An improved method of in vivo wound disruption and measurement

Outcome Measurements in Wound Healing Are Not Inclusive: A Way Forward

Standardized outcome measurement in wound healing has been an elusive goal. Whilst research into wound healing science and technology continues to progress rapidly, the lack of a uniform outcome assessment is making comparative analysis of results difficult. This paper seeks to outline the reported clinical, physiological, and histological outcomes that have been utilized in the literature. A minimal data set base for wound outcome evaluation is also established to be validated by future multivariate analysis of patient data.

Clinical applications of surgical adhesives and sealants

In the United States and Europe, the number of topical adhesives, surgical sealants, and hemostats approved for use in the surgical setting is ever expanding although no single device fills all medical and surgical needs to replace sutures. As more surgical procedures are performed through laparoscopic and robotic approaches, these devices are becoming more important, and current research is focused on solving the limitations of conventional wound treatments. This review article discusses clinical applications of various biologically derived and synthetic products that are currently available to surgeons and those that are in development.

Morphine enhances tissue content of collagen and increases wound tensile strength

PURPOSE

Morphine is a commonly prescribed analgesic for wound pain. Previous studies have shown that morphine enhances accumulation of collagen in cultured fibroblasts. Because fibroblasts are important for the remodeling of connective tissue in incisional wound, this study investigates the biological effects of morphine on cutaneous collagen content and wound tensile strength.

METHODS

A full-thickness incisional wound (2 cm in length) was created on the dorsum of mice followed by treatment with placebo or morphine (5 and 20 mg/kg/day, i.p.). Fourteen days later, tensile strength of the healed incisional wound was measured using a tensiometer. Protein expression of transforming growth factor (TGF)-beta1 and matrix metalloproteinases (MMP)-2 in the incisional wound tissue was analyzed. Degree of tissue remodeling and levels of collagen were determined by histological examination and a dye-binding collagen assay, respectively.

RESULTS

Morphine enhanced the breaking strength of incisional wound 14 days after treatment (92 +/- 10, 102 +/- 10 and 134 +/- 12 mg for control, morphine 5 mg/kg/day and morphine 20 mg/kg/day, respectively; P = 0.03, n = 6-7). Protein expression of TGF-beta1 and MMP-2 was significantly enhanced in mice treated with morphine. Histological examination of the wound tissue showed evidence of increased thickness of the cutaneous fibrous layer and deposition of collagen in the high-dose morphine treatment group. Collagen assays also demonstrated that tissue concentrations of collagen were significantly increased in the wound tissue of morphine-treated animals on day 2 of drug treatment.

CONCLUSION

The present study demonstrates that systemic administration of morphine enhances tissue collagen deposition in the cutaneous tissue, thereby increasing the tensile strength of the incisional wound.

In vivo study of wound bursting strength and compliance of topical skin adhesives

OBJECTIVES

Over the past decade, the use of topical skin adhesives (TSA) for wound closure has increased. Among TSA characteristics, strength and flexibility are most important. Prior studies have compared the wound bursting strengths (WBSs) of the cyanoacrylates immediately after wound closure. In this study the authors compared the WBS and flexibility of multiple TSAs immediately and up to 2 days after closure.

METHODS

This was a controlled animal experiment. Two-centimeter incisions were created on both sides of 210 Sprague-Dawley rats and randomly closed with one of five commercially available TSAs (Dermabond [D], Indermil [I], Histoacryl [H], Liquiband [L], or GluStitch [G]). WBS and TSA flexibility were measured using the BTC-2000 device immediately after closure and at 1 and 2 days after closure. WBS and TSA flexibility were compared across groups with analysis of variance (ANOVA).

RESULTS

Wound bursting strengths were higher (p < 0.05) at 0, 1, and 2 days for D (274, 388, 232 mm Hg) than for all other TSAs (I 182, 225, and 107; H 189, 214, and 69; L 146, 118, and 75; or G 161, 150, and 73). TSA flexibility was also greater (p < 0.05) at 0, 1, and 2 days for D (36, 27, and 29 mm Hg/mm) than for all other TSAs (I 18, 14, and 12; H 18, 13, and 15; L 19, 14, and 12; G 26, 23, and 18).

CONCLUSIONS

The octyl-cyanoacrylate-based adhesive is significantly stronger and more flexible than all the butyl-cyanoacrylate-based adhesives at 0, 1 and 2 days after closure.

Considerations for selecting the correct animal model for dermal wound-healing studies

An array of animal models has been described to elucidate wound-healing processes and access the impact of various therapies on healing. However, which model to use for different applications may not be immediately apparent. This article will highlight less frequently used animal models so as to illustrate their utility and increase their use. Selection of an animal model should include consideration of inter-species anatomical and physiological attributes that may confound data interpretation, differences in how different types of wounds heal, and sample size and analytical techniques to be applied. Importantly, the use of human beings should be considered, as techniques have been developed that allow for histological, biochemical and molecular analyses of healing parameters on a scale that could be used in humans.

Has packing sinus wounds become a ritualistic practice?

Wound healing is both a science and an art, and modern advances in wound management are ensuring that advanced clinicians use both clinical knowledge and experience when deciding on wound dressings and therapies. When there is a lack of evidence, then selection of dressings or therapies becomes extremely difficult and inappropriate treatment can occur. This is generally the situation with sinus wounds. There is very little evidence available to help decide on suitable dressings for these intractable wounds. The use of high frequency ultrasound (HFU) can help to guide practice on whether or not to pack sinus wounds. This article will explore the potential of ultrasound use by describing a case study of a patient with a sinus wound where HFU was used to examine the sinus and inform the practitioners on the appropriate choice of wound dressing.

Intraoperative handling and wound healing: controlled clinical trial comparing coated VICRYL plus antibacterial suture (coated polyglactin 910 suture with triclosan) with coated VICRYL suture (coated polyglactin 910 suture)

BACKGROUND

Coated polyglactin 910 suture with triclosan was developed recently in order to imbue the parent suture, coated polyglactin 910, with antibacterial activity against the most common organisms that cause surgical site infections (SSI). Because such alterations could alter the physical properties of the suture, this study sought to compare the intraoperative handling and wound healing characteristics of coated polyglactin 910 suture with triclosan and traditional coated polyglactin 910 suture in pediatric patients undergoing various general surgical procedures.

METHODS

This was a prospective, randomized, controlled, open-label, comparative, single-center study. Pediatric patients (age 1-18 years) undergoing various surgical procedures were randomized in a 2:1 ratio to treatment with either coated polyglactin 910 suture with triclosan or coated polyglactin 910 suture. The primary endpoint was the surgeon's assessment of the overall intraoperative handling of coated polyglactin 910 suture with triclosan and traditional coated polyglactin 910 suture without triclosan. The secondary endpoints included specific intraoperative suture handling measures and wound healing assessments. The suture handling measures were (1) ease of passage through tissue; (2) first-throw knot holding; (3) knot tie-down smoothness; (4) knot security; (5) surgical handling; (6) surgical hand; (7) memory; and (8) suture fraying. Assessment of wound healing included the following: Healing progress, infection, edema, erythema, skin temperature, seroma, suture sinus, and pain. Adverse events were recorded.

RESULTS

Scores for intraoperative handling were favorable and not significantly different for both sutures, although coated polyglactin 910 suture with triclosan received more "excellent" scores (71% vs. 59%). Wound healing characteristics were comparable for both sutures except for pain on postoperative day 1. Significantly fewer patients treated with polyglactin 910 suture with triclosan reported pain on day 1 than patients who received the other suture (68% vs. 89%, p = 0.01). The overall incidence of adverse events was 18%; none was devicerelated.

CONCLUSIONS

Coated polyglactin 910 suture with triclosan performed as well or better than traditional coated polyglactin 910 suture in pediatric patients undergoing general surgical procedures. The incidence of postoperative pain was significantly less in patients treated with coated polyglactin 910 suture with triclosan than the traditional suture. We speculate that polyglactin 910 suture with triclosan, by inhibiting bacterial colonization of the suture, reduced pain that can be an indicator of "subclinical" infection. Coated polyglactin 910 suture with triclosan may be a useful alternative in patients at increased risk of developing SSI.

Quantitative and reproducible murine model of excisional wound healing

The goal of animal wound healing models is to replicate human physiology and predict therapeutic outcomes. There is currently no model of wound healing in rodents that closely parallels human wound healing. Rodents are attractive candidates for wound healing studies because of their availability, low cost, and ease of handling. However, rodent models have been criticized because the major mechanism of wound closure is contraction, whereas in humans reepithelialization and granulation tissue formation are the major mechanisms involved. This article describes a novel model of wound healing in mice utilizing wound splinting that is accurate, reproducible, minimizes wound contraction, and allows wound healing to occur through the processes of granulation and reepithelialization. Our results show that splinted wounds have an increased amount of granulation tissue deposition as compared to controls, but the rate of reepithelialization is not affected. Thus, this model eliminates wound contraction and allows rodents' wounds to heal by epithelialization and granulation tissue formation. Given these analogies to human wound healing, we believe that this technique is a useful model for the study of wound healing mechanisms and for the evaluation of new therapeutic modalities.

A 28-day study of the effect of Coated VICRYL* Plus Antibacterial Suture (coated polyglactin 910 suture with triclosan) on wound healing in guinea pig linear incisional skin wounds

BACKGROUND

This study evaluated the effect of coated polyglactin 910 suture with triclosan on tissue response and wound healing over a 28-day period on full-thickness linear wounds in the hairless guinea pig model.

METHODS

In situ wound strength was assessed, and histopathologic effects on tissue response and wound healing were evaluated. Four (1.9 cm) full-thickness incisional wounds were created on the dorsolateral region (two left and two right, approximately 3 cm apart) in 40 Hartley male hairless guinea pigs (400-500 g). A 1.9-cm segment of suture material was implanted "length-wise" into the incision and the sites closed with simple interrupted closure with 3-0 nylon sutures. The test material was 2-0 coated polyglactin 910 suture with triclosan and the control material was 2-0 Coated VICRYL* Suture (coated polyglactin 910 suture). On days 3, 7, 14, and 28 postimplantation (n = 10/time interval), body weights were recorded, tissue specimens harvested, and bursting strength testing performed.

RESULTS

There was no significant difference (P > 0.05) in bursting strength between the study groups for any of the time intervals studied. The bursting strengths (mm Hg) for the sutures with triclosan were 95.8 (day 3), 268.8 (day 7), 542.6 (day 14), and 633.8 (day 28). Both materials demonstrated comparable tissue response to implantation, and there were no significant differences (P > 0.05) observed in wound healing based on cellular response and collagen formation and orientation.

CONCLUSION

Based on the in vivo biomechanical testing and histological results, no evidence of impedance to wound healing was detected.

Non-invasive measurement of biomechanical skin properties in systemic sclerosis

OBJECTIVE

To evaluate biomechanical properties of skin in patients with systemic sclerosis (SSc) using the BTC-2000 suction device.

METHODS

Twenty five patients with limited cutaneous SSc (lcSSc), 20 patients with diffuse disease (dcSSc), and 25 age matched healthy controls were evaluated. Viscoelastic deformation (VED, mm), elastic deformation (ED, mm), ultimate deformation (UD, mm), and pressure-deformation ratio (PDR, mm Hg/mm) were measured on the dorsal surface of the forearm, shoulder, and above the trapezius muscle on the back.

RESULTS

Indices of skin extensibility (VED, ED, UD) were reduced and resistance to stress (PDR) increased in patients with dcSSc compared with healthy controls, or patients with lcSSc, at all three sites (p<0.001). At all sites, and overall, UD, ED, and VED were lower and PDR was higher at skin score above grade 2, compared with clinically normal skin. For both lcSSc and dcSSc biomechanical differences from controls were found even at sites of clinically normal skin.

CONCLUSION

BTC-2000 is a sensitive tool for clinical evaluation of skin involvement in SSc and may be a valuable adjunct to skin sclerosis score in disease monitoring.

Use of the wound healing trajectory as an outcome determinant for acute wound healing

Accurate and clinically practical methods for measuring the progress of acute wound healing is necessary before interventions designed to optimize and even accelerate acute wound healing can be applied. Complete wound closure rates and operative wound closure severity are irrelevant to most acute wounds since most are closed at the time of primary tissue repair and remain closed throughout healing. Analogous to chronic wound closure, the rate of increase of incision tensile strength progressively decreases as time passes and 100% unwounded tissue strength is never achieved making the endpoint definition of "healed" vague. Conceptualizing acute wound healing in terms of its design elements with reintegration into a final outcome lends itself to the description of acute wound healing as a mathematical trajectory. Frequently such an equation is a rate expressing the change in an acute healing parameter, most often tensile strength, over time. Such an approach also normalizes misinterpretations in analysis or errors in theory developed by measuring healing parameters at fixed points in time. Distributions of fractional strength gain times (e.g., 85% normal strength) can be determined using statistical methodology similar that used for failure time of survival analysis. Preclinical studies show that acute wound healing trajectories can be shifted to the left from a "normal" or "impaired" curve to an accelerated or more "ideal" curve. A useful method for measuring acute wound healing outcomes is therefore required before the basic science of acute wound healing is inevitably applied to the problem of acute surgical wounds.

Models for use in wound healing research: a survey focusing on in vitro and in vivo adult soft tissue

Many different factors must be considered before selecting a wound healing model to use for a specific study. A wide variety of models have been developed that examine different aspects of the repair response, both in vitro and in vivo. In this review article, we focus on those systems that are most widely used for studies on adult soft tissue healing. Advantages and disadvantages of each are discussed, along with relevant background information to help guide decision-making.