The use of bioabsorbable osteofixation devices in craniomaxillofacial surgery

Bioabsorbable implants in forefoot surgery: a review of materials, possibilities and disadvantages

Bioabsorbable and biodegradable implants offer new possibilities in orthopaedic and trauma surgery. As soon as the initial stability of the degradable implants has reached the qualities of conventional materials, new devices may find usage in younger and more demanding patients. Residual conventional osteosynthetic material or the necessity to remove metal increasingly seems to be more of an adverse event than daily practice in forefoot surgery. Nevertheless, some drawbacks need to be discussed. Recent literature screened for the use of bioabsorbable and biodegradable materials in forefoot surgery, available implants and indications in forefoot surgery were analysed and summarized. Apart from common indications in forefoot surgery, points of interest were the type of biomaterial, the process of biodegradation and biointegration, and possible adverse events. Materials were comprehensively discussed for each indication based on the available literature. Polylactide, polyglycoside and polydioxanone are considered safe and sufficiently stable for use in forefoot surgery. Low complication rates (e.g. 0.7% for pin fixation in hallux deformities) are given. Magnesium implants suffered from an extensive corrosive process in the first generation but now seem to be safe in forefoot surgery and offer good options compared with conventional titanium screws, especially in procedures of the first ray. Allograft bone has proven feasibility in small case series, but still lacks larger or randomized clinical trials. The first results are promising. Bioresorbable and osseointegrating devices offer attractive new possibilities for surgeons and patients. Despite all the known advantages, the difficulties and possible complications must not be forgotten, such as soft tissue reactions, unwanted osteolysis and a lower primary mechanical load capacity.

Cite this article: EFORT Open Rev 2021;6:1132-1139. DOI: 10.1302/2058-5241.6.200157

In Vitro Cartilage Regeneration with a Three-Dimensional Polyglycolic Acid (PGA) Implant in a Bovine Cartilage Punch Model

Resorbable polyglycolic acid (PGA) chondrocyte grafts are clinically established for human articular cartilage defects. Long-term implant performance was addressed in a standardized in vitro model. PGA implants (+/- bovine chondrocytes) were placed inside cartilage rings punched out of bovine femoral trochleas (outer Ø 6 mm; inner defect Ø 2 mm) and cultured for 84 days (12 weeks). Cartilage/PGA hybrids were subsequently analyzed by histology (hematoxylin/eosin; safranin O), immunohistochemistry (aggrecan, collagens 1 and 2), protein assays, quantitative real-time polymerase chain reactions, and implant push-out force measurements. Cartilage/PGA hybrids remained vital with intact matrix until 12 weeks, limited loss of proteoglycans from "host" cartilage or cartilage-PGA interface, and progressively diminishing release of proteoglycans into the supernatant. By contrast, the collagen 2 content in cartilage and cartilage-PGA interface remained approximately constant during culture (with only little collagen 1). Both implants (+/- cells) displayed implant colonization and progressively increased aggrecan and collagen 2 mRNA, but significantly decreased push-out forces over time. Cell-loaded PGA showed significantly accelerated cell colonization and significantly extended deposition of aggrecan. Augmented chondrogenic differentiation in PGA and cartilage/PGA-interface for up to 84 days suggests initial cartilage regeneration. Due to the PGA resorbability, however, the model exhibits limitations in assessing the "lateral implant bonding".

Change in Pull-Out Force during Resorption of Magnesium Compression Screws for Osteosynthesis of Mandibular Condylar Fractures

BACKGROUND

Magnesium has been used as degradable fixation material for osteosynthesis, but it seems that mechanical strength is still a current issue in these fixations. The aim of this study was to evaluate the axial pull-out force of compression headless screws made of magnesium alloy during their resorption.

METHODS

The tests included screws made for osteosynthesis of the mandible head: 2.2 mm diameter magnesium alloy MgYREZr (42 screws) and 2.5 mm diameter polylactic-co-glycolic acid (PLGA) (42 pieces, control). The screws were resorbed in Sørensen's buffer for 2, 4, 8, 12, and 16 weeks, and force was measured as the screw was pulled out from the polyurethane block.

RESULTS

The force needed to pull the screw out was significantly higher for MgYREZr screws than for PLGA ones (p < 0.01). Within eight weeks, the pull-out force for MgYREZr significantly decreased to one third of its initial value (p < 0.01). The dynamics of this decrease were greater than those of the pull-out force for PLGA screws (p < 0.05). After these eight weeks, the values for metal and polymer screws equalized. It seems that the described reduction of force requires taking into account when using magnesium screws. This will provide more stable resorbable metallic osteosynthesis.

Comparison between resorbable plates vs. titanium plates for treatment of zygomatic fractures: a systematic review with meta-analysis

PURPOSE

To compare resorbable plates with titanium plates for the fixation of zygomatic fractures, taking into account postoperative complications.

METHODS

This systematic review followed the guidelines of PRISMA and the recommendations of the Cochrane Handbook and was registered in PROSPERO. The electronic search was performed in the Web of Science, PubMed, Virtual Health Library, and Cochrane Library databases and in the gray literature. The study selection and the data extraction were performed by three calibrated and independent researchers. The assessment of the risk of bias in the studies was performed using the Cochrane Risk of Bias Tool for clinical trials. Meta-analyses were performed using Review Manager Software version 5.3, using the Peto's Odds Ratios (PORs), and when I² > 30, the random effect model was used. The evaluation of the quality of the evidence was carried out through GRADE.

RESULTS

A total of 2651 studies were screened and only nine were included; 7 of which were used for quantitative assessment. The follow-up time for patients ranged from 6 months to 5 years. All studies showed a low risk of bias in the "incomplete outcome data" domain. The need for plate removal (POR: 0.11, 95% CI: 0.02 to 0.81, I² = 0%) and dehiscence (POR 0.12, 95% CI 0.02 to 0.63, I² = not applied) was lower for the group of patients who used resorbable plates than for titanium plates.

CONCLUSION

There was no difference in the occurrence of infection, diplopia, or paresthesia between the fixation methods. Resorbable plates showed better postoperative clinical performance.

Bioabsorbable Osteofixation Materials for Maxillofacial Bone Surgery: A Review on Polymers and Magnesium-Based Materials

Clinical application of osteofixation materials is essential in performing maxillofacial surgeries requiring rigid fixation of bone such as trauma surgery, orthognathic surgery, and skeletal reconstruction. In addition to the use of titanium plates and screws, clinical applications and attempts using bioabsorbable materials for osteofixation surgery are increasing with demands to avoid secondary surgery for the removal of plates and screws. Synthetic polymeric plates and screws were developed, reaching satisfactory physical properties comparable to those made with titanium. Although these polymeric materials are actively used in clinical practice, there remain some limitations to be improved. Due to questionable physical strength and cumbersome molding procedures, interests in resorbable metal materials for osteofixation emerged. Magnesium (Mg) gained attention again in the last decade as a new metallic alternative, and numerous animal studies to evaluate the possibility of clinical application of Mg-based materials are being conducted. Thanks to these researches and studies, vascular application of Mg-based biomaterials was successful; however, further studies are required for the clinical application of Mg-based biomaterials for osteofixation, especially in the facial skeleton. The review provides an overview of bioabsorbable osteofixation materials in maxillofacial bone surgery from polymer to Mg.

Direct incorporation of mesenchymal stem cells into a Nanofiber scaffold - in vitro and in vivo analysis

Bony defects are a common problem in musculoskeletal surgery. Replacement with autologous bone grafts is limited by availability of transplant material. Sterilized cancellous bone, while being osteoconductive, has limited osteoinductivity. Nanofiber scaffolds are currently used for several purposes due to their capability of imitating the extracellular matrix. Furthermore, they allow modification to provide functional properties. Previously we showed that electrospun nanofiber scaffolds can be used for bone tissue regeneration. While aiming to use the osteoinductive capacities of collagen type-I nanofibers we saw reduced scaffold pore sizes that limited cellular migration and thus colonization of the scaffolds. Aim of the present study was the incorporation of mesenchymal stem cells into the electrospinning process of a nanofiber scaffold to produce cell-seeded nanofiber scaffolds for bone replacement. After construction of a suitable spinning apparatus for simultaneous electrospinning and spraying with independently controllable spinning and spraying devices and extensive optimization of the spinning process, in vitro and in vivo evaluation of the resulting scaffolds was conducted. Stem cells isolated from rat femora were incorporated into PLLA (poly-l-lactide acid) and PLLA-collagen type-I nanofiber scaffolds (PLLA Col I Blend) via simultaneous electrospinning and -spraying. Metabolic activity, proliferation and osteoblastic differentiation were assessed in vitro. For in vivo evaluation scaffolds were implanted into critical size defects of the rat scull. After 4 weeks, animals were sacrificed and bone healing was analyzed using CT-scans, histological, immunhistochemical and fluorescence evaluation. Successful integration of mesenchymal stem cells into the scaffolds was achieved by iteration of spinning and spraying conditions regarding polymer solvent, spinning distance, the use of a liquid counter-electrode, electrode voltage and spinning duration. In vivo formation of bone tissue was achieved. Using a PLLA scaffold, comparable results for the cell-free and cell-seeded scaffolds were found, while the cell-seeded PLLA-collagen scaffolds showed significantly better bone formation when compared to the cell-free PLLA-collagen scaffolds. These results provide support for the future use of cell-seeded nanofiber scaffolds for large bony defects.

In-vivo histocompatibility and osteogenic potential of biodegradable PLDLA composites containing silica-based bioactive glass fiber

The purpose of this two-year study was to evaluate the histocompatibility and osteogenic properties of a composite material consisting of poly(l-co-d,l lactide) (PLDLA) and silica-based bioactive glass fibers in vivo. PLDLA and PLDLA/silica-based bioactive glass fibers pins were implanted into the erector spinae muscles and femurs of beagles. Muscle and bone tissue samples were harvested 6, 12, 16, 26, 52, 78, and 104 weeks after implantation. Histology analysis was used to assess the histocompatibility, angiogenesis, and bone-implant contact. Micro-computed tomography was used to evaluate bone formation around the pins. Immunohistochemistry and western blotting revealed the expression level of the osteogenesis-related proteins. Addition of bioactive glass was demonstrated to possess better histocompatibility and reduce the inflammatory reactions in vivo. Moreover, PLDLA/silica-based bioactive glass fibers pins were demonstrated to promote angiogenesis and increase osteogenesis-related proteins expression, and thus played a positive role in osteogenesis and osseointegration after implantation. Our findings indicated that a composite of PLDLA and silica-based bioactive glass fiber is a promising biodegradable material for clinical use.

[Alveoloplasty and the use of osteosynthesis material in the cleft lip palate]

OBJECTIVES

To compare the results of secondary alveoloplasty performed in one Hospital when osteosynthesis material was used and when the bone graft does not require this material, and relating them to factors such as gender and age.

MATERIAL AND METHODS

A retrospective study was conducted from the years 2014 to 2019 in this Hospital on the selected patients who met the inclusion criteria. Two periods of ages, period A: ages between 5-12 years (mixed secondary alveoloplasty) and period B: greater than 12 years (late secondary alveoloplasty). Autologous bone from the iliac crest or parietal calotte was used for the bone graft. The patients were divided into 2 groups: group I: patients with alveoloplasties that required osteosynthesis material. Group II: patients who did not require osteosynthesis material. Parameters evaluated: the success criteria for alveoloplasty were assessed according to the clinical parameters described by Precious. Alveoloplasty was successful if they met all the criteria of Precious in the year of intervention. Postoperative complications in both groups were evaluated. The statistical analysis was performed using the exact Fisher test for qualitative variables.

RESULTS

Alveoloplasty was successful in 89.4% of patients in group I, while it was 90.3% in group II. Alveoloplasty was successful in 87.5% of females compared to 91.17% of males. The intervention was a success in 91.48% of patients in group A, compared to 66.6% in group B. The osteosynthesis material in two patients of group I was not degraded in the annual assessment. There were no significant differences in any of the comparisons.

CONCLUSIONS

The use of osteosynthesis material does not alter the integration of the bone graft in patients that undergo alveoloplasty. Factors such as gender or age do not influence the results of the interventions.

Modelling the Mechanical and Strain Recovery Behaviour of Partially Crystalline PLA

This is a study of the modelling and prediction of strain recovery in a polylactide. Strain recovery near the glass transition temperature is the underlying mechanism for the shape memory in an amorphous polymer. The investigation is aimed at modelling such shape memory behaviour. A PLA-based copolymer is subjected to stress–strain, stress relaxation and strain recovery experiments at large strain at 60 °C just below its glass transition temperature. The material is 13% crystalline. Using published data on the mechanical properties of the crystals, finite element modelling was used to determine the effect of the crystal phase on the overall mechanical behaviour of the material, which was found to be significant. The finite element models were also used to relate the stress–strain results to the yield stress of the amorphous phase. This yield stress was found to possess strain rate dependence consistent with an Eyring process. Stress relaxation experiments were also interpreted in terms of the Eyring process, and a two-process Eyring-based model was defined that was capable of modelling strain recovery behaviour. This was essentially a model of the amorphous phase. It was shown to be capable of useful predictions of strain recovery.

Effect of Injection Molding Melt Temperatures on PLGA Craniofacial Plate Properties during In Vitro Degradation

The purpose of this article is to present mechanical and physicochemical properties during in vitro degradation of PLGA material as craniofacial plates based on different values of injection molded temperatures. Injection molded plates were submitted to in vitro degradation in a thermostat bath at 37 ± 1°C by 16 weeks. The material was removed after 15, 30, 60, and 120 days; then bending stiffness, crystallinity, molecular weights, and viscoelasticity were studied. A significant decrease of molecular weight and mechanical properties over time and a difference in FT-IR after 60 days showed faster degradation of the material in the geometry studied. DSC analysis confirmed that the crystallization occurred, especially in higher melt temperature condition. DMA analysis suggests a greater contribution of the viscous component of higher temperature than lower temperature in thermomechanical behavior. The results suggest that physical-mechanical properties of PLGA plates among degradation differ per injection molding temperatures.

Effect of Injection Molding Melt Temperatures on PLGA Craniofacial Plate Properties during In Vitro Degradation

The purpose of this article is to present mechanical and physicochemical properties during in vitro degradation of PLGA material as craniofacial plates based on different values of injection molded temperatures. Injection molded plates were submitted to in vitro degradation in a thermostat bath at 37 ± 1°C by 16 weeks. The material was removed after 15, 30, 60, and 120 days; then bending stiffness, crystallinity, molecular weights, and viscoelasticity were studied. A significant decrease of molecular weight and mechanical properties over time and a difference in FT-IR after 60 days showed faster degradation of the material in the geometry studied. DSC analysis confirmed that the crystallization occurred, especially in higher melt temperature condition. DMA analysis suggests a greater contribution of the viscous component of higher temperature than lower temperature in thermomechanical behavior. The results suggest that physical-mechanical properties of PLGA plates among degradation differ per injection molding temperatures.

The Recent Revolution in the Design and Manufacture of Cranial Implants: Modern Advancements and Future Directions

Large format (i.e., >25 cm) cranioplasty is a challenging procedure not only from a cosmesis standpoint, but also in terms of ensuring that the patient's brain will be well-protected from direct trauma. Until recently, when a patient's own cranial flap was unavailable, these goals were unattainable. Recent advances in implant computer-aided design and 3-dimensional (3-D) printing are leveraging other advances in regenerative medicine. It is now possible to 3-D-print patient-specific implants from a variety of polymer, ceramic, or metal components. A skull template may be used to design the external shape of an implant that will become well integrated in the skull, while also providing beneficial distribution of mechanical force in the event of trauma. Furthermore, an internal pore geometry can be utilized to facilitate the seeding of banked allograft cells. Implants may be cultured in a bioreactor along with recombinant growth factors to produce implants coated with bone progenitor cells and extracellular matrix that appear to the body as a graft, albeit a tissue-engineered graft. The growth factors would be left behind in the bioreactor and the graft would resorb as new host bone invades the space and is remodeled into strong bone. As we describe in this review, such advancements will lead to optimal replacement of cranial defects that are both patient-specific and regenerative.

Tissue response after implantation of pure titanium and bioresorbable screws in scapula with postoperative irradiation: an experimental study on rats

OBJECTIVE

The study focuses on the comparison of tissue reaction to titanium and bioresorbable implants with and without postoperative irradiation on an animal model.

MATERIALS AND METHODS

Thirty-nine LEW/W rats were randomly assigned to experimental or control groups. One titanium and one bioresorbable screw (poly-L-lactide [PLLA] and L- and D-lactide poly-L/D-lactide [PDLLA]) were implanted into the left scapulas of 24 rats. Half of them received 30 Gy to the operation site and the other half received 42 Gy. In the control groups, 3 rats received 30 Gy, and 6 rats received 42 Gy to the scapula area without operation; and 6 rats had implants inserted as in the experimental group, but received no postoperative irradiation. The scapulas were removed 14 or 30 days after irradiation and a histologic analysis was performed.

RESULTS

The host tissue reaction to titanium and PLLA-PDLLA screws without postoperative irradiation was of similar intensity. In irradiated animals, the inflammatory tissue reaction was more evident around the titanium screws than around the bioresorbable screws, irrespective of the radiation dose and of the time that elapsed from the irradiation. The reaction was more evident on the 14th day than on the 30th day after the last radiation dose (70 and 86 days after surgery, respectively). The intensity of the inflammatory tissue reaction, irrespective of the implant type, was more intense in the group irradiated with 42 Gy.

CONCLUSIONS

PLLA-PDLLA implants appear to cause less tissue reaction after irradiation and could be safer reconstructive devices than titanium implants for patients undergoing surgery and adjuvant radiotherapy for cancer.

Frontal cranial modeling using endocranial resorbable plate fixation in 27 consecutive plagiocephaly and trigonocephaly patients

INTRODUCTION

Premature ossification of coronal and metopic sutures is treated by fronto-orbital remodeling. Such operations require stable fixation of the reshaped cranial bones. Currently, biodegradable plating systems are used to provide sufficient stability over the time that takes for the osteotomies to ossify. Plates that are placed traditionally on the outer surface of the cranium are often palpable and even visible through the thin overlying skin, compromising the cosmetic results of these operations. Improved aesthetics could be achieved by placing the plates endocranially.

PURPOSE

This study aimed to evaluate endocranial resorbable plate fixation and its clinical and radiographic results in frontal remodeling cranioplasty for plagiocephaly and trigonocephaly patients with follow-up sufficiently long for the plates to have been completely resorbed.

METHODS

A poly(lactide-co-glycolide) (PLGA) resorbable plating system was used on the inner aspect of frontal bone in 27 patients treated for coronal and metopic craniosynostoses. The outcome was evaluated at follow-up visits. The mean follow-up was 79.2 months.

RESULTS

Three patients had complications that required reoperations. None of these complications were related to the endocranial location of the plates. There were no problems with ossification of the osteotomy sites. All but one patient's outcome was judged as good or excellent.

CONCLUSION

Placement of resorbable fixation on the endocranial surface of the calvarial bones is safe, stable, and results in satisfactory aesthetics without interfering with the ossification of the cranial bones.

3D Printable Biophotopolymers for in Vivo Bone Regeneration

The present study investigated two novel biophotopolymer classes that are chemically based on non-toxic poly (vinyl alcohol). These vinylesters and vinylcarbonates were compared to standard acrylates in vitro on MC3T3-E1 cells and in vivo in a small animal model. In vitro, both vinylester and vinylcarbonate monomers showed about tenfold less cytotoxicity when compared to acrylates (IC₅₀: 2.922 mM and 2.392 mM vs. 0.201 mM) and at least threefold higher alkaline phosphatase activity (17.038 and 18.836 vs. 5.795, measured at [10 mM]). In vivo, polymerized 3D cellular structures were implanted into the distal femoral condyle of 16 New Zealand White Rabbits and were observed for periods from 4 to 12 weeks. New bone formation and bone to implant contact was evaluated by histomorphometry at end of observation. Vinylesters showed similar rates of new bone formation but significantly less (p = 0.002) bone to implant contact, when compared to acrylates. In contrast, the implantation of vinylcarbonate based biophotopolymers led to significantly higher rates of newly formed bone (p < 0.001) and bone to implant contact (p < 0.001). Additionally, distinct signs of polymer degradation could be observed in vinylesters and vinylcarbonates by histology. We conclude, that vinylesters and vinylcarbonates are promising new biophotopolymers, that outmatch available poly(lactic acid) and (meth)acrylate based materials.

Clinical and radiographic evaluation of biodegradable bone plates in the treatment of mandibular body fractures

Background:

Many different systems are available for the treatment of fractures ranging from the heavy compression plates for mandibular reconstruction to low profile plates for mid-facial fixation, and are made either from stainless steel, titanium or vitallium. Recently, biodegradable, self-reinforced polylactide plates and screws have been used for the internal fixation of fractures of the mandible with good results.

Aim of this study:

This study evaluated clinically the biodegradable bone plates for treatment of mandibular body fracture and to evaluate bone healing during the follow-up period using digital radiography.

Materials and Methods:

Eight patients had been suffered from mandibular body fractures were treated using Inion CPS^TM bioresorbable fixation system and the healing process were followed up using digitised panoramic radiography at first week and after 1, 3 and 6 months.

Results:

Clinical examination of fractured segments revealed stable fixation across the fracture sites while visual and quantitative assessment of radiograph showed healing process was comparable with results previously reported by titanium bone plates.

Conclusion:

Open reduction and internal fixation of mandibular fractures using bioresorbable fixation system with a brief period of inter-maxillary fixation have evolved to the point where the physical properties are sufficient to withstand the post-operative loads required for fracture repair of mandibular body fractures. The foreign body reaction is a major material-related problem which requires further studies.

High strength chitosan rod prepared via LiOH/urea solvent through centrifugation induced orientation processing

High strength chitosan rod prepared via LiOH/urea solvent utilizing the unique centrifugation induced orientation method.

Strut size and surface area effects on long-term in vivo degradation in computer designed poly(L-lactic acid) three-dimensional porous scaffolds

Current developments in computer-aided design (CAD) and solid free-form fabrication (SFF) techniques enable fabrication of scaffolds with precisely designed architectures and mechanical properties. The present study demonstrates the effect of precisely designed three-dimensional scaffold architectures on in vivo degradation. Specifically, three types of porous poly(L-lactic acid) (PLLA) scaffolds with variable pore sizes, strut sizes, porosities, and surface areas fabricated by indirect SFF. In addition, one experimental group of PLLA solid cylinders was fabricated. The scaffolds and cylinders were subcutaneously implanted into mice for 6, 12 and 21 weeks. The solid cylinders exhibited a faster percentage mass loss than all porous scaffolds. Among the porous scaffolds the group with the largest strut size lost percentage mass faster than the other two groups. Strong correlations between surface area and percentage mass loss were found at 12 (R(2)=0.681) and 21 (R(2)=0.671) weeks. Scaffold porosity, however, was not significantly correlated with degradation rate. Changes in molecular weight and crystallinity also resulted in changes in the chemical structures due to degradation, and the solid cylinders had faster crystallization due to more advanced degradation than the porous scaffolds. Scaffold compressive moduli decreased with degradation, but the resulting modulus was still within the lower range of human trabecular bone even after 21 weeks. The loss in compressive moduli, however, was a complex function of both degradation and the initial scaffold architecture. This study suggests that CAD and fabrication, within a given material, can significantly influence scaffold degradation profiles.

Inflammatory response with osteolysis related to a bioabsorbable anchor in the finger: a case report

Soft tissue fixation of ligaments and tendons in the hand can be achieved by the use of metal or bioabsorbable suture anchors. Advantages of bioabsorbable suture anchors include lack of interference in magnetic resonance imaging, resorption of anchor, replacement by bone, and no need for hardware removal. However, complications of these bioabsorbable implants include inflammatory response to the material use. We present what we believe to be the first case in the hand of a poly(l-lactide-co-d,l-lacitide) suture anchor causing an inflammatory response leading to significant osteolysis 4 months postoperatively after repair of a ring finger flexor digitorum profundus avulsion. Exploration of the distal phalanx revealed an intact implant and repair, no signs of infection, and an extensive bone defect. Pathology showed chronically inflamed tissue. This case has led us to reconsider the use of bioabsorbable anchor sutures in the hand. Further research is necessary to better define the contraindications to bioabsorbable suture anchor use in the hand.

EXTENSIVE OSTEOLYSIS AFTER THE USE OF A BIOABSORBABLE SUTURE ANCHOR: CASE REPORT AND LITERATURE REVIEW

Bioabsorbable implants are very frequently used to treat rotator cuff and shoulder labrum injuries. Many researchers have observed small areas of osteolysis after treating pathological conditions of the shoulder using bioabsorbable anchors. Biological and mechanical theories have been put forward to account for the osteolysis caused by these materials. The case of a patient who was simultaneously treated for a rotator cuff lesion using the double-row technique and a Bankart lesion using bioabsorbable PLLA anchors and Fiber Wire®, and developed extensive osteolysis of the anatomical neck of the humerus, is described. Given that an anchor was used in the glenoid, and this did not present osteolysis, the hypothesis that mechanical factors are important in the etiology of this complication is raised.

Intraosseous foreign body granuloma in rotator cuff repair with bioabsorbable suture anchor

Biodegradable implants lead to problems such as cyst formation, soft-tissue inflammation, loose implant fragments or local osteolysis. This report represents the first published case of an intraosseous foreign body granuloma in the humeral head after arthroscopic rotator cuff tear fixation with a poly-L: -lactide (PLLA) suture anchor. A 48-year-old female patient presented with pain in her right shoulder. A refixation of her right supraspinatus tendon with a biodegradable suture anchor was performed 11 months ago at an external hospital. Laboratory tests showed normal values for C-reactive protein, leukocytes and the erythrocyte sedimentation rate. No signs of infection or instability were noted. The visual analogue scale (VAS) was 8, the simple shoulder test (SST) was 4 and the American shoulder and elbow surgeons score (ASES) was 44. Plain radiographs showed high lucency in the area of the tuberculum majus. MRI showed an intra- and extraosseous mass surrounded by fluid in this area. Surgical care involved arthroscopic debridement and removal of the suture anchor. Histological examination revealed a foreign body granuloma. At the 18-month follow-up the patient was nearly pain-free. The VAS was 2, SST was 10 and ASES was 88. Foreign body granulomas are a well known but rarely described complication that arises after the use of biodegradable suture anchors in shoulder surgery. Every patient presenting with shoulder pain after usage of a biodegradable fixation material should be evaluated closely. Orthopaedic surgeons should be aware of the possibility of delayed foreign body reactions, especially after using PLLA anchors.

Closing capacity of segmental radius defects in rabbits

In the research of synthetic bone graft substitutes, the relevance for bone regeneration can be confirmed in a critical-sized model. In this study the rabbit radial defect was investigated as an ingenious model of critical size, due to its defect immobilizing intact ulna. In addition, the influence of poly(DL-lactic-co-glycolic acid) (PLGA) on bone regeneration was determined. Sixteen, 4-month-old rabbits received bilateral segmental radial defects of 15 or 20 mm. The osteotomy ends were marked with small titanium pins. Half of the group received injected PLGA microparticle/carboxymethylcellulose implants. Implantation time was 12 weeks. Evaluation consisted of radiographs after surgery and sacrifice, microcomputed tomography and histology. The radiographs revealed that the created defects were significantly smaller after sacrifice. Further a number of radii showed fibrocartilaginous interposition. Both findings indicated instability of the created defect. All evaluation techniques revealed that 15 and 20 mm were not of critical size, as most defects were more or less regenerated. PLGA microparticles did not influence bone regeneration significantly. In conclusion, 15- and 20-mm radius defects in 4-month-old rabbits were not a suitable model for bone regeneration as these defects were neither critical size nor stable. PLGA-microparticle degradation did not influence bone regeneration.

Polylactide/polyglycolide copolymer in bone defect healing in humans

This pilot study aims to evaluate the healing of a large defects in the human jawbone filled with a Poly-Lactide-co-Glycolide (PLG) polymer (Fisiograft) by means of clinical, radiological and histological methods and to compare the results with those of platelet-rich plasma (PRP) clot or autologous bone (AB) fillings. Bone cysts, where previous non-surgical treatments failed to promote healing, underwent surgery. Nineteen consenting male patients were randomly split into three groups, packed with PRP, AB or PLG. A core biopsy was performed 4 and 6 months after surgery. All treated defects showed clinical, radiological and histological progresses over time. AB provided the best clinical and histological performance and PLG had overlapping outcomes; PRP filling was statistically different. Six months after surgery, bone activities were enhanced in sites treated with PLG and fairly good with PRP. Additionally, PLG showed some new lamellar formations. In conclusion, outcomes were best with AB graft, but suitable results were achieved using PLG to promote healing of severe bone defects. PLG shows only a delayed regenerative capability but does not require a secondary donor site.

Poly-L/D-lactide (PLDLA) 96/4 fibrous implants: histological evaluation in the subcutis of experimental design

Poly-L/D-lactide (PLDLA) 96/4 fibrous implants have been introduced to engineer functional fibrous constructions in situ. The current study was undertaken to evaluate the guidance of the fibrous tissue formation and the tissue reaction of porous PLDLA 96/4 scaffolds implanted in subcutaneous tissue. Three various PLDLA 96/4 knitted-mesh scaffolds (Loose, Ordinary, and Dense) were implanted subcutaneously in 32 rats, and followed-up from 3 days until 48 weeks postsurgery. Histological examination showed that PLDLA 96/4 scaffolds provided a structurally supporting element for 48 weeks. They were filled with fibrous tissue by 3 weeks. During the follow-up, loose connective tissue was organized into dense connective tissue with thick collagen bundles. At 48 weeks, no statistically significant difference was found in the amount of loose or dense connective tissue between the scaffold groups of various porosities, although the tendency for higher amounts of loose connective tissue was seen in the Loose type scaffolds. PLDLA filament diameters were 121 mum at 2 weeks, 119 mum at 24 weeks and 116 mum at 48 weeks (P = 0.03 between 2 and 48 weeks). Porous PLDLA scaffold induced fibrous tissue formation in situ. This can be exploited in engineering fibrous tissue constructs in vivo for tissue support or replacement purposes.

Tissue-engineered tear secretory system: functional lacrimal gland acinar cells cultured on matrix protein-coated substrata

Dry eye is a general term that refers to a myriad of ophthalmic disorders resulting in the inadequate wetting of the corneal surface by the tear film. Dry eyes are typically treated by the application of artificial tears. However, patients with lacrimal insufficiencies such as Stevens-Johnson syndrome, chemical and thermal injuries, or ocular cicatricial pemphigoid have very limited options because of the short duration and action of lubricating agents. As a therapeutic strategy, we are working to develop a bioengineered tear secretory system for such patients. This article describes the growth and physiological properties of purified rabbit lacrimal gland acinar cells (pLGACs) on several matrix protein-coated polymers such as silicone, collagen I, copolymers of poly-D,L-lactide-co-glycolide (PLGA; 85:15 and 50:50), poly-L-lactic acid (PLLA), and Thermanox plastic cell culture coverslips. Monolayers of acinar cells were established on all of the polymeric substrata. An assay of beta-hexosaminidase activity in the supernatant medium showed significant increases in protein secretion, following stimulation with 100 microM carbachol on matrix protein-coated and uncoated polymers such as silicone, PLGA 85:15, and PLLA. Our study demonstrates that PLLA supported the morphological and physiological properties of purified rabbit lacrimal gland epithelial cells more successfully than the others.

Effect of FGF and Polylactide Scaffolds on Calvarial Bone Healing With Growth Factor on Biodegradable Polymer Scaffolds

Repair of bone defects remains a major concern in reconstructive surgery. Synthetic biodegradable polymers have been used as scaffolds for guided bone regeneration. Fibroblast growth factors (FGFs) promote cell growth, differentiation, and tissue maintenance factors. They can stimulate the proliferation of osteogenic cells and chondrocytes, and also promote angiogenesis. Acidic and basic fibroblast growth factors (FGF-1 and FGF-2, respectively) are the best known members of this protein family. To evaluate the healing of experimental bone defects using poly-L/D-lactide (PLDLA) 96/4 scaffolds and FGF-1, 18 adult rats were operated on. A 6-mm diameter critical size defect (CSD) was made in the calvarial bone of each rat. The animals were divided into three treatment groups: 1) Neither scaffold nor FGF was used (control group); 2) scaffold only; and 3) scaffold with FGF-1. Follow-up time was eight weeks. Samples were embedded in methylmethacrylate and 5-microm thick sections from the middle of each specimen were stained with modified Masson-Goldner method. The shape and size of defects were evaluated radiologically. New bone formation was measured histologically and histomorphometrically. Radiologically, in the control group the shape of the defects changed from round to oval and edges were blunt. In the other groups the defects were round with sharp edges. Histomorphometrically, mean surface area of bone trabeculae was 1.05 mm (SD +/- 0.25) in group 1 (no implant), 1.35 mm (SD +/- 0.52) in group 2 (implant) and 0.79 mm (SD +/- 0.34) in group 3 (implant and FGF-1). Histological examinations revealed no or little osteoid in the groups 1 and 2, whereas in the group 3 samples had little or moderate new bone formation. Accordingly, no clear benefit of using knitted PLDLA scaffolds combined with FGF-1 on the healing of calvarial critical size defects in rats could be demonstrated.

Stability of Skeletal Class III Malocclusion After Combined Maxillary and Mandibular Procedures: Titanium Versus Resorbable Plates and Screws for Maxillary Fixation

PURPOSE

The aim of this study was to evaluate skeletal stability after double jaw surgery for correction of skeletal Class III malocclusion to assess if there were any differences between resorbable plate and screws and titanium rigid fixation of the maxilla.

PATIENTS AND METHODS

Twenty-two Class III patients had bilateral sagittal split osteotomy for mandibular setback stabilized with rigid internal fixation. Low level Le Fort I osteotomy for maxillary advancement was stabilized with conventional titanium plate and screws in 12 patients (group 1) and with resorbable plate and screws in 10 patients (group 2). Lateral cephalograms were taken before surgery, immediately postoperatively, 8 weeks after surgery, and 1 year postoperatively.

RESULTS

Before surgery both groups were balanced with respect to linear and angular measurements of craniofacial morphology. One year after surgery, maxillary stability was excellent in both groups. In group 1 no significant correlations were found between maxillary advancement and relapse. In group 2, significant correlations were found between maxillary advancement and relapse at A point and posterior nasal spine. No significant differences in postoperative skeletal and dental stability between groups were observed.

CONCLUSION

Surgical correction of Class III malocclusion after combined maxillary and mandibular procedures appears to be a fairly stable procedure for maxillary advancements up to 5 mm independently from the type of fixation used to stabilize the maxilla. Resorbable devices should be used with caution for bony movements of greater magnitude until their usefulness is evaluated in studies with large maxillary advancements.

Modulated release of bioactive protein from multilayered blended PLGA coatings

The objective of this study was to develop a poly(D,L-lactic-co-glycolic acid) (PLGA)-based coating system for producing biologically-inspired delivery profiles. Protein-loaded microspheres were made from PLGA (50:50) terminated with carboxylic acid groups (PLGA-2A) blended either with more hydrophobic PLGA (50:50) having lauryl ester endcaps (PLGA-LE) or with the more hydrophilic Pluronic F-127 (PF-127). Dense coatings were formed by pressure-sintering the microspheres. Altering hydrophobicity changed the water concentration within coatings, and consequently the time to onset of polymer degradation and protein release was modulated. After blending up to 8% Pluronic, degradation by-products began accumulating immediately upon incubation in saline, whereas, degradation was delayed for up to 14 days with blending of up to 30% PLGA-LE. Primary protein release peaks from one-layer coatings could be created from 7 to 20 days using 8% PF-127 or 30% PLGA-LE blends, respectively. Multilayered coatings of different blends generated several release peaks, with their temporal occurrence remaining approximately the same when layers of other hydrophobicity were added above or below. To allow design of coatings for future use, results were used to construct a model based on Fourier analysis. This polymer blend system and model can be used to mimic temporally varying profiles of protein expression.

Biocompatibility of b-Tricalcium Phosphate Root Replicas in Porcine Tooth Extraction Sockets - A Correlative Histological, Ultrastructural, and X-ray Microanalytical Pilot Study

This investigation studies porcine tissue response in tooth extraction sockets treated with root replicas made out of β-tricalcium phosphate (β-TCP; β-Ca3(PO4)2) granules, molded and held together by thermal fusion of a thin film of polyglycolic-polylactic acid copolymer. Six left mandibular third incisors (n 1/4 6) of experimental pigs are treated with the root replicas and four contralateral incisors are used as nontreated controls (n 1/4 4). Two animals each were killed at 20, 40, and 60 weeks of observation periods. The mandibular jaw segments were prepared in toto for light microscopy by resin embedding and serial ground sectioning. Additionally, one β-TCP-treated socket at 60 weeks was thoroughly investigated by correlative light, electron microscopic and electron probe X-ray microanalysis to assess the bioabsorbability and host removal of the replica material from the implant site. The extraction wounds of the animals healed satisfactorily with very little histologically observable differences in the healing pattern of the test and control sites. The β-TCP was completely removed from extracellular sites, but at 60 weeks, remnants of it were found in the cytoplasm of multinucleated giant cells. The root replicas made out of β-TCP were biocompatible and bioabsorbable. Osseous healing occurred both in the test and control sockets, but the healing process was delayed due to the presence of β-TCP particles.

Fibronectin immobilization using water-soluble carbodiimide on poly-L-lactic acid for enhancing initial fibroblast attachment

The aim of this study is to evaluate the influence of fibronectin immobilization on poly-L-lactic acid (PLA) films on the initial attachment of human gingival fibroblasts. Carboxylic acid groups are chemically introduced on the PLA films' surface by surface hydrolysis with 0.5 M NaOH. The contact angle of PLA surface with respect to double-distilled water decreases significantly after NaOH hydrolysis. X-ray photoelectron spectroscopy (XPS) also reveals significantly higher intensities of C(C=O)/C(C-O) after NaOH hydrolysis. Fibronectin is immobilized onto the hydrolyzed PLA surface through a condensation reaction between the carboxylic acid groups on the hydrolyzed PLA surface and the amino groups of fibronectin using water-soluble carbodiimide. XPS analysis shows that the fibronectin-immobilized PLA surface is enriched with nitrogen atoms. The immobilization of fibronectin significantly enhances the number of initially attached human gingival fibroblasts on the PLA surface. No obvious differences in morphology are noted between fibroblasts cultured on native PLA and on fibronectin-immobilized PLA. Fibronectin can be immobilized onto the PLA surface after NaOH hydrolysis and this is effective in enhancing the initial attachment of human gingival fibroblasts.

Les matériels d'ostéosynthèse résorbables

There is continued interest in the development of new biomaterials. The application of new implantable biomaterials requires intense research and thorough evaluation. Much time and effort has been required to overcome the risks and problems associated with the bioabsorbable devices. For surgical bone fixation, these materials were investigated since the 1960's. Different polymer properties were explored to ensure adequate strength and biocompatibility. High-molecular-weight bioabsorbable polymers were initially used, followed by addition of reinforcement materials. The most recent materials are self-reinforced, small yet strong devices. The newer generations contain bioactive substances such as antibiotics and growth factors. Bioabsorbable materials are constantly changing as we try to adopt the principles of tissue engineering. Surgeons are using new techniques to exploit these polymers and their bioabsorbable properties. It is hoped that this multidisciplinary approach of surgery and research will continue to help the further evolution of biomaterial science.

HISTOLOGIC ANALYSIS OF BIOABSORBABLE SCLERAL BUCKLING IMPLANTS

PURPOSE

To analyze histologically tissue reactions to bioabsorbable PLA96 in rabbit eyes.

METHODS

Scleral buckling operations were carried out in 48 rabbits. Two materials were used: bioabsorbable PLA96 (polylactide 96/4; L/D molar ratio 96/4) and silicone sponge. One eye of each rabbit was operated on and the other eye served as a nonoperated control. After follow-up times of 1, 3, 5, and 12 months, the rabbits were killed and the eyes enucleated for histology.

RESULTS

All rabbits recovered well. Histologically, tissue reactions were very localized; implant fragments were not seen within the sclera. The amounts of fibrous tissue and inflammatory cells (mainly macrophages) inside the implant area increased over time. One rabbit from the silicone group was killed 4 months postoperatively owing to refusal to eat. In the PLA96 group, acute or chronic infections occurred in four rabbits. The bioabsorbable implant was macroscopically easily detectable at 12 months postoperatively.

CONCLUSIONS

The PLA96 material used for scleral buckling in rabbits showed good biocompatibility. The material did not undergo biodegradation during the follow-up period of 12 months. PLA96 implants were associated with thicker fibrous tissue encapsulation and more inflammatory cells compared with silicone sponge implants.