A 5-year in vitro and in vivo study of the biodegradation of polylactide plates

Metastable FeMg particles for controlling degradation rate, mechanical properties, and biocompatibility of Poly(l-lactic) acid (PLLA) for orthopedic applications

Poly(l-lactic) acid (PLLA) is commonly used in bioabsorbable medical implants, but it suffers from slow degradation rate and rapid decline in mechanical properties for orthopedic applications. To address this drawback, recent research has explored the use of Mg as a filler for PLLA, resulting in composites with improved degradation rate and cytocompatibility compared to neat PLLA. In this study, FeMg powder particles were proposed as fillers for PLLA to investigate the potential of PLLA/FeMg composites for bioabsorbable implants. Cylinder specimens of PLLA, PLLA/Fe, PLLA/Mg and PLLA/FeMg were prepared using solvent casting followed by thermo-molding. The microstructure, thermal behavior, in vitro degradation behavior in simulated body fluid, mechanical properties and cytocompatibility of these composites were examined. The results indicate that the presence of FeMg particles prevents the deterioration of the composite mechanical properties, at least up to 14 days. Once a certain amount of degradation of the composite is reached, the degradation is faster than that of PLLA. Direct cytotoxicity assays revealed that pre-osteoblast MC3T3-E1 cells successfully adhered to and proliferated on the PLLA/FeMg surface. The inclusion of a low percentage of Mg into the Fe lattice not only accelerated the degradation rate of Fe but also improved its cytocompatibility. The enhanced degradation rate, mechanical properties, and osteoconductive properties of this composite make it a promising option for temporary orthopedic biomedical devices.

A Review on Manufacturing Processes of Biocomposites Based on Poly(α-Esters) and Bioactive Glass Fillers for Bone Regeneration

The incorporation of bioactive and biocompatible fillers improve the bone cell adhesion, proliferation and differentiation, thus facilitating new bone tissue formation upon implantation. During these last 20 years, those biocomposites have been explored for making complex geometry devices likes screws or 3D porous scaffolds for the repair of bone defects. This review provides an overview of the current development of manufacturing process with synthetic biodegradable poly(α-ester)s reinforced with bioactive fillers for bone tissue engineering applications. Firstly, the properties of poly(α-ester), bioactive fillers, as well as their composites will be defined. Then, the different works based on these biocomposites will be classified according to their manufacturing process. New processing techniques, particularly additive manufacturing processes, open up a new range of possibilities. These techniques have shown the possibility to customize bone implants for each patient and even create scaffolds with a complex structure similar to bone. At the end of this manuscript, a contextualization exercise will be performed to identify the main issues of process/resorbable biocomposites combination identified in the literature and especially for resorbable load-bearing applications.

Titanium or Biodegradable Osteosynthesis in Maxillofacial Surgery? In Vitro and In Vivo Performances

Osteosynthesis systems are used to fixate bone segments in maxillofacial surgery. Titanium osteosynthesis systems are currently the gold standard. However, the disadvantages result in symptomatic removal in up to 40% of cases. Biodegradable osteosynthesis systems, composed of degradable polymers, could reduce the need for removal of osteosynthesis systems while avoiding the aforementioned disadvantages of titanium osteosyntheses. However, disadvantages of biodegradable systems include decreased mechanical properties and possible foreign body reactions. In this review, the literature that focused on the in vitro and in vivo performances of biodegradable and titanium osteosyntheses is discussed. The focus was on factors underlying the favorable clinical outcome of osteosyntheses, including the degradation characteristics of biodegradable osteosyntheses and the host response they elicit. Furthermore, recommendations for clinical usage and future research are given. Based on the available (clinical) evidence, biodegradable copolymeric osteosyntheses are a viable alternative to titanium osteosyntheses when applied to treat maxillofacial trauma, with similar efficacy and significantly lower symptomatic osteosynthesis removal. For orthognathic surgery, biodegradable copolymeric osteosyntheses are a valid alternative to titanium osteosyntheses, but a longer operation time is needed. An osteosynthesis system composed of an amorphous copolymer, preferably using ultrasound welding with well-contoured shapes and sufficient mechanical properties, has the greatest potential as a biocompatible biodegradable copolymeric osteosynthesis system. Future research should focus on surface modifications (e.g., nanogel coatings) and novel biodegradable materials (e.g., magnesium alloys and silk) to address the disadvantages of current osteosynthesis systems.

Bone Union Quality after Fracture Fixation of Mandibular Head with Compression Magnesium Screws

For some years now, fixation devices created with resorbable magnesium alloys for the mandibular head have been clinically available and are beginning to be used. It is thus valuable to evaluate the quality of unions in these cases. The aim of this study was radiological comparison of magnesium versus titanium open reduction and rigid fixations in the mandible condylar head. Thirty-one patients were treated for fractures of the mandibular head with magnesium WE43 alloy headless compression screws (diameter 2.3 mm) and, as a reference group, 29 patients were included with similar construction titanium screws (diameter 1.8 mm). The 12-month results of the treatment were evaluated by the texture analysis of CT. Near similar treatment results were found with magnesium screws in traditional titanium fixation. Magnesium screws result in a higher density of the bone structure in the mandibular head. Conclusions: The quantitative evaluation of bone union after surgical treatment of mandibular head fracture with magnesium compression headless screws indicates that stable consolidation was achieved. Undoubtedly, the resorption process of the screws was found to be incomplete after 12 months, evidenced by a marked densification of the bone structure at the fracture site.

In Silico Biomechanical Evaluation of WE43 Magnesium Plates for Mandibular Fracture Fixation

Titanium fixation devices are the gold standard for the treatment of mandibular fractures; however, they present serious limitations, such as non-degradability and generation of imaging artifacts. As an alternative, biodegradable magnesium alloys have lately drawn attention due to their biodegradability and biocompatibility. In addition, magnesium alloys offer a relatively high modulus of elasticity in comparison to biodegradable polymers, being a potential option to substitute titanium in highly loaded anatomical areas, such as the mandible. This study aimed to evaluate the biomechanical competence of magnesium alloy WE43 plates for mandibular fracture fixation in comparison to the clinical standard or even softer polymer solutions. A 3D finite element model of the human mandible was developed, and four different fracture scenarios were simulated, together with physiological post-operative loading and boundary conditions. In a systematic comparison, the material properties of titanium alloy Ti-6Al-4V, magnesium alloy WE43, and polylactic acid (PLA) were assigned to the fixation devices, and two different plate thicknesses were tested. No failure was predicted in the fixation devices for any of the tested materials. Moreover, the magnesium and titanium fixation devices induced a similar amount of strain within the healing regions. On the other hand, the PLA devices led to higher mechanical strains within the healing region. Plate thickness only slightly influenced the primary fixation stability. Therefore, magnesium alloy WE43 fixation devices seem to provide a suitable biomechanical environment to support mandibular fracture healing in the early stages of bone healing. Magnesium WE43 showed a biomechanical performance similar to clinically used titanium devices with the added advantages of biodegradability and radiopacity, and at the same time it showed a remarkably higher primary stability compared to PLA fixation devices, which appear to be too unstable, especially in the posterior and more loaded mandibular fracture cases.

Biodegradable Fiducial Markers for Bimodal Near-Infrared Fluorescence- and X-ray-Based Imaging

This study aimed to evaluate, for the first time, implantable, biodegradable fiducial markers (FMs), which were designed for bimodal, near-infrared fluorescence-based (NIRF) and X-ray-based imaging. The developed FMs had poly(l-lactide-co-caprolactone)-based core-shell structures made of radiopaque (core) and fluorescent (shell) composites with a poly(l-lactide-co-caprolactone) matrix. The approved for human use contrast agents were utilized as fillers. Indocyanine green was applied to the shell material, whereas in the core materials, iohexol and barium sulfate were compared. Moreover, the possibility of tailoring the stability of the properties of the core materials by the addition of hydroxyapatite (HAp) was examined. The performed in situ (porcine tissue) and in vivo experiment (rat model) confirmed that the developed FMs possessed pronounced contrasting properties in NIRF and X-ray imaging. The presence of HAp improved the radiopacity of FMs at the initial state. It was also proved that, in iohexol-containing FMs, the presence of HAp slightly decreased the stability of contrasting properties, while in BaSO₄-containing ones, changes were less pronounced. A comprehensive material analysis explaining the differences in the stability of the contrasting properties was also presented. The tissue response around the FMs with composite cores was comparable to that of the FMs with a pristine polymeric core. The developed composite FMs did not cause serious adverse effects on the surrounding tissues even when irradiated in vivo. The developed FMs ensured good visibility for NIRF image-supported tumor surgery and the following X-ray image-guided radiotherapy. Moreover, this study replenishes a scanty report regarding similar biodegradable composite materials with a high potential for application.

Experience with resorbable plates for fixation of mandible fracture. A prospective study of 10 cases

Aim:

This study aims to evaluate the efficacy of resorbable plates for the fixation of mandible fracture.

Materials and Methods:

10 cases of fracture mandible were treated with resorbable plates using the Inion CPS system. Patients were evaluated during their entire hospital stay and recalled on 1^st, 4^th, and 8^th postoperative weeks. A thorough evaluation was done at the recall visits for any surgical and postoperative complications such as infection, malocclusion, neural abnormalities, wound or suture dehiscence, segmental mobility, foreign body reaction, and pain on biting. Bite force measurements were taken to evaluate the return of function.

Results:

Clinical union of the fracture was noted at the 8^th week follow-up examination for all cases. There were swelling and pain at the operated site at 8^th week follow-up for one patient, which was managed conservatively. The mean bite force was recorded for different regions and it increased over the entire follow-up period progressively.

Conclusion:

These plates and screws are an essential tool in the treatment of mandibular fractures owing to benefits such as biodegradability, biocompatibility, and the ability to be eliminated via the body's natural processes.

Design Challenges in Polymeric Scaffolds for Tissue Engineering

Numerous surgical procedures are daily performed worldwide to replace and repair damaged tissue. Tissue engineering is the field devoted to the regeneration of damaged tissue through the incorporation of cells in biocompatible and biodegradable porous constructs, known as scaffolds. The scaffolds act as host biomaterials of the incubating cells, guiding their attachment, growth, differentiation, proliferation, phenotype, and migration for the development of new tissue. Furthermore, cellular behavior and fate are bound to the biodegradation of the scaffold during tissue generation. This article provides a critical appraisal of how key biomaterial scaffold parameters, such as structure architecture, biochemistry, mechanical behavior, and biodegradability, impart the needed morphological, structural, and biochemical cues for eliciting cell behavior in various tissue engineering applications. Particular emphasis is given on specific scaffold attributes pertaining to skin and brain tissue generation, where further progress is needed (skin) or the research is at a relatively primitive stage (brain), and the enumeration of some of the most important challenges regarding scaffold constructs for tissue engineering.

Next Generation of Zinc Bisguanidine Polymerization Catalysts towards Highly Crystalline, Biodegradable Polyesters

Polylactide and polycaprolactone are both biodegradable polymers produced through metal-catalyzed ring-opening polymerization. For a truly sustainable lifecycle of these polymers it is essential to replace the industrially used cytotoxic catalyst tin(II) bis(2-ethylhexanoate) [Sn(Oct)₂ ] with non-toxic alternatives. Here, we report the fastest known robust catalyst in the polymerization of lactide and ϵ-caprolactone. This zinc guanidine catalyst can polymerize non-purified technical rac-lactide and ϵ-caprolactone in the melt at different [M]/[I] ratios with fast rate constants, high molar masses, and high yields in a short time, leading to colorless, transparent polymer. Moreover, we report that polylactide and polycaprolactone produced by zinc-guanidine complexes have favorably high crystallinities. In fact, the obtained polylactide shows a more robust degradation profile than its Sn(Oct)₂ -catalysed equivalent due to a higher degree of crystallinity.

Are Magnesium Screws Proper for Mandibular Condyle Head Osteosynthesis?

Recently, magnesium alloys have gained a significant amount of recognition as potential biomaterials for degradable implants for craniofacial bone screws. Purpose: The aim of this work was to compare screws made specifically for mandibular head osteosynthesis from different materials. Materials and Methods: Screws measuring 14 mm made by one manufacturer specifically for mandibular head osteosynthesis out of the following materials were selected: magnesium (MgYREZr), titanium (Ti6Al7Nb), and polymer (PLGA). The axial pull-out strength and torsional properties were investigated. Results: Each type of screw presented different pull-out forces (Kruskal–Wallis test, p < 0.001). The magnesium screw had the highest pull-out force of 399 N (cracked without the screw out being pulled out), followed by the titanium screw, with a force of 340 N, and the PLGA screw, with a force of 138 N (always cracked at the base of the screw head without the screw being pulled out). ANOVA was performed for the maximal torques before damage to the screw (torsional properties), revealing that the maximal torque of the magnesium screw was 16 N·cm, while that of the titanium screw was 19 N·cm. The magnesium screw was significantly weaker than the titanium screw (p < 0.05). The measured torque and pull-out force were not related to each other (p > 0.05). Conclusion: Among the screws compared, the metal biodegradable magnesium screw seems to be the most suitable material for multiscrew mandibular head osteosynthesis, considering the condition of the fragile screwdriver socket.

The Implications of Titanium Alloys Applied in Maxillofacial Osteosynthesis

Titanium alloys are known for their biological, mechanical and chemical properties, which have successfully expanded their use in the maxillofacial field. The internal fixation using titanium miniplates and screws offer a new perspective for the treatment of trauma and in orthognathic surgery and maxillofacial oncology. Although, titanium is highly recommended for its excellent biocompatibility, recent research has focused on identifying the potential local and general implications of the interactions between the human tissue and the metallic particles. This present review aims to outline the existing tissue changes, cellular alterations and future perspectives regarding the use of titanium-based alloys as osteosynthesis materials, taking into consideration the existing present debate whether the routinely removal of these materials should be an indication.

Effect of Ethylene Oxide and Gamma (γ-) Sterilization on the Properties of a PLCL Polymer Material in Balloon Implants

Poly-l-lactide-co-ε-caprolactone (PLCL) is a unique polymer containing both polylactic acid and poly-ε-caprolactone (PCL) chain units, and thus it has better flexible and biodegradable properties. Based on these unique properties of PLCL, we have developed balloons that are now widely used in treating major medical problems [Biomaterials 2016, 105, 109-116]. One of the most important considerations needed for balloons is to ensure that the material properties remain similar after undergoing ethylene oxide (EtO) or gamma (γ-) sterilization treatments. From the biotechnological point of view, we focused on analyzing the vital molecular properties of the PLCL material after sterilization, such as changes in crystallinity, molecular weight distributions (M _w, M _n, and polydispersity index), and inherent viscosity (η). Analysis of the data reveals that EtO sterilization does not engender any change in crystallinity, melting temperature (T _m), molecular weights, and η of the polymer. On the contrary, γ-radiations induce chain scission and consequential decrease of ∼33 and ∼15% in molecular weights and η values, respectively. Based on our observations, we recommend EtO sterilization instead of γ-radiation for PLCL. This ensures prolonged stability of the polymer against degradation in a biological environment, long-shelf life, and absolute assurance that balloon failures do not occur after implantation.

Resorbable Implants for Mandibular Fracture Fixation: A Systematic Review and Meta-Analysis

Mandibular fractures in adults commonly require rigid fixation to ensure proper occlusion while minimizing infection risks. Numerous centers have assessed the efficacy of resorbable materials as a potential alternative to metallic plates. The purpose of the current systematic review and meta-analysis is to shed light on overall outcomes for resorbable implants and to compare these results to those for metallic counterparts.

The effectiveness of biodegradable instrumentation in the treatment of spinal fractures

INTRODUCTION

A variety of biodegradable implants (screws, rods, plates and cages) are available which are composed of many different biodegradable polymers with varying characteristics. The present review of animal and clinical studies examines the efficacy and safety of biodegradable implants in spinal fracture intervention.

METHODS

A review of the literature through March 2018 was performed using PubMed and Cochrane databases. Success rates were calculated according to sufficient tissue biocompatibility, solid clinical fusion and propensity for osseointegration.

RESULTS

49 articles (24 animal and 25 human studies) were included. In animal experiments, the overall success rate for spinal fusion was 60.3%, while the mean success rate regarding the cervical spine was 51.8% compared to 68.1% for the lumbar spine (p = 0.002). In studies involving control group(s): the mean bioabsorbable implant success rate for spinal fusion was 42% compared to 57% for conventional implants (p = 0.0016). In the lumbar spine pL-lactide acid (PLLA) had 75.2% success rate compared to poly (L-lactide-co-DL-lactide) (PLDLLA) at 53.4% (p = 0.003). In clinical studies, the overall mean success rate was 89%, while the mean success rate regarding the cervical spine was 92%, as compared to 83.6% for the lumbar spine (p = 0.001). In studies involving control group(s): the mean bioabsorbable implant success rate was 75% compared to a conventional implant mean success rate of 97% (p<0.0001). In the cervical spine PLLA had a 98.7% success rate compared to 90% with PLDLLA (p = 0.015). In the lumbar spine PLDLLA had 84.7% success rate compared to 63.6% for poly-glycolic acid (PGA) (p = 0.085).

DISCUSSION

Studies combined biodegradable and conventional implants. Polymers were used in various combinations and surface modification of the implants also varied. Comparison studies were of small sample size. Animal and clinical studies diverged. The current data are not encouraging. The end-point of assessing osseointegration varies in the studies and is indeterminate. In early stages the structure comparison of osseous restoration using biodegradable implants appears inferior to utilization of conventional cages and instrumentation. There is no statistically significant evidence supporting the efficacy of biodegradable implants replacing traditional instrumentation. There is a lack of prospective clinical trials with long-term follow-up regarding utilization of biodegradable implants and the available data does not support their routine use in spinal fracture intervention.

Effect of Chemical Composition Variant and Oxygen Plasma Treatments on the Wettability of PLGA Thin Films, Synthesized by Direct Copolycondensation

The synthesis of high molecular weight poly (lactic-co-glycolic) acid (PLGA) copolymers via direct condensation copolymerization is itself a challenging task. Moreover, some of the characteristic properties of polylactide (PLA)-based biomaterials, such as brittleness, hydrophobicity, and longer degradation time, are not suitable for certain biomedical applications. However, such properties can be altered by the copolymerization of PLA with other biodegradable monomers, such as glycolic acid. A series of high molecular weight PLGAs were synthesized through the direct condensation copolymerization of lactic and glycolic acids, starting from 0 to 50 mol% of glycolic acid, and the wettability of its films was monitored as a function of the feed molar ratio. Copolymerization was performed in the presence of a bi-catalytic system using stannous chloride dihydrate and methanesulfonic acid (MSA). The viscosity average molecular weight of the resulting PLGA was in the range of 80k to 135k g/mol. The PLGA films were prepared using the solvent casting technique, and were treated with oxygen plasma for 2 min. The water contact angle of the PLGA films was determined before and after the oxygen plasma treatments, and it was observed that the wettability increased with an increase in the glycolic acid contents, however, the manifolds increased after 2 min of oxygen plasma treatments.

New fabrication method of silk fibroin plate and screw based on a centrifugal casting technique

Recently, a newer generation of absorbable biomaterials has been developed from silk. Silk is approved by the US Food and Drug Administration, has robust mechanical features, and is biocompatible. Moreover, it offers the ability to be functionalized with bioactive compounds, making it ideal for use in new medical devices. Thus, many researchers have considered that absorbable devices made from silk may be able to overcome current limitations and could be used to meet a broader range of fixation needs. Here, we describe a novel method for the fabrication of silk fibroin (SF)-based bioabsorbable fixation systems using a centrifugal casting technique and incorporating a 3D printer. This approach allows us to create the desired geometric design for the fixation system easily. Moreover, our products demonstrated smoother surface profiles and more homogenous and dense cross-sectional architectures. Furthermore, our plates exhibited very similar mechanical properties compared with commercially used one, and our screws showed more than 70% of their initial mass after 7 weeks on the enzymatic degradation test. On in vivo analysis, we found that our devices were well-maintained in the location of initial fixation, and new bone formation was also observed around this. By these results, we suggest that the SF-based plate/screw prepared by our novel method might be used for the internal fixation of fracture sites.

Modified Magnesium Hydroxide Nanoparticles Inhibit the Inflammatory Response to Biodegradable Poly(lactide- co-glycolide) Implants

Biodegradable polymers have been extensively used in biomedical applications, ranging from regenerative medicine to medical devices. However, the acidic byproducts resulting from degradation can generate vigorous inflammatory reactions, often leading to clinical failure. We present an approach to prevent acid-induced inflammatory responses associated with biodegradable polymers, here poly(lactide- co-glycolide), by using oligo(lactide)-grafted magnesium hydroxide (Mg(OH)₂) nanoparticles, which neutralize the acidic environment. In particular, we demonstrated that incorporating the modified Mg(OH)₂ nanoparticles within degradable coatings on drug-eluting arterial stents efficiently attenuates the inflammatory response and in-stent intimal thickening by more than 97 and 60%, respectively, in the porcine coronary artery, compared with that of drug-eluting stent control. We also observed that decreased inflammation allows better reconstruction of mouse renal glomeruli in a kidney tissue regeneration model. Such modified Mg(OH)₂ nanoparticles may be useful to extend the applicability and improve clinical success of biodegradable devices used in various biomedical fields.

WITHDRAWN: A Randomized Controlled Trial Comparing Between Titanium Osteosynthesis and Biodegradable Osteosynthesis in Access Mandibulotomy for Oral Malignancy

Available online April 7, 2018. This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Novel ultrasound assisted suture anchor system using the BoneWelding® technology yields a comparable primary stability in osteopenic and healthy human humeri as a benchmark anchor

Introduction

The aim of this biomechanical study was to evaluate the primary stability of the SportWelding® Sombrero 3.6 mm suture anchor system in osteopenic and healthy cadaveric humeri.

Methods

The Sombrero® and BioCorkscrew® anchors were deployed in 8 osteopenic and 4 healthy cadaver humeri after the bone mineral density (BMD) measurements of the 32 specimens. Both anchors were loaded with a USP Nr. 2 FiberWire® suture. An established cyclic testing protocol was performed. The maximum failure load (Fmax), the system displacement and the modes of failure were recorded.

Results

The F_max and system displacement of the Sombrero® in osteopenic and healthy humeri was equivalent to the Bio-Corkscrew® benchmark anchor; there were no significant differences in the maximum failure loads and system displacement values. Only anchor and suture dislocations were observed; suture ruptures did not occur.

Conclusion

This study shows that the Sombrero® yields similar maximum failure loads and system displacement values as the established Bio-Corkscrew® benchmark anchor. The primary stability of the Sombrero® and Bio-Corkscrew® seems to be independent of the bone mineral quality. This relatively small-sized polymer anchor is independent of the BMD and may be an alternative to established suture anchors in rotator cuff repair.

Clinical Evaluation of an Unsintered Hydroxyapatite/Poly-L-Lactide Osteoconductive Composite Device for the Internal Fixation of Maxillofacial Fractures

Introduction:

OSTEOTRANS MX (Takiron Co, Ltd, Osaka, Japan) is a resorbable osteosynthetic material composed of an unsintered hydroxyapatite/poly-l-lactide composite, and its osteoconductive capacity has been documented. The authors here report their clinical experience using OSTEOTRANS MX.

Methods:

The authors treated 35 patients (19 men, 16 women; age, 14–88 years; mean ± standard deviation, 38.4 ± 19.9 years) with maxillofacial fractures. The authors used standard surgery to stabilize fractures in all patients, fitting resorbable plates (thickness, 1.0 or 1.4 mm) and screws (diameter, 2 mm) according to Arbeitsgemeinschaft für Osteosynthesefragen/Association (AO) for the Study of Internal Fixation guidelines.

Results:

All patients eventually achieved satisfactory healing with favorable restoration of form and function without foreign body reaction. Complications occurred in 3 patients—plate exposure in 2 and discomfort in 1. However, fracture sites healed in all patients. Scanning electron microscopy revealed that the devices bonded directly to the bone without interposition of nonmineralized tissue.

Conclusion:

OSTEOTRANS MX is a useful material with few complications. Its osteoconductive bioactivity is advantageous for the early functional improvement of maxillofacial fractures.

The Clinical Feasibility of Newly Developed Thin Flat-Type Bioresorbable Osteosynthesis Devices for the Internal Fixation of Zygomatic Fractures: Is There a Difference in Healing Between Bioresorbable Materials and Titanium Osteosynthesis?

INTRODUCTION

In recent years, bioresorbable plates have undergone remarkable development. However, there has been no attendant improvement in their strength, because strength requires thickness, and complications such as palpability are related to the thickness of bioresorbable plate systems. In this clinical study, we compared the surgical management of zygomatic fractures using newly developed thinner bioresorbable materials or conventional titanium miniplates.

METHODS

Twelve patients with zygomatic fractures were randomly divided equally into 2 groups (6 with new bioresorbable osteosynthesis materials and 6 with standard titanium miniplates). Using computed tomography, we evaluated the thickness of the soft tissue and plate at the zygomaticofrontal sutures in each patient with the help of detailed radiographic computed tomography data at 6 months postoperatively. We compared the amount of soft-tissue volume increase between the uninjured healthy and injured operated sides in each patient.

RESULTS

Both groups eventually achieved satisfactory healing, with a favorable restoration of form and function and without any complications, including palpability. The amount of soft-tissue volume increase at the operated side relative to the uninjured healthy side using new thin bioresorbable plates was 131.1% (range: 101.5-165.8). On the other hand, that of titanium miniplates was 126.4% (range: 102.2-167.6). There was no statistically significant difference (P > 0.05).

CONCLUSION

This newly developed thinner flat-type bioresorbable plate system could be considered clinically useful in the treatment of zygomatic fractures even in easily palpated areas, such as the infraorbital rim or zygomaticofrontal sutures, without any healing differences in skeleton as compared with conventional titanium miniplates.

Influence of dynamic compressive loading on the in vitro degradation behavior of pure PLA and Mg/PLA composite

The effects of dynamic compressive loading on the in vitro degradation behavior of pure poly-lactic acid (PLA) and PLA-based composite unidirectionally reinforced with micro-arc oxidized magnesium alloy wires (Mg/PLA) are investigated. Dynamic compressive loading is shown to accelerate degradation of pure PLA and Mg/PLA. As the applied stress is increased from 0.1MPa to 0.9MPa or frequency from 0.5Hz to 2.5Hz, the overall degradation rate goes up. After immersion for 21days at 0.9MPa and 2.5Hz, the bending strength retention of the composite and pure PLA is 60.1% and 50%, respectively. Dynamic loading enhances diffusion of small acidic molecules resulting in significant pH decrease in the immersion solution. The synergistic reaction between magnesium alloy wires and PLA in the composite is further clarified by electrochemical tests. The degradation behavior of the pure PLA and PLA matrix in the composite under dynamic conditions obey the first order degradation kinetics and a numerical model is postulated to elucidate the relationship of the bending strength, stress, frequency, and immersion time under dynamic conditions.

STATEMENT OF SIGNIFICANCE

We systematically study the influence of dynamic loading on the degradation behavior of pure PLA and Mg/PLA. Dynamic compressive loading is shown to accelerate degradation of pure PLA and Mg/PLA. The synergistic reaction between magnesium alloy wires and PLA in the composite is firstly clarified by electrochemical tests. The degradation behavior of the pure PLA and PLA matrix in the composite under dynamic conditions obey the first order degradation kinetics. Then, a numerical model is postulated to elucidate the relationship of the bending strength, stress, frequency, and immersion time under dynamic conditions.

A co-culture system with three different primary human cell populations reveals that biomaterials and MSC modulate macrophage-driven fibroblast recruitment

The biological response to implanted biomaterials is a complex and highly coordinated phenomenon involving many different cell types that interact within 3D microenvironments. Here, we increased the complexity of a 3D platform to include at least 3 cell types that play a role in the host response upon scaffold implantation. With this system, it was possible to address how immune responses triggered by 3D biomaterials mediate recruitment of stromal cells that promote tissue regeneration, mesenchymal stromal/stem cells (MSC), or a foreign body response, fibroblasts. Primary human macrophages yielded the highest fibroblast recruitment when interacting with chitosan scaffolds but not polylactic acid. Interestingly, when there were MSC and fibroblasts in the same environment, macrophages in chitosan scaffolds again promoted a significant increase on fibroblast recruitment, but not of MSC. However, macrophages that were firstly allowed to interact with MSC within the scaffolds were no longer able to recruit fibroblasts. This study illustrates the potential to use different scaffolds to regulate the dynamics of recruitment of proregenerative or fibrotic cell types through immunomodulation. Overall, this work strengths the idea that ex vivo predictive systems need to consider the different players involved in the biological response to biomaterials and that timing of arrival of specific cell types will affect the outcome.

Macrophage interactions with polylactic acid and chitosan scaffolds lead to improved recruitment of human mesenchymal stem/stromal cells: a comprehensive study with different immune cells

Despite the importance of immune cell-biomaterial interactions for the regenerative outcome, few studies have investigated how distinct three-dimensional biomaterials modulate the immune cell-mediated mesenchymal stem/stromal cells (MSC) recruitment and function. Thus, this work compares the response of varied primary human immune cell populations triggered by different model scaffolds and describes its functional consequence on recruitment and motility of bone marrow MSC. It was found that polylactic acid (PLA) and chitosan scaffolds lead to an increase in the metabolic activity of macrophages but not of peripheral blood mononuclear cells (PBMC), natural killer (NK) cells or monocytes. PBMC and NK cells increase their cell number in PLA scaffolds and express a secretion profile that does not promote MSC recruitment. Importantly, chitosan increases IL-8, MIP-1, MCP-1 and RANTES secretion by macrophages while PLA stimulates IL-6, IL-8 and MCP-1 production, all chemokines that can lead to MSC recruitment. This secretion profile of macrophages in contact with biomaterials correlates with the highest MSC invasion. Furthermore, macrophages enhance stem cell motility within chitosan scaffolds by 44% but not in PLA scaffolds. Thus, macrophages are the cells that in contact with engineered biomaterials become activated to secrete bioactive molecules that stimulate MSC recruitment.

Comparison of the long-term clinical performance of a biodegradable and a titanium fixation system in maxillofacial surgery: A multicenter randomized controlled trial

BACKGROUND

Biodegradable fixation systems could reduce or eliminate problems associated with titanium removal of implants in a second operation.

AIM

The aim of this study was to compare the long-term (i.e. >5 years postoperatively) clinical performance of a titanium and a biodegradable system in oral and maxillofacial surgery.

MATERIALS AND METHODS

The present multicenter Randomized Controlled Trial (RCT) was performed in four hospitals in the Netherlands. Patients treated with a bilateral sagittal split osteotomy (BSSO) and/or a Le Fort-I osteotomy, and those treated for fractures of the mandible, maxilla, or zygoma were included from December 2006 to July 2009. The patients were randomly assigned to either a titanium (KLS Martin) or a biodegradable group (Inion CPS).

RESULTS

After >5 years postoperatively, plate removal was performed in 22 of the 134 (16.4%) patients treated with titanium and in 23 of the 87 (26.4%) patients treated with the biodegradable system (P = 0.036, hazard ratio (HR) biodegradable (95% CI) = 2.0 (1.05-3.8), HR titanium = 1). Occlusion, VAS pain scores, and MFIQ showed good and (almost) pain free mandibular function in both groups.

CONCLUSION

In conclusion, the performance of the Inion CPS biodegradable system was inferior compared to the KLS Martin titanium system regarding plate/screws removal in the abovementioned surgical procedures.

TRIAL REGISTRATION

http://controlled-trials.com ISRCTN44212338.

[Biodegradable fixation systems in pediatric craniofacial surgery: 10-year experience with 324 patients]

INTRODUCTION

Over the past 15 years, resorbable materials have been successfully used for osteosynthesis, but their high cost prevents widespread application. However, the use of resorbable systems could be a method of choice, especially in treatment of children in the active growth period. Obviously, biodegradable materials not only are highly competitive with known metal constructs in terms of fixation rigidity, biocompatibility, and a low risk of infection but also have an undeniable advantage, such as gradual resorption allowing quick return of damaged bones to the physiological conditions of functioning. A special feature of bioresorbable systems is that they can be assembled using ultrasonic welding, which greatly facilitates the fixation process and also provides necessary rigidity, even in cases of joining very thin bones when reliable fixation with screws is impossible.

MATERIAL AND METHODS

Over the past 10 years, we have used biodegradable systems in 324 patients. In 244 of them, we used traditional (plate/screw) systems; in 80 cases, an ultrasonic welding system was chosen for osteosynthesis.

RESULTS

In the present work, we discuss, based on clinical evidence, the advantages and disadvantages of both fixation systems for reconstructive craniofacial surgery in children.

Efficacy and Safety of Biodegradable Osteofixation Devices in Oral and Maxillofacial Surgery: a Systematic Review

The use of osteofixation devices should be evidence-based if uncomplicated bone healing is to be achieved. Numerous studies describe and claim the advantages of biodegradable over titanium devices as a bone fixation method. Here, we systematically review the available literature to determine the clinical efficacy and safety of biodegradable devices compared with titanium devices in oral and maxillofacial surgery. In addition, related general aspects of bone surgery are discussed. We conducted a highly sensitive search in the databases of MEDLINE (1966–2005), EMBASE (1989–2005), and CENTRAL (1800–2005) to identify eligible studies. Eligible studies were independently evaluated by two assessors using a quality assessment scale. The study selection procedure revealed four methodologically ‘acceptable’ articles. Owing to the different outcome measures used in the studies, it was impossible to perform a meta-analysis. Therefore, the major effects regarding the stability and morbidity of fracture fixation using titanium and biodegradable fixation systems were qualitatively described. Any firm conclusions regarding the fixation of traumatically fractured bone segments cannot be drawn, due to the lack of controlled clinical trials. Regarding the fixation of bone segments in orthognathic surgery, only a few controlled clinical studies are available. There does not appear to be a significant short-term difference between titanium and biodegradable fixation systems regarding stability and morbidity. However, definite conclusions, especially with respect to the long-term performance of biodegradable fixation devices used in maxillofacial surgery, cannot be drawn. Abbreviations: CENTRAL, Cochrane Central Register of Controlled Trials; MeSH, Medical Subject Heading; VAS, Visual Analogue Scale; and W, weight.

Resorbable Mesh as a Containment System in Mandibular Reconstruction

The recent advances seen in computer technologies and biomaterials have changed the approach to craniomaxillofacial surgery. In this report, the authors describe the technique of using a resorbable containment system for bone graft in a large mandibular reconstruction patient. The authors provide a patient report with a 1-year follow-up.

Biodegradable fiducial markers for X-ray imaging – soft tissue integration and biocompatibility

This study aims at investigation of material for innovative fiducial markers for soft tissue in X-ray based medical imaging. NH₃ plasma modified P[LAcoCL] combined with BaSO₄ and hydroxyapatite as radio-opaque fillers appears to be a promising material systems for this application.

Effect of a bioabsorbable, super-high molecular weight poly-D,L-lactic acid plate containing recombinant human bone morphogenetic protein-2 for fracture healing

The aim of this study was to investigate the effect of a bioabsorbable, super-high molecular weight poly-D,L-lactic acid (PDLLA) plate exhibiting the sustained release of recombinant human bone morphogenetic protein-2 (rhBMP-2) (PDLLA-rhBMP-2) on the treatment of fracture with internal fixation. A total of 32 New Zealand rabbits were randomly allocated to one of four groups (2, 4, 8 and 12 weeks), and a 2.5-mm middle ulnar osteotomy was performed bilaterally. The right side (experimental side) was fixed internally with PDLLA-rhBMP-2, and the left side (control side) was fixed with a normal PDLLA plate. At 2, 4, 8 and 12 weeks after surgery, the gross pathology of the ulnas was examined and radiographic, histological and computer image analyses were performed. The results demonstrated that the ulna fractures were fixed stably with the two bioactive plates at 2, 4, 8 and 12 weeks after surgery. At the 8-week time-point, 7 rabbits exhibited good healing at the osteotomy site on the experimental side. At 12 weeks after surgery, 8 rabbits exhibited good healing at the osteotomy site on both sides, but the experimental side showed enhanced compatibility between the plates and surrounding tissue, faster bone formation, a greater bone regeneration mass and better medullary canal structure compared with the control side. In conclusion, PPLLA-rhBMP-2 may be effectively used to treat fracture or nonunion at a non-weight-bearing site.

Intraocular Implants for the Treatment of Autoimmune Uveitis

Uveitis is the third leading cause of blindness in developed countries. Currently, the most widely used treatment of non-infectious uveitis is corticosteroids. Posterior uveitis and macular edema can be treated with intraocular injection of corticosteroids, however, this is problematic in chronic cases because of the need for repeat injections. Another option is systemic immunosuppressive therapies that have their own undesirable side effects. These systemic therapies result in a widespread suppression of the entire immune system, leaving the patient susceptible to infection. Therefore, an effective localized treatment option is preferred. With the recent advances in bioengineering, biodegradable polymers that allow for a slow sustained-release of a medication. These advances have culminated in drug delivery implants that are food and drug administration (FDA) approved for the treatment of non-infectious uveitis. In this review, we discuss the types of ocular implants available and some of the polymers used, implants used for the treatment of non-infectious uveitis, and bioengineered alternatives that are on the horizon.

In vitro and in vivo evaluation of a polylactic acid-bioactive glass composite for bone fixation devices

Poly(lactic acid) is nowadays among the most used bioabsorbable materials for medical devices. To promote bone growth on the material surface and increase the degradation rate of the polymer, research is currently focused on organic-inorganic composites by adding a bioactive mineral to the polymer matrix. The purpose of this study was to investigate the ability of a poly(L,DL-lactide)-Bioglass® (P(L,DL)LA-Bioglass(®) 45S5) composite to be used as a bone fixation device. In vitro cell viability testing of P(l,dl)LA based composites containing different amounts of Bioglass(®) 45S5 particles was investigated. According to the degradation rate of the P(L,DL)LA matrix and the cytocompatibility experiments, the composite with 30 wt % of Bioglass® particles seemed to be the best candidate for further investigation. To study its behavior after immersion in simulated physiological conditions, the degradation of the composite was analyzed by measuring its weight loss and mechanical properties and by proceeding with X-ray tomography. We demonstrated that the presence of the bioactive glass significantly accelerated the in vitro degradation of the polymer. A preliminary in vivo investigation on rabbits shows that the addition of 30 wt % of Bioglass(®) in the P(L,DL)LA matrix seems to trigger bone osseointegration especially during the first month of implantation. This composite has thus strong potential interest for health applications.

Metal/polymer composite Nuss bar for minimally invasive bar removal after Pectus Excavatum treatment: FEM simulations

This study aims at assessing the mechanical behavior of a composite metal/polymer bar to be implanted in the retrosternal position, in order to correct chest wall deformities, such as Pectus Excavatum. A 300-mm-long, 12.7-mm-wide, and 3.5-mm-thick Nuss bar was considered, made of different metals and biodegradable polymers, fixed at its extremities, and with a constant force of 250 N applied on its center. Two different geometries for the metal elements to be embedded in the polymeric matrix were tested: in the former, thin metal sheets and in the latter, cylindrical metal reinforcing rods were considered. Finite element method simulation results are reported, in terms of maximum stress and strain of the bar. Furthermore, the maximum stress values obtained by varying metal sheet thickness or rod diameter (and therefore the volumetric percentage of metal within the matrix) for different material combinations are also shown; optimal configuration for the Pectus Excavatum treatment was finally identified for a composite Nuss bar.

Bone tissue engineering scaffolding: computer-aided scaffolding techniques

Tissue engineering is essentially a technique for imitating nature. Natural tissues consist of three components: cells, signalling systems (e.g. growth factors) and extracellular matrix (ECM). The ECM forms a scaffold for its cells. Hence, the engineered tissue construct is an artificial scaffold populated with living cells and signalling molecules. A huge effort has been invested in bone tissue engineering, in which a highly porous scaffold plays a critical role in guiding bone and vascular tissue growth and regeneration in three dimensions. In the last two decades, numerous scaffolding techniques have been developed to fabricate highly interconnective, porous scaffolds for bone tissue engineering applications. This review provides an update on the progress of foaming technology of biomaterials, with a special attention being focused on computer-aided manufacturing (Andrade et al. 2002) techniques. This article starts with a brief introduction of tissue engineering (Bone tissue engineering and scaffolds) and scaffolding materials (Biomaterials used in bone tissue engineering). After a brief reviews on conventional scaffolding techniques (Conventional scaffolding techniques), a number of CAM techniques are reviewed in great detail. For each technique, the structure and mechanical integrity of fabricated scaffolds are discussed in detail. Finally, the advantaged and disadvantage of these techniques are compared (Comparison of scaffolding techniques) and summarised (Summary).

Knitted polylactide 96/4 L/D structures and scaffolds for tissue engineering: shelf life, in vitro and in vivo studies

This study covers the whole production cycle, from biodegradable polymer processing to an in vivo tissue engineered construct. Six different biodegradable polylactide 96/4 L/D single jersey knits were manufactured using either four or eight multifilament fiber batches. The properties of those were studied in vitro for 42 weeks and in 0- to 3-year shelf life studies. Three types (Ø 12, 15 and 19 mm) of cylindrical scaffolds were manufactured from the knit, and the properties of those were studied in vitro for 48 weeks. For the Ø 15 mm scaffold type, mechanical properties were also studied in a one-year in vivo experiment. The scaffolds were implanted in the rat subcutis. All the scaffolds were γ-irradiated prior to the studies. In vitro, all the knits lost 99% of their mechanical strength in 30 weeks. In the three-year follow up of shelf life properties, there was no decrease in the mechanical properties due to the storage time and only a 12% decrease in molecular weight. The in vitro and in vivo scaffolds lost their mechanical properties after 1 week. In the case of the in vivo samples, the mechanical properties were restored again, stepwise, by the presence of growing/maturing tissue between weeks 3 and 12. Faster degradation was observed with in vitro scaffolds compared to in vivo scaffolds during the one-year follow up.

Treatment of malar and midfacial fractures with osteoconductive forged unsintered hydroxyapatite and poly-L-lactide composite internal fixation devices

PURPOSE

To evaluate the internal fixation of malar and midfacial fractures, long-term results, and biocompatibility of osteoconductive internal fixation devices composed of a forged composite of unsintered hydroxyapatite and poly-L-lactide (F-u-HA/PLLA).

MATERIALS AND METHODS

From January 2006 to June 2010, 29 patients (24 males and 5 females; age 33 ± 15 years) were included in the present prospective study. The fracture type was malar in 24 patients, midfacial in 5, isolated orbital floor blowout in 2, and frontal sinus, cranial base in 2 patients. The fractures were fixed with internal fixation devices; these were plates and screws composed of F-u-HA/PLLA. The 24 patients with malar fractures were treated with a single 4-hole L-plate or a straight plate at the infrazygomatic crest.

RESULTS

All fractures with internal fixation using devices composed of F-u-HA/PLLA healed well. All malar and midfacial fractures had satisfactory long-term stability. The follow-up examinations at 12 to 67 months after surgery showed that most patients had no complaints, although 2 patients (15%) had a foreign body reaction that was treated by implant removal, with complete symptom resolution. At 5 years after fracture fixation, 2 patients had ultrasound and 2 had radiographic evidence of residual material. An exemplar biopsy showed direct bone growth into the material.

CONCLUSIONS

In patients with malar and midfacial fractures, hardware composed of the F-u-HA/PLLA composite provided reliable and satisfactory internal fixation, intraoperative handling, long-term stability, and biocompatibility. Direct bone growth into the material could be histopathologically exemplified, in contrast to previous polymer fixations that were resorbed and surrounded by a connective tissue layer. This finding indicates that long-term F-u-HA/PLLA residual material will be included into the remodeled bone, which was confirmed on long-term follow-up radiographs.

Safety evaluation of a bioglass-polylactic acid composite scaffold seeded with progenitor cells in a rat skull critical-size bone defect

Treating large bone defects represents a major challenge in traumatic and orthopedic surgery. Bone tissue engineering provides a promising therapeutic option to improve the local bone healing response. In the present study tissue biocompatibility, systemic toxicity and tumorigenicity of a newly developed composite material consisting of polylactic acid (PLA) and 20% or 40% bioglass (BG20 and BG40), respectively, were analyzed. These materials were seeded with mesenchymal stem cells (MSC) and endothelial progenitor cells (EPC) and tested in a rat calvarial critical size defect model for 3 months and compared to a scaffold consisting only of PLA. Serum was analyzed for organ damage markers such as GOT and creatinine. Leukocyte count, temperature and free radical indicators were measured to determine the degree of systemic inflammation. Possible tumor occurrence was assessed macroscopically and histologically in slides of liver, kidney and spleen. Furthermore, the concentrations of serum malondialdehyde (MDA) and sodium oxide dismutase (SOD) were assessed as indicators of tumor progression. Qualitative tissue response towards the implants and new bone mass formation was histologically investigated. BG20 and BG40, with or without progenitor cells, did not cause organ damage, long-term systemic inflammatory reactions or tumor formation. BG20 and BG40 supported bone formation, which was further enhanced in the presence of EPCs and MSCs.

This investigation reflects good biocompatibility of the biomaterials BG20 and BG40 and provides evidence that additionally seeding EPCs and MSCs onto the scaffold does not induce tumor formation.

Bioabsorbable fixation devices in trauma and bone surgery: current clinical standing

Bioabsorbable fixation devices are increasingly used in trauma, orthopedic and craniomaxillofacial surgery. The devices are essentially made of polylactic acid and/or polyglycolic acid polymers. Ultra-high-strength implants are manufactured from such polymers using self-reinforcing techniques. Implants are available for stabilization of fractures, osteotomies, bone grafts and fusions, as well as for reattachment of ligaments, tendons, meniscal tears and other soft tissue structures. As these implants are completely absorbed, the need for a removal operation is overcome and long-term interference with tendons, nerves and the growing skeleton is avoided. The risk of implant-associated stress shielding, peri-implant osteoporosis and infections is reduced. Implants do not interfere with clinical imaging. Current clinical use of bioabsorbable devices is reviewed.

In vitro and in vivo cytocompatibility of electrospun nanofiber scaffolds for tissue engineering applications

An electrospun polymeric-based nanofibrous scaffold mimicking the extracellular matrix and serving as a temporary support for cell growth, adhesion, migration and proliferation.