Novel zinc alloys for biodegradable surgical staples

BACKGROUND The development of biodegradable surgical staples is desirable as non-biodegradable Ti alloy staples reside in the human body long after wound healing, which can cause allergic/foreign-body reactions, adhesion, or other adverse effects. In order to develop a biodegradable alloy suitable for the fabrication of surgical staples, we hypothesized that Zn, a known biodegradable metal, could be alloyed with various elements to improve the mechanical properties while retaining biodegradability and biocompatibility. Considering their biocompatibility, Mg, Ca, Mn, and Cu were selected as candidate alloying elements, alongside Ti, the main material of clinically available surgical staples.AIM To investigate the in vitro mechanical properties and degradation behavior and in vivo safety and feasibility of biodegradable Zn alloy staples.METHODS Tensile and bending tests were conducted to evaluate the mechanical properties of binary Zn alloys with 0.1–6 wt.% Mg, Ca, Mn, Cu, or Ti. Based on the results,three promising Zn alloy compositions were devised for staple applications(wt.%): Zn-1.0Cu-0.2Mn-0.1Ti(Zn alloy 1), Zn-1.0Mn-0.1Ti(Zn alloy 2), and Zn-1.0Cu-0.1Ti(Zn alloy 3). Immersion tests were performed at 37℃ for 4 wk using fed-state simulated intestinal fluid(Fe SSIF) and Hank’s balanced salt solution(HBSS). The corrosion rate was estimated from the weight loss of staples during immersion. Nine rabbits were subjected to gastric resection using each Zn alloy staple, and a clinically available Ti staple was used for another group of nine rabbits. Three in each group were sacrificed at 1, 4, and 12 wk post-operation.RESULTS Additions of ≤1 wt.% Mn or Cu and 0.1 wt.% Ti improved the yield strength without excessive deterioration of elongation or bendability. Immersion tests revealed no gas evolution or staple fracture in any of the Zn alloy staples. The corrosion rates of Zn alloy staples 1, 2, and 3 were 0.02 mm/year in HBSS and 0.12, 0.11, and 0.13 mm/year, respectively, in Fe SSIF. These degradation times are sufficient for wound healing. The degradation rate is notably increased under low pH conditions. Scanning electron microscopy and energy dispersive spectrometry surface analyses of the staples after immersion indicated that the component elements eluted as ions in Fe SSIF, whereas corrosion products were produced in HBSS, inhibiting Zn dissolution. In the animal study, none of the Zn alloy staples caused technical failure, and all rabbits survived without complications. Histopathological analysis revealed no severe inflammatory reaction around the Zn alloy staples.CONCLUSION Staples made of Zn-1.0Cu-0.2Mn-0.1Ti, Zn-1.0Mn-0.1Ti, and Zn-1.0Cu-0.1Ti exhibit acceptable in vitro mechanical properties, proper degradation behavior,and in vivo safety and feasibility. They are promising candidates for biodegradable staples.

Gastroenteroanastomosis Techniques for Laparoscopic Gastric Bypass: Linear vs Circular Stapler

Background: Laparoscopic Roux-en-Y gastric bypass (LRYGB) is an effective and well-accepted procedure for the treatment of morbid obesity but has complications such as stenosis of the gastroenteroanastomosis (GE), GE leak, surgical site infection, and stapling malfunction. This study evaluated the efficiency of weight loss and the incidence of short- and mid-term postoperative complications in patients undergoing LRYGB in which anastomosis was performed using a linear stapler (LSA) or a circular stapler (CSA). Methods: Prospective observational study conducted between April 2016 and March 2019. The data were extracted from a hospital database that includes patients undergoing LRYGB in two different GE techniques, assessing postoperative complications and excess body weight loss. Results: Data from 457 patients were analyzed, of which 216 were in the LSA group and 241 were in the CSA group. There were four cases (1.7%) of GE stenosis in the CSA group and only one (0.5%) in the LSA group. Stapler malfunction occurred in both groups: CSA (0.4%) and LSA (0.5%), and a GE leak developed only in the CSA group (0.4%). Surgical site infection was found in five patients in the CSA group (2.1%) and two in the LSA group (0.9%). No statistical difference was found between the two groups in any of the variables analyzed (p > 0.05). Conclusions: Both stapling techniques resulted in a similar loss of excess body weight during the follow-up period. Although the LSA group had fewer total complications, these were not statistically significant, which substantiates the fact that both techniques are safe and feasible, provided they are performed by a surgeon with a long learning curve in laparoscopic bariatric surgery.

Biodegradable high-nitrogen iron alloy anastomotic staples:In vitro and in vivo studies

For gastrointestinal anastomosis,metallic biodegradable staples have a broad application potential.However,both magnesium and zinc alloys have relatively low strength to withstand the repeated peristalsis of the gastrointestinal tract.In this study,we developed a novel kind of biodegradable high-nitrogen iron(HN–Fe)alloy wires(0.23 mm),which were fabricated into the staples.The tensile results showed that the ultimate tensile strength and elongation of HN–Fe wires were 1023.2 MPa and 51.0%,respectively,which was much higher than those of other biodegradable wires.The degradation rate in vitro of HN–Fe wires was slightly higher than that of pure Fe wires.After 28 days of immersion,the tensile strength of HN–Fe wires remained not less than 240 MPa,meeting the clinical requirements.Furthermore,sixteen rabbits were enrolled to conduct a comparison experiment using HN–Fe and clinical Ti staples for gastroanastomosis.After 6 months of implantation,a homogeneous degradation product layer on HN–Fe staples was observed and no fracture occurred.The degradation rate of HN–Fe staples in vivo was significantly higher than that in vitro,and they were expected to be completely degraded in 2 years.Meanwhile,both benign cutting and closure performance of HN–Fe staples ensured that all the animals did not experience hemorrhage and anastomotic fistula during the observation.The anastomosis site healed without histopathological change,inflammatory reaction and abnormal blood routine and biochemistry,demonstrating good biocompatibility of HN–Fe staples.Thereby,the favorable performance makes the HN–Fe staples developed in this work a promising candidate for gastrointestinal anastomosis.

Surgical staples:Current state-of-the-art and future prospective

Wound closing is one of the widely performed and prominent clinical practices in the surgical intervention process.A physician or surgeon has several options ranging from surgical sutures and adhesive strips to fibrin glue for effective wound closure to close the commonly occurring surgical cuts and deep skin tissue injuries.However,all the commercially available wound closure devices have some limitations in each and another perspective.From the beginning of the late 90s,surgical staples got tremendous attention as efficient wound closure devices for their time-effective and sufficient mechanical strength,performance feasibility,fewer chances of surgical site infection and require minimal expertise characteristics in consideration of remote location.Even in the context of the recent COVID19 pandemic,the clinical acceptance and patient compliance for the staples have increased due to minimizing the chances of prolonged interaction between the patient and physicians.The surgical staples application is extensive and diversified,ranging from common external cuts to highly complex surgery procedures like laparoscopic appendectomy,intestinal anastomosis,etc.Thus,in this literature review,we try to give a comprehensive glimpse of the development and current state-of-the-art surgical staples in consideration with research from a commercial point of view.On a special note,this review also describes a very brief outline of the regulatory aspects and some common internationally acceptable‘de jure standards for the development of commercially viable surgical staples.

The mechanical property and corrosion resistance of Mg-Zn-Nd alloy fine wires in vitro and in vivo

Titanium and its alloy are commonly used as surgical staples in the reconstruction of intestinal tract and stomach,however they cannot be absorbed in human body,which may cause a series of complications to influence further diagnosis.Magnesium and its alloy have great potential as surgical staples,because they can be degraded in human body and have good mechanical properties and biocompatibility.In this study,Mg-2Zn-0.5Nd(ZN20)alloy fine wires showed great potential as surgical staples.The ultimate tensile strength and elongation of ZN20 alloy fine wires were 248 MPa and 13%,respectively,which could be benefit for the deformation of the surgical staples from U-shape to B-shape.The bursting pressure of the wire was about 40 kPa,implying that it can supply sufficient mechanical support after anastomosis.Biochemical test and histological analysis illustrated good biocompatibility and biological safety of ZN20 alloy fine wire.The residual tensile stress formed on the outside of ZN20 fine wire during drawing would accelerate the corrosion.The second phase had a negative influence on corrosion property due to galvanic corrosion.The corrosion rate in vitro was faster than that in vivo due to the capsule formed on the surface of ZN20 alloy fine wire.