Special Topic The Influence Manufacturers Have on Negative-Pressure Wound Therapy Research Nicolas Kairinos, M.Med., F.C.Plast.Surg., Ph.D. Kamlen Pillay, M.R.C.S. Michael Solomons, F.C.S. Donald A. Hudson, M.Med., F.C.S., F.R.C.S. Delawir Kahn, M.Med., M.Sc., F.C.S. Cape Town, South Africa
Background: Studies investigating the effects of negative-pressure wound therapy using the Chariker-Jeter system (gauze-based interface) and the vacuum-assisted closure system often have outcomes that favor one particular system. This study attempts to examine whether manufacturer involvement could be related to the outcomes of these scientific studies. Methods: A literature review was undertaken to identify a cohort of studies that compared these two forms of negative-pressure wound therapy. Clinical outcomes studies, basic research studies, and published conference abstracts were included. All the articles’ abstracts and conclusions were given to five surgeons, who were blinded to the titles and authors. They were individually asked to record what they would consider to be the take-home message of each article (in terms of which system is superior). After categorizing each study according to the system that it appears to favor, the level of manufacturer involvement in each study was evaluated. The relationship between the outcome of a study and the level of manufacturer involvement in that study was then investigated. Results: Of the total of 24 studies found to match the inclusion criteria, 22 were considered to favor a particular system (the other two were categorized as impartial). Of the 24 studies, 19 had some form of manufacturer involvement. Of the 19 that had some form of manufacturer involvement, 18 had outcomes that were deemed beneficial to the involved manufacturer, whereas one was deemed to have an impartial outcome. Conclusions: This study suggests that manufacturer involvement in these studies (regardless of level) correlates with the outcomes being beneficial to the involved manufacturer in almost all cases. Potential reasons for this and the implications thereof are discussed. (Plast. Reconstr. Surg. 133: 1178, 2014.)
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egative-pressure wound therapy has been widely adopted by numerous surgical disciplines. However, the mechanism of action has not been fully elucidated. Numerous theories have been proposed,1–11 many of which are supported by peer-reviewed publications. However, there is conflicting evidence among these studies and, as such, researchers continue to try and understand the mechanism of this therapy. Although a form of negative-pressure wound therapy was already described by Svedman in From the Departments of Plastic Surgery and Surgery, and the Martin Singer Hand Unit, Department of O rthopaedic Surgery, University of Cape Town and Groote Schuur Hospital. Received for publication May 22, 2013; accepted October 30, 2013. Presented at the Association of Plastic, Reconstructive and Aesthetic Surgeons of Southern Africa Meeting, in Stellenbosch, South Africa, October 14 through 17, 2011. Copyright © 2014 by the American Society of Plastic Surgeons DOI: 10.1097/PRS.0000000000000130
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197912 and in the Russian literature in the early 1980s,13–24 the two most common techniques used today are those described by Morykwas et al.,1 Argenta and Morykwas,2 and Chariker et al.25 The intellectual property of the technique and patented system described by Morykwas and Argenta et al. in 1997 was assigned to Kinetic Concepts, Inc. (San Antonio, Texas) and is known as vacuum-assisted closure (V.A.C.). This is a foam-based negative-pressure wound therapy device, using the patented Therapy Regulated Accurate Care (T.R.A.C.) drainage system to supply the generally recommended suction pressure of −125 mmHg. The technique of Chariker et al., initially described in 1989, is commonly referred to as the Chariker-Jeter technique and entails the use of gauze-based negative-pressure wound therapy. Disclosure: The authors have no financial interest to declare in relation to the content of this article.
www.PRSJournal.com
Volume 133, Number 5 • Manufacturer Involvement in Studies Suction is supplied by a perforated drainage tube, and the pressures used are generally lower than the pressures recommended by Kinetic Concepts (−75 to −80 mmHg). The financial success achieved by the commercialization of negative-pressure wound therapy in the form of the patented vacuum-assisted closure device has inspired many other manufacturers to develop their own form of negative-pressure wound therapy. Because of Kinetic Concepts actively protecting its intellectual property, with exorbitant litigation battles still continuing at the time of writing, practically all other manufacturers have adopted the Chariker-Jeter technique. Originally, most studies on negative-pressure wound therapy had been conducted using the vacuum-assisted closure device. The growing number of manufacturers using the CharikerJeter technique has resulted in an increasing number of studies on this method in an attempt to clarify which system is the most successful. Some directly compare these two forms of negative-pressure wound therapy, whereas others indirectly “compare” them by testing the outcomes of one type and comparing them to known outcomes of the other. As with many other studies involving negative-pressure wound therapy, the outcomes of these comparative studies conflict with one another, despite rigorous scientific methodology and peer review. Anecdotally, it appeared that many of the studies that found better outcomes with a particular system were associated in some way with the manufacturer of such a system. Similarly, the discussions of these studies often appeared to promote mechanisms of action of negative-pressure wound therapy that would favor that particular manufacturer’s type of system (e.g., foam or gauze). The degree of association varied, however, from no association at all, to studies that were conducted by the manufacturers themselves. A scientific model was sought to objectively quantify whether there was a statistically significant relationship between these studies’ outcomes and the level of involvement of manufacturers in the research. The design of this study required a
somewhat unorthodox methodology because of the nature of what needed to be determined.
MATERIALS AND METHODS A literature review was undertaken using PubMed and Google Scholar to identify a representative cohort of studies that directly compared these two forms of negative-pressure wound therapy. An additional review was undertaken to include studies that did not directly compare products but had outcome measures regarding one type of dressing, which assisted the assessment of the two systems. In the latter studies, if the authors did not mention and compare components of the other available system (or their components), they were excluded from this study, as they were not seen as comparative. Clinical outcomes studies, basic research studies, and published conference abstracts were included. A negative-pressure wound therapy system comprises individual components, and each of these could be compared or studied separately, as each could affect the success of the system. Therefore, over and above the comparison of the composite vacuum-assisted closure and Chariker-Jeter systems, studies comparing the outcomes of the following individual components of a negative-pressure wound therapy system were also included: lower suction pressures (Chariker-Jeter technique) versus the higher ones typically used with vacuumassisted closure; foam (vacuum-assisted closure) versus gauze (Chariker-Jeter technique); and single-lumen (vacuum-assisted closure) versus perforated drainage tubes (Chariker-Jeter technique). Therefore, as some studies tested only individual components and others tested the entire system, instead of referring to vacuum-assisted closure or Chariker-Jeter systems, we assigned the products being compared to either group A (any composite vacuum-assisted closure system or individual components thereof) or group B (any composite Chariker-Jeter technique or individual components thereof) (Table 1). Any study that compared a group A component to its group B counterpart was included in this analysis. Although group A
Table 1. The Two Groups, A and B, Categorized by Specific Components Known to Be Parts of These Systems Composite System or Components Thereof Composite system Interface dressing Suction drainage system Recommended suction pressure
Group A
Group B
V.A.C. Foam (PU or PVA) Single lumen (T.R.A.C. pad) −125 mmHg
Chariker-Jeter Gauze Perforated drainage tube (e.g., Jackson-Pratt drain) −75 to −80 mmHg
PU, polyurethane; PVA, polyvinyl alcohol; T.R.A.C., Therapy Regulated Accurate Care.
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Plastic and Reconstructive Surgery • May 2014 refers to one manufacturer (Kinetic Concepts, Inc.) and group B to multiple, “group B manufacturers” will be referred to in the singular form during comparisons (i.e., group B manufacturer). Based on their findings and conclusions, studies were then categorized into two groups, namely, studies with outcomes beneficial to group A manufacturers or those with outcomes beneficial to group B manufacturers. The current market leaders are Kinetic Concepts (group A manufacturer) with the vacuum-assisted closure device, which is still considered the accepted standard in negative-pressure wound therapy, albeit more expensive than the group B devices.26 Therefore, studies that found the group B components to be as good as or superior to the current accepted standard (group A components) were considered to have outcomes beneficial to group B manufacturers. If the study concluded that group A components were superior, they were considered to have outcomes beneficial to group A manufacturers. Although most studies were quite clear in terms of which system was “as good as” or “superior” to the other, there were some that were less clear. This was found where studies tested multiple components or had various outcome measures and found some components superior for one outcome but not necessarily for others. A study may have also found that one of the components was better but that the others were not. However, most tended to leave the reader with an impression of which system had better overall benefits. For this reason, and to ensure impartial categorization, all of the articles’ abstracts and conclusions were given to five surgeons. They were individually asked to record what they would consider to be the take-home message of each article (in terms of which system is superior). None of the surgeons had any conflict of interest with either of the two systems. There was no communication between the surgeons during this process. They were blinded to the authors of the study and any manufacturer involvement in the
article. The articles were presented in a randomized manner. This was done by placing the titles of the studies on lots, shuffling these in a closed box, and randomly selecting a title before the study was presented to the surgeon. If there was 80 percent concordance among the surgeons’ decisions (four of five), the article was assigned to one of the following categories: (1) outcomes beneficial to group A manufacturers, (2) outcomes beneficial to group B manufacturers, or (3) impartial. Once assigned to one of the three categories, the individual studies were assessed and graded according to the level of manufacturer involvement in the study (Table 2). Only one of the specified criteria was necessary to grade a manufacturer’s involvement to a particular level. Although an attempt was also made to stratify each study according to the levels of evidence, this was abandoned because only four of the 24 studies were conducted on humans. The rest were either animal or laboratory experiments. It was planned that an analysis would be performed to ascertain whether there was a correlation between the category to which a study belonged (outcomes beneficial to group A manufacturers or outcomes beneficial to group B manufacturers) and the level of manufacturer involvement. However, a formal statistical analysis was deemed not necessary for this aspect of the study after evaluating the outcomes (see later under Results). The Mann-Whitney U test was used, however, to compare the levels of involvement of group A and group B manufacturers (p
Background: Studies investigating the effects of negative-pressure wound therapy using the Chariker-Jeter system (gauze-based interface) and the vacuum-assisted closure system often have outcomes that favor one particular system. This study attempts to examine whether manufacturer involvement could be related to the outcomes of these scientific studies. Methods: A literature review was undertaken to identify a cohort of studies that compared these two forms of negative-pressure wound therapy. Clinical outcomes studies, basic research studies, and published conference abstracts were included. All the articles’ abstracts and conclusions were given to five surgeons, who were blinded to the titles and authors. They were individually asked to record what they would consider to be the take-home message of each article (in terms of which system is superior). After categorizing each study according to the system that it appears to favor, the level of manufacturer involvement in each study was evaluated. The relationship between the outcome of a study and the level of manufacturer involvement in that study was then investigated. Results: Of the total of 24 studies found to match the inclusion criteria, 22 were considered to favor a particular system (the other two were categorized as impartial). Of the 24 studies, 19 had some form of manufacturer involvement. Of the 19 that had some form of manufacturer involvement, 18 had outcomes that were deemed beneficial to the involved manufacturer, whereas one was deemed to have an impartial outcome. Conclusions: This study suggests that manufacturer involvement in these studies (regardless of level) correlates with the outcomes being beneficial to the involved manufacturer in almost all cases. Potential reasons for this and the implications thereof are discussed. (Plast. Reconstr. Surg. 133: 1178, 2014.)
N
egative-pressure wound therapy has been widely adopted by numerous surgical disciplines. However, the mechanism of action has not been fully elucidated. Numerous theories have been proposed,1–11 many of which are supported by peer-reviewed publications. However, there is conflicting evidence among these studies and, as such, researchers continue to try and understand the mechanism of this therapy. Although a form of negative-pressure wound therapy was already described by Svedman in From the Departments of Plastic Surgery and Surgery, and the Martin Singer Hand Unit, Department of O rthopaedic Surgery, University of Cape Town and Groote Schuur Hospital. Received for publication May 22, 2013; accepted October 30, 2013. Presented at the Association of Plastic, Reconstructive and Aesthetic Surgeons of Southern Africa Meeting, in Stellenbosch, South Africa, October 14 through 17, 2011. Copyright © 2014 by the American Society of Plastic Surgeons DOI: 10.1097/PRS.0000000000000130
1178
197912 and in the Russian literature in the early 1980s,13–24 the two most common techniques used today are those described by Morykwas et al.,1 Argenta and Morykwas,2 and Chariker et al.25 The intellectual property of the technique and patented system described by Morykwas and Argenta et al. in 1997 was assigned to Kinetic Concepts, Inc. (San Antonio, Texas) and is known as vacuum-assisted closure (V.A.C.). This is a foam-based negative-pressure wound therapy device, using the patented Therapy Regulated Accurate Care (T.R.A.C.) drainage system to supply the generally recommended suction pressure of −125 mmHg. The technique of Chariker et al., initially described in 1989, is commonly referred to as the Chariker-Jeter technique and entails the use of gauze-based negative-pressure wound therapy. Disclosure: The authors have no financial interest to declare in relation to the content of this article.
www.PRSJournal.com
Volume 133, Number 5 • Manufacturer Involvement in Studies Suction is supplied by a perforated drainage tube, and the pressures used are generally lower than the pressures recommended by Kinetic Concepts (−75 to −80 mmHg). The financial success achieved by the commercialization of negative-pressure wound therapy in the form of the patented vacuum-assisted closure device has inspired many other manufacturers to develop their own form of negative-pressure wound therapy. Because of Kinetic Concepts actively protecting its intellectual property, with exorbitant litigation battles still continuing at the time of writing, practically all other manufacturers have adopted the Chariker-Jeter technique. Originally, most studies on negative-pressure wound therapy had been conducted using the vacuum-assisted closure device. The growing number of manufacturers using the CharikerJeter technique has resulted in an increasing number of studies on this method in an attempt to clarify which system is the most successful. Some directly compare these two forms of negative-pressure wound therapy, whereas others indirectly “compare” them by testing the outcomes of one type and comparing them to known outcomes of the other. As with many other studies involving negative-pressure wound therapy, the outcomes of these comparative studies conflict with one another, despite rigorous scientific methodology and peer review. Anecdotally, it appeared that many of the studies that found better outcomes with a particular system were associated in some way with the manufacturer of such a system. Similarly, the discussions of these studies often appeared to promote mechanisms of action of negative-pressure wound therapy that would favor that particular manufacturer’s type of system (e.g., foam or gauze). The degree of association varied, however, from no association at all, to studies that were conducted by the manufacturers themselves. A scientific model was sought to objectively quantify whether there was a statistically significant relationship between these studies’ outcomes and the level of involvement of manufacturers in the research. The design of this study required a
somewhat unorthodox methodology because of the nature of what needed to be determined.
MATERIALS AND METHODS A literature review was undertaken using PubMed and Google Scholar to identify a representative cohort of studies that directly compared these two forms of negative-pressure wound therapy. An additional review was undertaken to include studies that did not directly compare products but had outcome measures regarding one type of dressing, which assisted the assessment of the two systems. In the latter studies, if the authors did not mention and compare components of the other available system (or their components), they were excluded from this study, as they were not seen as comparative. Clinical outcomes studies, basic research studies, and published conference abstracts were included. A negative-pressure wound therapy system comprises individual components, and each of these could be compared or studied separately, as each could affect the success of the system. Therefore, over and above the comparison of the composite vacuum-assisted closure and Chariker-Jeter systems, studies comparing the outcomes of the following individual components of a negative-pressure wound therapy system were also included: lower suction pressures (Chariker-Jeter technique) versus the higher ones typically used with vacuumassisted closure; foam (vacuum-assisted closure) versus gauze (Chariker-Jeter technique); and single-lumen (vacuum-assisted closure) versus perforated drainage tubes (Chariker-Jeter technique). Therefore, as some studies tested only individual components and others tested the entire system, instead of referring to vacuum-assisted closure or Chariker-Jeter systems, we assigned the products being compared to either group A (any composite vacuum-assisted closure system or individual components thereof) or group B (any composite Chariker-Jeter technique or individual components thereof) (Table 1). Any study that compared a group A component to its group B counterpart was included in this analysis. Although group A
Table 1. The Two Groups, A and B, Categorized by Specific Components Known to Be Parts of These Systems Composite System or Components Thereof Composite system Interface dressing Suction drainage system Recommended suction pressure
Group A
Group B
V.A.C. Foam (PU or PVA) Single lumen (T.R.A.C. pad) −125 mmHg
Chariker-Jeter Gauze Perforated drainage tube (e.g., Jackson-Pratt drain) −75 to −80 mmHg
PU, polyurethane; PVA, polyvinyl alcohol; T.R.A.C., Therapy Regulated Accurate Care.
1179
Plastic and Reconstructive Surgery • May 2014 refers to one manufacturer (Kinetic Concepts, Inc.) and group B to multiple, “group B manufacturers” will be referred to in the singular form during comparisons (i.e., group B manufacturer). Based on their findings and conclusions, studies were then categorized into two groups, namely, studies with outcomes beneficial to group A manufacturers or those with outcomes beneficial to group B manufacturers. The current market leaders are Kinetic Concepts (group A manufacturer) with the vacuum-assisted closure device, which is still considered the accepted standard in negative-pressure wound therapy, albeit more expensive than the group B devices.26 Therefore, studies that found the group B components to be as good as or superior to the current accepted standard (group A components) were considered to have outcomes beneficial to group B manufacturers. If the study concluded that group A components were superior, they were considered to have outcomes beneficial to group A manufacturers. Although most studies were quite clear in terms of which system was “as good as” or “superior” to the other, there were some that were less clear. This was found where studies tested multiple components or had various outcome measures and found some components superior for one outcome but not necessarily for others. A study may have also found that one of the components was better but that the others were not. However, most tended to leave the reader with an impression of which system had better overall benefits. For this reason, and to ensure impartial categorization, all of the articles’ abstracts and conclusions were given to five surgeons. They were individually asked to record what they would consider to be the take-home message of each article (in terms of which system is superior). None of the surgeons had any conflict of interest with either of the two systems. There was no communication between the surgeons during this process. They were blinded to the authors of the study and any manufacturer involvement in the
article. The articles were presented in a randomized manner. This was done by placing the titles of the studies on lots, shuffling these in a closed box, and randomly selecting a title before the study was presented to the surgeon. If there was 80 percent concordance among the surgeons’ decisions (four of five), the article was assigned to one of the following categories: (1) outcomes beneficial to group A manufacturers, (2) outcomes beneficial to group B manufacturers, or (3) impartial. Once assigned to one of the three categories, the individual studies were assessed and graded according to the level of manufacturer involvement in the study (Table 2). Only one of the specified criteria was necessary to grade a manufacturer’s involvement to a particular level. Although an attempt was also made to stratify each study according to the levels of evidence, this was abandoned because only four of the 24 studies were conducted on humans. The rest were either animal or laboratory experiments. It was planned that an analysis would be performed to ascertain whether there was a correlation between the category to which a study belonged (outcomes beneficial to group A manufacturers or outcomes beneficial to group B manufacturers) and the level of manufacturer involvement. However, a formal statistical analysis was deemed not necessary for this aspect of the study after evaluating the outcomes (see later under Results). The Mann-Whitney U test was used, however, to compare the levels of involvement of group A and group B manufacturers (p
