Bioabsorbable Materials Research Articles

Influence of Annealing and Biaxial Expansion on the Properties of Poly(l-Lactic Acid) Medical Tubing.

Poly-l-lactic acid (PLLA) is one of the most common bioabsorbable materials in the medical device field. However, its use in load-bearing applications is limited due to its inferior mechanical properties when compared to many of the competing metal-based permanent and bioabsorbable materials. The objective of this study was to directly compare the influence of both annealing and biaxial expansion processes to improve the material properties of PLLA. Results showed that both annealing and biaxial expansion led to an overall increase in crystallinity and that the crystallites formed during both processes were in the α’ and α forms. 2D-WAXS patterns showed that the preferred orientation of crystallites formed during annealing was parallel to the circumferential direction. While biaxial expansion resulted in orientation in both axial and circumferential directions, with relatively equal sized crystals in both directions, Da (112 Å) and Dc (97 Å). The expansion process had the most profound effect on mechanical performance, with a 65% increase in Young’s modulus, a 45% increase in maximum tensile stress and an 18-fold increase in strain at maximum load. These results indicate that biaxially expanding PLLA at a temperature above Tcc is possible, due to the high strain rates associated with stretch blow moulding.

Development of biocompatible and fully bioabsorbable PLA/Mg films for tissue regeneration applications

During recent years, Mg reinforced polylactic acid (PLA) composites have emerged as potential biocompatible and bioabsorbable materials for biomedical applications. It has been shown that Mg particles added to a matrix based on a biodegradable polymer can address the lack of bioactivity and the low mechanical properties of the polymers and, furthermore, it can counteract the detrimental effects associated to the high degradation rate of Mg, as alkalinization and elevated H2 release. Additionally, the polymer can protect the Mg particles, by tailoring their degradation rate. Former processing of these composites performed by extrusion, compression and injection molding employed Mg contents up to 10 wt%. Higher amounts of Mg resulted in heterogeneous materials and thermally degraded matrices, with the corresponding higher degradation rate. In the present work, Mg reinforced PLA films with Mg content as high as 50 wt% were obtained without compromising the thermal stability of the polymer. Firstly, a successful dispersion of Mg microparticles was achieved by a breakthrough in processing introducing a colloidal step where organic additives were added to modify the Mg particle surface and promote a chemically stable suspension. The resulting colloidal suspension was then used as feedstock to obtain composite films by tape casting. The films show advantageous in vitro behaviour in terms of degradation, hydrogen release and oxygen permeability. In addition, the viability with fibroblast cells (MEF) opens a window of opportunity for these composite films as bioabsorbable material for tissue engineering and wound dressing applications. Statement of SignificanceMagnesium materials have extraordinary biodegradable properties and bioactive behavior due to release of Mg2+ ions, which offer a promising opportunity for their applicability as biomaterials for tissue regeneration. However, Mg is one of the most reactive metals with a high degradation rate. In contact with water produces H2, associated with a risk of failure of the implant. One alternative to minimize this drawback is the use of Mg particles surrounded by a biodegradable biocompatible polymer such as polylactic acid (PLA) to obtain PLA/Mg composites. In this work we processed Mg reinforced PLA in the shape of films that would be suitable for tissue regeneration. In vitro behavior of PLA/Mg films demonstrated that Mg2+ ions increase the fibroblast cells growth.

Forty years of the Japanese Society for Biomaterials looking back at my term of office as the chairperson.

The compatibility of artificial materials with living system, such as antithrombogenicity and antiimmunogenicity, has been an important issue in the field of the biomaterials researches at the early periods of the biomaterials research. After that, the bioabsorbable materials have been subsequently incorporated as biomaterials. As a result, biomaterial researchers started participating in the field of drug delivery system (DDS), and combining biomaterials and cells not only led to bioartificial organs, but also tissue engineering. The bioabsorbable biomaterials function as scaffolds for the cells and play an important role in the field of regenerative medicine researches. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 930-932, 2019.

Pathology of Bioabsorbable Implants in Preclinical Studies.

Bioabsorbable implants can be advantageous for certain surgical tissue bioengineering applications and implant-assisted tissue repair. They offer the obvious benefits of nonpermanence and eventual restoration of the native tissue's biomechanical and immunological properties, while providing a structural scaffold for healing and a route for additional therapies (i.e., drug elution). They present unique developmental, imaging, and histopathological challenges in the conduct of preclinical animal studies and in interpretation of pathology data. The bioabsorption process is typically associated with a gradual decline (over months to years) in structural strength and integrity and may also be associated with cellular responses such as phagocytosis that may confound interpretation of efficacy and safety end points. Additionally, as these implants bioabsorb, they become increasingly difficult to isolate histologically and thus imaging modalities such as microCT become very valuable to determine the original location of the implants and to assess the remodeling response in tandem with histopathology. In this article, we will review different types of bioabsorbable implants and commonly used bioabsorbable materials; additionally, we will address some of the most common challenges and pitfalls confronting histologists and pathologists in collecting, handling, imaging, preparing tissues through histology, evaluating, and interpreting study data associated with bioabsorbable implants.

Is bio absorbable screw really reliable for midcarpal arthrodesis? A literature review through a case report

Bio absorbable materials have been used for a long time in human surgery. Application in various surgical fields as hand, foot, knee and spine surgery were developed. Among the numerous uses in hand surgery, wrist arthrodesis with those materials has rarely been studied. Should we use bio absorbable screw for midcarpal arthrodesis? We reviewed the literature about wrist arthrodesis with absorbable devices and shared our experience with a case of a midcarpal arthrodesis failure with magnesium and zinc alloy screws. From our review, we found that very few articles about that particular subject were published and amongst them very few had good results regarding wrist arthrodesis. Complications were construct failure and led to reintervention. Thus, this subject should be investigated biomechanically and clinically. According to our research and experience, bio absorbable screws should be avoided for midcarpal arthrodesis.

Zastosowanie śrub biowchłanialnych w porównaniu ze śrubami metalowymi w truamatologii dziecięcej

ABSTRACTIntroduction: Metal stabilizing implants used in pediatric fractures have to be removed to not inhibit the growth of bones. Bioabsorbable implants can save children from surgical removal of the fixating material. As there have been only a few reports regarding children, we decided to evaluate the clinical advantages of bioabsorbable screws in the treatment of selected bone fractures in pediatric traumatology.Materials and methods: The study group included 35 patients with bone fractures aged 5–17 years (mean 13.2 years) fixed with LactoSorb® bioabsorbable screws made of polymeric lactic acid and polyglycolic acid. The follow-up was compared with a matched control group of 35 children that underwent operative fixation of the same type of fractures with metal screws. Results: Clinical and radiological follow-up showed that bone unions were obtained in all cases, with no signs of osteolysis. The time of immobilization was slightly shorter in the study group (5.5 weeks) than among controls (6.2 weeks; p = 0.038). There were no differences in complications, wound infections, pain management and time of hospitalization between both groups.Conclusions: The use of bioabsorbable material in the treatment of fractures in pediatric traumatology is a safe alternative to metal stabilizing devices, with clinical benefits for young patients including no necessity of a second surgery and anesthesia.

A numerical study on the application of the functionally graded bioabsorbable materials in the stent design

BackgroundAngioplasty with stenting is one of the primary treatment for coronary artery disease, hence, performance of the stent is deemed important. Bioabsorbable stents are the new generation of stents. Bioabsorbable magnesium alloys are a promising solution for adverse effects of long-term usage of stents. While their corrosion mechanics and biocompatibility have extensively been studied, there are no studies on application of functionally graded materials (FGM) on reduction of dogboning in bioabsorbable stents. MethodsThe objective of this study was at reducing the dogboning via the application of the FGM. A combination of the finite element (FE) method and optimization algorithm were employed to analyse/optimize the mechanical behaviour of bioabsorbable stents. Proposed FGM, in this study, was a combination of AZ80 and WE43 magnesium alloys. Dogboning of the FGM stent was chosen as objective function to be minimized and heterogeneous index was chosen as control variable in the optimization algorithm. ResultsThe results revealed that the optimum FGM stent with heterogeneous index of 1.4625 has lower dogboning (63%) compared to that of the uniform stents made of AZ89 or WE43 magnesium alloy. ConclusionsFurthermore, the results suggested that the plastic material properties have higher impact on the mechanical behaviour of the stent in comparison to the elastic material properties.

Friday, September 28, 2018 1:00 PM–2:30 PM abstracts: achieving lumbar interbody fusion: 192. Clinical evaluation of a new allograft cage designed for TLIF: a minimal 1-year follow-up

BACKGROUND CONTEXT Currently most cages are made of metal, carbon fiber, polyether ether ketone (PEEK), and bio-absorbable materials. But there are some drawbacks of these materials in terms of biology, biomechanics, etc., mainly in terms of the elastic modulus is too large, poor biocompatibility, and unable to absorb. Allogeneic bone is recognized bone graft material of great osteogenic effect. It has the closest physicochemical properties, structure and activity of protein-based composition of autologous bone. It in rich in a variety of cytokines required for osteogenesis: bone morphogenetic protein-2, vascular endothelial growth factor, core binding factor α1, et. PURPOSE The purpose of this study was to observe the preliminary clinical results of the new allograft cage. STUDY DESIGN/SETTING A retrospective research. PATIENT SAMPLE A total of 152 patients. OUTCOME MEASURES Visual Analogue Scale (VAS) and The Oswestry Disability Index (ODI);Relative intervertebral disc height (RIDH); fusion rate. METHODS From 2012 to 2015, a retrospective review of the first 152 consecutive cases using the new allograft cage in our department was performed. The follow-up ranged from 12 to 36 months (average 18 months). Intraoperative index, clinical outcome and complications were recorded. Radiographs evaluatedrelative intervertebral disc height (RIDH) and fusion rate. RESULTS Between September 2012 and November 2014, total 152 patients surgery using the new allograft cage in our department. A total of 133 c (87.6%) met the inclusion criteria and exclusion criteria. There are 78 males and 55 females. The average follow-up time is 15.2±5.3 months. The main diagnosis are lumbar disc herniation (68/133), Lumbar spinal stenosis (44/133), SpondyloliSthesis (21/133). There are 99 one segments fusion and 33 two segments fusion. Respectively, the average blood loss and operation time is 335.7±214.2ml and 175.2±40.9 minutes in single segments fusion, and 488.3±173.2ml, 335.7±214.2 minutes in double segments fusion. The VAS score decreased significantly from 6.89 ±2.51 preoperatively to 2.72±0.97 in 3 months postoperation. At final follow up, the VAS score is 2.96 ±1.02. There was also a significant improvement of the ODI from 38.3±15.9preoperatively to 14.6±6.3 in 3 months postoperation (P CONCLUSIONS It has the potential ability in promoting fusion rate in relative short time (approximately 6 months) postoperatively. We consider it have good clinical outcomes. However, it is just the preliminary data with a short-term follow up. Long-term follow-up is still needed proved.

Hemocompatibility of plasma electrolytic oxidation (PEO) coated Mg-RE and Mg-Zn-Ca alloys for vascular scaffold applications

Percutaneous transluminal coronary angioplasty and subsequent vascular scaffold implantation remains the prevalent invasive treatment of coronary heart disease. In-stent restenosis remained a problem with bare metal stents, until drug-eluting stents were introduced. The inhibition of the healing process by the antimitotic drug coating and the permanent metallic remnant can promote sub-acute and delayed stent thrombosis. Thus, the development of biodegradable stents emerged as a subject of research. Magnesium-based bioabsorbable devices can provide sufficient radial force in the acute phase of vessel-treatment and degrade thoroughly in aqueous environment, making them potential new candidates for vascular scaffold applications. Magnesium alloys tend to degrade very quickly due to their high electrochemical corrosion potential. Plasma Electrolytic Oxidation modification of magnesium alloys improves interface and degradadation properties and may therefore enhance the performance and suitability for vascular scaffold applications of these materials. Assuring the hemocompatibility and foremost assessing the thrombogenicity of new biomaterials prior to their use is essential in order to avoid adverse effects. The goal was to assess thrombocyte adhesion on coated Mg-RE and Mg-Zn-Ca alloys. Static experiments with human blood were carried out on the plasma-electrolytically treated or corresponding untreated Mg alloy in order to assess quantity and quality of thrombocyte adhesion via standardized SEM imaging. In a second step, a parallel plate flow chamber was designed in order to examine thrombocyte adhesion under dynamic flow conditions. During flow chamber experiments the test-materials were exposed to human thrombocyte concentrate and the number of adherent thrombocytes was assessed. The flow chamber was additionally perfused with human blood and thrombocyte adhesion was semiquantitatively and qualitatively assessed via SEM imaging and subsequent scoring. In conclusion, a new parallel plate flow chamber design simulating blood-circulation was successfully established, enabling the further assessment of platelet adhesion on bioabsorbable materials under dynamic flow conditions. Static and dynamic experiments showed, that plasma-electrolytically treated specimens showed low thrombocyte adhesion on both alloys, proposing their potential use in vascular scaffolds. The uncoated magnesium alloys showed rapid degradation along with gas formation due to the chemically active surface and therefore give concern regarding their safety and suitability for vascular applications.

Progress in bioabsorbable screws used in treatment of injury to distal tibiofibular syndesmosis

As injury to distal tibiofibular syndesmosis is commonly associated with ankle fractures, it calls for timely and correct diagnosis and treatment because it might result in chronic pain and ankle instability. Its severe cases can lead to traumatic arthritis. Stable injury to distal tibiofibular syndesmosis can be treated conservatively, but internal fixation is mostly recommended for severe cases of the injury. Internal fixation with metal screws usually requires a secondary surgery for removal of the implants but application of bioabsorbable screws overcomes this trouble and avoids a secondary surgery and its related complications. This article reviews the advantages of bio-absorbable screws, choice of bioabsorbable materials and screws, therapeutic outcomes and adverse reactions in the treatment of distal tibiofibular syndesmotic injury. Key words: Ankle; Bone screws; Fracture fixation, internal; Distal tibiofibular

Short-Term Prospective Clinical Evaluation of a Polyglycolic Acid Tibial Tuberosity Advancement Cage Implant.

This study investigated the short-term radiographic healing of the osteotomy following tibial tuberosity advancement (TTA), maintenance of patellar tendon angle (PTA), and complications in dogs receiving a polyglycolic acid (PGA) TTA cage. Patients diagnosed with unilateral cranial cruciate ligament disease requiring a 9- or 12-mm TTA cage were included. Twenty-six consecutive client-owned dogs were prospectively selected for this clinical study. Age, weight, sex, breed, cage size, surgery date, and follow-up time were recorded. Radiographs were scored for healing and measured for PTA immediately, at 6 wk, and at 10 wk postoperatively. All stifles were assessed for complications throughout the study period. Stifles with PGA cages had similar overall healing scores compared to previously reported values for metallic cages, and the PTA was well maintained at 6 and 10 wk postoperatively. Polyglycolic acid cages were associated with a higher complication rate (10/26, 38%; 95% confidence interval, 0.19-0.61) compared with previously reported complication rates for metallic cages. Despite favorable healing scores and overall PTA maintenance, PGA cage use resulted in a high complication rate. Proposed advantages offered by this particular implant over currently used metallic cages are offset by this high complication rate. Additional investigation of bioabsorbable materials and implant design should be considered.

Effective Repair of Dural Tear Using Bioabsorbable Sheet With Fibrin Glue.

Basic science. This study aimed to compare the techniques of surgical repair of dural tear using bioabsorbable material and fibrin glue. Cerebrospinal fluid (CSF) leakage caused by dural tear can often be difficult to manage even after repair when the same materials are used in a similar manner. Burst pressure was measured for repaired porcine dura with holes of different diameters using spray of combined fibrinogen and thrombin solution (fibrin spray) alone as a control and the 5-mm hole following different methods using fibrinogen and thrombin solutions plus polyglactin 910 sheet (PGS). For group 1, fibrinogen was applied on the dura followed by PGS and thrombin. For group 2, thrombin was followed by PGS and fibrinogen. For group 3, fibrinogen was followed by PGS and fibrin spray. For group 4, thrombin was followed by PGS and fibrin spray. Microscopic observation was conducted for each specimen. Repair using fibrin spray alone was successful for the 0.3-mm diameter pinhole (breakdown pressure: 27.8 ± 8.6 mmHg), but was not able to cover the 2.7- and 5-mm holes. For a 5-mm diameter hole, the breakdown pressure was 54.4 ± 38.8 mmHg in group 1, 26.3 ± 19.4 mmHg in group 2, 147.7 ± 65.0 mmHg in group 3, and 35.5 ± 23.4 mmHg in group 4 (P < 0.001). There was little fibrin glue in the burst layer between the dural surface and PGS with thrombin on the dural surface (group 2 and group 4). Suppression of excessive CSF leakage could be successful by performing several cycles of the group 1 method (fibrinogen was applied on the dura followed by PGS and thrombin), followed by the group 3 method (fibrinogen was applied on the dura followed by PGS and fibrin spray), with thrombin solution wash each time. 4.

Bioabsorbable Anchors for Medial Patellofemoral Ligament Reconstruction

Acute dislocation of the patella is a very common injury of the knee. In more than 90% of the cases the medial patellofemoral ligament (MPFL) is injured. Reconstruction of the MPFL has become a popular soft tissue procedure, which reduces hospitalization and the rehabilitation period. Bioabsorbable materials, in form of screws and anchors are ideal for soft fixation to bones in orthopedics. We would like to present our experience and short-term results after MPFL reconstruction with semitendinous autograft and bioabsorbable fixation devices. 10 patients were involved in this study with PF joint instability, who underwent to MPFL reconstruction. In order to evaluate the functional outcome of the procedure we applied the Tegner Lysholm scoring system before and after 3 Months of surgery. MPFL reconstruction significantly improved the functionality of the PF joint. Gender distribution of the studied group was: 7 female with an average age of 25 5,03 SD and 3 male patients with an average age of 29 1 SD. The key for the success in MPFL reconstruction is the positioning of the femoral tunnel, followed by an isometric tensioning of the graft. Bioabsorbable materials reduce inflammatory, and foreign body response facilitating biointegration of the autograft.

Multicenter single-arm, prospective study of reinforced stapler with bioabsorbable materials to prevent pancreatic fistula after distal pancreatectomy

Multicenter single-arm, prospective study of reinforced stapler with bioabsorbable materials to prevent pancreatic fistula after distal pancreatectomy

Coupled ductile–hydrolytic damage model based on variational constitutive updates

This work presents a constitutive model suitable for the description of materials showing elastic–viscoplastic behavior and coupled ductile–hydrolytic damage. Such behavior is frequently observed in bioabsorbable materials that have been increasingly used in the development of medical implants (surgical sutures, screws, plates, anchors, stents, etc.). An approach for describing this coupling between mechanical and hydrolytic damage is the core and main contribution of the current proposal. The model is embedded within a variational framework in such a way that the update of internal variables is driven by a minimization principle. A complete description of the model is presented as well as operational details related to an incremental algorithm suitable for finite element calculations. Despite the complexity of the phenomena involved in the formulation, it is shown that the update algorithm follows a simple operational scheme. Several numerical tests were carried out at a material point level, showing the model capability to handle coupling effects of ductile and chemical (hydrolytic) damage. Furthermore, some implications related to the dependence of dissipation functions on state variables, mainly those dependent on the elastic state, were analyzed demonstrating the possible consequences on the solution of damage and stress. The material model was successfully implemented in an in-house code and a commercial code, where examples of application on 3D devices were run bringing insight into realistic applications of the proposed model.

Synthesis, properties and biomedical applications of hydrolytically degradable materials based on aliphatic polyesters and polycarbonates.

Polyester-based polymers represent excellent candidates in synthetic biodegradable and bioabsorbable materials for medical applications owing to their tailorable properties. The use of synthetic polyesters as biomaterials offers a unique control of morphology, mechanical properties and degradation profile through monomer selection, polymer composition (i.e. copolymer vs. homopolymer, stereocomplexation etc.) and molecular weight. Within this review, the synthetic routes, degradation modes and application of aliphatic polyester- and polycarbonate-based biomaterials are discussed.

A novel method of using bioabsorbable materials for the surgical repair of flail chest.

A novel method of using bioabsorbable materials for the surgical repair of flail chest.

Complications Related to Pectus Carinatum Correction: Lessons Learned from 15 Years' Experience. Management and Literature Review.

Various methods of corrective thoracoplasty for pectus carinatum deformity have been described, but to date no studies describe a review of complications and how to manage them. Complications are dependent not only on the technique used and the patient's age, but also on the experience of the treating surgeon. The authors present their 15 years' experience with surgical correction of pectus carinatum and the complications that have occurred. A literature review regarding complications with pectus carinatum surgery is performed. A retrospective review of 95 patients (mean age, 19 years) was performed. One hundred four surgical procedures for repair of pectus carinatum were performed from July of 2000 to July of 2015 using a modified Ravitch technique, bioabsorbable material, postoperative bracing, and in some cases a diced rib cartilage graft technique. Intraoperative and postoperative complications were evaluated. The mean patient follow-up was 13.6 months (range, 4 months to 9.75 years). Intraoperative complications were pleura lesion and laceration of the internal mammary vein. Postoperative complications were recurrent mild protrusion, persistent protrusion of one or two costal cartilages, minor wound healing delay, skin ulcer, hypertrophic scar, transient intercostal dysesthesia, marginal pneumothorax, seroma, meningitis, and epidural hematoma. In our reported series of pectus carinatum repair, increasing experience and progressively less extensive techniques have resulted in fewer complications, low morbidity, and early return to activity. Complications were observed in the early period of application, predominantly because of a lack of experience, and usually subsided with increasing numbers of patients and frequency of surgery. Therapeutic, IV.

Correct techniques for the use of bioabsorbable implants in orthopaedic trauma

Since the mid 1980s, the materials and designs of bioabsorbable screws and rods have improved with better biocompatibility, absorbability, and biomechanics, thus reducing the rate of complications. This article describes the differences in the placement of bioabsorbable materials and conventional materials and how the differences affect applicability in orthopaedic procedures. Bioabsorbable screws and pins can be used for different types of fractures. However, when used it is important to consider the differences between bioabsorbable and conventional materials during the surgical technique. When using bioabsorbable materials, the following must be considered: the bone surface should be fully seen, even cannulated screws; the entire length of the pilot hole requires drilling or tapping; screws and rods are nonreversible; drilling of bioabsorbable materials is possible, if required; screws or rods, if long or prominent, can be cut or shaped to avoid skin complications; bioabsorbable implants cannot be seen on radiography (a drill bit or Kirschner wire must be used to assure that the final position of the screw or rod will be correct); and there are no self-adjustment properties when bioabsorbable screws or rods are inserted. Conventional materials and bioabsorbable materials require different insertion strategies. Recognizing these differences will help in the application of bioabsorbable implants and decrease the rate of complications.

Enhanced Anti-corrosion Ability and Biocompatibility of PLGA Coatings on MgZnYNd Alloy by BTSE-APTES Pre-treatment for Cardiovascular Stent

Bioabsorbable magnesium alloys are widely studied for various implant applications, as they reduce the risks such as severe inflammatory response existing in permanent metallic implants. However, the over-fast corrosion rate of magnesium alloy is usually an obstacle in biomedical applications. Here we report a simple two-step reaction to introduce anticorrosive silane pre-treatment on MgZnYNd alloys before coating with poly (glycolide-co-lactide) (PLGA). The first step is to immerse the NaOH-activated MgZnYNd with bistriethoxysilylethane (BTSE) to form a cross-linked silane coating layer with enhanced corrosion resistance; the second step involves immobilizing amine functional groups for forming hydrogen bond with outer PLGA coating by treating the BTSE-modified MgZnYNd with 3-amino-propyltrimethoxysilane (APTES). We characterized the BTSE-APTES pre-treated PLGA coating on MgZnYNd by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), static contact angle and Acid Orange 7 measurement. Nano-scratch test was to verify that the scratch resistance of the PLGA coating with BTSE-APTES pre-treatment was superior to direct PLGA coating. Standard electrochemical measurements along with the long-term immersion results indicated that the BTSE-APTES pre-treatment rendered better in vitro degradation behavior. Cell adhesion and cell viability tests with both vascular smooth muscle cells (VSMC) and human umbilical vein endothelial cells (EA. hy926) demonstrated that BTSE-APTES pre-treated MgZnYNd substrate had significantly more beneficial effects. The favorable anti-corrosion behavior and biocompatibility of BTSE-APTES pre-treated PLGA coatings on MgZnYNd alloy suggest that the novel two-step silanization procedure may have the great potential to enhance the performance of the magnesium-based biomaterials and provide a valid solution for the conversion modification of cardiovascular implants, taking the magnesium-based bioabsorbable materials closer to clinical application.