Continuous versus interrupted skin sutures for non‐obstetric surgery

Abstract

Background

Most surgical procedures involve a cut in the skin, allowing the surgeon to gain access to the surgical site. Most surgical wounds are closed fully at the end of the procedure; this review focuses on these closed wounds. There are many ways to close the surgical incision, for example, using sutures (stitches), staples, tissue adhesives or tapes. Skin sutures can be continuous or interrupted. In general, continuous sutures are usually subcuticular and can be absorbable or non‐absorbable, while interrupted sutures are usually non‐absorbable and involve the full thickness of the skin ‐ although some surgeons do use absorbable interrupted sutures.

Objectives

To compare the benefits and harms of continuous compared with interrupted skin closure techniques in participants undergoing non‐obstetric surgery.

Search methods

In August 2013 we searched the following databases: Cochrane Wounds Group Specialised Register; The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In‐Process & Other Non‐Indexed Citations); Ovid Embase; and EBSCO CINAHL.

Selection criteria

We included only randomised controlled trials (RCTs) that compared skin closure using continuous sutures with skin closure using interrupted sutures, irrespective of whether there were differences in the nature of the suture materials used in the two groups. We included all relevant RCTs in the analysis, irrespective of language of publication, publication status, publication year or sample size.

Data collection and analysis

Two review authors independently identified the trials and extracted data. We calculated the risk ratio (RR) with 95% confidence intervals (CI) for comparing binary outcomes between the groups, and calculated the mean difference (MD) with 95% CI for comparing continuous outcomes. We performed meta‐analysis using a fixed‐effect model and a random‐effects model. We performed intention‐to‐treat analysis whenever possible.

Main results

We included five RCTs with a total of 827 participants. Outcomes were available for 730 participants (384 participants randomised to continuous sutures and 346 participants to interrupted sutures). All the trials were of unclear or high risk of bias. The participants underwent abdominal or groin operations. The only outcomes reported in the trials were superficial surgical site infection, superficial wound dehiscence (breakdown) and length of hospital stay. Other important outcomes such as quality of life, long‐term patient outcomes and use of healthcare resources were not reported in these trials.

Overall, 6.5% (39/602 participants, four trials) developed superficial surgical site infections. There was no significant difference between the groups in the proportion of participants who developed superficial surgical site infections (RR 0.73; 95% CI 0.40 to 1.33). A total of 23 participants (23/625 (3.7%), four trials) developed superficial wound dehiscence. Twenty‐two of the 23 participants belonged to the interrupted suture group.The proportion of participants who developed superficial wound dehiscence was statistically significantly lower in the continuous suture group compared to the interrupted suture group (RR 0.08; 95% CI 0.02 to 0.35). Most of these wound dehiscences were reported in two recent trials in which the continuous skin suture groups received absorbable subcuticular sutures while the interrupted skin suture groups received non‐absorbable transcutaneous sutures. The non‐absorbable sutures were removed seven to nine days after surgery in the interrupted sutures groups whilst sutures in the comparator groups were not removed, being absorbable. The continuous suture technique with absorbable suture does not require suture removal and provides support for the wound for a longer period of time. This may have contributed to the difference between the two groups in the proportion of participants who developed superficial wound dehiscence. There was no significant difference in the length of the hospital stay between the two groups (MD ‐1.40 days; 95% CI ‐7.14 to 4.34).

Authors' conclusions

Superficial wound dehiscence may be reduced by using continuous subcuticular sutures. However, there is uncertainty about this because of the quality of the evidence. Besides, the nature of the suture material used may have led to this observation, as the continuous suturing technique used suture material that did not need to be removed, whereas the comparator used interrupted (non‐absorbable) sutures that did need to be removed. Differences in the methods of skin closure have the potential to affect patient outcomes and use of healthcare resources. Further well‐designed trials at low risk of bias are necessary to determine which type of suturing is better.

Plain language summary

Continuous versus interrupted stitches for closing the skin after non‐childbirth surgery

Background

During operations surgeons make a cut (incision) in the skin to gain access to the surgical site. Incisions are closed with sutures (stitches), staples, tissue adhesives or tapes. Sutures can be continuous or interrupted. Continuous sutures are usually inserted underneath the skin surface using absorbable or non‐absorbable suture material. Interrupted sutures involve the full thickness of the skin and are usually non‐absorbable (but not always).

Impaired wound healing increases costs of health care and leads to poor cosmetic results. We investigated whether it is better to use continuous or interrupted sutures to close wounds after non‐childbirth surgery by performing a thorough search of the medical literature for randomised controlled trials (RCTs) that compared these two methods of skin closure (in August 2013).

Study characteristics

We identified five RCTs with a total of 827 participants. Seven hundred thirty participants (384 received continuous sutures and 346 interrupted sutures) provided data for this review. Participants had abdominal or groin operations.

Key results

The only outcomes reported were, superficial surgical site infection, superficial wound breakdown and length of hospital stay. No other important outcomes, including quality of life, long‐term patient outcomes and use of healthcare resources, were reported.

Approximately 6% of participants developed superficial surgical site infection, but there was no significant difference between the two groups in the proportion of participants who developed these. Approximately 4% of participants developed superficial wound breakdown. The proportion of participants with this problem in the continuous suture group was approximately one‐tenth of that in the interrupted suture group. Most wound breakdowns occurred in two trials that used absorbable sutures for continuous suturing and non‐absorbable sutures for interrupted suturing. Non‐absorbable sutures are removed seven to nine days after surgery, but absorbable sutures are not removed, and so support the wound for longer ‐ which may account for the difference in distribution of this problem between groups. There was no significant difference between groups for length of hospital stay.

Superficial wound breakdown is reduced by continuous subcuticular suturing. However, the trials that contributed to this result had suture removal in only one group (interrupted sutures), which may have led to this observation. The number of participants included in this review was small and follow‐up after surgery was short.

Quality of evidence

The overall quality of evidence was very low. Levels of bias across the studies were mostly high or unclear, so there may have been flaws in trial organisation that could produce erroneous results.

Future research

Further well‐designed trials at low risk of bias are necessary.

Summary of findings

Summary of findings for the main comparison. Continuous skin sutures compared to interrupted skin sutures for non‐obstetric surgery.

Continuous skin sutures compared to interrupted skin sutures for non‐obstetric surgery
Patient or population: participants with non‐obstetric surgery Settings: secondary Intervention: continuous skin sutures Comparison: interrupted skin sutures
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	No of participants (studies)	Quality of the evidence (GRADE)
	Assumed risk	Corresponding risk
	Interrupted skin sutures	Continuous skin sutures
Superficial surgical site infection	71 per 1000	52 per 1000 (29 to 95)	RR 0.73 (0.4 to 1.33)	602 (4 studies)	⊕⊝⊝⊝ very low1,2
Superficial wound dehiscence	75 per 1000	6 per 1000 (2 to 26)	RR 0.08 (0.02 to 0.35)	625 (4 studies)	⊕⊕⊝⊝ low1
Hospital stay	The mean hospital stay in the control groups was 13.9 days	The mean hospital stay in the intervention groups was 1.4 days lower (7.14 lower to 4.34 higher)		105 (1 study)	⊕⊝⊝⊝ very low1,3
*The basis for the assumed risk is the control group risk across studies. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; RR: Risk ratio.
GRADE Working Group grades of evidence High quality: further research is very unlikely to change our confidence in the estimate of effect Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate Very low quality: we are very uncertain about the estimate

¹ The trial(s) was (were) of high risk of bias
 ² The confidence intervals overlapped 1 and either 0.75 or 1.25, or both. The number of events in the intervention and control group was fewer than 300
 ³ The confidence intervals overlapped 0 and minimal clinically important difference. The total number of participants in the intervention and control group was fewer than 400

Background

Description of the condition

Many people undergo surgical operations during their lifetime. Worldwide, an estimated 234 million surgical procedures are performed each year (Weiser 2008). In most surgical operations, surgeons make a cut (incision) to gain access to the tissue in which the surgery is performed. After the surgical procedure is complete they close the incision, in most instances, resulting in a closed surgical wound.

The proportion of patients who develop wound healing complications such as surgical site infection and wound dehiscence (breakdown) depends upon various factors, including the type of surgery, method of wound closure, systemic illnesses of the patients, medication(s) they take (including antibiotic prophylaxis and other drugs that may impair wound healing), antiseptic measures taken to prevent wound complications, and the length of follow‐up (Garner 1986; Guo 2010; Le 2007; Mannien 2011; Reilly 2006; Woodfield 2009). Postoperative surgical site infections can increase the length of hospital stay and result in increased costs of health care (Herwaldt 2006). Impaired wound healing can lead to poor cosmesis (appearance of the wound) due to the development of hypertrophic scars (enlargement and overgrowth of scar tissues) (NCBI‐MeSH‐Cicatrix‐Hypertrophic 1993), and keloid scars (sharply elevated, irregularly shaped, progressively enlarging scar; different from a hypertrophic scar in that the former does not spread to surrounding tissues) (NCBI‐MeSH‐Keloid 2012).

Description of the intervention

There are many ways to close the surgical incision, for example, using sutures (stitches), staples, tissue adhesives or tapes (Biancari 2010; Coulthard 2010). Sutures can be absorbable or non‐absorbable and can be continuous or interrupted (Pauniaho 2010). Absorbable suture materials include polyglecaprone, polydioxanone and polyglactin, while non‐absorbable sutures include polypropylene, nylon and silk. In general, continuous sutures are usually subcuticular (intradermal; i.e. within the layers of the skin) and can be absorbable or non‐absorbable (Pauniaho 2010; Selvadurai 1997). On the other hand, interrupted sutures are usually non‐absorbable, and involve the full thickness of the skin (Pauniaho 2010), although some surgeons do use absorbable interrupted sutures (Parell 2003).

How the intervention might work

Continuous sutures may provide a better seal, since this approach involves approximating the tissue in a continuous way and, hence, may have the potential to prevent bacterial invasion of the surgical wound. However, some surgeons advocate interrupted sutures, since continuous suturing may not allow pus to drain, and a tightly pulled continuous suture can strangulate the wound edges (McLean 1980). Since the choice of interrupted or continuous suture is linked with whether the suture material is absorbable or non‐absorbable, the advantages or disadvantages of using absorbable and non‐absorbable sutures may also play a role in how an intervention might work. The advantage of using absorbable suture materials is that there is no need to remove the sutures after the wound heals. However, some claim that non‐absorbable sutures may lead to a reduced inflammatory response, and so are better than absorbable sutures for skin closure (Parell 2003).

Why it is important to do this review

As mentioned previously, postoperative surgical site infections can increase the hospital stay and can result in increased costs of health care (Herwaldt 2006). Impaired wound healing can lead to a requirement for additional dressings, hospital visits, poor cosmesis and delayed return to normal activity. There is neither consensus nor evidence from systematic reviews regarding the best method of skin closure for non‐obstetric surgical wounds. One systematic review that evaluated the method of closure of caesarean section skin wounds did not find any conclusive evidence for any one method of skin closure, although this review included only one randomised controlled trial (Mackeen 2012). Another systematic review evaluating closure methods for episiotomy wounds and second‐degree perineal tears found that continuous sutures were better than interrupted sutures for short‐term outcomes such as pain (Kettle 2012). A further systematic review found no evidence of a difference between the use of staples or sutures in the risk of surgical site infection and wound dehiscence when closing leg wounds after harvesting of vein grafts (Biancari 2010). A systematic review by Coulthard 2010 found sutures were significantly better than tissue adhesives for minimising wound dehiscence, and were significantly faster to use. This review will provide guidance to surgeons regarding the suturing technique that can be used, should they choose to perform skin closure using sutures.

Objectives

To compare the benefits and harms of continuous compared with interrupted skin closure techniques in participants undergoing non‐obstetric surgery.

Methods

Criteria for considering studies for this review

Types of studies

We included randomised controlled trials (RCTs), irrespective of their use of blinding, language of publication, publication status, date of publication, study setting or sample sizes. We planned to include cluster randomised controlled trials if the effect estimate was available after adjusting for clustering effect. We excluded quasi‐randomised studies (where the methods of allocating participants to a treatment are not strictly random, for example, date of birth, hospital record number, alternation) and other study designs.

Types of participants

People, of any age and sex, undergoing non‐obstetric surgery. We have excluded obstetric operations because there are already systematic reviews addressing methods of skin closure after caesarean sections and perineal closure after episiotomies or perineal tears (Mackeen 2012; Kettle 2012).

Types of interventions

We included trials that compared skin closure using continuous sutures versus interrupted sutures, irrespective of whether there were differences in the nature of the suture material used. We recognise that if there are differences in the nature of material used for suturing, outcomes might differ because of the nature of the suturing, or because of the nature of the suture material, or both. However, in reality, the choice of suture material may depend upon the suture method adopted. We planned to address this issue of different suturing materials by exploring heterogeneity and by subgroup analysis.

We excluded trials in which the difference between the groups compared was only in the suture material used if both groups received continuous skin sutures or if both groups received interrupted skin sutures.

Types of outcome measures

Primary outcomes

1. Surgical site infection within 30 days of operation. We attempted to use the standard definition of surgical site infection described by Horan 1992. Otherwise, we have accepted the definitions stated by the authors of the reports.

   1. Superficial.

   2. Deep.

2. Wound dehiscence within 30 days of operation. Postoperative wound dehiscence refers to wound disruption resulting from poor wound healing caused by various factors such as type of incision, infection, anaemia, diabetes, ascorbic acid deficiency, etc (Keill 1973). Dehiscence is classified as: superficial (dehiscence involving skin and subcutaneous tissue) or deep (burst abdomen or dehiscence of fascia).

3. Quality of life (short‐term and long‐term; however defined by authors).

Secondary outcomes

1. Hypertrophic scar at maximal follow‐up.

2. Keloid scar at maximal follow‐up.

3. Incisional hernia at maximal follow‐up (in case of abdominal surgery).

4. Length of hospital stay (for inpatient surgery, includes any readmissions for wound‐related complications for a period of one year; however defined by authors).

5. Impact to the patient (in terms of return to activity and return to work) and to the healthcare funder (in terms of costs for dressings or treatment related to wound complications).

Search methods for identification of studies

Electronic searches

In August 2013 we searched the following electronic databases to identify reports of relevant RCTs: 

• Cochrane Wounds Group Specialised Register (searched 28 August 2013);

• The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 7);

• Ovid MEDLINE (1946 to August Week 2 2013);

• Ovid MEDLINE (In‐Process & Other Non‐Indexed Citations August 21, 2013);

• Ovid EMBASE (1974 to 2013 Week 33);

• EBSCO CINAHL (1982 to 23 August 2013).

We used the following search strategy in The Cochrane Central Register of Controlled Trials (CENTRAL):

#1 MeSH descriptor: [Suture Techniques] explode all trees1449
 #2 MeSH descriptor: [Sutures] explode all trees675
 #3 (closure near/3 method*):ti,ab,kw 259
 #4 ((interrupted or continuous*) near/3 sutur*):ti,ab,kw 210
 #5 #1 or #2 or #3 or #4 2120
 #6 MeSH descriptor: [Wound Infection] explode all trees2954
 #7 MeSH descriptor: [Sepsis] explode all trees2823
 #8 MeSH descriptor: [Soft Tissue Infections] explode all trees68
 #9 MeSH descriptor: [Surgical Wound Dehiscence] explode all trees343
 #10 (surg* near/5 infect*):ti,ab,kw 3982
 #11 (surg* near/5 wound*):ti,ab,kw 4379
 #12 (surg* near/5 site*):ti,ab,kw 986
 #13 (surg* near/5 incision*):ti,ab,kw 1034
 #14 (surg* near/5 dehisc*):ti,ab,kw 378
 #15 (wound* near/5 dehisc*):ti,ab,kw 546
 #16 ((deep next infection*) or "deep sepsis" or (infected next collection*)):ti,ab,kw 119
 #17 #6 or #7 or #8 or #9 or #10 or #11 or #12 or #13 or #14 or #15 or #16 9971
 #18 #5 and #17 5

The search strategies for Ovid MEDLINE, Ovid EMBASE and EBSCO CINAHL can be found in Appendix 1. We combined the Ovid MEDLINE search with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity‐ and precision‐maximising version (2008 revision) (Lefebvre 2011). We combined the EMBASE search with the Ovid EMBASE filter developed by the UK Cochrane Centre (Lefebvre 2011). We combined the CINAHL searches with the trial filters developed by the Scottish Intercollegiate Guidelines Network (SIGN 2012). We did not restrict studies with respect to language, date of publication or study setting.

We searched the metaRegister of Controlled Trials (mRCT) (http://www.controlled‐trials.com/mrct/) and the ICTRP (International Clinical Trials Registry Platform) portal maintained by World Health Organization (http://apps.who.int/trialsearch/). The meta‐register includes the ISRCTN Register and the NIH ClinicalTrials.gov Register among others. The ICTRP portal includes these trial registers, along with trial registry data from a number of countries.

Searching other resources

We searched the references of those trials for which we retrieved the full text to identify further relevant trials. We contacted suture manufacturers, such as Ethicon, to enquire about any unpublished trials, but received no response.

Data collection and analysis

We performed the systematic review following guidance in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011a).

Selection of studies

Two review authors (KSG and CT) independently sifted through the search results and identified references for which the full text should be retrieved. We sought the full text for any reference that was considered likely to meet the inclusion criteria. Final decisions regarding inclusion or exclusion of studies were based on reading the full text. We have listed the excluded studies with reasons for their exclusions (Characteristics of excluded studies). We resolved any differences in opinion through discussion. We did not apply any restrictions relating to language of publication or publication status.

Data extraction and management

Two review authors (KSG and CT) independently extracted the following data.

1. Year and language of publication.

2. Country of conduct of the trial.

3. Year of conduct of the trial.

4. Inclusion and exclusion criteria.

5. Sample size.

6. Type of surgery.

7. Details of suture material used.

8. Details of suturing method ‐ intervention and control.

9. Outcome data for primary and secondary outcomes (by group).

10. Duration of follow‐up.

11. Number of withdrawals (by group).

12. Assessment of risk of bias (as described below).

Where multiple reports existed for a trial, we planned to examine all the reports to obtain the maximum information relevant for the review. We sought clarification for any unclear or missing information by contacting the authors of the individual trials. If there was any doubt about whether the trials shared the same participants ‐ completely or partially (by identifying common authors and centres) ‐ we planned to contact the trial authors to check whether the trial report had been duplicated. We resolved any differences in opinion through discussion amongst the review authors.

Assessment of risk of bias in included studies

We followed instructions in the Cochrane Handbook for Systematic Reviews of Interventions to assess risk of bias in the included studies (Higgins 2011b). According to empirical evidence (Kjaergard 2001; Moher 1998; Schulz 1995; Wood 2008), we assessed the risk of bias of included trials based on the following risk of bias domains:

Sequence generation

1. Low risk of bias: the method used was either adequate (e.g. computer‐generated random numbers, table of random numbers) or unlikely to introduce confounding.

2. Uncertain risk of bias: there was insufficient information to assess whether the method used was likely to introduce confounding.

3. High risk of bias (the method used was improper and likely to introduce confounding (e.g. quasi‐randomised studies). Such studies were excluded.

Allocation concealment

1. Low risk of bias: the method used was unlikely to induce bias on the final observed effect (e.g. central allocation).

2. Uncertain risk of bias: there was insufficient information to assess whether the method used was likely to induce bias on the estimate of effect.

3. High risk of bias: the method used was likely to induce bias on the final observed effect (e.g. open random allocation schedule).

Blinding of participants and personnel

It is impossible to blind healthcare personnel who suture wounds. However, not being blinded was unlikely to result in bias provided that the personnel were not involved in any other aspect of patient care apart from suturing the skin layer of the wound. Blinding of personnel refers to healthcare personnel involved in all other patient care apart from suturing the skin layer of the wound.

1. Low risk of bias: blinding was performed adequately, or the outcome measurement was not likely to be influenced by lack of blinding.

2. Uncertain risk of bias: there was insufficient information to assess whether the type of blinding used was likely to induce bias on the estimate of effect.

3. High risk of bias: no blinding or incomplete blinding, and the outcome or the outcome measurement was likely to be influenced by lack of blinding.

Blinding of outcome assessors

1. Low risk of bias: blinding was performed adequately, or the outcome measurement was not likely to be influenced by lack of blinding.

2. Uncertain risk of bias: there was insufficient information to assess whether the type of blinding used was likely to induce bias on the estimate of effect.

3. High risk of bias: no blinding or incomplete blinding, and the outcome or the outcome measurement was likely to be influenced by lack of blinding.

Incomplete outcome data

1. Low risk of bias: the underlying reasons for missing data were unlikely to make treatment effects depart from plausible values, or proper methods have been employed to handle missing data.

2. Uncertain risk of bias: there was insufficient information to assess whether the missing data mechanism in combination with the method used to handle missing data was likely to induce bias on the estimate of effect.

3. High risk of bias: the crude estimate of effects were clearly biased due to the underlying reasons for data being absent, and the methods used to handle missing data were unsatisfactory (e.g. complete case estimate).

Selective outcome reporting

1. Low risk of bias: the trial protocol was available and all of the trial's pre‐specified outcomes that are of interest in the review have been reported or similar; if the trial protocol was not available, all the primary outcomes in this review were reported.

2. Uncertain risk of bias: there was insufficient information to assess whether the magnitude and direction of the observed effect was related to selective outcome reporting.

3. High risk of bias: not all of the trial's pre‐specified primary outcomes have been reported.

We considered trials that were classified as being at low risk of bias in all the above domains to be low bias‐risk trials. All other trials we considered to be unclear or high bias‐risk trials.

Measures of treatment effect

For dichotomous variables, we calculated the risk ratio (RR) with 95% confidence intervals (CI). For continuous variables, we calculated the mean difference (MD) with 95% CI for outcomes that can be quantified, such as length of hospital stay, and planned to calculate the standardised mean difference (SMD) with 95% CI for quality of life (where different assessment scales might have been used).

Unit of analysis issues

The unit of analysis was the surgical wound subject to the method of skin closure under investigation. While we planned to accept the results from trials in which multiple incisions were randomised to different intervention groups, we did not accept trials in which a part of the surgical incision was randomised to one group and the rest of the incision to another group. If multiple incisions were randomised to different groups, we planned to include the trial only if appropriate analysis was undertaken to take within‐subject correlation into account, or if it was possible to perform such an analysis from available data.

Dealing with missing data

We performed an intention‐to‐treat (ITT) analysis whenever possible (Newell 1992). We imputed missing data for binary outcomes using various scenarios such as best‐best, best‐worst, worst‐best, and worst‐worst scenarios (Gurusamy 2009). In the best‐best scenario, the outcomes of people with missing data from both groups were assumed to have been good. In the best‐worst scenario, the outcomes of people with missing data in the intervention group were assumed to be good, while the outcomes of the people in the control group were assumed to be bad. The worst‐best scenario was the opposite to the best‐worst scenario, in that the outcomes of people with missing data in the intervention group were assumed to be bad, while the outcomes of people with missing data in the control group were assumed to be good. In the worst‐worst scenario, the outcomes of people with missing data in both groups were assumed to have been bad.

For continuous outcomes, we used available‐case analysis. We planned to impute the standard deviation from P values according to the instructions given in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011c), and to use the median for the meta‐analysis when the mean was not available. If it was not possible to calculate the standard deviation from the P value or the confidence intervals, we planned to impute the standard deviation as the highest standard deviation in the other trials included under that outcome, fully recognising that this form of imputation would decrease the weight of the study for calculation of mean differences and bias the effect estimate to no effect in case of standardised mean difference (Higgins 2011d).

Assessment of heterogeneity

We explored heterogeneity by the Chi² test with significance set at P value 0.10, and measured the degree of heterogeneity by the I² statistic (Higgins 2002). Thresholds for the interpretation of the I² statistic can be misleading. A rough guide to interpretation is as follows (Deeks 2011).

1. 0% to 40%: might not be important.

2. 30% to 60%: may represent moderate heterogeneity.

3. 50% to 90%: may represent substantial heterogeneity.

4. 75% to 100%: considerable heterogeneity.

Assessment of reporting biases

Had a minimum of 10 trials been included in the review, we planned to explore reporting bias using visual asymmetry of the funnel plot (Egger 1997; Macaskill 2001). We planned to perform linear regression as described by Egger 1997 to determine funnel plot asymmetry.

Data synthesis

We performed the meta‐analysis using RevMan 5 software (RevMan 2011), and following the recommendations of The Cochrane Collaboration (Deeks 2011). We used both random‐effects (DerSimonian 1986), and fixed‐effect models for meta‐analyses (DeMets 1987). In case of discrepancy between the two models identified from the pooled estimates and their confidence intervals, we planned to report both results; otherwise we have reported the results of the fixed‐effect model. With regard to dichotomous outcomes, risk ratio calculations do not include trials in which no events occurred in either group in the meta‐analysis, whereas risk difference calculations do. We planned to report the risk difference (RD) if the results using this association measure were different from risk ratio in terms of statistical significance. However, risk ratio is the measure that we planned to use to arrive at conclusions, since risk ratios perform better when there are differences in the control event rate (proportion of participants who develop the event in the control groups).

Summary of findings

We have presented the 'Summary of findings' table for all the primary and secondary outcomes reported in the trials (Schünemann 2011).

Subgroup analysis and investigation of heterogeneity

We planned to perform the subgroup analyses listed below.

1. Different types of suture material.

2. Different types of surgery.

3. Trials with adults compared to trials with children.

We planned to use a P value of less than 0.05 for the Chi² test to identify the differences between subgroups.

Sensitivity analysis

We planned to perform a sensitivity analysis by excluding trials at high risk of bias. We performed a sensitivity analysis by imputing data for binary outcomes using various scenarios such as best‐best, best‐worst, worst‐best, worst‐worst scenarios as described previously (Gurusamy 2009). We also planned to perform a sensitivity analysis by excluding the trials in which the mean and the standard deviation were imputed.

Results

Description of studies

Results of the search

We identified a total of 1115 unique references through electronic searches, and excluded 1037 clearly irrelevant references through reading titles and abstracts. We sought 78 full‐text references for further assessment. We were unable to obtain four references (Farris 1981; Hamelmann 2001; Melo 1989; Soottiporn 1998) (Characteristics of studies awaiting classification). We did not identify any additional references to trials by scanning reference lists of included trials, or through other searches. We excluded 69 references because of the reasons listed in the Characteristics of excluded studies and Excluded studies sections. Five trials (five citations) met the inclusion criteria and were included in this review (Anatol 1997; Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010). The reference flow is shown in Figure 1.

1.

Study flow diagram.

Included studies

Five trials randomised a total of 827 participants (Anatol 1997; Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010), Ninety‐seven participants from four trials were excluded after randomisation (Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010), with the remaining 730 participants randomised to continuous sutures (384 participants) or to interrupted sutures (346 participants). Outcome data was available for these 730 participants.

One trial included children having surgery through groin crease incision (Anatol 1997). This trial probably included only clean surgeries. Three trials were appendicectomies (also called appendectomies), one in children (Pauniaho 2010), one in adults (Kotaluoto 2012), while the third did not specify the age of participants (Hopkinson 1982). Appendicectomies are considered to be clean‐contaminated operations. The fifth trial included participants (age not specified) having abdominal operations (McLean 1980). The contamination level in the surgeries included in this trial was variable.

Kotaluoto 2012 and Pauniaho 2010 used absorbable subcuticular sutures in the continuous suture groups and non‐absorbable transdermal sutures in the interrupted suture groups. Anatol 1997 used absorbable subcuticular sutures in the continuous suture group and absorbable transdermal sutures of different suture material in the interrupted suture group. In the McLean 1980 trial both the continuous suture group and the interrupted suture group had the same type of non‐absorbable sutures, but information about whether the sutures were subcuticular or transdermal was not reported. Hopkinson 1982 did not report the nature of the suture material used or the method of continuous or interrupted skin closure applied.

Duration of follow‐up varied between one week and 11 months.

Excluded studies

A total of 69 references were excluded. One study was quasi‐randomised (Boutros 2000). Four studies were not RCTs (Anate 1991; Anonymous 1982; Bang 1989; Knaebel 2006). Two references were comments on excluded trials (Jones 2006; Rogers 2012). In 17 studies, methods of fascial closure (layers of connective tissue that surround muscles and other structures) were investigated (Andersen 1980; Agrawal 2009; Bohanes 2002; Emi 2012; Erel 2001; Fagniez 1985; Gislason 1999; Howard 2009; Huszar 2012; Irvin 1976; Irvin 1978; Israelsson 1994; Knaebel 2005; Luck 2013; Mendoza 1966; Niggebrugge 1999; Richards 1983; Sahlin 1993; Seiler 2009; Turtiainen 2012). Two studies investigated methods of closure of other layers of the wound (Mylonas 1991; Nakamura 2013). Twenty‐two studies were not comparisons of continuous with interrupted sutures (Chen 2010; Chen 2011; Elashry 1996; Emi 2012; Ford 2005; Galal 2011; Gandham 2003; Harimoto 2011; Isik 2012; Karounis 2004; Khachatryan 2011; Leaper 1985; Lu 2012; Luck 2008; Luck 2013; Menovsky 2004; Mouzas 1975; Murphy 1995; Rasic 2011; Turner 1972; Turtiainen 2012; Vipond 1991). In 21 studies, it was not clear whether the study involved a comparison of continuous sutures with interrupted sutures (Adams 1977; Barker 1984; Clough 1975; Corder 1991; de Waard 2006; Foster 1977; Ghaderi 2010; Hansen 2009; Kakeji 2009; Karabay 2005; Lundblad 1989; Mattavelli 2013; Onwuanyi 1990; Pease 1976; Risnes 2001; Risnes 2002; Rosen 1997; Sakka 1995; Sakka 1995a; Watson 1983; Zhang 2011).

Risk of bias in included studies

All the trials were of unclear or high risk of bias as shown in Figure 2 and Figure 3.

2.

Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

3.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

Allocation

None of the trials had low risk of selection bias. Three trials had low risk of bias for random‐sequence generation and unclear risk of bias for allocation concealment (Anatol 1997; Kotaluoto 2012; Pauniaho 2010). Two trials had unclear risk of bias for random sequence generation and low risk of bias in allocation concealment (Hopkinson 1982; McLean 1980).

Blinding

All the trials were at unclear or high risk of bias due to lack of blinding of participants and healthcare providers (Anatol 1997; Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010). In one trial outcome assessors were blinded (Anatol 1997). The remaining trials had an unclear or high risk of bias due to lack of blinding of outcome assessors (Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010).

Incomplete outcome data

None of the trials was free from attrition bias. Four trials had post‐randomisation drop‐outs and so were of high risk of attrition bias (Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010). In one trial, it was not possible to determine whether there was attrition bias because the participant flow was not described (Anatol 1997).

Selective reporting

None of the five trials had a published protocol. None of the trials reported all the primary outcomes of this review. So, all the trials were at high risk of selective reporting bias.

Effects of interventions

See: Table 1

The only outcomes reported in the trials included in this review were superficial surgical site infection, superficial wound dehiscence and length of hospital stay. The other outcomes of deep surgical site infection, deep wound dehiscence, quality of life, hypertrophic scar, keloid scar, incisional hernia or the impact to the patient (in terms of return to activity and return to work) and to the healthcare funder (in terms of costs for dressings or treatment related to wound complications) were not reported in any of the trials.

The results are summarised in Table 1.

Superficial surgical site infection

Four trials reported surgical site infection (Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010). Overall, 6.5% (39/602 participants) developed superficial surgical site infection. There was no significant difference in the proportion of participants who developed surgical site infection between the two groups (RR 0.73; 95% CI 0.40 to 1.33) (Analysis 1.1). There was no change in the interpretation of results by adopting the random‐effects model or by calculating the risk difference. Sensitivity analysis showed that the results changed according to the scenario for imputation of the missing data (Analysis 1.4). There was no significant difference between the groups when the best‐best method of imputation or worst‐worst method of imputation was used. However, when the best‐worst method of imputation was used, the superficial SSI was statistically significantly lower in the continuous suture group than the interrupted suture group, while the superficial surgical site infection rate was significantly higher in the continuous suture group than the interrupted suture group when the worst‐best method of imputation was used (Analysis 1.4).

1.1. Analysis.

Comparison 1 Continuous versus interrupted skin sutures, Outcome 1 Superficial surgical site infection.

1.4. Analysis.

Comparison 1 Continuous versus interrupted skin sutures, Outcome 4 Superficial surgical site infection (sensitivity analysis).

Superficial wound dehiscence

Four trials reported superficial wound dehiscence (Anatol 1997; Hopkinson 1982; Kotaluoto 2012; Pauniaho 2010). A total of 23 participants (23/625 (3.7%)) developed superficial wound dehiscence. Of these, 22 participants belonged to interrupted suture groups. The proportion of participants who developed superficial wound dehiscence was statistically significantly lower in the continuous suture group compared to the interrupted suture group (RR 0.08; 95% CI 0.02 to 0.35) (Analysis 1.2). There was no change in the interpretation of results by adopting the random‐effects model or by calculating the risk difference. Sensitivity analysis showed that the results changed according to the scenario for imputation of the missing data (Analysis 1.5). Superficial wound dehiscence was statistically significantly lower in the continuous suture group than the interrupted suture group when the best‐best and the best‐worst methods of imputation were used, while there was no significant difference between the two groups when the worst‐best and the worst‐worst methods of imputation were used (Analysis 1.5).

1.2. Analysis.

Comparison 1 Continuous versus interrupted skin sutures, Outcome 2 Superficial wound dehiscence.

1.5. Analysis.

Comparison 1 Continuous versus interrupted skin sutures, Outcome 5 Superficial wound dehiscence (sensitivity analysis).

Hospital stay

Only one trial reported length of hospital stay in days (McLean 1980). This trial did not report the standard deviation or any other parameter from which the standard deviation could be calculated. We imputed the standard deviation to calculate the effect estimate. There was no significant difference in the length of the hospital stay between the two groups (MD ‐1.40 days; 95% CI ‐7.14 to 4.34) (Analysis 1.3). Since only one trial reported the length of hospital stay (McLean 1980), the issue of fixed‐effect versus random‐effects model did not arise. We did not perform a sensitivity analysis excluding the trial in which the standard deviation was imputed, as only one trial reported the length of hospital stay (McLean 1980). We imputed different values of standard deviation to assess the impact of imputation of standard deviation, but the results remained unchanged (no difference) (Analysis 1.6).

1.3. Analysis.

Comparison 1 Continuous versus interrupted skin sutures, Outcome 3 Hospital stay.

1.6. Analysis.

Comparison 1 Continuous versus interrupted skin sutures, Outcome 6 Hospital stay (sensitivity analysis).

Subgroup analysis

We did not perform any subgroup analyses because of the small number of trials included in this review.

Reporting bias

We did not explore reporting bias by a funnel plot because the review included fewer than 10 trials.

Discussion

Summary of main results

This review compared continuous with interrupted skin sutures for participants undergoing non‐obstetric operations. Five trials reporting data on 730 participants provided information for this review (Anatol 1997; Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010). All the participants included in these trials underwent abdominal or groin crease operations, with the majority undergoing appendicectomies. The only outcomes reported in these trials were superficial surgical site infection, superficial wound dehiscence and length of hospital stay. Overall, 6.5% (39/602 participants) developed superficial surgical site infection. There was no significant difference in the proportion of participants who developed superficial site infection between the continuous suture and interrupted suture group. A total of 23 participants (23/625 (3.7%)) developed superficial wound dehiscence. Twenty‐two of these 23 participants belonged to the interrupted suture groups. The proportion of participants who developed superficial wound dehiscence was significantly lower in the continuous skin suture group than the interrupted skin suture group (RR 0.08; 95% CI 0.02 to 0.35). Most of these wound dehiscences were reported in two recent trials (Kotaluoto 2012; Pauniaho 2010). In these trials, the exact definition used to describe wound dehiscence was not stated. However, it is likely that these partial wound dehiscences would have required wound dressings (at the very least), which would have resulted in an increased use of healthcare resources. It must be noted that in both these trials the continuous skin suture groups received absorbable subcuticular sutures, while the interrupted skin suture groups received non‐absorbable transcutaneous sutures (Kotaluoto 2012; Pauniaho 2010). These non‐absorbable sutures were removed seven to nine days after surgery, which is generally considered to be a suitable time for removal of sutures. Removal of sutures was not necessary in the absorbable subcuticular continuous suture group. The suture materials used in the continuous suture groups in these two trials were 4‐0 Poliglecaprone in Kotaluoto 2012, and 4‐0 polyglactin in Pauniaho 2010. The product manual reports that these sutures retain approximately 50% to 75% of their original tensile strength after one week in situ (Ethicon 2013a; Ethicon 2013b). This extra support for the wound after one week may be the main reason for the difference between the continuous suture group and the interrupted suture group in the proportion of participants who developed superficial wound dehiscence. The impact of this difference in superficial wound dehiscence on long‐term patient outcomes or the financial impact to the patient or healthcare funders was not reported.

Duration of follow‐up was one month or less in four of the five trials (Hopkinson 1982; Kotaluoto 2012; McLean 1980; Pauniaho 2010). Longer follow‐up periods are necessary to assess outcomes such as development of hypertrophic and keloid scarring, and incisional hernia. Future trials should use a longer period of follow‐up to assess the impact of the difference in skin suturing methods.

Overall completeness and applicability of evidence

It must be noted that most participants included in this review had appendicectomy operations for inflamed or perforated appendix, which are generally considered to be clean‐contaminated or contaminated operations (Garner 1986), so, the findings of this review are mainly applicable to such participants.

Quality of the evidence

The overall quality of evidence is low to very low as shown in Table 1. In particular, the risk of bias in the trials was high: the lack of blinding and the exclusion of participants from the analyses are of major concern and it is possible that the observed effect may not be the true effect. Blinding of outcome assessors may be difficult for early outcomes. The influence of the post‐randomisation exclusion of participants was tested by imputing outcomes for the missing participants under different scenarios. This showed that different scenarios resulted in different conclusions, and indicated a high risk of bias due to missing outcome data.

Potential biases in the review process

We have performed a thorough search of the literature without any restrictions regarding language or time of publication. In spite of this, we will not be able to identify any trials that were conducted in the pre‐mandatory trial registration era, but not reported. We included only trials in which it was clear that the comparison involved continuous versus interrupted skin sutures. As mentioned in the Excluded studies section, 20 studies were excluded because it was not clear whether they involved this comparison. Attempts to contact the authors were unproductive. While the majority of these studies are unlikely to be included in this review, some of the studies may have met the inclusion criteria for this review. The majority of these trials were old, and even the recent publications did not provide information on the impact of the different suturing methods on long‐term patient outcomes and use of healthcare funders' resources.

Agreements and disagreements with other studies or reviews

This is the first systematic review on this topic. While the authors of two trials included in this review recommend continuous absorbable sutures compared to interrupted non‐absorbable sutures (Kotaluoto 2012; Pauniaho 2010), we do not make this recommendation because of the bias in these two trials and the lack of information on long‐term patient outcomes and impact on use of healthcare funders' resources.

Authors' conclusions

Implications for practice.

Data from four trials at high risk of bias demonstrate that superficial wound dehiscence is reduced by the use of continuous subcuticular suturing. The reduction in superficial wound dehiscence was noted in the continuous absorbable subcuticular sutures compared to non‐absorbable interrupted sutures in two trials of high risk of bias. However, this reduction was observed when only when the participants excluded from the analysis in the continuous absorbable subcuticular sutures group or both the continuous absorbable subcuticular sutures and non‐absorbable interrupted sutures group were considered to have not developed superficial wound dehiscence.

Implications for research.

Differences in methods of skin closure have the potential to affect patient outcomes and use of healthcare resources. Further well‐designed trials at low risk of bias are necessary to compare continuous and interrupted skin sutures for non‐obstetric surgery. The follow‐up in such trials should be at least one year, in order to measure outcomes such as hypertrophic scar formation, keloid scar formation and incisional hernia. Such trials should include assessments of quality of life and the impact to the patient (in terms of return to activity and return to work), and to the healthcare funder (in terms of costs related to dressings or treatment related to wound complications) as outcomes, as well as short‐term wound complications.

Appendices

Appendix 1. Search strategies for Ovid MEDLINE, Ovid Embase and EBSCO CINAHL

Ovid MEDLINE

1 exp Suture Techniques/ (19242)
 2 exp Sutures/ (5335)
 3 (closure adj3 method*).tw. (805)
 4 ((interrupted or continuous*) adj3 sutur*).tw. (1243)
 5 or/1‐4 (23759)
 6 exp Wound Infection/ (15567)
 7 exp Sepsis/ (53688)
 8 exp Soft Tissue Infections/ (2029)
 9 exp Surgical Wound Dehiscence/ (3091)
 10 (surg* adj5 infect*).tw. (11653)
 11 (surg* adj5 wound*).tw. (5939)
 12 (surg* adj5 site*).tw. (8695)
 13 (surg* adj5 incision*).tw. (4515)
 14 (surg* adj5 dehisc*).tw. (409)
 15 (wound* adj5 dehisc*).tw. (1946)
 16 (deep infection* or deep sepsis or infected collection).tw. (1769)
 17 or/6‐16 (94841)
 18 5 and 17 (1983)
 19 randomized controlled trial.pt. (253655)
 20 controlled clinical trial.pt. (40653)
 21 randomized.ab. (207525)
 22 placebo.ab. (95368)
 23 clinical trials as topic.sh. (82163)
 24 randomly.ab. (142445)
 25 trial.ti. (77704)
 26 or/19‐25 (571938)
 27 (animals not (humans and animals)).sh. (1681151)
 28 26 not 27 (519938)
 29 18 and 28 (323)

Ovid Embase

1 exp suturing method/ (16996)
 2 exp suture/ (20285)
 3 (closure adj3 method*).tw. (2084)
 4 ((interrupted or continuous*) adj3 sutur*).tw. (2051)
 5 or/1‐4 (37326)
 6 exp wound infection/ (20559)
 7 exp sepsis/ (116437)
 8 exp soft tissue infection/ (5604)
 9 exp wound dehiscence/ (7462)
 10 (surg* adj5 infect*).tw. (18121)
 11 (surg* adj5 wound*).tw. (8795)
 12 (surg* adj5 site*).tw. (13741)
 13 (surg* adj5 incision*).tw. (7273)
 14 (surg* adj5 dehisc*).tw. (602)
 15 (wound* adj5 dehisc*).tw. (2881)
 16 (deep infection* or deep sepsis or infected collection).tw. (2429)
 17 or/6‐16 (181176)
 18 5 and 17 (3408)
 19 Randomized controlled trials/ (37380)
 20 Single‐Blind Method/ (16672)
 21 Double‐Blind Method/ (89945)
 22 Crossover Procedure/ (33818)
 23 (random$ or factorial$ or crossover$ or cross over$ or cross‐over$ or placebo$ or assign$ or allocat$ or volunteer$).ti,ab. (1017331)
 24 (doubl$ adj blind$).ti,ab. (95806)
 25 (singl$ adj blind$).ti,ab. (10447)
 26 or/19‐25 (1058241)
 27 animal/ (790397)
 28 human/ (9273167)
 29 27 not 28 (527005)
 30 26 not 29 (1022231)
 31 18 and 30 (536)

EBSCO CINAHL

S31 S18 AND S30
 S30 S19 or S20 or S21 or S22 or S23 or S24 or S25 or S26 or S27 or S28 or S29
 S29 MH "Quantitative Studies"
 S28 TI placebo* or AB placebo*
 S27 MH "Placebos"
 S26 TI random* allocat* or AB random* allocat*
 S25 MH "Random Assignment"
 S24 TI randomi?ed control* trial* or AB randomi?ed control* trial*
 S23 AB ( singl* or doubl* or trebl* or tripl* ) and AB ( blind* or mask* )
 S22 TI ( singl* or doubl* or trebl* or tripl* ) and TI ( blind* or mask* )
 S21 TI clinic* N1 trial* or AB clinic* N1 trial*
 S20 PT Clinical trial
 S19 MH "Clinical Trials+"
 S18 S5 AND S17
 S17 S6 OR S7 OR S8 OR S9 OR S10 OR S11 OR S12 OR S13 OR S14 OR S15 OR S16
 S16 TI ( deep infection* or deep sepsis or infected collection ) OR AB ( deep infection* or deep sepsis or infected collection )
 S15 TI wound* N5 dehisc* or AB wound* N5 dehisc*
 S14 TI surg* N5 dehisc* or AB surg* N5 dehisc*
 S13 TI surg* N5 incision* or AB surg* N5 incision*
 S12 TI surg* N5 site* or AB surg* N5 site*
 S11 TI surg* N5 wound* or AB surg* N5 wound*
 S10 TI surg* N5 infection* or AB surg* N5 infection*
 S9 (MH "Surgical Wound Dehiscence")
 S8 (MH "Soft Tissue Infections")
 S7 (MH "Sepsis+")
 S6 (MH "Wound Infection+")
 S5 S1 OR S2 OR S3 OR S4
 S4 TI ( (interrupted or continuous*) N3 sutur* ) OR AB ( (interrupted or continuous*) N3 sutur* )
 S3 TI closure N3 method* OR AB closure N3 method*
 S2 (MH "Sutures")
 S1 (MH "Suture Techniques+")

Data and analyses

Comparison 1. Continuous versus interrupted skin sutures.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Superficial surgical site infection	4	602	Risk Ratio (M‐H, Fixed, 95% CI)	0.73 [0.40, 1.33]
2 Superficial wound dehiscence	4	625	Risk Ratio (M‐H, Fixed, 95% CI)	0.08 [0.02, 0.35]
3 Hospital stay	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
4 Superficial surgical site infection (sensitivity analysis)	4		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
4.1 Best‐best scenario	4	655	Risk Ratio (M‐H, Fixed, 95% CI)	0.72 [0.40, 1.31]
4.2 Best‐worst scenario	4	655	Risk Ratio (M‐H, Fixed, 95% CI)	0.38 [0.22, 0.64]
4.3 Worst‐best scenario	4	655	Risk Ratio (M‐H, Fixed, 95% CI)	2.11 [1.31, 3.41]
4.4 Worst‐worst scenario	4	655	Risk Ratio (M‐H, Fixed, 95% CI)	1.08 [0.74, 1.58]
5 Superficial wound dehiscence (sensitivity analysis)	4		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
5.1 Best‐best scenario	4	678	Risk Ratio (M‐H, Fixed, 95% CI)	0.08 [0.02, 0.34]
5.2 Best‐worst scenario	4	678	Risk Ratio (M‐H, Fixed, 95% CI)	0.04 [0.01, 0.17]
5.3 Worst‐best scenario	4	678	Risk Ratio (M‐H, Fixed, 95% CI)	1.43 [0.86, 2.36]
5.4 Worst‐worst scenario	4	678	Risk Ratio (M‐H, Fixed, 95% CI)	0.73 [0.49, 1.11]
6 Hospital stay (sensitivity analysis)	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
6.1 Low standard deviation	1		Mean Difference (IV, Fixed, 95% CI)	0.0 [0.0, 0.0]
6.2 Medium standard deviation	1		Mean Difference (IV, Fixed, 95% CI)	0.0 [0.0, 0.0]
6.3 High standard deviation	1		Mean Difference (IV, Fixed, 95% CI)	0.0 [0.0, 0.0]

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Anatol 1997.

Methods	Randomised controlled trial
Participants	Country: Trinidad Number randomised: 128 Post‐randomisation drop‐outs: not stated Average age: not stated Male:female ratio: not stated Duration of follow‐up: 11 months Inclusion criteria: children under the age of 15 years requiring groin crease incision
Interventions	Participants randomly assigned to 2 groups: Group 1: continuous sutures (n = 76), using 3‐0 vicryl subcuticular Group 2: interrupted sutures (n = 52), using: 3‐0 plain catgut Another group to which the participants were allocated and received skin tapes was excluded from the analysis.
Outcomes	Superficial wound dehiscence
Notes	We attempted to contact the authors in February 2013
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Wounds were assigned to skin closure by one of the three methods under assessment, by the throw of a dice".
Allocation concealment (selection bias)	Unclear risk	Quote: "Wounds were assigned to skin closure by one of the three methods under assessment, by the throw of a dice"
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: this information was not available
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Post‐operatively, inspection of the wound was undertaken by an independent observer, a trained nurse (GSH), who was unaware of the method of skin closure used"
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: this information was not available
Selective reporting (reporting bias)	High risk	Comment: the protocol was not available and the published trial did not report all the primary outcomes of this review

Hopkinson 1982.

Methods	Randomised controlled trial
Participants	Country: UK Number randomised: 184 Post‐randomisation drop‐outs: 38 (20.7%) Per‐protocol population: 146 Average age: 20 years Male:female ratio: not stated Duration of follow‐up: 2 weeks Inclusion criteria: patients with acute appendicitis undergoing appendectomy
Interventions	Participants randomly assigned to 2 groups: Group 1: continuous sutures (n = 83), no further details Group 2: interrupted sutures (n = 63), no further details
Outcomes	Wound infection and superficial wound dehiscence.
Notes	We attempted to contact the authors in February 2013 Reasons for post‐randomisation drop‐outs: did not attend follow‐up (33) and protocol violations (5). The group(s) to which the post‐randomisation drop‐outs belonged were not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "After closure of the muscle layer a randomly selected sealed envelope was opened to determine the choice of skin suture."
Allocation concealment (selection bias)	Low risk	Quote: "After closure of the muscle layer a randomly selected sealed envelope was opened to determine the choice of skin suture."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: this information was not available
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: this information was not available
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: there were post‐randomisation drop‐outs
Selective reporting (reporting bias)	High risk	Comment: the protocol was not available and the published trial did not report all the primary outcomes of this review

Kotaluoto 2012.

Methods	Randomised controlled trial
Participants	Country: Finland Number randomised: 206 Post‐randomisation drop‐outs: 21 (10.2%) Per‐protocol population: 185 Average age: 41 years Male:female ratio: 80 men (43.2%):105 women (56.8%) Duration of follow‐up: 3 weeks Inclusion criteria: adult participants (over 18 years old) undergoing appendicectomy
Interventions	Participants randomly assigned to 2 groups: Group 1: continuous sutures (n = 95), using 4‐0 Monocryl subcuticular Group 2: interrupted sutures (n = 90), using 4‐0 Monosoph interrupted
Outcomes	Wound infection and wound dehiscence
Notes	We contacted the authors in February 2013; the authors provided replies to the questions in February 2013 Reasons for post‐randomisation drop‐outs: lost to follow‐up (5 in each group); did not receive intervention (3 in continuous group); discontinued intervention (1 in each group); insufficient data (1 in continuous group and 4 in interrupted group); secondary closure for fascial closure (1 in continuous group). Total 11 in continuous group and 10 in interrupted group
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The patients were then randomized into two wound closure groups by computer‐produced random numbers: the non absorbable interrupted suture (NA), and absorbable continuous intradermal suture (A) groups."
Allocation concealment (selection bias)	Unclear risk	Quote: "Then the nurse from the ER or patient's ward checked the next computer produced randomization number and according to that, informed the OR's assisting nurse of the randomization group. Thus the surgeon performing the operation wasn't aware of the group until wound closure (author replies)."
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "The patients or the healthcare providers were not blinded, since we didn't find a reliable way of blinding (author's replies)."
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote: "Of the outcome assessors the surgeons interviewing the patients on the phone were blinded. The nurse evaluating the wound after one week was not, since the same nurse removed the stitches when necessary (author's replies)."
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: there were post‐randomisation drop‐outs
Selective reporting (reporting bias)	High risk	Comment: the protocol was not available and the published trial did not report all the primary outcomes of this review

McLean 1980.

Methods	randomised controlled trial
Participants	Country: UK Number randomised: 111 Post‐randomisation drop‐outs: 6 (5.4%) Per‐protocol population: 105 Average age: 53 years Male:female ratio: 55 men (52.4%): 50 women (47.6%) Duration of follow‐up: 1 month Inclusion criteria: patients undergoing elective or emergency surgery
Interventions	Participants were randomly assigned to two groups: Group 1: continuous sutures (n = 51), using 3‐0 monofilament polyamide Group 2: interrupted sutures (n = 54), using 3‐0 monofilament polyamide
Outcomes	Wound infection
Notes	We attempted to contact the authors in February 2013 Reasons for post‐randomisation drop‐outs: died in the post‐operative period (4); fascial wound disruption due to physical trauma (1); re‐exploration for bile leak (1) (groups not stated)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: this information was not available
Allocation concealment (selection bias)	Low risk	Quote: "At this stage the patients were randomly allocated to the continuous or interrupted method of skin closure using sealed envelopes containing trial cards"
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: this information was not available
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: this information was not available
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: there were post‐randomisation drop‐outs
Selective reporting (reporting bias)	High risk	Comment: the protocol was not available and the published trial did not report all the primary outcomes of this review

Pauniaho 2010.

Methods	Randomised controlled trial
Participants	Country: Finland Number randomised: 198 Post‐randomisation drop‐outs: 32 (16.2%) Per‐protocol population: 166 Average age: 13 years Male:female ratio: 79 boys (47.6%): 87 girls (52.4%) Duration of follow‐up: 7‐9 days Inclusion criteria: children and adolescents up to 18 years of age with suspected appendicitis
Interventions	Participants randomly assigned to 2 groups: Group 1: continuous sutures (n = 79), using 4‐0 polyglactin subcuticular Group 2: interrupted sutures (n = 87), using 4‐0 nylon interrupted
Outcomes	Wound infection and wound dehiscence
Notes	We attempted to contact the authors in February 2013 Reasons for post‐randomisation drop‐outs: lost to follow‐up (19 in continuous group and 9 in interrupted group); insufficient data (2 in each group). Total of 21 drop‐outs in continuous group and 11 in interrupted group
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The randomization of the wound closure was performed by the circulating nurse at the time of wound closure by tossing a 20 cent coin."
Allocation concealment (selection bias)	Unclear risk	Quote: "The randomization of the wound closure was performed by the circulating nurse at the time of wound closure by tossing a 20 cent coin."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: this information was not available
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: this information was not available
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: there were post‐randomisation drop‐outs
Selective reporting (reporting bias)	High risk	Comment: the protocol was not available and the published trial did not report all the primary outcomes of this review

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Adams 1977	It was not clear whether this was a comparison of continuous versus interrupted sutures
Agrawal 2009	Fascial closure
Anate 1991	Not a randomised controlled trial
Andersen 1980	Fascial closure
Anonymous 1982	Not a randomised controlled trial
Bang 1989	Not a randomised controlled trial
Barker 1984	It was not clear whether this was a comparison of continuous versus interrupted sutures
Bohanes 2002	Fascial closure
Boutros 2000	Quasi‐randomised study (allocation by birth date)
Chen 2010	Not a comparison of continuous versus interrupted sutures
Chen 2011	Not a comparison of continuous versus interrupted sutures
Clough 1975	It was not clear whether this was a comparison of continuous versus interrupted sutures
Corder 1991	It was not clear whether this was a comparison of continuous versus interrupted sutures
de Waard 2006	It was not clear whether this was a comparison of continuous versus interrupted sutures
Elashry 1996	Not a comparison of continuous versus interrupted sutures
Emi 2012	Not a trial comparing continuous versus interrupted sutures
Erel 2001	Fascial closure
Fagniez 1985	Fascial closure
Ford 2005	Not a comparison of continuous versus interrupted sutures
Foster 1977	It was not clear whether this was a comparison of continuous versus interrupted sutures
Galal 2011	Not a comparison of continuous versus interrupted sutures
Gandham 2003	Not a comparison of continuous versus interrupted sutures
Ghaderi 2010	It was not clear whether this was a comparison of continuous versus interrupted sutures
Gislason 1999	Fascial closure
Hansen 2009	It was not clear whether this was a comparison of continuous versus interrupted sutures
Harimoto 2011	Not a comparison of continuous versus interrupted sutures
Howard 2009	Fascial closure
Huszar 2012	Fascial closure
Irvin 1976	Fascial closure
Irvin 1978	Fascial closure
Isik 2012	Not a comparison of continuous versus interrupted sutures
Israelsson 1994	Fascial closure
Jones 2006	Comment on an excluded trial (de Waard 2006)
Kakeji 2009	It was not clear whether this was a comparison of continuous versus interrupted sutures
Karabay 2005	It was not clear whether this was a comparison of continuous versus interrupted sutures
Karounis 2004	Not a comparison of continuous versus interrupted sutures
Khachatryan 2011	Not a comparison of continuous versus interrupted sutures
Knaebel 2005	Fascial closure
Knaebel 2006	Not a randomised controlled trial
Leaper 1985	Not a comparison of continuous versus interrupted sutures
Lu 2012	Not a comparison of continuous versus interrupted sutures
Luck 2008	Not a comparison of continuous versus interrupted sutures
Luck 2013	Both groups received the same technique (either continuous or interrupted ‐ the authors state that a standardised approach was followed with the only difference being absorbable versus non‐absorbable sutures)
Lundblad 1989	It was not clear whether this was a comparison of continuous versus interrupted sutures
Mattavelli 2013	Not clear whether there was a difference in the method of wound closure (there were differences in the suture used)
Mendoza 1966	Fascial closure
Menovsky 2004	Not a comparison of continuous versus interrupted sutures
Mouzas 1975	Not a comparison of continuous versus interrupted sutures
Murphy 1995	Not a comparison of continuous versus interrupted sutures
Mylonas 1991	Closure of all layers of the wound
Nakamura 2013	Not a trial involving different methods of skin closure
Niggebrugge 1999	Fascial closure
Onwuanyi 1990	It was not clear whether this was a comparison of continuous versus interrupted sutures
Pease 1976	It was not clear whether this was a comparison of continuous versus interrupted sutures
Rasic 2011	Not a comparison of continuous versus interrupted sutures
Richards 1983	Fascial closure
Risnes 2001	It was not clear whether this was a comparison of continuous versus interrupted sutures
Risnes 2002	It was not clear whether this was a comparison of continuous versus interrupted sutures
Rogers 2012	Comment about an excluded trial (Turtiainen 2012)
Rosen 1997	It was not clear whether this was a comparison of continuous versus interrupted sutures
Sahlin 1993	Fascial closure
Sakka 1995	It was not clear whether this was a comparison of continuous versus interrupted sutures
Sakka 1995a	It was not clear whether this was a comparison of continuous versus interrupted sutures
Seiler 2009	Fascial closure
Turner 1972	Not a comparison of continuous versus interrupted sutures
Turtiainen 2012	Continuous sutures were used in both groups
Vipond 1991	Not a comparison of continuous versus interrupted sutures
Watson 1983	It was not clear whether this was a comparison of continuous versus interrupted sutures
Zhang 2011	It was not clear whether this was a comparison of continuous versus interrupted sutures

Characteristics of studies awaiting assessment [ordered by study ID]

Farris 1981.

Methods	Awaiting full text
Participants
Interventions
Outcomes
Notes

Hamelmann 2001.

Methods	Awaiting full text
Participants
Interventions
Outcomes
Notes

Melo 1989.

Methods	Awaiting full text
Participants
Interventions
Outcomes
Notes

Soottiporn 1998.

Methods	Awaiting full text
Participants
Interventions
Outcomes
Notes

Differences between protocol and review

A new outcome "Impact to the patient (in terms of return to activity and return to work) and to the healthcare funder (in terms of costs related to dressings or treatment related to wound complications)" was added, since this outcome will permit the assessment of the impact of the difference in wound complications for participants and healthcare funders.

Contributions of authors

KS Gurusamy conceived the review question, developed and co‐ordinated the review; secured funding; completed the first draft of the review; wrote, edited and made an intellectual contribution to the review; advised on the review; approved the final version prior to submission; and acts as guarantor for the review.
 Clare Toon extracted data; made an intellectual contribution to the review; and approved the final version prior to submission.
 Victoria Allen screened the search results and identified those studies that required full‐text assessment.
 Brian Davidson conceived the review question; secured funding; made an intellectual contribution to the review; advised on part of the review; and approved the final version prior to submission.

Contributions of editorial base

Nicky Cullum: edited the review; advised on methodology, interpretation and review content.
 Andrea Nelson, Editor: Approved the final review prior to submission.
 Sally Bell‐Syer: co‐ordinated the editorial process; advised on methodology, interpretation and content; and edited the review.
 Ruth Foxlee: designed the search strategy and edited the search methods section.

Sources of support

Internal sources

• The National Institute for Health Research (NIHR) is the sole funder of the Cochrane Wounds Review Group, UK.

External sources

• National Institute for Health Research, UK.

  National Institute for Health Research, the health research wing of the UK Government Department of Health, funded K Gurusamy to complete this review.

Declarations of interest

This project was funded by the National Institute for Health Research (NIHR).

Disclaimer

Department of Health disclaimer: The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the NIHR, NHS (National Health Service), or the Department of Health.

None of the authors have any conflicts of interest.

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