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Techniques of Wound Closure
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Wound Management
Techniques of Wound Closure
Gayle W. Trotter, DVM, MS*
GENERAL CONSIDERATIONS The goal of suture repair of a wound is to achieve first intention healing, with both a functional and a cosmetic result. In this regard, it has been said that some surgeons consider "an open wound as an incomplete treatment or a challenge not met" .6 The decision for surgical closure should be based on when the wound environment is conducive to successful healing, which, with many equine wounds, often is not at the time of first examination. Generally, the decision for primary closure versus delayed closure is based subjectively on degree of contamination and damage to local blood supply. Crushing type injuries often have significant attendant tissue trauma that causes inhibition of local tissue defenses. Primary suture closure of these wounds often results in failure. By contrast, wounds made with a relatively clean, sharp object may be sufficiently resistant to infection to allow immediate suture closure. Primary surgical closure of wounds to certain anatomic regions (e.g., the head) is often successful, whereas the same treatment to a similar wound on the distal limbs might be unsuccessful. The veterinarian's role is to weigh all factors that might influence the final result before selecting a definitive course of treatment.
CHOOSING A SUTURE A number of factors enter into the decision on which suture material to use, and a working knowledge of the properties of absorbable and nonabsorbable suture materials is necessary. It has been stated that faults in making sutures lie with the manufacturers but errors in using sutures lie with the surgeon. 13 · 24 A general goal should be to use sufficiently strong *Diplomate, American College of Veterinary Surgeons; Associate Professor, Department of Clinical Sciences, Colorado State Unive rsity College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado Veterinary Clinics of North America: Equine Practice-Vol. 5, No. 3, December 1989
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suture material that has minimal tissue reactivity. The smallest size of suture material that meets this strength requirement should then be used. It is beyond the scope and intent of this chapter to describe advantages and disadvantages of different suture materials, but some salient features of the most commonly used materials are included. All suture materials potentiate infection when placed in contaminated wounds, with natural materials (catgut, silk) being significantly more harmful than synthetic materials. 21 • 22 Although monofilament materials are generally considered least likely to potentiate infection, it has also been shown that little difference exists between synthetic nonabsorbable monofilament sutures and synthetic multifilament absorbable sutures. Synthetic nonabsorbable multifilament sutures, however, are more prone to cause infection. 21 · 22 Generally, synthetic monofilament and multifilament absorbable sutures are buried in deeper tissue layers, and synthetic monofilament sutures are used in the skin. Hydrolysis rather than enzymatic digestion causes absorption of synthetic absorbable sutures, which makes them much less reactive than natural absorbable material (catgut) 4 in tissues. Loss of tensile strength after placement in tissues is also more predictable for synthetic absorbable sutures than it is for catgut. The tensile strength of many of the synthetic absorbable sutures in vitro is also greater than that of many nonabsorbable sutures including silk, polypropylene, and braided polyester suture materials. 3 Of some interest is the behavior of the relatively new monofilament absorbable polyglyconate (Maxon; Davis and Geck, Pearl River, NY), which has tremendous tensile strength in the dry state but in vivo behaves more like the synthetic multifilament absorbable sutures. In a study in which Maxon was compared to another absorbable monofilament polydioxanone (PDS; Ethicon, Somerville, NJ), Maxon lost 50 per cent of its tensile strength in vivo by 3 weeks versus 6 weeks for PDS . 3
MANAGEMENT OF DEAD SPACE Wound dead space must be effectively controlled to avoid wound infection. Through unknown mechanisms , dead space potentiates the infectivity of subinfective doses of bacteria. 9 Some evidence exists that dead space exudate is devoid of opsonins, and phagocytosis by neutrophils is therefore compromised. Fluid in dead space further prevents tissue apposition, which delays healing. Blood and other body fluids can act as culture media for bacteria, and hemoglobin interferes with chemotaxis of and killing by neutrophils. 9 In horses, large wounds to the body and chest often have large areas of potential dead space that must be managed during wound closure. Dead space may be dealt with in a number of ways. The time-honored principle of layered wound closure is one way in which this is accomplished. Not all wounds are amenable to simple layered closure, however, and alternative methods of dead space elimination must then be used. These include suture obliteration, drainage, bandages, or a combination of these methods. Although conflicting evidence exists regarding use of sutures to eliminate dead space, conclusions of most experimental studies are that
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sutures potentiate wound infection when used to eliminate dead space in contaminated wounds. 7 · 21 · 22 · 30 Degree of contamination is probably important, since in relatively clean wounds suture closure of dead space can be very effective . Complete obliteration of dead space using sutures does increase the amount of suture material in a wound. Needle passages through tissues created during dead space closure can also potentiate infection in contaminated wounds. 5 Therefore, the wound should be appropriately lavaged and debrided prior to suture closure of dead space, and the least amount of suture to achieve closure should be used. Synthetic absorbable rather than natural absorbable suture material should be used for dead space closure, owing to the reactivity of material such as catgut. 22 Sutures should be pulled snugly, but creation of local tissue ischemia from excessive tension should be avoided. With large skin flaps in horses, walking sutures can be used to advance the flap over the wound bed at the same time as dead space is eliminated. 27 These studies are started near the base of the skin flap, with the first bite taken in the deep dermis, followed by a bite taken in the wound tissue that is slightly closer to the center of the wound. In this fashion, the skin is gradually moved over the wound. To avoid inadvertent suture incorporation of blood vessels supplying the skin, these sutures should be placed in a direction parallel to the skin flap. Dead space can often be managed using compression bandages. This is true of many wounds to the body, chest, head or extremities (Fig. IA and B). Drains may have to be placed prior to bandaging if fluid accumulation is likely; however, drains should not be used unless fluid accumulation is very likely. In some areas where bandaging is impossible, a tie-over or stent bandage can be used to help counteract dead space (Fig. 2). Although objective data are lacking, this type of bandage is felt to aid in relief of incision line tension as well as provide counterpressure to areas of dead space.
MANAGEMENT OF SKIN TENSION When tissue has been lost, undue skin tension may result if closure is attempted, and healing by second intention will often be necessary. Even
Figure L A and B, Solt tissue support, using elastic bandage materials, is important in helping eliminate dead space in certain wounds. Insufficient soft tissue support results in failure of the suture obliteration of dead space.
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Figure 2. A tie-ove r or ste nt bandage can help obliterate dead space in wounds in which bandaging is not possible.
in wounds where primary closure is feasible , excessive tension may complicate healing. Numerous me thods exist, howeve r, whereby skin tension can b e diminished in wounds that are candidates for primary closure.
Undermining Even small increases in local tissue swelling sometimes can greatly increase the difficulty of skin closure, especially on the distal limbs of horses. Undermining can greatly facilitate apposition of such tissues. A combination of sharp and blunt scissor dissection is used to gain access to the natural tissue cleavage plane in the subcutaneous tissues. 27 Sharp scalpel dissection can also be used and may be preferred in certain situations, but risk of hemorrhage is increased, and it is more difficult to remain in the proper tissue plane when using a sharp scalpel. Undermining should be continued until skin edges can be brought into apposition without surrounding skin appearing tight or drawn. The surgeon's judgment must be used regarding the extent to which surrounding skin can be undermined . To the author's knowledge, objective information in this area is lacking. Undermining up to 4 cm on either side of experimental wounds created on equine metacarpi and metatarsi caused no complications. 1 In a clinical case involving a laceration over the metatarsus, undermining around almost the entire circumference of the metatarsus also did not cause a proble m. 1 This degree of undermining may be possible when the blood supply to the tissues being undermined has not been significantly compromised. Further skin necrosis might be expected if the surrounding tissues already have significant vascular compromise. When tissue is surgically unde rmined , no attempt is usually made to close this created "dead space" using sutures.
Relief Incisions Strategically located relief skin incisions away from the wound margins can sometimes greatly ease primary wound skin closure. 26 Good surgical
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judgment is needed in deciding how long to make such incisions, but generally they are continued until visible tension on the primary suture line is relieved. In some cases, relief incisions can be closed after undermining of adjacent tissues, whereas in other cases the relief incisions may need to heal by second intention (Fig. 3A and B). Bailey described a mesh expansion method of relief incisions to gain local skin expansion. 1 This technique is more applicable to delayed closure and scar revision and is described in the chapter on that subject (see Booth). Tension Sutures
Tension on skin flaps in humans can seriously affect local blood supply 18 but seems to be less of a problem in animals. In dogs it was shown that as long as blood supply to the base of skin flaps was intact, marked increases in skin tension did not result in skin necrosis. 19 The difference in skin blood supply between humans and dogs probably influences these results. Horses are probably more tolerant of skin tension than humans, but wound dehiscence is still often a sequel to excessive suture line tension, especially with wounds on the distal limb. Tension sutures are generally placed 2 to 4 cm away from wound margins and are used to draw the wound edges closer together so that definitive appositional closure can be completed (Fig. 4A and B). If necrosis occurred around tension sutures placed too close to the repaired wound, suture pull-through and dehiscence could follow. There are a variety of suture patterns called "tension suture" patterns. Perhaps the most common of these are simple interrupted tension sutures, horizontal and vertical mattress tension sutures, and far-and-near tension sutures. 25 · 26 Alternately spaced narrow and wide simple interrupted suture
Figure 3. A , A relief incision was used over the lateral aspect of the forearm to reduce tension on the primary suture lin e over the cranial aspect of the forearm. Exc:essive tension is noted as puckering of the skin along the midportion of the relief incision. B , A third, smaller reli e f incision was made and was le ft open to heal by second intention. Further healing was uneventful.
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Figure 4. A, Vertical mattress tension sutures have been placed along this oblique wound over the dorsal surface of the carpus. A Penrose drain exits through a stab incision ventral to the wound. B, Complete apposition is attained with simple interrupted appositional sutures. This wound would also require immobilization of the limb for successful healing.
bites may be placed, with the wide bites acting as tension sutures. 26 Horizontal mattress suture patterns are also commonly used but have the disadvantage of potentially compromising local blood supply, owing to the ir orientation relative to the wound (Fig. 5). Vertical mattress tension sutures are more commonly used because of less local vascular compromise (Figs.
Figure 5. H orizontal mattress tension sutures are oriented such that impairment to local circulation can occur. Rubber tubing has been used to distribute suture compression of local tissues.
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Figure 6. Vertical mattress tension sutures are effective and less inhibitory to local blood supply than horizontal mattress tension sutures. Rubber tubing has been used to distribute suture compression of local tissues.
6 and 7). If tension is not excessive, the suture bites nearest the wound margin can split the skin thickness and act as appositional sutures. With moderate to marked tension, both suture bites on each side of the wound are placed well back from the wound margin, and a separate line of appositional sutures is then placed. Some prefer to use one vertical mattress suture per five simple interrupted appositional sutures, whereas others alternate the use of these sutures. With both of these mattress patterns, suture supports may be necessary beneath the skin suture loop to further distribute pressure and prevent local necrosis. Such supports are called "quilled" support or "quilled" sutures. 27 This author prefers rubber intravenous tubing in such cases. When vertical mattress sutures are alternately placed close tc and further away from the wound margins and are combined with simple interrupted appositional sutures, the pattern is called an "echelon" pattern. 10 Two types of far-and-near suture patterns can also be used as tension sutures. Both patterns are considered to have a far tension component and a near appositional component (Fig. 8A and B). The far-far-near-near pattern
Figure 7. A, Vertical mattress tension sutures have been placed to help support the appositional suture line in this lacerated tongue. B, Further wound apposition is achieved using simple interrupted sutures.
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Figure 8. The far-far-near-near suture pattern (A) or the far-near-near-far suture pattern (B) can be used as both a tension suture and an appositional suture. The combination of a simple stitch and a simple loop gives these suture patterns increased strength over many other patterns.
has been called the most cosmetic of the tension suture patterns. Far and near suture patterns have been shown to be considerably stronger than simple interrupted and mattress suture patterns when tested in vitro. 15 In a study in which various suture patterns and techniques were evaluated, simple interrupted suture patterns were found to be slightly stronger than simple continuous suture patterns . The most striking finding, however, was the significantly increased strength of far and near patterns over all other suture patterns. The combination of a simple stitch and a simple loop was considered to be the reason for the increased strength of far and near patterns. Vertical and horizontal mattress suture patterns were found to be no stronger than a simple interrupted suture pattern. 15
FURTHER CONSIDERATIONS IN WOUND SUTURING It is not always clear whether a continuous or an interrupted suture pattern should be used. 2° Continuous patterns have the advantage of speed of application and only two knots. The entire suture line is vulnerable, however, if a problem develops with one of these knots . Experimentally, interrupted closure was associated with increased strength and less postoperative edema and induration than were associated with continuous closure. 15 • 25 On a weight-for-weight basis, though, interrupted suture patterns leave more suture material in wounds. 23 As previously discussed, suture material does potentiate infection in contaminated wounds . Therefore, in comparing potential advantages and disadvantages of buried suture patterns, interrupted sutures may be indicated when factors are present that may significantly impair or delay healing. Otherwise, continuous patterns should be used to decrease the amount of buried suture. Continuous dosure is currently used successfully by many equine surgeons to dose midline abdominal incisions, an area where significant impairment of wound healing would be unacceptable. 2~ As previously mentioned, other soft tissue support is often required to
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prevent wound dehiscence. Insufficient bandage support in some wounds can allow seromas to develop in dead space. In other wounds, external support may be needed to minimize motion (Fig. 9A, B, C) . (For a discussion of the role of immobilization in protecting wounds , see Lindsay.) Methods for closure of skin other than suture closure include wound tape, skin staples, and cyanoacrylates or wound glue. Tape wound closure is used commonly in humans and has definite advantages in certain situations (increased patient comfort, less infection when used in contaminated wounds, good wound strength). 9 Tape closure has not gained extensive use in veterinary medicine. Patients may remove tape before it is desired and growth of hair under the tape causes loosening. 27 Skin staples have become popular in veterinary medicine . Major benefits associated with their use is their ease and speed of application. Experimentally, metal clip wound closure has been associated with decreased wound strength when compared with use of conventional sutures. 11 Stainless steel staples, however, are associated with a good cosmetic result when used in people. In a study done in dogs , wound strength in stapled wounds was equivalent to that using conventional sutures. 4 • 12 Skin staples are routinely used at Colorado State University for skin closure of ventral midline celiotomy skin incisions. Staples are also occasionally used for skin closure of various elective incisions or wounds on the head and neck. A carefully placed subcutaneous suture line should be used to provide good apposition of the skin margins prior to staple placement. This decreases tension on the staple line and in this author's opinion, gives a more cosmetic result. Cyanoacrylates have been developed that can be used for a variety of purposes. In equine wounds, these compounds have been used either for skin apposition or to help control exuberant granulation tissue .2 Experimentally, glued
Figure 9. A , This 5-day-old laceration to the tip of the ear has been cleansed and debrided in preparation for closure. B, Simple inte rrupted sutures were used to appose the wound margins. C , A piece of radiographic film was trimmed to fit inside the ear. The film was fixed to the ear with sutures oriented parallel to the long axis of the ear. This suture orientation minimizes the chance of incorporating a blood vessel in the suture loop. The film acts as an internal splint to minimize moveme nt of the incision line.
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wounds in rats were stronger than conventionally sutured wounds for the first 4 to 6 days after wounding, but there was no difference after that time. It was also noted that the substance stayed in the wound for protracted periods of time. 14 Cyanoacrylates currently offer no advantage over conventional suturing in the management of equine wounds. Presuturing is a recently described technique that may prove efficacious in management of some equine wounds. 17 The technique has been evaluated experimentally in pigs and has also been used clinically in select cases in humans when a skin graft or excessive undermining would otherwise be required for skin closure. Presuturing probably has greatest potential application in equine wounds where delayed closure is being considered, and the technique will be described more completely in that chapter (see Booth). Its efficacy remains to be proven; an inherent disadvantage is the requirement for two general anesthetic episodes. Continuous passive motion is a modality that has proven beneficial in rabbits in promoting healing of both articular cartilage and wounds. 29 Despite potential be nefit from passive motion in horse wounds, immobilization is almost always required if first-intention healing is expected.
DRAINS
Drains play an important role in the successful management of some equine wounds . Their use remains controversial, however, and specific indications for which type of drain to use and duration of use cannot be given. Good surgical judgment based on available scientific information and previous experiences must be used . General advantages associated with use of drains in wounds include obliteration of dead space and prevention or elimination of fluid collections. 16 Opsonization of bacteria is decreased in some wound fluids , which inhibits phagocytosis by neutrophils. 18 Hemoglobin is recognized as an adjuvant substance in bacterial peritonitis, interfering with chemotaxis, phagocytosis, and bacterial killing by neutrophils. 9 Hemoglobin could play a similar role in wound seromas. Sterile blood in a wound may be of little conseque nce, but hematomas in general are known to enhance bacterial virulence. 9 D rains in wounds also have some disadvantages. Their use should never substitute for appropriate wound debridement and hemostasis. The lure to close and drain a wound that should really be left open must be avoided16 ; drains are foreign bodies and have some of the inherent disadvantages of sutures when they are placed in contaminated wounds. The exit site for a drain is also a potential portal of entry for bacteria and must be appropriately managed to prevent retrograde infections. In addition, some of the more rigid types of drains may cause patient discomfort. Drains may be active or passive, and numerous types are available . 16 It is not the intent of this discussion to describe drainage systems in detail. It is this author's opinion that simple drain systems appropriately placed work very effectively. The most common type of passive wound drain is the thin latex rubber Penrose drain, which depends on gravity to function
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properly. 16 • 18 These drains must exit near the most dependent part of a wound, which can be awkward with some wounds. The drain should also be exited through a portal separate from the incision to minimize the incidence of incisional infection (Fig. 10). Although the drain can be entered through a separate proximal stab incision, leaving the proximal portion of the drain buried decreases the opportunity for ascending infection. The proximal portion of the drain must be anchored in the wound with a loosely placed suture that exits the skin away from the wound margin. A wide variety of active drainage systems are also available. 16 These systems can be either open or closed, with the closed system being most common. The advantages of closed suction systems is that incidence of ascending infections is minimized, wound dressings can be kept dry, and continuous drainage is provided (Fig. 11). 16 The suction apparatus can be bandaged, taped, or tied to the animal, but maintenance of some of the more bulky devices can be awkward. Another problem associated with closed suction drains is plugging of the drain openings. Heparinizing the drain prior to placement can lessen this problem, but drain obstruction can still be a frustrating complication. Sump (double- or triple-lumen) drains have a large draining lumen and a smaller sump lumen that are meant to make them more efficient and to keep them patent longer than singlelumen suction drains. 16 Irrigating solutions can also be introduced through one of the channels with triple-lumen drains. This author has found that
Figure 10. This Penrose drain is fixed with a suture to retain it proximally and is exited through a stab incision away from the wound.
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Figure 11. A relatively simple closed suction drain uses fenestrated tubing, a 3-way stopcock, and a syringe with a needle through the plunger to act as a stay.
the single-lumen, multifenestrated drain with syringe suction suffices in cases in which closed suction is required. A personal preference also exists for a separate proximal ingress portal, when wound lavage is indicated. Some wounds that are closed and provided with ingress lavage and egress drainage are probably better candidates for delayed closure or second intention healing.
REFERENCES 1. Bailey J, Jacobs K: The mesh expansion method of suturing wounds on the legs of horses . Ve t Surg 12:78, 1983 2. Blackford J, Shires M , Goble D, et al: The use of N-butyl cyanoacrylate in the treatment of open leg wounds in the horse . Am Assoc Equine Pract 32:349, 1986 3. Bourne R, Bitar H, Andreae P, et al: In vivo comparison of four absorbable sutures: Vicryl, Dexon Plus, Maxon and PDS. Can J Surg 31:43, 1988 4. Capperauld I , Bucknall T: Sutures and dressings. In Bucknall T, Ellis H: Wound Healing for Surgeons. London , Bailliere Tindall, 1984, p 75 5. Condie J, Ferguson D : Experimental wound infections: Contamination versus surgical technique. Surgery 50:367, 1961 6. Daly W: Wound infections. In Slatter DH (ed): Textbook of Small Animal Surgery, vol I. Philadelphia, WB Saunders, 1985, p 37 7. deHoll D , Rodeheaver G, Edgerton M, et al: Potentiation of infection by suture closure of dead space. Am J Surg 127:716, 1974 8. Edlich R, Panek P, Rode heaver G, et al: Surgical sutures and infection: A biomaterial evaluation. J Biomed Mater Res Symposium 5:115, 1974 9. Edlich R, Rode heaver G, Thacker J: Technical factors in the prevention of wound infections. In Simmons RL, Howard RJ (eds): Surgical Infectious Diseases, New York, Appleton-Century-Crofts, 1982, p 449 10. Hackett R: Delayed wound closure: A review and report of use of the technique on three equin e limb wounds. Vet Surg 12:48, 1983 11. Harrison I, Williams D, Cuschieri A: The effect of metal clips on the te nsile properties of healing skin wounds. Br J Surg 62:945, 1975 12. Hess J, De Young D, Riley M, et al: Comparison of stainless steel staple and synthetic suture material on wound healing. J Am Anim Hosp Assoc 15:501, 1979 13. Knowles R: Critique of suture mate rials in small animal surgery. J Am Anim Hosp Assoc 12:670, 1976 14. Lamborn P, Soloway H, Matsumoto T, et al: Comparison of tensile strength of wounds closed by sutures and cyanoacrylates. Am J Vet Res 31: 125, 1970 15. Larse n J, Ulin A: Tensile strength advantage of the far-and-near suture technique . Surg Gyn Obste t 131: 123, 1970 16. Lee A, Swaim S, Henderson R: Surgical drainage . Compend Conlin Educ Pract Vet 8:94, 1986
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17. Liang M, Briggs P, Heckle r F, et al: Presuturing-a new technique for closin g large skin defects: Clinical and experime ntal studies. Plast Reconstr Surg 81:694, 1988 18. Moss J: Historical and cu rrent perspectives on surgical drainage. Surg Gyn Obstet 152:517, 1981 19. Mye rs B, Combs B, Cohen G: Wound tension and wound slough: A negative correlation. Am J Surg 109:711, 1965 20. Nelson E, Funakoshi E , O' Leary T: A comparison of the continuous and inte rrupted suturing techniques. J Pe riodont 48:273, 1977 21. Paterson-Brown S, Cheslyn -Curtis S, Biglin J, et al: Suture mate rials in contaminated wounds: a de tailed comparison of a new suture with those currently in use . Br J Surg 74:734, 1987 22. Sharp W , Belden T, King P, et al: Suture resistance to infection. Surgery 91:61, 1982 23. Smellie G: Continuous versus interrupted suture: A study on a we ight-for-weight basis. J Royal Coll Surg 14:345, 1969 24. Synder C: On the history of the suture . Plast Reconstr Surg 58:401, 1976 25. Speer D: The influe nce of suture technique on early wound healing. J Surg Res 27:385, 1979 26. Swaim S: Management of skin tension in dermal surgery. Comp Con tin Educ 2:758, 1980 27. Swaim S: Surgery of Traumatized Skin: Management and Reconstruction in the Dog and Cat. Philadelphia, WB Saunders Co, 1980, p 119 28. Turne r AS , Yovich J, White N, et al: Continuous absorbable suture pattern in the closure of ventral midline abdominal incisions in horses. Equine Vet J 20:401 , 1988 29. van Royen B, O 'Driscoll S, Dhe rt W, et al: A comparison of the effects of immobilization and continuous passive motion on surgical wound healing in mature rabbits. Plast Reconstr Surg 78:360, 1986 30. Varma S, John son L, Ferguson H , et al: Tiss ue reaction to suture materials in infected su rgical wounds-A histopathologic evaluation . Am J Vet Res 42:563, 1981 Department of Clinical Sciences College of Veterinary Medicine and Biomedical Sciences Colorado State Unive rsity Fort Collins, CO 80523
Wound Management
Techniques of Wound Closure
Gayle W. Trotter, DVM, MS*
GENERAL CONSIDERATIONS The goal of suture repair of a wound is to achieve first intention healing, with both a functional and a cosmetic result. In this regard, it has been said that some surgeons consider "an open wound as an incomplete treatment or a challenge not met" .6 The decision for surgical closure should be based on when the wound environment is conducive to successful healing, which, with many equine wounds, often is not at the time of first examination. Generally, the decision for primary closure versus delayed closure is based subjectively on degree of contamination and damage to local blood supply. Crushing type injuries often have significant attendant tissue trauma that causes inhibition of local tissue defenses. Primary suture closure of these wounds often results in failure. By contrast, wounds made with a relatively clean, sharp object may be sufficiently resistant to infection to allow immediate suture closure. Primary surgical closure of wounds to certain anatomic regions (e.g., the head) is often successful, whereas the same treatment to a similar wound on the distal limbs might be unsuccessful. The veterinarian's role is to weigh all factors that might influence the final result before selecting a definitive course of treatment.
CHOOSING A SUTURE A number of factors enter into the decision on which suture material to use, and a working knowledge of the properties of absorbable and nonabsorbable suture materials is necessary. It has been stated that faults in making sutures lie with the manufacturers but errors in using sutures lie with the surgeon. 13 · 24 A general goal should be to use sufficiently strong *Diplomate, American College of Veterinary Surgeons; Associate Professor, Department of Clinical Sciences, Colorado State Unive rsity College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado Veterinary Clinics of North America: Equine Practice-Vol. 5, No. 3, December 1989
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suture material that has minimal tissue reactivity. The smallest size of suture material that meets this strength requirement should then be used. It is beyond the scope and intent of this chapter to describe advantages and disadvantages of different suture materials, but some salient features of the most commonly used materials are included. All suture materials potentiate infection when placed in contaminated wounds, with natural materials (catgut, silk) being significantly more harmful than synthetic materials. 21 • 22 Although monofilament materials are generally considered least likely to potentiate infection, it has also been shown that little difference exists between synthetic nonabsorbable monofilament sutures and synthetic multifilament absorbable sutures. Synthetic nonabsorbable multifilament sutures, however, are more prone to cause infection. 21 · 22 Generally, synthetic monofilament and multifilament absorbable sutures are buried in deeper tissue layers, and synthetic monofilament sutures are used in the skin. Hydrolysis rather than enzymatic digestion causes absorption of synthetic absorbable sutures, which makes them much less reactive than natural absorbable material (catgut) 4 in tissues. Loss of tensile strength after placement in tissues is also more predictable for synthetic absorbable sutures than it is for catgut. The tensile strength of many of the synthetic absorbable sutures in vitro is also greater than that of many nonabsorbable sutures including silk, polypropylene, and braided polyester suture materials. 3 Of some interest is the behavior of the relatively new monofilament absorbable polyglyconate (Maxon; Davis and Geck, Pearl River, NY), which has tremendous tensile strength in the dry state but in vivo behaves more like the synthetic multifilament absorbable sutures. In a study in which Maxon was compared to another absorbable monofilament polydioxanone (PDS; Ethicon, Somerville, NJ), Maxon lost 50 per cent of its tensile strength in vivo by 3 weeks versus 6 weeks for PDS . 3
MANAGEMENT OF DEAD SPACE Wound dead space must be effectively controlled to avoid wound infection. Through unknown mechanisms , dead space potentiates the infectivity of subinfective doses of bacteria. 9 Some evidence exists that dead space exudate is devoid of opsonins, and phagocytosis by neutrophils is therefore compromised. Fluid in dead space further prevents tissue apposition, which delays healing. Blood and other body fluids can act as culture media for bacteria, and hemoglobin interferes with chemotaxis of and killing by neutrophils. 9 In horses, large wounds to the body and chest often have large areas of potential dead space that must be managed during wound closure. Dead space may be dealt with in a number of ways. The time-honored principle of layered wound closure is one way in which this is accomplished. Not all wounds are amenable to simple layered closure, however, and alternative methods of dead space elimination must then be used. These include suture obliteration, drainage, bandages, or a combination of these methods. Although conflicting evidence exists regarding use of sutures to eliminate dead space, conclusions of most experimental studies are that
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sutures potentiate wound infection when used to eliminate dead space in contaminated wounds. 7 · 21 · 22 · 30 Degree of contamination is probably important, since in relatively clean wounds suture closure of dead space can be very effective . Complete obliteration of dead space using sutures does increase the amount of suture material in a wound. Needle passages through tissues created during dead space closure can also potentiate infection in contaminated wounds. 5 Therefore, the wound should be appropriately lavaged and debrided prior to suture closure of dead space, and the least amount of suture to achieve closure should be used. Synthetic absorbable rather than natural absorbable suture material should be used for dead space closure, owing to the reactivity of material such as catgut. 22 Sutures should be pulled snugly, but creation of local tissue ischemia from excessive tension should be avoided. With large skin flaps in horses, walking sutures can be used to advance the flap over the wound bed at the same time as dead space is eliminated. 27 These studies are started near the base of the skin flap, with the first bite taken in the deep dermis, followed by a bite taken in the wound tissue that is slightly closer to the center of the wound. In this fashion, the skin is gradually moved over the wound. To avoid inadvertent suture incorporation of blood vessels supplying the skin, these sutures should be placed in a direction parallel to the skin flap. Dead space can often be managed using compression bandages. This is true of many wounds to the body, chest, head or extremities (Fig. IA and B). Drains may have to be placed prior to bandaging if fluid accumulation is likely; however, drains should not be used unless fluid accumulation is very likely. In some areas where bandaging is impossible, a tie-over or stent bandage can be used to help counteract dead space (Fig. 2). Although objective data are lacking, this type of bandage is felt to aid in relief of incision line tension as well as provide counterpressure to areas of dead space.
MANAGEMENT OF SKIN TENSION When tissue has been lost, undue skin tension may result if closure is attempted, and healing by second intention will often be necessary. Even
Figure L A and B, Solt tissue support, using elastic bandage materials, is important in helping eliminate dead space in certain wounds. Insufficient soft tissue support results in failure of the suture obliteration of dead space.
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Figure 2. A tie-ove r or ste nt bandage can help obliterate dead space in wounds in which bandaging is not possible.
in wounds where primary closure is feasible , excessive tension may complicate healing. Numerous me thods exist, howeve r, whereby skin tension can b e diminished in wounds that are candidates for primary closure.
Undermining Even small increases in local tissue swelling sometimes can greatly increase the difficulty of skin closure, especially on the distal limbs of horses. Undermining can greatly facilitate apposition of such tissues. A combination of sharp and blunt scissor dissection is used to gain access to the natural tissue cleavage plane in the subcutaneous tissues. 27 Sharp scalpel dissection can also be used and may be preferred in certain situations, but risk of hemorrhage is increased, and it is more difficult to remain in the proper tissue plane when using a sharp scalpel. Undermining should be continued until skin edges can be brought into apposition without surrounding skin appearing tight or drawn. The surgeon's judgment must be used regarding the extent to which surrounding skin can be undermined . To the author's knowledge, objective information in this area is lacking. Undermining up to 4 cm on either side of experimental wounds created on equine metacarpi and metatarsi caused no complications. 1 In a clinical case involving a laceration over the metatarsus, undermining around almost the entire circumference of the metatarsus also did not cause a proble m. 1 This degree of undermining may be possible when the blood supply to the tissues being undermined has not been significantly compromised. Further skin necrosis might be expected if the surrounding tissues already have significant vascular compromise. When tissue is surgically unde rmined , no attempt is usually made to close this created "dead space" using sutures.
Relief Incisions Strategically located relief skin incisions away from the wound margins can sometimes greatly ease primary wound skin closure. 26 Good surgical
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judgment is needed in deciding how long to make such incisions, but generally they are continued until visible tension on the primary suture line is relieved. In some cases, relief incisions can be closed after undermining of adjacent tissues, whereas in other cases the relief incisions may need to heal by second intention (Fig. 3A and B). Bailey described a mesh expansion method of relief incisions to gain local skin expansion. 1 This technique is more applicable to delayed closure and scar revision and is described in the chapter on that subject (see Booth). Tension Sutures
Tension on skin flaps in humans can seriously affect local blood supply 18 but seems to be less of a problem in animals. In dogs it was shown that as long as blood supply to the base of skin flaps was intact, marked increases in skin tension did not result in skin necrosis. 19 The difference in skin blood supply between humans and dogs probably influences these results. Horses are probably more tolerant of skin tension than humans, but wound dehiscence is still often a sequel to excessive suture line tension, especially with wounds on the distal limb. Tension sutures are generally placed 2 to 4 cm away from wound margins and are used to draw the wound edges closer together so that definitive appositional closure can be completed (Fig. 4A and B). If necrosis occurred around tension sutures placed too close to the repaired wound, suture pull-through and dehiscence could follow. There are a variety of suture patterns called "tension suture" patterns. Perhaps the most common of these are simple interrupted tension sutures, horizontal and vertical mattress tension sutures, and far-and-near tension sutures. 25 · 26 Alternately spaced narrow and wide simple interrupted suture
Figure 3. A , A relief incision was used over the lateral aspect of the forearm to reduce tension on the primary suture lin e over the cranial aspect of the forearm. Exc:essive tension is noted as puckering of the skin along the midportion of the relief incision. B , A third, smaller reli e f incision was made and was le ft open to heal by second intention. Further healing was uneventful.
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Figure 4. A, Vertical mattress tension sutures have been placed along this oblique wound over the dorsal surface of the carpus. A Penrose drain exits through a stab incision ventral to the wound. B, Complete apposition is attained with simple interrupted appositional sutures. This wound would also require immobilization of the limb for successful healing.
bites may be placed, with the wide bites acting as tension sutures. 26 Horizontal mattress suture patterns are also commonly used but have the disadvantage of potentially compromising local blood supply, owing to the ir orientation relative to the wound (Fig. 5). Vertical mattress tension sutures are more commonly used because of less local vascular compromise (Figs.
Figure 5. H orizontal mattress tension sutures are oriented such that impairment to local circulation can occur. Rubber tubing has been used to distribute suture compression of local tissues.
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Figure 6. Vertical mattress tension sutures are effective and less inhibitory to local blood supply than horizontal mattress tension sutures. Rubber tubing has been used to distribute suture compression of local tissues.
6 and 7). If tension is not excessive, the suture bites nearest the wound margin can split the skin thickness and act as appositional sutures. With moderate to marked tension, both suture bites on each side of the wound are placed well back from the wound margin, and a separate line of appositional sutures is then placed. Some prefer to use one vertical mattress suture per five simple interrupted appositional sutures, whereas others alternate the use of these sutures. With both of these mattress patterns, suture supports may be necessary beneath the skin suture loop to further distribute pressure and prevent local necrosis. Such supports are called "quilled" support or "quilled" sutures. 27 This author prefers rubber intravenous tubing in such cases. When vertical mattress sutures are alternately placed close tc and further away from the wound margins and are combined with simple interrupted appositional sutures, the pattern is called an "echelon" pattern. 10 Two types of far-and-near suture patterns can also be used as tension sutures. Both patterns are considered to have a far tension component and a near appositional component (Fig. 8A and B). The far-far-near-near pattern
Figure 7. A, Vertical mattress tension sutures have been placed to help support the appositional suture line in this lacerated tongue. B, Further wound apposition is achieved using simple interrupted sutures.
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Figure 8. The far-far-near-near suture pattern (A) or the far-near-near-far suture pattern (B) can be used as both a tension suture and an appositional suture. The combination of a simple stitch and a simple loop gives these suture patterns increased strength over many other patterns.
has been called the most cosmetic of the tension suture patterns. Far and near suture patterns have been shown to be considerably stronger than simple interrupted and mattress suture patterns when tested in vitro. 15 In a study in which various suture patterns and techniques were evaluated, simple interrupted suture patterns were found to be slightly stronger than simple continuous suture patterns . The most striking finding, however, was the significantly increased strength of far and near patterns over all other suture patterns. The combination of a simple stitch and a simple loop was considered to be the reason for the increased strength of far and near patterns. Vertical and horizontal mattress suture patterns were found to be no stronger than a simple interrupted suture pattern. 15
FURTHER CONSIDERATIONS IN WOUND SUTURING It is not always clear whether a continuous or an interrupted suture pattern should be used. 2° Continuous patterns have the advantage of speed of application and only two knots. The entire suture line is vulnerable, however, if a problem develops with one of these knots . Experimentally, interrupted closure was associated with increased strength and less postoperative edema and induration than were associated with continuous closure. 15 • 25 On a weight-for-weight basis, though, interrupted suture patterns leave more suture material in wounds. 23 As previously discussed, suture material does potentiate infection in contaminated wounds . Therefore, in comparing potential advantages and disadvantages of buried suture patterns, interrupted sutures may be indicated when factors are present that may significantly impair or delay healing. Otherwise, continuous patterns should be used to decrease the amount of buried suture. Continuous dosure is currently used successfully by many equine surgeons to dose midline abdominal incisions, an area where significant impairment of wound healing would be unacceptable. 2~ As previously mentioned, other soft tissue support is often required to
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prevent wound dehiscence. Insufficient bandage support in some wounds can allow seromas to develop in dead space. In other wounds, external support may be needed to minimize motion (Fig. 9A, B, C) . (For a discussion of the role of immobilization in protecting wounds , see Lindsay.) Methods for closure of skin other than suture closure include wound tape, skin staples, and cyanoacrylates or wound glue. Tape wound closure is used commonly in humans and has definite advantages in certain situations (increased patient comfort, less infection when used in contaminated wounds, good wound strength). 9 Tape closure has not gained extensive use in veterinary medicine. Patients may remove tape before it is desired and growth of hair under the tape causes loosening. 27 Skin staples have become popular in veterinary medicine . Major benefits associated with their use is their ease and speed of application. Experimentally, metal clip wound closure has been associated with decreased wound strength when compared with use of conventional sutures. 11 Stainless steel staples, however, are associated with a good cosmetic result when used in people. In a study done in dogs , wound strength in stapled wounds was equivalent to that using conventional sutures. 4 • 12 Skin staples are routinely used at Colorado State University for skin closure of ventral midline celiotomy skin incisions. Staples are also occasionally used for skin closure of various elective incisions or wounds on the head and neck. A carefully placed subcutaneous suture line should be used to provide good apposition of the skin margins prior to staple placement. This decreases tension on the staple line and in this author's opinion, gives a more cosmetic result. Cyanoacrylates have been developed that can be used for a variety of purposes. In equine wounds, these compounds have been used either for skin apposition or to help control exuberant granulation tissue .2 Experimentally, glued
Figure 9. A , This 5-day-old laceration to the tip of the ear has been cleansed and debrided in preparation for closure. B, Simple inte rrupted sutures were used to appose the wound margins. C , A piece of radiographic film was trimmed to fit inside the ear. The film was fixed to the ear with sutures oriented parallel to the long axis of the ear. This suture orientation minimizes the chance of incorporating a blood vessel in the suture loop. The film acts as an internal splint to minimize moveme nt of the incision line.
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wounds in rats were stronger than conventionally sutured wounds for the first 4 to 6 days after wounding, but there was no difference after that time. It was also noted that the substance stayed in the wound for protracted periods of time. 14 Cyanoacrylates currently offer no advantage over conventional suturing in the management of equine wounds. Presuturing is a recently described technique that may prove efficacious in management of some equine wounds. 17 The technique has been evaluated experimentally in pigs and has also been used clinically in select cases in humans when a skin graft or excessive undermining would otherwise be required for skin closure. Presuturing probably has greatest potential application in equine wounds where delayed closure is being considered, and the technique will be described more completely in that chapter (see Booth). Its efficacy remains to be proven; an inherent disadvantage is the requirement for two general anesthetic episodes. Continuous passive motion is a modality that has proven beneficial in rabbits in promoting healing of both articular cartilage and wounds. 29 Despite potential be nefit from passive motion in horse wounds, immobilization is almost always required if first-intention healing is expected.
DRAINS
Drains play an important role in the successful management of some equine wounds . Their use remains controversial, however, and specific indications for which type of drain to use and duration of use cannot be given. Good surgical judgment based on available scientific information and previous experiences must be used . General advantages associated with use of drains in wounds include obliteration of dead space and prevention or elimination of fluid collections. 16 Opsonization of bacteria is decreased in some wound fluids , which inhibits phagocytosis by neutrophils. 18 Hemoglobin is recognized as an adjuvant substance in bacterial peritonitis, interfering with chemotaxis, phagocytosis, and bacterial killing by neutrophils. 9 Hemoglobin could play a similar role in wound seromas. Sterile blood in a wound may be of little conseque nce, but hematomas in general are known to enhance bacterial virulence. 9 D rains in wounds also have some disadvantages. Their use should never substitute for appropriate wound debridement and hemostasis. The lure to close and drain a wound that should really be left open must be avoided16 ; drains are foreign bodies and have some of the inherent disadvantages of sutures when they are placed in contaminated wounds. The exit site for a drain is also a potential portal of entry for bacteria and must be appropriately managed to prevent retrograde infections. In addition, some of the more rigid types of drains may cause patient discomfort. Drains may be active or passive, and numerous types are available . 16 It is not the intent of this discussion to describe drainage systems in detail. It is this author's opinion that simple drain systems appropriately placed work very effectively. The most common type of passive wound drain is the thin latex rubber Penrose drain, which depends on gravity to function
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properly. 16 • 18 These drains must exit near the most dependent part of a wound, which can be awkward with some wounds. The drain should also be exited through a portal separate from the incision to minimize the incidence of incisional infection (Fig. 10). Although the drain can be entered through a separate proximal stab incision, leaving the proximal portion of the drain buried decreases the opportunity for ascending infection. The proximal portion of the drain must be anchored in the wound with a loosely placed suture that exits the skin away from the wound margin. A wide variety of active drainage systems are also available. 16 These systems can be either open or closed, with the closed system being most common. The advantages of closed suction systems is that incidence of ascending infections is minimized, wound dressings can be kept dry, and continuous drainage is provided (Fig. 11). 16 The suction apparatus can be bandaged, taped, or tied to the animal, but maintenance of some of the more bulky devices can be awkward. Another problem associated with closed suction drains is plugging of the drain openings. Heparinizing the drain prior to placement can lessen this problem, but drain obstruction can still be a frustrating complication. Sump (double- or triple-lumen) drains have a large draining lumen and a smaller sump lumen that are meant to make them more efficient and to keep them patent longer than singlelumen suction drains. 16 Irrigating solutions can also be introduced through one of the channels with triple-lumen drains. This author has found that
Figure 10. This Penrose drain is fixed with a suture to retain it proximally and is exited through a stab incision away from the wound.
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Figure 11. A relatively simple closed suction drain uses fenestrated tubing, a 3-way stopcock, and a syringe with a needle through the plunger to act as a stay.
the single-lumen, multifenestrated drain with syringe suction suffices in cases in which closed suction is required. A personal preference also exists for a separate proximal ingress portal, when wound lavage is indicated. Some wounds that are closed and provided with ingress lavage and egress drainage are probably better candidates for delayed closure or second intention healing.
REFERENCES 1. Bailey J, Jacobs K: The mesh expansion method of suturing wounds on the legs of horses . Ve t Surg 12:78, 1983 2. Blackford J, Shires M , Goble D, et al: The use of N-butyl cyanoacrylate in the treatment of open leg wounds in the horse . Am Assoc Equine Pract 32:349, 1986 3. Bourne R, Bitar H, Andreae P, et al: In vivo comparison of four absorbable sutures: Vicryl, Dexon Plus, Maxon and PDS. Can J Surg 31:43, 1988 4. Capperauld I , Bucknall T: Sutures and dressings. In Bucknall T, Ellis H: Wound Healing for Surgeons. London , Bailliere Tindall, 1984, p 75 5. Condie J, Ferguson D : Experimental wound infections: Contamination versus surgical technique. Surgery 50:367, 1961 6. Daly W: Wound infections. In Slatter DH (ed): Textbook of Small Animal Surgery, vol I. Philadelphia, WB Saunders, 1985, p 37 7. deHoll D , Rodeheaver G, Edgerton M, et al: Potentiation of infection by suture closure of dead space. Am J Surg 127:716, 1974 8. Edlich R, Panek P, Rode heaver G, et al: Surgical sutures and infection: A biomaterial evaluation. J Biomed Mater Res Symposium 5:115, 1974 9. Edlich R, Rode heaver G, Thacker J: Technical factors in the prevention of wound infections. In Simmons RL, Howard RJ (eds): Surgical Infectious Diseases, New York, Appleton-Century-Crofts, 1982, p 449 10. Hackett R: Delayed wound closure: A review and report of use of the technique on three equin e limb wounds. Vet Surg 12:48, 1983 11. Harrison I, Williams D, Cuschieri A: The effect of metal clips on the te nsile properties of healing skin wounds. Br J Surg 62:945, 1975 12. Hess J, De Young D, Riley M, et al: Comparison of stainless steel staple and synthetic suture material on wound healing. J Am Anim Hosp Assoc 15:501, 1979 13. Knowles R: Critique of suture mate rials in small animal surgery. J Am Anim Hosp Assoc 12:670, 1976 14. Lamborn P, Soloway H, Matsumoto T, et al: Comparison of tensile strength of wounds closed by sutures and cyanoacrylates. Am J Vet Res 31: 125, 1970 15. Larse n J, Ulin A: Tensile strength advantage of the far-and-near suture technique . Surg Gyn Obste t 131: 123, 1970 16. Lee A, Swaim S, Henderson R: Surgical drainage . Compend Conlin Educ Pract Vet 8:94, 1986
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17. Liang M, Briggs P, Heckle r F, et al: Presuturing-a new technique for closin g large skin defects: Clinical and experime ntal studies. Plast Reconstr Surg 81:694, 1988 18. Moss J: Historical and cu rrent perspectives on surgical drainage. Surg Gyn Obstet 152:517, 1981 19. Mye rs B, Combs B, Cohen G: Wound tension and wound slough: A negative correlation. Am J Surg 109:711, 1965 20. Nelson E, Funakoshi E , O' Leary T: A comparison of the continuous and inte rrupted suturing techniques. J Pe riodont 48:273, 1977 21. Paterson-Brown S, Cheslyn -Curtis S, Biglin J, et al: Suture mate rials in contaminated wounds: a de tailed comparison of a new suture with those currently in use . Br J Surg 74:734, 1987 22. Sharp W , Belden T, King P, et al: Suture resistance to infection. Surgery 91:61, 1982 23. Smellie G: Continuous versus interrupted suture: A study on a we ight-for-weight basis. J Royal Coll Surg 14:345, 1969 24. Synder C: On the history of the suture . Plast Reconstr Surg 58:401, 1976 25. Speer D: The influe nce of suture technique on early wound healing. J Surg Res 27:385, 1979 26. Swaim S: Management of skin tension in dermal surgery. Comp Con tin Educ 2:758, 1980 27. Swaim S: Surgery of Traumatized Skin: Management and Reconstruction in the Dog and Cat. Philadelphia, WB Saunders Co, 1980, p 119 28. Turne r AS , Yovich J, White N, et al: Continuous absorbable suture pattern in the closure of ventral midline abdominal incisions in horses. Equine Vet J 20:401 , 1988 29. van Royen B, O 'Driscoll S, Dhe rt W, et al: A comparison of the effects of immobilization and continuous passive motion on surgical wound healing in mature rabbits. Plast Reconstr Surg 78:360, 1986 30. Varma S, John son L, Ferguson H , et al: Tiss ue reaction to suture materials in infected su rgical wounds-A histopathologic evaluation . Am J Vet Res 42:563, 1981 Department of Clinical Sciences College of Veterinary Medicine and Biomedical Sciences Colorado State Unive rsity Fort Collins, CO 80523