The Evidence for Staple Line Buttress Material

Ariel U. Spencer, MD; Thomas H. Magnuson, MD, FACS; Hien Nguyen, MD; Kimberley E. Steele, MD, FACS; Anne O. Lidor, MD, FACS; and
Michael A. Schweitzer, MD, FACS.

From The Johns Hopkins Medical Institutions, Baltimore, Maryland

Introduction
Staple line buttress material—either absorbable or permanent—is widely used in bariatric surgery. While many surgeons have anecdotal experience with a particular material, this review will examine the data currently available to support the use of buttress material, the indications for its use, and possible advantages of specific types of material, based on current human and animal studies.

Most bariatric surgical procedures—with the exception of adjustable gastric banding—require the creation of staple lines along the margins of gastric pouch, gastric remnant, or as a component of the anastomoses between hollow viscera. While there are a large number of potential complications from bariatric surgery, one of the most clinically significant complications is leakage of enteric contents along either a marginal staple line or an anastomotic staple line. 

The incidence of leaks associated with laparoscopic Roux-en-Y gastric bypass ranges from 0% to 6% [1–3].  Not all leaks are clinically significant, but those that are significant can result in death or prolonged morbidity. Patients may rapidly deteriorate with tachycardia, peritonitis, sepsis, and death if the leak is not promptly recognized and corrected. In addition to staple line leaks, bleeding from divided edges along staple lines is another source of morbidity and potential mortality.[4] Again, it is the technical integrity of the staple line—especially the appropriate “height” of staples with respect to the thickness of the tissue being stapled—that is a critical factor in prevention of bleeding.

Given the fact that leaks and bleeding are two of the most significant potential complications of bariatric surgery—and also among the most difficult to diagnose and treat in a timely fashion—a number of investigators have tried using buttress material along staple lines to help prevent both leakage and bleeding.

Causes of Staple Line Leaks
Leaks occur primarily as a result of one of three factors: increased intraluminal pressure, tissue ischemia, or technical issues. The effect of increased intraluminal pressure is particularly important in blind loops such as the gastric remnant after a Roux-en-Y gastric bypass. In this case, the stomach has no outlet to decompress itself in the event of an obstruction, which can lead to markedly elevated intragastric pressures. This, in turn, stresses the integrity of the staple lines along the margin of gastric division. This point has clearly been demonstrated in a number of carefully conducted animal studies in which the ability of transgastric staple lines to resist elevated intraluminal pressure (burst pressure) was tested either with or without buttressing material along the staple line. Most of these studies report dramatically improved resistance of staple lines to intraluminal pressure if buttressing material is used.[5–7 ] The reason for the success of buttressing material in this setting is the fact that the material distributes tension over a greater serosal surface area than staples alone. In fact, when buttressing material is used and increased intraluminal pressure is generated experimentally the staple line often remains intact even when sufficient pressure has been generated to cause rupture of the stomach or bowel wall itself.[8] While most of these experimental data support the efficacy of buttressing material to protect against leaks due to increased intraluminal pressures, there are a few experimental studies that have not found a significant improvement in burst pressure when buttress material is used. In a porcine model of sleeve gastrectomy, there was no significant improvement in burst pressure when buttress material was used on the staple lines.[9]
A second cause of staple line leaks is tissue ischemia. If a focal area of stomach or intestinal wall is devascularized, this portion of bowel wall may subsequently necrose and slough away from surrounding tissue, creating a point of enteric leak. This may be one possible mechanism to explain delayed leaks after bariatric surgery, which may occur about one week postoperatively when ischemic tissue would be expected to slough off remaining viable tissue. It is not clear whether staple line buttress material actually provides any benefit in terms of protecting against this type of leak.
Finally, a third major cause of leaks are technical issues. A number of specific technical issues can lead to staple line leakage. These include failure of the stapling device itself (failure of staples to deploy properly) or incorrect choice of stapler for the tissue being divided. Each stapler manufacturer provides specific instructions regarding the thickness of tissue appropriate for each device,[7] but tissue thickness in the clinical setting is highly variable, and the correct choice of staple device is still best determined by a clinician with extensive clinical experience using the device. Individual differences in surgical skill probably explain some of the variability in leak rates between different studies, even when the same staplers and buttress material are used.

The thickness of the buttress material must be taken into account when deploying a stapler.[8–11] For example, a bovine pericardial strip (Peri-Strips Dry, Synovis Surgical Innovations, St. Paul, Minnesota) adds about 0.4mm thickness, but one must take into account twice this amount because two strips are used with each stapling (one on each side). An absorbable synthetic polyglycolide/ trimethylene carbonate buttress material (Seamguard bioabsorbable, W. L. Gore & Associates, Inc., Flagstaff, Arizona) adds a total of 0.5mm thickness (0.25mm for each of the two sides of the buttress material). An absorbable glycolide diaxonone trimethylene carbonate product sold as an integrated product already loaded onto the stapler cartridge (Duet TRS, Covidien, Norwalk, Connecticut) is 0.07mm thickness on each side to add a total of 0.14mm along each staple line. Clearly, the surgeon needs to keep these differences in mind when choosing different materials to buttress staple lines. Trying to staple through material either too thick or too thin can result in a flawed staple line. Attempts to staple through material (tissue plus buttress) exceeding the thickness limit for a particular stapler will risk incomplete formation of staples, or cause injury to the tissue itself. On the other hand, material too thin for a particular stapler can lead to immediate staple line leakage.[5–7]

Apart from technical issues associated with the stapling and buttress material themselves, there are also technical issues related solely to proper surgical technique. For example, failure to close gaps along a divided margin will guarantee a bad outcome. In this case, there may be a direct opening into the lumen at the site of an enterotomy created while performing a stapled anastomosis. Subsequently, if a stapling device is used to close this enterotomy defect, one must carefully inspect the area after deploying the stapler to be sure that no further defect remains. Visual inspection of a staple line after it has been completed is mandatory, in order to look for inadvertent technical errors.

Clinical Evidence for Buttress Material
A prospective nonrandomized study compared the rate of staple line leaks in patients with a mean BMI of 45kg/m2, undergoing Roux-en-Y gastric bypass either with or without bovine pericardial strips to buttress the staple lines.[12] As in several other studies, there were fewer leaks in the group with buttress material, compared to the nonbuttressed group.[10,13–15] This has been shown both with absorbable and nonabsorbable buttress materials.[16] However, not all studies reached the same conclusion. In contrast to some of the studies in patients undergoing gastric bypass, a recent review of leak rates after sleeve gastrectomy found no benefit to buttress material.[17] The first international consensus summit for sleeve gastrectomy also found wide variability in current surgical practice, with only some surgeons routinely using buttress material during that operation.[18] As a result, the data are somewhat controversial as to the benefit of buttress material to reduce gastric staple line leaks.

Part of this controversy may be due to the variety of materials that have been used. As mentioned earlier, several products have gained a significant share of the market in recent years. Permanent material, such as glutaraldehyde-preserved bovine pericardium (Peri-Strips Dry, Synovis Surgical Innovations, St. Paul, Minnesota) has had case reports of extrusion into the lumen of the bowel.[19, 20] A newer product from the same company is nonpermanent bovine pericardium (Peri-Strips Dry Veritas, Synovis). Synthetic materials have also been produced in both permanent (expanded PTFE, Seamguard, W.L. Gore & Associates, Flagstaff, Arizona) and completely absorbable varieties (polyglycolide/trimethylene carbonate, Seamguard bioabsorbable, W.L. Gore & Associates). Another biologic absorbable product is made of porcine small bowel submucosa (Surgisis, Cook Biotech Inc., West Lafayette, Indiana). And a more recently available product is made of glycolide diaxonone trimethylene carbonate, which is absorbable (Duet TRS, Covidien, Norwalk, CT). Given the variety of available products, controversy in the literature is not surprising; however, recent literature reviews tend to support the view that overall, buttress material on gastric staple lines does, in fact, reduce the incidence of leaks.[16]

Very few direct comparisons of one material to another have been reported. In one available (nonrandomized) study, bovine pericardial strips were compared with polyglycolide/trimethylene carbonate buttress material. This study found a significantly greater incidence of leaks in the latter group; but importantly, these authors used the same stapler (3.5mm staple height) in both groups.[21] Because the polyglycolide/trimethylene carbonate product is significantly thinner than the bovine pericardial product, the increased leak rate may be attributable to their use of the same stapler with buttress materials of significantly different thicknesses.[21]

This point illustrates the attention to detail required in the surgeon’s choice of both stapler and buttress material. The specific areas being stapled (fundus versus antrum, stomach versus small bowel), as well as the choice of stapling device and buttress material, must all be compatible.
Hemorrhage from staple lines has been a difficult area to study. Intraoperatively, bleeding may be seen from staple lines externally and can range from obvious pulsatile bleeding to ambiguous oozing. Surgical clips or stitches are frequently used to achieve hemostasis. From a research standpoint, however, these incidents are difficult to quantify and often impossible to cull retrospectively from medical records because such maneuvers are frequently viewed as routine and may not be mentioned in operative reports. In addition, bleeding may occur internally (intraluminal) along staple lines and may not be detected until later in the postoperative recovery period. In these cases, it is likely that minor staple line bleeding usually goes undiagnosed, and when suspected, may or may not be treated with transfusion, according to clinical indications. Only in the most severe cases would definitive diagnosis (surgical re-exploration, or perhaps endoscopy) be obtained. From a research standpoint, therefore, there is very little hard data regarding buttress material and the incidence of bleeding, although trends towards decreased bleeding with buttress material have been noted.10 Two key prospective, randomized trials with data on the incidence of bleeding at the staple line have been reported.[14, 15] These investigators found that reinforcement of gastric staple lines with buttress material significantly reduced the number of surgical clips required to achieve hemostasis. By using the number of clips as a proxy for bleeding, these authors were able by extension to quantify the amount of bleeding along the staple lines, and showed that the buttress material at these particular sites really did reduce bleeding, i.e., the number of clips used.[14] However, their comparison group (nonbuttress material) did not have any instances requiring transfusion or other intervention; so the clinical relevance of this point, at least with regard to bleeding, is still debatable.

Clearly, experience and clinical judgment are needed to determine not only a global choice of buttress material in general, but also the exact surgical situations where its use may or may not be appropriate. Factors to consider include the staple height, the individual patient’s risk of bleeding, the thickness of tissue, the thickness of the buttress material, and the presence of scar tissue. Any of these factors may play a role in deciding whether to use buttress material, which type of material, and which stapling device to use with it. In summary, the most important basis for making these decisions is mature clinical judgment. Even with the optimum choice of stapling device and buttress material, these devices sometimes fail, so it is important to always inspect the staple line on both sides after firing the stapler, to ensure visually that the staples are well formed and the buttress material was properly deployed.

References
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5.    Downey DM, Harre JG, Dolan JP. Increased burst pressure in gastrointestinal staple-lines using reinforcement with a bioprosthetic material. Obes Surg. 2005;15:1379–1383.
6.    Arnold W, Shikora SA. A comparison of burst pressure between buttressed versus non-buttressed staple-lines in an animal model. Obes Surg. 2005;15:164–171.
7.    Baker RS, Foote J, Kemmeter P, Brady R, Vroegop T, Serveld M. The science of stapling and leaks. Obes Surg. 2004;14:1290–1298.
8.    Shikora SA. The use of staple-line reinforcement during laparoscopic gastric bypass. Obes Surg. 2004;14:1313–1320.
9.    Assalia A, Ueda K, Matteotti R, et al. Staple-line reinforcement with bovine pericardium in laparoscopic sleeve gastrectomy: experimental comparative study in pigs. Obes Surg. 2007;17:222–228.
10.    Consten EC, Gagner M, Pomp A, Inabnet WB. Decreased bleeding after laparoscopic sleeve gastrectomy with or without duodenal switch for morbid obesity using a stapled buttressed absorbable polymer membrane. Obes Surg. 2004;14:1360–1366.
11.    Basu NN, Leschinskey D, Heath DI. The use of Seamguard to buttress the suture repair of a staple line leak following laparoscopic gastric bypass for obesity. Obes Surg. 2008;18:896–897.
12.    Shikora SA, Tarnoff M. Reinforcing gastric staple lines with Peri-Strips Dry (PSD) may prevent gastric leak after laparoscopic roux-en-Y gastric bypass for morbid obesity. Obes Surg. 2002;12:474–475.
13.    Shikora SA, Kim JJ, Tarnoff ME. Reinforcing gastric staple-lines with bovine pericardial strips may decrease the likelihood of gastic leak after laparoscopic roux-en-Y gastric bypass for morbid obesity. Obes Surg. 2003;13:37–44.
14.    Angrisani L, Lorenzo M, Borrelli V, et al. The use of bovine pericardial strips on linear stapler to reduce extraluminal bleeding during laparoscopic gastric bypass: prospective randomized clinical trial. Obes Surg. 2004;14:1198–1202.
15.    Nguyen NT, Longoria M, Welbourne S, et al. Glycolide copolymer staple-line reinforcement reduces staple site bleeding during laparoscopic gastric bypass: a prospective randomized trial. Arch Surg. 2005;140:773–778.
16.    Yo LS, Consten EC, Quarles van Ufford HM, et al. Buttressing of the staple line in gastrointestinal anastomoses: overview of new technology designed to reduce perioperative complications.  Dig Surg. 2006;23:283–291.
17.    Chen B, Kiriakopoulos A, Tsakayannis D, et al. Reinforcement does not necessarily reduce the rate of staple line leaks after sleeve gastrectomy. A review of the literature and clinical experiences. Obes Surg. 2009;19:166–172.
18.    Deitel M, Crosby RD, Gagner M. The first international consensus summit for sleeve gastrectomy (SG), New York City, October 25–27, 2007. Obes Surg. 2008;18:487–496.
19.    Consten EC, Dakin GF, Gagner M. Intraluminal migration of bovine pericardial strips used to reinforce the gastric staple-line in laparoscopic bariatric surgery. Obes Surg. 2004;14:549–554.
20.    Yu S, Jastrow K, Clapp B, et al. Foreign material erosion after laparoscopic Roux-en-Y gastric bypass: findings and treatment. Surg Endosc. 2007;21:1216–1220.
21.    Shikora SA, Kim JJ, Tarnoff ME. Comparison of permanent and nonpermanent staple line buttressing materials for linear gastric staple lines during laparoscopic Roux-en-Y gastric bypass. Surg Obes Relat Dis. 2008;4(6):729–734.

Category: Past Articles, Review