The use of bioabsorbable osteofixation devices in craniomaxillofacial surgery

Evaluation of biodegradable synthetic scaffold coated on arterial prostheses implanted in rat subcutaneous tissue

Polyester arterial prostheses impregnated with various synthetic biodegradable materials and with gelatin were implanted subcutaneously in rats for 3-180 days. The inflammation was assessed by quantifying the activity of alkaline phosphatase and by histology. The degradation of the scaffold materials was determined by scanning electron microscopy (SEM), size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). The alkaline phosphatase activity induced by the polymer-impregnated grafts was similar to that induced by the non-impregnated controls during most of the post-implantation periods. Histological studies revealed that the acute inflammatory response was moderate to mild and was similar for all types of specimens, except for the gelatin-impregnated grafts that induced a severe acute inflammation during the first 2 weeks post-implantation. At 4 and 6 months, significant disintegration of the scaffold was observed, accompanied by enhanced tissue infiltration and a reactivation of the acute inflammatory phase. Linear and exponential degradation rates of the synthetic polymers were described. The relative degradation rates of the biodegradable polymers were ranked as following: PLLACL > PDLLA > PLLA > PCEL. In conclusion, biodegradable polymers may provide an option as sealant/scaffolding materials for vascular prosthesis. It is suggested that the degradation rate of the polymer scaffolding materials should be higher to achieve early healing while without inducing strong inflammation.

Histological study on sinus lift grafting by Fisiograft and Bio-Oss

The work aims to provide a histological investigation of Fisiograft, a PLA/PGA copolymer, used as filler for bone defects in humans. The study was performed on biopsies of sinus lifts where Bio-Oss and Fisiograft gel were applied as graft material. Bone regeneration was satisfactory in all sinus lifts, even when Fisiograft was applied alone. Due to remarkable osteoclast activity, Bio-Oss granules were cleared from the majority of biopsy cores. At histology, Fisiograft gel appeared as globes enveloped by fibroblasts, displaying an epithelial-like cell appearance. Due to its solubility in solvents, undegraded Fisiograft (recorded for 7 months or more) did not stain whereas degraded Fisiograft stained positive. The loose connective tissue, that surrounded Fisiograft and bone contained isolated mastocytes. Bone grew inside the loose connective and often reached the surface of Fisiograft by intervening cells. The results seem to indicate that Fisiograft may be considered both a polymer useful for fastening bone substitutes inside a defect and in addition a material capable of prompting bone regeneration, with or without the use of a bone substitute. In addition to space-former and space-maintainer functions, Fisiograft shows potential bone stimulation function, which may be labelled as osteopromotive capability.

PERSISTENCE OF INDENTATION WITH BIOABSORBABLE POLY-l/d-LACTIDE VERSUS SILICONE SPONGE SCLERAL BUCKLING IMPLANTS

PURPOSE

To measure the amount and duration of indentation depth achieved with biodegradable poly-L/D-lactide 96/4 (PLA96) and silicone sponge implants.

METHODS

Thirty rabbits underwent a scleral buckling procedure. A PLA96 buckling implant was used in 15 rabbits and a silicone sponge buckling implant was in 15 rabbits. A circumferential scleral buckling implant was sutured episclerally on the left eye of each rabbit, just temporal to the superior rectus muscle and 7 mm posterior to the limbus. Computed tomography was performed at 1 week, 3 months, and 5 months after surgery.

RESULTS

The PLA96 buckling implant (implant diameter, 3-3.5 mm) used in this study created lower indentation than the silicone sponge implant (implant diameter, 4 mm). The indentation created by the PLA96 implant decreased over time compared with that created by the silicone implant. There were no complications related to either kind of implant.

CONCLUSION

Both the silicone sponge implant and the PLA96 implant caused indentation that decreased in a comparable manner over the follow-up period (5 months).

Self-reinforced biodegradable plates and screws for fixation of zygomatic fractures

PURPOSE

The aim of this retrospective clinical study was to evaluate zygomatic fracture fixation with the BioSorbFX osteosynthesis system by assessing stability of reduction as well as complications in the first postoperative year and by conducting a survey to document surgeons' opinions on biodegradable osteosynthesis for this indication.

MATERIAL

From January to September 2003, 25 patients with displaced non-infected unilateral fracture of the zygoma were operated upon (m:f = 20:5; age 17-81 years; mean 39.4 years) using the BioSorbFX 2.0 and/or 1.5 mm osteosynthesis systems.

METHODS

A: Clinical and radiographic examinations were carried out immediately postoperatively and after 1, 3, 6, 9 and 12 months.

METHODS

B: Surgeons were asked to participate in a survey critically evaluating their experience with biodegradable osteosynthesis systems.

RESULTS

A: All fractures of the zygoma healed uneventfully. An excessive soft tissue reaction due to the degradation process was not seen. Three minor complications which resolved after local therapy occurred in the immediate postoperative phase.

RESULTS

B: In the survey, the handling of biodegradable plates in general was rated worse than metal plate osteosynthesis.

CONCLUSION

Fixation of fractures of the zygoma with the BioSorbFX system was simple and safe. The fixations remained stable and bony healing was uneventful. Postoperative complications were few, of a minor nature and not related to the process of biodegradation.

Engineered osteochondral grafts using biphasic composite solid free-form fabricated scaffolds

Tissue engineering has provided an alternative to traditional strategies to repair cartilage damaged by injury or degenerative disease. A successful strategy to engineer osteochondral tissue will mimic the natural contour of the articulating surface, achieve native mechanical properties and functional load-bearing ability, and lead to integration with host cartilage and underlying subchondral bone. Image-based design (IBD) and solid free-form (SFF) fabrication can be used to generate scaffolds that are load bearing and match articular geometry. The objective of this study was to utilize materials and biological factors in an integrated approach to regenerate a multitissue interface. Biphasic composite scaffolds manufactured by IBD and SFF fabrication were used to simultaneously generate bone and cartilage in discrete regions and provide for the development of a stable interface between cartilage and subchondral bone. Poly-L-lactic acid/hydroxyapatite composite scaffolds were differentially seeded with fibroblasts transduced with an adenovirus expressing bone morphogenetic protein 7 (BMP-7) in the ceramic phase and fully differentiated chondrocytes in the polymeric phase. After subcutaneous implantation into mice, the biphasic scaffolds promoted the simultaneous growth of bone, cartilage, and a mineralized interface tissue. Within the ceramic phase, the pockets of tissue generated included blood vessels, marrow stroma, and adipose tissue. This combination of IBD and SFF-fabricated biphasic scaffolds with gene and cell therapy is a promising approach to regenerate osteochondral defects.

In vivo experimental study on bone regeneration in critical bone defects using an injectable biodegradable PLA/PGA copolymer

OBJECTIVES

An assessment was done of the bone-healing rate after implantation of a polylactide/polyglycolide copolymer (PLA-PGA) 50/50 dispersed in aqueous solution of PGA and dextran, used as bone substitutes in an animal model.

STUDY DESIGN

Two groups of 5 rabbits each were used. In both the femoral condyles, a critical size defect of 6x10 mm was made. On the right side PLA/PGA was inserted; the left side remained empty. Thirty and 90 days after surgery the animals were killed.

RESULTS

Defects left unfilled showed no spontaneous healing after 30 and 90 days. Sites filled with experimental materials showed new bone ranging between 11.46% and 76.82% after 30 days, and 75.98% and 95.34% after 90 days. Histomorphometry showed an increase in bone maturation between day 30 and 90 in experimental sites. At day 90, no statistical difference was seen as compared to normal bone.

CONCLUSION

PLA/PGA copolymer dispersed in hydrosoluble matrix seems to be suitable as osteoconductive material in critical size defects.

Fixation of zygomatic fractures with a biodegradable copolymer osteosynthesis system: short- and long-term results

Biodegradable osteosynthesis devices can be viewed as addition to, not yet replacement for conventional metal osteosynthesis materials. In a series of 65 patients with zygomatic fractures, a short-term complication/sequelae rate of 22.8% and a long-term complication rate of 9.4% were recorded. Lactosorb plates, panels and screws were the only devices used for osteosynthesis. All complications associated with the biodegradable material could be considered minor and were resolved by the use of minor surgical procedures or conservative measures. The results of this study indicate that treatment of zygomatic fractures with biodegradable osteosynthesis material has no major long-term adverse effects beyond the total material resorption time.

Successful Use of Biosorb Osteofixation Devices in 165 Cranial and Maxillofacial Cases: A Multicenter Report

Bioabsorbable osteofixation devices were developed to avoid problems associated with metals. Bioabsorbable devices are mostly made of the polymers polylactide, polyglycolide, and their copolymers [polyglycolide-co-polylactide and P(L/DL)LA]. Using the technique of self-reinforcement of bioabsorbable materials, it is possible to manufacture osteofixation devices with ultra high strength. Self-reinforced polyglycolide-co-polylactide 80/20 was selected to make devices (Biosorb PDX) for this study because of its favorable degradation characteristics. The aim of this study was to evaluate the efficacy of using self-reinforced polyglycolide-co-polylactide 80/20 (Biosorb) plates and screws in the fixation of osteotomies in craniomaxillofacial surgery. In a prospective study, 165 patients (161 children and 4 adults) were operated on in four European Union centers (Paris, Innsbruck, London, and Oulu) from May 1, 1998 to January 31, 2002. Indications included correction of dyssynostotic deformities (n = 159), reconstruction of bone defects after trauma (n = 2), tumor removal (n= 2), and treatment of encephalocele (n = 2). Plates used were 0.8, 1, or 1.2 mm thick, and screws had an outer (thread) diameter of 1.5 or 2 mm and a length of 4, 6, or 8 mm. Tacks had an outer diameter of 1.5 or 2 mm and a length of 4 or 6 mm. During surgery, the devices were easy to handle and apply and provided stable fixation apart from 2 cases. Postoperative complications occurred in 12 cases (7.3%), comprising infection (n = 6), bone resorption (n = 4), diabetes insipidus (n = 1), delayed skin wound healing/skin slough (n = 2), and liquorrhea (n = 1). Accordingly, self-reinforced polyglycolide-co-polylactide 80/20 (Biosorb) plates and screws can be used safely and with a favorable outcome in corrective cranioplasties, especially in infants and young children.

Self-reinforced polylactide/polyglycolide 80/20 screws take more than 1½ years to resorb in rabbit cranial bone

The aim of this study was to assess tissue reactions to bioabsorbable self-reinforced polylactide/polyglycolide (SR-PLGA) 80/20 miniscrews in rabbit cranial bone. One PLGA screw was implanted on one side and one titanium screw on the other side of the sagittal suture (n = 21). Three animals were sacrificed after 2, 4, 8, 16, 24, 54, and 72 weeks. In histological examination the numbers of macrophages, giant cells, active osteoblasts, and fibrous tissue layers were assessed and degradation of the bioabsorbable screws was evaluated. After 2 weeks, macrophages were seen near the heads of both screws. After 4 and 8 weeks, the bioabsorbable screws were surrounded by fibrous tissue. Osteoblastic activity and groups of several giant cells were seen. After 24 weeks, a significant change in the morphology of the PLGA screws had occurred. Osteoblastic activity and the amount of giant cells had decreased. After 1 year, some PLGA biomaterial was still present. PLGA screws had been replaced by adipose tissue, fibrous tissue, and "foamy macrophages" that had PLGA particles inside them. After 1(1/2) years, the amount of biomaterial remaining had decreased remarkably. The particles of biomaterial were inside foamy macrophages. SR-PLGA 80/20 screws are biocompatible and have no clinically manifested complications when used in the cranial bone of rabbits. No contraindications as regards their clinical use in craniofacial surgery was found when these screws were studied in the cranial bones of rabbits.

Comparison of miniplates and reconstruction plates in mandibular reconstruction

BACKGROUND

The aim of this study is to compare complication rates of miniplates versus reconstruction plates in the fixation of vascularized grafts into segmental mandibular defects.

METHODS

Retrospective analysis of 143 consecutive successful microvascular composite flaps performed between 1993 and 2001 was performed. Data were gathered from a computerized database, case notes and pathology reports. Complications were classified as dehiscence, infection, plate or bone removal.

RESULTS

In the series, 49% of patients received miniplates, and 51% received plates. No significant differences in complication rates were found between those grafts fixed with miniplates (27%) and those with reconstruction plates (30%). Plate choice was primarily determined by consultant preference. No significant differences were found in patient, defect, treatment, or follow-up characteristics between the plate groups. Twenty-nine percent of patients had at least one late complication at the reconstructed site, and this was higher (39%) in those who had postoperative radiotherapy.

CONCLUSIONS

No evidence was found in this study that the increased rigidity offered by reconstruction plates influences the rate of plate or bone removal, infection, or plate exposure. Thus, the decision to use reconstruction or miniplates is not dependent on the rate of plate complications.