Review

Suture Materials, 1980s: Properties, Uses,and Abuses

NEIL A. SWANSON, M.D. AND THEODORE A. TROMOVITCH, M.D.

Throughout antiquity many materials have been usedto approximate wounds. As early as 5000-3000 B.C.E.,eyed needles were used to pass suture material throughsurgical wounds. By 2000 B.C.E. boned needles beganusage in a fashion unsurpassed until Renaissance times.Materials connected to these needles included flax,hemp, fascia, hair, linen strips, pig's bristles, reeds, gras-ses, and other exotic materials available. Tying of locksof scalp hair into knots to close scalp wounds was com-mon djring battles and is still employed as a temporarymeasure in some busy emergency rooms.

Perhaps the most legendary wound closure was theuse of the mouth parts of the pincher ant. In all, naturalproducts alone sufficed as suture material until the1940s. These included silk, cotton, linen-cotton, andcatgut. During this decade, nylon and dacron becamethe first synthetic materials made into suture. Later,polyethylene, polypropylene, polyglycolic acid, andpolyglycan 910 were developed and added to the sur-geon's armamentarium. For years, the surgeon had nochoice but to use silk and catgut to close wounds.

With the advent of modern suture material, oneshould become familiar with the different characteristicsof each so that he may best use the most appropriateproduct. The qualities of the ideal suture material havebeen bantered for years. Characteristics of such a suturematerial include superior tensile strength, good knot se-curity, excellent handling characteristics, minimal,nonallergenic tissue reaction, resistance to infection,and eventual absorption (of absorbable suture products)when tissue repair has reached satisfactory levels. Unfor-tunately, there is no ideal suture material.

The U.S. Pharmacopeia divides sutures into twogroups, the ahsorhable and the nonabsorhahle. In gen-eral, absorbable sutures lose tensile strength in less than60 days; nonabsorbable sutures maintain tensile strength

AcJdress for reprints: Neil A. Swanson, M.D., C-2074 OutpatientBuildint; University of Michigan Medical School, Ann Arbor, Ml48109.

from the Department of Dermatology,University of Michigan Medical School,

Ann Arbor, Michiganand the Department of Dermatology,

University of California Medical School at San Francisco,San Francisco. California

for greater than 60 days. Tables 1 and 2 list several dif-ferent sutures available in each category which are ofimportance to the dermatologic surgeon. The tablefurther summarizes the important physical characteris-tics each suture possesses.

Properties of Suture Material'-^

Knot security refers to the ability of the suture to main-tain knot strength without slippage. It is important to tiecareful square knots to impart a fair test of knot security.Knot security is inversely proportional to the memory ofthe suture material, and directly proportional to theworkahility of the suture material. Sutures of high mem-ory are less pliable, maintain their original shape, andcan be more difficult with which to work. Knot securitycan be improved by an extra tie when securing a surgicalknot. Examples of sutures with good memory aremonofilament nylon and polypropylene.

Tensile strength^ is used for both suture material andtissue. It refers to the strength per unit area of tissue orsuture. Breaking strength, on the other hand, involves ameasurement of strength for unit width and differs fromtensile strength. Skin and fascia are tissues of greatesttensile strength, a quality which experimentally in-creases with age. Theoretically, therefore, suture mate-rial need not have greater tensile strength than the wouldbeing closed.

Tissue reactivity^ has become increasingly importantin considering suture material. Biopsy material fromwounds after suture implantation has revealed a markedand peaked tissue reaction and two to seven days after

0011-9059/82/0900/0373/$01.10 © International Society ol Tropical Dermatology, Inc.

373

374 INTERNATIONAL lOURNAL OF DERMATOLOCY Septemi>er 1982 Vol. 21

TABLE 1. The Ab^orhable Sutures

TypeKnot

SecurityTensileStrength

WoundSecurity (%)

TissueReaction

GutChromicDexon*Vicrylt

+ ++ +

+ + + +

5- 7 da (50%)10-14 da (50%)

25 da (50%]30 da (50%]

Polyglycolfc acid.Polyglyccin 910.

implantation. This occurs to some degree with all suturesstudied. The information is characterized in the first fourdays by polymorphonuclear leukocytes, lymphocytes,and monocytes. By the fourth day, mononuclear cells,macrophages, and fibroblasts predominate. After theseventh day, fibrous tissue with chronic inflammationpersists. The inflammation is universally present forseven days for all suture products. It then decreases formost nonasorbable sutures, with the monofilament su-tures, especially polypropylene, exhibiting the leastreactivity. The absorbable sutures, however, differ intheir reactivity. Plain catgut maintains an intense reac-tion until the suture is absorbed, with chromic gut beingslightly less reactive. Synthetic polyglycolic acid (PGA)and polyglycan are much less reactive.

Wound security refers to the strength the suture im-parts to the wound overtime. It is a reflection not only ofwound healing, but of the tensile strength, know se-curity, and other characteristics of the suture material.For the absorbable suture, it is a reflection of their less oftensile strength over time. Wound security, therefore, isdependent on both original tensile strength and rate ofabsorption. Therefore, although some studies show thatPGA is absorbed more rapidly than chromic gut, theoriginal tensile strength of PGA Is much greater thanchromic catgut, thus imparting a much greater woundsecurity to PGA.

Absorbable SuturesCatgut^ (plain gut) is made from sheep intima and has

historically been the longest available and best-knownsuture; however, its use today is declining. Catgut main-tains significant tensile strength for approximately four tofive days. Wound security is essentially gone in 14 days.It also exerts the greatest amount of tissue reaction of allthe absorbable sutures. Therefore, to place catgut suturesother than for hemostasis in a wound where the skinsutures are going to be removed in a week to 14 daysdoes not make mechanical sense. It is, in a sense, intro-ducing a foreign body which will not add to the strengthofthe wound once the skin suture has been removed. Itcan be used on a surface such as the mucosa whichheals rapidly and advantage taken of its rapidabsorption.

Chromic gut^-^ is historically almost as old as catgut. Itis catgut which has been treated by exposure to variouschromic salts in an attempt to retard absorption in tissue.It has better wound security In that its absorption issomewhat delayed compared with catgut. Some studieshave shown that its rate of degradation in tissue is slowerthan some of the modern absorbable sutures; its tensilestrength is much less. It only maintains wound securityfor about 14 days. After this, wound security markedlydiminishes and it is more useful than catgut in woundapproximation. Where true wound security is an issue, it

TABLE 2. The Nonabsorbable Sutures

Type

Silk

Mersilene*NurolontNylonProleneiEthibond§

KnotSecurity

4- + + 4-+ + + +

+ + +4-4-

-1-

+ + +

TensileStrength

+4-4-

4-4-4--H 4-

4-4-4-4-+ + + +

WoundSecurity

+4^-1-4-

+ +4-4-4-

-H 4- -H4-

+ + + +

TissueReaction

4-4 -4 -4 -

4- + 4-

+ 4- ++ +

+ + ( + ]

Workability

+ + + +-H'4--t-4-

+ ++

Multifilament dacron.Braided monofilament nylon.Polypropylene.Coated braided polyester.

No. 7 SUTURE MATERIALS Swanson and Tromovitch 375

still is inferior to more modern suture materials. It alsoimparts a good deal of tissue reaction.

There is one chromic gut suture, manufactured byDavis and Geek, called "mild ophthalmic chromic gut"which has somewhat less reaction in tissue but is ab-sorbs too rapidly for routine use. It is available in a small(6/0) size, which can be used as an external skin suturein a special way for the suturing of grafts and blephro-plasties in delicate areas where suture removal wouldpresent a problem. If the suture line is covered with apiece of tape, the mild ophthalmic usually absorbswithin a week, so that removing the tape at that timegenerally removes all the suture at the same time. Thishas been observed only for Davis and Geek's mildophthalmic chromic and not for the other types of mildchrom c. Except for the special uses discussed for bothcatgut and chromic gut suture, they probably should bereplaced by more modern materials.

Vicryi®^-^-'* (polyglycan 910) is a synthetic polymer.Prepared by the copolarization of a mixture of lactideand glycolide. A catalyst, a colorant (if the suture isdyed) and a chemical regulator, are also present in thereaction. The polymer which is formed is then meltedand extruded into fine fibers. These fibers are thenbraided into sutures making this a synthetic braided su-ture. The braiding provides better handling properties.The synthetic fiber is available in both dyed and clearsutures. The dye is used primarily to enhance suturevisibility. The suture possesses an extremely high tensilestrength and maintains 50% of that tensile strength forapproximately thirty days. It requires 90 to 120 days forcomplete dissolution. Its removal is accomplished byhydrolysis without significant phagocytosis. This sup-posedly causes less tissue inflammatory response thangut su;ures. Vicryl has less knot security, so that theplacing of knots must be more accurate. Vicryl biologi-cally makes more sense in a wound which will requiretensile strength subcutaneously during healing, since thesutures maintain strength for the four to six-week periodof collagen formation in the healing process.

Dexon®^-**"^" (polyglycolic acid) represents anotherof the modern absorbable sutures. Polyglycolic acid is ahigh molecular, linear copolymer of glycolic acid. It isextruded into thin filaments and braided into sutures inmuch the same way as other synthetic fibers. It possessesmany of the same qualities as Vicryl. Its knotting charac-teristics are very similar. It is said that knot security withDexon is 1.4 times greater than chromic catgut and twotimes greater than catgut.^ It has an extremely hightensile strength and maintains 50% of tensile strength intissue for 25 days. Again, all ofthe suture material gen-erally is totally removed in 90 to 120 days. It also pro-vides a very low tissue reactivity compared to catgutsuture^. It is dissolved by autolytic action in the tissuesand does not involve phagocytosis. A problem with

Dexon has been that the braided suture has a tendencyto "hang up" when attempting to tie knots. The loop onan instrument tie will sometimes lock on the braidedstructure so that the knot cannot be set exactly wheredesired. In 1978, a new Dexon was introduced com-posed of smaller multifilament strands in a tighter weaveand this has compensated somewhat for this problem.Dexon and Vicryl sutures have now basically replacedthe routine use of catgut sutures in dermatoiogic surgery.

Coated Vicryl® is a new suture which is essentiallyVicryl with a Teflon® coating. It has the advantage ofmuch easier slippage through tissue without the braidedstrands getting caught in wound margins. Its knots also tiemore easily and the suture has less memory, thus makingit easier to handle. The knots, however, do have more ofa tendency to slip and must be placed accurately.

Nonabsorbable '^" '̂

Silk has been a mainstay suture material for years. Itpossesses an extremely adequate workability and knotsecurity. It has very little memory, enabling these qual-ities to be apparent. It does, however, induce most tissuereactions of any nonabsorbable sutures, it imparts theleast tensile strength of the nonabsorable sutures, losing50% of the strength in one year, and all of its tensilestrength by the end of two years. It still is a suture used inkey locations with great benefit. Its lack of memory and,therefore, good workability make it useful around theeye, mouth, and orifices. It also can be used on the solesof feet where pressure is being placed.

Mersilene (dacron-polyester) is a braided synthetic su-ture. Its braided construction offers tying ease, workabil-ity, and knot security similar to those of silk. It is presentin both dyed and undyed materials which makes its usebeneficial for certain areas. It causes less tissue reactionthan silk. It can be used in the same areas where silk canbe used because of its lack of memory. It has extremelyhigh tensile strength and remains in tissue for more thantwo years.

Neurolon (braided nylon) consists of fine nylonbraided again in an attempt to give tying characteristicscloser to those of silk, while retaining the low reactivityof nylon. Surgeons who prefer nylon sutures will find thissuture beneficial in areas where lack of memory andeasy tying characteristics are of benefit. Its tensilestrength is very similar to nylon, and it also can remain intissue for more than two years. Its tensile strength, how-ever, is less than the tensile strength of polypropylene.

Nylon is a monofilament extruded nylon syntheticmaterial. It has a good deal of memory, thus, know se-curity can be a problem if care is not taken in a propersurgical tie. It has a great deal of tensile strength andprovides very adequate wound security for skin. It hasmuch less tissue reaction making it a valuable suture for

376 INTERNATIONAL JOURNAL OF DERMATOLOGY September 1982 Vol. 21

routine use. Monofilament sutures have several advan-tages over braided sutures. The synthetic monofilamentsutures offer the advantage of decreased wound infec-tion compared to braided suture. They also can be usedmore safely than braided sutures in contaminatedwounds. This, coupled with their high tensile strengthand low tissue reactivity, make them an excellentcutaneous suture. They can offer more aggravation dur-ing the surgical procedure because of their increasedmemory. The first throw that is placed has a tendency toslip, and this must be accounted for when performingthe surgical closure so as not to apply too much pressureto the wound edges.

Prolene (polypropylene) is a monofilament suture ofmore recent development. It has extremely low tissuereactivity which is better than nylon. It has slightly morememory than monofilament nylon. However, it has thegreatest tensile strength and the best resistance to infec-tion, a5 shown in several studies. It is manufactured in aclear and a blue suture, this making it easily visible. Theknot security with both prolene and the other monofil-ament sutures can be improved by adding an extra sur-gical throw at the time of wound closure.

Ethibond (braided, coated polyester) is the newest andmost costly suture for skin surgery. It possesses a lowtissue reactivity, passes through tissue easily, and hasless memory than monofilament sutures so that its work-ability and know security increases. As with monofila-ment sutures, there is a low incidence of infection.Therefore, other than its cost, this is an excellent suturefor the dermatologic surgeon.

Surgical Needles

Modern cutaneous surgery does not warrant the use ofneedles which require threading, produce large holes,and require the passage of a double layer of suturethrough the wound. Modern suture material is swedged

onto the needle to provide for a smaller diameter needleas well as one diameter of suture having to be pulledthrough tissue.

Various types of tips on needles are available. Theseare illustrated in Figure 1. In almost all cases of cutane-ous surgery today, the reverse cutting needle is pre-ferred. The needle tip has a cutting edge on the outsideof the curve. It actually makes a small cut in the tissue toallow smooth passage of needle and suture. Since thecut is made in the direction opposite to the wound edge,the suture does not tear through tissue as sometimeshappens with conventional cutting needles with the cut-ting surface on the inside of the curve. Precision pointneedles (Fig. 1) offer the highest degree of honing of thesteel and points which are reported to maintain sharp-ness for a longer period of time.

Needle nomenclature has evolved in a haphazardway without long-term planning. The surgeon must learnthrough experience which needles he prefers and theterminology of the manufacturer of the needle. In ourexperience, the needles manufactured by Ethlcon Cor-poration have superior sharpness and are particularlyable to maintain their sharpness. We, therefore, arefamiliar with their nomenclature. With the Ethicon no-menclature, the two series of needles used are F seriesand the P series. The FS code denotes "for skin," the PSneedle (-) "plastic skin," and the P needle (-) "plastic."The FS and PS needles are 3/16 of a circle. The former isthe least expensive needle and is used for most non-cosmetic surgery. The PS needles are made of bettersteel and honed to a higher degree. The P-series needlesare a semicircle, small that the PS series, and representthe least tissue drag. The P-series needles, because oftheir increased honing and better quality of steel, areused for most cosmetic work. However, the P and PSseries cost approximately three times as much as the FSseries. Therefore, the economics of the choice of sutureand needle becomes important.

BODY

COhfVENTIONAL CUTTINGTwo opposing cutting edges,with a third on inside curve.Change in cross-section froma triangular cutting tipto a flattened body.

REVERSE CUTTINGCutting edge onouter curve.For tough, difficult*to-penetrate tissues.

BODY BODY

PRECISION POINTFor delicate plastic orcosmetic surgery. Cutting tip,honed 24 extra times.

FIG. 1. Various types of tips on needles used for sutures.

No. 7 SUTURE MATERIALS Swanson and Tromovitch 377

Wound Management ̂ -̂̂ ^

A basic consideration ofthe biology of wound healingis important in suture selection. In essence, wound heal-ing can be delineated into three phases: (1) the lag phasefrom day 0 today 5; (2} the phase of fibroplasia from day5 to day 14; and (3) the phase of maturation from day 14until wound healing is complete. During the first phase,the wound depends upon sutures to maintain closureand strength. The phase of fibroplasia is a time when arapid gain in wound strength takes place; however, skinapproximation is equally important. Skin approximationusually is complete when maturation begins. This is aphase of connective tissue remodeling and molding. Itlasts fn^m four to six weeks. Nature then remolds thewound for approximately eighteen months. Studies havepinpointed that there Is increased collagen production ina wound up to day 42. There probably is no clear dis-tinction between the phases of fibroplasia and matura-tion as they represent a continuum. In general, woundstrength continues to increase for the ensuing year. Ex-perimental studies of skin wounds have shown that al-though wounds gain strength at relatively early post-wound time, they have not yet regained the strength ofnormal skin. Therefore, it is obvious that some form ofwound support is necessary for a much longer period oftime than was originally thought. If collagen productioncontinues into the sixth week, then the use ofthe newerabsorb..ible sutures which maintain tensile strength forclose to that period of time should provide improvedresuits. Wound taping and other measures of aidingwound support can also be beneficial.

The choice of suture in a surgical wound, therefore,depends on several factors. Wound healing, as alreadymentioned, plays an imfjortant role. The cleanness (lackol infection) plays a role, as monofilament sutures arebetter tolerated in a contaminated wound than braidedsutures. The anatomic locition ofthe wound is also im-portanl. For most dermatoiogic surgery on areas notaround orifices and eyelids, monofilament sutures areperfectly acceptable. However, their memory and rigid-ity can be a nuisance around eyelids and orifices andareas where pressure is placed on the ends of the suture.Suture size also is an important variable. The size listingson suture range trom 0 through 8/0 in sutures used bythe dermatoiogic surgeon. The 8/0 suture is the finest.One should also note that size is dependent on a specificdiameter to produce a sufficient tensile strength. There-fore, the diameters of suture for the same size suture willvary. For example, a 5/0 silk suture will be greater indiameter than a 5/0 prolene suture. In general the smal-ler sutures (5/0, 6/0) are used for cosmetic areas and onthe face where the tissue is under the least amount of ten-sion, the 3/0 and 4/0 sutures are used on the torso of the

body where the wound is under greater stress. The verystrong sutures are used in special circumstances, such asthe approximation of galea in scalp reduction. The espe-cially fine sutures (7/0, 8/0) are used for cosmetic pro-cedures performed around eyelids such as blepharoplas-ties and skin grafts.

Suture removal is another important consideration.Generally, the least amount of time the suture is left inplace, the better the cosmetic result. This is also relatedto the tightness of the suture. Wound edges should belightly kissed in an everted manner for best tissue ap-proximation. Tying the suture too tight can inhibit thisprocess. Face sutures usually are removed in three to fivedays. On the neck and other areas under more tension,the sutures are removed five to seven days. On the torso,specifically the back and areas affected by a great deal ofmotion, the suture is often left in place for two weeks ormore. The type of wound closure can also affect the timeof suture removal. For example, a wound closed with arunning subcuticular stitch can have that stitch left inplace for <i much longer period of time than a woundclosed with interrupted and/or mattress stitches.

We favor the use of monofilament sutures for woundapproximation in most instances. This is because of theirhigh tensile strength, low tissue reactivity, and lesser in-cidence of infection.

Staples'"^

Staples have been commonly used tor years to closeskin following thyroid surgery. Hunt,'^ in his classicbook on wound healing, states that staples give one ofthe best experimental wound closures available. Theyare finding increasing use in general surgery as a skinclosure. Stapling is a fast and effective method to closemany skin wounds. Staples can be used to hasten skingrafting and the closure of long linear wounds. There aretwo commonly used staplers.

The Autosuture® is a nondisposable apparatus whichis made in both stainless steel and plastic models. Theyboth are autoclavable. A disposable cartridge is avail-able in two widths of staples which is inserted just prior touse. It has a trigger pull mechanism to insert the staple,and a tip which can be turned 360 degrees to facilitatestaple insertion. Disposal staple removers are availablefor staple extraction.

The Proximate® disposable skin stapler is a new ap-paratus manufactured by Ethicon. It is made predomi-nantly of plastic and contains either 15 or 35 stainlesssteel staples which are approximately 5.7 mm in width.This whole unit is disposable. It can be used easily forlinear incisions, but because the head does not rotate, itcan be difficult to use in hard-to-reach locations.

378 INTERNATIONAL JOURNAL OF DERMATOLOGY September 1982 Vol. 21

Summary

The development of modern suture material offers thedermatologic surgeon an important choice in would clo-sure. This review, although prejudiced in some instancesby the author's experience, likes, and dislikes, is an at-tempt to clarify the difference between various absorb-able and nonabsorbable sutures. Properties of suturematerial are discussed in detail. Guidelines for choice inregard to wound healing, location of incision, and surgi-cal needles are offered. Lastly, the use of staples inwound closure is mentioned.

References

1. Van Winkle W, Hastings )C: Considerations in the choice of su-ture material for various tissues. Surg Gynecol Obstet 1 J5:11.3,1972

2. Van Winkle W, Salthouse TN: Biological response to sutures andprinciples of suture selection, scientific exhibit; Americ^in Col-lege Surgeons, 1975 Clinical Congress, S.F.

3. Aston S|: Thechoiceof suture material for skin closure. J DermatolSurg Oncol 2:57, 1976

4. Herrmann |B; Changes in tensile strength and knot security ofsurgical sutures in vivo. Arch Surg 106:707, 1973

5. Postlethwait RW, Willigan DA, Ulin AW: Human reaction to su-tures. Ann Surg 181:144, 1975

6. Howes EC: Strength studies of polyglycolic acid versus catgutsutures of the same size. Surg Obstet Gynecol 137:18, 1973

7. Horton CE, Adamson JE, Mladick RA, et al: Vicryl® syntheticabsorbable sutures. Am 5urg 40:729, 1974

8. Craig PH, Williams |A, Davis KW, et dl: A biologic comparison ofpolyglactin 910 and polyglycolic acid synthetic abosrbable su-tures. Surg Gynecol Obstet 141:1, 1975

9. Katz AR, Turner JR: Evaluation of tensile strength and absorptionproperties of polyglycolic acid sutures, Surg Gynecol Obstet701, 1970

10. Herrmann JB, Kelley R), Higgins GA: Polyglycolic acid sutures.Arch Surg 100:486, 1970

11. Postlethwait KW: Long term comparative study of nonabsorbablesutures. Ann Surg 1 71:892, 1970

12. Hunt TK, Dunphy |E: Fundamentals of Wound Management, NewYork Appleton-Century-Crofts, 1979

13. SatoRM, TebbettsJB, Saarex A|, et al: Staples: Their use in achiev-ing biological coverage of burn patients. Burns 6:482, 1950

14. Swanson NA, Tromovitch TA, Stegman 5J, et al: The split thick-ness skin gralt, 1980. J Dermatol Surg Oncol 6:524, 1980

"Alex . . . Through the Looking Glass," Mr^. Norman Goldstein. Fromthe 1981 art exhibit of the American Academy of Dermatology, SanFrancisco, CA. Photograph courtesy of Hoechst-Roussel Pharmaceuti-cals, Inc.