Safety and Performance Evaluation of Su2ura Approximation,a New Suturing Device,in Pigs

Abstract

One of the challenging aspects of minimal invasive surgery (MIS) is intracorporal suturing, which can be significantly time-consuming. Therefore, there is a rising need for devices that can facilitate the suturing procedure in MIS. Su2ura Approximation Device (Su2ura Approximation) is a novel device developed to utilize the insertion of anchors threaded with stitches to allow a single action placement of a suture. The objective of this study was to evaluate the long-term safety and tissue approximation of Su2ura Approximation in comparison to Endo Stitch + Surgidac sutures in female domestic pigs. All incision sites were successfully closed by both methods. Firm consolidation within and around the incision site was noted in several animals in both treatment groups, which corresponded histopathologically to islands of ectopic cartilage or bone spicules within the fibrotic scar. These changes reflect heterotopic ossification that is commonly seen in the healing of abdominal operation sites in pigs. No other abnormal findings were observed throughout the study period. In conclusion, the use of Su2ura Approximation under the present experimental conditions revealed no safety concerns.

Introduction

Minimal invasive surgery (MIS) has become increasingly popular in the last 2 decades, and has been adopted for a wide array of surgical procedures. ^1,2 One of the more challenging aspects of MIS is intracorporal suturing, that is, suturing from within a body cavity as opposed to from the external surface of the body, which can be significantly time-consuming and can affect the amount of bleeding during the operation. ³ In addition, proper suturing is critical for satisfactory wound healing. ⁴ Intracorporal suturing is especially difficult to perform in a limited working space, where the angle between the instruments being used is narrow. ^5,6 In order to master this skill, surgeons require lengthy training. Hence, it is not surprising that suturing and knot tying are rated as a major hurdle during MIS, even for experienced surgeons. ^{7 –9} Therefore, there is a rising need for devices that can facilitate the suturing procedure in MIS. Indeed, throughout the years, several devices, robotic systems, and alternatives to suturing have been developed, in order to allow easier and quicker knot tying. ^{10 –18}

Su2ura Approximation (Anchora Medical Ltd) is a novel device developed to utilize the insertion of anchors threaded with stitches to bypass the standard passing of a needle from one side of the tissue to the other as performed in traditional suturing (Figure 1; Supp Figure 1). This anchor feature allows a single action placement of a suture for easier MIS suturing, which is intended to help surgeons on a variety of MIS skill levels.

Figure 1.

Illustration of suturing with the Su2ura Approximation device. The device can be used for different stitch configurations.

The objective of this study was to evaluate the long-term safety and tissue approximation success of Su2ura Approximation upon suturing an internal incision by laparoscopic surgery in female domestic pigs. Both safety and tissue approximation success of Su2ura Approximation were compared to the Endo Stitch device using Surgidac sutures (Covidien), serving as the control item. ¹⁹

Materials and Methods

Animal Husbandry and Maintenance

A total of 8 female Landrace cross domestic swine, 5-month-old and with body weight of 47.1 to 55.4 kg, were obtained from Ya’ar Shivuk, I’bllin, Israel. The animals were housed at Biotech Farm Ltd, Na’an, Israel, a GLP-compliant facility. Animals were provided with commercially available pig diet approximately 1% to 2% of the pig’s body weight/day and allowed free access to drinking water. Environmental conditions were set to maintain temperature at 17 °C to 30 °C with a relative humidity of about 30% to 70% and a 12-hr light/12-hr dark cycle. This model was chosen as the pig is the most common large animal species used for in vivo studies involving laparoscopic surgeries. ²⁰

The study was approved by the Israeli National Council for Animal Experimentation (No. IL-19-6-262). The study was performed in compliance with ISO 10993-6, “Biological evaluation of medical devices—Part 6: Tests for local effects after implantation”; Third edition issued on December 1, 2016. Animal handling was performed according to guidelines of the National Institute of Health and the Israeli Council for Experiments on Animals.

Experimental Design

The animals were randomized to 2 groups: 5 animals were allocated to the Su2ura Approximation group and 3 animals were allocated to the Endo Stitch + Surgidac Suture group. On the day of surgery, buprenorphine was administered by intramuscular (IM) injection at a dose level of ∼0.005 mg/kg and then animals were tranquilized and sedated by IM injection of a combination of Ketamine HCl 20 mg/kg + Xylazine 2 mg/kg + Atropine 1 mg/animal. After sedation was achieved, animals were subjected to inhalation of Isoflurane 5% in 100% O₂ at a rate of 2 to 4 L/min via face mask. Thereafter, animals were intubated, and anesthesia was maintained at 1% to 3% Isoflurane. After CO₂ insufflation of the abdomen, 3 trocars were introduced into the abdomen: 1 for the camera and 2 for laparoscopic devices (Figure 2). Four incision sites were created for each animal in the study, excluding a single case from the Su2ura Approximation group, where only 3 incision sites were created. Each incision in the abdominal wall muscle was approximately 5 cm long. The cut was made using laparoscopic scissors from within the abdominal cavity, through the entire muscular layer (care was taken not to cut through the subcutaneous layer).

Figure 2.

Scheme of entry ports and incision sites arrangement.

Each incision was sutured with both interrupted and continuous patterns using either Su2ura Approximation or Endo Stitch + Surgidac. Each incision site was divided into 3 to 6 sections and a range of 8 to 23 of either anchors in Su2ura Approximation or needle passes in Endo Stitch + Surgidac were placed in each section, according to the decision of the surgeon, and closed with a knot (Supp Table 1).

Su2ura Approximation

Anchors were placed on both sides of the incision. The Su2ura Approximation device shaft was retracted outside of the body and the distal thread end was held with a laparoscopic grasper and was pulled from the port. An extracorporal sliding knot was made. The knot pushing cap was placed on the distal part of the shaft and the thread was placed in its intended position. The knot was then pushed into the body using the Su2ura Approximation device and tightened at the incision site. These steps were repeated until the incision was fully closed.

Endo Stitch + Surgidac Suture

Endo Stitch + Surgidac Suture were used in accordance with its instructions for use, with the following exceptions: The operator performed several passes from each side of the incision. The closing knot was made outside of the body using an extracorporal sliding knot. The knot was then pushed into the body using a knot pusher and tightened at the incision site. These steps were repeated until the incision was fully closed.

In all animals, following closure of the last incision site, the canulae used for the laparoscopic devices and camera were removed and the incision made for entry of the laparoscopic devices and camera was closed manually using the same commercial suture in all animals (neither Su2ura nor Endo Stitch). Antibiotic ointment was topically applied, and each site was bandaged by adhesive wound dressing and tubular elastic bandage on top. Ketoprofen was administered by IM injection at a dose level of 4 mg/kg after the surgical procedure and continued to be injected once daily for 3 subsequent days. One incision site from one animal from the Su2ura Approximation group was excluded from the study since the site was located near the ribs, where the muscle tissue is thin, and anchors or sutures could not be placed. Thus, this animal had only 3 incisions.

Observations and Examinations

Animals were observed for approximately 13 weeks. Detailed clinical examinations of both systemic and local reactions were carried out on all animals on the day of surgery and once daily for the first week post-surgery. Thereafter, animals were observed once weekly throughout the entire observation period. All observations were recorded. Special attention was given to the approximate sites of internal incisions for any local reaction and/or hernia formation (indicative of incision opening) by superficial palpation. Individual body weights of all animals were recorded following their receipt, and then on the day of surgery and once weekly thereafter. The last body weight determination was recorded on the day of euthanasia, prior to necropsy.

Animals were euthanized 13 weeks after the surgical procedure and were dissected so that the abdominal inner surface was carefully examined for appearance of the incisions and surrounding tissue, uniformity and texture of tissue, success of approximation of the wounds, the presence of any herniation through the incisions, any adhesion of internal organs to the incisions, and evaluation of the internal organs for any pathological injury. The incision sites were also photographed.

All Su2ura or Endo Stitch + Surgidac incision sites were collected from all animals during the scheduled necropsy and fixed in 10% neutral buffered formalin (approximately 4% formaldehyde solution). The draining lymph nodes (inguinal and axillary) were also collected from both sides and preserved in 10% neutral buffered formalin. Each incision site was trimmed in oblique orientation to capture maximal number of the stainless-steel anchors for Su2ura Approximation or needle penetration suturing sites for Endo Stitch + Surgidac Suture (Supp Figure 2). Paraffin embedding was used for soft items (Endo Stitch + Surgidac Suture), while resin embedding was used for the hard items (Su2ura Approximation).

Paraffin embedding incision sites were sectioned at approximately 3 to 5 microns thickness and stained with Hematoxylin & Eosin (H&E). Resin embedding incision sites with the anchors in place were sectioned and ground/micropolished at approximately 40 to 100 microns thickness and stained with H&E.

Cell Type/Response was evaluated histologically by a board-certified veterinary pathologist using a 0 to 4 scoring grade as described in the ISO 10993-6 standard (Supp Table 2) focusing on extent of neovascularization, fibrosis/fibrous capsule, and fatty infiltrate (Supp Table 3). In addition, the sections were evaluated subjectively.

Statistical Analysis

Calculations were performed using MeanSDRelative_01.2.Rnw and Microsoft Excel 365 (both transcription of raw data and formulae were 100% checked).

Results

Mortality, Clinical Signs, and Body Weights

No mortality occurred in any of the animals throughout the entire observation period. During the first 2 weeks post-surgical procedure, mild irregularities of the abdominal wall muscle layer were noted during superficial palpation in several incision sites, all in the Endo Stitch + Surgidac Suture group. These irregularities most likely formed since the Endo Stitch device enables tissue approximation in large bites of tissue along the suture line with fewer needle passes, which can lead to a surface which is not smooth and uniform. This was resolved within 2 weeks of post-surgery. No such observation was recorded for the Su2ura Approximation group.

Minimal to mild soft swelling was noted in several control and test sites a day following surgery and recovery was evident within 4 weeks in control sites and within 3 weeks in the test sites. This swelling is an expected reaction to the surgical procedure.

In addition, a hard mass (approximately 2 cm in diameter) was observed (diagnosed as scar tissue by histopathological examination) in a single incision site of a Su2ura Approximation-treated animal (#503) from the fifth week following the surgical procedure until the end of the observation period. All animals gained weight to a similar extent during the observation period.

Approximation Evaluation

All incision sites were successfully closed by either Su2ura Approximation or Endo Stitch + Surgidac Suture, as assessed at the end of surgery and at necropsy, by both visual examination and external palpation and no herniation was noted (Supp Figure 3).

Macroscopic Observations

Su2ura Approximation group

Adhesion of the mesentery to the body wall at the incision sites was observed in 1 to 2 sites in all animals assigned to the Su2ura Approximation group. Adhesion of the liver to the body wall at one incision site was observed in a single animal from this group. In addition, minimal, hard or firm consolidation of tissues (diagnosed as scar tissue by histopathological examination) within and around the incision site was recorded in 3 of 5 animals (#498, 501, 503) at several sites.

An island of bone spicules (confirmed histologically) at 3 sites spread across 2 of 5 animals (#299, 501) and a structure composed of ectopic cartilage and bone spicules (confirmed histologically) that connected 3 of the incision sites and crossed the laparoscopic entry port in the midline in 1 animal (#500) were also noted in this group.

A similar island of ectopic cartilage or bone spicules was found at the laparoscopic entry ports of another animal (#503) from this group.

Endo Stitch +Surgidac Suture group

Adhesion of the mesentery or colon to the body wall at the incision site was noted in a single animal. In addition, hard firm consolidation of tissues (diagnosed as scar tissue by histopathological examination) within and around the incision site was recorded for all the sites in this animal. A very small island of ectopic cartilage or bone spicules was found in one of the laparoscopic entry ports of a second animal. No gross lesions were macroscopically observed in the third animal in this group.

Microscopic Findings

Tissue reaction

The tissue reaction surrounding the metal component of the Su2ura Approximation device consisted only of fibrosis, while the tissue reaction surrounding the threads consisted of an expected minimally severe foreign body reaction (FBR), not considered to be adverse, since no alteration in the function of the test organism or affected organ/tissue was noted, and since this is an inherent biological property of the animal model (Supp Table 4; Figure 3A and B). ²¹ This FBR was comparable in nature and severity to the reaction associated with the stitches of the Endo Stitch + Surgidac Suture group (Figure 4A and B). Evaluation using the scoring method described in the ISO 10993-6 standard resulted in the same score for every animal, regardless of suture type.

Figure 3.

A and B, Tissue reaction in an incision site treated with Su2ura Approximation device. Low (A) and high (B) magnification of an internal incision site, 13 weeks following laparoscopic surgery. The operation site, including the anchors (arrowhead—part of the Su2ura Approximation device) is characterized by the presence of fibrotic scar (ie, mature granulation tissue; broken lines arrow). Star indicates the location of the intact abdominal wall muscle (fascia). Thin arrows indicate the presence of the thread remnants (part of the Su2ura Approximation device), surrounded by minimal foreign body reaction. C and D, Heterotopic cartilage reaction in an incision site treated with Su2ura Approximation device. Low (C) and high (D) magnification of an internal incision site, 13 weeks following laparoscopic surgery. The operation site is characterized by the presence of fibrotic scar (ie, mature granulation tissue; broken lines arrow). Star indicates the location of the intact abdominal wall muscle (fascia). Open arrow indicates the presence of heterotopic cartilage and/or bone located within the granulation tissue. Thin arrows indicate the presence of the thread remnants (part of the Su2ura Approximation device), surrounded by minimal foreign body reaction.

Figure 4.

A and B, Tissue reaction in an incision site treated with Endo Stitch + Surgidac Suture device. Low (A) and high (B) magnification of an internal incision site, 13 weeks following laparoscopic surgery. The operation site is characterized by the presence of fibrotic scar (ie, mature granulation tissue; broken lines arrows). Stars indicate the location of the intact abdominal wall muscle (fascia). Thin arrows indicate the presence of suture remnants, surrounded by minimal foreign body reaction. C and D, Heterotopic cartilage reaction in an incision site treated with Endo Stitch + Surgidac Suture device. Low (C) and high (D) magnification of an internal incision site, 13 weeks following laparoscopic surgery. The operation site is characterized by the presence of fibrotic scar (ie, mature granulation tissue; broken lines arrows). Star indicates the location of the intact abdominal wall muscle (fascia). Open arrows indicate the presence of heterotopic cartilage and/or bone located within the granulation tissue. Thin arrows indicate the presence of suture remnants, surrounded by minimal foreign body reaction.

Gross abnormalities detected

In all cases where macroscopic changes indicated consolidation of tissues within and around the incision site and cartilage or bone-like structure within the incision site, histopathological evaluation indicated the presence of islands of ectopic cartilage or bone spicules within the fibrotic scar (Figure 3C and D and Figure 4C and D).

The incidence of islands of ectopic cartilage or bone spicules within the fibrotic scar was relatively comparable when comparing the 2 types of suture methods, and the presence of this finding should not be considered related to a specific suture method.

Discussion

This study was designed to evaluate the long-term safety and tissue approximation success of Su2ura Approximation in comparison to a control device, the Endo Stitch + Surgidac Suture, in female domestic pigs. Tissue approximation by Su2ura Approximation, using a laparoscopic approach following an internal incision, was successful and all sutures remained closed.

An interesting histopathological observation was the finding of islands of ectopic cartilage or bone spicules within the fibrotic scar. These histopathologic changes corresponded to the macroscopic observation of consolidation of tissues within and around the incision sites and port site that were observed macroscopically. The formation of bony structures in an aberrant location is defined as heterotopic (ectopic) ossification. Such structures can form from osseous metaplasia of proliferating fibrous tissues, or from endochondral ossification of cartilaginous tissue. Such heterotopic ossifications can be observed in many tissues and usually bear no pathologic importance. ²² Surgical scars can also undergo ossification, and such findings have also been reported specifically in the peritoneal cavity of pigs. ²² Such changes have been attributed to trauma, hemorrhage, and inflammation. While heterotopic ossification is considered an incidental finding in pigs, it can rarely lead to other conditions, such as intestinal necrosis due to obstruction by adhesions that surround the bone, intestinal perforation by the bone, or by hindering intestinal movement, leading to constipation. ²³ In the current study, the heterotopic ossifications were seen in samples in which the Endo Stitch + Surgidac Suture and the Su2ura Approximation were used, and therefore it is not suggested to be associated with a specific device and was considered to be a feature of healing from the surgical procedure in this model.

Interestingly, a similar condition has been also reported in humans following abdominal surgeries, and is termed traumatic myositis ossificans. ^24,25 The pathophysiology in humans is postulated to be similar to that in pigs, with severe inflammatory stimulus leading to metaplasia of multipotent mesenchymal cells, or surgical implantation of periosteum or bone into the soft tissues. ^{26 –29} Since these changes are considered benign and carry a favorable prognosis, they are usually treated conservatively, avoiding further surgeries. ^30,31

In view of the reported in-life findings and under the conditions of this study, it is concluded that tissue approximation by the Su2ura Approximation, using a laparoscopic approach following an internal incision in female domestic pigs, was successful and all sutures remained closed. The histopathological data indicated that long-term safety evaluation of Su2ura Approximation compared to Endo Stitch + Surgidac Suture had similar individual and group reaction scoring without any difference in the scored parameters. The use of the Su2ura Approximation under the present experimental conditions revealed no safety concerns, with no adverse findings or undue reactivity, compared to the Endo Stitch + Surgidac Suture.

Supplemental Material

Supplemental Material, sj-docx-1-tpx-10.1177_01926233211067960 - Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs

Supplemental Material, sj-docx-1-tpx-10.1177_01926233211067960 for Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs by Yuval Ramot, Serge Rousselle, Michal Steiner, Yossi Lavie, Nati Ezov and Abraham Nyska in Toxicologic Pathology

Supplemental Material

Supplemental Material, sj-docx-2-tpx-10.1177_01926233211067960 - Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs

Supplemental Material, sj-docx-2-tpx-10.1177_01926233211067960 for Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs by Yuval Ramot, Serge Rousselle, Michal Steiner, Yossi Lavie, Nati Ezov and Abraham Nyska in Toxicologic Pathology

Supplemental Material

Supplemental Material, sj-tif-1-tpx-10.1177_01926233211067960 - Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs

Supplemental Material, sj-tif-1-tpx-10.1177_01926233211067960 for Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs by Yuval Ramot, Serge Rousselle, Michal Steiner, Yossi Lavie, Nati Ezov and Abraham Nyska in Toxicologic Pathology

Supplemental Material

Supplemental Material, sj-tif-2-tpx-10.1177_01926233211067960 - Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs

Supplemental Material, sj-tif-2-tpx-10.1177_01926233211067960 for Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs by Yuval Ramot, Serge Rousselle, Michal Steiner, Yossi Lavie, Nati Ezov and Abraham Nyska in Toxicologic Pathology

Supplemental Material

Supplemental Material, sj-tif-3-tpx-10.1177_01926233211067960 - Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs

Supplemental Material, sj-tif-3-tpx-10.1177_01926233211067960 for Safety and Performance Evaluation of Su2ura Approximation, a New Suturing Device, in Pigs by Yuval Ramot, Serge Rousselle, Michal Steiner, Yossi Lavie, Nati Ezov and Abraham Nyska in Toxicologic Pathology