From ideal to adequate: Revisiting the suture length–wound length ratio in emergency midline laparotomy closure

Abstract

A suture length to wound length (SL:WL) ratio of ≥4:1 when closing laparotomy incisions seems to help prevent incisional hernias. However, this practice is often not followed. Our prospective study of 140 patients assessed emergency midline laparotomy wound closure by surgical residents; and compared wound outcomes between those with and without a SL:WL ratio of ≥4:1. The latter was achieved in only one patient. While the incidence of wound dehiscence and of incisional hernia at six months was similar in those with a SL:WL ratio of <3 and ≥3 (p = 0.73 and p = 0.32 respectively), it was significantly higher in those with a SL:WL ratio <2.5 than ≥2.5 (p = 0.005 and p = 0.02 respectively). Even if an ideal SL:WL ratio of ≥4:1 cannot be achieved, a SL:WL ratio of ≥3 would be adequate to prevent surgeon-related wound dehiscence and incisional hernias.

Keywords

Midline laparotomy incision suture length:wound length ratio SL:WL ratio incisional hernia wound dehiscence

Introduction

Wound dehiscence and incisional hernia are the Achilles heel of the closure of midline laparotomy incisions and contribute to increased morbidity, decreased quality of life and high costs. Despite advances in surgical techniques and in suture materials, the incidence of incisional hernia may be as high as 18% and the cumulative incidence is known to increase with time.^1,2

Predisposing patient-related risk factors include: malnutrition, anaemia, hypoproteinaemia, diabetes, jaundice, renal failure, prolonged steroids, peritonitis, malignancy, prolonged postoperative abdominal distension (ileus), cough and wound infection.

It is also recognised that an excessively tight wound closure, a surgeon related factor, predisposes to wound disruption. This can be minimised by using an adequate length of suture material; which should ideally be a Suture Length to Wound Length ratio (SL:WL ratio) of 4:1 or more.^3,4 However, evidence suggests that this theoretical advice is often not followed, and this may be especially true for emergency laparotomy closures performed by trainee or junior surgeons.

The ratio, however, can act as a tool to monitor the quality of surgical technique; and standardisation of ventral midline abdominal closure could possibly be achieved by this tool.^3,5,6

Thus, we assessed if a SL:WL ratio of ≥4:1 was being achieved in closure of emergency midline laparotomy wounds, and to compare the incidence of wound dehiscence and incisional hernia in those with and without a SL:WL ratio of ≥4:1.

Methods

Ours was a prospective observational study conducted in the department of General Surgery, in a tertiary referral centre in central India, between August 2022 and May 2024. The study was conducted after receiving ethical clearance from the hospital Institutional Ethics Committee (No. IEC/2022/8629-123).

All adult patients (>18 years), undergoing emergency midline laparotomy, and who consented, were included in the study. Patients with a previous midline laparotomy scar, with current or previously repaired incisional hernia, in whom the incision needed extension away from the midline, in whom a bowel stoma was constructed, those with radiation exposure to the abdomen, those on systemic steroids/immuno-suppressants, and those who did consent for the study, were excluded.

The sample size was calculated using the formula n = Z²⋅S²/d², where Z is the standard normal deviate for 95% confidence (1.96), S is the standard deviation of suture length (20.31 cm), and d is the allowable error (3% of the mean suture length, i.e. 3.471 cm). A mean suture length of 115.7 cm was determined from a preliminary pilot study. The calculated minimum sample size was 132. To ensure adequate power, accommodate possible dropouts and allow subgroup analyses, 140 patients were recruited. This sample size ensured sufficient precision and robustness of statistical inference for key outcomes such as wound dehiscence and incisional hernia.

Pre-operatively, patient's demographic, anthropometric (age, sex, body mass index (BMI)), haematological (full blood count), and serum creatinine and albumin were recorded.

Patients with peptic perforation were also graded by the Jabalpur Prognostic Scoring System (JPSS).⁷

Reasons for intervention (hollow viscus perforation, intestinal obstruction, solid organ injury, mesenteric vascular injury, acute mesenteric ischaemia or gangrene); organ involved (stomach / duodenum, small intestine, colo-rectum, solid organs); and degree of contamination according to Center for Disease Control and Prevention criteria (clean, clean-contaminated, contaminated or dirty) were noted.

Abdominal closure was performed by trainee surgeons in their 2^nd or 3^rd year of residency, and was standardised as follows:

The length of the incision in the rectus was measured, between its ends using a plastic scale with partitions of 1 mm.

Suturing was started at one end of the incision using non-absorbable Polypropylene No. 1 on a heavy body needle. The length of the suture material between knot and needle was measured (L1).

Suturing proceeded along the length of the incision in a continuous, non-interlocking manner; with bites placed at 1 cm intervals, 1 cm from the incision wound margin.

On reaching the end of the incision, the length of suture remaining on the needle, before tying the terminating knot, was measured (L2).

An Aberdeen knot was used to finish the closure. This knot incorporated 6 throws and 1 turn.

The suture length (SL) used to close the incision was calculated by subtracting L2 from L1.

Postoperatively, the surgical wound was monitored by a strict protocol: (1) clinical assessment for wound dehiscence on days 7, 14, and 30 after surgery, graded as follows:

Partial disruption involving the skin

Partial disruption involving the skin & subcutaneous tissue

Total disruption (burst abdomen), without bowel evisceration

Total disruption (burst abdomen), with bowel evisceration

(The highest grade of dehiscence recorded was assigned to the patient.)

(2) clinical & sonographic assessment for incisional hernia at 3 and 6 months after surgery, and (3) clinical assessment for presence of surgical site infection.

Data were analysed with IBM's SPSS 23 software (IBM SPSS Statistics for Windows, Version 29.0.2.0 Armonk, NY: IBM Corp), using the student t test and the Chi-square test for quantitative and qualitative variables respectively. A p-value <0.05 was considered statistically significant.

Results

A total of 140 patients (119 males), with a mean age of 38.7 ± 16.5 years were included. Some extent of wound dehiscence was noted in 46 (32.9%), of whom 41 only had a partial (Gr I / II), and 5 had a total disruption (Gr III / IV). At the 6-month follow-up, 11 (7.8%) had developed an incisional hernia.

We observed that the ideal SL:WL ratio of >4 was achieved in only one patient which prevented any worthwhile analysis. On reducing the cutoff value, 82 patients (58%) had a SL:WL ratio <3; while on further lowering the cutoff value, 27 patients (19%) had a ratio <2.5.

Patients whose SL:WL ratio was <3 or ≥3 were comparable, in terms of the preoperative parameters, as were those with a ratio <2.5 or ≥2.5 (Table 1).

Table 1.

Comparison of preoperative parameters.

	SL:WL cutoff 3			SL:WL cutoff 2.5
Variable	SL:WL ratio <3	SL:WL ratio ≥3	p-value	SL:WL ratio <2.5	SL:WL ratio ≥2.5	p-value
Numbers of patients	82	58		27	113
Age (years)	38.12 ± 16.30	39.43 ± 16.79	0.645	38.03 ± 15.30	38.6 ± 17.05	0.625
BMI	19.05 ± 2.70	19.26 ± 3.41	0.691	18.73 ± 2.61	19.15 ± 3.15	0.152
Hb (g/l)	120.1 ± 25.6	121.1 ± 27.8	0.830	117.8 ± 18.4	123.3 ± 27.2	0.043
TLC (10⁹/l)	8.58 ± 5.50	9.93 ± 1.03	0.318	8.10 ± 4.76	9.26 ± 8.39	0.246
S. Creatinine (μmol/l)	121.1 ± 62.8	335.9 ± 67.2	0.281	119.3 ± 67.2	238.7 ± 123.8	0.521
S. Albumin (g/l)	30.4 ± 5.4	29.9 ± 5.2	0.568	30.6 ± 5.5	30.0 ± 5.3	0.669
PO Interval (h)	60.8 ± 34.2	51.8 ± 37.2	0.156	61.0 ± 34.7	55.7 ± 35.8	0.568
JPSS^a	4.89 ± 2.55	4.66 ± 2.67	0.600	5.14 ± 2.96	4.86 ± 2.63	0.619

Used for patients with peptic perforation.

When a cutoff value of 3 was applied, the incidence of wound dehiscence (31% vs 34%, p = 0.73) and of incisional hernia at 6 months (9.8% vs 5.2%, p = 0.32) was similar between those with an SL:WL ratio <3 and those with ≥3. On re-analysis using a cutoff of 2.5, patients with a ratio <2.5 had a markedly higher incidence of both wound dehiscence (55.5% vs 27.4%, p = 0.005) and incisional hernia (18.5% vs 5.3%, p = 0.02) compared to those with ≥2.5. Table 2 shows a clear rise in risk only when the SL:WL ratio threshold falls below 2.5.

Table 2.

Risk of wound complications by SL:WL ratio – a critical threshold at 2.5.

	SL:WL ratio <3	SL:WL ratio ≥3	p-value	SL:WL ratio < 2.5	SL:WL ratio ≥2.5	p-value
Number (% of the 140)	82 (58%)	58 (42%)		27 (19%)	113 (81%)
Wound dehiscence	31% of the 82	34% of the 58	0.73	55.5% of the 27	27.4% of the 113	0.005
Incisional hernia	9.8% of the 82	5.2% of the 58	0.32	18.5% of the 27	5.3% of the 113	0.02

Note: While <3 mathematically includes <2.5, the clinical risk is not evenly distributed within this group. Patients with ratios between >2.5 and 3.0 behave more like the ≥3 group, with relatively low complication rates. By contrast, those with ratios <2.5 cross a clinical “tipping point,” showing a much higher risk of wound dehiscence and incisional hernia.

The incidence of incisional hernia at 6 months was not influenced by the degree of contamination (p = 0.16) or the presence of SSI (p = 0.20), as seen in Table 3.

Table 3.

Effect of contamination on wound dehiscence and incisional hernia.

	Incisional hernia
	Present (n = 11)	Absent (n = 129)	p-value
Contamination
Gr I (n = 53)	2 (18.2%)	51 (42.5%)	0.16
Gr II (n = 87)	9 (81.8%)	78 (57.5%
SSI
Present	7 (63.6%)	43 (33.3%)	0.20
Absent	4 (36.4%)	86 (66.7%)

Discussion

The incidence of incisional hernia following closure of midline laparotomy wounds can be as high as 18%.¹ While some risk factors related to the patient and tissue status may not be alterable, the surgeon related risk factors are potentially correctable.

For the closure of elective laparotomy wounds, the guidelines of the European & American Hernia Societies recommend a continuous suturing technique with slowly absorbable, monofilament suture material, in a single-layer aponeurotic closure technique; with small tissue bites, with a SL:WL ratio of at least 4:1.^4,8 Maintaining a high SL:WL ratio to distribute tension evenly across the suture line reduces the likelihood of tissue ischaemia and wound dehiscence. This is all the more important when postoperative abdominal distension increases the wound length by up to 30%; here suturing under minimal tension enables wound lengthening without the sutures cutting through the tissue. In such circumstances, the risk of herniation is 3 times higher with a SL:WL ratio <4.^9,10

Using a mathematical model and by analysis of available literature, it was found that deep wound disruption (evisceration and ventral hernia) was associated with an SL:WL ratio of 2:1 or less – the lower the ratio, the greater the risk.⁹ A SL:WL ratio of 4:1 or more was therefore recommended. Prospective studies have identified SL:WL ratio as an independent risk factor for the development of incisional hernia, with an incidence 9.0% when it was ≥4 and 23.7% (p = 0.001) when it was <4.^10,11 Some authors even recommend a ratio of ≥6 to prevent incisional hernias in midline laparotomy wounds.¹² Certainly, the benefits of employing a ratio of ≥4 has been established in prospective trials,^6,11,13 systematic reviews¹⁴ and meta-analyses.^15,16

Despite the recognised benefits of a ratio ≥4 since the 1970s, it is still not being implemented consistently in clinical practice. In an audit in a surgical residency program, an SL:WL ratio ≥4 was achieved in 76% of cases. There was a significantly higher rate of failing to achieve a 4:1 ratio when two residents completed the fascial closure compared with one resident and one attending (p = 0.005) and compared with no residents involved (p = 0.001).¹³ This led the authors to infer that fascial closure is not being adequately taught to surgical residents and that laparotomy closure does not receive the attention it deserves, and is left unsupervised to trainee surgeons. Indeed, in a similar study, 76% of patients received a 4:1 SL:WL closure performed by residents, which improved significantly (90%; p = 0.0083) following resident education.¹⁷

The scenario is no better among experienced surgeons. An online survey of Dutch surgeons revealed that only 35% sought a ratio of 4:1, while 43% had no preference¹⁸; while 63% of a large survey of surgeons respondents reported practicing, but not measuring their SL:WL ratio as >4:1.¹⁹ Even amongst surgeons using this technique after having being trained, only 31% were able to do so in actual clinical practice.²⁰ A proprietary device has been recently developed to ensure that the SL:WL ratio of 4:1 can be uniformly and consistently achieved, eliminating subjectivity in operating.²¹

Possible reasons why guidelines have not been adopted by surgeons include lack of awareness, not being convinced by available data, and an initial inertia in adoption of the guidelines.¹⁸ Other causes could be reservations about applicability to patient population and excess time involved, lack of familiarity with the technique, and concerns about closure-related complications.¹⁹

The robustness of currently available literature may also be an obstacle in the adoption of the guidelines. European & American Hernia Societies guidelines rate the quality of available evidence as “low,” and therefore designates the strength of recommendation as “weak.”⁸ A recent meta-analysis also alludes to the low quality of evidence in the studies evaluated.¹⁶ Additionally, as all the trials had included a mix of elective & emergency laparotomies, and the European Hernia Society guidelines were specifically for closure of elective midline incisions, no recommendations were made on the optimal technique to close emergency laparotomy incisions.⁴

A SL:WL ratio of ≥4:1 can be readily achieved when many small stitches are placed at close intervals.²² That such a technique was not used in our study may have contributed to us not achieving this ratio in an overwhelming majority of cases. Some may deem this as a major shortcoming of our study, as guidelines promote a small bite technique for closure of midline laparotomy wounds.^4,8,23 However, the level of evidence has been low. The small-bites suture technique showed promise in reducing incisional hernia rates in some randomised trials and meta-analyses,²⁴ yet its long-term benefit remains unproven. Extended follow-up from the ESTOIH trial confirmed the safety of the method but found no significant advantage at either 3 or 5 years.^25,26 The EHS guideline ‘suggest’, but do not ‘recommend’ this technique as the level of evidence is weak.⁴ Similarly, ECLAPTE guidelines on closure of emergency midline laparotomy wounds ‘suggest’ that the closure be performed with a small bite technique, while acknowledging that this was extrapolated from evidence obtained from elective surgery cases; wherein the certainty of evidence was low, and thus the strength of recommendation was weak.²³

Although the technique is not difficult to learn, challenges lie in accurately judging bite and stitch distances, inconsistent application in practice, and the perception that the method is more time-consuming. Added to a lack of robust supporting data, the lack of widespread adoption of the small bite technique is not surprising.²⁰ On-going research may better define its role, but given the persisting uncertainty, we did not adopt the small-bites technique in our study, instead employing a continuous large-bite mass closure with monofilament suture, which has established reproducibility and wide acceptance in our surgical setting. Moreover, while a small bite technique may facilitate achievement of a 4:1 SL:WL ratio, it is not essential for this end.^5,6,9,11

Our study involved real-life conditions where surgical residents perform closure of emergency midline laparotomy incisions. The trainees did not receive any special instructions to achieve a SL:WL ratio of ≥4. For this reason, this ideal ratio was observed in only one of our 140 patients.

This compelled us to analyse the data with lowered cutoff levels. It was only when the cutoff was reduced to 2.5 that a significant difference was noted in the incidence of wound dehiscence and incisional hernia. This suggests that though the SL:WL ratio is likely to be significant, a level of 4:1 may not be necessary. This is borne out by a specific study on wound tension; wherein the tension rose steeply when the ratio reduced to <2.5.⁹

The incidence of incisional hernia was lower than that reported in previous studies^6,11,13 (Table 4) and could be related to the relatively short duration of follow-up of six months at which the patients were evaluated.

Table 4.

Incisional hernia in relation to the SL:WL ratio cutoff.

	Incisional hernia
	SL:WL ratio ≥4	SL:WL ratio <4	p-value
Israelson⁶	6%	22%	0.01
Israelson¹¹	9%	23%	0.001
Williams¹³	9%	26%	0.045
Present study
(cutoff 3)	5.2%	9.8%	0.32
(cutoff 2.5)	5.30%	18.51%	0.02

The limitations of our study are that it is a single centre observational study, with a relatively small number of patients, and with a short follow-up duration. However, the fact that the laparotomy closures were done by trainee surgeons who had not been coached to consciously obtain an ideal SL:WL ratio, created real-world circumstances which lends credence to our findings, and its clinical applicability.

To summarise, even if an ideal SL:WL ratio of 4 or more may not be achieved when closing emergency midline laparotomy wounds, a ratio of 3 or more would be adequately effective and safe.

Footnotes

ORCID iDs

Uday Somashekar

Dileep Singh Thakur

Deepti Bala Sharma

Dhananjaya Sharma

Author contributions

Shailendra Sahu: data collection and analysis. Uday Somashekar: conceptualisation, methodology, analysis and manuscript. Sanjay Muvel: methodology and analysis. Dileep Singh Thakur: methodology and analysis. Deepti Bala Sharma: methodology and supervision. Dhananjaya Sharma: manuscript and supervision.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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