Fixation of mandibular body osteotomies using biodegradable amorphous self-reinforced (70L:30DL) polylactide or metal lag screws: an experimental study in sheep

Biomaterials-aided mandibular reconstruction using in vivo bioreactors

Large mandibular defects are clinically challenging to reconstruct due to the complex anatomy of the jaw and the limited availability of appropriate tissue for repair. We envision leveraging current advances in fabrication and biomaterials to create implantable devices that generate bone within the patients themselves suitable for their own specific anatomical pathology. The in vivo bioreactor strategy facilitates the generation of large autologous vascularized bony tissue of customized geometry without the addition of exogenous growth factors or cells. To translate this technology, we investigated its success in reconstructing a mandibular defect of physiologically relevant size in sheep. We fabricated and implanted 3D-printed in vivo bioreactors against rib periosteum and utilized biomaterial-based space maintenance to preserve the native anatomical mandibular structure in the defect site before reconstruction. Nine weeks after bioreactor implantation, the ovine mandibles were repaired with the autologous bony tissue generated from the in vivo bioreactors. We evaluated tissues generated in bioreactors by radiographic, histological, mechanical, and biomolecular assays and repaired mandibles by radiographic and histological assays. Biomaterial-aided mandibular reconstruction was successful in a large superior marginal defect in five of six (83%) sheep. Given that these studies utilized clinically available biomaterials, such as bone cement and ceramic particles, this strategy is designed for rapid human translation to improve outcomes in patients with large mandibular defects.

Comparison of Different Fixation Types Used in Unilateral Mandibular Condylar Fractures: An In Vivo Study With New Biomechanical Model

INTRODUCTION

The aim of this in vivo study is to compare the single-titanium, double-titanium mini plate, and single resorbable plate systems used in internal rigid fixation of the unilateral mandibular condylar fractures on new design biomechanical model.

METHODS

Thirty synthetic polyurethane models were used for biomechanical testing. Fracture lines were created for each model. Fragments were fixed with single-titanium plates in Group A (n = 10), double-titanium plates in Group B (n = 10), and single biodegradable plate (PPLA) in Group C (n = 10). Masticatory forces were applied to the models and the biomechanical properties of the titanium plate and screws, resorbable plate, and screws were evaluated.

RESULTS

The average failure force for Group A, Group B, and Group C is 199, 324, 177N and the average bone displacement for Group A, Group B, Group C is 1.9, 0.3, 2.1 mm, respectively.

DISCUSSION

Double titanium plates showed the most acceptable results in the fixation of unilateral subcondylar fractures where the single titanium and biodegradable plate systems failed to provide enough stability in unilateral subcondylar fracture fixation. Biodegradable plate systems are still not an alternative in fixation of unilateral condylar fractures.

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.

Facile synthesis and comparative study of poly(l-lactide) with linear-comb and star-comb architecture

The crystallization ability of PLLA with different chain structures.

Comparison of resorbable plates and titanium plates for fixation stability of combined mandibular symphysis and angle fractures

OBJECTIVES

We compared resorbable plates with titanium plates for treatment of combined mandibular angle and symphyseal fractures.

MATERIALS AND METHODS

Patients with mandibular angle and symphysis fractures were divided into two groups. The control (T) group received titanium plates while the experimental (R) group received resorbable plates. All procedures were carried out under general anesthesia using standard surgical techniques. We compared the frequency of wound dehiscence, development of infection, malocclusion, malunion, screw breakage, and any other technical difficulties between the two groups.

RESULTS

Thirteen patients were included in the R group, where 39 resorbable plates were applied. The T group consisted of 16 patients who received 48 titanium plates. The mean age in the R and T groups was 28.29 and 24.23 years, respectively. Primary healing of the fractured mandible was obtained in all patients in both groups. Postoperative complications were minor and transient. Moreover, there were no significant differences in the rates of various complications between the two groups. Breakage of 3 screws during the perioperative period was seen in the R group, while no screws or plates were broken in the T group.

CONCLUSION

Resorbable plates can be used to stabilize combined mandibular angle and symphysis fractures.

Resorbable plates for the fixation of mandibular fractures: a prospective study

PURPOSE

The hypothesis for this prospective evaluation is that resorbable plates are equal to the performance of titanium 2-mm plates, regarding healing of the fracture with bone union and restoration of function. To prove this hypothesis, specific end points will be compared with literature norms for titanium 2-mm miniplate rigid fixation. The primary end point variable for this analysis is the union of the fracture and return to normal function. Secondary end point variables included the incidence of complications such as infection, malunion with malocclusion, soft tissue dehiscence, the need for revision surgery, specific technical challenges, operative time, and the learning curve for the surgeon.

PATIENTS AND METHODS

This prospective study consisted of a sequential enrollment of 50 fractures that met the inclusion criteria of having a fracture of the mandibular body, symphysis, angle, or ramus, and required an open reduction and internal fixation for stabilization and repair. The resorbable plates and screws used consisted of an amorphous injection molded copolymer of L-lactide/D-lactide/trimethylene carbonate (Inion CPS system, Tampere, Finland). Data were collated and compared with literature norms for titanium plates and also compared with nonrigid fixation data from a prospective study performed on a similar population in the same institution.

RESULTS

Clinical and radiographic evaluation indicated union of all fractures at the eighth follow-up visit. Three sites (6%) noted to have clinical signs of infection were treated immediately upon presentation, with fracture union by 8 weeks. There was no need for revision surgery in this series of patients; 12 screw heads fractured during screw placement and were immediately replaced without significant fracture sequelae.

CONCLUSION

Based on this limited series of patients, the hypothesis formulated for this study was validated.

Bioabsorbable screw fixation for the treatment of ankle fractures

BACKGROUND

Self-reinforced poly(L/dL)lactide 70:30 (SR-PLA70) retains its strength in bone for 24 weeks, whereas self-reinforced poly-L-lactide (SR-PLLA) retains its strength for over 36 weeks. In this prospective randomized study, bioabsorbable 4.5-mm SR-PLA70 screws were compared with SR-PLLA screws in the treatment of displaced ankle fractures in adults.

METHODS

Sixty-two patients with ankle fractures needing operative treatment were randomized into two groups. Comminuted fractures needing plating were excluded. In total 54 of 62 patients were followed up for 1 year by clinical evaluation, radiographs, and Olerud-Molander score.

RESULTS

The study groups differed significantly only in the mean duration of sick leave (SR-PLA70, 60 days; SR-PLLA, 65 days; P = 0.02). At the 1-year follow-up, syndesmotic ossification was more common in the SR-PLA70 group (5 versus 1 patient, not significant). Radiologically, the screw channel had not disappeared in any of the patients by the 1-year follow-up.

CONCLUSIONS

Both implant types proved to have good biocompatibility. SR-PLA70 and SR-PLLA screws are suitable in selected cases for the fixation of ankle fractures, but the mechanical stability of the fixation has to be carefully monitored perioperatively.

Skeletal Stability in Bimaxillary Orthognathic Surgery: P(L/DL)LA-Resorbable versus Titanium Osteofixation

BACKGROUND

One-year skeletal stability following bimaxillary orthognathic surgery was assessed by comparing poly(L-lactide-co-DL-lactide) to titanium osteofixation.

METHODS

Thirty patients underwent osteofixation with poly(L-lactide-co-DL-lactide) copolymer and 30 had 2.0-mm titanium-miniplate osteosyntheses. Lateral cephalograms were analyzed preoperatively, postoperatively, and at 1-year follow-up. Average +/- SD values were as follows in resorbable plate-osteosyntheses (number of cases/titanium controls): for maxillary advancement, 3.5 +/- 4.1 mm (n = 19)/5.4 +/- 3.5 mm (n = 21); setback, 2.8 +/- 3.7 mm (n = 9)/1.9 +/- 1.8 mm (n = 8); elongation, 4.2 +/- 3.6 mm (n = 18)/3.7 +/- 5.2 mm (n = 14); and intrusion, 1.9 +/- 1.7 mm (n = 12)/3.3 +/- 2.7 mm (n = 13); for mandibular advancement, 4.6 +/- 3.6 mm (n = 10)/6.3 +/- 8.8 mm (n = 18); setback, 7.5 +/- 8.3 mm (n = 20)/7.2 +/- 3.2 mm (n = 12); enlargement of the mandibular angle, 11.8 +/- 9.9 degrees (n = 19)/7.9 +/- 6.6 degrees (n = 21); and reduction, 4.5 +/- 3.2 degrees (n = 9)/6.3 +/- 6.6 degrees (n = 9).

RESULTS

Preoperative to postoperative landmark positions within the study and control groups differed highly significantly (p = 0.008, paired t test), yet the amount of operative movement was comparable between the study and control groups (p = 0.5, two-sided t test). Absolute instability at the advanced A-point was (study group/controls) 2.3 +/- 1.8/2.4 +/- 2 mm, setback was 2.3 +/- 1.9 mm/2.5 +/- 1.7 mm, elongation at the anterior nasal spine was 3.8 +/- 3.1 mm/3.1 +/- 3.6 mm, intrusion was 2.1 +/- 1.9 mm/2.2 +/- 1.5 mm, advancement instability at the B-point was 4.9 +/- 4.3 mm/5.1 +/- 8.2 mm, setback was 3.0 +/- 2 mm/1.7 +/- 2 mm, mandibular angle enlargement instability was 6.7 +/- 8.9 degrees/8.2 +/- 9.6 degrees, and angle narrowing was 6.8 +/- 5.2 degrees/4.2 +/- 5.9 degrees. Absolute postoperative instability did not differ significantly between the study and control groups (p = 0.6).

CONCLUSIONS

Resorbable osteofixation as tested proved to be as reliable as titanium, but as the study and control groups were not matched, the results have to be interpreted as preliminary. Resorbable materials permitted clinically faster occlusal and condylar settling than standard titanium osteosyntheses, as bone segments showed slight clinical mobility up to 6 weeks postoperatively.

Indications and limitations in resorbable P(L70/30DL)LA osteosyntheses of displaced mandibular fractures in 4.5-year follow-up

BACKGROUND

This study evaluates prospective 4.5-year follow-up of available poly(l-lactide-co-dl-lactide) [P(L70/30DL)LA] resorbable plate osteosyntheses in displaced traumatic and pathological mandibular fractures.

METHODS

P(L70/30DL)LA miniplates and screws were used to fixate 50 displaced fractures in 30 patients, aged 1 to 83 years, with their informed consent. There were 15 traumatic paramedian, seven corpus, 11 angle, and 10 condyle fractures, and seven pathological fractures due to atrophy, osteomyelitis, or third molar osteotomy. Double osteosyntheses were preferred, with one monocortical plate at the dentoalveolar basis (6-mm screws) and a second plate at the inferior margin (8-mm screws).

RESULTS

The average follow-up was 31 months (range, 6 to 53 months). Fifteen (100 percent) traumatic paramedian, seven (100 percent) corpus, 10 (91 percent) angle, 10 (100 percent) condylar, and three (43 percent) pathological fractures healed primarily. Two mandibular angle fractures, traumatic and pathological, each initially healed, but 6 weeks postoperatively the first fracture re-dislocated on removal of a dental impression by the family dentist, and the second re-dislocated after mastication of hard food. One atrophic corpus fracture developed a rigid fibrous union in an 83-year-old patient; a preexistent osteomyelitis and fracture progressed to further bone loss and finally required preformed fibula reconstruction.

CONCLUSIONS

Use of the tested resorbable plates can be encouraged in multiple displaced mandibular fractures in children and likewise in highly compliant dentate adolescents and adults with doubled osteosyntheses; traumatic mandibular angle and pathological fractures, however, remain critical for nonunion. These necessitate evaluation with future smaller, more rigid, and, it is hoped, more economical fixations.

A retrospective evaluation of rigid fixation in orthognathic surgery using a biodegradable self-reinforced (70L:30DL) polyactide

OBJECTIVE

This study was designed to evaluate clinical and radiological evidence of osteotomy site healing in orthognathic surgery after rigid fixation using a biodegradable plating system.

STUDY DESIGN

A follow up of 30 patients who underwent orthognathic surgery using a biodegradable self-reinforced (70L:30DL) polylactide plating system was presented. The follow-up schedule for all patients consisted of regular appointments at 1-180 days after surgery. Clinical evaluation involved notation of any abnormal swelling, infection, discoloration, or discharge at the osteotomy sites. Stability was evaluated by manual palpation. For radiographic evaluation, panoramic radiographs were taken immediately after surgery, and again at 7-180 days. The radiographs were analyzed for any visual changes in osteotomy fragments, resorptive changes in osteotomy fragments, callus formation, and union of the osteotomy segments.

RESULTS

No clinical complications and no radiological changes in the osteotomy sites were observed. Regarding the clinical usefulness of the biodegradable fixation system, fixation at the time of operation was considered as excellent in all 30 cases.

CONCLUSIONS

The conclusions of this study were that self-reinforced (70L:30DL) polylactide was considered to be comparable to other forms of rigid internal fixation for orthognathic surgery.

Are there any complications with bioabsorbable fixation devices? A 10 year review in orthognathic surgery

Bioabsorbable fixation devices have been used in our departments between November 1991 and November 2001 in orthognathic surgery. The aim of this retrospective study was to assess all complications experienced during this time period, when we have operated 163 patients who have undergone 329 orthognathic osteotomies fixated with bioresorbable devices. No postoperative intermaxillary fixation was used. Light guiding elastics were used for 5 to 7 weeks. Patients' acceptance was generally excellent and very few complications occurred during this follow-up of 10 years. The complications were minor and did not affect the end results of the operations. Minor complications occurred in 14 patients (8.6%). Only one patient (0.6%) had a postoperative infection with elevated infection parameters. The other minor complications consisted mainly of dehiscence of the wound and plate exposure together with granulation tissue in the operation field. The rest of the complications occurred in the beginning of our study, when large screw heads on top of the bone irritated the patient and had to be removed. Insufficient fixation resulted in open bite in three patients (1.8%) in the beginning of the trial use of new devices, which no longer are used. Based on our experience, bioresorbable devices are safe to be used in orthognathic procedures. However, there is a learning curve, as there is with all new methods introduced.

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 bioresorbable poly-L/DL-Lactide [SR-P(L/DL)LA] 70/30 miniplates and miniscrews are reliable for fixation of anterior mandibular fractures: A pilot study

OBJECTIVE

Bioresorbable osteofixation devices are being increasingly used in orthognathic surgery and in cases of trauma to avoid problems associated with conventional metal osteofixation devices. The aim of this clinical study was to assess the reliability and efficacy of bioresorbable self-reinforced poly-L/DL-lactide (SR-P(L/DL)LA 70/30) plates and screws in the fixation of mandibular fractures in adults.

STUDY DESIGN

Ten patients (20 to 49 years old) with isolated anterior mandibular parasymphyseal fractures were treated by means of open reduction and internal fixation using SR-P(L/DL)LA 70/30 bioresorbable plates and screws.

RESULTS

During the minimum of 6 months of follow-up, no problems were encountered except for 1 case where a plate became exposed intraorally and infected. This required debridement and later excision of the exposed part of the plate. Despite this setback the fractured bone healed well.

CONCLUSIONS

SR-P(L/DL)LA 70/30 plates and screws are reliable for internal fixation of anterior mandibular fractures in adults. Proper soft tissue coverage should be ensured to avoid plate exposure. Should implant exposure occur, it might be necessary to excise the exposed part after fracture healing (6-8 weeks postoperatively).

Evaluation of the bending strength of rigid internal fixation with absorbable and metallic screws in mandibular ramus sagittal split osteotomy: in vitro study

The aim of this study was to evaluate, in vitro, the bending strength of internal fixation with absorbable and metallic screws in mandibular ramus sagittal split osteotomy in sheep hemimandibles. The screws were inserted as lag screws, with an inverted "L" configuration, and the set was submitted to bending strength tests. The load and displacement of the peak and final load averages were, respectively, 18.45 kgf, 8.19 mm and 14.38 kgf for Group I, and 16.67 kgf, 6.73 mm and 13.98 kgf for Group II. The results were submitted to statistical analysis by Student’s t test and by the Pearson correlation analysis. The groups showed no statistically significant differences, indicating the feasibility of both for osteosynthesis in mandibular ramus sagittal split osteotomies.

Resorbable plate osteosynthesis of sagittal split osteotomies with major bone movement

This study evaluates resorbable miniplate osteosyntheses in sagittal split osteotomies with major bone repositioning. Two resorbable 2.0-mm miniplate systems, MacroSorb (Macropore, San Diego, Calif.) and PolyMax (Synthes, Oberdorf, Switzerland), were compared consecutively. Amorphous 70:30 poly-L/DL-lactide copolymer plates sustain continuous hydrolysis through water penetration into the implant body during the first 6 months in situ. This breaks copolymer chains into smaller particles, which later become degraded through phagocytotic cells. Eighteen patients, 10 women and eight men, 16 to 57 years old (average, 27 years) were examined. They had severe dysgnathia caused by congenital craniofacial malformations, systemic disorders, trauma, amelogenesis imperfecta, oligodontia, and other conditions, and they needed five 8- to 10-mm and 13 major 10- to 12-mm repositions. Twelve sagittal split osteotomies were fixed with 12 MacroSorb plates in six patients, and 24 osteotomies were filled with 32 PolyMax plates in 12 patients. Ten mandibular plate, screw, hard-tissue, and soft-tissue specimens were taken at 3, 6, 9, or 12 months postoperatively in secondary operations (e.g., dental implant placement).Follow-up ranged from 4 to 19 months; all osteosyntheses reossified. Four patients showed proximal fragments rotated up to 5 mm sagittally anteriorly and nonaligned burr holes on the postoperative radiogram, suggesting plate fractures or screw pullout. When plate fracture was noted, guided occlusion was maintained 4 weeks after surgery. Occlusal, radiologic, and skeletal results remained stable. After starting fixation with two plates on each side, no more plate fractures were seen. In three other patients, minor skeletal relapses up to 3 mm horizontally resulted. Local histologic inspection of specimens showed thorough osseous union. Screw remnants embedded in bone made screw pullout unlikely; rather, screw-head or plate fractures were found as multiple degraded particles. Microscopy showed a chronic foreign body reaction. Two patients (11 percent) developed a sterile fistula 3 and 4 months after surgery, draining implant debris. Here, the biopsies showed a granulocytic infiltrate that subsided clinically after excisional biopsy. The assignment of MacroSorb plates followed by PolyMax plates was done in an otherwise unchanged treatment protocol. Comparison of the number of patients in each group with stable osteosyntheses and regular healing showed no significant differences by Fisher's exact test (p = 0.1516); therefore, the authors focused on the combined results for both treatments. The current osteosynthesis systems showed sufficient stability for mandibular fixation after sagittal split osteotomy and repositioning more than 10 mm distant when two plates were applied to each side; however, 27 percent of patients had complications, including relapses. Disadvantages were the cost, breakability, diameter, and need to place the screws vertically to the plate, necessitating a bent instrument or transbuccal incisions.

Holding power of bioabsorbable self-reinforced poly-L/DL-lactide 70/30 tacks and miniscrews in human cadaver bone

Several bioabsorbable internal fixation systems are currently in use in the field of bone surgery. To test the mechanical properties of recently developed amorphous self-reinforced poly-L/DL-lactide [SR-P(L/DL)LA] 70/30 tacks in comparison with commercially available SR-P(L/DL)LA 70/30 (BioSorbFX; Bionx Implants Ltd) miniscrews, SR-P(L/DL)LA miniscrews (length = 6.0 mm, core diameter = 1.5 mm, thread diameter = 2.0 mm) and tacks (length = 5.4 mm, core diameter = 1.5 mm, thread diameter = 2.0 mm) were applied to human cadaveric metatarsal (MT) bones (6 pairs of fourth MT bones and 6 pairs of fifth MT bones from donors who were from 29 to 56 years of age at the time of death). Pullout force was measured using a mechanical testing machine. Forty-eight pullout tests were carried out for each implant type. The Student test, Mann-Whitney test, and Spearman coefficient were used for statistical evaluation. The pullout force of tacks was 135.0 +/- 26.1 N, and that of the miniscrews was 119.3 +/- 26.1 N ( = 0.04, statistically significant difference). Accordingly novel SR-P(L/DL)LA 70/30 tacks have a statistically better pullout strength than the SR-P(L/DL)LA 70/30 miniscrews when tested in cadaver MT bones.

Resorbable plate osteosynthesis of dislocated or pathological mandibular fractures: a prospective clinical trial of two amorphous L-/DL-lactide copolymer 2-mm miniplate systems

The purpose of this study was to evaluate the indication for resorbable miniplates in traumatic and pathological mandibular fractures. Two resorbable miniplate systems, the 2.0-mm MacroSorb (Macropore, San Diego, Calif.) and the PolyMax (Synthes, Oberdorf, Switzerland), were prospectively used in 24 mandibular osteosyntheses. Made from amorphous 70:30 poly-L/DL-lactide, amorphous copolymer plates have not yet been evaluated for mandibular osteosyntheses. The main advantage of the amorphous copolymer-structure is continuous hydrolysis through water penetration into the implant body during the first 6 months. Hydrolysis breaks the copolymer chains into smaller particles that later become degraded through phagocytotic cells. Twelve patients, aged 13 to 83 years, were treated after providing informed consent. Fourteen dentate patients with moderately dislocated traumatic fractures and two edentulous atrophic and dislocated traumatic mandibular fractures were treated. Two patients with pathological fractures due to osteomyelitis received osteosynthesis after sequestrectomy. Histological specimens of the plates, screws, and surrounding soft tissues were taken after 3, 6, 9, and 12 months in secondary dental implant operations. A total of 22 osteosyntheses healed well without clinical or radiological signs of dislocation, insufficient or excess formation of callus, pseudarthrosis, or plate fracture. The follow-up time ranged from 4 to 22 months. One patient with osteomyelitis worsened because of widespread osseous infection, and one with atrophic fracture developed a bland fibrous pseudarthrosis. The histological specimens showed a moderate inflammatory foreign body reaction. No sinuous drainage or clinically apparent inflammation occurred. The presented osteosynthesis systems showed reliable stability for mandibular osteosynthesis in cooperative patients; however, two treatment failures occurred (8 percent). Disadvantages of the resorbable osteosyntheses were costs, greater diameter, screw breakage, and the need to place the screws vertically to the plate. The use of resorbable osteosyntheses in dislocated fractures should be further evaluated in controlled studies.

The effects of low-intensity pulsed ultrasound on bioabsorbable self-reinforced poly L-lactide screws

The effects of low-intensity pulsed ultrasound on the mechanical and molecular properties of self-reinforced poly L-lactide (SR-PLLA) screws were studied in vitro. SR-PLLA screws of 4.5 mm diameter were exposed on low-intensity ultrasound for 1, 3. 6, 9, and 12 weeks. After exposure, the bending strength, shear strength, and molecular weight were investigated. There were no differences in the investigated properties between the ultrasound exposure and control groups. We found no evidence that low-intensity ultrasound has any effect on the mechanical or molecular properties of SR-PLLA screws in vitro. The present results suggest that biodegradable SR-PLLA fixation devices are compatible with low-intensity ultrasound in vitro.

The use of bioabsorbable osteofixation devices in craniomaxillofacial surgery

Because of problems associated with the conventional osteofixation devices used in craniomaxillofacial surgery, bioabsorbable devices have presented an appealing alternative. Devices made of the polymers polyglycolide (PGA) and polylactide (PLA) and their copolymers (PLGA and PLDLA) are currently the most commonly used. Strong implants can be manufactured from these polymers with a self-reinforcing technique and used in the treatment of fractures and osteotomies. Self-reinforced devices have been studied for nearly 2 decades by our multidisciplinary research group for internal fixation of the bone in both experimental and clinical settings. In craniomaxillofacial fractures and osteotomies they have been used for as long as 10 years with no significant clinical problems. Because of more favored degradation characteristics, currently the copolymer devices (PLDLA and PLGA) represent the advancing front in the application of absorbable devices in craniomaxillofacial surgery. By using bioabsorbable devices, several problems associated with conventional biostable devices can be avoided, especially in children. New techniques that are not possible with biostable devices can be developed by using bioabsorbable devices, too. Our experience with and research on self-reinforced devices are shared here.

Mandibular, sagittal split osteotomies fixed with biodegradable or titanium screws: a prospective, comparative study of postoperative stability

OBJECTIVE

Comparison of skeletal stability following bilateral sagittal split osteotomy (BSSO) advancement of the mandible fixed with titanium or biodegradable bicortical screws.

STUDY DESIGN

Forty consecutive patients underwent mandibular advancement by means of BSSO performed with a standardized technique. In 20 patients rigid fixation was achieved by means of titanium bicortical screws; the other 20 patients were fixed with biodegradable copolymer screws made of poly-L-lactic acid (82%) and polyglycolic acid (18%). Lateral cephalograms were obtained 1 week preoperatively, 1 week postoperatively and after a minimum of 6 months postoperatively. Relevant skeletal points were traced and digitized to evaluate 2-dimensional skeletal change. Changes at each time point were analyzed and compared statistically.

RESULTS

There was no statistically significant difference in long-term stability between the 2 groups. No clinical or radiographic evidence of wound healing problems were noted.

CONCLUSION

Resorbable poly-L-lactic/polyglycolic acid copolymer bicortical screw fixation of a BSSO is a viable alternative to titanium screws for the fixation of advancement BSSO.

Holding power of bioabsorbable ciprofloxacin-containing self-reinforced poly-L/DL-lactide 70/30 bioactive glass 13 miniscrews in human cadaver bone

Antibiotics-plus bioactive glass-containing bioabsorbable self-reinforced (SR) polylactide screws have been developed for antibacterial osteoconductive bone fixation. The aim of the present study was to test the pullout properties of these recently developed miniscrews. Ciprofloxacin-plus bioactive glass-containing SR-polylactide miniscrews (BC) were compared with miniscrews made of neat SR-polylactide (A), SR-polylactide with bioactive glass (B), and ciprofloxacin-containing SR-polylactide (C). BC miniscrews and their controls (A, B, C) (all of length 6.0 mm, core diameter 1.45 mm, thread diameter 2.0 mm) were applied to one pair of cadaveric fibulae. Pullout force was measured using a materials testing machine. We carried out 49-50 pullout tests for each implant type. The Mann-Whitney test and Student's t-test were used for statistical evaluation. The pullout force for BC miniscrews was 114.9 +/- 34.0 (SD) N. Pullout forces for control miniscrews were 162.7 +/- 37.8 N (A), 99.1 +/- 16.2 N (B), and 142.9 +/- 26.9 N (C). Differences between the four groups were statistically significant (p < 0.001). Ciprofloxacin-plus bioactive glass-containing polylactide miniscrews have good holding power to human cadaver fibulae. However, adding bioactive glass and ciprofloxacin components to neat SR-polylactide results in lower pullout values.

Developments in craniomaxillofacial surgery: use of self-reinforced bioabsorbable osteofixation devices

Because of the problems associated with the conventional osteofixation devices used in craniomaxillofacial surgery, absorbable devices present an appealing alternative. Devices made of the polymers polylactide, polyglycolide, and their copolymers (PLGA and P[L/DL]LA) are currently the most commonly used. Ultrahigh-strength implants can be manufactured from these polymers with the self-reinforcing technique. Over the authors' almost two decades of study, both in experimental and clinical settings, self-reinforced devices have proved to be biocompatible, easy to handle, and mechanically strong, even for the fixation of femoral neck fractures. In craniomaxillofacial surgery, the authors have used self-reinforced devices for over 8 years without complications. Because of the more favored degradation characteristics, currently the copolymeric self-reinforced devices (P[L/DL]LA, Biosorb FX and PLGA, Biosorb PDX; Elite Performance Technologies, Solana Beach, Calif.) represent the advancing front in the application of absorbable devices in craniomaxillofacial surgery. The authors' share their experience and their studies of self-reinforced devices, which possess the highest strength and ductility of all bioabsorbable products.

Comparison of strength properties of poly-L/D-lactide (PLDLA) 96/4 and polyglyconate (Maxon) sutures: in vitro, in the subcutis, and in the achilles tendon of rabbits

Achilles tendon rupture is a common injury. Absorbable sutures are not commonly used because of their limited strength properties. Recently, sutures with prolonged strength retention properties have been developed. The aim of the study is to test the mechanical properties of recently developed poly-L/D-lactide (PLDLA) sutures in comparison with polyglyconate (Maxon) sutures. PLDLA (0.2 mm thick) and Maxon (4.0) sutures were studied in vitro by immersion in a buffered saline solution (pH 7.4). Tensile strength tests were done on sutures retrieved after 1-26 weeks. In vivo, they were implanted in the subcutis of 32 rabbits. Tensile strength tests were done on sutures retrieved after 1-6 weeks. The sutures were also used to repair the Achilles tendon in rabbits. Maximum force before breaking and percentage elongation of tendons were determined. Although PLDLA had a lower initial tensile strength than Maxon, PLDLA showed more prolonged tensile strength retention than Maxon. Tendons repaired with PLDLA, however, had a lower strength than Maxon-repaired tendons at six weeks (insignificant difference). PLDLA has more prolonged tensile strength properties compared with Maxon. Thus, PLDLA offers an alternative to Maxon in repair of the Achilles tendon.

Intramedullary fixation of cortical bone osteotomies with absorbable self-reinforced fibrillated poly-96L/4D-lactide (SR-PLA96) rods in rabbits

Osteotomies of the femoral diaphysis were fixed with absorbable self-reinforced fibrillated poly-96L/4D-lactide (SR-PLA96) intramedullary rods (4.5 mm x 50-60 mm) in 43 adult rabbits. Follow-up times varied from 3 weeks to 3 yr. After sacrifice histological, oxytetracycline-fluorescence and microradiographic studies of the bones were performed. Strength characteristics and changes in crystallinity and molecular weight of the rods were also measured. All osteotomies were evaluated radiographically. Thirty-six osteotomies (84%) healed uneventfully. The implant disappeared almost totally within 3 yr and histology showed only a minor foreign body reaction. From 6 weeks on, the bending force needed to break the osteotomy was comparable to the bending force needed to break the control bone. The shear strength of the rods displayed only minor changes for the first 24 weeks. Subsequently, the rods rapidly lost their strength and at 48 weeks there was practically no shear strength left, which is ideal for healing of an osteotomy. The present investigation demonstrated, that absorbable. fibrillated SR-PLA96-rods can be used for the intramedullar fixation of simple cortical bone osteotomies in rabbits. These results have encouraged us to continue our studies with the fixation of experimental cortical bone osteotomies in larger species.

The foreign body reaction to a biodegradable biomaterial differs between rats and mice

Before a biomaterial can be applied in the clinic, biocompatibility must be tested in in vivo models, by monitoring the foreign body reaction. In this study, we compared the foreign body reaction (FBR) to the biodegradable biomaterial hexamethylenediisocyanate crosslinked dermal sheep collagen (HDSC) between several strains of rats and mice. HDSC disks were implanted subcutaneously on the backs of AO, BN, F344, LEW, and PVG rats and on the backs of 129 SVEV, BALB/c, and C57BL/6 mice. Materials were explanted after 7, 14, 21, and 28 days and processed for (immuno) light and transmission electron microscopic evaluation. In all rat strains, giant cell formation and phagocytosis of HDSC bundles were comparable. In addition, in the PVG rat, many plasma cells infiltrated the HDSC disks. Only a few T cells were present in AO and PVG rats, whereas, in F344 and LEW rats, the presence of T cells was more pronounced. BN rats showed an intermediate T-cell infiltration. In mice, the FBR to HDSC was comparable between the different strains. Compared with rats, giant cell formation was limited, whereas stroma formation was more abundant. Phagocytosis of HDSC bundles rarely occurred in mice, whereas calcification was observed more often. It is concluded that the FBR to HDSC clearly differs between rats and mice. This has consequences for assessment studies on biocompatibility and also on fundamental biomaterial research.

Particulate retrieval of hydrolytically degraded poly(lactide-co-glycolide) polymers

This article describes a technique for the retrieval of polymeric particulate debris following advanced hydrolytic in vitro degradation of a biodegradable polymer and presents the results of the subsequent particle analysis. Granular 80/20 poly(L-lactide-co-glycolide) (PLG) was degraded in distilled, deionized water in Pyrextrade mark test tubes at 80 degrees C for 6 weeks. Subsequently, a density gradient was created by layering isopropanol over the water, followed by a 48-h incubation. Two opaque layers formed in the PLG tubes, which were removed and filtered through 0.2-micrometer polycarbonate membrane filters. In addition, Fourier transform IR spectroscopy (FTIR) was performed to confirm the presence of polymer in the removed layers. The filters were gold sputter coated, and scanning electron microscopy (SEM) images were made. FTIR analysis confirmed that the removed material was PLG. SEM images of the extracts from the upper (lowest density) opaque layer showed a fine, powderlike substance and globular structures of 500-750 nm. The SEM images of the lower (highest density) opaque layer showed particles with a crystalline-like morphology ranging in size from 4 to 30 micrometer. Particulate PLG debris generated with the described technique can be useful for further studies of its biological role in complications associated with poly(alpha-hydroxy)ester implants. This study shows the presence of very persistent nano- and microparticles in the degradation pathway of PLG.