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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.
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T. P. N. Jenkins
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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
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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
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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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