Biodegradable fracture-fixation devices in maxillofacial surgery

Efficacy of bioresorbable plating system in the treatment of pediatric maxillary fractures: A short clinical study

Aim

The aim of this study was to evaluate the efficacy, stability, and clinical outcomes of a bioresorbable plating system in the treatment of pediatric maxillary fractures.

Materials and Methods

Twenty pediatric patients with maxillary fractures (13 males and 7 females) were included in this study. The 1.5- and 2.0-mm resorbable plates were used and secured with monocortical resorbable screws 6 mm and 7 mm in length. All patients were followed up for 6 months. Clinical parameters, such as pain, swelling, soft-tissue infection, malocclusion, nerve injury, and bite force for stability, were prospectively assessed.

Results

Fall from height (50%) was the most common cause of etiology, followed by road traffic accidents (35%). Maxillary alveolar # (40) was the most common fracture site, followed by nasal complex # (25%) and zygomatic complex # (25%). Appropriate fixation and adequate primary bone healing was achieved in 100% of the cases. Few minor complications were observed: (1) soft-tissue infection (5%) and (2) paresthesia (10%). There was a significant increase in bite force in the incisor and molar regions. Observation in clinical parameters shows that there was a significant reduction in postoperative pain and swelling at different follow-up periods.

Conclusion

Bioresorbable plating system is used as a load-sharing plate in a semirigid fixation technique after anatomic fracture reduction. Although its high costs limit its feasibility for use low infection rates, minimized second surgery for implant removal attracts its use. 1.5- and 2-mm resorbable plating system along is a good treatment modality for moderately displaced maxillary fractures in pediatric patients. Larger sample size and longer follow-up studies are required for conclusive results.

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

Aim:

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

Materials and Methods:

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

Results:

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

Conclusion:

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

Bone Regeneration Capacity of Newly Developed Uncalcined/Unsintered Hydroxyapatite and Poly-l-lactide-co-glycolide Sheet in Maxillofacial Surgery: An In Vivo Study

Uncalcined/unsintered hydroxyapatite and poly-l-lactide-co-glycolide (u-HA/PLLA/PGA) is a new bioresorbable nanomaterial with superior characteristics compared with current bioresorbable materials, including appropriate mechanical properties, outstanding bioactive/osteoconductive features, and remarkably shorter resorption time. Nevertheless, the bone regeneration characteristics of this nanomaterial have not been evaluated in maxillofacial reconstructive surgery. In this study, we used a rat mandible model to assess the bone regeneration ability of u-HA/PLLA/PGA material, compared with uncalcined/unsintered hydroxyapatite and poly-l-lactide acid (u-HA/PLLA) material, which has demonstrated excellent bone regenerative ability. A 4-mm-diameter defect was created at the mandibular angle area in 28 Sprague Dawley male rats. The rats were divided into three groups: u-HA/PLLA/PGA (u-HA/PLLA/PGA graft + defect), u-HA/PLLA (u-HA/PLLA graft + defect), and sham control (defect alone). At 1, 3, 8, and 16 weeks after surgeries, the rats were sacrificed and assessed by micro-computed tomography, histological analysis with hematoxylin and eosin staining, and immunohistochemical analyses. The results confirmed that the accelerated bone bioactive/regenerative osteoconduction of u-HA/PLLA/PGA was comparable with that of u-HA/PLLA in the rat mandible model. Furthermore, this new regenerative nanomaterial was able to more rapidly induce bone formation in the early stage and had great potential for further clinical applications in maxillofacial reconstructive surgery.

Efficacy of Altered Two-Point Fixation in Zygomaticomaxillary Complex Fracture

PURPOSE

To reconstruct a zygomaticomaxillary complex (ZMC) fracture, zygomaticofrontal (ZF) suture is the most reliable site to assess anatomical alignment and to secure rigidity. It has been chosen primary site to be fixed, but approach through the lateral eyebrow incision may leave a visible scar. This study suggests altered two-point fixation of ZMC fracture without accessing the ZF suture.

METHODS

In the retrospective study, a total of 40 patients with ZMC fracture were divided into two groups (group 1, two-point fixation and group 2, three-point fixation). Patient demographics and follow-up were evaluated, and degree of reduction including cortical gaps of ZF and inferior orbital (IO) area, protruding difference of zygoma, and malar difference using asymmetry index were measured through preoperative and postoperative CT.

RESULTS

Preoperatively, the means of ZF displacement, IO displacement, protruding difference of zygoma, and facial asymmetry index between the groups were not statistically different. The result was the same after the operation. However, all variables were significantly different before and after surgery within each group. Moreover, mean operation time was significantly different between groups (P value = 0.026).

CONCLUSION

Altered two-point fixation in ZMC fracture excluding incision approaching the ZF provides surgical efficacy and similar surgical outcomes to three-point fixation but offers reduced operation time and fewer complications.

Complications of a poly-L-lactic acid and polyglycolic acid osteosynthesis device for internal fixation in maxillofacial surgery

The purpose of this study was to retrospectively evaluate and examine the incidence of complications using poly-L-lactic acid and polyglycolic acid (PLLA/PGA) copolymer plate system in maxillofacial osteosynthesis. The retrospective study included 87 patients (50 men, 37 women), who needed maxillofacial surgery. We examined the proportion of complications and their factors from clinical data. A comparison was also made for plate decomposition using the molecular weight of the plate without plate exposure and complications. Osteosynthesis sites healed in all patients. Ten cases (11.5%) showed plate exposure-related complications, with all occurring at intraoral surgical sites. There was no significant difference in molecular weight changes of plates in resorbable process. Statistical analysis of study variables between patients with and without exposed plates showed that the plate thickness was significantly associated with the risk of exposed plates (p < 0.05). The commercially available PLLA/PGA device could be a useful rapid resorbable material for maxillofacial osteosynthesis. When thick plates are used on the intraoral site, it may be necessary to pay attention to the complication of plate exposure. Even if exposure-related complications have occurred, resorption and degradation of this material proceeds, suggesting the ease of appropriate risk management.

Polylactic acid (PLA) controlled delivery carriers for biomedical applications

Polylactic acid (PLA) and its copolymers have a long history of safety in humans and an extensive range of applications. PLA is biocompatible, biodegradable by hydrolysis and enzymatic activity, has a large range of mechanical and physical properties that can be engineered appropriately to suit multiple applications, and has low immunogenicity. Formulations containing PLA have also been Food and Drug Administration (FDA)-approved for multiple applications making PLA suitable for expedited clinical translatability. These biomaterials can be fashioned into sutures, scaffolds, cell carriers, drug delivery systems, and a myriad of fabrications. PLA has been the focus of a multitude of preclinical and clinical testing. Three-dimensional printing has expanded the possibilities of biomedical engineering and has enabled the fabrication of a myriad of platforms for an extensive variety of applications. PLA has been widely used as temporary extracellular matrices in tissue engineering. At the other end of the spectrum, PLA's application as drug-loaded nanoparticle drug carriers, such as liposomes, polymeric nanoparticles, dendrimers, and micelles, can encapsulate otherwise toxic hydrophobic anti-tumor drugs and evade systemic toxicities. The clinical translation of these technologies from preclinical experimental settings is an ever-evolving field with incremental advancements. In this review, some of the biomedical applications of PLA and its copolymers are highlighted and briefly summarized.

Efficacy of Resorbable Plates for Reduction and Stabilization of Laryngeal Fractures

We evaluated the efficacy of resorbable reconstruction plates (polylactic acid copolymer) for the open reduction and stabilization of displaced laryngeal fractures. Both MacroPore and Leibinger reconstruction plates were used with equal ease of application in 3 adult male patients. We found the plating system to be especially effective for the reduction of comminuted cricoid fractures. Adequate skeletal stabilization allowed early resumption of phonatory and respiratory function without long-term intraluminal stenting for skeletal support. No complications of hematoma, seroma, or infection were experienced. Resorbable plates appear to be relatively safe and useful for internal fixation of both cartilaginous and ossified parts of the larynx, allowing rapid rehabilitation and return of function.

Utilization of Ethyl Cyanoacrylate and 2-Octyl Cyanoacrylate Adhesives for Autogenous Bone Graft Fixation: Histomorphometric Study in Rats

The present study analyzes the repair process of autogenous bone graft in a block fixed with ethyl cyanoacrylate and 2-octyl cyanoacrylate adhesives in rat calvaria. Forty-eight rats, divided into 3 groups, received round osteotomies at the right parietal bone for the attainment of autogenous bone graft fragment, which was fixed at the opposite side to the donor site with ethyl cyanoacrylate (ethyl group) and 2-octyl cyanoacrylate (octyl group) adhesives. In the control group, bone fragment was only juxtaposed at the parietal bone surface without any fixation material. The animals were euthanized after 10 and 60 postoperative days. The calvariae were processed in a laboratory for the attainment of slides stained through the hematoxylin and eosin technique for histological and histometric analysis. The qualitative analysis showed a discrete inflammatory infiltrate in the control group and moderate inflammatory infiltrate in the ethyl and octyl groups at the 10-day period, which remained at the 60-day period, mainly in the octyl group. The bone fragment remained bonded to the recipient site through the adhesive, but graft incorporation was not observed in any of the specimens. Resorption was higher in the octyl group followed by the ethyl and control groups, both at the 10- and 60-day periods, but with no statistical significance (P &lt; .05). Although promoting graft fixation and its maintenance at the recipient site, both studied adhesives did not allow the graft incorporation, producing a localized and discrete inflammatory reaction, which persisted at 60 days, being more intense in the octyl cyanoacrylate group.

Bio-resorbable plates as effective implant in paediatric mandibular fracture

AIM

To evaluate the efficacy of bio-resorbable plates in paediatric mandibular fracture.

MATERIALS AND METHODS

In the present study, 40 cases of mandibular fractures were treated by Inion Cps plating system using, 2 and 2.5 mm (LPLA/DLPLA/TMC/PGA) bio-resorbable bone plates and screws of 6 and 8 mm screws. The assessment of the patients was done at 2 week, 1, 3, and 6 months using the clinical parameters and bite force recording.

RESULTS

There was significant reduction in pain at different follow-ups. Paraesthesia was found in two patients with body fracture which remained for 2 week and 1 month follow-up. No paraesthesia was found after 3rd follow-up. Significant stability of fracture fragments were found on different follow ups. Implant exposure was present only in two patients (5%) at 1 month follow up. There was significant increase in incisor, right molar and left molar bite force at 1, 3 and 6 months, from 2nd week onwards.

CONCLUSION

These findings show that the use of bio-resorbable plates in paediatric mandibular fracture was efficacious enough to bear the masticatory loads during osteosynthesis of the fracture. The recent and significant achievement is the advent of bio-resorbable osteosynthesis devices that has almost solved the problems of stress shielding, secondary surgery and corrosion when metal implants are left-in situ.

The clinical usefulness of ultrasound-aided fixation using an absorbable plate system in patients with zygomatico-maxillary fracture

Background

Ultrasound-aided fixation is a recently developed alternative method of treatment of zygomatico-maxillary (ZM) fracture, and it can resolve the problems of excessive torsion force and subsequent fractures of screws. We conducted this study to evaluate the clinical usefulness of ultrasound-aided fixation as compared with the conventional fixation method using a drill and an expander in patients with ZM fracture.

Methods

We conducted a retrospective study in 35 patients with ZM fracture who had been treated at our hospital during a period ranging from March of 2008 to December of 2010. We divided them into two groups: an ultrasound-aided fixation group, comprising 13 patients who underwent ultrasound-aided fixation (SonicWeld Rx, KLS Martin), and a conventional group, comprising 22 patients who underwent conventional fixation (Biosorb FX, Linvatec Biomaterials Ltd.). We compared such variables as sex, direction, age at operation, follow-up period, operation duration, number of fixed holes, and time to discharge between the two groups.

Results

The ultrasound-aided fixation reduced the operation duration by about 30 minutes as compared with that of conventional fixation. There was no significant difference in follow-up period, number of fixed holes, or time to discharge between the two groups. Furthermore, there were no complications in either group.

Conclusions

The ultrasound-aided fixation of fractured ZM bone using an absorbable implant system is safe and effective in promptly reducing the bone fracture and providing satisfactory cosmetic outcomes over time.

Histomorphometric analysis of the repair process of autogenous bone grafts fixed at rat calvaria with cyanoacrylate

Objective

The purpose of this study was to perform histological and histometric analyses of the repair process of autogenous bone grafts fixed at rat calvaria with ethyl-cyanoacrylate adhesive.

Material and Methods

Thirty-two rats were divided into two groups (n=16), Group I - Control and Group II - Adhesive. Osteotomies were made at the right parietal bone for graft obtainment using a 4-mm-diameter trephine drill. Then, the bone segments were fixed with the adhesive in the parietal region of the opposite side to the donor site. After 10 and 30 days, 8 animals of each group were euthanized and the calvarias were laboratorially processed for obtaining hematoxylin and eosin-stained slides for histological and histometric analyses.

Results

An intense inflammatory reaction was observed at the 10-day period. At 30 days, this reaction was less intense, despite the presence of adhesive at the recipient-site/graft interface. Graft incorporation to the recipient site was observed only at the control group, which maintained the highest graft size at 10 and 30 days.

Conclusions

Although the fragment was stable, the presence of adhesive in Group II did not allow graft incorporation to the recipient site, determining a localized, discrete and persistent inflammatory reaction.

Current requirements for polymeric biomaterials in otolaryngology

In recent years otolaryngology was strongly influenced by newly developed implants which are based on both, innovative biomaterials and novel implant technologies. Since the biomaterials are integrated into biological systems they have to fulfill all technical requirements and accommodate biological interactions. Technical functionality relating to implant specific mechanical properties, a sufficiently high stability in terms of physiological conditions, and good biocompatibility are the demands with regard to suitability of biomaterials. The goal in applying biomaterials for implants is to maintain biofunctionality over extended periods of time. These general demands to biomaterials are equally valid for use in otolaryngology. Different classes of materials can be utilized as biomaterials. Metals belong to the oldest biomaterials. In addition, alloys, ceramics, inorganic glasses and composites have been tested successfully. Furthermore, natural and synthetic polymers are widely used materials, which will be in the focus of the current article with regard to their properties and usage as cochlear implants, osteosynthesis implants, stents, and matrices for tissue engineering. Due to their application as permanent or temporary implants materials are differentiated into biostable and biodegradable polymers. The here identified general and up to date requirements for biomaterials and the illustrated applications in otolaryngology emphasize ongoing research efforts in this area and at the same time demonstrate the high significance of interdisciplinary cooperation between natural sciences, engineering, and medical sciences.

Development of a Novel Temporary Epicardial Pacing Wire With Biodegradable Film

PURPOSE

A temporary epicardial pacing wire (TEPW) has been routinely placed in patients undergoing cardiac surgery. However, its fixation or removal occasionally causes troublesome complications. The aim of this study is to develop a novel TEPW using biodegradable film to fix the electrode to the epicardium without needle stabbing.

DESCRIPTION

A biodegradable film was prepared with poly(L-lactide-co-epsilon-caprolactone). The film has a honeycomb-patterned structure that serves as a temporary adhesive for the myocardial surface, and the electrode was incorporated within the film. The novel TEPW was placed on the ventricular epicardium of dogs (group A, n = 5). As a control, conventional TEPW was inserted (group B, n = 6). The pacing threshold, R wave amplitude, impedance, and slew rate were measured at postoperative days 0, 1, 3, 5, 7, and 14, and complications after removal were checked.

EVALUATION

All measurements in both groups were identified and differences were not observed. In addition, the novel TEPWs could be easily removed without related complications.

CONCLUSIONS

This novel TEPW is safe and feasible for postoperative management of cardiac surgeries.

Fixation of the split calvarial graft in nasal reconstruction

Reconstruction of nasal contour where skeletal support is deficient or absent has usually been achieved using autogenous bone. Membranous bone taken from the cranium is clearly superior to rib or iliac crest when used as autografting material to the craniofacial skeleton. Conventionally, the bone graft is rigidly fixated to the recipient nasal bone with either metal plate-screw systems or Kirschner wires. Reported here are the results of a single biodegradable screw fixation of the split calvarial graft that is used for nasal reconstruction. Ten patients with moderate to severe saddle nose deformity underwent reconstruction using the open rhinoplasty approach. The graft was harvested from the outer cortex of the parietal bone, shaped, and secured in place with a single bioresorbable screw. No significant resorption has been observed in the grafts and a favorable aesthetic result was achieved in all of the cases. Described modification in fixation of the bone graft in nasal reconstruction avoids some of the disadvantages of permanent materials while preserving the advantages of rigid fixation.

Polyglycolic acid/poly-L-lactic acid copolymer use in laryngotracheal reconstruction: a rabbit model

OBJECTIVE

To evaluate the tissue response and resorption of the polyglycolic acid/poly-L-lactic acid (PGA/PLLA) implant in laryngotracheal reconstruction and compare its dynamic stability with autologous cartilage grafts.

STUDY DESIGN

An interventional, before-after trial.

METHODS

Twenty-one white, female, New Zealand rabbits were divided into four groups. Groups A and B underwent laryngotracheoplasty using the PGA/PLLA implants of 3 and 4 mm widths. Group C received autologous ear cartilage grafts. Group D was the control group and did not undergo surgery. The subjects were sedated at 12 months, and the larynges were evaluated in vivo for stability and area measurements by way of endoscopy during spontaneous respiration. The subjects were then killed, the larynges harvested, and the negative intraluminal pressures applied to the laryngotracheal unit were measured in a closed-system apparatus. The larynges were then evaluated for inflammatory reaction and implant resorption by way of histologic analysis.

RESULTS

All implanted subjects survived without complications and grew normally. There was no appreciable subglottic collapse during spontaneous respiration under anesthesia. Ex vivo examination of maximum negative intraluminal pressures (-50 cm H2O) in a closed system demonstrated subglottic collapse of 78%, 72%, 61%, and 3% for groups A, B, C, and D, respectively, revealing the inherent weakness in the surgically manipulated airways regardless of grafting material. Histologically, the PGA/PLLA implants were essentially completely resorbed.

CONCLUSIONS

PGA/PLLA appears to be a safe and effective synthetic material for use in laryngotracheal reconstruction in the rabbit model while avoiding donor site morbidity and additional operative time. Reconstructed airways maintained adequate strength and patency under physiologic conditions and are comparable with autologous cartilage grafts.

Rigid internal fixation with titanium versus bioresorbable miniplates in the repair of mandibular fractures in rabbits

The purpose of this study was to compare by qualitative histology the efficacy of rigid internal fixation with titanium system and the Lacto Sorb system in mandibular fractures in rabbits. Thirty male adult rabbits Oryctolagus cuniculus were used. Unilateral mandibular osteotomies were performed between the canine and first premolar. The animals were divided into two groups: for Group I-rigid internal fixation was performed with titanium system 1.5 mm (Synthes, Oberdorf, Switzerland), with two screws of 6 mm (bicortical) on each side of the osteotomy. For Group II-rigid internal fixation was performed with PLLA/PGA system 1.5 mm (Lacto Sorb, WLorenz, Jacksonville, FL, USA). The histological analysis evaluated the presence of inflammatory reaction, degree of bone healing and degree of resorption of the Lacto Sorb screws. The results of both fixation systems were similar, only with a small difference after 15 and 30 days. In Group I a faster bony healing was noted. But after 60 days, bony healing was similar in both groups. It is concluded that both PLLA/PGA and titanium plates and screws provide sufficient strength to permit mandibular bone healing. The resorption process of PLLA/PGA osteosynthesis material did not cause acute or chronic inflammatory reaction or foreign body reaction during the studied period.

Orbital floor reconstruction with poly-L/D-lactide implants: clinical, radiological and immunohistochemical study in sheep

In this study the reconstruction capacity of orbital wall in sheep was evaluated when poly-L/D-lactide (PLDLA96) implants were used for large blow-out defects in 18 sheep. The contralateral side, where the defects healed spontaneously, served as controls. The follow-up was 12, 16, 22 and 36 weeks. Healing was evaluated clinically, radiologically, histologically and immunohistochemically. Physiochemical properties of the implants were also studied. At first, the implants were surrounded by elastic capsules, which gradually ossified. At 36 weeks, 60% were still visible and deformed but surrounded by bone. Light microscopy revealed a low grade inflammatory reaction. Expression of Tn-c and cFn was intense throughout the study. Shear strength decreased gradually and was not measurable after 16 weeks. Crystallinity increased steadily from 1.5 to 29.30% and molecular weight decreased from 49,000 to 4186. In CT, the final bony defect was smaller in the reconstructed sides than in the controls. Based on this study it can be concluded that PLDLA96 implant provokes a local inflammation, which does not prevent bone healing. The deformation of the implant, however, indicates that this PLDLA96 plate is not suitable for orbital floor reconstruction.

Resorbable poly-l-lactide plates and screws for the treatment of mandibular condylar process fractures: a clinical and radiologic follow-up study

PURPOSE

The purpose of this study was to determine whether a resorbable poly-l-lactide (PLLA) miniplate system could be used to treat mandibular condylar process fracture.

PATIENTS AND METHODS

Fourteen patients (12 males, 2 females, aged 23.1 +/- 5.7 years) who had mandibular condylar process fractures treated with PLLA implants were recalled for follow-up clinical and radiologic examinations at 3 years.

RESULTS

Mouth opening recovered to more than 35 mm and occlusion was stable in all patients. There was no facial asymmetry 3 months postoperatively. Two patients had mild chronic postoperative tenderness at the implantation site; however, there was no wound infection. All fractured mandibular condyles showed anatomic good reduction and long-term stability with the use of resorbable miniplates and screws. Bone healing was satisfactory in all patients, and there was no evidence of abnormal resorption of the condylar process. The screw holes remained evident after 3 years. Screw holes in 2 patients showed enlargement on radiographic examination.

CONCLUSION

The PLLA miniplate system provides reliable stability when used for the fixation of mandibular condylar process fractures.

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.

The effect of an admixture of sodium hydrogen phosphate or heparin-coating to poly(D,L)lactide--results of an animal study

The study was aimed at investigating the effect of an admixture of sodium hydrogen phosphate (NaP) on the pH value around degrading poly(D,L)lactide (PDLLA) and the possible improvement of PDLLA biocompatibility by coating its surface with heparin. PDLLA +/- NaP was injection-molded to form rods (20 x 3 x 2 (mm)) and cubes (3 x 2 x 2 (mm)). Half of the pure PDLLA samples were surface-coated using heparin. One rod and cube each of PDLLA, PDLLA + NaP and PDLLA/Hep were implanted into the dorsal muscles of 42 rats. From the 2nd to 52nd week after operation, pH measurements were performed in the environment around the implants. The samples were then harvested for histological and mechanical analyses. No significant decrease in pH-values was observed in the tissue around the implants. Pure PDLLA and PDLLA/Hep samples were macroscopically resorbed after 52 weeks, while the degradation of PDLLA + NaP was still in progress. Approximately 80% of the initial bending strength of PDLLA or PDLLA/Hep rods was present after six weeks, while the bending strength of PDLLA + Nap was reduced to 50% after 4 weeks. Heparin-coating of PDLLA did not improve its biocompatibility but did increase its resorption. While no significant effect of NaP on pH value was found, its admixture did reduce the mechanical characteristics of the implants.

Preliminary assessment of skeletal stability after sagittal split mandibular advancement using a bioresorbable fixation system

We studied skeletal stability during the first year after mandibular advancement and fixation with bioresorbable self-reinforced poly-L-lactide (SR-PLLA) screws in 11 patients by cephalometric measurements. We compared these with a cohort of 11 patients, in whom titanium screws were used for fixation. We found no significant difference between the two groups in the median preoperative cephalometric values and the median changes after operation. There was also no significant difference between the two groups regarding the median extent of relapse 1-year after operation. We conclude that bioresorbable SR-PLLA screws are comparable to metallic screws for fixation of bone after sagittal split mandibular advancement.

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.

The efficacy of resorbable plates in head and neck reconstruction

OBJECTIVE/HYPOTHESIS

The advent of malleable macroporous resorbable plates has allowed the surgeon a greater range of reconstructive options and has decreased the morbidity of conventional plating procedures. Completely malleable after warming to 55 degrees C, resorbable plates can readily conform to most morphologic appearances of fractures or defects and provide rigid fixation when cooled. The plating systems used in head and neck reconstruction are described.

STUDY DESIGN

Nine patients were selected for reconstruction using a resorbable plating system. The resorbable system was tested under a variety of clinical situations including frontal sinus fractures (three patients), midface fractures (two patients), mandibular defects (two patients), and laryngeal fractures (two patients).

METHODS

Each case was evaluated for rigidity of fixation, and ease of plate contouring and application. Furthermore, the postoperative functional and cosmetic results and complications were contrasted between the resorbable plating systems and each surgeon's vast experience with traditional plating systems.

RESULTS

The resorbable plating system was found to be as effective as traditional plating systems with respect to rigidity of fixation, functional results, and complications. In addition, the resorbable system was far easier to contour and, consequently, to apply, while producing higher cosmetic satisfaction after plate resorption than traditional plating.

CONCLUSIONS

Based on our experience, resorbable plates appear to be safe, easy to contour and apply, as well as effective for a wide range of head and neck reconstructive applications. In addition, the shortcomings of permanently retained plates such as plate migration, bone growth restriction, and imaging artifact are avoided.

Outcome analysis for correction of single suture craniosynostosis using resorbable fixation

A retrospective review was performed on 63 patients at Childrens Healthcare of Atlanta at Scottish Rite who underwent correction of single-suture craniosynostosis using a resorbable fixation system. Included in the series were 24 patients with metopic synostosis, 15 with sagittal synostosis, and 24 with unicoronal synostosis. The average age at operation was 22.7 months (range: 2.8 months-18 years), and mean follow-up time was 30.7 months (range: 7.1-10 years). Reoperation equal to or exceeding the magnitude of the original procedure occurred in 4.76% of the patients. This was comparable to the reoperation rate observed at our institution using traditional fixation systems. Minor complications related to the use of resorbable plates were also identified, and the final outcome for single-suture synostosis was favorable. Results suggest that resorbable plates and screws are as effective as titanium-based systems in the treatment of single-suture synostosis.

Resorbable plate fixation in pediatric craniofacial surgery: long-term outcome

OBJECTIVE

To determine the long-term efficacy of resorbable plate fixation in pediatric patients undergoing craniofacial surgery for congenital anomalies, traumatic deformities, or skull base tumors.

DESIGN

Retrospective case review.

MATERIALS AND METHODS

Medical records of 57 consecutive cases using resorbable plates and screws for craniofacial fixation in patients younger than 18 years were analyzed.

MAIN OUTCOME MEASURES

The status of bone healing postoperatively (anatomical union, malunion, delayed union, or nonunion) and any complications or adverse effects (hardware visibility or palpability, plate extrusion, or infection) were noted.

RESULTS

In midfacial and upper face procedures (54 patients) anatomical union and uncomplicated bone healing occurred in 52 (96%) of the patients. In this same group, complications (plate extrusion) occurred in 2 patients (3.7%) and were resolved using conservative treatment without untoward sequelae. These outcomes are comparable to results using metal osteosynthesis in similar situations. Costs of resorbable hardware are similar to existing metal fixation systems.

CONCLUSIONS

Our data support the use of bioresorbable plate fixation in pediatric craniofacial surgery as a means of avoiding the potential and well-documented problems with rigid metal fixation. Indications include fractures and segmental repositioning in low-stress non-load-bearing areas of the middle and upper craniofacial skeleton. Although there is an initial learning curve in using this technology, we believe the benefits are well worth the effort and represent a major advance in pediatric craniofacial surgery.

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.

Calcium-deficient hydroxyapatite-PLGA composites: mechanical and microstructural investigation

The microstructural and mechanical properties of composites composed of calcium deficient hydroxyapatite (CDHAp) and poly(lactide-co-glycolide) (PLGA) have been investigated. The composites were formed by hydrolysis of alpha-tricalcium phosphate (alpha-TCP) to CDHAp in pressed precomposite compacts of alpha-TCP-PLGA-NaCl. The differences in hydrolysis of alpha-TCP-PLGA-NaCl for two compositions of 80:10:10 wt % and 60:20:20 wt %. were monitored by isothermal calorimetry and X-ray diffraction. The microstructural evolution and variance in final composite microstructure after hydrolysis at 37 degrees C, 45 degrees C, and 56 degrees C were examined by scanning electron microscopy. HAp-PLGA composite formed from the alpha-TCP-PLGA-NaCl (80:10:10) precomposites at 37 degrees C developed a tensile strength of 13.3 +/- 0.9 MPa, a flexural strength of 24.8 +/- 1.7 MPa, and Young's modulus of 2.8 +/- 0.3 GPa. These values were 12.00 +/- 0.2 MPa, 36.1 +/- 2.1 MPa, and 5.5 +/- 0.8 GPa for the precomposite composition 60:20:20. All these mechanical properties showed a variation with hydrolysis temperature and composition. The differences in mechanical properties were related to the final microstructures of the composites, which are governed by the morphological changes in the polymer structure at its glass transition temperature and the extent of cement-type formation of CDHAp by hydrolysis of alpha-TCP.

Soft tissue response in the rabbit larynx following implantation of LactoSorb (PLA/PGA copolymer) prosthesis for medialization laryngoplasty

This project is designed to provide initial data regarding the use of polylactic acid/polyglycolic acid (PLA/PGA) copolymer ("LactoSorb" [Walter Lorenz Corp]), an alloplastic, resorbable material, as a prosthesis in an animal model of vocal fold medialization. Fifteen New Zealand white rabbits were utilized for left medialization laryngoplasty with LactoSorb implants after undergoing left recurrent laryngeal nerve section. At 1, 3, 6, and 9 months, the rabbits were sacrificed and their larynges were evaluated both grossly and histologically for tissue response to, and resorption characteristics of the implant, tissue cellularity, maintenance of vocal fold medialization, and airway patency. Additionally, 4 rabbits were used as controls, implanted with silicone rubber medialization implants, and sacrificed at 9 months for comparison. One rabbit underwent no surgery and was likewise used as a control. Grossly, no airway obstruction was noted, and no extrusions of the implants occurred. The LactoSorb implant maintained medialization in each group of sacrificed rabbits. Histologic findings revealed a very discrete, fibrous capsule around the implant in the 1- and 3-month rabbits, and the LactoSorb was still grossly visible. At 6 months, the thin fibrous capsule partially remained; at 9 months, the capsule was no longer evident, and the implant was no longer grossly visible. Endoscopic findings at the time of sacrifice in those rabbits implanted with silicone rubber included grossly patent airways with maintenance of medialization. In the rabbits implanted with silicone rubber, the histologic findings are similar to those described elsewhere. LactoSorb, because of its intermittent resorption rate, could offer an ideal alternative to currently utilized temporary, or resorbable, materials, and as such will hopefully prove an invaluable tool in the laryngologist's treatment planning and surgical repair of the patient with a paralyzed vocal fold.

Use of a resorbable fixation system in orthognathic surgery

We present our early experience with the use of a resorbable plating system in orthognathic surgery. Thirty-one patients who have finished growing and who had dentofacial deformities that were not part of syndromes were treated by routine orthognathic repositioning procedures: maxillary (n = 8) and mandibular (n = 9) osteotomies, or bimaxillary procedures (n = 14). All skeletal fragments were fixed with resorbable plates and screws. The follow-up period ranged from 2-8 months (mean 5). All the patients recovered normally except for one who developed a localized buccal space infection. In the early postoperative period, six patients had mild mobility of the maxilla, but stability was within normal limits at six weeks postoperatively. We conclude that, though technique has an important influence on success, LactoSorb is a good fixative for maxillo-mandibular repositioning.

The future of biodegradable osteosyntheses

In the last 3 decades, much progress has been made in the development of biodegradable osteosyntheses. Despite this progress, these materials are still only used in small numbers, and the scope of their application has been limited. The limitations of biodegradable osteosyntheses mainly are related to problems with their mechanical properties and, in particular, biocompatibility. These problems need to be solved so that biodegradable osteosyntheses can perform up to their full potential and thus, eventually, make their general clinical application routine. This paper presents a historical perspective on the development of biodegradable osteosyntheses, discusses the successful developmental achievements and the still-existing problems, and gives a perspective on their future development.

Effect of simulated intraoperative heating and shaping on mechanical properties of a bioabsorbable fracture plate material

Heating bioabsorbable fracture fixation plates to above their glass transition temperature renders them temporarily malleable, thus facilitating their adaptation to the underlying bone geometry, although the consequence of heating is not well understood. Poly (L-lactide-co-glycolide) copolymer specimens were heated under various conditions, and the effects on specimen mechanics were assessed. Heating temporarily increased toughness while slight reducing flexural modulus. No lasting effects on in vitro material degradation were seen.

Biodegradable implants in sports medicine: the biological base

Biodegradable implants are increasingly used in the field of operative sports medicine. Today, a tremendous variety of implants such as interference screws, staples, sutures, tacks, suture anchors, and devices for meniscal repair are available. These implants consist of different biodegradable polymers that have substantially different raw material characteristics such as in vivo degradation, host-tissue response, and osseous replacement. Because these devices have become the standard implant for several operative procedures, it is essential to understand their biological base. The purpose of this report is to provide a comprehensive insight into biodegradable implant biology for a better understanding of the advantages and risks associated with using these implants in the field of operative sports medicine. In particular, in vivo degradation, biocompatibility, and the osseous replacement of the implants are discussed. A standardized classification system to document and treat possible adverse tissue reactions is given, with special regard to extra-articular and intra-articular soft-tissue response and to osteolytic lesions.

SR-PLLA and SR-PGA miniscrews: biodegradation and tissue reactions in the calvarium and dura mater

The biocompatibility and degradation of self-reinforced poly-L-lactide (SR-PLLA) and polyglycolide (SR-PGA) miniscrews, vs titanium miniscrews, was studied in frontal bone osteotomies in 20 lambs, where they were used for plate fixation. At follow-up at 4, 6, 12, 26, 52 and 104 weeks, no clinical foreign body reaction, infection or other complications had occurred. Histologically, PGA material was hydrolyzed and fragmented at 4-6 weeks and was resorbed by 12 weeks, whereas the SR-PLLA miniscrews retained their integrity and holding power for 26 weeks and were mostly resorbed at 2 years. According to histological and histomorphometric analyses and plain film radiography, the degradation of PGA miniscrews was accompanied by a typical non-specific foreign-body reaction and initial transient osteolysis with decreased osteoid formation around the screw channel, but compensatory intense osteoid formation and bone remodelling followed after resorption of the polymer. The foreign body reactions to PLLA and titanium were considerably milder. All miniscrews were commendably strong and could be satisfactorily tightened against the plate. SR-PLLA miniscrews offer fixation stability for half a year, whereas rapidly degrading SR-PGA miniscrews may be used when short-term fixation is needed.

Fixation of zygomatic fractures with a new biodegradable copolymer osteosynthesis system. Preliminary results

In a prospective study, a new biodegradable osteosynthesis material for the facial skeleton has been used in 27 patients with zygomatic fractures. In the six-month follow-up period, the first ten patients showed clinically and radiologically uneventful healing of bone. There were no implant-related complications. The main advantages of the new material are its malleability when heated, enabling fast adaptation to the bone surface, and the avoidance of a second operation for implant removal.

Biomechanical evaluation of titanium, biodegradable plate and screw, and cyanoacrylate glue fixation systems in craniofacial surgery

Choice of appropriate fixation after reduction of displaced bone fragments or advancement of osteotomized segments requires knowledge of the maximal force to which these segments can be subjected. The present study was performed to obtain a biomechanical comparison of a variety of resorbable fixation systems as an alternative to metal plates and screws. Sheep cadaver parietal bone segments were osteotomized and fixed with one of six methods of fixation: (A) titanium plates and screws consisting of (1) miniplates and 2.0-mm-diameter screws; (2) midface plates and 1.5-mm screws; (3) microplates and 1.0-mm screws; (B) resorbable systems consisting of combinations of butyl-2-cyanoacrylate glue and biodegradable polylactic acid/polyglycolic acid copolymer plates and 2.0-mm screws as follows: (1) direct glue fixation of segments; (2) resorbable plates fixed to bone segments with cyanoacrylate glue; (3) resorbable plates fixed with resorbable screws. Compression testing was performed upon bone segments advanced and fixed across a central gap, and distraction testing was performed on bone segments fixed in direct contact. Force to failure in both distraction and compression was significantly greater in bone segments fixed with titanium miniplates than with any other method of fixation. Segments fixed with plates and screws, either nonresorbable or resorbable, achieved stronger fixation in distraction than in compression for all plate sizes tested. Resorbable plate and screw fixation was as strong as standard titanium midface and microplating systems in distraction, and stronger than the latter techniques in compression. With compressive forces of relapse, fixation with glue and resorbable plates was as strong as standard titanium midface and microplating systems. However, with distractive forces of relapse, glue fixation of either the bone segments or resorbable plates was weaker than both titanium and resorbable alternatives in which plates and screws were used. These findings may have direct impact on the choice of fixation devices used to support osteotomized or fractured bone segments, which are subjected to persistent muscular and soft-tissue pull.

Consolidation of craniotomy lines after resorbable polylactide and titanium plating: a comparative experimental study in sheep

The consolidation process of craniotomy lines in a skeletally immature large mammal was studied. A traditional narrow titanium miniplate was compared with a 0.5-mm-thick, 12-mm-wide absorbable punched self-reinforced poly-L-lactide (SR-PLLA) plate, both fixed with titanium miniscrews over bilateral parietal 2.5-mm-wide stable transosseous craniotomies on nine female sheep (16 to 20 months old). After 6, 12, 20, 52, and 104 weeks, cross-sectional histology, histomorphometry, and oxytetracycline chloride fluorescence studies were done to compare the healing process of the craniotomy lines and to study the biocompatibility and the degradation process of the SR-PLLA plate. The consolidation pattern supported the principle of guided tissue regeneration: under the wide, resorbable plate osseous bridging proceeded evenly throughout the line, whereas titanium plating led to bulky, uneven growth in the bone margins. All SR-PLLA-plated osteotomy lines had healed completely by 20 weeks, whereas none of the titanium-plated lines had consolidated during a follow-up of 1 year. The nonossified gaps were filled with dense connective tissue. Histomorphometric analysis showed that osseous bridging proceeded significantly faster on the resorbable plate side compared with the titanium side (p < 0.001). The osteoid surface fraction over the total trabecular surface was highest at 6 weeks, being 63 percent on the SR-PLLA side and only 36 percent on the titanium side. The oxytetracycline chloride fluorescence studies confirmed these findings. After 52 weeks, there was no osteoid or oxytetracycline chloride fluorescence left as a sign of terminated ossification, even in the nonconsolidated titanium sides. Microscopic cracking of the plate was evident at 12 to 20 weeks, and the first signs of active resorption were present at 52 weeks. After 2 years, the plate had disappeared and tiny polylactide particles were being actively reabsorbed. The biocompatibility of SR-PLLA and titanium was good, and no adverse cellular reactions to these materials were noted, except a clinical foreign body reaction caused by loosened titanium miniscrews. A densely punched, 0.5-mm-thick self-reinforced PLLA plate seems to retain its integrity for a sufficiently long time to complete osseous healing of a 2.5-mm-wide craniotomy line in the sheep calvarial area. A thin, wide fixation plate enables superior healing, especially in osseous defects. The degradation process of the SR-PLLA plate begins within 1 year and is far advanced after 2 years. By using absorbable SR-PLLA fixation plates instead of metallic plates, a subsequent operation for the removal of the implants can be avoided. SR-PLLA devices could thus be a potential additive or even alternative to metallic implants in craniofacial surgery.

The use of biodegradable fixation in sagittal split and vertical subsigmoid osteotomy of the mandible: a preliminary report

OBJECTIVE

An absorbable pin made from poly-p-dioxanone (Orthosorb, Johnson and Johnson, UK) was used to internally fix osteotomies of the mandibular ramus. We present our initial series of 10 patients.

DESIGN

Open study.

SETTING

Regional unit, teaching hospital, UK.

SUBJECTS AND INTERVENTIONS

10 patients who required a bilateral sagittal split osteotomy (BSS, n = 3) or a vertical subsigmoid osteotomy (BVSS, n = 6), or both (n = 1).

MAIN OUTCOME MEASURE

Jaw functioning and ability to open mouth.

RESULTS

9/10 followed up for 1 year, 1/10 lost to follow up at one month, 1/10 lost to follow up at one year. 7/9 reported the same degree of mouth opening as preoperatively, 2/9 slightly less. 3/10 developed slight anterior open bite problems; 1/10 required no treatment, 1/10 improved with selective grinding, and 1/10 was lost to follow up. No patient complained of discharge from the site of the implant or of any change in sensation of the lip.

CONCLUSION

Small absorbable implants undoubtedly have a place in selected maxillofacial operations, but there are still some problems with their use, including complications during the learning curve.

Effects of implantable biomaterials on radiation dosimetry

BACKGROUND

It is generally known that radiation dose is enhanced in front of and reduced behind metallic plates. This study evaluates metallic, ceramic, and bioabsorbable facial-reconstruction materials for their differential effects on radiation dosimetry.

METHODS

Commercially pure titanium (cpt), stainless steel (steel), titanium alloy (tia), hydroxyapatite (HA), and poly-L-lactide (PLA, a bioabsorbable polymer) were obtained for this study. The radiation doses distal (behind) and proximal (in front of) to the test material were measured with an ionization chamber placed at several distances from the test material. Therefore, transmission (proximal to plate) and backscattering (distal to plate) factors were generated at several distances for each material.

RESULTS

Poly-L-lactide transmitted nearly 100% of the incident radiation beam. The metals had the greatest effect on transmission with steel, followed by cpt, tia, and HA showing the greatest reduction of incident beam. Poly-L-lactide revealed minimal backscattering. Greater backscatter of the incident radiation beam was seen from steel, followed by cpt and HA. Poly-L-lactide also behaved similar to water in transmission and backscatters properties during electron irradiation.

CONCLUSIONS

Poly-L-lactide has a minimal effect on the radiation-dose distribution and may be beneficial as a reconstructive device for patients undergoing head and neck cancer radiotherapy. Hydroxyapatite showed a relatively minor effect, whereas the metals (steel, followed by cpt and tia) revealed the greatest detrimental effect on the radiation-dose distribution.