fios de sutura no mercado

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IITTE W RTHEINEMANN

Biomoterids 16 (1995) 1141-11480 1995 Elsevier Science Limited

Printed in Great Britain. All rights reserved014%9612/95/$10.00

Monocryl@ suture, a new ultra-pliableabsorbable monofilament sutureRao S. Bezwada, Dennis D. Jamiolkowski, In-Young Lee, VishvaroopAgarwal, Joseph Persivale, Susan Trenka-Benthin, Modesto Emeta,Jogendra Suryadevara, Alan Yang and Sylvia LiuResearch and Development Division, Ethicon, Inc., P.O. Box 151, Somerville, NJ 08876-0151, USA

Synthetic absorbable sutures are available as braided constructions or as monofilaments. Braidedabsorbable sutures are made either from 9O:lO poly(glycolide-co-L(-)-lactide), sold by Ethicon, Inc.under the trade name Vicryl@, or from polyglycolide, as sold, for instance, by Davis and Geck underthe trade name Dexon@. There are, however, some concerns with braided sutures that relate to tissuedrag and the trauma this may cause, as well as the possible potentiation of infection through theinterstices of the braid structure. Absorbable monofilaments, such as the monofilament suturesderived from p-dioxanone homopolymer (PDS IIa, an Ethicon, Inc. product), or a copolymer oftrimethylene carbonate and glycolide (Maxor?, a Davis and Geck product), eliminate many of theseconcerns, but generally monofilaments do not handle as well as braids. This paper describes theresearch leading to the introduction of Monocryl (poliglecaprone 25) monofilament sutures, based onsegmented block copolymers of &-caprolactone and glycolide. Monocryl sutures will be shown todisplay excellent handling properties, minimal resistance during passage through tissue and excellenttensile properties. These sutures provide an in vivo breaking strength retention of approximately 20-30% after 2 weeks, considered by many to be the critical wound healing period. Absorption data onthese sutures are presented; absorption is complete between the 91st and 119th days of implantation,with slight or minimal tissue reaction.Keywords: Sutures, absorbable sutures, synthetic absorbable sutures, monofilamentReceived1 July 1994; accepted 26 January 1995

Synthetic absorbable sutures are available as braidedconstructions or as monofilaments. Braided absorbablesutures are made either from polyglactin-910, a 90:lOcopolymer of glycolide and lactide, sold by Ethicon,Inc. under the trade name Vicryl, or from polyglycolide,sold, for instance, by Davis and Geck under the tradename Dexon. Except for fine sizes, the monofilamentsderived from these polymer systems are relatively stiffand, thus, mainly braided sutures are produced frompolyglactin-910 and its variants. There are, however,some concerns with braided sutures that relate totissue drag and the trauma this may cause.Consequently, braided sutures are generally coated tohelp minimize tissue drag. Other concerns withbraided sutures include the possible potentiation ofinfection through the interstices of the braid structure.To eliminate some of the concerns of braided sutures,absorbable monofilament sutures, PDS II (a homopoly-mer of p-dioxanone; an Ethicon, Inc. product) andMaxon [a copolymer of trimethylene carbonate andglycolide; a Davis and Geck product) have beenintroduced2*3. Even though some advances have beenmade with these monofilaments, generally speaking,Correspondence to Dr R.!3. Bezwada.

monofilaments do not handle as well as braids andfurther improvements in handling and packagememory are desired.Although the natural absorbable suture, catgut, is stillbeing used, it has several drawbacks, including lowtensile strength and significant tissue reaction duringthe critical wound healing period. The latter causesnon-uniform surgical performance. In order toovercome these shortcomings, a major researchprogramme was initiated which led to the developmentof Monocryl (poliglecaprone 251, the most pliablesynthetic absoibable monofilament suture marketed.These monofilaments are derived from a segmentedcopolymer of &-caprolactone and glycolide4. Thiscomplex polymeric system contains soft segments of arandom copolymer of &-caprolactone and glycolidewhich provide good handling characteristics, and hardsegments of polyglycolide which provide highstrength. The hard and soft segments are combined inthe same polymeric chain in such a way so as to leadto the unique properties of Monocryl.In this study, the in vivo characteristics of breakingstrength retention, absorption, tissue reaction, as wellas the pharmacokinetics and surgical functionality ofMonocryl monofilament sutures, are described. These

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Monocrvl suture, an absorbable monofilament: R.S. Bezwada et a/. 1143

were measured in accordance with USP XXI16. Straighttensile strength, knot strength, elongation-to-break andYoungs modulus were measured on a constant rate-of-extension universal tensile testing machine withsuitable clamps for holding the specimens firmly.

Tissue dragThe frictional forces encountered -during passagethrough tissue werle estimated by recording the forcerequired to pull 20cm of suture through the tissue atthe rate of 30 cm min- using an Instron tensile testingmachine. In this experiment, surgically preparedposterior dorsal rat skin was used. A square section ofthis tissue was stretched and mounted on a frame. Theframe was mounted to a pulley device that wasattached to the lower jaw of the tensile testingmachine. A length of suture was attached to the upperjaw of the machine and then passed through the tissueguided by a set of pulleys. An appropriate minimumweight was attached to the end of the suture strand tojust keep the complete suture strand assembly undertension. The In&on machine was activated and as thelower jaw moved down, the response at the suture-tissue interface was recorded as a computer trace. Thesystem recorded the real-time plot of force versus pull-length as the suture passed through the tissue.Breaking strength retentionFemale Long-Evans rats weighing between 250 and300g were utilized. to evaluate the in tivo breakingstrength of Monocryl suture (sizes 5-O to 1). The ratswere each anaesthetized with an intraperitonealinjection of a mixture of ketamine hydrochloride(60 mg kg-l) and x:ylazine hydrochloride (10 mg kg-)and prepared for surgery by clipping the hair from thedorsal cervical area to the dorsal lumbosacral area. Theskin of the clipped area was then scrubbed with anantiseptic solution. A small transverse skin incision(2 cm) was made in the dorsal subcutis of each rat,immediately posteri.or to the scapula. Suture segments,each approximately 10 cm in length, were implanted bygrasping both ends of each with haemostatic forceps,inserting the forceps into the dorsal subcutis throughthe transverse skin incision, releasing the sutures andwithdrawing the forceps. Two suture segments wereimplanted in each rat, one in the right and one in theleft posteriodorsal subcutis. The skin wounds wereclosed and the rats retained for up to 3 weeks. At theend of scheduled test periods (typically i and 14 d), theappropriate rats were killed by carbon dioxide asphyxia-tion, The suture ,strands were carefully recoveredfollowing the transverse incision of the skin in thedorsoscapular area a.nd reflection of the skin posteriorly.For each size, multiple suture lots were evaluated; foreach lot, eight suture strands per time period weretested for breaking strength on a calibrated In&onUniversal Testing Instrument. The strength ofunimplanted samples was determined similarly. Theaverage breaking strength remaining was calculated asthe percentage of the original, unimplanted strength.Pooled standard deviations were calculated.In a separate study, the breaking strength retentionprofiles of size 2-0 Monocryl, dyed Vicryl and Chromic

Gut sutures were determined; four lots of each suturewere evaluated. The results obtained on dyed PDS IIsuture from another set of experiments are alsoreported; two lots of size 2-0 were tested. In thesecomparative studies, as before, eight suture strands pertime period were tested for each lot.Tissue reaction and absorptionFemale Long-Evans rats used in the tissue reaction andabsorption study were acclimatized, anaesthetized andprepared as described earlier for aseptic surgery. Amidline incision was made on the skin over the sacralspine parallel to the vertebral column. Following retrac-tion of the skin laterally, sterile suture strands weredrawn into the right and left gluteal muscles. Twosuture segments, each approximately 2 cm long, wereimplanted per muscle. The skin incisions were thenclosed and the rats retained up to 116 d.At the predetermined periods of in vivo residence,predesignated rats were killed by carbon dioxide asphyx-iation. Gluteal muscles containing the implanted suturesamples were excised, examined grossly and preservedin 10% buffered formalin fixative. A transverse sectionof each formalin-fixed sample was trimmed andprocessed for paraffin embedding, sectioning, andstaining with haematoxylin and eosin. Histologicalexamination of the implant sites was conducted usingcross-sections 6pm in thickness. To assess absorption,the average cross-sectional area of the suture samplewas calculated from suture diameters obtained with theuse of an ocular micrometer. Data from the 3 day periodwere considered to represent 100% remaining and wereused as such in calculating the median percentagesuture area remaining at subsequent periods. The tissuereactions were quantitatively evaluated by using amodified method of Sewell and associates7. Table 1details the histological grading and scoring system used.Table 1 Histological grading system of tissue reactionCharacteristic Weighting

factorWidth of zone 5Overall cell density 3Neutrophils 6Giant cells 2Lymphocytes/plasma cells 1Macrophages 1Eosinophils 1Fibroblastslfibrocytes 1A sample score is completed as shown:Parameter Grade Weighting

factor Score

Zone 2 5 10Cell density 2 3 6Macrophages 2 1 2Giant cells 1 2 2Fibroblasts 2 1 2Total 22Each characteristic is assigned a grade of W based upon dimension ordensity. The grade is then multiplied by the weighting factor to obtain thefinal score. Adjectival ratings were assigned to the reaction scores withinthese limits: 0, none, l-8, minimal; g-24, slight, 25-40. moderate; 41-56,marked; greater than 56, extensive.

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1144 Monocryl suture, an absorbable monofilament: R.S. Bezwada et al.

Surgical finctionalityThe performance of Monocryl suture for urocystotomyclosure, hysterotomy closure, gastrotomy closure,small intestinal anastomosis, colonic anastomosis,vascular ligation (splenectomy, ovariohysterectomy),joint capsule closure (arthrotomy) and laparotomyclosure was evaluated in Beagle dogs.Blood samples were obtained from all dogs fordetermination of clinical chemistry and haematologyparameters the week before surgery and approximately1 week postoperatively. In the urocystotomy study,urine samples were collected from all dogs duringsurgery and at necropsy. In all studies, vital signs(pulse, body temperature, respiration rate) weremeasured prior to surgery and daily for the first weekpostoperatively. Dogs were observed daily during thepostoperative period for general health. Twenty-eightdays after surgery, dogs were killed and a grossexamination was performed.PharmacokineticsA size Z-O, 14C-labelled Monocryl suture was preparedfrom a copolymer of [2,6-14C] caprolactone andglycolide. The synthesis of the [2,6-14C] caprolactone-glycolide copolymer and the preparation of the 14C-labelled Monocryl suture were conducted at Ethicon.[2,6-14C] Caprolactone was purchased from Du PontNEN Products.A total of 64 rats was used in the study. A 31 inchstrand of the 14C-labelled Monocryl suture wasimplanted surgically into the dorsal subcutis of eachanimal, immediately posterior to the scapular. Themean radioactivity per suture strand corresponded to19.8 &i.Following the implantation of 14C-labelled Monocrylsuture, a group of six animals, three per sex, was killedat weeks 1, 2, 3, 4, 6, 8, 9, 10 and 14. The remaining10 animals, five per sex, were killed at the end of thestudy (week 16). Radioactivity levels in the blood andvarious tissues were measured by liquid scintillationcounting. Urine, faeces and expired air were alsocollected from these animals, and the weekly output ofradioactivity up to the time of killing was determined.

RESULTS AND DISCUSSIONMechanical propertiesThe physical property test results for size 2-O and 4-OMonocryl suture are shown in Table 2. The physical

Table 2 Physical properties of Monocryl suture, sizes 2-Oand 4-OPhysical property Size 2-O Size 4.0Diameter (mils) 15.03 8.55Straight tensile strength (lb) 16.14 6.76Straight intrinsic strength (psi) 91100 117400Knot tensile strength (lb) 8.11 3.01Knot intrinsic strength (psi) 45 700 52 500Elongation (%) 39 37Youngs modulus (psi) 113000 156000

Table 3 Physical property comparison of size 2-O absorbablesutures

Straight-pull Knot-pullMaterial Diameter strength strength Elongation(mils) (lb) (psi) (lb) (psi) (%)Monocryl 15.03PDS II 13.93Chromic 15.70

gut

16.14 91 100 8.11 45700 3910.77 70700 7.37 48400 519.07 46700 4.51 23 200 22

Vicryl 13.74 15.28 103000 7.97 54000 24

properties of size 2-O Monocryl suture are compared inTable 3 to the following commercial absorbablesutures: Vicryl, PDS II and Chromic Gut.Figure 1, a graphical representation of the tensilestrengths of all commercial size 2-0 absorbable monofi-laments, normalized for cross-sectional area, showsthat Monocryl suture is the strongest of all the absorb-able monofilament sutures.Suture stiffness is an important parameter thatsignificantly influences the handling properties of asuture. Pliability or lack of stiffness is the quality ofbeing sufficiently flexible or supple to accomplishsurgical suturing, ligating or for knot tying. Suturestiffness can be calculated from the product of thesuture area moment of inertia and the Youngsmodulus of the material as obtained from stress-straincharts. The assumption was made that the suturematerials were homogeneous throughout their cross-sectional area. Table 4 shows the stiffness valuescalculated for Monocryl suture as compared toMaxon, Chromic Gut and PDS II suture. Maxon is 4.1times as stiff as Monocryl suture; Chromic Gut sutureand PDS II suture were found to be 3.8 and 1.4 timesas stiff, respectively. The lower stiffness of. Monocrylsuture, i.e. its pliability, results in excellent handlingduring surgical use with the added benefit of minimalout-of-package memory when compared to othersutures.

//

YONOCRYL

I/

1

Figure 1 A graphical representation of the tensilestrengths, normalized for cross-sectional area, of allcommercial size 2-O absorbable monofilaments.

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Monocryl suture, an absorbable monofilament: R.S. Bezwada et al. 1145

Table 4 Handling characteristics of size 2-O absorbablemonofilament suturesSuture Diameter Youngs modulus Stiffness(mils) (psi) (lb in2 x 104)Monocr I@Maxon J

15.03 113000 2.815.81 380 000 11.8Chromic gut 15.70 358 000 10.7

PDS II@ 13.93 211000 3.9

Tissue dragThe frictional forces produced by a suture duringpassage through tissue is an important consideration.Surgeons prefer a suture which can pass smoothlythrough tissue, minimizing tissue trauma. A roughstrand presents considerable resistance during tissuepassage, making it difficult to use as a continuousrunning suture. Synthetic monofilaments, because oftheir smooth surface, have less tissue drag compared to,for instance, braids, which have relatively high surfaceroughness. Even within the monofilament family, theremay be considerable differences in smoothness.Figure 2, for example, compares the tissue drag charac-teristics of size 2-O Monocryl suture with a gut suture ofsimilar size, demonstrating that the Monocryl suturepasses through the tissu.e with greater ease.Breaking strength retentionThe in tivo breaking strength retentions of various sizesof Monocryl suture are shown in Table 5. Fourteendays postoperatively, Monocryl suture retainedapproximately 20-30% of its initial tensile strength.

The breaking strengih retention profiles of size 2-OMonocryl, PDS II, Vicryl and Chromic Gut suture arecompared in Figur e 3.Tissue reaction and absorptionMicroscopic examination with tissue reaction gradingwas performed on all .slides of the implant sites. The

0 5 10 15 20 25Pull Length (cm)

Figure 2 A comparison of the tissue drag traces of size 2-OMonocryl@ and gut sutures.

. MONOCRYL*Dyed VICRYL

0 1 2 3WEEKS AFTER SUTURE IMPLANTATION

Figure 3 Average breaking strength of size 2-OMonocryl@, dyed Vicryl@, dyed PDS II@ and chromic cutsutures, as a function of implantation time in the subcutisof rats.

tissue reactions for Monocryl sutures were in theslight or minimal ranges throughout (Table 6), andwere characterized primarily by the presence ofmacrophages and fibroblasts, fewer lymphocytes andplasma cells, small numbers of polymorphonuclearleucocytes and occasional giant cells (see Figure 4).These cells gradually diminished in concentrationduring the 119d study period. The absorption ofMonocryl sutures was complete between 91 and119 d.

Table 5 In viva breaking strength retention of various sizes ofMonocryl@ suturesSuturesize

5-o4-O3-o2-o01

Mean breakingstrength, 0 days(lb) (p.s.d.)

4.55 0.166.55 0.3010.92 0.74

15.59 0.9419.43 1.3025.60 1.65

Mean breakingstrength, 14 days(lb) (pad.)

l3sd(%I1.19 0.15 26.31.45 0.22 22.22.81 0.25 25.83.86 0.58 24.74.85 0.55 24.96.20 1.08 24.2

Pooled standard deviation.t Breaking strength retpntion.

Table 6 Median tissue reaction scores* for Monocryl@ suturesafter intramuscular implantation in rats

Time tocomplete

Days postimplantation absorptionSize 3 7 28 63 91 119 (d)2-o 17 9 7.5 15 20 2.5 1196-O 10 12.5 6 11.5 0 0 91Scores are as follows: 0, no reaction: l-6, minimal reaction; g-24, slightreaction; 2540, moderate reaction; 41-56, marked reaction; 56+, extensivereaction.

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1146 Monocryl suture, an absorbable monofilament: R.S. Bezwada et al.

Figure 4 Tissue reaction and absorption of size 2-0, dyed, monofilament Monocryl@ suture at 3, 7, 28,63, 91 and 119 d postim-plantation. Haematoxylin and eosin stained paraffin embedded rat gluteal muscle. a, Monocryl suture at 3d surrounded by anirregular zone of oedema and inflammatory cells, primary macrophages and neutrophils, separating skeletal muscle cells. b,Monocryl suture at 7d with a minimal inflammatory reaction zone composed of macrophages and fibroblasts. c, Monocrylsuture at 28 dwith a slight inflammatory reaction zone composed primarily of macrophages and fibroblasts with a scatteringof eosinophils. d, Monocryl suture at 63d with a slight inflammatory reaction zone composed primarily of macrophages,fibroblasts, lymphocytes and plasma cells. e, At 91 d, the Monocryl suture has been completely absorbed. There is a slightinflammatory reaction zone composed of large, foamy macrophages centrally with fibroblasts, lymphocytes and plasma cellsat the periphery. f, At 119d, the Monocryl suture has undergone complete absorption. There is a minimal inflammatoryreaction composed of macrophages, fibroblasts, lymphocytes and plasma cells. a-f, Haematoxylin and eosin, original magnifi-cation x 150.Biomaterials 1995, ol. 16 No. 15


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Monocryl suture, an absorbable monofilament: R.S. Bezw ada et al. 1147Surgical functionalityIntraoperatively, Monocryl suture passed through thetissues with very little resistance. Knot security wasfelt to be very good based on the tactile feedback fromthe suture. All dogs recovered uneventfully fromsurgery without evidence of pain or discomfort. Bodyweights remained stable and no treatment-relatedchanges in pulse rate, body temperature, respiratoryrate or clinical laboratory values were apparent. Uponnecropsy, all surgical incision lines were shown to behealing normally with no evidence of dehiscence.PharmacokineticsThe absorption of the 14C-labelled glycolyl moiety in aglycolide-based copolymer suture was reported byKatz et ~1.~. They iround that at 22-24 weeks aftersubcutaneous implantation, nearly all of the radioac-tivity disappeared from the implantation site andappeared in expired air, urine and faeces. The presentpaper reports the results of a pharmacokinetic studycarried out with radioactive Monocryl suture inwhich the caproyl moiety was 14C labelled. Figure 5shows the absorption profile of this 14C-labelledMonocryl suture, as measured by the disappearanceof radioactivity from the implantation site. There wasan initial lag period of about 3 weeks. Thereafter, theradioactivity decreased linearly (zero-order kinetics)up to week 10. The radioactivity in the implantationsite at week 10 corresponded to 5.6% and 9.4% of theimplanted dose in males and females, respectively. Byweek 14, the radioactivity corresponded to 0.15% and0.24% of the implanted dose in males and females,respectively. These results demonstrated that theabsorption of 14C-labelled Monocryl suture isessentially complete 14 weeks after subcutaneousimplantation.

The radioactivity in the plasma reached peak levelsat week 6, but completely returned to baseline levels at

WEEKS AFTER SUTURE IMPLANTATION CFigure 5 Amounts of radioactivity in ihe surgical implanta-tion site of rats, male and female as indicated, followin&subcutaneous implantation of C-labelled Monocrylsuture. Expressed as the percentage of the total radioactiv-ity dose administered per animal.

Figure 6 Cumulative amounts of radioactive output fromrats following subcutaneous implantation of C-labelledMonocryl@ suture. Expressed as the percentage of thetotal radioactivity dose administered per animal. a, In theurine; b, in the expired air; c, in the faeces of the rat.

ii? 601B a. in urine8 50.

a WEEKS AFTER SUTURE IMPLANTATIONac 60B * Yd*+ emale8 5om b. in expired airc I

i 0:2 0 2 4 6 8 10 12 14 160 WEEKS AFTER SUTURE IMPLANTATIONb

i.:5 0 2 4 6 a 10 12 14 16WEEKS AFTER SUTURE IMPLANTATION

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1148 Monocrvl suture, an absorbable monofilament: R.S. Bezwada et al.week 16. The tissue radioactivity reached peak levels atweek 6 in the liver, kidney and testes, at week 8 in thebrain, heart, lungs and spleen, and at weeks 8-10 inmuscles, fat, lymph nodes, eye lenses and ovaries.Throughout the entire study period of 16 weeks, theradioactivity content in the tissues and organs was lessthan 0.75% of the total implanted dose. These resultsindicate that there was no unusual accumulation ofradioactivity in the tissues and organs after sutureimplantation.

Figure 6 shows the elimination profiles of radioac-tivity from implanted animals. Approximately 96% ofthe implanted dose (95.1% in males and 97.0% infemales) was eliminated from animals within 14weeks. Approximately 49% of the radioactivity wasexcreted in the urine (48.8% in males and 49.8% infemales), 41% was recovered in the expired air(40.4% in males and 42.5% in females) and 5% waseliminated in the faeces (5.0% in males and 4.1% infemales). The results indicate that the major routes ofelimination of 14C-labelled Monocryl suture areurinary excretion and pulmonary elimination of4coz.

CONCLUSIONSA new synthetic absorbable monofilament suturederived from a segmented copolymer of s-caprolactoneand glycolide, Monocryl suture, is presented. Thephysical and biological properties of Monocryl sutureare discussed. Monocryl suture possesses the higheststraight tensile strength and best handling propertiesof all the available monofilament absorbable sutures.The in viva performance of the suture was evaluatedfor breaking strength retention, absorption, tissuereaction, pharmacokinetics and surgical functionality.Tissue reaction and absorption were assessed byintramuscular implantation of sizes 2-O and 6-OMonocryl suture into rats. The tissue reactions of thesutures were in the slight or minimal ranges and wereof a foreign body nature. Absorption of the sutures wascomplete between 91 and 119 d.Multiple surgical procedures were performed inBeagle dogs to judge the surgical performance of the

sutures. The use of Monocryl sutures for urocystotomy,laparotomy, hysterotomy, intestinal anastomosis,gastrotomy, vascular ligation and joint capsule closurewere satisfactory based upon the intraoperative,postoperative and necropsy results.

ACKNOWLEDGEMENTSThe authors are deeply indebted to Dr Constance L. Acefor her NMR characterization of the polymers. Theauthors also wish to acknowledge the help of Dr IreneNozad with this project.

REFERENCESCraig PH, Williams JA, Davis, KW et al. A biologicalcomparison of polyglactin 919 and polyglycolic acidsynthetic absorbable sutures. Surg Gynecol O&et1975; 141:1-10.Ray JA, Doddi A, Regula D, Williams JA, Melveger A.Polydioxanone (PDS), a novel monofilament syntheticabsorbable suture. Surg Gynecol Obstet 1981; 53: 97-507.Katz AR, Mukhejee DP, Kaganov AL, Gordon S. A newsynthetic monofilament absorbable suture made frompolytrimethylene carbonate. Surg Gynecol Obstet 1985;161:213-222.Bezwada RS, Jamiolkowski DD. Segmented copolymersof &-caprolactone and glycolide for new absorbablemonofilament sutures. Transactions of the Society ofBiomaterials (Annual Meeting, 28 April-2 May 1993),XVI: 40.Bezwada RS, Jamiolkowski DD, Shalaby SW. Segmen-ted copolymers of &-caprolactone and glycolide. USPatent 5,133,739, July 1992.Pharmacopeia of the Un ited States, Vol. XXII. Easton,PA: Mack, 1989: 1614-1615.Sewell WR,. Wiland J and Craver BN. New methods ofcomparing sutures of ovine catgut with sutures ofbovine catgut in three species. Surg Gynecol Obstet1955: 100:483-494.Rodeheaver GT, Thacker JG, Owen J, Strauss M, Master-son T, Edlich RR. Knotting and handling characteristicsof coated synthetic absorbable sutures. j Surg Res 1983;35: 525-530.

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fios de sutura no mercado

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