Poly(glycolide-co-caprolactone) (PGCL) has become a novice to the bioresorbable suture owing to the synergistic properties taken from the homo-polyglycolide (PGA) and polycaprolactone (PCL) such as excellent bioresorption and flexibility. In addition to under conventional monotonic loading, the understanding of mechanical responses of PGCL copolymers under complex loading conditions such as cyclic and stress relaxation is crucial for its application as a surgical suture. Consequently, the present work focuses on evaluating the mechanical responses of PGCL sutures under monotonic, cyclic, and stress relaxation loading conditions. Under monotonic loading, the stress-strain behavior of the PGCL suture was found to be non-linear with noticeable strain-rate dependence. Under cyclic loading, inelastic responses including stress-softening, hysteresis and permanent set were observed. During cyclic loading, both stress-softening and hysteresis were found to increase with the maximum strain. In multi-step stress relaxation, the PGCL sutures were observed to exhibit a strong viscoelastic response. In an attempt to describe the relationship between the stress-relaxation and strain-induced crystallization (SIC) occurring during the loading and relaxation processes, a schematic illustration of the conformational change of polymer chains in PGCL sutures was proposed in this work. Results showed that SIC was dependent on the strain level as well as the loading and relaxation durations. The inelastic phenomena observed in PGCL sutures can be thus correlated to the combined effect of stress relaxation and SIC.
Inguinal hernia remains the most commonly encountered surgical problem. Various methods of repair have been described, and the most suitable one debated. Single port access (SPA) surgery is a rapidly evolving field, and has the advantage of affording 'scarless' surgery. Single incision laparoscopic surgery (SILS) for inguinal hernia repair is seen to be feasible in both total extraperitoneal (TEP) and transabdominal pre-peritoneal (TAPP) approaches. Data and peri-operative information on both of these however are limited. We aimed to review the clinical experience, feasibility and short term complications related to laparoscopic inguinal hernia repair via single port access. A literature search was performed using Google Scholar, Springerlink Library, Highwire Press, Surgical Endoscopy Journal, World Journal of Surgery and Medscape. The following search terms were used: laparoscopic hernia repair, TAPP, TEP, single incision laparoscopic surgery (SILS). Fourteen articles in English language related to SILS inguinal hernia repair were identified. Nine articles were related to TEP repair and the remaining 5 to TAPP. A total of 340 patients were reported within these studies: 294 patients having a TEP repair and 46 a TAPP. Only two cases of recurrence were reported. Various ports have been utilized, including the SILS port, Tri-Port and a custom- made port using conventional laparoscopic instruments. The duration of surgery was 40-100 minutes and the average length of hospital stay was one day. Early outcomes of this novel technique show it to be feasible, safe and with potentially better cosmetic outcome.
Magnesium has been recognized as a groundbreaking biodegradable biomaterial for implant applications, but its use is limited because it degrades too quickly in physiological solutions. This paper describes the research on the influence of polycaprolactone (PCL)/chitosan (CS)/zinc oxide (ZnO) composite coating (PCL/CS/ZnO) on the corrosion resistance and antibacterial activity of magnesium. The PCL/CS film presented a porous structure with thickness of about 40-50 μm, while after incorporation of ZnO into the PCL/CS, a homogenous film without pores and defects was attained. The ZnO embedded in PCL/CS enhanced corrosion resistance by preventing corrosive ions diffusion in the magnesium substrate. The corrosion, antibacterial, and cell interaction mechanism of the PCL/CS/ZnO composite coating is discussed in this study. In vitro cell culture revealed that the PCL/CS coating with low loaded ZnO significantly improved cytocompatibility, but coatings with high loaded ZnO were able to induce some cytotoxicity osteoblastic cells. It was also found that enhanced antibacterial activity of the PCL/CS/ZnO coating against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, while less significant antibacterial activity was detected for uncoated Mg and PCL/CS coating. Based on the results, the PCL/CS coatings loaded with low ZnO content may be recommended as a candidate material for biodegradable Mg-based orthopedic implant applications.
The recent proposal of using Zn-based alloys for biodegradable implants was not supported with sufficient toxicity data. This work, for the first time, presents a thorough cytotoxicity evaluation of Zn-3Mg alloy for biodegradable bone implants. Normal human osteoblast cells were exposed to the alloy's extract and three main cell-material interaction parameters: cell health, functionality and inflammatory response, were evaluated. Results showed that at the concentration of 0.75mg/ml alloy extract, cell viability was reduced by ~50% through an induction of apoptosis at day 1; however, cells were able to recover at days 3 and 7. Cytoskeletal changes were observed but without any significant DNA damage. The downregulation of alkaline phosphatase protein levels did not significantly affect the mineralization process of the cells. Significant differences of cyclooxygenase-2 and prostaglandin E2 inflammatory biomarkers were noticed, but not interleukin 1-beta, indicating that the cells underwent a healing process after exposure to the alloy. Detailed analysis on the cell-material interaction is further discussed in this paper.
Biodegradable metals such as magnesium, iron and their alloys have been known as potential materials for temporary medical implants. However, most of the studies on biodegradable metals have been focusing on optimizing their mechanical properties and degradation behavior with no emphasis on improving their bioactivity behavior. We therefore investigated the possibility of improving iron biodegradation rate and bioactivity by incorporating various bioactive bioceramics. The iron-based bioceramic (hydroxyapatite, tricalcium phosphate and biphasic calcium phosphate) composites were prepared by mechanical mixing and sintering process. Degradation studies indicated that the addition of bioceramics lowered the corrosion potential of the composites and slightly increased their corrosion rate compared to that of pure iron. In vitro cytotoxicity results showed an increase of cellular activity when rat smooth muscle cells interacted with the degrading composites compared to pure iron. X-ray radiogram analysis showed a consistent degradation progress with that found in vivo and positive tissue response up to 70 days implantation in sheep animal model. Therefore, the iron-based bioceramic composites have the potential to be used for biodegradable bone implant applications.
Bones are nanocomposites consisting of a collagenous fibre network, embedded with calcium phosphates mainly hydroxyapatite (HA) nanocrystallites. As bones are subjected to continuous loading and unloading process every day, they often tend to become prone to fatigue and breakdown. Therefore, this review addresses the use of nanocomposites particularly polymers reinforced with nanoceramics that can be used as load bearing bone implants. Further, nanocomposite preparation and dispersion modification techniques have been highlighted along with thorough discussion on the influence that various nanofillers have on the physico-mechanical properties of nanocomposites in relation to that of natural bone properties. This review updates the nanocomposites that meet the physico-mechanical properties (strength and elasticity) as well as biocompatibility requirement of a load bearing bone implant and also attempts to highlight the gaps in the reported studies to address the fatigue and creep properties of the nanocomposites.
In this work, binary Zn-0.5Al and ternary Zn-0.5Al-xMg alloys with various Mg contents were investigated as biodegradable materials for implant applications. Compared with Zn-0.5Al (single phase), Zn-0.5Al-xMg alloys consisted of the α-Zn and Mg2(Zn, Al)11 with a fine lamellar structure. The results also revealed that ternary Zn-Al-Mg alloys presented higher micro-hardness value, tensile strength and corrosion resistance compared to the binary Zn-Al alloy. In addition, the tensile strength and corrosion resistance increased with increasing the Mg content in ternary alloys. The immersion tests also indicated that the corrosion rates in the following order Zn-0.5Al-0.5Mg
Stent designs with ultrathin struts may further increase the procedural success of challenging lesion subsets. The objective of this study was to assess the safety and efficacy of ultrathin strut, polymer-free sirolimus eluting stent (PF-SES) implantations in a large scale, unselected patient population.Adult patients underwent percutaneous coronary interventions (PCI) with a thin-strut PF-SES. Data from two all-comers observational studies having the same protocol (ClinicalTrials.gov Identifiers: NCT02629575 and NCT02905214) were pooled. The accumulated target lesion revascularization (TLR) rate at 9-12 months was the primary endpoint. All dual antiplatelet therapy strategies according to the applicable guidelines were permissible.In total, 7243 patients were prospectively enrolled for PCI with PF-SES in stable coronary artery disease or acute coronary syndrome (ACS). Major risk factors in the overall cohort were diabetes (37.3%), ST elevation myocardial infarction (18.1%) and non-ST myocardial infarction (24.6%). The follow-up rate was 88.6% in the overall population. The TLR rate in the overall cohort was 2.2% whereas definite/probable stent thrombosis (ST) occurred in 0.7%. In patients with in-stent restenosis lesions, the major adverse cardiac events rate was 6.4% whereas the corresponding rate for isolated left main coronary artery (LMCA) disease was highest with 6.7% followed by patients with culprit lesions in vein bypasses (VB, 7.1%). The mortality rate in patients treated in VB lesions was highest with 5.4%, followed by the isolated LMCA subgroup (3.4%) and ACS (2.6%).PCI with PF-SES in an unselected patient population, is associated with low clinical event and ST rates. Furthermore, PF-SES angioplasty in niche indications demonstrated favorable safety and efficacy outcomes with high procedural success rates.
This article reports the in vitro degradation and cytotoxicity assessment of Zn-3Mg alloy developed for biodegradable bone implants. The alloy was prepared using casting, and its microstructure was composed of Mg2Zn11 intermetallic phase distributed within a Zn-rich matrix. The degradation assessment was done using potentiodynamic polarization and electrochemical impedance spectrometry. The cell viability and the function of normal human osteoblast cells were assessed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and alkaline phosphatase extracellular enzyme activity assays. The results showed that the degradation rate of the alloy was slower than those of pure Zn and pure Mg due to the formation of a high polarization resistance oxide film. The alloy was cytocompatible with the normal human osteoblast cells at low concentrations (<0.5 mg/mL), and its alkaline phosphatase activity was superior to pure Mg. This assessment suggests that Zn-3Mg alloy has the potential to be developed as a material for biodegradable bone implants, but the toxicity limit must be carefully observed.
Valved allografts and xenografts for reconstruction of the right ventricular outflow tract (RVOT) lack durability and do not grow. We report the first clinical use of a completely bioabsorbable valved conduit (Xeltis pulmonary valve - XPV) in children. Twelve children (six male), median age five (two to twelve) years and median weight 17 (10 to 43) kg, underwent RVOT reconstruction with the XPV. Diagnoses were: pulmonary atresia with ventricular septal defect (VSD) (n=4), tetralogy of Fallot (n=4), common arterial trunk (n=3), and transposition of the great arteries with VSD and pulmonary stenosis (n=1). All had had previous surgery, including prior RVOT conduit implantation in six. Two diameters of conduit 16mm (n=5) and 18mm (n=7) were used. At 24 months none of the patients has required surgical re-intervention, 9 of the 12 are in NYHA functional class I and three patients in NYHA class II. None of the conduits has shown evidence of progressive stenosis, dilation or aneurysm formation. Residual peak gradient of >40 mm Hg was observed in three patients, caused by kinking of the conduit at implantation in 1 and distal stenosis in the peripheral pulmonary arteries in 2 patients. Five patients developed severe pulmonary valve insufficiency (PI); the most common mechanism was prolapse of at least one of the valve leaflets. The XPV conduit is a promising innovation for RVOT reconstruction. Progressive PI requires however an improved design (geometry, thickness) of the valve leaflets.
The purpose of this study was to evaluate the early functional outcome following the use of a bioabsorbable suture anchor to simplify the repair of injured lateral ankle structures as a variation of an established technique known as the Brostrom-Gould procedure.
Older patients who undergo coronary interventions are at greater risk of ischemic events and less likely to tolerate prolonged dual antiplatelet therapy (DAPT) due to bleeding risk. The COMBO biodegradable polymer sirolimus-eluting stent promotes rapid endothelialization through endothelial progenitor cell capture technology which may be advantageous in elderly patients. We compared 1-year clinical outcomes and DAPT cessation events in patients >75 versus ≤75 years from the MASCOT registry. MASCOT was a prospective, multicenter cohort study of all-comers undergoing attempted COMBO stenting. The primary endpoint was 1-year target lesion failure (TLF), composite of cardiac death, myocardial infarction (MI) not clearly attributed to a nontarget vessel or clinically driven target lesion revascularization. Bleeding was adjudicated using the Bleeding Academic Research Consortium criteria. Adjusted outcomes were analyzed using Cox regression methods. The study included 18% (n = 479) patients >75 years and 72% (n = 2,135) patients ≤75 years. One-year TLF occurred in 4.6% patients >75 years versus 3.1% patients ≤75years of age, p = 0.10; adj hazard ratio 1.36, 95% confidence intervals 0.77 to 2.38, p = 0.29. There were no significant differences in cardiac death (1.7% vs 1.3%, p = 0.55), MI (2.1% vs 1.2%, p = 0.14), target lesion revascularization (1.7% vs 1.4%, p = 0.60) and definite stent thrombosis (0.8% vs 0.4%, p = 0.19). Major Bleeding Academic Research Consortium 3,5 bleeding (3.1% vs 1.5%, p = 0.01) and DAPT cessation rates (32.4% vs 23.0%, p <0.001) were significantly higher in elderly patients. In conclusion, elderly patients >75 years treated with COMBO stents had similar TLF but significantly greater incidence of bleeding than younger patients and DAPT cessation in one-third of patients over 1 year.
This study compares the midterm results of mitral valve repair using the biodegradable ring versus repair with non-ring annuloplasty techniques for congenital mitral valve disease in young children where it was not possible to use standard commercial rings.
The study was carried out to evaluate macroscopically the ability of coral to repair a large size bone defect. A total 12 adult, male sheep were used in the study. The large bone defect (2.5cm x 0.5cm x 0.5cm) was created surgically on the left proximal femur and replaced by a block of coral (Porites sp.). Radiographs were obtained immediately after surgery and at 2, 4, 8 and 12 weeks post-implantation. Ultrasonographic examinations were carried out every 2 weeks after implantation up to 12 weeks using ultrasound machine (TOSHIBA Capasee II) connected with 7MHz frequency transducer. The sheep were euthanased at 2, 4, 8, and 12 weeks post-implantation and the bone examined grossly. Both ultrasonographs and radiographs taken at 8 and 12 weeks showed that the implants had been resorbed and left the space that much reduced in size. There was no sign of implant rejection observed in all animals. The results showed that processed coral has potential to become bone substitute for reconstructive bone surgery.
This in vivo study revealed that porous hydroxyapatite (PHA) and dense hydroxyapatite (DHA) are good implant materials that can accelerate bone healing and resorbed in acceptable time. But there were differences in the mechanism of the resorption of DHA and PHA due to variability in the physical properties and osteogenicity.
The study was carried out with the aim to evaluate natural coral (Porites spp.) implanted in sheep femur microscopically. Twelve adult, male sheep were used in this study. The defect area was implanted with coral and monitored for up to 12 weeks. The sheep were euthanased at 2,4,8, and 12 weeks post-implantation. Microscopically, natural coral implanted into bone tissue have shown gradual resorption and progressively replaced by new bone. At 12 weeks post-implantation, the implanted site was almost completely surrounded by mature bone. The results showed that natural coral was found to be a biodegradable and osteo-conductive biomaterial, which acted as a scaffold for a direct osteoblastic apposition.
The main objective of the study was to determine the biodegradability, resorption and osteoconductivity potency of coral implant. Coral blocks (CORAGRAF) were prepared from sea coral Porites species. The blocks were implanted in the right mandible of rabbit model. Implants were harvested at 2 and 4 weeks intervals and subjected for light and scanning electron microscopy. Dense hydroxyapatite (DHA) was implanted in the left mandible as a control. The results of this study demonstrated that CORAGRAF is a good implant material that can accelerates bone healing and be resorbed in an acceptable time. The mechanisms of the resorption seemed to be the same (crumbling process), a first step where the edge of the coral become powdery then a second step which could be phagocytosis and dissolution in extracellular fluid.