Degradation of an ultrasonically welded device for surgical suture holding

Background: Nonabsorbable suture knots are usually used to link the tendon and bone during rotator cuff repair surgery. There are many variations in the arthroscopic knot-tying technique; however, the location of suture knot placement for rotator cuff healing has rarely been studied. Hypothesis: The authors compared the rotator cuff healing between knots tied on tendon and bone in a rotator cuff tear rat model. It has been hypothesized that knots can cause chronic inflammation and create the weakest link between tendon and bone, thus affecting rotator cuff healing. Study Design: Controlled laboratory study. Methods: Bilateral supraspinatus tenotomy and rotator cuff repair at the greater tuberosity were performed on 24 Wistar rats. Nonabsorbable surgical suture knots were made on the right supraspinatus tendon tissue and left humerus inferior to the greater tuberosity, respectively. Twelve rats each were sacrificed at 3 and 9 weeks. Six of the 12 rats were used for biomechanical testing and the remaining 6 for histologic evaluation. Results: The surgical knots placed on the bursal side of the tendon migrated to the articular side, as noted on gross observation in 22 of 24 samples. The knots on the tendon group showed significantly inferior tendon-bone integration and significantly inferior biomechanical results in terms of maximum load to failure and stiffness. An obvious chronic foreign body inflammatory reaction was found in the knots on the tendon group at 3 and 9 weeks. Furthermore, inferior bone-tendon interface regeneration and weakest link formation were obtained in the knots on the tendon group compared with those on the bone group. Conclusion: Nonabsorbable suture knots placed on the tendon migrate to the articular side, causing chronic inflammation and weakening tendon-bone healing, which may explain some retears after rotator cuff repair. Clinical Relevance: The present animal study suggests that it is not recommended in clinical practice to make several bulky nonabsorbable suture knots on the rotator cuff tendon during rotator cuff repair surgery. It may be better to tie the knots at the bone side or do knotless repair.

High-strength sutures allow tightening of a suture knot beyond the strength of the surgeon, possibly inflicting skin damage through the gloves. This study was undertaken to evaluate whether such effort is useful and how much tensioning on a surgical knot is necessary. Three different suture materials were tested: No. 2 Vicryl, FibreWire, and PDS. First, the force spontaneously applied on sutures during experimental knot tightening ("tying load") was measured in fifteen experienced surgeons. Second, with each suture material, surgical square knots were tied with increasing, standardized loads (range 0.5-50 N) using a custom-made apparatus. Thereby, knot seating after tying was evaluated, and by loading the knots to failure, evaluation for failure mode and failure load was performed. FibreWire 5-throw square knots always failed by complete slipping of all knots (resolving), independent on the tying load. A nonlinear decrease of knot slippage and increased failure load were seen with increasing tying loads for all sutures. Major differences were seen between 0.5 and 10 N for FibreWire (slippage: 25 mm) and PDS (99.6 mm), whereas Vicryl showed major differences (22.7 mm) between 0.5 and 2 N. Increasing the tying load from 10 to 50 N decreased the mean knot slippage from 12 (FibreWire, ±2.6 SD), 9 (PDS, ±1.8 SD) and 8 (Vicryl, ±1.3 SD) mm to 6 (±2.9 SD), 3 (±1.5 SD) and 4 mm (±0.9 SD), respectively. Slippage and self-seating of the knots under load is unavoidable even with highest tying loads. Relatively minor but possibly important differences can be seen for tying loads exceeding 2 N (Vicryl) and 10 N (PDS and FibreWire) for failure load and knot slippage. But also with a tying load of 50 N, a minimal slippage of approximately 3 mm seems unavoidable for all suture types. However, it is important to state that intense tightening does not prevent knot resolution and is only necessary in clinical situations that demand very tight sutures. Numbers and proper appliance of throws are more relevant than tying strength to reach the maximum failure load.

Development of mass transport resistance in poly(lactide-co-glycolide) films and particles – A mechanistic study

Background: The imperfection of surgical sutures, from the point of view of insufficient prevention of microbial contamination in the area of suturing, is one of the urgent problems in modern practical healthcare. In this connection, one of the promising areas at the present time is the study of suture material under conditions of its coating with various antiseptics. This study aimed to evaluate the physical and mechanical properties of the suture material impregnated with miramistin for further application in experimental studies on animals. Methods and Results: By applying a two-layer polymer coating on absorbable polyglycolide threads, the threads were given antimicrobial properties. In the amount of 10% or 20% by weight of the polymer, miramistin was introduced into both coatings. The breaking load and elongation data in the surgical suture knot were evaluated by immersing the samples in a phosphate buffer solution (pH=7.4), maintaining a constant temperature of 37°C by a thermostat. Threads from the solution were extracted on Days 1, 3, 7, 14, and 21 of the experiment. Further, the studied samples of the suture material were subjected to stretching to rupture on a universal tensile testing machine of the domestic company Metrotest. Physical and mechanical properties were evaluated by the dynamics of the breaking load and elongation at a break in the node after being in a phosphate buffer solution. Coating of polyglycolide thread, which is a suture material, with miramistin at a concentration of 10% and 20% does not lead to loss of strength even in the long term of the experimental study, which, in turn, meets the standards for suture material. Conclusion: The results obtained allow us to recommend a suture material impregnated with miramistin for further research, the ultimate goal of which will be the possibility of active use of this material in practical medicine, in particular in surgery to prevent microbial contamination in the area of suturing and infection of wounds.

Does speed equal quality? Time pressure impairs minimally invasive surgical skills in a prospective crossover trial

BackgroundThe absence of force feedback (FFB) is considered a technical limitation in robotic-assisted surgery (RAS). This pre-clinical study aims to evaluate the forces applied to tissues using a novel integrated FFB technology, which allows surgeons to sense forces exerted at the instrument tips.MethodsTwenty-eight surgeons with varying experience levels employed FFB instruments to perform three robotic-assisted surgical tasks, including retraction, dissection, and suturing, on inanimate or ex-vivo models, while the instrument sensors recorded and conveyed the applied forces to the surgeon hand controllers of the robotic system. Generalized Estimating Equations (GEE) models were used to analyze the mean and maximal forces applied during each task with the FFB sensor at the “Off” setting compared to the “High” sensitivity setting for retraction and to the “Low”, “Medium”, and “High” sensitivity settings for dissection and suturing. Sub-analysis was also performed on surgeon experience levels.ResultsThe use of FFB at any of the sensitivity settings resulted in a significant reduction in both the mean and maximal forces exerted on tissue during all three robotic-assisted surgical tasks (p < 0.0001). The maximal force exerted, potentially associated with tissue damage, was decreased by 36%, 41%, and 55% with the use of FFB at the “High” sensitivity setting while performing retraction, dissection, and interrupted suturing tasks, respectively. Further, the use of FFB resulted in substantial reductions in force variance during the performance of all three types of tasks. In general, reductions in mean and maximal forces were observed among surgeons at all experience levels. The degree of force reduction depends on the sensitivity setting selected and the types of surgical tasks evaluated.ConclusionsOur findings demonstrate that the utilization of FFB technology integrated in the robotic surgical system significantly reduced the forces exerted on tissue during the performance of surgical tasks at all surgeon experience levels. The reduction in the force applied and a consistency of force application achieved with FFB use, could result in decreases in tissue trauma and blood loss, potentially leading to better clinical outcomes in patients undergoing RAS. Future studies will be important to determine the impact of FFB instruments in a live clinical environment.

Biodegradable stents can alleviate intestinal obstruction and stenosis in patients. The objective of this study was to develop a biodegradable polydioxanone (PDO) stent using weft-knitting technology and then investigate its biodegradation behaviors in vitro. PDO monofilament with linear density of 100 ± 10 tex was knitted into a tubular stent using a tubular weft-knitting machine. The physical and mechanical properties were evaluated according to the British standard BS EN 13895:2003 and ISO 7198:1998. The biodegradation behaviors of PDO weft-knitted stent in a phosphate buffer solution (pH = 6.8 ± 0.2, 37 ± 0.5 °C) were then investigated. The results showed that the stent maintained more than 60% of its original radial force above 12 weeks. During the 16 weeks of degradation, weight, crystallization, and pH change indicated the degradation medium was diffused into the chain segments of low molecular weight due to the rupture of ester bonds in the monofilament. Fourier transform infrared spectroscopy results demonstrated that the chemical structure of PDO polymer is stable during the in vitro degradation. In conclusion, this biodegradable stent can find valuable applications in treatment of intestinal obstruction and stenosis clinically.

Factors relating to the volume of surgical knots

Background: Cardiac implantable electric device (CIED) implantation is a minor surgical procedure. One post-surgery complication often experienced is a suture knot projecting out of the skin 1-3 months after surgery. A unidirectional barbed suture (V-Loc; Covidien, Mansfield, MA) is a suture with barbs, which enables securing sutures without knots. The conventional sutures often leave a knot protruding at the suture line end; however, V-Loc eliminates the need to tie surgical knots and leaves a clean surface. Objective: We aimed to evaluate the safety and efficacy of V-Loc use in CIED implantation. Methods: A total of 153 patients underwent CIED implantation. Eighty-one patients were sutured using conventional string (PDS; Ethicon, Somerville, NJ) and V-Loc was used in 72 cases. A conventional method is to close a wound in three layers. After approximating the subcutaneous tissue in two layers with 3/0 PDS, the skin was closed with 4/0 PDS. Meanwhile, the new technique involves an over-and-over running stitch on the subcutaneous tissue with 3/0 V-Loc, followed by skin closure with 4/0 V-Loc. Results: The average suturing time was shorter in the V-Loc group than in the conventional group (9.9±1.7 vs. 18.0±4.1 mins. P&lt;0.01). This translated to a reduction in closure time by 45% (8.1 mins) without complications such as wound infection and dehiscence. In the conventional group, 16 of 81 patients (19.8%) had a suture knot projecting out without infection. Conclusion: V-loc suture material offers the possibility of a knotless stitch. We noted positive results in patients who were sutured with V-loc, and suggest its usefulness in CIED implantation.

Knot holding strength is essential to maintain wound closure and ensure tissue contact for healing. Knot unraveling can lead to severe complications, especially for high-tension closures such as tendon repairs, which have recently been reported to have knot unraveling rates as high as 86%. In the current study, a novel surgical knot, the two-strand-overhand locking (TSOL) knot, was designed and mechanically evaluated with use of different suture materials and knot configurations and in actual tendon repairs. The knot holding strength of the TSOL knot was compared with that of a 4-throw square knot with use of three different suture materials that are in common clinical use. With use of braided polyblend suture, the TSOL knot was also compared with five other surgical knot configurations. Finally, the strength of tendon repairs performed with use of the TSOL knot and a 4-throw square knot was studied. Compared with the 4-throw square knot, the holding strength of the TSOL knot was 143% greater for braided polyblend, 216% greater for polydioxanone, and 118% greater for polyester suture, with a significantly lower knot unraveling rate compared with that of the 4-throw square knot regardless of suture material. The TSOL knot holding strength was also greater than that of the other surgical knot configurations. The strength and stiffness of tendon repairs with a TSOL knot were significantly increased over those of repairs with a 4-throw square knot. The TSOL knot provided superior knot holding strength compared with some commonly used surgical knots. The TSOL knot has potential clinical applications, especially when knot security is important and high loads are expected, as in tendon or ligament repairs.

Surgical knots on the suture line provide an anchoring function, but also represent a potential source of infection and irritation on the donor leg after coronary artery bypass surgery. Knotless barbed sutures were designed to prevent knot-related complications. This study compared knot-related wound complication rates between patients receiving traditional monofilament sutures and those receiving barbed knotless sutures for closure of the donor leg. One hundred and forty-two patients were randomized into two groups. Group 1 (n = 70) received traditional monofilament sutures and Group 2 (n = 72) received barbed knotless sutures. All wounds were assessed on postoperative days 3 and 5 and weeks 2, 4 and 6 using a validated wound scoring system. Antibiotics usage and general practitioner and district nurse visits were recorded. No demographic differences were observed between groups. Leg wound skin closure times were significantly shorter in Group 2 compared with Group 1 (P < 0.001). Group 1 demonstrated a greater incidence of excessive scarring (P < 0.001), itching (P < 0.001), irritation (P < 0.001) and adverse skin tissue reactions (P < 0.001) than Group 2. Fewer general practitioner visits were recorded in Group 1 compared with Group 2 (P = 0.051). Knotless barbed suture usage significantly reduces the incidence of knot-related leg wound complications compared with traditional monofilament knotted sutures. This may be related to differences in the rate of absorption of the suture material or an associated decrease in the incidence of adverse skin tissue reactions that may delay postoperative wound healing.

The hydrolytic degradation of poly-L-lactide (PLLA) material was investigated in order to elucidate the effects of degradation on the morphology and molecular mass changes. The degradation mechanism and kinetics of PLLA were also studied. Molecular mass decreases and molecular weight distribution becomes broader continuously with an increase in the degradation time. After 20 weeks of degradation, there were a large number of diagonal striations on the surface and many erosive holes in the interior of the PLLA materials. The degradation mechanism of PLLA is indicative of an autocatalysis process and simple bulk hydrolysis at the same time, and the terminal hydroxyl group of the oligomer plays an important role. The degradation of PLLA complies with first-order kinetics, and the rate constant of the biodegradation process of PLLA is 9.2 × 10−3 day−1.

Star-shaped polymers of biodegradable aliphatic polyester, poly( ε-caprolactone), PCL, with different number of arms (three, four, and six) were synthesized by ring-opening polymerization initiated by multifunctional alcohols used as cores. As potential biomaterials, synthesized star-shaped poly( ε-caprolactone)s, sPCL, were thoroughly characterized in terms of their degradation under different pH conditions and in respect to their cytotoxicity. The in vitro degradation was performed in phosphate buffer (pH 7.4) and hydrochloric acid solution (pH 1.0) over 5 weeks. Degradation of sPCL films was followed by the weight loss measurements, GPC, FTIR, and AFM analysis. While the most of the samples were stable against the abiotic hydrolysis at pH 7.4 after 5 weeks of degradation, degradation was significantly accelerated in the acidic medium. Degradation rate of polymer films was affected by the polymer architecture and molecular weight. The molecular weight profiles during the degradation revealed random chain scission of the ester bonds indicating bulk degradation mechanism of hydrolysis at pH 7.4, while acidic hydrolysis proceeded through the bulk degradation associated with surface erosion, confirmed by AFM. The in vitro toxicity tests, cytotoxicity applying normal human fibroblasts (MRC5) and embryotoxicity assessment (using zebra fish model, Danio rerio), suggested those polymeric materials as suitable for biomedical application.

Purpose:It is hypothesized that a mesh reconstruction plate designed to fit a cochlear implant (CI) internal device will provide immediate structural support to the site of the implant and that this strength far exceeds the forces induced by a 1.5-tesla MRI. Procedures: Human calvarial specimens were drilled and plated with reconstruction mesh. Force was applied until failure was reached. Results: Mean maximum force, mean force to first failure and mean displacement measures for group 1 (resorbable mesh, n = 10) were 302.9 N, 283.0 N and 3.05 mm, respectively. The mean maximum force for group 2 (0.4-mm titanium mesh, n = 10) and group 3 (0.6-mm titanium mesh, n = 8), were 121.3 and 234.0 N, respectively. Mean force of first failure was 92.0 N for group 2 and 164.8 N for group 3. Conclusions: The force required for failure of the mesh is significantly greater than the 0.17 N exerted on a CI magnet by a 1.5-tesla MRI scan.

Optimum surgical suture material and methods to obtain high tensile strength at knots: problems of conventional knots and the reinforcement effect of adhesive agent