SURGICAL RESEARCH

EFFECT OF RE-STERILIZATION OF SURGICAL SUTURES

BY ETHYLENE OXIDE

PREM ANAND NAGARAJA AND DEVI SHETTY

Narayana Hrudayalaya, Bommasandra Industrial Area, Anekal Taluk, Bangalore, Karnataka, India

Background: Surgical suture packs are opened (and external packaging removed) on the operating table prior to surgery. Some ofthese suture packs may not be used in the surgery for reasons of inappropriateness or change in the surgical technique or followingaccidental contact with a non-sterile surface. These unused sutures with their foil packs still unopened are sometimes re-sterilizedusing ethylene oxide to allow for reuse. This re-sterilization of unopened suture packs can be contentious, due to legislation and healthregulations in developed countries. The purpose of the present paper was to measure the effect of such repeated gas sterilizationon sutures.Methods: The knot tensile strength was measured for new sterile sutures and ethylene oxide re-sterilized sutures. The tests wereconducted on two available brands of sutures, including both absorbable and non-absorbable synthetic sutures.Results: No statistically significant difference was observed in the tensile strengths between the two sets of sutures, before and afterre-sterilization. Some foil packs showed slight crimping after re-sterilization, but remained intact. No humidity was observed insidethe foil packs.Conclusions: Re-sterilization of unused suture foil packs can be carried out without loss of tensile strength.

Key words: knot tensile strength, re-sterilization, surgical sutures.

INTRODUCTION

Surgical sutures are available with two layers of packaging: anouter paper–plastic layer that maintains sterility and an inner foilpack that acts as a moisture barrier. Surgical suture packs arelabelled for single use only. However, more often than not, theouter packaging is removed but the foil pack is not opened forvarious reasons. It may happen that the surgical procedureplanned may be changed in the course of the surgery, whichmay require a different suture material or an altogether differentsize. Unused suture foil packs may accidentally contact a non-sterile area in the surgical field or may be dropped on the floor,rendering it unsuitable for use. These sutures are re-sterilized forreuse, using activated glutaraldehyde or ethylene oxide. Absorb-able sutures are made of polyglactin or polyglycolic acid whilenon-absorbable sutures are made of polyester or polypropylene.We have attempted to study the effect of ethylene oxide re-ster-ilization on the mechanical properties of these polymers. Knottensile strength was determined for all these types of sutures.The re-use of re-sterilized sutures is not an accepted practice indeveloped countries following strict health regulations. Ethicalissues and extensive monitoring for dependable quality of re-sterilization make it contentious to implement such methodology.However, in the developing countries it remains an acceptedpractice to re-sterilize unopened suture packs. This could be the

fallout of financial and managerial issues connected with materialmanagement.

METHODS

Twenty non-absorbable and 15 absorbable suture types being usedat Narayana Hrudayalaya, Bangalore, were chosen for testing.Two commercial brands of sutures were tested. Ten of the non-absorbable suture types were from Johnson & Johnson (brand A;Ethicon, Johnson & Johnson, Mumbai, India) while the remaining10 were from Centenial (brand B; Centenial Surgical Suture,Murbad, Mumbai). Eight of the absorbable sutures were fromCentenial (brand B) and the remaining seven from Johnson &Johnson (brand A). The details of the sutures chosen for testingare given in Table 1.

Two numbers of each suture type were procured for the testing.The outer packaging of one of each suture type was openedto simulate an in-use situation, and the sealed inner foil pouchwas repacked in paper-plastic packaging. These repacked sutureswere sterilized using 100% ethylene oxide in a Sterivac 8XL (3M,USA). The process of re-sterilization was carried out in theinstitute’s own Central Sterile Supplies Department. The sutureswere subjected to a 3-h exposure and 12-h aeration at 37�C.

All the suture packs, including the original and re-sterilized,were inspected for intactness of the packaging and integrity ofthe foil packs. The tensile strength testing of the re-sterilizedsutures was out-sourced. The knot tensile strength testing wasperformed at a laboratory accredited by the National Accredita-tion Board for Testing and Calibration Laboratories, New Delhi.The testing was performed according to American Society forTesting and Materials D 412 standard test procedure.1 The rateof loading used was 60mm/min. The end-point considered wasa break in the suture. Two readings of ultimate load were taken for

P. A. Nagaraja MD; D. Shetty MS.

Correspondence: PremAnandNagaraja, Narayana Hrudayalaya, no. 258/A,Bommasandra Industrial Area, Anekal Taluk, Hosur Road, Bangalore 560099,Karnataka, India.Email: dr.prem@indiatimes.com

Accepted for publication 5 May 2005.

ANZ J. Surg. 2007; 77: 80–83 doi: 10.1111/j.1445-2197.2006.03560.x

� 2007 Royal Australasian College of Surgeons

each suture. The Student’s t-test and Wilcoxon signed ranks testswere used to calculate statistical differences in the measured knottensile strengths before and after re-sterilization.

RESULTS

After re-sterilization no suture packs were found to be ruptured,bloated or deformed otherwise. However, some foil packs of brandA sutures showed some wrinkles, but no rupture or packagingdisruption. All suture packs of brand B showed no visible changesafter re-sterilization. No suture packs had de-lamination betweenthe foil pack and the external polymer layer. All the foil packs afterre-sterilization opened at the adhesive seal and did not tear across.

All samples tested met the United States Pharmacopeia limits onaverage knot tensile strength.2 The out-of-pack mean knot tensilestrengths of all the sutures increased, decreased or stayed the sameafter re-sterilization, in comparison to the values observed before re-sterilization. These changes were small and have not been observedto be significant. The overall results of tensile strength testing aredepicted in Table 2.

Statistical analysis was done using SPSS (version 10.0, SPSSInc., Chicago, IL, USA) for significance of difference in tensilestrength before and after re-sterilization and is depicted in Tables3 and 4.

As seen in Tables 3, 4, the difference in tensile strengths of bothtypes of sutures from both brands before and after re-sterilizationis not statistically significant. Analysis of the readings obtainedfrom all the sutures of both the brands before and after re-sterilization found no statistically significant difference (Table 5).

DISCUSSION

Reuse of single-use devices is documented widely. The firstrecycled device in the USA was the haemodialysis filter, whichremains the most commonly reused disposable medical device.3

The practice of recycling these filters was that patients used onlytheir own filters and therefore, patient-to-patient transmitted infec-tions were not an issue. This practice has become accepted world-wide, but it is not risk free. Although studies have not found deathrates to be increased related to haemodialysis filter reuse, theCenters for Disease Control and Prevention has investigated 12outbreaks of pyrogenic reactions or bacterial infections, primarilyas a result of inadequate reprocessing.4 Sutures with their outerpackages opened but inner packaging intact are often labelled asopened but unused devices.5 These are sometimes re-sterilized forreuse, although they are labelled for single use only. The mechan-ical properties of the polymers used in sutures are known to beaffected by sterilization methods.

The effectiveness of reprocessing procedures requires constantsurveillance and validation. Tests must be performed for pyro-gens, sterility, and ethylene oxide residues. Quality assurance isa key factor to ensure that the system is controlled and productintegrity and safety are not compromised. Product sampling ona routine basis, as well as periodic review of the external variables(e.g. employee education, physical facility remodeling) that mayaffect reuse products, also must occur.6

The most obvious benefit of reprocessing is the potentialfor saving money. The greatest opportunity for cost savings isfound in reprocessing critical devices, such as diagnostic cardiac

Table 1. Type of sutures, sizes and the manufacturer

No Suture Size Material Nature Company

1 2–0, 3–0, 4–0, 5–0 PO, silicone coated Non-absorbable Centenial2 2–0, 4–0, 5–0, 6–0, 7–0, 8–0 PP, monofilament Non-absorbable Centenial3 2–0, 4–0, 5–0, 6–0, 7–0, 8–0 PP, monofilament Non-absorbable Johnson & Johnson4 2–0, 3–0, 4–0 PO, green Non-absorbable Johnson & Johnson5 1–0, 2–0, 3–0 PGA Absorbable Centenial6 1–0, 2–0, 3–0 PGA, undyed Absorbable Centenial7 0–0, 1–0, 2–0, 3–0, 5–0, 6–0 PG Absorbable Johnson & Johnson

PG, polyglactin; PGA, polyglycolic acid; PO, polyester; PP, polypropylene.

Table 2. Results of tensile strength testing

No. Nature Brand Situation Range of tensilestrength (kg)

Mean ultimateload (kg)

1 Absorbable, PG A Original sutures 1.34–8.8 5.322 Absorbable, PGA B Original sutures 2.8–7.8 4.863 Non-absorbable, PO A Original sutures 1.72–4.6 2.954 Non-absorbable, PO B Original sutures 1.2–3.2 2.085 Non-absorbable, PP A Original sutures 0.19–3.8 1.096 Non-absorbable, PP B Original sutures 0.17–3.6 1.087 Absorbable, PG A Re-sterilized sutures 1.3–8.8 5.338 Absorbable, PGA B Re-sterilized sutures 2.6–8.4 4.859 Non-absorbable, PO A Re-sterilized sutures 1.72–5.0 3.13

10 Non-absorbable, PO B Re-sterilized sutures 1.04–3.6 2.1511 Non-absorbable, PP A Re-sterilized sutures 0.16–3.8 1.0812 Non-absorbable, PP B Re-sterilized sutures 0.16–3.0 1.0

A, brand A (Johnson & Johnson); B, brand B (Centenial); O, original; PG, polyglactin; PGA, polyglycolic acid; PO, polyester; PP, polypropylene;R, re-sterilized.

Methods: ASTM D 412.1 Rate of loading: 60mm/min.

� 2007 Royal Australasian College of Surgeons

RE-STERILIZATION OF SURGICAL SUTURES 81

catheters, forceps, and orthopaedic burrs.7 However, expensivedisposables such as sutures also contribute to effective utilizationof financial resources, more so in developing countries.

An article published in 2002 documented breaches in the integ-rity of packs, puffier or wrinkled packs, de-lamination and someinstances of tearing across packs while being opened after re-sterilization.8 In the present study some of the foil packs of a par-ticular brand were observed to be lightly crimped, but with nodamage to the overall integrity or any change in behavioural char-acters of the suture packs.

A keymechanical assessment is the tensile test, which measuresthe force required to stretch a device for a range of extensions.Other tests for reprocessed single-use items include measures ofhardness, torsional rigidity and flexibility, fatigue, electrical con-ductivity, and leaks (for balloons). Subjective measurementsinclude visual inspection and observation with a low-powermicro-scope. Health-care workers should keep in mind that it may bedifficult to simulate in an experimental situation the variousstresses that a device is exposed to in a clinical environment.6

No statistically significant difference was observed in the meanknot tensile strengths of all the sutures before and after re-sterilization.Woods et al. documented differences in tensile strengthconcurrent with changes in the pack integrity, but these differenceswere not statistically significant.8 Loss of seal integrity might notcause an initial strength loss. However, in the case of all absorbablesutures having the inner seal destroyed during repackaging, expo-sure to increased humidity for an extended time will cause suturedegradation. This can lead to a loss of strength after shelf ageing,and a loss of strength and possible changes in the degradationbehaviour after clinical use. These changes in the suture materialcould result in wound dehiscence or other complications. Changesin suture strengths are associated with hydrolysis of the suturepolymer following exposure to moisture.9 This happens followingloss of integrity of absorbable sutures, as reported byWoods et al.8

The concept of reprocessing and related protocols in standardhealth-care facilities and third-party reprocessors are generally

less stringent than those used in industry and these may provideless consistent results.10

CONCLUSION

The most significant issue in evaluating a reuse programme ispatient safety. The steps involved in reprocessing are numerousand complex. The process cannot be implemented casually, butmust be controlled and vigorously monitored to ensure that cleanand sterilized reprocessed items are used. Patient safety is para-mount in all phases of reprocessing and any item that cannot beguaranteed to be free from blood, fluid, body tissues, bioburden,or other contaminants should not be included in a reprocessingprogramme. Health-care facilities are responsible for demonstrat-ing that reprocessed devices continue to be safe, effective, and ofa high quality.11

Loss of integrity of suture packs following re-sterilization isknown to be associated with significant changes in the expectedbehaviour of the suture material. For some types of sutures theoriginal expiration date is not listed on the inner suture package.If the expiration date is related to the mechanical characteristicsof the suture or to the package that ensures its integrity rather thanits sterility, the original date may be lost following repackaging.If the expiration date is related to an assurance of sterility, thena new expiration date should be applied. The most significantconclusion to be drawn from the present study is the observationthat, as is true for other types of devices, it is not always possibleto make general conclusions about the effects of re-sterilizationon sutures. We, however, conclude that re-sterilization of non-absorbable sutures may be carried out in select cases where theinner packaging is intact and the suture reused when the packintegrity is not breached after re-sterilization. The same, however,cannot be ensured in the case of absorbable sutures. It is wellknown that re-sterilization of items such as surgical sutures isnot an accepted practice in developed countries, both by legisla-tion and the process of hospital accreditation. However, develop-ing countries would benefit from the present study in that valuableresources could be put to good use, lest they are wasted. Ethyleneoxide is still a widely used sterilant for heat-sensitive surgicalitems and supplies used in patient care and are available in almostall the hospitals in developing countries. In the event that ethyleneoxide may not be available, evaluation of plasma sterilization mayhave to be carried out on similar lines, subject to permissibilityand legislation.

Tensile strength is an important factor in deciding the roleof sutures in maintaining good opposition of the edges of thesurgical wound, thereby enabling them to heal rapidly. Lossof tensile strength in a suture would lead to premature wounddehiscence and failure to heal. Other factors such as rate of dis-solution and altered chemical nature were not studied in the pres-ent project.

Table 3. Paired t-test analysis of tensile strengths of sutures beforeand after re-sterilization

Paired suture samples d.f. P (two-tailed)

PP_A_O vs PP_A_R 13 0.835PP_B_O vs PP_B_R 11 0.249PO_A_O vs PO_A_R 5 0.140PO_B_O vs PO_B_R 7 0.307PG_A_O vs PG_A_R 13 0.845PGA_B_O vs PGA_B_R 15 0.906

A, brand A (Johnson & Johnson); B, brand B (Centenial); O, original;PG, polyglactin; PGA, polyglycolic acid; PO, polyester; PP, polypropylene;R, re-sterilized.

Table 4. Wilcoxon signed ranks test

PP_A_R vsPP_A_O

PP_B_R vsPP_B_O

PO_A_R vsPO_A_O

PO_B_R vsPO_B_O

PG_A_R vsPG_A_O

PGA_B_R vsPGA_B_O

Z –1.783† –0.153† –1.604‡ –1.185‡ –0.788‡ 0.000§Asymp. P (two tailed) 0.075 0.878 0.109 0.236 0.431 1.000

A, brand A (Johnson & Johnson); B, brand B (Centenial); O, original; PG, polyglactin; PGA, polyglycolic acid; PO, polyester; PP, polypropylene;R, re-sterilized.

†Based on positive ranks; ‡based on negative ranks; §sum of negative ranks equals sum of positive ranks.

� 2007 Royal Australasian College of Surgeons

82 NAGARAJA AND SHETTY

ACKNOWLEDGEMENTS

We wish to thank Cosmic Industrial Laboratories, ElectronicsCity, Bangalore for their help in testing the tensile strength ofsuture materials.

REFERENCES

1. American National Standards Institute. Standard Test Methodsfor Vulcanized Rubber and Thermoplastic Elastomers–Tension.Document Number: ASTM D412–98a(2002)e1. ANSI: ASTMInternational, 2002.

2. The United States Pharmacopeial Convention. USP 24-Nf 19Supplement 2. Rockville, MD: The United States PharmacopeialConvention, July 1, 2000; 2859.

3. Gibson NK. The Reuse of Single-Use Medical Devices. Guide-lines for Healthcare Facilities, Canadian Healthcare Association.Debate on reuse of disposable medical equipment fueled byFDA. J. Clin. Monit. 1998; 14: 75.

4. Schultz JK. Reservations are voiced about the reuse of single-useitems. OR Manager 1997; 13: 1–7.

5. Spears LD. Enforcement Priorities for Single-Use DevicesReprocessed by Third Parties and Hospitals. Guidance for Indus-try and for FDA Staff. US Department of Health and HumanServices, US Food and Drug Administration, Center for Devicesand Radiological Health, Division of Enforcement III, Office ofCompliance, 2000.

6. Reichert M. Reuse of disposables: choice to reuse disposablesrequires factual assessment. OR Manager 1996; 12: 8–9.

7. Radford R. Reprocessing single-use devices: choosing a third-party reprocessor for a given single-use device. Infect. ControlToday 2001; 5: 27–9.

8. Woods TO, Brown SA, Merritt K, McNamee S, Hitchins V.Effects of repeated ethylene oxide sterilization on syntheticabsorbable sutures. User Facility Reporting Bulletin. US Foodand Drug Administration, Center for Devices and RadiologicalHealth, Division of Enforcement III, Office of Compliance, 2002.

9. Middleton JC, Tipton AJ. Synthetic biodegradable polymers asmedical devices. Med. Plast. Biomaterials 1998; 5: 30–9.

10. ECRI. Special Report. Reuse of Single-Use Medical Devices:Making Informed Decisions. Plymouth Meeting, Pa: ECRI. 1997.

11. Dunn D. Reprocessing single-use devices: equipment connec-tion. AORN J. 2002; 75: 1143–58.

Table 5. Analysis of tensile strengths of all sutures before and afterre-sterilization

Original vs re-sterilized

Pairedsample test

d.f. 69 P (two-tailed) 0.782

Wilcoxonsigned ranks test

Z –0.802† Asymptotic P (two-tailed) 0.422

†Based on negative ranks.

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RE-STERILIZATION OF SURGICAL SUTURES 83