgical suture materials in which proposed a sound scientific basis for the selection of sutures based upon the results of scientific studies that documented the effects of surgical sutures on the healing wound. Three years later, Trier [2] wrote his collective review to provide a rational criteria for needle and needle holder selection. There were notable differences in the tasks and approaches to these two collective reviews. First, Van Winkle and Hastings [1] confined their review to the 6 different suture materials commonly used in clinical operations, whereas Trier [2] provided an overview of 100 needle choices i n 9 different shapes and a variety of needle holders bearing the name of the inventive surgeons. Van Winkle and Hastings [1] had the benefit of large numbers of well-designed experimental and clinical investigations that provided a scientific basis for the selection of surgical sutures. In contrast, Trier's [2] review was based exclusively on testimonials of talented surgeons, the manufacturers' catalogs, and his extensive clinical experience as a skilled plastic surgeon. In the absence of well-designed scientific studies, Trier's [2] report served as an excellent overview and classification of surgical needle and needle holder products, which has provided considerable direction for our comprehensive scientific studies during the last two decades. Our studies have focused on seven major advances in surgical needle and needle holder technology that have markedly improved surgical wound repair. These advances include quantitative tests for surgical needle and needle holder performance, high nickel maraging stainless steels, compound curved needles, needle-sharpening methods, laserdrilled holes for swages, needle:suture ratios of 1:1, and the atraumatic needle holder. These recent advances in surgical needle and needle holder technology provide a scientific basis for selecting surgical needle and needle holders as well as insight into future technologic advances that are on the horizon.
PRESENT Quantitative tests for surgical needle and needle holder performance: The biomechanical performance of the surgical needles and needle holders was determined by the following parameters: (1) needle sharpness, (2) needle resistance to bending, (3) needle ductility, and (4) Fromthe Departmentof PlasticSurgery(RFE,WM, GTR),University of VirginiaSchoolof Medicine,and the Departmentof Mechanical needle holder clamping moment. The sharpness of the and AerospaceEngineering(JGT), Universityof Virginia,Charlottes- surgical needle was determined by measuring the maxiviUe,Virginia. mum vertical force required for it to penetrate a thin Supported by a grant fromthe TexacoFoundation,WhitePlains, laminated synthetic membrane (Medpar 1220, 3M CenNew York. Requests for reprints should be addressedto Richard F. Edlieh, ter, St. Paul, MN) [3]. This test was accomplished with MD, PhD, Departmentof Plastic Surgery,Box 332, Charlottesville, an Instron Model CR5368 Curved Needle Testing Fixture in conjunction with an Instron 1122 Universal TestVirginia22908. 522
THE AMERICAN JOURNAL OF SURGERY VOLUME 166 NOVEMBER 1993
SURGICAL NEEDLES AND NEEDLE HOLDERS
ing Machine (Instron Corp., Canton, MA). The testing apparatus rigidly held the curved needle in a set of jaws that rotated through an arc equal to the curvature of the needle. The needle was made to penetrate the supported membrane, and the forces necessary to cause passage through the membrane were recorded as a force versus angle position curve. When the point of the needle passed through the membrane, there was a detectable decrease in the magnitude of the penetration force (initial needle penetration force/g), after which the penetration force rose to a maximum peak (maximum penetration force/g) as the needle's tapered geometry passed through the membrane. With the advent of the electronic load cell transducer, the bending resistance of the curved surgical needle generated a force-angular deflection curve that allowed quantitation of the resistance to needle bending [4]. In these tests, the bending forces were sensed by the strain gauge load cell transducer and recorded on a strip chart recorder. The bending force needed to deform the curved needle was recorded as a function of the angular deformation of the needle. The vertical axis on the strip chart recorder was calibrated to record force, whereas the horizontal axis was linearly related to the angular rotation of the needle. Because the moment arm remained constant, the bending moment was proportional to the bending force. During each test, bending of the needle resulted in an angular deformation versus bending moment curve that was analyzed to give a yield moment and an ultimate bending moment. Typically, the curve exhibited an initial linearly elastic deformation region, followed by a nonlinear plastic deformation region. Because there was no clear distinction for some needles between the elastic and plastic regions of this bending curve, it was difficult to identify the applied moment at which permanent deformation occurred. To identify a reproducible yield moment for this test, a 2* offset yield technique was used that followed the same principle as the classic 0.2% offset strain method commonly used in tensile testing [4]. This 2 ~ value was chosen because it represented a distinct point of demarcation from the linear line. The yield moment was identified at the intersection of this offset line with a test curve. Bending tests on curved needles whose applied bending moments were less than the yield moments resuited in needle elastic deformations that were completely recoverable, whereas applied bending moments greater than the yield moments caused needle plastic or irreversible deformation. The ultimate moment was defined as the greatest bending moment on the curve, with the maximum angle of bend for the curved needle being 90 ~ due to limitation imposed by the test apparatus. Ductility or resistance to surgical needle breakage was measured by the curved surgical needle bend tester, which determined the work required to completely fracture a surgical needle [5]. For this ductility test, the stepping motor of the curved needle bend tester was calibrated to rotate the curved needle at a constant angular speed. During a typical ductility test, bend forces were recorded as each test needle was cyclically bent through
arcs of 90 ~. To obtain the work required for needle breakage, the area under the moment-deflection curve was calculated using a computer software package. The total amount of work required to bend the needle back and forth through a 90* arc until fracture was the measurement of needle ductility. Needle holder clamping moment is an important measure of needle holder performance. The needle holder consists of two first-class levers that rotate on a common fulcrum. The portions of the levers that grasp the needle are distal to the fulcrum and are called the jaws. The remaining portion of the lever, that portion that is held by the surgeon, is called the handle. When a circular needle is clamped between the jaws of the needle holder, the needle contacts the jaws at three different sites. At midpoint in one jaw, a clamping force (F j) is applied to one site on the convex surface of the needle. Each edge of the opposing jaw surface applies separate and equal forces to the concave surface of the needle. The magnitude of these forces is exactly half the total clamping force (Fj/2). Because Fj acts at the point of the maximum bending moment, its moment is 0 and therefore does not contribute to the calculated bending moment. In contrast, the applied force at the edge of the needle holder jaw has a moment arm equivalent to one-half the jaw width (W/2). Consequently, the maximum needle holder clamping moment (Me) exerted on the needle is a product of the clamping force at one edge of the needle (F j/2) times the length of its moment arm (W/2) from the line of action of this force to the center of the clamped needle. Mc = Fj/2 x W/2 = FjW/4 The force resulting from the closure of the jaws (Fj) is directly proportional to the length of the handles and inversely related to the length of the jaws, and can be calculated by the following lever equation (Figure 1): F j = FFLL/LJ where: F j --- force applied by the jaws of the needle holder FF = force applied by fingers to ringlets of the needle holder LL = length of the handle from the fulcrum to the site at which force is applied to ringlets Lj = Length of the jaw from fulcrum to point at which jaw holds the needle
These equations have been validated by relating the clamping moments of the needle holder jaw to the yield bending moments of surgical needles [6]. High nickel maraging stainless steel: Iron is never found alone in nature, hut exists in the form of oxides, carbonates, and sulphides. Steel is a more refined grade of iron with a reduced carbon content. Every alloying element has a particular effect on steel. Technically, carbon should not be considered an alloying clement because without it steel would not exist, but would remain iron.
THE AMERICAN JOURNALOF SURGERY VOLUME 166 NOVEMBER1993 523
EDLICH ET AL
L._
LL
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,
2
MECHANICAL
L, Lj Figure 1. Needle holder.
Figure 2. The compound curved needle had two distinct radii of curvature, whereas the standard curved needle only had one radius of curvature.
Varying amounts of carbon in steel have a profound effect on its properties. When a combination of two or more elements exists in the steel, the total result is an increase in each of the characteristics that is greater than the sum of the individual effects. Stainless steels have excellent resistance to corrosion. All true stainless steels contain a minimum of about 12% chromium, which allows a thin protective surface layer of chromium oxide to form when the steel is exposed to oxygen. Since their development during the early sixties, high nickel maraging stainless steels have found extensive use in structural materials in many applications requiring a combination of high strength and toughness [7]. The basic principle of maraging consists of strengthening FeNi martensitic matrices by the precipitation of fine intermetallic phases such as Ni3 Ti. These precipitates are so small that they are only evident on transmission electron microscopy. They strengthen the metal by preventing the planes of atoms in the stainless steel from sliding over each other. A high nickel maraging stainless steel, like $45500, is composed of 7.5% to 9.5% nickel, 0.8% to 1.4% titanium, and 11% to 12.5% chromium. In contrast, $42000 stainless steel is composed of 12% to 14% chromium without nickel or titanium. Scientists have successfully utilized the concept of high nickel maraging stainless steels ($45500) to develop stainless steel wires with superior strength and ductility for use as surgical needles
[4,5]. Surgical needles made of high nickel maraging stain524
THE AMERICAN JOURNAL OF SURGERY
less steel, like $45500, have a greater resistance to bending and breakage than stainless steels without nickel, like $42000. The mean yield moment (5.7 4- 0.3 N-cm) and mean ultimate moment (8.1 4- 0.8 N-cm) of curved surgical needles (diameter 0.58 mm, length 19 mm, curvature 135 ~ made of $45500 stainless steel were significantly greater than the mean yield moment (3.6 4- 0.3 N-cm) and mean ultimate moment (5.9 4- 0.5 N-cm) of comparable size needles made of $42000 stainless steel (p <0.05). Similarly, the work to fracture (19.6 4- 2.9 N-cm) these $45500 surgical needles was significantly greater than the work to fracture (12.9 4- 1.1 N-cm) comparable size surgical needle made of $42000 stainless steel (p <0.05). Compound curved needle: Needles used for closure of thin planar structures (e.g., skin, vessels, etc.) have usually been semicircular needles with a single radius of curvature measuring 135 ~. Although needle sharpness and resistance to bending and breakage are important considerations, they will not provide optimal needle control necessary for accurate approximation of these structures without concomitant attention to needle shape. Needle shape or curvature has, until now, been the most neglected design parameter in the quest to improve needle performance. With the advent of high nickel maraging stainless steel alloys, the shape of the needle can be easily changed without altering its resistance to bending. By using this alloy, a new compound curved needle has been specifically designed and developed for closure of thin planar structures (Figure 2). This needle has a short, straight point, followed by a curved distal section. This needle exhibited a greater resistance to bending than a comparable size curve needle with a single radius of curvature. The mean yield moment (7.2 4- 0.2 N-cm) and the mean ultimate moment (9.5 4- 0.4 N-cm) of the compound curved needies were significantly greater than the mean yield moment (6.0 4- 0.3 N-cm) and the mean ultimate moment (8.1 4- 0.4 N-cm) of surgical needles with a single radius of curvature with the same diameter and high nickel maraging stainless steel alloy (p <0.05). The shape of the compound curved needle has several advantages over the needle with one radius of curvature
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SURGICAL NEEDLES AND NEEDLE HOLDERS
for closure of these tissues. Its relatively straight point facilitates the initial entrance through the tissue as well as controls the depth of penetration. Its tight needle curvature beyond the tip permits rapid, accurate needle passage at a selected depth and controlled exiting. Its design also provides a mechanical advantage over the standard needle that enhances its resistance to bending (Figure 3). The bending moment (M) that can be applied to the needle body is directly related to the needle's susceptibility to irreversible bending. The applied bending moment is determined by multiplying the tissue forces (F) that resist needle penetration by the needle moment arm (D), which is the perpendicular distance between the line of action of the tissue forces and the centroid needle's cross-section that emerges between the needle holder jaws. Because the moment arm (D2) of the compound curved needle is significantly less than that of the standard needle with a single radius of curvature (D1), the bending moment (M) on the compound curved needle will be proportionally less than that of the other needle, accounting for its increased resistance to bending and breakage. The obvious impact of the compound curved needle is an improved needle shape that permits more accurate approximation of thin planar tissues. More importantly, it is the beginning of a new era in surgical needle design in which the shape of the needle can be changed without reducing its strength. On the basis of this research, compound curved needles have been designed for closure of skin and skin grafts, dermis, oral mucosa, and large and small vessels [8-12]. Needle sharpening methods: Electrohoning. Corrosion of stainless steel needles can be minimized by electropolishing and electrohoning. Because the stainless steels are used in hardened and tempered conditions, they must be freed from all surface scale by pickling, grinding, or polishing. For full corrosion resistance, the surface must be free of all foreign particles. Consequently, electropolishing by passivating is advisable. In electrohoning, the surface of the needle is polished, while the edges of the needles are sharpened. The main difference between electropolishing and electrohoning is the composition of the electrolyte solution and the power setting of the energy cycle. Cutting edge needles were sharper after the electrohoning process than after electropolishing. The mean initial (10.2 4- 1.9 g) and maximum (15.2 4- 1.9 g) penetration forces of reverse cutting edge surgical needles (diameter 0.58 mm, length 19 mm, curvature 135") subjected to electrohoning were significantly less than the mean initial (15.2 4- 1.5 g) and the mean maximum (22.2 4- 2.1 g) penetration forces of comparable size needles made of the same stainless alloy ($45500) treated by electropolishing (p <0.05). Narrow needle point configuration. By narrowing the needle point configuration, the conventional cutting edge needles were made sharper than reverse cutting edge needles [13]. The mean initial (8.0 4- 0.5 g) and mean maximum (12.2 4- 1.0 g) penetration forces for conventional cutting edge curved surgical needles (diameter 0.58 mm, length 19 ram, curvature 135") were significantly less than the mean initial (10,0 4- 1.0 g) and mean
S
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F1 D1 > D 2 FI= F2 MI>M 2 Figure 3. Bendingmoments for the compound curved and standard needles.
maximum (15.0 4- 1.0 g) penetration forces of reverse cutting edge needles of comparable diameter, length, curvature, and alloy composition ($45500) (p <0.05). Photographs of their point configurations and measurements of point angles of their cutting edges by an optical comparator revealed notable differences, which contributed to their sharpness. The point angles of the apices (18*) of the conventional cutting edge needles were smaller than the point angles of the apices (27 ~) of the reverse cutting edge needles. Similarly, the point angles of the side cutting edges (17 ~) of the conventional cutting edge needles were smaller than the point angles of the side cutting edges (25 ~) of the reverse cutting edge needles. Finally, composite photographs confirmed that the conventional cutting edge needles exhibited a narrower point configuration than did the reverse cutting edge needles (Figure 4). Narrow cutting edge angles. The sharpness of the cutting edge of the conventional cutting edge needle was enhanced by reducing the angles of its cutting edges [14]. In the reverse and conventional cutting edge needles, the shape of the needle point was triangular with two lateral cutting edges and a cutting edge at the apex. The cutting edges of a new bevel edge needle were developed by creating opposing concave surfaces, rather than the straight planar surfaces encountered in the standard, con-
THE AMERICANJOURNALOF SURGERY VOLUME166 NOVEMBER1993
525
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Figure 4. Composite photographs at 50 X magnification of the points of the convex surface of a reverse cutting edge needle and the concave surface of a conventional cutting edge needle. The conventional cutting edge needle had a more narrow point configuration than the reverse cutting edge needle.
Figure 5. The cress-sectional area of the point of a standard conventional cutting edge needle has the configuration of an equilateral triangle. The bevel conventional cutting needle was developed by creating two opposing concave surfaces.
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ventional cutting edge needles (Figure 5). The angles of the cutting edges at the apex and sides of the bevel cutting edge needles were 45* and 52.5 ~, respectively, rather than 60* for the standard cutting edge needles. This decrease in the angles of the cutting edges enhanced the sharpness of the needle. The initial penetration forces for the bevel conventional cutting edge needles were significantly less than those for the standard conventional cutting edge needle of comparable sizes (p <0.05) (Fi~re 6). The maximum penetration forces for the bevel conventional cutting edge needles were lower than those for comparable size standard conventional cutting edge needies, but these differences were not statistically significant. Narrowing the point configuration and beveling the long side cutting edges of ophthalmic needles has also been shown to increase their sharpness [15]. Silicone coating. In the preceding studies, sharpness was judged by the magnitude of the initial and maximum penetration forces encountered by only one passage through tissue. Ideally, the sharpness of the surgical needie should be maintained after repeated passage through tissue, which was a measure of the durability of a surgical needle. When a needle was judged to be durable, it maintained its sharpness after repeated passage through tis-
526
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sue. Needle durability was quantitated by measuring the energy required to pass the surgical needle repeatedly through a specific tissue at separate sites 20 times. This frequency of passage was judged to be the average number of suture passes through tissue in a continuous running suture for a vascular anastomosis. Coating a surgical needle with silicone enhanced its sharpness and durability in tissue. The taper point needle was selected for this study because of its frequent use in aortic anastomoses in humans. Half of the needles did not receive a silicone coating; the remaining half were coated with silicone before testing. The surface of each needle was first passivated through electropolishing, after which it was coated with silicone. All coated needles were then cured tO promote surface adhesion and coating uniformity. The aorta was obtained from 20-kg domestic white pigs. After transection of a 20-cm sample of ascending aorta 4 cm from the aortic valve, the aorta was incised in a longitudinal direction, converting this tubular structure into a rectangular-shaped sample that was positioned on a special membrane holder. The aorta was oriented on the membrane holder so that the needle passed through the adventitia before passing through the aorta. The energy
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SURGICAL NEEDLES AND NEEDLE HOLDERS
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required to pass each taper point needle repetitively through the porcine aorta was measured with an Instron CR5368 needle testing f'Lxture in conjunction with an Instron Universal Testing Machine 1122. The silicone coating had considerable influence on needle sharpness and durability of taper point needles passed through porcine aorta (Figure 7). The work required for the initial penetration of the taper point needles coated with silicone was 51% less than that for the uncoated needles (p <0.05). Although the sharpness of silicone-coated needles was not significantly affected by 20 passes through the aorta, the uncoated needle became dull. The work required for the 20th pass of the uncoated needle through the porcine aorta was more than 2-fold greater than that for its initial pass (p <0.01). Laser-drilled holes for swages: The site of attachment of the suture to the needle has received considerable attention by surgeons. Prior to 1914, surgeons resorted to needles with eyes that were comparable to those of sewing needles [2]. The needles had eyes at their ends for holding the suture. The eyes of the needle were divided into two general categories, closed eye or French (split or spring). The shape of the closed eye was either round, oblong, or square. Its diameter was usually wider than that of the needle. French eye had a slit from inside the eye to the end of the needle with ridges that caught and held the suture in place. Because eyed needles must be threaded, a double strand of suture had to be pulled through the tissue. Since 1914, an eyeless needle in which the suture was attached to a drilled hole in the needle has been used [16]. This swaging process provided a smooth juncture between the needle and suture, creating a smaller hole than the threaded eye needle. This swaging process was only applicable for larger diameter needles (greater than 0.36
1
20
20
mm), because the mechanical drill could not reliably cut uniform holes in the ends of smaller needles. Consequently, a forming tool was used to create a channel in one half of the diameter of these smaller diameter needles with an underlying receptacle for attachment of the suture. The linear slit in the wall of these small needles increased the drag force encountered by the needle during passage through a synthetic membrane [17]. With the advent of the laser (yttrium-aluminum-garnet [YAG] laser), uniform holes were reliably produced in the ends of small needles, resulting in a smooth swage that encountered lower drag forces than channel needles. The lower drag forces noted with taper point needle swages produced by the laser should be associated with less mechanical trauma to the tissue. For both laser-drilled and channel needies, the sutures were securely attached to the needles [18]. The suture needle attachment strength for the laserdrilled and channel needle did not differ significantly. The laser-drilled needles have other unique advantages over the channel needles, which were related to the depth of the holes in the needle ends. The length of the channel was four times longer than that of the laserdrilled hole. Because laser-drilled and channel swages are more susceptible to bending and breakage by the needle holder jaws than the body of the needle, surgeons are warned to grasp the needle with a needle holder at a site beyond the swage. In the case of 18-ram long taper point cardiovascular needles with laser-drilled and channel swages, the depths of the laser-drilled and channel holes were 1.5 mm and 6.0 mm, respectively. In these cases, the laser-drilled taper point needle can be held by the needle holder jaws 3 mm from the needle end, whereas the channel taper point needles must be grasped 7.5 mm from the needle end. By grasping the needle close to its end, the surgeon can more easily ma-
T H E A M E R I C A N J O U R N A L OF S U R G E R Y
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527
EDLICH ET AL
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Figure 8. The needle suture products w h o s e n e e d l e : s u t u r e r a t i o approached 1 had the lowest fluid loss through the needle puncture sRe in the polytetrafluoroethylenegraft.
1.4
TABLE I
Biomechanical Properties of Needle Holders Clamping Force* Length
FF
LLt
Type
(in)
(N)
(cm)
(cm)
I_jt
Halsey Crile-Wood Microvascular DeBakey Mayo-Hegar
5 6 7 7 7
11.70 14.51 13.55 13.76 17.63
8.86 11.21 13.72 13.40 13.68
2.39 2,55 2.97 2.95 2.89
Mechanical
Advantagew 3.71 4.40 4.62 4.54 4.73
Width** (cm)
Applied Clamping Moment+ (N/cm)
0,20 0.23 0.17 0.21 0.27
2.17 3,67 2.66 3.28 5.63
*At first ratchet setting with a curved needle (0.58 mm wire diameter) 2 mm from jaw tip. 1Length of the handle from the fulcrum to the site at which force is applied to ringlets. SLength of the jaw from the fulcrum to the point at which jaw holds the needle 2 mm from the tip of the jaw. w **Two millimetersfrom needle jaw tip. +Clamping force • mechanical advantage • jaw width + length
nipulate the passage of the needle through tissue. This benefit of the laser-drilled needles was accomplished without altering the needle suture attachment strength. These distinct advantages of swages produced by lasers indicated that they should eventually replace all channel swage needles. Needle:suture ratio of 1:1: The introduction and wide acceptance of polytetrafluoroethylene (PTFE) grafts have focused considerable attention on the bleeding occurring during vascular anastomosis [19,20]. One of the characteristics of this material is that a needle hole placed in this graft remains approximately the same size as the needle. Needle-hole bleeding is due to the disparity between the diameter of the needle making the hole and the diameter of the suture filling it. Because the vascular surgical monofilament sutures currently in use have a needle:suture diameter ratio of approximately 2:1, the 528
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difference between the sizes of the needles and sutures leaves an unfilled space at each suture hole, through which bleeding occurs. To resolvethis problem of bleeding through the holes in the P T F E grafts,two new cardiovascular suturesattached to taper point needles have been developed [21].One monofilament suture made of P T F E (W.L. Gore & Associates Inc.,Elkton, M D ) isproduced with a porous microstructure, which is approximately 50% air by volume. Its porous structure allows it to be swaged to a needle that closely approximates its suture diameter, having a needle-to-suturediameter ratio that approaches 1:1.The other suture,calledHemoscal (Ethicon, Inc.,Somerville,N J) suture,isa monofilament polypropylene suture that has been extruded to produce a tapered swage end, which is significantlysmaller than that of the remainder of the suture in order for it to be channel swaged to smaller diameter needles.
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SURGICAL NEEDLES AND NEEDLE HOLDERS
A dosed fluid system was developed to measure fluid jaw (w) width was measured using calipers at the needle leakage following penetration of a PTFE graft by differ- clamping site. The needle holder was then placed verticalent suture needle types. This closed system had four com- ly in a machinist's vise on top of a small compression load penents: (1) graft, (2) damp, (3) pressure transducer, cell. The ringlets of the needle holder were then comand (4) infusion pump. A 10-cm damped segment of pressed manually so that either the first, second, or third graft was attached to a pressure transducer using a medi- ratchet setting interlocked. The crosshead of the Instron trace disposable pressure monitoring product. An infu- Universal Tensile Tester was then lowered at 50 mm/min sion pump was incorporated through the pressure trans- until the force applied to the ringlets disengaged the interducer to introduce additional fluid that maintained a locking teeth, after which the movement of the crosshead constant system pressure of 80 mm Hg in the event that a was then stopped. As the direction of the crosshead was leak initiated a pressure loss. This system was tested with reversed, the force applied to the ringlet (FF) was record0.9% sodium chloride. Following a single suture passage ed until the teeth in the specified ratchet setting reeninto the graft, the rate of fluid loss around the suture was gaged. The maximal force encountered just before endetermined by measuring the rate of fluid infused to gagement of the interlocking teeth was judged to be the maintain a constant closed system pressure. This amount force required for engagement of the specified ratchet of infused fluid was always equivalent to the fluid leakage setting. This force influenced the applied clamping mofrom the graft. ment of the needle holder on the needle at the designated Although the diameters of the sutures were remark- ratchet setting. The measurement was repeated eight ably similar (Hemoseal and standard polypropylene di- times at the specified ratchet setting and at the measured ameter 0.23 mm and PTFE diameter 0.28 mm), the distance from the jaw tip using a new needle for each test. diameter of the standard needle (0.56 mm) was nearly The damping moment was calculated as previously detwo-fold wider than those of the Hemoseal (0.33 mm) scribed. and Gore (0.38 ram) needles. Consequently, the neeThe damping moment of the needle holder was didie:suture ratios of the Hemoseal and Gore products ap- rectly related to its mechanical advantage (LL/Lj), the proached one, whereas the standard needle:polypropy- damping force, and the jaw width at the site of the needle lene suture ratio exceeded two. The magnitude of the loss (Table I). The Halsey needle holder had the smallest of 0.9% sodium chloride from the needle puncture site damping moment, whereas the Mayo Hegar had the was proportional to the needle:suture ratio of the product greatest. The magnitude of the damping moment was (Figure 8). The loss of 0.9% sodium chloride from the significantly influenced by the size of the needle diameneedle puncture site was greatest with the standard prod- ter, the location of the needle between the needle holder uct whose needle:suture ratio was 2.4. When the Hemo- jaws, and the ratchet setting of the needle holder [6]. seal needle product with a 1.4 needle:suture ratio pene- When needle holder jaws clamped different diameter trated the graft, the needle puncture fluid loss from the needles at the site 2 mm from the jaw tip, the needle standard product was reduced by 79%. The needle punc- holder damping moments on the larger diameter needles ture fluid loss following needle puncture with the Gore- (0.58 mm) were significantly greater than those on the Tex needle suture product with a needle:suture ratio of smaller diameter needles (0.43 mm) (p <0.05). When the 1.4 was negligible. needle was advanced to sites 2 mm, 3 mm, and then 5 mm Atraumatie needle holder: Needle yield moment from the jaw tip, there were significant incremental inand needle holder clamping moment compatibility. Se- creases in the damping moments (p <0.05). Similarly, lecting the appropriate needle holder for a designated advancing the ratchet setting from the first, second, and needle can be accomplished by relating the damping third interlocking teeth resulted in significant increases in moment of the needle holder at the specified ratchet the jaw clamping moments (p <0.05). setting to the yield moment for the needle placed in a In Hgure 9, the clamping moments of seven different measured site in the needle holder jaws. Ideally, the sur- needle holders were related to the yield moments of cargeon should use a needle holder whose damping moment diovascular taper point (RB-1) and tapercut (V-5) neeis less than that of the yield moment of the needle. Clamp- dies manufactured by Ethicon Inc. [22]. The clamping ing a needle whose yield moment is greater than the moment of the needle holders were recorded at the first damping moment of the needle holder will result in re- ratchet setting with a 0.58-mm diameter PS2 needle posiversible deformation of the needle. When the clamping tioned 2 mm from the jaw tip. The diameters (0.66 mm) moment of the needle holder exceeds the needle yield of the cardiovascular needles were very similar to that of moment, damping the needle between the jaws of the the PS2 needle. Because the clamping moments of the needle holder will result in irreversible needle deforma- needle holders were less than the yield moments of the tion, with a subsequent enlargement of needle chord cardiovascular needles, these needle holders could be length. used at this ratchet setting without permanent needle The clamping moments exerted by needle holder jaws deformation. of six different needle holders (Snowden Pencer, Tucker, This compatibility between the needle holder dampGA) were recorded at specific ratchet settings. During ing moments and the yield moments of the cardiovascular measurements of damping moments, needles of varying needles was not encountered with the reverse and convendiameter (0.43 mm and 0.58 mm) were positioned at tional cutting edge needles whose diameters were 0.56 to spocified distances from the needle holder jaw tip. The 0.58 mm (Figure 10). Because the clamping moments of THE AMERICAN JOURNAL OF SURGERY
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CARDIOVASCULAR TAPERCUT(V-5) AND TAPERPOINT (RB-1) NEEDLES
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CUTTING EDGE NEEDLES
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NEEDLE HOLDER (First Ratchet Setting) Figure 10. Relationship between the yield moments of 0.56- to 0.58-mm diameter conventional and reverse cutting edge needies and the clamping moments of needle holders at their first r a t ~ e t setting with the 0.58-rnm diameter needle positioned 2 m m from the jaw tip.
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T H E A M E R I C A N J O U R N A L OF S U R G E R Y
the Halsey and microvascular needle holders were less than the yield moments of cutting edge needles, these needle holders could be used at the first ratchet setting with all cutting edge needles without permanent deformation. In contrast, the clamping moment of the Mayo Hegar needle holder exceeded the yield moments of the FS2, PS4, and PC5 PRIME needles, indicating that it will permanently deform these needles. Textured tungsten carbide jaw inserts. The design of the needle holder jaw is another important consideration in the selection of a needle holder. Tungsten carbide inserts with teeth, varying from 2,500 to 16,000 teeth/ inch2, have been incorporated into the jaws of the needle holder to enhance its needle holding security [23]. The presence of teeth within the needle holder jaws limits twisting and rotation of needle as compared with needle holder jaws without teeth. These teeth stabilize the needle, allowing the surgeon to accurately control the passage of the needle through the tissue. While appreciating the potential benefits of tungsten carbide jaw inserts with teeth in achieving needle holding security, the surgeon should also realize the potential deleterious effects of the teeth on suture materials and needles [24-26]. These teeth can produce distinct morphologic changes in monofilament synthetic sutures that markedly reduce their breaking strength [24]. The implications of this sutural damage on the strength of continuous monofilament synthetic suture in surgery are obvious. Finally, these teeth can alter the structural configuration of needles by producing stress concentrations, thereby reducing their resistance to either bending or breakage
[25,26]. Smooth needle holder jaws with rounded edges did not induce structural damage to either monofilament suture or needles [27]. However, their smooth jaw surface provided limited resistance to either the twisting or rotation of the needle between the jaws. A textured needle holder jaw metallurgicaUy bonded with tungsten carbide particles appears to be an attractive alternative to either smooth needle holder jaws or those with teeth [27]. Although its needle holding security was significantly less than the jaws with teeth, it provided greater needle holding security than the smooth jaws. By enhancing the average surface roughness of the jaw, the embedded tungsten carbide particles of the textured jaw surface resisted twisting and rotational moments of the needle. Unlike the sutural damage inflicted by the jaws with teeth, compression of the synthetic monofilament suture by either the smooth jaws or textured jaws with tungsten carbide particles did not weaken the monofilament suture. Rounded jaw edges. Recent studies demonstrated that the sharp outer edges of smooth needle jaws cut the smooth surface of monofilament sutures, weakening its strength [28]. When the smooth tungsten carbide inserts of needle holders clamped 6-0 monofilament nylon suture with the first opposing teeth of the needle holder ratchet mechanism interlocked, there was a significant reduction in suture breaking strength. This sutural damage can be prevented by mechanical grinding the outer edges of the
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smooth tungsten carbide inserts, resulting in a rounded edge. Clamping the suture with the smooth jaws of the needle holder with rounded edges was atraumatic, with no demonstrable damage to the suture's breaking strength. Another approach to enhance the needle holding security was tochange the configuration of the needle body to allow the needle holder to hold it more securely [23]. However, changes in the configuration of the needle body were considerably less important than either the presence of teeth in the tungsten carbide jaw inserts or advancement of the engagement of the ratchet setting of the needle holder. In addition, the presence of longitudinal ridges on the concave or convex surface of the needle or on both surfaces did not decrease undesirable twisting or rotational movements of the needle. FUTURE During the last two decades, standard, reproducible tests have been devised that determine the biomechanical performance of surgical needle and needle holders. These tests can ensure quality control of the manufactured products as well as provide a frame of reference for the development of new, improved products. The need for reliable quality control standards is especially apparent in the manufacturing of surgical needle holders. Because the vast majority of needle holders are manufactured by companies in Germany and Pakistan, it has been difficult to institute reliable quality control programs. Today, the biomechanical performance of needle holders has an unacceptably large degree of variability [29,30]. This resistance to quality control standards by the manufacturers is associated with an indifference to the development of innovative products. With the advent of new surgical techniques, there is an urgent need for development of lighter-weight needle holders that are atraumatic to sutures and needles [31]. Fortunately, American-owned companies manufacture most of the surgical needles used in the world. The quality control of the manufactured needle products is superior. It is also gratifying that these companies are not resting on their laurels and are designing new needle products for the 21st century. New alloys are being developed that have a greater resistance to bending and breakage than the $45500 stainless steel. New coatings for needles are being devised that will eventually replace the silicone coating. New attention is being paid to packaging systems for needles, which ensure that their delicate points are protected from damage. CONCLUSION During the last two decades, seven major advances in surgical needle and needle holder technology have markedly improved surgical wound repair. These advances include quantitative tests for surgical needle and ne~ile holder performance, high nickel maraging stainless steels, compound curve needle, needle sharpening methods, laser-drilled holes for swages, needle:suture ratios of 1:1, and the atraumatic needle holder. The quantitative tests for surgical needle and needle holder performance
are measurements of needle sharpness, needle resistance to bending, needle ductility, and needle holder clamping moment. New needle sharpening methods involve dectrohoning, narrowing needle point configuration, reducing cutting edge angles, and silicone coating. The atraumatic needle holder has been achieved by ensuring needle yield moment and needle holder clamping moment compatibility, and developing textured tungsten carbide jaw inserts and rounded needle holder jaw edges. These advances in surgical needle and needle holder technology provide a scientific basis for selecting surgical needle and needle holders as well as insight into future technologic advances that are on the horizon. REFERENCES 1. Van Winkle W Jr, Hastings JC. Considerations in the choice of suture materials for various tissues. Surg Gynecol Obstet 1972; 135: 113-26. 2. Trier WC. Considerations in the choice of surgical needles. Surg Gynecol Obstet 1979; 149: 84-94. 3. Thacker JG, Rodeheavcr GT, Towler MA, Edlich RF. Surgical needle sharpness. Am J Surg 1989; 157: 334-9. 4. Abidin MR, Towler MA, Rodeheavcr GT, Thacker JG, Cantrell RW, Edlich RF. Biomechanicsof curved surgical needle bending. J Biomater Res 1989; 23: 129-43. 5. Abidin MR, Towler MA, Nochimson GD, Rodcheaver GT, Thacker JG, Edlich RF. A new quantitative measurement for surgical needle ductility. Ann Emerg Med 1989; 18: 64-8. 6. Edlich RF, Towler MA, Rodeheaver GT, Becker DG, Lornbardi SA, Thacker JG. Scientific basis for selecting surgical needles and needle holders for wound closure. Clin Plast Surg 1990; 17: 583-602. 7. Ayer R, Bendel LP, Zackay VP. Metastable precipitate in a duplex martensite ferrite precipitation-hardening stainless steel. Metallurgical Trans A 1992; 23A: 1-7. 8. Abidin MR, Becker DG, Paley RD, et al. A new compound curved needle for intradermal suture closure. J Emerg Med 1989; 7: 441-4. 9. Edlich RF, Zimmer CA, Morgan RF, et al. A new compoundcarved needle for microvascular surgery. Ann Plast Surg 1991; 27: 339-44. 10. Tribble CG, Moody FP, Girard P, et al. A new, compound carved needle for vascular surgery. Am Surg 1992; 58: 458-62. l l . Hoard MA, Franz DA, Bellian KT, Edlich RF. A new compound curved tapcrcat needle for oral surgery. J Oral Maxillofac Surg 1992; 50: 484-9. 12. Cook TS, Towler MA, Girard P, McGregor W, Dcvlin PM, Edlich RF. A new compound curved needle for skin and skin graft suture closure. J Burn Care Rehab 1992; 13: 650-5. 13. Towler MA, McGregor W, Rodcheaver GT, et al. Influence of catting edge configuration on surgical needle penetration forces. J Emerg Med 1988; 6: 475-81. 14. Kaulbach HC, Towler MA, McClelland WA, et al. A beveled, conventional cutting edge surgical needle: a new innovation in wound closure. J Emerg Med 1990; 8: 253-60. 15. McClung WL, Thacker JG, Edlich RF, Allen RC, Rodeheaver GT. Biomechanical performance of ophthalmic surgical needles. Ophthalmology 1992; 99: 232-7. 16. Minahan PR. Eyeless needle. United States Patent Office. No. 1,106,667, Aug. 11, 1914. 17. Tow|er MA, Clapp CG, McGregor W, Morgan RF, Edlich RF. Laser-drilled cardiovascular surgical needles. J Appl Biomater 1991; 2: 183-6. 18. Ahn LC, Towler MA, McGregor W, Thacker JG, Morgan RF,
THE AMERICAN JOURNAL OF SURGERY VOLUME 166 NOVEMBER 1993 531
EDLICH ET AL
Edlich RF. Biomechanical performance of laser-drilled and channel taper point needles. J Emerg Med 1992; 10: 601-6. 19. Miller CM, Sangiolo P, Jacobson JH II. Reduced anastomotic bleeding using new sutures with a needle-suture diameter ratio of one. Surgery 1987; 101: 156-60. 20. Garcia-Rinaldi R, Revuelta JM, Poeppel R, Treager K, Black D, Kirby JM. Clinical experience with expanded polytetrafluoroethylene suture. Bol Asoc Med P R 1986; 78: 335-8. 21. Towler MA, Tribble CG, Pavlovich LJ, Milam JT, Morgan RF, Edlich RF. Biomechanical performance of new vascular sutures and needles for use in polytetrafluoroethylenegrafts. J Biomat Res 1993; 4: 87-95. 2 2 . Bellian KT, Thacker JG, Tribble CG, et al. Biomechanical performance of tapercut cardiovascular needles.Am Surg 1991; 57: 591-601. 23. Thacker JG, Borzelleca DC, Hunter JC, McGregor W, Rodehearer GT, Edlich RF. Biomechanical analysis of needle holding security. J Biomed Mater Res 1986; 20: 903-17. 24,. Stamp CV, McGregor W, Rodeheaver GT, Thacker JG, Towler MA, Edlich RF. Surgical needle holder damage to sutures.
532
Am Surg 1988; 54: 300-6. 25. Abidin MR, Thacker JG, Lombardi SA, et al. Needle holder damage to surgical needles. Am Surg 1989; 55: 681-4. 26. Bond RF, McGregor W, Cutler PV, Becket DG, Thacker JG, Edlich RF. Influence of needle holder jaw configuration on curved surgical needle bending. J Biomed Mater Res 1990; 1: 39-47. 27. Abidin MR, Dunlap JA, Towler MA, et al. Metallurgically bonded needle holder jaws. A technique to enhance needle holding security without sutural damage. Am Surg 1990; 56: 643-7. 28. Abidin MR, Towler MA, Thacker JG, Nochimson GD, McGregor W, Edlich RF. New atraumatic rounded-edge surgical needle holder jaws. Am J Surg 1989; 157: 241-2. 29. Chen NC, Towler MA, Moody RF, et al. Mechanical performance of surgical needle holders. J Emerg Med 1991; 9: 5-13. 30. Francis Eli III, Towler MA, Moody RP, et al. Mechanical performance of disposable surgical needle holders. J Emerg Med 1992; 10: 63-70. 31. Towler MA, Chen NC, Moody FP, et al. Biomechanics of a new atraumatic surgical needle holder. J Emerg Med 1991; 9: 477-86.
THE AMERICAN JOURNAL OF SURGERY VOLUME 166 NOVEMBER 1993
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 needie 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 atraumatie needle holder.
1972, Van Winkle and Hastings [1] published a colItheynlective review of surgical suture materials in which proposed a sound scientific basis for the selection of sutures based upon the results of scientific studies that documented the effects of surgical sutures on the healing wound. Three years later, Trier [2] wrote his collective review to provide a rational criteria for needle and needle holder selection. There were notable differences in the tasks and approaches to these two collective reviews. First, Van Winkle and Hastings [1] confined their review to the 6 different suture materials commonly used in clinical operations, whereas Trier [2] provided an overview of 100 needle choices i n 9 different shapes and a variety of needle holders bearing the name of the inventive surgeons. Van Winkle and Hastings [1] had the benefit of large numbers of well-designed experimental and clinical investigations that provided a scientific basis for the selection of surgical sutures. In contrast, Trier's [2] review was based exclusively on testimonials of talented surgeons, the manufacturers' catalogs, and his extensive clinical experience as a skilled plastic surgeon. In the absence of well-designed scientific studies, Trier's [2] report served as an excellent overview and classification of surgical needle and needle holder products, which has provided considerable direction for our comprehensive scientific studies during the last two decades. Our studies have focused on seven major advances in surgical needle and needle holder technology that have markedly improved surgical wound repair. These advances include quantitative tests for surgical needle and needle holder performance, high nickel maraging stainless steels, compound curved needles, needle-sharpening methods, laserdrilled holes for swages, needle:suture ratios of 1:1, and the atraumatic needle holder. These recent advances in surgical needle and needle holder technology provide a scientific basis for selecting surgical needle and needle holders as well as insight into future technologic advances that are on the horizon.
PRESENT Quantitative tests for surgical needle and needle holder performance: The biomechanical performance of the surgical needles and needle holders was determined by the following parameters: (1) needle sharpness, (2) needle resistance to bending, (3) needle ductility, and (4) Fromthe Departmentof PlasticSurgery(RFE,WM, GTR),University of VirginiaSchoolof Medicine,and the Departmentof Mechanical needle holder clamping moment. The sharpness of the and AerospaceEngineering(JGT), Universityof Virginia,Charlottes- surgical needle was determined by measuring the maxiviUe,Virginia. mum vertical force required for it to penetrate a thin Supported by a grant fromthe TexacoFoundation,WhitePlains, laminated synthetic membrane (Medpar 1220, 3M CenNew York. Requests for reprints should be addressedto Richard F. Edlieh, ter, St. Paul, MN) [3]. This test was accomplished with MD, PhD, Departmentof Plastic Surgery,Box 332, Charlottesville, an Instron Model CR5368 Curved Needle Testing Fixture in conjunction with an Instron 1122 Universal TestVirginia22908. 522
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SURGICAL NEEDLES AND NEEDLE HOLDERS
ing Machine (Instron Corp., Canton, MA). The testing apparatus rigidly held the curved needle in a set of jaws that rotated through an arc equal to the curvature of the needle. The needle was made to penetrate the supported membrane, and the forces necessary to cause passage through the membrane were recorded as a force versus angle position curve. When the point of the needle passed through the membrane, there was a detectable decrease in the magnitude of the penetration force (initial needle penetration force/g), after which the penetration force rose to a maximum peak (maximum penetration force/g) as the needle's tapered geometry passed through the membrane. With the advent of the electronic load cell transducer, the bending resistance of the curved surgical needle generated a force-angular deflection curve that allowed quantitation of the resistance to needle bending [4]. In these tests, the bending forces were sensed by the strain gauge load cell transducer and recorded on a strip chart recorder. The bending force needed to deform the curved needle was recorded as a function of the angular deformation of the needle. The vertical axis on the strip chart recorder was calibrated to record force, whereas the horizontal axis was linearly related to the angular rotation of the needle. Because the moment arm remained constant, the bending moment was proportional to the bending force. During each test, bending of the needle resulted in an angular deformation versus bending moment curve that was analyzed to give a yield moment and an ultimate bending moment. Typically, the curve exhibited an initial linearly elastic deformation region, followed by a nonlinear plastic deformation region. Because there was no clear distinction for some needles between the elastic and plastic regions of this bending curve, it was difficult to identify the applied moment at which permanent deformation occurred. To identify a reproducible yield moment for this test, a 2* offset yield technique was used that followed the same principle as the classic 0.2% offset strain method commonly used in tensile testing [4]. This 2 ~ value was chosen because it represented a distinct point of demarcation from the linear line. The yield moment was identified at the intersection of this offset line with a test curve. Bending tests on curved needles whose applied bending moments were less than the yield moments resuited in needle elastic deformations that were completely recoverable, whereas applied bending moments greater than the yield moments caused needle plastic or irreversible deformation. The ultimate moment was defined as the greatest bending moment on the curve, with the maximum angle of bend for the curved needle being 90 ~ due to limitation imposed by the test apparatus. Ductility or resistance to surgical needle breakage was measured by the curved surgical needle bend tester, which determined the work required to completely fracture a surgical needle [5]. For this ductility test, the stepping motor of the curved needle bend tester was calibrated to rotate the curved needle at a constant angular speed. During a typical ductility test, bend forces were recorded as each test needle was cyclically bent through
arcs of 90 ~. To obtain the work required for needle breakage, the area under the moment-deflection curve was calculated using a computer software package. The total amount of work required to bend the needle back and forth through a 90* arc until fracture was the measurement of needle ductility. Needle holder clamping moment is an important measure of needle holder performance. The needle holder consists of two first-class levers that rotate on a common fulcrum. The portions of the levers that grasp the needle are distal to the fulcrum and are called the jaws. The remaining portion of the lever, that portion that is held by the surgeon, is called the handle. When a circular needle is clamped between the jaws of the needle holder, the needle contacts the jaws at three different sites. At midpoint in one jaw, a clamping force (F j) is applied to one site on the convex surface of the needle. Each edge of the opposing jaw surface applies separate and equal forces to the concave surface of the needle. The magnitude of these forces is exactly half the total clamping force (Fj/2). Because Fj acts at the point of the maximum bending moment, its moment is 0 and therefore does not contribute to the calculated bending moment. In contrast, the applied force at the edge of the needle holder jaw has a moment arm equivalent to one-half the jaw width (W/2). Consequently, the maximum needle holder clamping moment (Me) exerted on the needle is a product of the clamping force at one edge of the needle (F j/2) times the length of its moment arm (W/2) from the line of action of this force to the center of the clamped needle. Mc = Fj/2 x W/2 = FjW/4 The force resulting from the closure of the jaws (Fj) is directly proportional to the length of the handles and inversely related to the length of the jaws, and can be calculated by the following lever equation (Figure 1): F j = FFLL/LJ where: F j --- force applied by the jaws of the needle holder FF = force applied by fingers to ringlets of the needle holder LL = length of the handle from the fulcrum to the site at which force is applied to ringlets Lj = Length of the jaw from fulcrum to point at which jaw holds the needle
These equations have been validated by relating the clamping moments of the needle holder jaw to the yield bending moments of surgical needles [6]. High nickel maraging stainless steel: Iron is never found alone in nature, hut exists in the form of oxides, carbonates, and sulphides. Steel is a more refined grade of iron with a reduced carbon content. Every alloying element has a particular effect on steel. Technically, carbon should not be considered an alloying clement because without it steel would not exist, but would remain iron.
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EDLICH ET AL
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Figure 2. The compound curved needle had two distinct radii of curvature, whereas the standard curved needle only had one radius of curvature.
Varying amounts of carbon in steel have a profound effect on its properties. When a combination of two or more elements exists in the steel, the total result is an increase in each of the characteristics that is greater than the sum of the individual effects. Stainless steels have excellent resistance to corrosion. All true stainless steels contain a minimum of about 12% chromium, which allows a thin protective surface layer of chromium oxide to form when the steel is exposed to oxygen. Since their development during the early sixties, high nickel maraging stainless steels have found extensive use in structural materials in many applications requiring a combination of high strength and toughness [7]. The basic principle of maraging consists of strengthening FeNi martensitic matrices by the precipitation of fine intermetallic phases such as Ni3 Ti. These precipitates are so small that they are only evident on transmission electron microscopy. They strengthen the metal by preventing the planes of atoms in the stainless steel from sliding over each other. A high nickel maraging stainless steel, like $45500, is composed of 7.5% to 9.5% nickel, 0.8% to 1.4% titanium, and 11% to 12.5% chromium. In contrast, $42000 stainless steel is composed of 12% to 14% chromium without nickel or titanium. Scientists have successfully utilized the concept of high nickel maraging stainless steels ($45500) to develop stainless steel wires with superior strength and ductility for use as surgical needles
[4,5]. Surgical needles made of high nickel maraging stain524
THE AMERICAN JOURNAL OF SURGERY
less steel, like $45500, have a greater resistance to bending and breakage than stainless steels without nickel, like $42000. The mean yield moment (5.7 4- 0.3 N-cm) and mean ultimate moment (8.1 4- 0.8 N-cm) of curved surgical needles (diameter 0.58 mm, length 19 mm, curvature 135 ~ made of $45500 stainless steel were significantly greater than the mean yield moment (3.6 4- 0.3 N-cm) and mean ultimate moment (5.9 4- 0.5 N-cm) of comparable size needles made of $42000 stainless steel (p <0.05). Similarly, the work to fracture (19.6 4- 2.9 N-cm) these $45500 surgical needles was significantly greater than the work to fracture (12.9 4- 1.1 N-cm) comparable size surgical needle made of $42000 stainless steel (p <0.05). Compound curved needle: Needles used for closure of thin planar structures (e.g., skin, vessels, etc.) have usually been semicircular needles with a single radius of curvature measuring 135 ~. Although needle sharpness and resistance to bending and breakage are important considerations, they will not provide optimal needle control necessary for accurate approximation of these structures without concomitant attention to needle shape. Needle shape or curvature has, until now, been the most neglected design parameter in the quest to improve needle performance. With the advent of high nickel maraging stainless steel alloys, the shape of the needle can be easily changed without altering its resistance to bending. By using this alloy, a new compound curved needle has been specifically designed and developed for closure of thin planar structures (Figure 2). This needle has a short, straight point, followed by a curved distal section. This needle exhibited a greater resistance to bending than a comparable size curve needle with a single radius of curvature. The mean yield moment (7.2 4- 0.2 N-cm) and the mean ultimate moment (9.5 4- 0.4 N-cm) of the compound curved needies were significantly greater than the mean yield moment (6.0 4- 0.3 N-cm) and the mean ultimate moment (8.1 4- 0.4 N-cm) of surgical needles with a single radius of curvature with the same diameter and high nickel maraging stainless steel alloy (p <0.05). The shape of the compound curved needle has several advantages over the needle with one radius of curvature
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for closure of these tissues. Its relatively straight point facilitates the initial entrance through the tissue as well as controls the depth of penetration. Its tight needle curvature beyond the tip permits rapid, accurate needle passage at a selected depth and controlled exiting. Its design also provides a mechanical advantage over the standard needle that enhances its resistance to bending (Figure 3). The bending moment (M) that can be applied to the needle body is directly related to the needle's susceptibility to irreversible bending. The applied bending moment is determined by multiplying the tissue forces (F) that resist needle penetration by the needle moment arm (D), which is the perpendicular distance between the line of action of the tissue forces and the centroid needle's cross-section that emerges between the needle holder jaws. Because the moment arm (D2) of the compound curved needle is significantly less than that of the standard needle with a single radius of curvature (D1), the bending moment (M) on the compound curved needle will be proportionally less than that of the other needle, accounting for its increased resistance to bending and breakage. The obvious impact of the compound curved needle is an improved needle shape that permits more accurate approximation of thin planar tissues. More importantly, it is the beginning of a new era in surgical needle design in which the shape of the needle can be changed without reducing its strength. On the basis of this research, compound curved needles have been designed for closure of skin and skin grafts, dermis, oral mucosa, and large and small vessels [8-12]. Needle sharpening methods: Electrohoning. Corrosion of stainless steel needles can be minimized by electropolishing and electrohoning. Because the stainless steels are used in hardened and tempered conditions, they must be freed from all surface scale by pickling, grinding, or polishing. For full corrosion resistance, the surface must be free of all foreign particles. Consequently, electropolishing by passivating is advisable. In electrohoning, the surface of the needle is polished, while the edges of the needles are sharpened. The main difference between electropolishing and electrohoning is the composition of the electrolyte solution and the power setting of the energy cycle. Cutting edge needles were sharper after the electrohoning process than after electropolishing. The mean initial (10.2 4- 1.9 g) and maximum (15.2 4- 1.9 g) penetration forces of reverse cutting edge surgical needles (diameter 0.58 mm, length 19 mm, curvature 135") subjected to electrohoning were significantly less than the mean initial (15.2 4- 1.5 g) and the mean maximum (22.2 4- 2.1 g) penetration forces of comparable size needles made of the same stainless alloy ($45500) treated by electropolishing (p <0.05). Narrow needle point configuration. By narrowing the needle point configuration, the conventional cutting edge needles were made sharper than reverse cutting edge needles [13]. The mean initial (8.0 4- 0.5 g) and mean maximum (12.2 4- 1.0 g) penetration forces for conventional cutting edge curved surgical needles (diameter 0.58 mm, length 19 ram, curvature 135") were significantly less than the mean initial (10,0 4- 1.0 g) and mean
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maximum (15.0 4- 1.0 g) penetration forces of reverse cutting edge needles of comparable diameter, length, curvature, and alloy composition ($45500) (p <0.05). Photographs of their point configurations and measurements of point angles of their cutting edges by an optical comparator revealed notable differences, which contributed to their sharpness. The point angles of the apices (18*) of the conventional cutting edge needles were smaller than the point angles of the apices (27 ~) of the reverse cutting edge needles. Similarly, the point angles of the side cutting edges (17 ~) of the conventional cutting edge needles were smaller than the point angles of the side cutting edges (25 ~) of the reverse cutting edge needles. Finally, composite photographs confirmed that the conventional cutting edge needles exhibited a narrower point configuration than did the reverse cutting edge needles (Figure 4). Narrow cutting edge angles. The sharpness of the cutting edge of the conventional cutting edge needle was enhanced by reducing the angles of its cutting edges [14]. In the reverse and conventional cutting edge needles, the shape of the needle point was triangular with two lateral cutting edges and a cutting edge at the apex. The cutting edges of a new bevel edge needle were developed by creating opposing concave surfaces, rather than the straight planar surfaces encountered in the standard, con-
THE AMERICANJOURNALOF SURGERY VOLUME166 NOVEMBER1993
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EDLICH ET AL
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Figure 4. Composite photographs at 50 X magnification of the points of the convex surface of a reverse cutting edge needle and the concave surface of a conventional cutting edge needle. The conventional cutting edge needle had a more narrow point configuration than the reverse cutting edge needle.
Figure 5. The cress-sectional area of the point of a standard conventional cutting edge needle has the configuration of an equilateral triangle. The bevel conventional cutting needle was developed by creating two opposing concave surfaces.
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0.56
0.35 .
ventional cutting edge needles (Figure 5). The angles of the cutting edges at the apex and sides of the bevel cutting edge needles were 45* and 52.5 ~, respectively, rather than 60* for the standard cutting edge needles. This decrease in the angles of the cutting edges enhanced the sharpness of the needle. The initial penetration forces for the bevel conventional cutting edge needles were significantly less than those for the standard conventional cutting edge needle of comparable sizes (p <0.05) (Fi~re 6). The maximum penetration forces for the bevel conventional cutting edge needles were lower than those for comparable size standard conventional cutting edge needies, but these differences were not statistically significant. Narrowing the point configuration and beveling the long side cutting edges of ophthalmic needles has also been shown to increase their sharpness [15]. Silicone coating. In the preceding studies, sharpness was judged by the magnitude of the initial and maximum penetration forces encountered by only one passage through tissue. Ideally, the sharpness of the surgical needie should be maintained after repeated passage through tissue, which was a measure of the durability of a surgical needle. When a needle was judged to be durable, it maintained its sharpness after repeated passage through tis-
526
0
056
056
Figure 6. The initial penetration forces for the bevel conventional cutting edge needles were significantly less than those for the standard conventional cutting edge needles (p
<0.05).
sue. Needle durability was quantitated by measuring the energy required to pass the surgical needle repeatedly through a specific tissue at separate sites 20 times. This frequency of passage was judged to be the average number of suture passes through tissue in a continuous running suture for a vascular anastomosis. Coating a surgical needle with silicone enhanced its sharpness and durability in tissue. The taper point needle was selected for this study because of its frequent use in aortic anastomoses in humans. Half of the needles did not receive a silicone coating; the remaining half were coated with silicone before testing. The surface of each needle was first passivated through electropolishing, after which it was coated with silicone. All coated needles were then cured tO promote surface adhesion and coating uniformity. The aorta was obtained from 20-kg domestic white pigs. After transection of a 20-cm sample of ascending aorta 4 cm from the aortic valve, the aorta was incised in a longitudinal direction, converting this tubular structure into a rectangular-shaped sample that was positioned on a special membrane holder. The aorta was oriented on the membrane holder so that the needle passed through the adventitia before passing through the aorta. The energy
THE AMERICAN JOURNAL OF SURGERY VOLUME 166 NOVEMBER1993
SURGICAL NEEDLES AND NEEDLE HOLDERS
35.7 + 13.2 J
AORTA -Q-(0.25mm) (13mm) (135~ 35
SILICONE COATING
J'---1 NO COATING
I
!
A
o
25
v
Z O m I'--
,,, Z iii
20 13.8 _+3.1
15
D..
u_
0
10
v
0 Figure 7, Silicone coating of a taper point needle increased its sharpness and durability during repetitive passes through a porcine aorta.
6.8 _+2.7
.L J
+8.0 2.7 -_
5
PASSES NO
1
required to pass each taper point needle repetitively through the porcine aorta was measured with an Instron CR5368 needle testing f'Lxture in conjunction with an Instron Universal Testing Machine 1122. The silicone coating had considerable influence on needle sharpness and durability of taper point needles passed through porcine aorta (Figure 7). The work required for the initial penetration of the taper point needles coated with silicone was 51% less than that for the uncoated needles (p <0.05). Although the sharpness of silicone-coated needles was not significantly affected by 20 passes through the aorta, the uncoated needle became dull. The work required for the 20th pass of the uncoated needle through the porcine aorta was more than 2-fold greater than that for its initial pass (p <0.01). Laser-drilled holes for swages: The site of attachment of the suture to the needle has received considerable attention by surgeons. Prior to 1914, surgeons resorted to needles with eyes that were comparable to those of sewing needles [2]. The needles had eyes at their ends for holding the suture. The eyes of the needle were divided into two general categories, closed eye or French (split or spring). The shape of the closed eye was either round, oblong, or square. Its diameter was usually wider than that of the needle. French eye had a slit from inside the eye to the end of the needle with ridges that caught and held the suture in place. Because eyed needles must be threaded, a double strand of suture had to be pulled through the tissue. Since 1914, an eyeless needle in which the suture was attached to a drilled hole in the needle has been used [16]. This swaging process provided a smooth juncture between the needle and suture, creating a smaller hole than the threaded eye needle. This swaging process was only applicable for larger diameter needles (greater than 0.36
1
20
20
mm), because the mechanical drill could not reliably cut uniform holes in the ends of smaller needles. Consequently, a forming tool was used to create a channel in one half of the diameter of these smaller diameter needles with an underlying receptacle for attachment of the suture. The linear slit in the wall of these small needles increased the drag force encountered by the needle during passage through a synthetic membrane [17]. With the advent of the laser (yttrium-aluminum-garnet [YAG] laser), uniform holes were reliably produced in the ends of small needles, resulting in a smooth swage that encountered lower drag forces than channel needles. The lower drag forces noted with taper point needle swages produced by the laser should be associated with less mechanical trauma to the tissue. For both laser-drilled and channel needies, the sutures were securely attached to the needles [18]. The suture needle attachment strength for the laserdrilled and channel needle did not differ significantly. The laser-drilled needles have other unique advantages over the channel needles, which were related to the depth of the holes in the needle ends. The length of the channel was four times longer than that of the laserdrilled hole. Because laser-drilled and channel swages are more susceptible to bending and breakage by the needle holder jaws than the body of the needle, surgeons are warned to grasp the needle with a needle holder at a site beyond the swage. In the case of 18-ram long taper point cardiovascular needles with laser-drilled and channel swages, the depths of the laser-drilled and channel holes were 1.5 mm and 6.0 mm, respectively. In these cases, the laser-drilled taper point needle can be held by the needle holder jaws 3 mm from the needle end, whereas the channel taper point needles must be grasped 7.5 mm from the needle end. By grasping the needle close to its end, the surgeon can more easily ma-
T H E A M E R I C A N J O U R N A L OF S U R G E R Y
V O L U M E 166
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527
EDLICH ET AL
I -C)-I
28.3 + 4.5
3O UJ =.J
0 91-
I
25
.~ 'E" ~_'~: u : ~ 20 ZE tu~
15
Z~
10
0
I PTFE(CV5) POLYPROPYLENE (3-0)
I,kl
HS POLYPROPYLENE(HSS) INFUSION PRESSURE= 80 mmHg
6.0 +1.1
5
NEEDLE/SUTURE RATIO
0.6 +.2 1.4
2.4
Figure 8. The needle suture products w h o s e n e e d l e : s u t u r e r a t i o approached 1 had the lowest fluid loss through the needle puncture sRe in the polytetrafluoroethylenegraft.
1.4
TABLE I
Biomechanical Properties of Needle Holders Clamping Force* Length
FF
LLt
Type
(in)
(N)
(cm)
(cm)
I_jt
Halsey Crile-Wood Microvascular DeBakey Mayo-Hegar
5 6 7 7 7
11.70 14.51 13.55 13.76 17.63
8.86 11.21 13.72 13.40 13.68
2.39 2,55 2.97 2.95 2.89
Mechanical
Advantagew 3.71 4.40 4.62 4.54 4.73
Width** (cm)
Applied Clamping Moment+ (N/cm)
0,20 0.23 0.17 0.21 0.27
2.17 3,67 2.66 3.28 5.63
*At first ratchet setting with a curved needle (0.58 mm wire diameter) 2 mm from jaw tip. 1Length of the handle from the fulcrum to the site at which force is applied to ringlets. SLength of the jaw from the fulcrum to the point at which jaw holds the needle 2 mm from the tip of the jaw. w **Two millimetersfrom needle jaw tip. +Clamping force • mechanical advantage • jaw width + length
nipulate the passage of the needle through tissue. This benefit of the laser-drilled needles was accomplished without altering the needle suture attachment strength. These distinct advantages of swages produced by lasers indicated that they should eventually replace all channel swage needles. Needle:suture ratio of 1:1: The introduction and wide acceptance of polytetrafluoroethylene (PTFE) grafts have focused considerable attention on the bleeding occurring during vascular anastomosis [19,20]. One of the characteristics of this material is that a needle hole placed in this graft remains approximately the same size as the needle. Needle-hole bleeding is due to the disparity between the diameter of the needle making the hole and the diameter of the suture filling it. Because the vascular surgical monofilament sutures currently in use have a needle:suture diameter ratio of approximately 2:1, the 528
THE AMERICAN JOURNAL OF SURGERY
difference between the sizes of the needles and sutures leaves an unfilled space at each suture hole, through which bleeding occurs. To resolvethis problem of bleeding through the holes in the P T F E grafts,two new cardiovascular suturesattached to taper point needles have been developed [21].One monofilament suture made of P T F E (W.L. Gore & Associates Inc.,Elkton, M D ) isproduced with a porous microstructure, which is approximately 50% air by volume. Its porous structure allows it to be swaged to a needle that closely approximates its suture diameter, having a needle-to-suturediameter ratio that approaches 1:1.The other suture,calledHemoscal (Ethicon, Inc.,Somerville,N J) suture,isa monofilament polypropylene suture that has been extruded to produce a tapered swage end, which is significantlysmaller than that of the remainder of the suture in order for it to be channel swaged to smaller diameter needles.
VOLUME 166
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SURGICAL NEEDLES AND NEEDLE HOLDERS
A dosed fluid system was developed to measure fluid jaw (w) width was measured using calipers at the needle leakage following penetration of a PTFE graft by differ- clamping site. The needle holder was then placed verticalent suture needle types. This closed system had four com- ly in a machinist's vise on top of a small compression load penents: (1) graft, (2) damp, (3) pressure transducer, cell. The ringlets of the needle holder were then comand (4) infusion pump. A 10-cm damped segment of pressed manually so that either the first, second, or third graft was attached to a pressure transducer using a medi- ratchet setting interlocked. The crosshead of the Instron trace disposable pressure monitoring product. An infu- Universal Tensile Tester was then lowered at 50 mm/min sion pump was incorporated through the pressure trans- until the force applied to the ringlets disengaged the interducer to introduce additional fluid that maintained a locking teeth, after which the movement of the crosshead constant system pressure of 80 mm Hg in the event that a was then stopped. As the direction of the crosshead was leak initiated a pressure loss. This system was tested with reversed, the force applied to the ringlet (FF) was record0.9% sodium chloride. Following a single suture passage ed until the teeth in the specified ratchet setting reeninto the graft, the rate of fluid loss around the suture was gaged. The maximal force encountered just before endetermined by measuring the rate of fluid infused to gagement of the interlocking teeth was judged to be the maintain a constant closed system pressure. This amount force required for engagement of the specified ratchet of infused fluid was always equivalent to the fluid leakage setting. This force influenced the applied clamping mofrom the graft. ment of the needle holder on the needle at the designated Although the diameters of the sutures were remark- ratchet setting. The measurement was repeated eight ably similar (Hemoseal and standard polypropylene di- times at the specified ratchet setting and at the measured ameter 0.23 mm and PTFE diameter 0.28 mm), the distance from the jaw tip using a new needle for each test. diameter of the standard needle (0.56 mm) was nearly The damping moment was calculated as previously detwo-fold wider than those of the Hemoseal (0.33 mm) scribed. and Gore (0.38 ram) needles. Consequently, the neeThe damping moment of the needle holder was didie:suture ratios of the Hemoseal and Gore products ap- rectly related to its mechanical advantage (LL/Lj), the proached one, whereas the standard needle:polypropy- damping force, and the jaw width at the site of the needle lene suture ratio exceeded two. The magnitude of the loss (Table I). The Halsey needle holder had the smallest of 0.9% sodium chloride from the needle puncture site damping moment, whereas the Mayo Hegar had the was proportional to the needle:suture ratio of the product greatest. The magnitude of the damping moment was (Figure 8). The loss of 0.9% sodium chloride from the significantly influenced by the size of the needle diameneedle puncture site was greatest with the standard prod- ter, the location of the needle between the needle holder uct whose needle:suture ratio was 2.4. When the Hemo- jaws, and the ratchet setting of the needle holder [6]. seal needle product with a 1.4 needle:suture ratio pene- When needle holder jaws clamped different diameter trated the graft, the needle puncture fluid loss from the needles at the site 2 mm from the jaw tip, the needle standard product was reduced by 79%. The needle punc- holder damping moments on the larger diameter needles ture fluid loss following needle puncture with the Gore- (0.58 mm) were significantly greater than those on the Tex needle suture product with a needle:suture ratio of smaller diameter needles (0.43 mm) (p <0.05). When the 1.4 was negligible. needle was advanced to sites 2 mm, 3 mm, and then 5 mm Atraumatie needle holder: Needle yield moment from the jaw tip, there were significant incremental inand needle holder clamping moment compatibility. Se- creases in the damping moments (p <0.05). Similarly, lecting the appropriate needle holder for a designated advancing the ratchet setting from the first, second, and needle can be accomplished by relating the damping third interlocking teeth resulted in significant increases in moment of the needle holder at the specified ratchet the jaw clamping moments (p <0.05). setting to the yield moment for the needle placed in a In Hgure 9, the clamping moments of seven different measured site in the needle holder jaws. Ideally, the sur- needle holders were related to the yield moments of cargeon should use a needle holder whose damping moment diovascular taper point (RB-1) and tapercut (V-5) neeis less than that of the yield moment of the needle. Clamp- dies manufactured by Ethicon Inc. [22]. The clamping ing a needle whose yield moment is greater than the moment of the needle holders were recorded at the first damping moment of the needle holder will result in re- ratchet setting with a 0.58-mm diameter PS2 needle posiversible deformation of the needle. When the clamping tioned 2 mm from the jaw tip. The diameters (0.66 mm) moment of the needle holder exceeds the needle yield of the cardiovascular needles were very similar to that of moment, damping the needle between the jaws of the the PS2 needle. Because the clamping moments of the needle holder will result in irreversible needle deforma- needle holders were less than the yield moments of the tion, with a subsequent enlargement of needle chord cardiovascular needles, these needle holders could be length. used at this ratchet setting without permanent needle The clamping moments exerted by needle holder jaws deformation. of six different needle holders (Snowden Pencer, Tucker, This compatibility between the needle holder dampGA) were recorded at specific ratchet settings. During ing moments and the yield moments of the cardiovascular measurements of damping moments, needles of varying needles was not encountered with the reverse and convendiameter (0.43 mm and 0.58 mm) were positioned at tional cutting edge needles whose diameters were 0.56 to spocified distances from the needle holder jaw tip. The 0.58 mm (Figure 10). Because the clamping moments of THE AMERICAN JOURNAL OF SURGERY
VOLUME 166
NOVEMBER 1993
529
EDLICH ET AL
CARDIOVASCULAR TAPERCUT(V-5) AND TAPERPOINT (RB-1) NEEDLES
/
7
V-5 7.0 4-"1.4
6 ,&
4-
31 4- ."1
3.3
--t---
4-."1
2i "1-
Halsey MA
Crile
Micro- DeBokey Mayo
Wood vascular
3.7"1
4.40
4.62
Hegar
4.54
4.73
NEEDLE HOLDER (First Ratchet Setting)
Figure 9. Relationship between the yield moments of 0.66-ram diameter cardiovascular taper point and tapercut needles and the clamping moments of needle holders at their first ratchet setting with the 0 . ~ diameter needle positioned 2 mm from the jaw tip.
CUTTING EDGE NEEDLES
liPs2 5.7•
[iiiiiiiiiii;iiiiiiiiiiiiii: iiiiiiiiiil ilili' ':2,:
PS4 4.9 • 0.9 ~7
3
0
i
U
I
1" 1
2.2 ___.1 Halsey MA
3.7"1
3.7 2.7 3.3 5.6 +.1 • _+..1 _+.1 Crile Micro- DeBakey Mayo Wood vascular Hegar 4.40
4.62
4.54
4.73
NEEDLE HOLDER (First Ratchet Setting) Figure 10. Relationship between the yield moments of 0.56- to 0.58-mm diameter conventional and reverse cutting edge needies and the clamping moments of needle holders at their first r a t ~ e t setting with the 0.58-rnm diameter needle positioned 2 m m from the jaw tip.
530
T H E A M E R I C A N J O U R N A L OF S U R G E R Y
the Halsey and microvascular needle holders were less than the yield moments of cutting edge needles, these needle holders could be used at the first ratchet setting with all cutting edge needles without permanent deformation. In contrast, the clamping moment of the Mayo Hegar needle holder exceeded the yield moments of the FS2, PS4, and PC5 PRIME needles, indicating that it will permanently deform these needles. Textured tungsten carbide jaw inserts. The design of the needle holder jaw is another important consideration in the selection of a needle holder. Tungsten carbide inserts with teeth, varying from 2,500 to 16,000 teeth/ inch2, have been incorporated into the jaws of the needle holder to enhance its needle holding security [23]. The presence of teeth within the needle holder jaws limits twisting and rotation of needle as compared with needle holder jaws without teeth. These teeth stabilize the needle, allowing the surgeon to accurately control the passage of the needle through the tissue. While appreciating the potential benefits of tungsten carbide jaw inserts with teeth in achieving needle holding security, the surgeon should also realize the potential deleterious effects of the teeth on suture materials and needles [24-26]. These teeth can produce distinct morphologic changes in monofilament synthetic sutures that markedly reduce their breaking strength [24]. The implications of this sutural damage on the strength of continuous monofilament synthetic suture in surgery are obvious. Finally, these teeth can alter the structural configuration of needles by producing stress concentrations, thereby reducing their resistance to either bending or breakage
[25,26]. Smooth needle holder jaws with rounded edges did not induce structural damage to either monofilament suture or needles [27]. However, their smooth jaw surface provided limited resistance to either the twisting or rotation of the needle between the jaws. A textured needle holder jaw metallurgicaUy bonded with tungsten carbide particles appears to be an attractive alternative to either smooth needle holder jaws or those with teeth [27]. Although its needle holding security was significantly less than the jaws with teeth, it provided greater needle holding security than the smooth jaws. By enhancing the average surface roughness of the jaw, the embedded tungsten carbide particles of the textured jaw surface resisted twisting and rotational moments of the needle. Unlike the sutural damage inflicted by the jaws with teeth, compression of the synthetic monofilament suture by either the smooth jaws or textured jaws with tungsten carbide particles did not weaken the monofilament suture. Rounded jaw edges. Recent studies demonstrated that the sharp outer edges of smooth needle jaws cut the smooth surface of monofilament sutures, weakening its strength [28]. When the smooth tungsten carbide inserts of needle holders clamped 6-0 monofilament nylon suture with the first opposing teeth of the needle holder ratchet mechanism interlocked, there was a significant reduction in suture breaking strength. This sutural damage can be prevented by mechanical grinding the outer edges of the
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SURGICALNEEDLES AND NEEDLE HOLDERS
smooth tungsten carbide inserts, resulting in a rounded edge. Clamping the suture with the smooth jaws of the needle holder with rounded edges was atraumatic, with no demonstrable damage to the suture's breaking strength. Another approach to enhance the needle holding security was tochange the configuration of the needle body to allow the needle holder to hold it more securely [23]. However, changes in the configuration of the needle body were considerably less important than either the presence of teeth in the tungsten carbide jaw inserts or advancement of the engagement of the ratchet setting of the needle holder. In addition, the presence of longitudinal ridges on the concave or convex surface of the needle or on both surfaces did not decrease undesirable twisting or rotational movements of the needle. FUTURE During the last two decades, standard, reproducible tests have been devised that determine the biomechanical performance of surgical needle and needle holders. These tests can ensure quality control of the manufactured products as well as provide a frame of reference for the development of new, improved products. The need for reliable quality control standards is especially apparent in the manufacturing of surgical needle holders. Because the vast majority of needle holders are manufactured by companies in Germany and Pakistan, it has been difficult to institute reliable quality control programs. Today, the biomechanical performance of needle holders has an unacceptably large degree of variability [29,30]. This resistance to quality control standards by the manufacturers is associated with an indifference to the development of innovative products. With the advent of new surgical techniques, there is an urgent need for development of lighter-weight needle holders that are atraumatic to sutures and needles [31]. Fortunately, American-owned companies manufacture most of the surgical needles used in the world. The quality control of the manufactured needle products is superior. It is also gratifying that these companies are not resting on their laurels and are designing new needle products for the 21st century. New alloys are being developed that have a greater resistance to bending and breakage than the $45500 stainless steel. New coatings for needles are being devised that will eventually replace the silicone coating. New attention is being paid to packaging systems for needles, which ensure that their delicate points are protected from damage. CONCLUSION During the last two decades, seven major advances in surgical needle and needle holder technology have markedly improved surgical wound repair. These advances include quantitative tests for surgical needle and ne~ile holder performance, high nickel maraging stainless steels, compound curve needle, needle sharpening methods, laser-drilled holes for swages, needle:suture ratios of 1:1, and the atraumatic needle holder. The quantitative tests for surgical needle and needle holder performance
are measurements of needle sharpness, needle resistance to bending, needle ductility, and needle holder clamping moment. New needle sharpening methods involve dectrohoning, narrowing needle point configuration, reducing cutting edge angles, and silicone coating. The atraumatic needle holder has been achieved by ensuring needle yield moment and needle holder clamping moment compatibility, and developing textured tungsten carbide jaw inserts and rounded needle holder jaw edges. These advances in surgical needle and needle holder technology provide a scientific basis for selecting surgical needle and needle holders as well as insight into future technologic advances that are on the horizon. REFERENCES 1. Van Winkle W Jr, Hastings JC. Considerations in the choice of suture materials for various tissues. Surg Gynecol Obstet 1972; 135: 113-26. 2. Trier WC. Considerations in the choice of surgical needles. Surg Gynecol Obstet 1979; 149: 84-94. 3. Thacker JG, Rodeheavcr GT, Towler MA, Edlich RF. Surgical needle sharpness. Am J Surg 1989; 157: 334-9. 4. Abidin MR, Towler MA, Rodeheavcr GT, Thacker JG, Cantrell RW, Edlich RF. Biomechanicsof curved surgical needle bending. J Biomater Res 1989; 23: 129-43. 5. Abidin MR, Towler MA, Nochimson GD, Rodcheaver GT, Thacker JG, Edlich RF. A new quantitative measurement for surgical needle ductility. Ann Emerg Med 1989; 18: 64-8. 6. Edlich RF, Towler MA, Rodeheaver GT, Becker DG, Lornbardi SA, Thacker JG. Scientific basis for selecting surgical needles and needle holders for wound closure. Clin Plast Surg 1990; 17: 583-602. 7. Ayer R, Bendel LP, Zackay VP. Metastable precipitate in a duplex martensite ferrite precipitation-hardening stainless steel. Metallurgical Trans A 1992; 23A: 1-7. 8. Abidin MR, Becker DG, Paley RD, et al. A new compound curved needle for intradermal suture closure. J Emerg Med 1989; 7: 441-4. 9. Edlich RF, Zimmer CA, Morgan RF, et al. A new compoundcarved needle for microvascular surgery. Ann Plast Surg 1991; 27: 339-44. 10. Tribble CG, Moody FP, Girard P, et al. A new, compound carved needle for vascular surgery. Am Surg 1992; 58: 458-62. l l . Hoard MA, Franz DA, Bellian KT, Edlich RF. A new compound curved tapcrcat needle for oral surgery. J Oral Maxillofac Surg 1992; 50: 484-9. 12. Cook TS, Towler MA, Girard P, McGregor W, Dcvlin PM, Edlich RF. A new compound curved needle for skin and skin graft suture closure. J Burn Care Rehab 1992; 13: 650-5. 13. Towler MA, McGregor W, Rodcheaver GT, et al. Influence of catting edge configuration on surgical needle penetration forces. J Emerg Med 1988; 6: 475-81. 14. Kaulbach HC, Towler MA, McClelland WA, et al. A beveled, conventional cutting edge surgical needle: a new innovation in wound closure. J Emerg Med 1990; 8: 253-60. 15. McClung WL, Thacker JG, Edlich RF, Allen RC, Rodeheaver GT. Biomechanical performance of ophthalmic surgical needles. Ophthalmology 1992; 99: 232-7. 16. Minahan PR. Eyeless needle. United States Patent Office. No. 1,106,667, Aug. 11, 1914. 17. Tow|er MA, Clapp CG, McGregor W, Morgan RF, Edlich RF. Laser-drilled cardiovascular surgical needles. J Appl Biomater 1991; 2: 183-6. 18. Ahn LC, Towler MA, McGregor W, Thacker JG, Morgan RF,
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EDLICH ET AL
Edlich RF. Biomechanical performance of laser-drilled and channel taper point needles. J Emerg Med 1992; 10: 601-6. 19. Miller CM, Sangiolo P, Jacobson JH II. Reduced anastomotic bleeding using new sutures with a needle-suture diameter ratio of one. Surgery 1987; 101: 156-60. 20. Garcia-Rinaldi R, Revuelta JM, Poeppel R, Treager K, Black D, Kirby JM. Clinical experience with expanded polytetrafluoroethylene suture. Bol Asoc Med P R 1986; 78: 335-8. 21. Towler MA, Tribble CG, Pavlovich LJ, Milam JT, Morgan RF, Edlich RF. Biomechanical performance of new vascular sutures and needles for use in polytetrafluoroethylenegrafts. J Biomat Res 1993; 4: 87-95. 2 2 . Bellian KT, Thacker JG, Tribble CG, et al. Biomechanical performance of tapercut cardiovascular needles.Am Surg 1991; 57: 591-601. 23. Thacker JG, Borzelleca DC, Hunter JC, McGregor W, Rodehearer GT, Edlich RF. Biomechanical analysis of needle holding security. J Biomed Mater Res 1986; 20: 903-17. 24,. Stamp CV, McGregor W, Rodeheaver GT, Thacker JG, Towler MA, Edlich RF. Surgical needle holder damage to sutures.
532
Am Surg 1988; 54: 300-6. 25. Abidin MR, Thacker JG, Lombardi SA, et al. Needle holder damage to surgical needles. Am Surg 1989; 55: 681-4. 26. Bond RF, McGregor W, Cutler PV, Becket DG, Thacker JG, Edlich RF. Influence of needle holder jaw configuration on curved surgical needle bending. J Biomed Mater Res 1990; 1: 39-47. 27. Abidin MR, Dunlap JA, Towler MA, et al. Metallurgically bonded needle holder jaws. A technique to enhance needle holding security without sutural damage. Am Surg 1990; 56: 643-7. 28. Abidin MR, Towler MA, Thacker JG, Nochimson GD, McGregor W, Edlich RF. New atraumatic rounded-edge surgical needle holder jaws. Am J Surg 1989; 157: 241-2. 29. Chen NC, Towler MA, Moody RF, et al. Mechanical performance of surgical needle holders. J Emerg Med 1991; 9: 5-13. 30. Francis Eli III, Towler MA, Moody RP, et al. Mechanical performance of disposable surgical needle holders. J Emerg Med 1992; 10: 63-70. 31. Towler MA, Chen NC, Moody FP, et al. Biomechanics of a new atraumatic surgical needle holder. J Emerg Med 1991; 9: 477-86.
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