Maximizing results in craniofacial surgery with bioresorbable fixation devices

Osseointegration enhancement by controlling dispersion state of carbonate apatite in polylactic acid implant

Osteoconductive ceramics (OCs) are often used to endow polylactic acid (PLA) with osseointegration ability. Conventionally, OC powder is dispersed in PLA. However, considering cell attachment to the implant, OCs may be more favorable when they exist in the form of aggregations, such as granules, and are larger than the cells rather than being dispersed like a powder. In this study, to clarify the effects of the dispersion state of OCs on the osseointegration ability, carbonate apatite (CAp), a bone mineral analog that is osteoconductive and bioresorbable, powder-PLA (P-PLA), and CAp granule-PLA (G-PLA) composite implants were fabricated via thermal pressing. The powder and granule sizes of CAp were approximately 1 and 300-600 µm, respectively. G-PLA exhibited a higher water wettability and released calcium and phosphate ions faster than P-PLA. When cylindrical G-PLA, P-PLA, and PLA were implanted in rabbit tibial bone defects, G-PLA promoted bone maturation compared to P-PLA and pure PLA. Furthermore, G-PLA bonded directly to the host bone, whereas P-PLA bonded across the osteoid layers. Consequently, the bone-to-implant contact of G-PLA was 1.8- and 5.6-fold higher than those of P-PLA and PLA, respectively. Furthermore, the adhesive shear strength of G-PLA was 1.9- and 3.0-fold higher than those of P-PLA and PLA, respectively. Thus, G-PLA achieved earlier and stronger osseointegration than P-PLA or PLA. The findings of this study highlight the significance of the state of dispersion of OCs in implants as a novel strategy for material development.

Implementation of Upper Extremity Trauma Registry: A Pilot Study

Background

Hand traumas are common in young men and their complications can have negative effects on their occupation and economic activities. On the other hand, most of the hand injuries are related to occupation accidents and thus necessitates preventive measures. The goal of a clinical registry is assisting epidemiologic surveys, quality improvement preventions.

Methods

This article explains the first phase of implementing a registry for upper extremity trauma. This phase includes recording of demographic data of patients. A questionnaire was designed. Contents include patients' characteristics, pattern of injury and past medical history in a minimal data set checklist. This questionnaire was filled in the emergency room by general practitioners. For 2 months the data were collected in paper based manner, then problems and obstacles were evaluated and corrected. During this period a web based software was designed. The registry was then ran for another 4 months using web based software.

Results

From 6.11.2019 to 5.3.2020, 1675 patients were recorded in the registry. Random check of recorded data suggests that accuracy of records was about 95.5%. Most of the missing data was related to associated injuries and job experience. Some mechanisms of injury seems to be related to Iran community and thus warrants special attention for preventive activities.

Conclusion

With a special registry personnel and supervision of plastic surgery faculties, an accurate record of data of upper extremity trauma is possible. The patterns of injury were remarkable and can be used for investigations and policy making for prevention.

Bioabsorbable System-Related Subcutaneous Swelling After Craniofacial Surgery

BACKGROUND

Bioabsorbable systems have been commonly used in pediatric patients for primary cranioplasty and other related surgeries. However, subcutaneous swelling, a unique complication related to bioabsorbable osteosynthesis, is a concern. Differences in the incidence of subcutaneous swelling, depending on the bioabsorbable material used to construct the plate, are still unknown.

METHODS

The authors retrospectively reviewed all incidences of subcutaneous swelling related to resorbable systems used during primary cranioplasty for patients with craniosynostosis at their hospital between 2014 and 2018 during a 12-month follow-up period. Furthermore, the authors reviewed all published English-language articles (since 1995) on subcutaneous swelling in bioabsorbable systems used for craniosynostosis.

RESULTS

The most common resorbable systems used in the literature were divided into 2 groups: mixtures of poly D-lactic acid and polyglycolic acid, and mixtures of poly D- and L-lactic acid. In patients for whom poly D-lactic acid and polyglycolic acid were used, the incidence of subcutaneous swelling during resorption was 0% to 4.2% between 3 and 9 months of follow-up. In patients for whom poly D- and L-lactic acid was used, subcutaneous swelling during resorption occurred in 5% to 16.7% of these patients between 6 and 12 months of follow-up. All cases resolved spontaneously after complete absorption of the plate.

CONCLUSIONS

It was difficult to determine which system had the lowest incidence of subcutaneous swelling. The thickness of each resorbable system and the thickness of the infants' scalps were different in each study. However, subcutaneous swelling occurred in every resorbable system. Therefore, preoperative counseling and careful follow-up are necessary.

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.

Fronto-orbital advancement and reconstruction using reverse frontal bone graft without the use of orbital bar: a technical note

INTRODUCTION

We describe our technique of using reverse frontal bone graft for FOAR for patients with metopic or coronal synostosis and present our complications using the Leeds classification system for complications in craniosynostosis surgery.

METHODS

Since April 2015, seventeen patients have been operated using this technique. We perform a frontal bone graft that is then reversed, and supraorbital margins are drilled out. The orbital bar is then removed and drilled down to make bone dust and on-lay bone grafts which are then used to fill gaps on exposed dura and fill in around the temporal region.

RESULTS

All 17 patients who underwent this technique have good cosmetic results. We report 5 (29%) complications and 8 (47%) blood transfusions (7 exposures, 1 cell salvage).

Complications of craniofacial surgery using the ultrasonic-assisted pinned resorbable system: A prospective report with a minimum follow-up of 30 months

Several resorbable fixation systems are used for osteosynthesis in craniofacial surgery. Recently, ultrasonic-assisted pinned resorbable systems have been introduced; however, few studies have described the associated complications during the long-term follow-up until complete resorption. In this study, we investigated the complications of craniofacial surgery using the ultrasonic-assisted pinned resorbable system with a follow-up of at least 30 months. Among patients who underwent craniofacial surgery using a commercially available ultrasonic-assisted pinned resorbable system between 2014 and 2016, those with follow-up visits for at least 30 months were included in this study. We investigated the development of complications such as local infection, exposure of the device, and reoperation related to the implant. Twenty-four patients aged 6 months to 69.4 years (median: 3.5 years) were followed up for more than 30 months. None of the patients required reoperation regardless of implants. Further, no infection or device exposure was seen among all patients. However, two patients aged 6 and 22 months who underwent cranioplasty for craniosynostosis and another patient aged 148 months who underwent cranioplasty for cranial defect exhibited plate-related bulging in the scalp during the course of resorption between 7 and 12 months of follow-up. The bulges were characterized by swelling without pain or redness and resolved spontaneously within 18 months of follow-up, which was considered to occur after complete absorption of the plate. In conclusion, subcutaneous swelling is related to resorbable plates and has a benign clinical course. We recommend that patients be informed of this phenomenon preoperatively to relieve their anxiety.

Trimming of Absorbable Plates and Screws through Smoothing by Multiple Sonic Activation Procedures Can Increase Local Tissue Reactions in Children with Cranial Fixations

OBJECTIVE

The aim of this paper was to investigate the local reactions due to the melting of absorbable plates and screws after trimming through smoothing by multiple sonic activation procedures (MSAP).

BACKGROUND

Drilling or smoothing by MSAP is performed for the trimming of the absorbable plates and screws for cranial fixation in children. Compared to drilling, smoothing by MSAP is suspected to more commonly cause local tissue reactions; thus, the issue was examined herein.

METHODS

For 90 children with smoothing by MSAP and 83 children with drilling procedures who underwent cranial fixation using absorbable plates and screws, the type, time of onset, and incidence of the local reactions were investigated.

RESULTS

Swelling was the most common reaction, followed by inflammatory reactions with itching, heating, skin-penetrating drainage, and pus formation. The mean time of onset of the local reaction was 10.0 ± 2.3 months after surgery. Local reactions occurred in 30% of the children in the group with smoothing by MSAP, and in 7.2% of the children in the group with drilling, showing a statistically significant difference between the two groups (p < 0.001).

CONCLUSION

It was concluded that drilling rather than smoothing by MSAP to change the shapes of the absorbable plates and screws in cranial fixation can reduce the local reactions.

Evaluation of Fronto-Orbital Advancement Using Titanium-Based Internal Fixation for Corrective Pediatric Craniofacial Surgery

BACKGROUND

For successful reshaping of the cranial vault in terms of corrective fronto-orbital advancement (FOA) efficient and reliable internal fixation systems for stabilization of bone fragments are indispensable. The rate of complications and feasibility of corrective FOA with the usage of titanium-based rigid fixation systems is rarely analyzed and discussed.

METHODS

The authors retrospectively reviewed the medical records of 42 patients who received corrective FOA with the implementation of titanium internal rigid fixation and consecutive secondary surgery for removal. The reliability of the fixation system was judged by the outcome of the FOA as evaluated by the Whitaker score, esthetic outcome as well as by the complication rate of the secondary intervention, necessary for removal of the fixation system.

RESULTS

All patients were categorized as Whitaker I (no further treatment desirable). Esthetic outcome was excellent in all patients as judged by surgeon and parents. Mean age at the time of FOA was 9.3 months. Time to removal, duration of the second hospital stay for removal of the fixation system, and duration of surgical drains were on average 5 months, 2 days, and 1.7 days, respectively. Mean duration of the secondary surgery was 63 min. No complications occurred.

CONCLUSION

Our investigation supports the usage of titanium internal rigid fixation systems in pediatric craniofacial surgery, thereby providing a reliable alternative to avoid the well-documented problems of bio-absorbable plate fixation systems.

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

INTRODUCTION

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

MATERIAL AND METHODS

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

RESULTS

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

An antibacterial and absorbable silk-based fixation material with impressive mechanical properties and biocompatibility

Implant-associated infections and non-absorbing materials are two important reasons for a second surgical procedure to remove internal fixation devices after an orthopedic internal fixation surgery. The objective of this study was to produce an antibacterial and absorbable fixation screw by adding gentamicin to silk-based materials. The antibacterial activity was assessed against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro by plate cultivation and scanning electron microscopy (SEM). We also investigated the properties, such as the mechanical features, swelling properties, biocompatibility and degradation, of gentamicin-loaded silk-based screws (GSS) in vitro. The GSS showed significant bactericidal effects against S. aureus and E. coli. The antibacterial activity remained high even after 4 weeks of immersion in protease solution. In addition, the GSS maintained the remarkable mechanical properties and excellent biocompatibility of pure silk-based screws (PSS). Interestingly, after gentamicin incorporation, the degradation rate and water-absorbing capacity increased and decreased, respectively. These GSS provide both impressive material properties and antibacterial activity and have great potential for use in orthopedic implants to reduce the incidence of second surgeries.

Quantifying Craniometric Change Early After Fronto-Orbital Advancement in Metopic Synostosis

Frontal orbital advancement (FOA) for metopic synostosis results in cranial vault expansion, supporting underlying growth of the developing brain and improving head shape. Previous studies have shown that FOA in younger infants leads to a greater incidence of long-term growth restriction of intracranial volume; however, it is still unknown as to whether this is due to undercorrection at the time of surgery versus primary suture pathology. The purpose of our study is to provide a method for objective analyses of intracranial volumes in the early post-FOA period. A retrospective chart review was conducted on patients who underwent FOA over a 10-year period by a single surgeon. Data collected included patient characteristics and clinical outcomes. Radiological analysis of intracranial volumes pre- and post-FOA was determined using Amira volume-rendering software. Average increase in intracranial volume at 6 weeks post-FOA was 139.27 mL (80.01-225.25 mL) with average relative cranial vault expansion of 18.1% (3.3-48%). Patients who underwent FOA older than 12 months of age had an average increase in intracranial volume of 8.5% (3.3-13.1%). Patients younger than 12 months had a statistically higher average increase of 25% (12.8-48%). Frontal orbital advancement effectively increases intracranial volume in patients with metopic synostosis. When compared with older patients, patients younger than 1 year of age have a greater relative increase in intracranial volume in the immediate postoperative period. Quantifying cranial vault expansion after FOA can assist surgeons in surgical planning as well as in measuring and monitoring clinical outcomes within and across craniofacial centers regardless of technique.

The cranial orbital buttress technique for nonsyndromic unicoronal and metopic craniosynostosis

OBJECT

Current craniosynostosis procedures can result in complications due to absorbable plates and screws or other specialized expensive hardware. The authors propose the cranial orbital buttress (COB) technique of frontoorbital remodeling for metopic and unicoronal synostoses, wherein no plates or screws are used. They hypothesize that, with this technique, aesthetically acceptable outcomes for unicoronal and metopic synostosis can be achieved. In this article, they present this technique and compare the results with current frontoorbital remodeling practices.

METHODS

The authors conducted a retrospective chart review of cases in which patients with nonsyndromic unicoronal or metopic synostosis underwent cranio-orbital surgery at their institution from 1985 through 2009. Operative parameters, surgical variations, and complications were analyzed. The COB technique uses a 1-piece switch, hemiforeheads, or multiple pieces for forehead remodeling. The supraorbital bar is reconstructed in patients with metopic synostosis using a double wedge or greenstick fracture technique, and in patients with unicoronal synostosis a hinge procedure based on a 1.5-orbital osteotomy is used. The supraorbital bar is advanced and supported in place by bone graft(s) inserted at the lateral aspect(s) of the orbit(s) to form a buttress, with fixation done using absorbable sutures.

RESULTS

A total of 79 cases met the criteria for inclusion in the study. Twenty-nine patients had metopic synostosis, 3 had combined metopic and sagittal synostoses, and 47 had unicoronal synostosis. The patients’ mean age at surgery was 11.4 ± 10.1 months and the mean operative time was 183.4 ± 41.0 minutes. The mean length of hospital stay was 3.7 ± 1.2 days. The mean blood loss was 150.0 ± 125.6 ml, and 33% of patients required a blood transfusion (mean volume 206.9 ± 102.3 ml). In metopic synostosis, hemiforeheads were used most often (24/29, 83%), and the supraorbital bar was remodeled using a bilateral intracranial orbital osteotomy followed by a double wedge modification (23/29, 79%) or a greenstick fracture (4/29 14%) for milder cases. Forehead remodeling for unicoronal synostosis was by a forehead switch (39/47, 83%) and the supraorbital bar was remodeled using a 1.5-orbital intracranial orbital osteotomy (34/47, 72%) such that the bar was advanced on the abnormal side and hinged at the midline of the normal orbit. Perioperative complications occurred in 19% of cases and included dural tears (16%), inconsequential subdural hematoma (1.3%), and nasal greenstick fracture (1.3%). The total reoperation rate was 7.6% (cranioplasties for irregular contours, 6.3%; scar revision, 1.3%).

CONCLUSIONS

The COB remodeling technique is simple and efficient, gives acceptable outcomes, and is less resource intensive than previous techniques reported in the literature.

Comparison of titanium and biodegradable plates for treating midfacial fractures

PURPOSE

The purpose of the present study was to evaluate the use of titanium plates and screws (TPSs) versus biodegradable plates and screws (BPSs) for fixation of midfacial fractures. In addition, complications related to the plates and rates of secondary surgery for plate removal were compared.

PATIENTS AND METHODS

From March 2005 to March 2012, 109 patients were enrolled in this study. Fifty-six patients with TPSs implanted to fix midfacial fractures (group A) and 53 patients with BPSs to treat midfacial fractures (group B) were evaluated. Patients' histories of plate-related nonunion, infection, displacement, pain, and palpability and secondary surgery for plate removal were checked.

RESULTS

None of the study participants developed nonunion issues related to the TPSs or BPSs. Six patients in group A developed complications associated with TPSs and 5 patients underwent secondary surgery for plate removal. One patient (1.8%) had a plate-related infection, 1 patient (1.8%) developed plate extrusion, 1 patient (1.8%) had plate-associated chronic pain, 2 patients (3.6%) complained of palpability, and 2 patients (3.6%) developed psychological problems (1 patient developed 2 complications). In contrast, only 1 patient in group B (2%) complained of temporary palpability, and this problem disappeared over time. None of the patients in group B complained of any other problems.

CONCLUSIONS

The results indicated that BPSs and TPSs have the potential for successfully treating midfacial fractures. BPSs are suitable for treating midfacial fractures and could serve as an alternative for TPSs in selected cases.

The value of ultrasound-assisted pinned resorbable osteosynthesis for cranial vault remodelling in craniosynostosis

Resorbable osteosynthesis is a widespread tool in craniofacial surgery, however only a limited number of studies have focused on ultrasound-assisted pinned resorbable systems in the treatment of craniosynostosis. Thirty-eight children with various types of craniosynostosis including scaphocephaly, trigonocephaly, anterior and posterior plagiocephaly were treated using the Sonic Welding resorbable osteosynthesis system. All patients were evaluated for operation time, stability of the surgical results, rate of local infections and visibility or palpability of the osteosynthesis material in the follow-up ranging from 15 to 21 month. Mean operation time was not significantly higher compared to conventional osteosynthesis material and all remodelled cranial vaults showed immediate stability. Only one patient showed signs of an inflammatory skin reaction, which recovered spontaneously. The number of palpable or visible plates, respectively, increased during the first months with a maximum at 12 months (34 (89%) plates palpable, 26 (68%) plates visible). After this time point, the number decreased continuously until the end of the follow-up period at 21 months when 3 (20%) plates were palpable, 0 (0%) plates were visible). Ultrasound-assisted pinned resorbable systems seem to be a promising tool in craniofacial surgery providing a timesaving and stable osteosynthesis. An initial swelling of the plates during the first 12 months before the complete degradation might result in a palpable and visible bulge.

Complications of rigid internal fixation

Over the past 20 years, there have been many advances in the development of bone fixation systems used in the practice of craniomaxillofacial surgery. As surgical practices have evolved, the complications of each technologic advance have changed accordingly. Interfragmentary instability of interosseous wiring has been replaced by the risk of exposure, infection, and palpability of plate and screw fixation systems. The improved rigidity of plate fixation requires anatomic alignment of fracture fragments. Failure to obtain proper alignment has led to the phenomenon known as "open internal fixation" of fracture fragments without proper reduction. The size of the plates has decreased to minimize palpability and exposure. However limitations in their application have been encountered due to the physiologic forces of the muscles of mastication and bone healing. In the pediatric population, the long-standing presence of plates in the cranial vault resulted in reports of transcranial migration and growth restriction. These findings led to the development of resorbable plating systems, which are associated with self-limited plate palpability and soft tissue inflammatory reactions. Any rigid system including these produces growth restriction in varying amounts. In this discussion, we review the reported complication rates of miniplating and microplating systems as well as absorptive plating systems in elective and traumatic craniofacial surgery.

Delayed infection after a zygoma fracture fixation with absorbable plates

A 48-year-old man who had received a bioresorbable plate fixation for a zygomatic bone fracture 13 months earlier visited our clinic complaining of sudden facial swelling. The facial computed tomographic scan showed the soft tissue swelling without any bony abnormality, and the symptoms did not improve after 1 week of antibacterial therapy. The patient had a diagnosis of a late infection caused by unresorbed plates, and exploratory surgery was performed. Partially resorbed plates and screws were seen, and we removed the remnants of such completely. The symptoms were relieved after the operation, and there was no recurrence during 8 months of follow-up.

Custom-made composite scaffolds for segmental defect repair in long bones

Current approaches for segmental bone defect reconstruction are restricted to autografts and allografts which possess osteoconductive, osteoinductive and osteogenic properties, but face significant disadvantages. The objective of this study was to compare the regenerative potential of scaffolds with different material composition but similar mechanical properties to autologous bone graft from the iliac crest in an ovine segmental defect model. After 12 weeks, in vivo specimens were analysed by X-ray imaging, torsion testing, micro-computed tomography and histology to assess amount, strength and structure of the newly formed bone. The highest amounts of bone neoformation with highest torsional moment values were observed in the autograft group and the lowest in the medical grade polycaprolactone and tricalcium phosphate composite group. The study results suggest that scaffolds based on aliphatic polyesters and ceramics, which are considered biologically inactive materials, induce only limited new bone formation but could be an equivalent alternative to autologous bone when combined with a biologically active stimulus such as bone morphogenetic proteins.

Characterization methods of bone-implant-interfaces of bioresorbable and titanium implants by fracture mechanical means

Bioresorbable materials for implants have become increasingly researched over the last years. The bone-implant-interfaces of three different implant materials, namely a new bioresorbable magnesium alloy, a new self-reinforced polymer implant and a conventional titanium alloy, were tested using various methods: push-out tests, SEM and EDX analyses as well as surface analyses based on stereoscopic 3D pictures were conducted. The fracture energy is proposed as a very significant reference value for characterizing the mechanical performance of a bone-implant system. By using a video-extensometer system instead of, as is commonly done, tracking the movement of the crosshead in the push-out tests, the accuracy of measurement could be increased.

Comparison of titanium and biodegradable miniplates for fixation of mandibular fractures

PURPOSE

The purpose of the present study was to compare the use of biodegradable miniplates and titanium miniplates for the fixation of mandibular fractures.

PATIENTS AND METHODS

BioSorb FX biodegradable plates and screws and titanium miniplates were used in 91 patients (65 males and 26 females; age range 11 to 69 years) for the treatment of mandibular fractures. The clinical and radiographic findings were recorded at 1, 3, 6, and 12 months after surgery.

RESULTS

The overall complication rate was 4.41%. In the biodegradable plate group, infection occurred in 2 cases (4.26%) and was resolved by incision and drainage and antibiotics. In the titanium plate group, infection occurred in 1 case and plate fracture in 1 case (4.56%). The fractured plate was removed, and a new titanium miniplate was applied using a trocar. The infection was resolved with antibiotics. No adverse tissue reactions, malocclusions, or malunions occurred during the observation period.

CONCLUSIONS

Our results have shown that the rate of morbidity is very low with the use of biodegradable plates and titanium plates, suggesting that biodegradable and titanium plates have the potential for successful use in the fixation of mandibular fractures.

Evaluation of polycaprolactone scaffold degradation for 6 months in vitro and in vivo

The use of polycaprolactone (PCL) as a biomaterial, especially in the fields of drug delivery and tissue engineering, has enjoyed significant growth. Understanding how such a device or scaffold eventually degrades in vivo is paramount as the defect site regenerates and remodels. Degradation studies of three-dimensional PCL and PCL-based composite scaffolds were conducted in vitro (in phosphate buffered saline) and in vivo (rabbit model). Results up to 6 months are reported. All samples recorded virtually no molecular weight changes after 6 months, with a maximum mass loss of only about 7% from the PCL-composite scaffolds degraded in vivo, and a minimum of 1% from PCL scaffolds. Overall, crystallinity increased slightly because of the effects of polymer recrystallization. This was also a contributory factor for the observed stiffness increment in some of the samples, while only the PCL-composite scaffold registered a decrease. Histological examination of the in vivo samples revealed good biocompatibility, with no adverse host tissue reactions up to 6 months. Preliminary results of medical-grade PCL scaffolds, which were implanted for 2 years in a critical-sized rabbit calvarial defect site, are also reported here and support our scaffold design goal for gradual and late molecular weight decreases combined with excellent long-term biocompatibility and bone regeneration.

Injectable biomaterials for regenerating complex craniofacial tissues

Engineering complex tissues requires a precisely formulated combination of cells, spatiotemporally released bioactive factors, and a specialized scaffold support system. Injectable materials, particularly those delivered in aqueous solution, are considered ideal delivery vehicles for cells and bioactive factors and can also be delivered through minimally invasive methods and fill complex 3D shapes. In this review, we examine injectable materials that form scaffolds or networks capable of both replacing tissue function early after delivery and supporting tissue regeneration over a time period of weeks to months. The use of these materials for tissue engineering within the craniofacial complex is challenging but ideal as many highly specialized and functional tissues reside within a small volume in the craniofacial structures and the need for minimally invasive interventions is desirable due to aesthetic considerations. Current biomaterials and strategies used to treat craniofacial defects are examined, followed by a review of craniofacial tissue engineering, and finally an examination of current technologies used for injectable scaffold development and drug and cell delivery using these materials.