Topics in Medicine and Surgery

Topics in Medicine and Surgery

Suture Materials and Suture Selection
for Use in Exotic Pet Surgical Procedures

Michael S. McFadden, MS, DVM, Dip. ACVS

Abstract

Exotic animals are becoming increasingly popular and more exotic pet owners are
seeking veterinary care. This has led to a demand for properly trained veterinarians
who are capable of providing quality, up-to-date medical and surgical treatments.
Many surgeries are now performed on exotic pets, and selection of the appropriate
suture material is an important part of the treatment protocol. An understanding of
different available suture materials, healing times of different tissues, and knowl-
edge of different anatomic and physiologic characteristics in different species is
important in the selection of the most appropriate suture material. This review will
summarize important aspects of suture selection in exotic animals. Copyright 2011
Elsevier Inc. All rights reserved.

Key words: biomaterials; exotics; surgery; suture materials

E

xotic pets have increased in popularity, with
estimates of up to 70 million of these animals
being maintained in US households.

1

The

groups of animals that comprise companion exotic
animals include ornamental fish, amphibians, rep-
tiles, birds, rabbits, rodents (e.g., hamsters, gerbils,
guinea pigs, mice, rats), and ferrets. The rise in pet
ownership of companion exotic species has also in-
creased the need for veterinarians to treat these
animals. A 2006 survey estimated that over US $530
million were spent on veterinary services for exotic
pets and birds.

2

It is the responsibility of the veteri-

narian to become knowledgeable in anatomic and
physiologic traits specific to each group to provide a
level of care comparable with that for common do-
mestic species (e.g., dogs, cats). In the early stages of
exotic pet practice, known procedures and tech-
niques were adapted from canine and feline medi-
cine for use in exotic species. Currently, there are
associations, journals, and conferences aimed at pro-
viding up-to-date, accurate information specific to
exotic species, thereby elevating the quality of exotic
pet practice.

3

The increase in scientific medical stud-

ies performed specifically with exotic species has

decreased the need to adapt treatments from domes-
tic species and provides opportunities to use specific
treatments and techniques developed and/or vali-
dated for these particular animals.

Suture materials play an important role in veteri-

nary surgery, but specific details regarding their se-
lection and use are often overlooked. A single suture
type may not be appropriate for all applications;
therefore, veterinarians must be familiar with several
suture types for different surgical situations. With
the exception of rodents and rabbits, there are rel-
atively few studies specifically examining suture ma-
terials in exotic pets. This review will summarize the
most commonly available suture materials and dis-

From the University of Illinois, Department of Veterinary Clin-

ical Medicine, Urbana, IL USA.

Address correspondence to: Michael S. McFadden, MS, DVM,

University of Illinois, Department of Veterinary Clinical Medicine,
1008 W. Hazelwood Drive, Urbana, IL 61802. E-mail:

mikem.

[e-mail]

.

© 2011 Elsevier Inc. All rights reserved.
1557-5063/11/2003-$30.00
doi:10.1053/j.jepm.2011.04.003

Journal of Exotic Pet Medicine, Vol 20, No 3 ( July), 2011: pp 173–181

173

cuss their selection for exotic pet procedures, con-
centrating on studies performed specifically on com-
panion exotic species.

Suture Materials

The role of sutures is to maintain incised or injured
tissue in apposition, thus allowing the tissue to
heal.

4-6

The ideal suture material would provide high

tensile strength for a sufficient time to allow the
tissue to heal, have good knot security, resist infec-
tion, and cause no inflammatory, immunogenic, or
carcinogenic reactions. The reaction of tissue to su-
ture material depends on several variables such as
the type, quantity, and duration of suture implanta-
tion as well as the tissues into which the suture
material is implanted.

Surgeons must be familiar with different suture

materials to make the most appropriate choice for
specific clinical situations.

7

It is important to have a

thorough understanding of a specific tissue’s healing
time, the knowledge that the suture will retain suffi-
cient tensile strength to support the tissues as they
heal, and the amount of time to complete suture
absorption. The suture material selected for a spe-
cific procedure may affect wound healing, functional
outcome, and cosmetics. The number of suture types
available to the veterinary surgeon has increased
dramatically, and each suture type has specific phys-
ical, handling, and tissue reaction characteristics.
Sutures are classified in many ways based on their
ability to be absorbed and whether they are single
stranded or braided.

Absorbable suture materials are defined as materials

that lose their tensile strength within 60 days of implan-
tation.

8

These sutures are either composed of different

synthetic polymers or are of biologic origin. Absorb-
able sutures that are biologic in origin are broken
down by phagocytosis, whereas synthetic polymers are
absorbed by hydrolysis. Hydrolysis involves breaking
down polymers into monomers by direct water cleav-
age; once broken down the monomers are then ab-
sorbed and metabolized by the body.

8

Common ab-

sorbable sutures include chromic gut, polydioxanone
(PDS), poliglecaprone 25 (Monocryl), polyglactin 910
(Vicryl), polyglyconate (Maxon), glycomer 631(Bio-
syn), polyglycolic acid (Dexon), polyglytone 6211
(Caprosyn), and lactomer (Polysorb).

Chromic gut is a monofilament absorbable suture

composed of purified connective tissue (primarily
collagen) derived from either bovine or ovine intes-
tine and is absorbed by the action of macrophages
through phagocytosis and enzymatic digestion.

4,5

Chromic salts are used to coat the suture to assist in

the delay of absorption, increase tensile strength,
and decrease tissue reactivity. Chromic gut is rapidly
absorbed in mammals, is completely absorbed in
approximately 60 to 90 days, and only maintains
tensile strength for 7 to 10 days.

7

Chromic gut has a

tendency to have a more pronounced inflammatory
response compared with other absorbable sutures,
thus making it less desirable in species prone to
developing adhesions (e.g., rabbits).

Synthetic absorbable sutures are all composed of

monomers or polymers. The type of monomer af-
fects the strength, flexibility, and speed at which the
suture is absorbed. Monomers used in most of the
currently available suture material include glycolide,
lactide, p-dioxanone,

␧-caprolactone, and trimethely-

ene carbonate. Glycolide and lactide contribute to
the resulting strength of the suture, whereas

␧-cap-

rolactone and trimethelyene carbonate contribute
to increased flexibility. P-dioxanone contributes to
the suture material by providing moderate strength
and flexibility. By combining these monomers in
different proportions, desired properties of specific
suture material are obtained.

Polydioxanone is a monofilament absorbable suture

composed of polymerized p-dioxanone.

7

Polydiox-

anone elicits minimal reaction, is slowly absorbed, and
maintains tensile strength for an extended period of
time. Polydioxanone maintains 70% of its tensile
strength at 2 weeks, 50% at 4 weeks, and 25% at 6
weeks, with complete absorption in approximately 180
days.

4,5,7

Initial tensile strength for PDS is greater than

chromic gut, Dexon, or Vicryl, but it has the poorest
knot security of the synthetic absorbable sutures.

9

Poly-

dioxanone is useful when prolonged support of heal-
ing tissue is desired.

8

Monocryl is a monofilament absorbable suture com-

posed of segmented block copolymers of

␧-caprolac-

tone and glycolide.

10

Soft segments of

␧-caprolactone

and glycolide contribute to favorable handling charac-
teristics, and hard segments of polyglycolide contribute
to tensile strength. Monocryl is one of the strongest
absorbable sutures, although it rapidly weakens after
implantation.

8

Fourteen days after implantation, only

20% to 30% of Monocryl’s initial tensile strength is
maintained, and complete absorption occurs between
90 and 100 days.

5,10

Vicryl is a multifilament suture composed of a

copolymer of lactic acid and glycolic acid that is
coated with calcium stearate and a second copoly-
mer of glycolide and lactide. The braided nature of
this suture results in good handling properties but
also increases tissue drag.

7

Tensile strength of Vicryl

is approximately 75% at 2 weeks and only 50% at 3
weeks, with complete absorption in approximately

174

McFadden

60 days.

4,5,7,11

Vicryl rapidly loses 50% of its initial

tensile strength in 5 days and 100% of its tensile
strength in 10 to 14 days; complete absorption oc-
curs in approximately 42 days.

8

Vicryl is designed for

rapidly healing tissues where long-term support is
not required.

Maxon is a monofilament suture composed of

copolymers of glycolide and trimethelyene carbon-
ate. The tensile strength of Maxon is approximately
80% at 1 week, 75% at 2 weeks, 50% at 4 weeks, and
25% at 6 weeks, with complete absorption at 180
days.

8

Biosyn is a monofilament suture composed of syn-

thetic polyesters with segments of glycolide and diox-
anone alternating with segments of trimethelyene car-
bonate and dioxanone. Biosyn retains 75% of its tensile
strength at 2 weeks and 40% at 3 weeks, with complete
absorption occurring between 90 and 110 days.

Dexon is a braided suture composed of the ho-

mopolymer of glycolic acid and coated with polycap-
rolate.

8

Polycaprolate is a copolymer of glycolide and

␧-caprolactone. Dexon is rapidly absorbed and quickly
loses tensile strength. Fourteen days after implantation,
Dexon only has 20% of its initial tensile strength; it is
completely absorbed in 60 days.

Caprosyn is a newer monofilament absorbable su-

ture composed of a synthetic polyester of glycolide,
caprolactone, trimethylene carbonate, and lactide.

12

Caprosyn provides short-term tensile strength com-
bined with the benefits of rapid absorption. Seventy
percent to 80% of Caprosyn’s tensile strength is lost in
10 days and it is completely absorbed in 56 days.

13

Polysorb is a braided suture composed of polymers

of glycolide and lactide. Polysorb is coated with

␧-cap-

rolactone glycolide and calcium stearoyl lactylate to
improve handling properties. Polysorb retains 80% of
its tensile strength at 2 weeks and 30% at 3 weeks, with
complete absorption between 56 and 70 days.

Nonabsorbable suture materials do not undergo

significant degradation after implantation. These su-
tures are used where extended wound support is
required or in areas where suture removal is ex-
pected (skin closure). Nonabsorbable sutures, as
with absorbable sutures, are composed of natural or
synthetic fibers. Natural fibers tend to invoke pro-
found inflammatory reactions. Thus, there may be a
preference for synthetic nonabsorbable sutures de-
pending on the application. Nonabsorbable suture
materials commonly used in veterinary surgery in-
clude silk, nylon (Ethilon, Monosof, Nurolon, Supra-
mid), polypropylene (Prolene, Surgipro, Fluorofil),
and stainless steel.

Silk is the most commonly used organic nonab-

sorbable suture material.

5,8,11

It is a braided suture

with excellent handling properties and knot security.
Silk loses a significant amount of its tensile strength
after an extended period of implantation but is con-
sidered nonabsorbable because the material remains
in the tissues for a significant amount of time. There
is a 30% loss of tensile strength at 14 days and 50%
loss at 1 year. Time for complete absorption is
greater than 2 years. Silk leads to significant reaction
in tissues, and the presence of silk suture can reduce
the number of bacteria needed to induce an infec-
tion from 10

6

to 10

3

.

11

Silk is the most commonly

used suture material in cardiovascular surgical pro-
cedures.

Nylon is a synthetic nonabsorbable suture that is

available as a monofilament or braided suture.

5,7,8,11

Nylon maintains a high level of elasticity but under-
goes little to no plastic deformation before breakage,
and monofilament nylon is relatively stiff. Overall
nylon has moderate handling characteristics and
knot security, but induces minimal tissue response.
Multifilament nylon has improved handling charac-
teristics but increased capillarity. Although it is non-
absorbable, monofilament nylon loses 30% of its
tensile strength after 2 years and braided nylon loses
75% to 100% of its tensile strength at 6 months.

Polypropylene is a synthetic monofilament non-

absorbable suture material composed of stereo iso-
mers of polypropylene.

8

Polypropylene has the great-

est strength of the synthetic nonabsorbable sutures
and has no appreciable loss of tensile strength after
implantation

8

; however, there was evidence of frag-

mentation when polypropylene sutures were evalu-
ated over periods of 2 and 5 years.

14,15

Polypropylene

has a very smooth surface and minimal tissue drag,
but this can lead to slipping and poor knot security.

7

Other disadvantages of polypropylene are the han-
dling properties and memory.

Stainless steel is an alloy of chromium, nickel, and

molybdenum and is available as a monofilament or
braided suture.

8,11

It is biologically inert and has the

greatest strength of all suture materials. Stainless-
steel sutures are extremely stiff and tend to cut
through tissues or cause necrosis when there is tissue
movement over buried knots.

Tissue Healing

In addition to understanding specific characteristics
of all available suture materials, it is important to
understand differences in tissue healing. Different
tissue types heal at dissimilar rates and this translates
into varying amounts of time for which the sutures
are required to support the tissue while it mends.
Compared with other tissues, the bladder heals very

Sutures in Exotic Pet Surgery

175

quickly and regains normal tensile strength in 14 to
21 days.

16

When choosing a suture material to use for

bladder repair, Monocryl, Biosyn, Dexon, or Vicryl
may be recommended based on the amount of time
these suture materials retain sufficient tensile strength,
thus allowing the bladder tissue to heal. Longer-lasting
absorbable sutures such as Maxon or PDS are probably
not required for bladder surgery unless delayed heal-
ing is anticipated, whereas nonabsorbable sutures may
promote calculi formation. Conversely, sutures that are
absorbed very rapidly (e.g., Caprosyn, Vicryl) probably
do not retain sufficient tensile strength long enough
and may increase the risk of dehiscence.

The gastrointestinal tract also heals at a relatively

rapid rate, with the strength of the repair site ap-
proximating the original tissue strength in 10 to 17
days for the small intestine and up to 30 days in the
large intestine.

17,18

The maturation phase in gastro-

intestinal tract healing occurs between 10 and 180
days after surgery. Polydioxanone, Monocryl, Biosyn,
or Maxon provide sufficient tissue support for the
gastrointestinal tract to allow for adequate healing.

Healing times for fascia are longer than for the

gastrointestinal tract or urinary tract; therefore, fas-
cia requires prolonged tissue support. Twenty days
after surgery the body wall has only regained 20% of
its original tensile strength.

19

Because fascia has

slower healing times, suture materials that will pro-

vide longer support of the tissues (e.g., PDS, Maxon)
are recommended. Tissues such as tendons can take
6 weeks to a year to completely heal and require
long-term support with orthopedic implants or ex-
ternal coaptation in addition to sutures.

20

When re-

pairing tissues that take an extended period of time
to heal, longer-lasting sutures such as PDS or Maxon,
or nonabsorbable sutures like Prolene, should be
used.

Table 1

provides a summary of tissue healing

times and suture absorption profiles.

Sutures in Exotic Pets

Rodents

Because of the extensive use of rodents in research,
suture reaction in rodent species has been exten-
sively studied, with investigations evaluating many
suture types that are used in specific applications.
Rats have been studied in great detail to compare
suture materials for optimum use in the body wall,
subcutaneous tissues, skin, urogenital tract, gastroin-
testinal tract, and oral cavity. The scientific investi-
gations that are referred to in this article are primar-
ily comparison studies in which commonly available
suture materials are used. Studies that evaluated ex-
perimental biomaterials not currently available to
the general veterinary practice were excluded.

Table 1. Percentage of retained tensile strength after implantation and number of days
required for complete absorption for commonly available suture materials in mammals.

Ranges in healing times are shown for different tissues

Suture material

7 Days

14 Days

21 Days

28 Days

42 Days

Complete

absorption

Chromic gut

0

60-90 days

Polydioxanone (PDS)

70

50

25

180-210 days

Polyglyconate (Maxon)

80

75

65

50

25

180 days

Glycomer 631 (Biosyn)

75

40

90-110 days

Polyglecaprone 25 (Monocryl)

60-70

30-40

90-120 days

Polyglycolic acid (Dexon)

20

60 days

Polyglactin 910 (Vicryl)

75

50

25

56-70 days

Lactomer (Polysorb)

80

30

56-70 days

Polyglytone 6211 (Caprosyn)

50-60

20-30

0

56 days

Polyglactin 910 (Vicryl Rapide)

50

0

42 days

Bladder

X---------------X

Gastrointestinal tract

X---------X (SI)

X------------------------------------X (LI)

Fascia

X----------------------------------------X

Abbreviations: SI, Small intestine; LI, large intestine.

176

McFadden

A study evaluating Maxon, Vicryl, chromic gut,

and PDS in the body wall of rats showed that the use
of Maxon and PDS resulted in significantly less in-
flammation than Vicryl and chromic gut 28 days
after implantation.

21

When Caprosyn was compared

with Monocryl in the body wall of rats, there was no
significant difference in the inflammatory response
2 or 10 days after implantation.

13

Comparison of

Monocryl, Vicryl, and polytetrafluorethylene (Tef-
lon) in subcutaneous tissues showed that Monocryl
caused significantly less inflammation 48 hours after
implantation than Vicryl and Teflon, and Teflon
sutures caused significantly more fibrosis 7, 14, and
21 days after implantation.

22

A study comparing Vi-

cryl, catgut, silk, and polypropylene in the skin
showed that Vicryl caused significantly less inflam-
mation than all other sutures over a period of 7
days.

23

Comparison of PDS, Monocryl, and Biosyn in

rat skin showed that Monocryl and Biosyn were less
reactive than PDS, but all 3 were acceptable because
of extremely low reaction scores.

24

When Caprosyn

was compared with chromic gut for skin closure in
rats, Caprosyn had significantly less tissue drag and
less potentiation of infection when surgical wounds
were inoculated with Staphylococcus aureus.

12

Several studies have also been performed compar-

ing suture materials in the urogenital tracts of rats
with the aim to evaluate inflammation, fibrosis, and
adhesion formation. A comparison of Vicryl and
Dexon in uterine tissue showed that there was sig-
nificantly less inflammation and fibrosis with Vicryl
90 days after implantation.

25

Another study evaluat-

ing suture material in uterine tissues compared
Dexon, Vicryl, PDS, silk, and Prolene. The results
showed that PDS had the lowest reaction scores and
Prolene led to the highest rate of granuloma forma-
tion.

26

Evaluation of inflammatory reactions to

Prolene, Vicryl, and catgut, and their role in adhe-
sion formation, showed that Prolene had the lowest
inflammatory score followed by Vicryl and catgut, but
no correlation to adhesion formation was found.

27

Su-

ture reaction in bladder tissue has also been evalu-
ated to determine differences in inflammation and
calculogenic potential. An early study showed that
there was no difference in calcification around
Dexon or chromic gut sutures in sterile or infected
rat urine; however, the presence of infection did
decrease the time that both suture types remained
within the bladder wall.

28

When PDS, Vicryl and

chromic gut were compared in bladder tissue over a
period of 24 weeks, PDS had the greatest initial
inflammatory response 7 days after implantation.

29

No difference was seen in inflammatory response
among suture types at later time points. There was

no difference in calculogenic potential among these
suture types over a 6-month period. A similar study
also compared PDS, Vicryl, and chromic gut and
found that inflammation and stone formation were
greater for chromic gut and Vicryl compared with
PDS.

30

Studies comparing suture materials in the gastro-

intestinal tract have also been performed. The use of
Dexon and catgut was compared in rat colonic anas-
tomoses, and there was no difference in the degree
of inflammation or strength of the anastomosis
site.

31

Another study comparing Vicryl and PDS in

colonic anastomoses did not show any significant
differences despite the belief that the multifilament
nature of the Vicryl in contaminated tissue could
lead to more inflammation or abscess formation.

32

A

third study evaluated Dexon, silk, Vicryl, chromic
gut, Prolene, and PDS in wounds inoculated with
bacteria commonly found in the colon. This study
determined that monofilament absorbable sutures,
with the exception of PDS, lose strength too quickly
and are not recommended for colonic surgery. In
addition, braided materials, especially silk, harbored
bacteria and led to prolonged inflammation.

17

Rabbits

As with rats, rabbits have been used as a model to
evaluate biomaterials and techniques for use in human
surgery. Several studies comparing suture materials in
rabbit urogenital tracts have been performed. Com-
parison of Vicryl, Polyethylene, and nylon in rabbit
uteri showed that Vicryl had a lower inflammation
score at 24 days, and 80% of samples were absorbed
by 80 days with little residual inflammation. The
nylon sutures were present at 80 days and caused a
persistent inflammatory response.

33

A similar study

comparing Vicryl, Dexon, Prolene, nylon, and chro-
mic gut in rabbit uterine tissue found that Vicryl had
the lowest short-term (16 days) and long-term (42
days) tissue reactions. As in other studies, the non-
absorbable sutures remained in the tissues and
caused a persistent inflammatory response.

34

An-

other study showed that there was no difference in
the histologic reaction or pregnancy rates between
Vicryl and Prolene in microsurgical anastomoses of
rabbit oviducts.

35

Comparison of chromic gut, Vicryl,

PDS, and Maxon in rabbit pyeloureterotomies
showed that chromic gut caused the most severe
inflammatory reaction. The reactions to the syn-
thetic absorbable sutures were similar, but there was
suture remaining in 50% and 100% of pyeloureter-
otomies closed with PDS and Maxon, respectively, 12
weeks after implantation.

36

Sutures in Exotic Pet Surgery

177

A study comparing gut, chromic gut, Vicryl, and

Prolene in rabbit bladder tissue found that the gut and
chromic gut had the highest inflammation scores fol-
lowed by Vicryl and Prolene. Fifteen weeks after
implantation, the gut sutures and Vicryl were almost
completely absorbed, with little residual inflammation
compared with Prolene.

37

Another study evaluating

suture material in rabbit bladders compared chromic
gut, PDS, and Prolene. Bladders were evaluated for
calculi at 15, 30, 60, and 90 days, and calculi formed on
all sutures. The persistence of the calculi was depen-
dent on the longevity of the suture material.

38

Ferrets

A single case report exists pertaining to suture material
use in ferrets.

39

An intraabdominal malignant mesen-

chymoma was removed from a 6-year-old spayed fe-
male ferret. The mass originated at the area of the
previous ovariectomy performed 60 months earlier.
Histopathologic examination showed a mixed popula-
tion of neoplastic cells and nonabsorbable suture ma-
terial was admixed with the neoplastic tissue. A chronic
inflammatory reaction to the suture may have played a
role in tumor development. Unfortunately, the type of
suture implanted was not determined.

The studies performed on rodents and rabbits show

that in most cases chromic gut is more reactive than
synthetic absorbable sutures. Nonabsorbable suture
materials tend to cause chronic inflammatory re-
sponses, whereas absorbable suture materials leave lit-
tle residual inflammation after they are broken down.
These studies and other investigations involving do-
mestic species demonstrate the importance of choos-
ing suture material that will retain tensile strength only
long enough for the tissues to heal. Any suture that
remains after the tissue is healed can lead to the for-
mation of granulomas and uroliths, or can possibly
lead to malignant transformation of the tissues.

Birds

Despite their popularity and the increasing fre-
quency with which veterinary care is pursued,

40

only

a single study exists evaluating suture materials in
birds. In this study the histologic reaction to 5 suture
materials (chromic gut, PDS, Vicryl, monofilament
nylon, and stainless steel) was evaluated in rock
doves (Columba livia) over a period of 120 days.

41

Vicryl caused an early and intense inflammatory re-
sponse and had higher inflammation scores than all
other suture types. Chromic gut also caused an early
and sustained inflammatory response. Initially, PDS
caused minimal reaction, but there was an increase
in inflammation between 60 and 90 days. Steel and
monofilament nylon stimulated minimal inflammatory

reaction but led to hematomas, seromas, and case-
ogranulomas. Based on this study, PDS is the optimal
suture because of the minimal inflammatory response
and lack of the complications seen with stiff nonab-
sorbable sutures. Interestingly, the author of that study
prefers Vicryl for skin closure in birds because the soft
suture is less irritating and quickly absorbed (Avery
Bennett, personal communication).

Reptiles and Amphibians

A few scientific investigations have evaluated the use
of suture material in reptiles and amphibians. A
single study exists evaluating suture materials in am-
phibians.

42

Five suture materials (silk, monofilament

nylon, PDS, Vicryl, and chromic gut) were evaluated
in African clawed frogs (Xenopus laevis) to determine
which suture material(s) elicited the fewest inflam-
matory changes in amphibian skin over 14 days. All
sutures caused significantly more inflammation than
a stab incision that was left to heal by second intention.
Chromic gut and silk caused significantly more inflam-
mation than all other sutures, and 67% of incisions
closed with silk sutures dehisced. Polydioxanone and
Vicryl caused significantly more inflammation than
monofilament nylon. There were no significant differ-
ences in scores between 7 and 14 days. Based on these
results, the use of chromic gut and silk is not recom-
mended and monofilament nylon may be the most
appropriate suture in amphibian skin.

Early studies on wound healing in reptiles com-

pared sutured and unsutured wounds in garter
snakes.

43

Paired 1-cm incisions were either sutured

with 5-0 Prolene or left to heal by second intention.
Unsutured wounds had significantly less disruption
of scale pattern and overlap of wound margins, and
less intense inflammatory infiltrates.

Four different suture materials (chromic gut,

Maxon, Vicryl, and Monocryl) were evaluated histo-
logically 7 days after laparoscopic sex determination
in loggerhead sea turtles (Caretta caretta).

44

Results

indicated that Monocryl and Maxon caused the least
tissue reaction of the 4 suture types examined. These
synthetic monofilament absorbable suture materials
caused significantly less crust formation and pannic-
ulus inflammation than chromic gut and Vicryl.

A scientific investigation that was recently com-

pleted evaluated 8 suture materials (PDS, PDS/Tri-
closan, Monocryl, Monocryl/Triclosan, Vicryl 910,
chromic gut, monofilament nylon, and surgical
steel) and cyanoacrylate tissue adhesive in hatchling
ball pythons (Python regius) over a period of 90
days.

45

Samples were evaluated histologically at 3, 7,

14, 30, 60, and 90 days after implantation. All suture
types caused significantly more inflammation over

178

McFadden

all time points compared with unsutured incisions
(negative control). Cyanoacrylate tissue adhesive did
not cause significantly more inflammation than the
negative controls at any time point, suggesting that
small superficial skin incisions or lacerations may be
best closed with cyanoacrylate tissue adhesive. All su-
ture materials caused chronic inflammatory responses
that were significantly higher than the negative control
90 days after suture implantation. Examples of inflam-
matory reactions are shown in

Figure 1

. No sutures

were completely absorbed by the end of the study
period, suggesting that absorption times are prolonged
compared with mammals. Despite previous reports
that reptiles may be unable to break down chromic
gut,

46,47

there was histologic evidence of fragmentation

of these sutures. Interestingly, there was also evidence
that before complete absorption, prolonged absorp-
tion may lead to suture extrusion.

Based on these studies, synthetic monofilament

suture material that is rapidly absorbed (e.g.,
Monocryl) should be used in reptiles. Unfortunately,
Biosyn and Caprosyn have not been evaluated in
reptiles, but, based on studies in mammals, may
compare favorably with Monocryl.

Fish

Of all exotic species commonly kept as pets, fish
represent the largest group, with over 75 million

being maintained in nearly 8% of US households.

40

Despite this popularity, veterinarians play a limited
role in their health care and few studies exist exam-
ining tissue reaction to suture materials in fish.

1,48-50

A single study evaluated the histopathologic reac-

tion to different suture materials in fish.

48

In that

study, 5 different suture materials (silk, monofila-
ment nylon, Maxon, Vicryl, and chromic gut) were
placed in the skin and body wall of koi (Cyprinus
carpio). Biopsies of the sutured tissues were taken 7
and 14 days after implantation and evaluated for
inflammation. Silk caused an inflammatory response
that increased between 7 and 14 days and was the
suture with the highest inflammation score at 14
days. The synthetic sutures induced a moderate in-
flammatory response at 7 days, with a decrease in
inflammation at 14 days. Vicryl caused a higher in-
flammation score than Maxon at 7 days, whereas
monofilament nylon produced a moderate, sus-
tained inflammatory response over the study period.
Chromic gut created a significant inflammatory re-
sponse at 7 days, and by 14 days no sutures were left
in the incision site.

Other studies evaluating suture material in fish

used gross inflammation and suture retention to
evaluate suture materials.

49,50

Healing response and

suture absorption using 4 suture materials (gut,
chromic gut, Vicryl, and PDS) were evaluated in

Figure 1.

Inflammatory reactions after implantation of different suture materials in ball pythons (Python regius). Samples were chosen as

representative examples of zero (A), mild (B), moderate (C), and severe (D) inflammatory responses. Suture material was lost in A and B during
processing, but surrounding inflammatory reaction is intact. Images are 20

⫻ magnification.

Sutures in Exotic Pet Surgery

179

largemouth bass (Micropterus salmoides) for 8 weeks
after surgery to obtain liver biopsies.

49

Gut sutures

were completely absorbed at 5 weeks and incisions
were healed at 6 weeks. Vicryl sutures were com-
pletely absorbed by 7 weeks and incisions were
healed by 8 weeks. All PDS sutures were intact at the
end of the evaluation period, and all incisions in this
group were healed at 3 weeks.

A more recent study evaluated 6 suture materials

(monofilament nylon, Monocryl, braided nylon, Vi-
cryl, Vicryl

⫹, and silk) in Chinook salmon (On-

corhynchus tshawytscha).

50

Suture retention was de-

fined as a functional suture that was present in the
fish, remained knotted, and did not tear through the
body wall. Monocryl exhibited a greater suture re-
tention than all other suture types, and braided ny-
lon had significantly lower retention than all other
suture types at 7 days after implantation. Monofila-
ment sutures had better retention than all braided
sutures at 14 days. Inflammation scores were lower for
monofilament nylon, braided nylon, and Monocryl
than all other suture types at 7 and 14 days after im-
plantation.

Based on the results of these studies, synthetic

monofilament absorbable sutures appear to be the
most appropriate suture material in fish. Unfortu-
nately, no direct comparisons were made between the
3 monofilament sutures that were determined to be
best suited in each study (Maxon, PDS, and Monocryl).

Conclusion

This article emphasizes the need to have an in-depth
understanding of available suture materials and
knowledge of the tissues to be closed and their heal-
ing times. This knowledge will help the veterinary
surgeon select the best material for each patient and
procedure. Articles describing or comparing suture
tissue reactions can aid in selection, but these studies
are varied in the methods used to evaluate the reac-
tion, time periods that reactions are evaluated, and
types and numbers of sutures evaluated, with no
single standard for grading such evaluations.

21

To

cause more confusion, similar studies may have var-
ied or contradictory results. Some believe that these
studies fail to evaluate acute reactions over the first 7
to 14 days when trauma and inflammation associated
with the surgical procedure nullify the possible dif-
ferences in reaction to the suture materials.

51

Fur-

ther studies evaluating loss in tensile strength and
time to complete absorption of sutures in exotic
animal species (especially in those animals classified
as nonmammalian), as well as studies evaluating
healing times of different tissues in nondomestic

species, can help veterinarians determine the opti-
mal suture to use for different surgical procedures.

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