TPN Jenkins

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Br. J. Surg. Vol. 63 (1976) 873-876

The burst abdominal wound : a mechanical approach

T. P. N . J E N K I N S *

SUMMARY

The burst abdominal wound has a mechanical cause. Itis the result o f suture b reakin g, knot slipping, the intactsuture cutting out of the tissues or protrusion of gut orornentum between stitches.

Measurements of abdominal girth and the xiphoid-pubis distance before and during abdominal distensionshow that a wound may lengthen by 30 per cent if

distension occurs. An adequate reserve of suture lengthin the wound is necessary to allow this lengthening tooccur and to ensure a minimal resulting rise in tensionbetween the sutures and the tissues.

Three variables present in every continuous woundclosure-the suture length inserted, the wound fasc iallength and the number of stitches-determine the stitchinterval and the size of the tissue bite, which are thetwo vital fac tors in wound strength under the surgeon’scontrol. These variables may be expressed by the ratioo jt h e length of suture (SL) nserted to the wound length(WL), he ratio SL : WL.

Analytical and clinical evidence is presented to showthat:

I . Deep wound disruption (evisceration and ventralhernia) is associated with the use of an S L : WL ratioof

2:

or less-the lower the ratio, the greater is therisk of a burst wound.2. Wound disruption because of cutting out of

sutures can be prevented by the use of non-absorbablecontinuous sutures at I-cm intervals and an S L : WL

ratio of 4 : or more.

SURGEONSeem to have accepted as unavoidable a

continuing incidence of deep wound disruption (with

or without evisceration) of about 5 per cent in vertical

laparotomy wounds, and recent writers have con-

tinued to propound the view that neither the suture

material (Reitamo and Moller, 1972) nor the technique

used (Efron, 1965; Ferrer, 1969) is of importance. Norational explanation of the occurrence of wound

bursting has been offered and little attempt has been

made either to analyse the mechanical factors

potentially involved in disruption or to relate these

to the apparent remarkable success of some surgeons

using particular methods of avoiding burst abdominal

wounds in their own practice (Abel and Hunt, 1948;Spencer et al., 1963). A return to first principles offers

a solution to the problem, and in this paper a

theoretical analysis of the abdominal wound exposed

to distending intra-abdominal forces and the practical

application of this analysis to wound closure are

presented.

Theoretical analysisIt has been shown (Dudley, 1970) that the size of the

bite and the diameter of the suture material bear an

inverse relationship to the distribution of forces at the

suture-tissue interface. Thus, large bites with thick

sutures should have less tendency to cut out than

small bites with thin sutures. However, this statement

neglects the dynamic state of the wound after

laparotomy and the changes in tension which may

result from stretching as the abdomen distends. This

will now be considered, principally in relation to

continuous sutures.

Chan ges in girt h, xiphoid-pubis distance and woundlength

The wound fascial layers tend to lengthen as theabdomen distends. Table I gives the percentage change

in values for abdominal girth and xiphoid-pubis

distance for three distending circumstances :voluntary

inspiration, Caesarean section and paralytic ileus. In

the last two cases the values found (mean and extreme)

are such that an increase in wound length of 3 0 per

cent is a reasonable figure to select for use in further

calculations.

Table I : INCREASES IN GIRTH AND XIPHOID-

PUBIS DISTANCE CAUSED BY ABDOMINAL

DISTENSION

increase indistension

Abdom inal distension Type of Mean Extremeassociated with : measurement value value

Voluntary inspiration Girth 6 1 1

(n= 18 ) Xiphoid-pubis 12 18Caesarean section Girth 18 94

(n = 27 ) Xiphoid-pubis 1 5 36Gut obstruction or Girth 27 5 3

paralytic ileus Xiphoid-pubis 37 67( n = 5 )

Ma them atical approach to a single stitch in a con finuou ssutureConsider a length of continuous suture (Fig. 1)inserted to resemble a series of identical isosceles

triangles, thus maintaining a constant transverse

distance across the wound ( T D in Fig. 1) . Selection

of an isosceles triangle stitch pattern simplifies

calculation. By geometric use of one individual stitch,

A T B , and by dropping a perpendicular, T D , a right-

angled triangle, D T B , is defined in which D B i s half

the stitch interval and T E is half the stitch length. It is

clear that:

T D = J [ ( T E ) 2 - ( D B ) Z ] ,

and that this distance, T D (which is the sum of thetissue bites), can be related to the stitch interval and

the stitch length.

* St Luke’s Hospital, and Royal Surrey County Hospital,Guildford.

873



T. P. N. Jenkins

1

4

I

i

1

I

1

1

I

1

A

D

B

I

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I

Table 11: COMPARISON OF THE NUMBER OFEVISCERATIONS OCCURRING IN THE PERIODS

1947-56 1957-73

1947-56 AKD 1957-73

No. of No. of

Type of No. of eviscera- No. of eviscera-

incision wounds tions wounds tions

T

Upper paramedian 195 5 I1 5 0

Upper midline 204 3 323 0

Lower paramedian 106 0 369 1

Full length 2 0 38 0

paramedian

Fig. 1. Geometric use of an individual stitch, ATS, in a

continuous suture closure. A B is the stitch interval and T D

comprises the two tissue bites.

I- - - - .TD cm) 1.94 0.87 0.4 1.89 0.76 O

SL :WL 4 : l 2 : i 1 . 3: I 4 : f 2 : l 1 .3 : I

Su t u re length(cm) 40 20 13 40 2o 13

W o u n d length(cm) 10 10 10 13.3 13.3 13.3

Fig. 2. Diagrams of three 10-cm wounds each closed with a

continuous suture at a n SL : W L atio of 4 : 1, 2 : 1 or

1.3 : 1 and a stitch interval of 1 cm. Following 30 per centwound lengthening, as by abdominal distension, the stitch

interval becomes 1.3 cm.

Further, for an individual stitch of given length,

lengthening of the base of the triangle, A B , by wound

stretching must reduce T D . Reduction of T D implies

tissue compression and a rise in tension. The amount

of reduction of T D and also the rise in tension

between sutures and tissues can be calculated for any

percentage of wound stretching and for closure by any

ratio of suture length to wound length (SL : WL).

The mathematical result of stretching wounds b y 30 p ercentFig. 2 shows three 10-cm wounds closed with an over-

and-over continuous suture adjusted to appose the

cut edges but differing in the size of the tissue bites.

Total 507 8 1505 1

f = 15.81, P<O.Ol.

The stitch interval is 1 cm initially in all three,

becoming 1.33 cm when stretched by 30 per cent as by

distension. For subsequent practical application

instead of determining bite size directly it is easier to

choose an SL: WL ratio which expresses the samemeasurement. In the model (Fig. 2 ) a 4 : 1 ratio gives

a value TD of 1.94 cm, a 2 : 1 ratio 0.87 cm and a

1.3 : 1 ratio 0.4 cm. If the wound is lengthened by

30 per cent and the suture length remains (as it must)

constant the new values for T D are 1.89, 0.76 and

0 cm. Small bite continuous suturing such as with an

SL : WL ratio of 1.3 : 1 would favour wound disrup-

tion by the suture cutting through the tissues.

These observations can be generalized by plotting

the SL : WL ratio against the percentage decrease in

transverse distance T D caused by abdominal disten-

sion (Fig.3).

The shorter the suture, the smaller is the

bite of tissue and, in response to stretch, the greater

is the resulting tissue compression and rise in tension,

whatever the surgeon may think about the size of

bite at the time of wound closure. From Fig. 3 ,

SL : WL ratios of 4 : 1 or more seem ideal for main-

taining the tension between sutures and tissues at aminimum. Conversely, as the SL : WL ratio decreases

from 2.5 : the risk of wound disruption increases

and it would appear to be inevitable at an SL :WL

ratio of 1 : 1 or less.

The analysis of interrupted suture closure follows

similar but simpler lines. However, wound elongation

still lengthens the stitch interval, thus increasing therisk of protrusion of abdominal contents between

stitches. Shortening the length of the interrupted

loop in tying the knot inevitably compresses the

tissue held, so increasing the tension at the stitch site.

If the stitch is tied just to oppose the fascia1 cut edges

and the suture length in the knot and the knot tails is

ignored, for a tissue bite of 1cm (moderate size) the

stitch length is at least 4 m and this with a stitch

interval of 1 cm requires an SL :WL ratio of 4 : 1.

Clinical studies

Ratio of suture length to wound length in evisceration

and ventral herniaIf when there is an evisceration or ventral hernia a

non-absorbable suture can be recovered, its length

would provide a practical test of the SL :WL hypo-

thesis outlined above. A less direct comparison can

874



The burst abdominal wound

Table 111: STITCH INTERVAL, STITCH LENGTH AND SL : W L OF 127 W O U N D C L O S U R E S IN 1971

TvDe of incision

Upper Upper, Lowermidline paramedian paramedian Transverse

No. of wounds measured 25 57 40 5Mean stitch interval (cm) 1 . 1 1 .3 1 . 3 1 . 1

Mean stitch length (cm) 5 . 8 4.8 4.6 4.3

Mean S L : W L 5 .3 : 1 4.9 : 1 3. 5 : 1 3.8 : 1

also be attempted for absorbable sutures if the operator

reinserts a suture to resemble the initial closure,

removes i t for measurement, measures the wound and

then proceeds to a definitive and more appropriate

wound closure. Data of both kinds are obviously

difficult to collect, but in 7 cases that have been

studied (evisceration 3, ventral hernia 4) the SL :WL

ratio was less than 2 : 1, the mean was 1.3 : 1 and the

lowest ratio was 0.9 : 1.

Abdominal wound closure with cont inuous non-absorbable sutures

Between 1947 and 1973, 2012 vertical incisons have

been closed with continuous non-absorbable sutures

using a stitch interval of about 1 cm by the author

and his associates (Table ZZ). The material was nylon

(metric 3) looped on a needle (Everett, 1970).

In the period 1947-56 the tendency was to suture

rather tightly, probably at an SL : W L ratio of about

2 : 1 , and there were 8 eviscerations as a consequence

of the intact suture cutting out.

From 1956 a large bite, slack suture technique was

developed based on an SL : W L ratio of around 4 : 1.In this second series, 1957-73, only one evisceration

occurred from cutting out. That this value 4 : 1 was

in fact realistic was checked in 1971 by analysing a

series of 127 consecutive wound closures for stitch

interval, suture length and wound length, and thus

the ratio of S L : W L (Table ZZZ). These data hide a

biphasic distribution (F i g . 4) of the ‘tighter’ wounds

closed by registrars and the ‘looser’ closure of the

more experienced surgeon. Nevertheless, the usual

ratio for the latter is in the zone 3 : 1 to 6 : 1 which

conforms with the theoretical value.

Although to apply statistical analysis to a con-

secutive series isnot entirely appropriate, the differencebetween the evisceration rates in the two periods

1947-56 and 1957-73 is statistically significant

(Table Zl).

Discussion

Adequate strength of suture material will prevent

suture breakage, efficient knots will prevent knot

slippage and a sufficiently small stitch interval will

prevent protrusion of abdominal contents into the

intact wound. Prevention of sutures cutting out will

not be possible until the cause is recognized.

As yet there is little scientific basis on which a

surgeon can make his choice of closure technique;it is made largely on a basis of custom, teaching or

recommendation. The expressions ‘tight’ and ‘loose’

suturing and ‘small’ and ‘large’ tissue bites have no

accurate meaning unless they refer to measured

50

40

hT

30

0CI

cE

0.-!4

s 20I-

10

I .o 2.0 3:O 4:O 510

SL : W L

Fig. 3. Graph showing the relationship between the rise intension between sutures and tissues caused by a 30 per centwound stretch and the S L : W L ratio.

251

SL :W L

Wound s c losed b y consul tant.....Wound s c losed by registrars..Fig. 4. Frequency histogram of the distribution of theSL :W L ratio in 127 measured abdominal closures.

quantities, and few surgeons have applied measure-

ments to wound closure. Abel and Hunt (1948) used

a I-cm tissue bite, but did not measure the stitch

interval; Spencer et al. (1963) used a 1-cm stitch

a75



T. P. N. Jenkins

interval and a 3-cm tissue bite but did not measure

the suture length actually inserted (calculation ofSL :WL for their data suggests a value of 12 : 1).

The simple calculations described in this paper

provide a basis for rational wound closure: a low

incidence of dehiscence (0.007 per cent) was obtained

when sutures were inserted so that the length of thesuture material was greater than four times that of

the wound. Conversely, lower ratios are associated

with high incidences of disruption.

Future studies of abdominal wound dehiscence

should incorporate quantitative observation of the

amount of suture material used in relation to the

length of wound and must also use as the standard of

comparison the low incidence that can be achieved

by the technique used here. Such a monofilament

closure not only gives almost complete protection

from dehiscence but also acts as an inert buried tissue

splint whose strength is unaffected by sepsis. Though

persistent wound sinuses occurred in 3 per cent of theseries between 1947 and 1956, the looser sutures now

inserted and attention to cutting the tails of the knots

flush have subsequently reduced this to 0.07 per cent.

Acknowledgements1 would like to acknowledge that nylon as a loop on

the needle was introduced by Ted Moloney and

Gordon Gill in 1945 and that I was taught the

technique by the latter. I am grateful to Sister FieIdus

who collected the measurements at Caesarean section,

to Colin Binks for guidance in the mathematical

analysis of wound measurements and to Professor

H. A. F. Dudley for his kind help in the final drafting

of this paper.

ReferencesABEL A. L . and H U N T A . H . (1948) Stainless wire for

closing abdominal incisions and for repair ofherniae. B r. Med. J . 2, 379-382.

D U D L E Y H . A . F . (1970) Layered and mass closure of

the abdominal wall. A theoretical and experi-

mental analysis. B r. J . Surg. 57, 664-667.

EFRON G. (1965) Abdominal wound disruption. Lancet1, 1287.

EVERETT w. G. (1970) Suture materials in general

surgery. Prog. Surg. 8, 15-37.

FERRER R . 0. 1969) Wound disruption after abdominallaparotomies. M d State Med. J . 18, 57-60.

REITAMO J. and MOLLER c. (1972) Abdominal wound

dehiscence. Acta Chir. Scand. 138, 170-1 75.

SPENCER F. R . , SHARP E. H. and JUDE J . R . (1963)

Experiences with wire closure of abdominal

incisions in 293 selected patients. Surg. Gynecol.Obstet. 117, 235-238.

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