Page 20 - Manual of Equine Field Surgery

-

16 PRESURGICAL PREPARATION AND ASSESSMENT

ment sutures. Stainless steel has the worst han- with an increased incidence of suture sinus tract

dling properties. formation.'

The number of throws necessary to secure a

square knot varies with the size and type of suture

material. In general, multifilament sutures have SUTURE PLACEMENT AND PATTERNS

better knot security than do monofilament

sutures. Stainless steel has the best knot security. The placement of sutures affects wound healing.

Also, the smaller the suture, the more secure is Sutures should be placed such that they just

the knot. For example, No. 2-0 polyglycolic acid appose the wound edges. Loosely approximated

suture material has better knot security than does wounds are stronger at 7, 10, and 21 days after

No. 2 polyglycolic acid suture material. surgery than are wounds tightly secured with

The suture material should be as strong as the sutures,8 possibly because overtightening disrupts

tissue in which it is placed. Skin and fascia are rel- the microvascular circulation to the wound edges.

atively strong, whereas fat and muscle are rela- Wound edges weaken over time because of colla-

tively weak. In traumatic wounds, the tissue gen lysis; therefore, sutures should be placed at

immediately surrounding the wound may be least 0.5 cm from the margins. Additionally, al-

compromised. Therefore, the wound margins though more sutures improve initial strength,

should be debrided, if possible, to clean healthy the increased number of sutures compromises

tissue and the sutures should be placed back from blood supply to the wound edges and stimulates

the wound margins to ensure that the sutures are an excessive tissue reaction and subsequently

placed in the healthiest tissue. The strength of a increases infection rate. Deep sutures should be

sutured wound is usually dependent on both the placed only in fascial planes, tendons, and liga-

tissue's ability to hold suture and the tensile ments, because additional deep sutures are gener-

strength of the suture material. With healthy ally ineffective and cause excessive tissue reaction.

tissue, the initial strength of the sutured wound is The suture pattern also can affect wound

dependent 011 the strength of the suture; however, healing. Although the simple continuous pattern

by 3 to 4 days, the repaired tissue starts to increase is the easiest to apply and provides the most

uniform support, its design leads to reduced
in strength.

All suture materials potentiate infection by microcirculation to the wound margins and a

acting as foreign bodies when placed in contami- single break results in failure of the entire line.

nated wounds. Monofilament sutures are the least Comparatively, a simple interrupted pattern leads

reactive and can withstand wound contamination to less edema, does not exert a negative impact 011

better than can multi:filament sutures of the same the microcirculation, and encourages greater

material. Multifilament sutures exhibit capillarity, wound tensile strength after 5 and 10 days,7

a wicklike action that allows bacteria to move although these positive effects are attenuated at

along the suture strand. Natural materials ( e.g., later times.9·13 The disadvantages of interrupted

catgut, silk, cotton, linen, collagen) are generally patterns compared with continuous patterns

considered the most reactive, are weaker, and have include the use of more suture material and
increased placement time. Interrupted suture pat-
a variable rate of absorption.

Synthetic absorbable sutures, such as polygly- terns should be used when impaired healing is

colic acid, polyglactin 910, polydioxanone, poly- anticipated and excessive tension is present.

glyconate, and polyglecaprone, have the distinct Simple interrupted suture patterns cause less

advantage of being absorbed at a constant rate by inflammation than vertical mattress and far-near-

hydrolysis. Additionally, monofilament sutures near-far patterns because of relatively less suture

are less reactive than twisted or braided materials. material in the incision line and fewer skin

Synthetic nonabsorbable sutures, such as nylon, penetrations.

polypropylene, and poly:filament polyamide, are Suture patterns may be divided based on

generally less reactive than absorbable sutures. whether they are appositional or serve as tension

Polyfilament polyamide has characteristics that suture patterns. Simple interrupted, simple con-

make it the least desirable synthetic nonab- tinuous, Ford interlocking, cruciate, and subcuta-

sorbable suture, such as losing 150/o to 20°/o of neous or subcuticular patterns are classified as

its strength when wet and being associated appositional suture patterns (Figures 3-1 to 3-5).