Gastric dilatation and volvulus is common and often fatal in large- and giant-breed dogs,1 and gastropex y, per formed with various techniques, has been used for many years to prevent recurrence of gastric dilatation and volvulus. Currently, incisional gastropexy is the most common technique used for open-surgery gastropexy in dogs; however, other techniques (eg, circumcostal and belt-loop techniques) are also described.1 Although such open-surgery gastropexy techniques are fairly safe and effective,1–6 the use of alternative minimally invasive gastropexy has lower postoperative morbidity and promotes rapid recovery and has been expanded as a prophylactic procedure.7–9 Two key minimally invasive techniques are laparoscopic-assisted gastropexy9–13 and TLG.14–20 Compared with open gastropexy and laparoscopic-assisted gastropexy, TLG is less invasive, has a lower rate of wound healing complications, and ameliorates postoperative recovery but has longer surgical duration and requires more surgical skill, with longer learning curves.21 In addition, TLG in dogs may be performed without the difficulty of intracorporeal knot tying and with a mean duration of surgery reported as 20.8 minutes18 to 70 minutes.20 In human medicine, surgical repair of abdominal wall hernias is less complex and faster when performed laparoscopically with the use of AFSs, compared with sutures, and the AFSs facilitate fast and secure fixation of surgical mesh to the hernia defect site.22 In addition, the use of AFSs in laparoscopic repair of abdominal wall hernias in humans allows for the use of absorbable tackers instead of transfascial sutures.22
Therefore, we hypothesized that when tested on specimens from cadaveric dogs, AFSs could mechanically affix the stomach to the body wall as well as could absorbable knotless (barbed) monofilament suture. In particular, the objectives of the study presented here were to compare results of load to failure for AFSs deployed at various angles and for AFSs versus absorbable knotless (barbed) sutures when used in simulated TLG in specimens from cadaveric dogs.
Materials and Methods
Samples
Thirty stomach and abdominal body wall specimens were harvested from cadavers of medium-sized and large dogs euthanized at the Section of Veterinary Clinics and Animal Production, University of Bari, Italy, between January 2018 and June 2019, for reasons unrelated to our study. For each dog, owner permission was obtained for harvest and use of the tissues, which were then harvested within 24 to 36 hours after euthanasia and tested within 1 hour after harvest. Medium-sized dogs were defined as those that had a body weight of 12 to 20 kg and a body condition score of 3 (on a scale of 1 to 5). Large dogs were defined as those that had a body weight > 20 kg and a body condition score of 3. Specimens were assigned randomly to 1 of 3 groups for use as simulated TLG constructs for comparisons of load-to-failure results for single AFSsa deployed at 30°, 60°, or 90° (AFS-angle group; n = 10) or for comparisons of load-to-failure results for 3-0 absorbable knotless (barbed) monofilament sutureb (TLG-1; 10) versus 8 AFSs (TLG-2; 10).
AFSs
The AFSs used were 6.7 × 4.0-mm mechanical fixation straps made of a blend of polydioxanone and an L(−)-lactide and glycolide copolymer. Each AFS had 2 points of fixation designed to secure prosthetic material to soft tissue. The AFSs were deployed with a laparoscopic applicator devicec (0.5 × 36 cm) that could hold 25 AFSs.
AFS-angle test
A group of 10 stomach and abdominal body wall specimens (AFS-angle group) were used to evaluate load to failure for constructs with AFSs deployed at 30°, 60°, or 90°. One individual (LL) deployed all AFSs used in the ASF-angle group. For each stomach and abdominal body wall specimen, the seromuscular layer of the stomach proximal to the pyloric antrum was grasped with 5-mm laparoscopic atraumatic Babcock forceps and, in doing so, slipped the gastric mucosa layer from the seromuscular plica created. The purpose of this technique was to best ensure that the gastric mucosa layer was not penetrated by an AFS. The seromuscular plica was then set on the abdominal wall that was fixed with 4 bolts to the base of a construct cage (Figure 1), and a single AFS was deployed at a test angle of 30°, 60°, or 90° on the basis of the angle between the AFS applicator device and the abdominal wall. To ensure the angle of deployment, each AFS was deployed with the laparoscopic applicator device inserted through a 5-mm laparoscopic trocar fixed to the construct cage and angled 30°, 60°, or 90° relative to the abdominal wall fixed to the base of the cage. A biomechanical tensile test to determine load to failure was performed for each AFS placed. Each specimen was used to perform a maximum of 3 tests, and each angle was tested in each specimen on a rotational basis.
Representative image of the tensile strength device testing load to failure (N) on a construct of a simulated TLG performed on 1 of 30 stomach and abdominal body wall specimens harvested from cadavers of medium-sized and large dogs euthanized for reasons unrelated to our study. The image shows the abdominal body wall portion (asterisk) of the construct held to the cage base with 4 bolts and the stomach portion (dagger) clamped in a custom-made vise (British pound sign) attached to a load cell (yellow arrow) while distraction is applied with an electric actuator (black arrow) at a rate of 0.5 mm/s. The image also shows a 5-mm laparoscopic trocar (red arrow) fixed to the cage and angled at 30° relative to the abdominal wall and an AFS applicator device (white arrow) partially inserted thorough the trocar.
Citation: American Journal of Veterinary Research 81, 7; 10.2460/ajvr.81.7.594
AFS versus absorbable knotless suture
For the TLG-1, the 10 simulated gastropexies were performed by the same operator (LL) by suturing the stomach seromuscular layer to the abdominal body wall with a single line of 3-0 absorbable knotless monofilament suture applied in a simple continuous pattern that included 7 suture bites placed over a distance of 4 to 5 cm. For the TLG-2, the seromuscular layer of the stomach proximal to the pyloric antrum was grasped with 5-mm laparoscopic atraumatic Babcock forceps and set on the abdominal wall, as was done in the AFS-angle test. The same length of gastropexy (4 to 5 cm) was achieved with 8 AFSs applied with deployment angles > 30° (Figure 2), then a biomechanical tensile test was performed to determine load to failure. All AFSs for the 10 simulated gastropexies were placed by the same individual (LL).
Representative image of a TLG gastropexy for constructs in TLG-2, with AFSs (arrows) deployed at angles > 30° through the stomach seromuscular plica (British pound sign), attaching the stomach portion (dagger) of the construct to the abdominal body wall portion (asterisk).
Citation: American Journal of Veterinary Research 81, 7; 10.2460/ajvr.81.7.594
Biomechanical test
A tensile strength device was used to determine load-to-failure force (N) for all constructs in the study (Figure 1). The abdominal body wall portion of the construct was attached to the base of the cage with 4 bolts, and the stomach was clamped in a custom-made vise and attached to a load cell.d Distraction was applied with an electric actuatore at a rate of 0.5 mm/s. Failure was defined as rupture of the suture, AFS, or tissues. Tensile strength was recorded with dedicated software.f
Statistical analysis
Statistical analysis was performed with available software.g Data were assessed for normality of distribution with the Shapiro-Wilk test. Data were reported as the mean ± SD, median, range, and IQR. A 1-way ANOVA was used to compare results among AFS deployment angles (30°, 60°, or 90°) and between TLG-1 and TLG-2. Values of P < 0.05 were considered significant.
Results
Samples
Of the 30 stomach and abdominal body wall specimens harvested from dog cadavers, 18 were from medium-sized dogs (mean ± SD body weight, 17.90 ± 3.66 kg) and 12 were from large dogs (mean ± SD body weight, 37.95 ± 7.60 kg). The AFS-angle group had 3 medium-sized and 7 large dogs. The TLG-1 had 6 medium-sized and 4 large dogs. The TLG-2 had 9 medium-sized and 1 large dog. Composition on the basis of body weight did not differ substantially among the groups.
AFS-angle test
There was no failure of the transversus abdominis muscle, penetration of AFSs through the gastric mucosa layer, or slippage of the constructs. Mean ± SD load to failure was significantly (P < 0.05) higher for AFS deployment angles of 60° (8.00 ± 3.90 N; n = 10) and 90° (12.71 ± 8.00 N; 10), compared with 30° (5.17 ± 1.90 N; 10; Figure 3).
Box-and-whisker plots of the results for tensile strength testing of load to failure (N) for gastropexy constructs described in Figure 1 for single AFSs with a deployment angle of 30° (n = 10), 60° (10), or 90°(10) affixing the stomach portion of the construct to the abdominal wall portion of the construct. Each box represents data from the 25th to the 75th percentiles, the bold line in the box represents the median, the whiskers represent the range, and the open circles represent outliers.
Citation: American Journal of Veterinary Research 81, 7; 10.2460/ajvr.81.7.594
AFS versus absorbable knotless suture
Similar to the AFS-angle test results, there was no failure of the transversus abdominis muscle, penetration of AFSs through the gastric mucosa layer of the stomach, or slippage of the constructs used to assess load to failure for AFS versus absorbable knotless suture (Figure 4). Mean ± SD load to failure was 39.18 ± 7.10 N (median, 40.20 N; IQR, 36.25 to 43.82 N; range, 27.40 to 46.00 N) for TLG-1 and 31.43 ± 10.86 N (median, 32.30 N; IQR, 37.40 to 39.20 N; range, 13.70 to 46.00 N) for TLG-2. No significant (P = 0.324) difference in mean load to failure was detected for TLG-1 versus TLG-2.
Representative images of gross evaluation of a TLG construct described in Figure 1 after undergoing load-to-failure testing. A—The stomach has been sectioned for inspection. The gastric mucosa (M) is visible in addition to the stomach seromuscular plica (SSE) through which AFSs (arrow) affix the stomach to the abdominal wall (AW). B—An image of the construct with the stomach transected and showing that the gastric mucosal surface overlying the TLG line (arrowhead) has not been punctured by any AFSs. C—An image of the construct with much of the gastric mucosa removed to show mucosal integrity as it overlies the TLG line (arrowhead) created by the stomach seromuscular plica affixed to the abdominal wall. D—An image of the construct with the abdominal wall portion sectioned to show an AFS (arrow) and the depth of AFS penetration into the muscle of the abdominal wall. E—A close-up of the isolated gastropexy from a construct showing the penetration of an AFS (arrow) through the stomach seromuscular plica and parietal peritoneum (P) and into the abdominal body wall, which has been sectioned here to better show the depth and position of an AFS (arrow).
Citation: American Journal of Veterinary Research 81, 7; 10.2460/ajvr.81.7.594
Discussion
The present study was an ex vivo evaluation of acute load to failure of AFSs when used in simulated laparoscopic gastropexy on stomach and abdominal wall specimens harvested from cadavers of dogs. We tested the potential role of AFS deployment angle, for which there are few studies22 on the fixation strength of AFSs at acute deployment angles. Therefore, we decided to test AFS deployment angles of 30°, 60°, and 90°.
Results of the present study indicated that the tensile strength of AFSs deployed into the isolated cadaveric tissues at an angle of 30° was significantly (P < 0.05) lower than that of 60° and 90°. This finding suggested that AFS deployment angles > 30° should be used for gastropexy in dogs. We speculated that AFS deployment angles > 30° could be achieved in vivo during TLG with the patient positioned in dorsal recumbency, a laparoscopy portal for the applicator device placed laterally and dorsally to the AFS deployment site, and the operator's hand on the abdominal wall to apply pressure and thereby position the body wall where needed, as described for TLG in dogs.21 In contrast to a study22 that shows the mean load to failure for constructs of absorbable mesh affixed to cadaveric porcine abdominal wall tissue with a single AFS was 12.95 to 18.04 N, depending on AFS deployment angle, the mean load to failure for individual AFSs was lower (5.17 to 12.71 N, depending on AFS deployment angle) in the present study. This difference could have been attributed to differences in the type of construct studied. In particular, we tested constructs that consisted of the stomach seromuscular layer affixed to the abdominal body wall, resulting in constructs with mechanical fixation of thicker tissue in the present study, compared with mechanical fixation of thinner absorbable mess in the previous study.22 Thus, it was understandable that the depth to which the AFSs reached into the abdominal body walls in the present study could have been less, resulting in lower mean load to failure.
In the present study, the same length of simulated TLG (4 to 5 cm) was used for TLG-1 and TLG-2 as has been used in other studies.18,23,24 Our results indicated no substantial difference in mean load to failure for TLG-1 versus TLG-2. In fact, our results were consistent with the load to failure reported in studies14,23,24 of double lines of knotless sutures.
The AFS used in the present study contained polydioxanone, similar to the suture that may be used in gastropexy. Moreover, polydioxanone suture is used in TLG because of less tissue drag and capillary effect, compared with braided suture.16,18 The absorbable knotless (barbed) monofilament suture used in the present study loses 50% of its tensile strength in 3 weeks after implantation,23,25 whereas the absorption profile for the copolymer blend in the AFSs of the present study is minimal during the first 2 weeks26 but essentially absorbed by approximately 12 to 18 months.26,27 To our knowledge, it is not known to what extent AFSs, like the ones used in the present study, would contribute to the tensile strength of a gastropexy 3 to 8 weeks after the surgery. In addition, the mechanical strength of the adhesion created during the healing process when AFSs are used is not known. Both of these aspects warrant further research.
In vivo, serosal scarification or cutting of abdominal wall and stomach by cauterization or incision contributes to a permanent adhesion.24 We suppose that in clinical settings, removal of the serosa, cauterization, or incision would be necessary to best ensure a reliable adhesion between the stomach and abdominal wall and should be addressed in any gastropexy technique. Relatedly, a studyh in dogs in a clinical setting shows that ultrasonography confirmed stable gastropexy at 4 weeks after TLG with cauterization of the serosa sites on the abdominal wall and stomach and use of AFSs.
Our study had limitations. The simulated TLGs performed to compare results for load to failure for AFSs versus an absorbable knotless suture were ex situ and not with full laparoscopic procedures. Similarly, Arbaugh et al23 also describe an ex situ approach as a first step in the use of knotless suture but did not evaluate the strength of gastropexy during healing. However, with our current knowledge of the AFSs used in the present report, we are confident that their use in TLG in vivo will provide successful outcomes, although this needs to be confirmed by a prospective clinical study with adequate long-term follow-up information before recommendations can be made. Care, however, should be taken to best ensure that the gastric mucosa is not penetrated by AFSs, a potential limitation of this technique and traditional gastropexy.24 For this reason, we used a 5-mm Babcock grasping forceps to create a seromuscular plica of the stomach to thereby best ensure AFSs or suture only penetrated the seromuscular layer of the stomach in constructs of the present study.
Compared with other TLG techniques, our findings indicated that TLG performed with AFSs required no suturing within the abdominal cavity, may be less technically demanding, and had similar loads to failure.h We therefore speculated that AFSs could be used to perform prophylactic minimally invasive gastropexy in dogs; however, research in clinical settings is warranted.
ABBREVIATIONS
| AFS | Absorbable fixation strap |
| IQR | Interquartile (25th to 75th percentile) range |
| TLG | Total laparoscopic gastropexy |
Footnotes
Ethicon SecureStrap absorbable fixation device strap, Ethicon US LLC, Cincinnati, Ohio.
V-loc 90 barbed absorbable wound closure device, Medtronic, New Haven, Conn.
Ethicon SecureStrap absorbable fixation device, Ethicon US LLC, Cincinnati, Ohio.
Model CTCE572T55, AEP Transducers SRL, Modena, Italy.
Model, AT377-P-JSP750 N, Justech AB, Landskrona, Sweden.
Quick Analyzer, version 2.0, AEP Transducers SRL, Modena, Italy.
MedCalc, version 14.1, MedCalc Software Ltd, Ostend, Belgium.
Fracassi L, Di Bella C, Stabile M, et al. Total laparoscopic gastropexy with PDS staples in the dog (abstr), in Proceedings. 72nd Convegno Sisvet, 2018;178.
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