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Paired skin incisions were made in 6 cats and closed intradermally with the copolymer of glycolide, -caprolacton, and trimethylene-carbonate, or polypropylene suture. The macroscopic and histologic appearance of the incisions was compared. Polypropylene suture compared favorably to glycolide, -caprolacton, and trimethylene-carbonate suture for closure of skin incisions in cats.
Comparaison des sutures absorbables et non absorbables pour la fermeture intradermique chez les chats. Des incisions de la peau appariées ont été pratiquées chez 6 chats et fermées de manière intradermique avec du copolymère de glycolide, de l’-caprolactone et du trimèthylène-carbonate ou des sutures de polypropylène. L’apparence macroscopique et histologique des incisions a été comparée. Les sutures de polypropylène offraient une comparaison favorable aux sutures de glycolide, d’-caprolactone et de triméthylène-carbonate pour la fermeture des incisions de la peau chez les chats.
(Traduit par Isabelle Vallières)
The buried continuous intradermal skin closure has become increasingly popular in both elective and non-elective surgical procedures in small animals (1–3). Potential advantages of the buried continuous intradermal closure pattern include elimination of the need for suture removal especially in elective surgical procedures, decreased scar formation because of promotion of epithelialization due to adequate skin apposition and minimal skin tension, reduction of tissue inflammation and risk of infection by avoiding formation of percutaneous suture tracts, and reduction of self-induced trauma because no suture material is exposed to the environment. However, the buried continuous intradermal closure is presumably more technically demanding and time consuming than the traditional percutaneous suture techniques (1–3).
Monofilament or multifilament suture materials have been used intradermally for closure of skin incisions in dogs, cats, and humans (2–8), but there are no studies in the veterinary literature comparing absorbable and nonabsorbable monofilament suture material for a continuous intradermal closure in small animals. The copolymer of glycolide, -caprolacton, and trimethylene-carbonate (Monosyn, B. Braun Aesculap AG & Co KG, Tuttlingen, Germany) is a rapidly absorbed suture that maintains approximately 50% of its knot tensile strength after 2 wk of implantation (9,10). Polypropylene suture, a reverse cutting needle, and 2 polypropylene attachment clips (Securex; B. Braun Aesculap AG & Co KG, Tuttlingen, Germany) may also be used for intradermal skin closure. The objective of the present study was to compare the macroscopic and histologic performance of an absorbable suture (glycolide, -caprolacton, and trimethylene-carbonate) with a nonabsorbable suture (polypropylene) for intradermal skin closure in cats.
The study was carried out with the approval of the ethics committee of the State Veterinary Authorities. Six healthy intact male domestic shorthair cats entered the study. All animals were premedicated with medetomidine (Domitor; Orion Corporation, Espoo, Finland), 50 μg/kg, IM, and butorphanol (Butomidor; Richter Pharma AG, Wels, Austria), 50 μg/kg, IM. Thirty minutes later anaesthesia was induced with propofol (Propofol; Fresenius Kabi, Athens, Greece), 1 to 2 mg/kg, IV, and maintained with isoflurane in oxygen, delivered via a non-rebreathing anesthetic circuit. After induction of anesthesia the ventral abdomen was clipped and prepared for aseptic surgery using chlorhexidine gluconate scrub 4% (Hibitane scrub; Astra Zeneca, London, United Kingdom) followed by chlorhexidne gluconate solution 0.5% diluted in 60% isopropyl alcohol. Each animal received 20 mg/kg of intravenous cefazolin (Vifazolin; Fujisawa Pharmaceutical, Osaka, Japan) at the time of induction of anesthesia. Two 5-cm long incisions positioned 3 cm apart and 0.5 cm caudal to the umbilicus were performed in each animal through the skin and subcutaneous tissue (to the level of the external fascial sheath of the rectus abdominis muscle) on the ventral midline.
Each incision had a 2-layer closure. The first layer, consisted of a simple continuous pattern of 3/0 glycolide, -caprolacton, and trimethylene-carbonate suture made with a reverse cutting needle and placed in the subcutaneous tissue; the thickness of the subcutaneous tissue was similar for the 2 incisions. This was followed by a continuous intradermal pattern with either 4/0 glycolide, -caprolacton and trimethylene-carbonate (incision M), or 4/0 polypropylene suture in a reverse cutting needle (incision S). For polypropylene closure, the suture was anchored to one end of the wound with a fixation clip just before the commissure of the wound and the needle was passed from this point through the wound commissure. The suturing was continued by passing the needle horizontally through the dermis. On the final bite the needle passed through the full thickness of the skin, and the suture was secured through a fixation clip. The skin closure techniques were randomly assigned so the surgical site would not influence the results.
All animals received oral meloxicam (Metacam; Boehringer Ingelheim, Ingelheim, Germany) at a dose of 0.05 mg/kg, q24h, for postoperative analgesia, starting 1 d after surgery for 4 d. Age, weight, and duration of the surgical procedure were recorded. All surgeries were performed by the same surgeon (LGP). The incisions were evaluated once daily for 9 d by the same clinician (VT) not involved in the surgical procedure, starting from the day after surgery (day 1), using a modified scale adapted from a previously published protocol (11): grade 1 — no visible reaction; grade 2 — mild swelling; grade 3 — suture line inflammation > 1-cm thickness with pain and redness; grade 4 — seroma or abscess formation requiring clinical treatment; and grade 5 — dehiscence.
On day 9, polypropylene sutures of incision S were removed and biopsies of each wound (groups M and S) were taken. A 1 × 2 cm wedge biopsy specimen, centered in the ventral midline, that included suture tracts, was obtained from the middle of each wound. Suture tracts were created following each suture passage through the dermis. A 0.3 × 2 cm strip of tissue was sectioned from the sample for tensile strength measurements and the rest of the sample was placed in buffered formalin. Specimens for tensile strength determination were wrapped in saline-soaked sponges and placed in ice; measurements were taken within 2 h of collection. A strain gauge tester (Instron 1122 dynamometer; Instron Corporation, Norwood, Massachusetts, USA) was used at 25°C, with a full-scale load cell of 10 kg and a drop head speed of 5 mm/min. Three measurements were taken for each sample, and the mean value was obtained. The specimen labels were coded and the tensile strength measurements were blindly performed by the same scientist (DB). The 0.7 × 2 cm skin strip of “nontested” tissue was placed in 10% neutral buffered formalin, embedded in paraffin, sectioned at 5 to 6 μm and stained with hematoxylin-eosin and van-Gieson’s collagen stain. The slides were assessed based on accuracy of wound edge apposition, epithelial bridging and thickness, cellular reaction, wound vascularity, and collagen content. The coded slide labels were evaluated by the same blinded pathologist (NP). This scoring system was adapted from a previously published protocol (12).
Data were presented as mean ± standard deviation (s). The Wilcoxon matched-paired signed-rank test was used for comparing differences between the closure techniques in surgical time and tensile strength. The marginal homogeneity test (exact inference, 2-sided) was used to compare differences between the 2 closure techniques regarding clinical and histological grading. An alpha of 0.05 was selected for all statistical comparisons.
Mean age of the 6 cats was 10.08 ± 4.95 mo (range: 7.5 to 20 mo) and mean weight was 4.3 ± 0.36 kg (range: 3.8 to 4.9 kg). Five of the 6 cats removed the fixation clips, but not the sutures, between days 8 and 9 after surgery. The mean ± s duration [seconds (s)] of surgical procedure of incision M (313.3 ± 23.2 s) was not significantly different (P = 0.2) from that of incision S (283.5 ± 30.75 s) and the mean ± s tensile strength of incision M (7.69 ± 1.75 kg/cm2) was not significantly different (P = 0.6) than that of incision S (7.87 ± 1.38 kg/cm2) (Table 1). There was no significant difference in gross evaluation scores between the closure techniques (Table 2). On day 4, incision S (5 cats with grade 1) tended to have a milder swelling (P = 0.13) than that of incision M (5 cats with grade 2). All animals were re-evaluated 1 mo after surgery and found to be clinically well. All incisions were inspected and no complications were identified. No significant differences were recorded between the 2 closure techniques based on histology (Table 3).
Intradermal skin closure may be achieved using either a continuous absorbable or a nonabsorbable monofilament suture material (1,13). Monofilament sutures may create less tissue drag and induce less inflammation than multifilament sutures (1,14). Polypropylene is a non-absorbable material with minimal tissue drag and moderate strength that was favorably compared to absorbable monofilament materials for intradermal closures in human surgery (4–7). Permanent polypropylene intradermal closure in dogs used for wounds under significant tension has been also reported to aid in prevention of scar widening (15). The surgical time required for closure of incision S was less than that for incision M but the difference was not significant; the difference probably reflects the lack of knots during polypropylene placement compared to glycolide, -caprolacton, and trimethylene-carbonate placement where there were 2 buried knots.
Incisional swelling tended to be longer lasting and more prevalent in incision M than incision S. On day 2, swelling of incision M was observed in all cats and swelling subsided in 3 cats on day 7. In contrast, 3 cats showed swelling of incision S on day 2, and swelling subsided in all cats on day 7. Incisional postoperative swelling is commonly encountered in cats especially those with a thin skin and subcutaneous tissue (8,11,16). There is no agreement, however, on the necessity of closing subcutaneous tissue in cats. Some authors found that seroma formation may be less likely if subcutaneous tissue is closed with sutures (11), whereas others believe that swelling is less when there is no closure of subcutaneous tissue (16). Differences between the 2 closure techniques may relate to the type of suture material used in the present study or to the anatomic site. Results of this study compare favorably with those of a study on closure of skin lacerations in experimental pigs (17). In this study, histologic examination on day 9 showed that closure with glycolide, -caprolacton and trimethylene-carbonate suture tended to cause wound edge misalignment and incomplete epithelialization compared with closure with polypropylene suture. Cellular reaction was moderate to severe in most incisions, regardless of the closure technique. This might be due to the trauma produced by placement of the needle and reaction to the suture material.
In conclusion, intradermal closure in cats using polypropylene achieves comparable epithelialization to that using glycolide, -caprolacton, and trimethylene-carbonate. Disadvantages of polypropylene sutures were the premature removal of the attachment clips by the cats and the need for suture removal. CVJ
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