Sutures and general surgical implants

| 10 |

Chapter

10 

Sutures and general surgical implants S.J. Langley-Hobbs

Knowledge of the properties of the suture materials and implants available is essential to be able to make an informed decision about what to use during surgery. Use of the wrong suture material, use of an inappropriate suture pattern or placement of a loose ligature could cause dehiscence of a surgical incision or hemorrhage in the cat, requiring additional corrective surgery. In some situations where there is inadequate tissue for closure, for example after tumor resection, synthetic materials can be used to fill the defect. Surgical implants have been developed for specific purposes, for example ameroid constrictors for portosystemic shunt closure. In contrast, some readily available inexpensive materials (e.g., cellophane) have also been used with success. The general properties of suture materials and implants will be covered in this chapter, with specifics of their usage covered in the organ-related chapters.

SUTURE MATERIALS Suture materials are used to approximate tissues and hold them in apposition while healing occurs. They may be placed to loosely approximate tissue during healing in an area with a good blood supply or low tension or as a tight ligature to seal a blood vessel while a clot is forming. In avascular areas or where there is high tension stress across a wound, the suture needs to retain its strength for a period of time compatible with the healing period of the tissue. In wounds where there is contamination or the risk of infection it may be preferable for the suture to be completely absorbed once its function is complete. Suture materials are generally categorized as absorbable or nonabsorbable, monofilament or multifilament and natural or synthetic. A suture is classified as non-absorbable if its mechanical resistance is constant for 60 days following implantation, even it is eventually absorbed. Although the perfect suture does not exist, ideally a suture should have minimal tissue reactivity, high initial tensile strength, predictable absorption, tie reliably, and be applicable to a wide variety of uses. © 2014 Elsevier Ltd DOI: 10.1016/B978-0-7020-4336-9.00010-X

Selection of suture materials Suture material of inadequate strength may result in wound breakdown, while suture material with high memory can lead to knots coming undone unless the surgeon is aware of this and adds additional throws to the knot to counteract this property. Excessively large diameter suture material results in a weaker knot, leading to knot insecurity and also more foreign material at the surgical site. The smallest diameter suture material that will adequately hold the healing tissue should be used. In cats, size 1.5–3 metric gauge (M) will be suitable for most general use. For either very delicate work or areas where a higher tensile strength is required, sutures outside this size range may be needed. Size conversion for suture materials is shown in Table 10-1. Multifilament suture material is usually stronger than monofilament and has better knot security due to the higher friction co-efficient. Conversely, multifilament material, particularly if dry, can cause drag which can damage delicate tissue and inadvertently cause the surgeon to tug on the material, which can cause iatrogenic injury and suture pullout. Multifilament suture material also has a greater surface area for bacterial penetration and contains crevices which can harbor bacteria. These characteristics are reduced when the multifilament or braided suture is coated. Natural materials like silk, cotton, ovine intestinal submucosa, or bovine serosa (catgut) can cause inflammatory reactions within the tissues and their absorption, by phagocytosis, may be variable depending on implant site and patient status. Synthetic materials are usually chemical polymers absorbed by hydrolysis, and thus they often have a more predictable rate of absorption independent of these factors (Table 10-2). Modifications to several of the generic suture materials include the introduction of rapidly absorbable sutures (the ‘Rapide’ range) and sutures with improved resistance to bacterial penetration (the ‘Plus’ range). The ‘Plus’ range sutures, which include polyglactin 910, polydioxanone and poliglecaprone, are coated with triclosan, which is an inhibitor of bacterial fatty acid synthesis with demonstrable antibacterial activity. The use of triclosan-coated sutures in humans has been associated with a decreased infection rate.1

105

Section | 2 |

Diagnostics, Equipment and Implants

Table 10-1  Size conversions for suture materials Actual size (mm)

Metric gauge (M)

United States Pharmacopeia (USP)

0.02

0.2

10–0

Surgical gut (USP)

0.03

0.3

9–0

0.04

0.4

8–0

0.05

0.5

7–0

8–0

0.07

0.7

6–0

7–0

0.1

1

5–0

6–0

0.15

1.5

4–0

5–0

0.2

2

3–0

4–0

0.3

3

2–0

3–0

0.35

3.5

0

2–0

0.4

4

1

0

0.5

5

2

1

A

B

C Table 10-2  Loss of strength and absorption times of suture materials Suture material composition

Loss of strength in weeks (percentage loss)

Absorption time in days

Intestinal submucosa (catgut)

2–3 (100%)

14–80 approx

Polyglytone

2–3 (100%)

56

Poliglecaprone

1–2 (50%)

119

Polyglactin 910

2–3 (50%)

56–70

Polyglycolic acid

2–3 (50%)

90

Glycomer 631

2–3 (50%)

90–110

Lactomer

2 (20%)

56–70

Polydioxanone

4–6 (50%)

180

Suture placement and patterns Careful attention to proper suturing technique and use of the appropriate suture patterns for wound closure is important in ensuring optimal closure and incisional healing. Careless handling of the suture or the use of damaged instruments can weaken the suture and make it more prone to breakage. Eversion of skin edges or excessively tight skin sutures can encourage self-trauma by the patient, increasing the risk of suture line infection or premature suture removal by the cat. Excess tension on sutures in wound closure can lead to ‘cutting out’ of sutures or to ischemia of tissue adjacent to the sutures. In areas of tension, the surgeon should consider other techniques such as the use of subcutaneous walking sutures, undermining of the skin, tension-relieving sutures, and then surgical procedures, including relaxing incisions, plasty procedures, or skin flaps (see Chapter 19). Placing an adequate number of throws is important to minimize the risk of the sutures undoing. Although some manufacturers give guidelines, strict recommendations are not made for individual suture materials, as this is dependent on many factors such as tightness of

106

D Figure 10-1  Simple sutures: (A) simple interrupted; (B) cruciate mattress; (C) vertical mattress; and (D) horizontal mattress.

each throw, length of the cut end(s) or ears and the tissue tension. The knot security of individual suture materials is influenced by the memory, plasticity and pliability of the suture material. Braided material generally has good knot security but this is also influenced by suture coating: some braided material is coated to decrease tissue drag and bacterial penetration but this will tend to decrease knot security. General recommendations for simple interrupted suture placement would be to place four throws, ensuring that the throws are tightened after the third (or second if suturing skin) and subsequent throw. For simple continuous patterns the recommendation is for five to six throws at the start of the suture line with one or two additional throws at the end of the suture pattern, as the suture material becomes damaged during use and the end knots are generally less secure. Suture patterns commonly used in feline general surgery are shown in Figures 10-1 and 10-2. There are several different suture materials on the market (Table 10-3) with a variety of different properties, indications and contraindications. The materials available in practice will vary according to surgeon preference and procedures commonly performed. The indications and contraindications for the different suture materials are listed in Tables 10-4 and 10-5.

Sutures and general surgical implants

Chapter

| 10 |

Table 10-3  Suture materials and some commercial manufacturers Suture material

Manufacturer

Catgut

A

B

D

C Figure 10-2  Continuous suture patterns: (A) Cushing; (B) Connell; (C) Ford Interlocking; and (D) Lembert.

Polyglactin 910

Vicryl: Ethicon, Polysorb: USS/DG

Poliglecaprone

Monocryl: Ethicon

Polyglycolic acid

Dexon II: USS/DG, Safil: Braun

Polyglycomers

Maxon: USS/DG, Monosyn: Braun

Polydioxanone

PDS: Ethicon

Glycomer 631

Biosyn: USS/DG

Polyglytone 6211

Caprosyn: USS/DG

Nylon, polyamide

Monosof: Covidien, Ethilon, Nurolon: Ethicon, Dafilon: Braun, Supramid: Braun, Dermalon: USS/DG, Monosof: USS: DG, Surgilon: USS/DG

Caprolactum

Vetafil

Polypropylene

Prolene: Ethicon, SurgiproII: USS/DG, Premilene: Braun

Polyester

Surgidac: USS/DG, Ti.Cron: USS/DG, Mersilene: Ethicon, Ethibond Excel: Ethicon, Miralene: Braun, Dagrofil: Braun, Synthofil: Braun, PremiCron: Braun

Polybutester

Novafil: USS/DG, Vascufil: USS/DG

Silk

Perma-hand: Ethicon, Sofsilk: USS/DG, Silkam: Braun

Stainless steel

Steel: USS/DG, Flexon: USS/DG, Surgical Stainless Steel Suture: Ethicon, Steelex: Braun

significant foreign body reaction when implanted in tissues. Absorption is unpredictable, occurring faster in patients with cancer, anemia, and malnutrition or when used in gastric surgery, an infected wound, or highly vascularized tissue.2 It is also absorbed faster when used in the mouth and in other mucous membranes, e.g., vagina, due to the presence of microorganisms. In one study of 12 cats where suture material was implanted into the oral cavity it completely disappeared between days 3 and 7.3 Chromic catgut suture is a variant treated with chromic acid salts. This treatment produces roughly twice the suture-holding time of plain catgut, but greater tissue inflammation occurs. Full tensile strength is extended to 18–21 days. Fast catgut suture is heat-treated to give even more rapid absorption in the body. Catgut is banned in Europe and Japan because of concern over bovine spongiform encephalopathy (BSE), although the herds from which gut is harvested are certified BSE-free. Catgut has largely been replaced by synthetic absorbable polymers such as polyglactin, polyglytone and poliglecaprone.

Poliglecaprone 25 ABSORBABLE SUTURE MATERIALS Catgut Catgut is made of collagen obtained from bovine intestines. It is naturally degraded by the body’s own proteolytic enzymes. It can cause a

Poliglecaprone 25 is a monofilament absorbable suture material made of glycolide and epsilon caprolactone copolymer (PGCL). It is pliable, with low tissue drag giving it smooth tissue passage. Knot security is not reliable, hence the ears should not be cut too short and additional throws placed if used for a continuous pattern. It loses its strength relatively quickly, with the tensile strength capability reduced to about

107

Section | 2 |

Diagnostics, Equipment and Implants

Table 10-4  Some indications and contraindications for use of suture materials in cats Indications

Contraindications

Absorbable suture material Polyglytone

Soft tissue approximation, subcutaneous, subdermal, intestinal surgery

Areas where there is high tension combined with prolonged healing

Poliglecaprone

Soft tissue approximation, subcutaneous, subdermal, intestinal surgery

Areas where there is high tension combined with prolonged healing

Polyglactin 910

Soft tissue approximation and ligation

Should not be used where extended approximation of tissue is required

Polyglycolic acid

Subcutaneous and dermal sutures, abdominal and thoracic surgery

Elderly anemic and malnourished patients, urinary tract

Glycomer 631

For abdominal closure and soft tissue repair requiring a strong but absorbable material

Should not be used where extended approximation of tissue is required

Polyglyconates

Internal tissues where a long-lasting absorbable suture is preferable (linea alba, hernias). Used for intestinal surgery

Should not be used where extended approximation of tissue is required or for fixation of permanent cardiovascular prostheses or synthetic grafts

Polydioxanone

Internal tissues where a long-lasting absorbable suture is preferable (linea alba, hernias). Used for intestinal surgery

Areas of rapid healing where prolonged suture retention not required

Non-absorbable suture material Polyamide

Skin closure

Polypropylene

Skin closure and general soft tissue approximation and ligation, tendon and ligament repair

Internally in infected or contaminated areas where non-absorbable material would be ill-advised Not necessary in rapidly healing tissue as non-absorbable

Tissue types

Suture recommendation and contraindications

Skin

Monofilament non-absorbable, e.g., polyamide or polypropylene

Subcutaneous

Absorbable, e.g., poliglecaprone, polyglactin 910, polyglytone

Tendon

Strong non-absorbable or slowly absorbable, e.g., polydioxanone, polypropylene, polyamide

60% within a week, 20–30% at two weeks and all strength is lost within three weeks. It undergoes reliable absorbtion by hydrolysis. It was used in a prospective study for all ligatures and closure of the linea alba in routine ovariohysterectomies in 24 cats.4 Dehiscence did not occur in any of the cats; however, the author has seen dehiscence of the linea alba after celiotomy closure and would recommend alternative suture material such as polydioxanone or glycomer 631 be used in this situation. Poliglecaprone is commonly used for subcutaneous and subdermal tissue closure. Careful technique ensuring an adequate number of throws, good knot security and sufficient purchase of tissue with each bite should be taken when placing in areas of high tension. It causes a relatively short-lived inflammatory response.

Abdominal closure – linea alba

Strong, with good knot security (use extra throws), e.g., polydioxanone, glycomer 631

Polyglactin 910

Muscle

Absorbable, e.g., polyglactin 910, polyglycolic acid, glycomer 631

Parenchymal organs

Absorbable monofilament, e.g., poliglecaprone, glycomer 631

Hollow viscus

Absorbable, e.g., poliglecaprone, polyglactin 910, glycomer 631 Avoid polyglycolic acid in the bladder as it rapidly dissolves in urine

Infected or contaminated wounds

Absorbable g. polyglactin, poliglecaprone. Avoid braided non-absorbable sutures which can fistulate or catgut which rapidly absorbs

Vessels and vascular anastomoses

Ligatures – absorbable suture material Vascular anastomoses – non-absorbable monofilament, e.g., polypropylene and with a needle-to-suture ratio of 1 : 1

Table 10-5  Suture recommendation for various tissue types

108

Polylactin 910 is an absorbable, braided suture material made of polyglycolic acid. The suture holds its tensile strength for three to four weeks in tissue, retaining 75% of strength after two weeks, 50% after three weeks and 25% after four weeks and it is completely absorbed by hydrolysis within 70 days. The suture material, being braided, has some tissue drag, particularly if it dries out, but it has good knot security and is good for ligation. The sutures are coated with a copolymer of calcium stearate to allow less drag and better water repellency. The suture material can also be treated to enable more rapid breakdown for its use in rapidly healing tissues such as mucous membranes.

Polyglycolic acid Polyglycolic acid (PGA) suture is classified as a synthetic, absorbable, braided multifilament. It is coated with N-laurin and L-lysine, which render the thread extremely smooth, soft, and safe for knotting. It is also coated with magnesium stearate and finally sterilized with

Sutures and general surgical implants ethylene oxide gas. It is naturally degraded in the body by hydrolysis and has approximately 60% strength left at 14 days; absorption is completed between 60 and 90 days. It has the advantages of high initial tensile strength, smooth passage through tissue, easy handling, excellent knotting ability, and secure knot tying (better when wet). It is commonly used for subcutaneous sutures, intradermal closure, abdominal and thoracic surgeries. Elderly, anemic and malnourished patients may absorb the suture more quickly. Absorption is faster in urine, and so it is not recommended for urinary tract surgery.5

Polydioxanone Polydioxanone (PDS) or poly-p-dioxanone is a slowly absorbable monofilament suture composed of the polyester, poly (p-dioxanone). This is a monofilament with greater strength than monofilament nylon and polypropylene, and with less tissue drag than the multifilament materials. It has good strength retention, with only 20% loss over two weeks and 60% loss after eight weeks. It can sometimes be difficult to handle due to its memory and tendency to coil or ‘pig-tail’. Knot security can be relatively poor, and seven throws are advisable at the end of a continuous suture line. Complete absorption occurs by hydrolysis and takes around 200 days. Polydioxanone was still intact at day 28 in the oral cavity of cats, and it is recommended for procedures in which longer healing time is anticipated3 such as hernia repair or pexy procedures. Despite the less than ideal knot security, the strength and pre­ dictable rate of absorption make this an ideal suture material for closure of the linea alba and it has become a very popular material for this use.

Polyglyconates These suture materials are polymers of glyconates (Monosyn: Braun) or combinations such as glycolic acid and trimethylene carbonate (Maxon: USS/DG). The tensile strength and absorption is dependent on the composition. Maxon can be used for linea alba closure; Monosyn has quicker absorption and loses 50% of its tensile strength by two weeks so would be more suitable for subcuticular closure.

Glycomer 631 This monofilament is a copolymer of glycolide, dioxanone, and trimethylene carbonate. It is advertised as the strongest monofilament suture material available, second only to steel. A quarter of the strength is gone by day 14, and only 40% remains at three weeks. Full absorption takes 90 to 110 days. It has fair handling characteristics with low tissue drag and slightly better knot security than polydioxanone, which is a comparable though longer-lasting monofilament. It has slightly less memory compared to polydioxanone. This material is promoted as suitable for abdominal closure and soft tissue repair requiring a strong but absorbable material.

Polyglytone 6211 A synthetic, absorbable polyester material indicated for very shortterm wound support. Approximately half of its initial tensile strength is gone at day 5, and only 25% remains at day 10. This suture material is completely absorbed by day 56. Interestingly, the absorption rate for this material is the closest of any synthetic material to catgut, and the handling of the suture material is similar. This suture is suitable for ligature placement, subcutaneous closure, intradermal sutures and use in the oral cavity.

Chapter

| 10 |

NON-ABSORBABLE SUTURE MATERIALS Stainless steel An alloy made from natural materials, stainless steel is available as a monofilament or braided multifilament suture material. Steel has the highest strength of any other suture material.5 It is biologically inert and can easily be sterilized by autoclaving. It incites little tissue reaction other than mechanical irritation from the ends. It has excellent knot security, although the knots can sometimes be difficult to place. Pieces of stainless steel can migrate if loose, and it will break if subject to repeated bending. It can easily cut or tear through sutured tissues if tightened too much. Given its difficult handling properties, it is not commonly used in practice as a suture material, but has a wide range of applications in clips and staples. One area, however, where steel suture is still commonly used is closure of sternotomy wounds, as in dogs it gives increased stability compared to PDS II or prolene.6

Silk Silk has a long history of use as a suture material. It is obtained as a fiber spun from the cocoon of the silk worm, and is available either twisted or as a braided multifilament. Silk has excellent handling characteristics, and is cheap. It has a variety of disadvantages, including tissue reaction, marginal knot security, and poor tensile strength. Many surgeons prefer the feel of silk, and it is still often used to ligate large vessels, although clinical use is limited. It can be moistened in sterile saline before use to improve knot security and reduce tissue drag, although this can slightly decrease its tensile strength. Silk is not recommended in hollow viscera or in infected wounds, as it can potentiate infection by trapping bacteria in its braiding. As with other multifilament materials, use in gall bladder and urinary tract surgery is discouraged, as it can be calculogenic.7

Polyamide Polyamide nylon is a generic designation for a family of synthetic polymers known generically as polyamides. Nylon can be found in both braided and monofilament forms. As a material, nylon is relatively inert, and has no capillary action as a monofilament. Only about 20% of monofilament nylon’s initial strength is gone at one year, although in some cases all the tensile strength in a multifilament strand can be gone at six months. Although monofilament nylon has a reputation for relatively poor handling and knot security,7 it is commonly used in a variety of applications including skin, cornea, fascia, and ligatures, e.g., pedicle ligatures for ovariohysterectomy. Due to its stiffness, it is not recommended within hollow viscera, as the cut ends cause mechanical irritation.2 A minimum of four throws on nylon is always recommended. In the same family of materials is polymerized caprolactam, a twisted and coated multifilament material with superior initial tensile strength compared to nylon. It has more tissue reactivity than nylon, however. It has been known to cause sinuses when implanted in tissues, so is best suited for skin. It is generally supplied in bulk rolls, but should not be considered sterile unless processed by ethylene oxide or heat sterilization. Autoclaving can make it more difficult to handle. In general, this family of materials is best suited for skin sutures. Although in general multifilament nylon materials may be easier to handle, the monofilament nylon materials would be preferred for use in the skin because they are less likely to wick outside contaminant bacteria into the deeper tissues of the wound bed.

109

Section | 2 |

Diagnostics, Equipment and Implants

Polypropylene Polypropylene is a widely used synthetic monofilament suture material that is composed of polymerized polypropylene. It is nonthrombogenic, and is often used in cardiovascular surgery in human patients. It is available as a mesh material for implantation. Polypropylene is very plastic, meaning that the material will assume a new shape when subject to tension, which contributes greatly to its good knot security if the sutures are tightened appropriately. Some surgeons find this material difficult to handle because of its memory and tendency to break if handled roughly. There is no appreciable loss of tensile strength after implantation. Polypropylene was still intact at day 28 post-implantation in the feline oral cavity3 and visual inspection showed polypropylene to have the least tissue reaction of all the suture materials tested. The clinical indications for use of polypropylene are varied and include cardiovascular and microvascular surgery, tracheobronchial surgery (e.g., tracheostomies and closure of bronchial stump after lobectomy), hernias and ruptures (e.g., perineal hernia repair), genitourinary (e.g., perineal urethrostomy), routine skin closure, and as a stay suture material.

Table 10-6  Needle characteristics Needle type

Description

Indications

Taper

Needle body is round and tapers smoothly to a sharp point that pierces and spreads tissue without cutting it

Generally used in easily penetrated tissues such as the intestine, subcutaneous tissue or loose fascia; or blood vessels

Cutting

Needle body is triangular and has a sharpened cutting edge on the inside (towards the wound)

Recommended in tough tissue such as skin, fascia, tendons and ligaments

Reverse cutting

Needle body is triangular and has a sharpened cutting edge on the outside (away from wound)

Taper cut

Has a combination of a reverse cutting point and taper point body

Generally used for suturing tough dense tissue such as a tendon or for vascular grafts

Blunt point

Has a rounded blunt point that can dissect through friable tissue without cutting

For suturing soft parenchyma such as liver or kidney

Side cutting or spatula points

Flat on top and bottom with a cutting edge along the front to one side

For eye surgery

Polyester A synthetic non-absorbable multifilament or monofilament suture material that is usually coated; the suture material has been reported to have some tissue reactivity if the coating is lost. This material has a very high and prolonged tensile strength, although knot security is only fair. Infection in an area where braided polyester suture has been used almost always necessitates removal. Polyester is very strong and has been used most commonly for prosthetic implant placement and large vessel ligation. Given that suture contamination and sinus tract formation with polyester materials can be problematic, other suture materials will provide sufficient strength without this risk.

Polybutester A special type of polyester material composed of polyglycol terephthalate and polybutylene terephthalate. This makes the material retain many advantages of both polypropylene and polyester. It is delivered as a monofilament, and is commonly used in cardiovascular and ophthalmic procedures. The material is known to have better knot security than polyester alone, with good tensile strength and flexibility.

spaces than the straight or half-curved needle, and the arc can be chosen to maximize tissue bite depth and width. 3/8 and 1/2 needles are most commonly used in veterinary medicine, but the 5/8 is slightly easier to manipulate in deep or inaccessible locations. A needle pierces the tissues by use of a cutting edge or a sharp point (taper) (Table 10-6 and Fig. 10-3) though a blunt-ended round body needle is available for use in friable viscera such as the liver or spleen. Which type of needle to use depends on many factors including the composition of the tissue that it is to be passed through, the thickness of tissue, and its depth in the body. As a general needle the taper point round bodied needle is suitable for most tissues, with the reverse cutting used for tougher tissues such as skin and fascia.

NEEDLES Modern sutures feature swaged atraumatic needles where the suture material is provided attached to the eyeless needle. Time does not have to be spent threading the suture on the needle and, more importantly, the suture end of a swaged needle is smaller than the needle body so it passes easily through the tissue. It is essential to use swaged needles for atraumatic surgery in cats, particularly when suturing delicate tissues such as viscera. There are essentially three types of needle shapes.8 Straight needles are used in accessible superficial places where the needle can be manipulated directly with fingers, e.g., skin, purse-string suture in the anus. Half-curved needles are straight in their shaft, but have a curved, cutting tip to them. These are not commonly used but are suitable for skin or ophthalmic surgery. Curved needles are manipulated with needle holders. They are formed in an arc of 1/4, 3/8, 1/2, or 5/8 circles. This allows the surgeon access with the needle to smaller

110

SUTURE REACTIONS IN CATS Cats appear to be prone to incisional swelling following celiotomy closure9 independent of the type of suture material used. The associated inflammation and fibrous tissue proliferation usually resolves without treatment over a number of weeks, although complications such as failure of the skin sutures, failure of the skin and subcutaneous sutures, wound dehiscence, and seroma or abscess formation may be associated with severe incisional swelling.9 Swelling and inflammation along the incision line was observed after elective ovariohysterectomy in 22 of 66 cats in a retrospective study. In a prospective study of 99 feline abdominal incisions closed with surgical gut, polyglactin 910, or polydioxanone, with and without subcutaneous closure, the least inflammation occurred when the linea alba was sutured with polyglactin 910 and the subcutaneous tissues were not sutured. The

Sutures and general surgical implants

Tapercut

Cutting

Reverse cutting

Tapercut

Blunt point

Chapter

| 10 |

come into contact with moisture in the skin. The products may contain dye to allow the user to easily see where the product has been applied. They are provided in single use capsules or bottles or multiple use vials, but the latter have a tendency to block unless used frequently. Cyanoacrylates form a bond across apposed wound edges allowing normal healing to occur below. They should be applied correctly to avoid complications; skin edges need to be accurately apposed and the glue applied over the top to form a bridge. It should not be allowed to enter the incision, where it may cause a foreign body reaction and local inflammation.11 A spray formulation is also available that forms a thin topical bandage. The adhesive polymerizes on contact with exudates from the wound, forming an occlusive dressing.

Indications Their use saves time during wound repair, provides a flexible, water resistant protective coating, is less traumatic and eliminates the need for suture removal.12 They can be used on large wounds concurrently with subcutaneous or subcuticular sutures. They are marketed to replace sutures of size 1 M or smaller or for use on superficial wounds in areas with no tension. They have been used for traumatic lacerations, abrasions, suture/staple line sealing, skin closure after spaying/ neutering and dewclaw removal. N-butyl-cyanoacrylate tissue adhesive was evaluated as a skin closure material in a population control program.13 The time required for closure of the surgical site with the adhesive was shorter than with nylon, saving approximately one minute per animal. As the adhesive eliminates the need for suture removal and decreases surgery time without additional risk to the cat, it may be indicated for surgical population control programs.13 Cyanoacrylate has also been used successfully for embolization of an arteriovenous fistula in a cat.14

Contraindications Spatula Figure 10-3  Needle point types.

inflammatory reaction did not appear to be specifically related to any particular suture material as reactions were seen with all of them.9 Histologically, reactions in the linea alba of 12 other cats progressed from purulent to fibromononuclear to fibrous within 14 days after closure with gut, polyglactin 910, and polydioxanone. Microscopic evidence of seroma formation was found in nine of 12 animals in which the subcutaneous tissue was not sutured, suggesting that surgical closure of subcutaneous dead space was indicated. Another study found conflicting results, with subcutaneous closure of celiotomy incisions causing increased tissue swelling compared to wounds closed without subcutaneous sutures.10 The results of this study suggested that placement of subcutaneous sutures in cats may not be the preferred technique in relation to postoperative inflammation. The authors would recommend a subcutaneous layer as it provides additional incisional security and provides an extra barrier to dehiscence, particularly if the cat removes the skin sutures.

TISSUE GLUE Topical adhesives are made from medical grade cyanoacrylates, a group of rapidly polymerizing adhesives, which polymerize when they

They should not be used for closure of mucous membranes or in areas of tension as they do not provide as strong a closure as a properly sutured incision. Cyanoacrylate was compared with the use of sutures in a study on enteroplication in cats.13 The inflammation associated with the adhesive persisted for the four weeks of the experiment, and it was concluded that cyanoacrylate tissue adhesive cannot be recommended for this clinical procedure.13

IMPLANTS FOR PORTOSYSTEMIC SHUNT CLOSURE Ameroid constrictor An ameroid constrictor is a device for gradual occlusion of blood flow. It is composed of a ring of casein, inside a ring of stainless steel (Fig. 10-4). Casein is a hygroscopic substance that swells as it slowly absorbs body fluid. The stainless steel sheath forces the casein to swell inwardly, eventually closing the ring and obliterating the shunt. In cats, ameroid constrictors are most commonly used for gradual constriction of portosystemic shunts, though a higher incidence of multiple acquired shunts has been associated with their use (see Chapter 32). They are gas sterilized and therefore should not be used until 12 to 24 hours after sterilization to allow residual ethylene oxide to be released from the casein. Before constrictor placement, the ‘key’, a small column of casein that completes the constrictor ring, is removed from the ameroid constrictor and set aside in a dry cup. The choice of ameroid constrictor size for portosystemic shunt occlusion is based on shunt diameter;

111

Section | 2 |

Diagnostics, Equipment and Implants

A

Figure 10-4  An ameroid constrictor.

therefore the surgeon should have a selection of sizes available at each surgery. Ameroid constrictors come in various sizes, with internal diameters ranging from 3.5–9 mm; constrictors with 3.5, 5 and 6.5 mm internal diameters are most frequently used for PSS ligation in cats.15 To avoid postoperative portal hypertension, a constrictor is selected that does not compress the shunt immediately. After placement around the vessel to be closed, the key is replaced to complete the circle of casein. Ameroid constrictors were thought to gradually close over four to five weeks, but generally thrombus formation in the enclosed vessel will occur earlier, often by ten days to two weeks.16 Time to occlusion of the vessel is dependent on the size of the vessel and constrictor and the rigidity of the outer ring. Closure is most rapid during the first three to 14 days after implantation; the rate of closure declines thereafter. For further information on the use of ameroid constrictors see Chapter 32.

Cellophane Gas sterilized strips of cellophane have been used to provide partial occlusion of shunts17 (see Chapter 32). Cellophane can be obtained from a florist, and is sterilized in ethylene oxide or hydrogen peroxide gas plasma. Strips are cut to size (triple folded 10 mm long by 4 mm wide). After placement around the shunt the strips are secured together with surgical clips or staples. Inflammation caused by the cellophane results in complete occlusion of most shunts in four to six weeks.

SHEETS AND MESHES

B Figure 10-5  Porcine small intestinal submucosa used for reconstruction of a diaphragmatic defect in a kitten. (From Andreoni AA, Voss K. Reconstruction of a large diaphragmatic defect in a kitten using small intestinal submucosa (SIS). J Fel Med Surg 2009;11:1019–1022, with permission from Elsevier.)

sizes, including large sheets, tubes, cylinders, and cones. This makes it suitable for many surgical applications. SIS comes in multiple sizes (2 cm × 3 cm to 7 cm × 20 cm) and is activated by immersion in sterile water for five to ten minutes. Surgisis Gold is a thicker eight-ply mesh with reinforced suture zones to prevent the suture cutting through the mesh. This thicker mesh has good handling properties and avoids the need for two layers of Surgisis four-ply.18 SIS has been used successfully in the reconstruction of a large diaphragmatic defect in a kitten (Fig. 10-5)19 and in feline corneal disease.20 An advantage of SIS grafts is that are they are absorbed over time, so they should not restrict growth in immature animals.

Porcine small intestinal submucosa

Surgical meshes

Small intestinal submucosa (SIS) is a naturally derived biomaterial isolated from the small intestine of pigs. After removal of the mucosal, serosal, and muscular layers of the intestine, a strong, collagenous matrix remains. Following treatment for disinfection, cell removal, and sterilization, SIS is biologically safe, easy to handle, has sufficient tensile strength, is infection resistant, and allows remodeling of replaced tissue. In addition, SIS can be formed into many shapes and

Meshes commonly used for surgical reconstruction include polyglactin, polypropylene and polytetrafluoroethylene (PTFE). Polyglactin is an absorbable mesh and is preferred in contaminated wounds. Polypropylene meshes are non-absorbable and pervious to air and fluid. PTFE is strong, resistant to infection and impervious to air and fluids but it is very expensive. Polypropylene mesh is most commonly used for reconstruction in small animal surgery.

112

Sutures and general surgical implants

Chapter

| 10 |

Polypropylene mesh

Skin stapling

Polypropylene monofilaments are knitted into an elastic, durable, large pore mesh. This construction permits the mesh to be cut into a desired shape or size without unravelling. Meshes vary in pore size and elasticity. Polypropylene mesh facilitates the reconstruction of large tissue defects and is most commonly used for hernia repair or for reconstruction of the chest or abdominal wall (see Chapter 43).21 If neoplasms are removed with 1–3 cm margins and a deep margin of at least one fascial plane, then the resulting defect may benefit from closure with mesh.21 The main complication seen in cats is seroma formation; long-term complications are rarely reported.

Skin stapling devices have become an attractive and affordable alternative to traditional skin closure in small animals. Skin staplers for veterinary use are usually fixed head, disposable and available with varying numbers and sizes of stainless steel staples. Although labeled as for single-patient use, some practices will re-sterilize and reuse them.23 Staples should be removed with staple extractors. The ideal skin stapler is comfortable to handle, makes a palpable and audible click to signal staple formation is complete, has an open staple view to see how many staples remain in the cartridge, and provides effortless staple alignment. Staples should be consistently formed, secure, and they should not rotate in the skin. Depth of staple penetration should be easy to control and the staples should be easy to remove at the right time. Also, the ideal stapler would be readily re-sterilized for reuse. Thumb forceps are used to hold skin edges in apposition while the stapler is aligned with the incision, there usually being an arrow to indicate the correct position, then while applying some pressure the staple is fired. It is preferable to start at the proximal end of the incision and work distally so the formed staples are visible, to enable even spacing.

SURGICAL STAPLERS The use of surgical stapling devices in the cat is less widespread than in the dog, due in part to difficulty in placing large stapling units into the chest, but also because resection of organs and tissues using sutures is easier in cats due to their smaller size. Stapling devices are available for superficial wound closure and intra-abdominal and thoracic resections and anastomoses (Table 10-7). The advantage of surgical staplers is that their use can save time over more conventional or traditional surgical techniques such as suturing. For example, a thoracoabdominal (TA) stapler can be used for pulmonary lobectomy, as it is not necessary to independently isolate or ligate the hilar vessels.22 The staples are usually composed of stainless steel or titanium and they are therefore minimally reactive. Selecting the correct size of stapler and staples to create the correct length of staple line is critical. It is important that all the tissue to be ligated lies comfortably within the staple line. It is better to use a stapler that is too long and collect the extra staples on a sponge or swab than to use one that is too short that results in leakage from non-stapled tissue. Experience in the use of the equipment is essential, as is good surgical judgment as to when to use or not to use these techniques.22

Lung stapling Lung stapling devices are now routinely used due to the ease and speed of application, safety, and efficacy. Lung stapling devices have been used in cats to perform lobectomies for neoplasia and lung lacerations. In a clinical study in dogs and cats24 the stapling device was easy to apply accurately and the design generally allowed it to be placed without interference by the lesion. Dissection and ligation of vasculature was not necessary. In many circumstances, the surgeons in the study believed that these factors made the application of staples faster than traditional surgical techniques.22 The stapling equipment used most commonly in the cat is the TA30 or TA55/60 (Fig. 10-6). The TA designation stands for thoracoabdominal and the 30 or 55 designation is for length of the staple line in millimeters. The TA apparatus usually places two lines of B-shaped

Table 10-7  Surgical staplers for use in cats Type of surgical stapler

Abbreviation

Skin stapler

Indication or usage

Size for cats

Wound apposition

4.8 mm × 3.5 mm

Thoracoabdominal – Double staggered rows of staples Triple staggered row for TA 30-V3 Endoscopic version

TA

Partial pulmonary lobectomy Complete lobectomy

30–3.5 mm 55–3.5 mm or 4.8 mm 60–3.5 mm or 4.8 mm

End-to-end anastomosis – places a circular double row of staples that creates a two layer inverting anastomosis and a circular blade within the cartridge simultaneously cuts redundant tissue from each end

EEA

Transrectal colocolostomy

21 mm

Gastrointestinal – Endoscopic version

GIA Linear Proximate Cutter

Few indications due to small size of feline intestine

3.5 mm

Ligating dividing stapler

LDS

Splenectomy Mesenteric vessels Ovariohysterectomy

One size, secures vessels up to 7 mm

Splenectomy, limb amputation, vessel sealing

Small Medium

Ligating clip appliers Ligaclip (Ethicon) Surgiclip (Covidien)

113

Section | 2 |

Diagnostics, Equipment and Implants

Figure 10-6  A thoracoabdominal stapler; the TA-30 is the size that is most suitable for use in the cat.

staples. The 30 mm staples are available in 3.5 mm heights and the 55 mm staples in 3.5 and 4.8 mm heights. These staples compress to 1.5 mm and 2 mm, respectively. A white vascular cartridge is available for the TA 30, the V3, which fires three lines of 2.5 mm staples, which compress to 1.5 mm. Selection of the height of the 55 mm staples is dependent on the compressed thickness of the tissue. Normal tissues generally have 3.5 mm staples applied, whereas 4.8 mm are generally used on thickened parenchyma. The vascular white cartridge for the TA30 (TA 30-V3) is advised for hilar lung and liver lobectomies. Before cutting the specimen from the staple line, large hemostats are used to clamp the tissue distal to the staples. This avoids spillage of neoplastic or infected cells into the pleural cavity. Any discharged staples that are free on either end of the suture line are removed. The staple line is then inspected. There is usually no indication to routinely oversew staple lines when performing a lobectomy. This may actually increase the chance of air leakage. If point areas of leakage or hemorrhage do occur, these can be independently occluded either with sutures or individual vascular clips. Thirty-seven dogs and cats were subjected to lobectomy, partial lobectomy, or pneumonectomy, using stapling equipment. The most common indication was neoplasia. No operative, perioperative, or long-term deaths could be attributed to the use of staples; complications were minimal. Staple resection was thus believed to be safe, fast, and efficient for removal of various segments of canine and feline lung.24

Abdominal stapling The use of stapling instruments (TA or GIA/ Proximate Linear Cutter stapler) to perform gastric surgery in small animal patients provides alternate techniques that are often more reliable and are usually performed more quickly than conventional techniques with manual sutures. In addition to reducing anesthetic and operating times, the risk of contamination of the abdominal cavity may be decreased significantly.25 The GIA (Covidien) or Proximate Linear Cutter (Ethicon) stapler deploys two staggered rows of staples and sections between them. They are available in a variety of lengths between 50 and 100 mm, with a choice of two different staple sizes. A functional end-to-end intestinal anastomosis can be performed using the GIA stapler (gastrointestinal stapler) placed into the two intestinal ends to be anastomosed and then closing the end of anastomosis with a TA stapler. This technique, though rapid and effective in dogs, is less applicable to most cats due to the size of the arms of the GIA stapler. The linear staplers designed for endoscopic surgery have smaller arms and are more suitable for use in this manner in the cat. Surgery of the colon and rectum has also been performed in cats using the end-to-end anastomosis (EEA) 21 circular stapler. In an

114

Figure 10-7  Testicular implants for use in cats. (Courtesy of Neuticles, with permission.)

experimental study in cats of caudal rectal resection from a dorsal approach, even this small size of EEA was difficult to insert into the feline anus and its use resulted in anal sphincter impairment postoperatively.26 The EEA has, however, been used successfully to perform transrectal colocolostomy in a series of cats that had undergone subtotal colectomy for acquired megacolon27 where the colon is dilated and therefore the size is not such a problem. Regular skin staples have not been successful when used to perform large intestinal anastomosis in cats. The LDS stapler places two titanium vascular clips and then cuts between them (ligate-divide stapler). It contains 30 staples and thus can be fired 15 times to secure vessels up to 7 mm in diameter. It decreases surgical time in procedures such as splenectomy and can be used to ligate jejunal vessels when performing intestinal resection and anastomosis. Hemostatic vascular clips, usually of titanium, are available in a variety of different sizes. When applying a clip, the vessel should be isolated and dissected clear of tissue. The diameter of the vessel needs to be between one-third and two-thirds of the length of the clip and the clip should be placed a couple of millimeters from the end of the vessel. Absorbable polymer locking clips are available that do not interfere with MRI signals.

IMPLANTS Silicone implants are not commonly used or indicated in feline surgery but they are available if owners request their implantation. There are silicone prostheses for implantation in cats after castration (Neuticles: CTI Neuticles). They are similar in size, shape and weight to the natural testicle. Implants available for use in cats are made of rigid polypropylene. There are two sizes (small and extra small) available for use in cats (Fig. 10-7). Silicone implants are available for implantation after enucleation in cats. The eyelids can be sutured closed over the prosthetic and its function is to prevent the sunken-in appearance. Alternatively, eyelids can be retained and the gray prosthesis is seen in the socket. An orbital prosthesis would not be recommended in cats with an infected eye socket, and cats with extremely flat faces and very shallow eye sockets such as Persians.

Sutures and general surgical implants

STENTS A stent is a tube that is used to maintain the patency of different conduits in the body, including the bile ducts, ureters, trachea, and bronchi. There are several different kinds of stents; those used in veterinary medicine are usually made of polyurethane or expandable metal or plastic mesh-like material.

Urinary stent There are stents specifically designed for placement in the feline ureter (DexStent-PU: Dextronix; Vet Stent-Ureter: Infiniti Medical)28,29 (Fig. 10-8). They have double-pigtail ends, multiple fenestrations and are

Chapter

| 10 |

made of polyurethane. The feline ureteral stent is 2.5 Fr tapered to a 0.018 inch wire and is available in three lengths (12, 14 and 16 cm). The multiple fenestrations allow drainage at several sites. The double pigtails are designed to sit in the bladder and renal pelvis. Urethral stents are self-expanding mesh tubes made of a nickeltitanium alloy (nitinol) (DexStent-UN: Dextronix).29 The stent mesh is designed for maximum flexibility and minimal shortening. Markers at the proximal and distal ends ensure excellent stent visibility for accurate placement. It can be supplied in two different working lengths: 80 cm or 120 cm. Urethral stents have been used successfully for malignant urethral obstruction and obstructive feline lower urinary tract disease in cats.30–33

Respiratory tract Stents used in the respiratory tract are self-expanding braided systems composed of a highly flexible nickel-titanium alloy (Nitinol) stent with radiopaque markers to assess positioning during fluoroscopy (e.g., DexStent-TN: Dextronix) (Fig. 10-9).29 Stents are designed to be flexibile yet keep their shape even when the neck is moved. Atraumatic stent endings reduce mucosal trauma/injury and potential inflammation. They have been used for relief of tracheal obstruction33 and collapsing trachea in the cat.

A

A

B Figure 10-8  A 2.5 Fr double-pigtail, multiple fenestrated, polyurethane stent for use in cats. (A) The whole stent showing the double pigtail ends. (B) Enlarged view of one of the fenestrated ends. ([A] courtesy of Infiniti Medical, LLC, Menlo Park, CA USA, with permission; [B] courtesy of Dextronix, with permission.)

B Figure 10-9  The DexStent-TN is a self-expanding braided tracheal stent system composed of a highly flexible Nickel-Titanium Alloy (Nitinol) stent mounted on a coaxial delivery system. (A) Stent in delivery system with tip just visible. (B) Stent shown after further protrusion from delivery system as it starts to expand. (Courtesy of Dextronix, with permission.)

115

Section | 2 |

Diagnostics, Equipment and Implants

REFERENCES 1. Galal I, El-Hindawy K. Impact of using triclosan-antibacterial sutures on incidence of surgical site infection. Am J Surg 2011;202:133–8. 2. Bellenger CR. Sutures part I. The purpose of sutures and available suture materials. Comp Contin Educ Pract Vet 1982a;4: 507–14. 3. DeNardo GA, Brown NO, Trenka-Benthin S, Marretta SM. Comparison of seven different suture materials in the feline oral cavity. J Am Anim Hosp Assoc 1996,32:164–72. 4. Runk A, Allen SW, Mahaffey EA. Tissue reactivity to poliglecaprone 25 in the feline linea alba. Vet Surg 1999;28: 466–71. 5. Schiller TD. In vitro loss of tensile strength and elasticity of five absorbable suture materials in sterile and infected canine urine. Vet Surg 1993;22:208–12. 6. Stashak TS, Yturraspe DJ. Considerations for selection of suture materials. Vet Surg 1978;7:48–52. 7. Pelsue DH, Monnet E, Gaynor JS, et al. Closure of median sternotomy in dogs: suture versus wire. J Am Anim Hosp Assoc 2002;38:569–76. 8. Bellenger CR. Sutures part II. The use of sutures and alternative methods for closure. Comp Contin Educ Pract Vet 1982b;4:587–600. 9. Freeman LJ, Pettit GD, Robinette JD, et al. Tissue reaction to suture material in the feline linea alba. A retrospective, prospective, and histologic study. Vet Surg 1987;16:440–5. 10. Muir P, Goldsmid SE, Simpson DJ, Bellenger CR. Incisional swelling following celiotomy in cats. Vet Rec 1993;132:189–90. 11. Schmiedt CW. Suture material, tissue staples, ligation devices and closure methods. In: Tobias KM, Johnston SA, editors. Veterinary surgery small animal. Missouri: Elsevier; 2012; p. 187–200.

116

12. Faria MC, de Almeida FM, Serrão ML, et al. Use of cyanoacrylate in skin closure for ovariohysterectomy in a population control programme. J Feline Med Surg 2005;7:71–5. 13. Nash JM, Bellenger CR. Enteroplication in cats, using suture of N-butyl cyanoacrylate adhesive. Res Vet Sci 1998;65:253–8. 14. Tobias KM, Cambridge A, Gavin P. Cyanoacrylate occlusion and resection of an arteriovenous fistula in a cat. J Am Vet Med Assoc 2001;219:785–8. 15. Kyles AE, Hardie EM, Mehl M, Gregory CR. Evaluation of ameroid ring constrictors for the management of single extrahepatic portosystemic shunts in cats: 23 cases (1996–2001). J Am Vet Med Assoc 2002;220:1341–7. 16. Besancon MF, Kyles AE, Griffey SM, Gregory CR. Evaluation of the characteristics of venous occlusion after placement of an ameroid constrictor in dogs. Vet Surg 2004;33:597–605. 17. Butler LM, Fossum TW, Boothe HW. Surgical management of extrahepatic portosystemic shunts in the dog and cat. Semin Vet Med Surg-Small Anim 1990;5:127–33. 18. Murphy F, Corbally MT. The novel use of small intestinal submucosal matrix for chest wall reconstruction following Ewings’s tumour resection. Pediat Surg Int 2007;23:353–6. 19. Andreoni AA, Voss K. Reconstruction of a large diaphragmatic defect in a kitten using small intestinal submucosa (SIS). J Fel Med Surg 2009;11:1019–22. 20. Featherstone HJ, Sansom J, Heinrich CL. The use of porcine small intestinal submucosa in ten cases of feline corneal disease. Vet Ophthalmol 2001;4: 147–53. 21. McAbee KP, Ludwig LL, Bergman PJ, Newman SJ. Feline Cutaneous Hemangiosarcoma: A Retrospective Study

22.

23.

24.

25.

26.

27.

28. 29. 30.

31.

32.

33.

of 18 Cases (1998–2003). J Am Anim Hosp Assoc 2005;41:110–16. Walshaw R. Stapling techniques in pulmonary surgery. Vet Clin North Am Small Anim Pract 1994;24(2): 335–66. Smeak DD, Crocker C. Fixed-head skin staplers: features and performance. Compend Contin Ed Pract Vet 1997;19: 1358–68. LaRue SM, Withrow SJ, Wykes PM. Lung resection using surgical staples in dogs and cats. Vet Surg 1987;16:238–40. Clark GN. Gastric surgery with surgical stapling instruments. Vet Clin North Am Small Anim Pract 1994;24:279–303. Fucci V, Newton JC, Hedlund CS, et al. Rectal surgery in the cat: comparison of suture versus staple technique through a dorsal approach. J Am Anim Hosp Assoc 1992;28:519–26. Kudisch M, Pavletic MM. Subtotal colectomy with surgical stapling instruments via a trans-cecal approach for treatment of acquired megacolon in the cat. Vet Surg 1993;22:457–63. http://www.infinitimedical.com/ p_stents_ureter.html. http://www.dextronix.com/ stentscatsanddogs. Choi R, Lee S, Hyun C. Urethral stenting in a cat with refractory obstructive feline lower urinary tract disease. J Vet Med Sci 2009;71:1255–9. Christensen NI, Culvenor J, Langova V. Fluoroscopic stent placement for the relief of malignant urethral obstruction in a cat. Aust Vet J 2010;88(12):478–82. Newman RG, Mehler SJ, Kitchell BE, Beal MW. Use of a balloon-expandable metallic stent to relieve malignant urethral obstruction in a cat. J Am Vet Med Assoc 2009;234:236–9. Culp WT, Weisse C, Cole SG, Solomon JA. Intraluminal tracheal stent placement in three cats. Vet Surg 2007;36:107–13.