Craniofacial Implants Research Articles

Designing patient-specific 3D printed craniofacial implants using a novel topology optimization method

Large craniofacial defects require efficient bone replacements which should not only provide good aesthetics but also possess stable structural function. The proposed work uses a novel multiresolution topology optimization method to achieve the task. Using a compliance minimization objective, patient-specific bone replacement shapes can be designed for different clinical cases that ensure revival of efficient load transfer mechanisms in the mid-face. In this work, four clinical cases are introduced and their respective patient-specific designs are obtained using the proposed method. The optimized designs are then virtually inserted into the defect to visually inspect the viability of the design . Further, once the design is verified by the reconstructive surgeon, prototypes are fabricated using a 3D printer for validation. The robustness of the designs are mechanically tested by subjecting them to a physiological loading condition which mimics the masticatory activity. The full-field strain result through 3D image correlation and the finite element analysis implies that the solution can survive the maximum mastication of 120 lb. Also, the designs have the potential to restore the buttress system and provide the structural integrity. Using the topology optimization framework in designing the bone replacement shapes would deliver surgeons new alternatives for rather complicated mid-face reconstruction.

Review of “Quantitative Analysis of Dual-Purpose, Patient-Specific Craniofacial Implants for Correction of Temporal Deformity” by Zhong S, Huang GJ, Susarla SM, Swanson EW, Huang J, Gordon CR in Neurosurgery 11

Review of “Quantitative Analysis of Dual-Purpose, Patient-Specific Craniofacial Implants for Correction of Temporal Deformity” by Zhong S, Huang GJ, Susarla SM, Swanson EW, Huang J, Gordon CR in Neurosurgery 11

Review of “Quantitative Analysis of Dual-Purpose, Patient-Specific Craniofacial Implants for Correction of Temporal Deformity” by Zhong S, Huang GJ, Susarla SM, Swanson EW, Huang J, Gordon CR in Neurosurgery 11

Review of “Quantitative Analysis of Dual-Purpose, Patient-Specific Craniofacial Implants for Correction of Temporal Deformity” by Zhong S, Huang GJ, Susarla SM, Swanson EW, Huang J, Gordon CR in Neurosurgery 11

Stress analysis of two craniofacial implants in implant retained auricular prostheses.

Implant-retained auricular prostheses require attachments to connect the implants and prostheses. Different attachments have different retention forces and hence different stress is transmitted to the implants. Splinting the implants together with a Hader bar allows the combination of different attachments with the Hader bar and allows changes in the amount and pattern of stress on the implants. However, the amount of removal force is also influenced by the retention components and the direction of removal of the prosthesis. In this paper, we studied the stress distribution around two craniofacial implants, in an auricular prosthesis, according to the removal forces, among three different attachment combinations and evaluated the stress distribution around two craniofacial implants in an auricular prosthesis with removal force at normal direction. The mean removal force was experimentally determined and the models were created using finite element software to analyze the distribution of von-Mises stress. Within the limitations of this study, the prosthodontist should place an emphasis on encouraging patients to remove the prosthesis at 90 degrees and if possible use a low retentive attachment to reduce the stress.

Immediate Single-Stage Cranioplasty Following Calvarial Resection for Benign and Malignant Skull Neoplasms Using Customized Craniofacial Implants.

Craniectomy defects following resection of calvarial lesions are most often reconstructed using on-table manufacturing. With the advent of computer-aided design/manufacturing and customized craniofacial implants (CCIs), there seems to be more suited alternatives. In this study, the authors report their institutional experience and outcome using immediate, single-stage, CCI-based reconstruction for benign and malignant skull neoplasm defects. A retrospective review of a prospectively maintained database of all implant cranioplasties performed between 2011 and 2014, by a single craniofacial surgeon at a tertiary academic medical institution was performed. Preoperative and postoperative computed tomography scans with 3D reconstruction were performed for the purpose of assessing adequate resection and reconstructive outcomes. Primary endpoints included length of surgery, predicted defect versus postoperative implant surface area, contour irregularities, and complications. Of the 108 patients with cranioplasty identified, 7 patients were found to undergo immediate CCI-based reconstruction for calvarial neoplasms; 4 patients (4/7, 57%) presented with malignant pathology. All defects were >5 cm2. As compared with their original size, all implants were modified intraoperatively between 0.2% and 40.8%, with a mean of 13.8%. With follow-up ranging between 1 and 16 months, there were no implant-related complications identified. The immediate and long-term aesthetic results, as well as patient satisfaction, were ideal. With this preliminary experience, the authors have successfully demonstrated that immediate customized implant reconstructive techniques, by way of intraoperative modification, are both safe and feasible for benign and malignant skull neoplasms. The authors believe that with wider acceptance of this multidisciplinary approach and increased surgeon familiarity, this technique will soon become the reconstructive standard of care.

Emerging Applications of Bedside 3D Printing in Plastic Surgery.

Modern imaging techniques are an essential component of preoperative planning in plastic and reconstructive surgery. However, conventional modalities, including three-dimensional (3D) reconstructions, are limited by their representation on 2D workstations. 3D printing, also known as rapid prototyping or additive manufacturing, was once the province of industry to fabricate models from a computer-aided design (CAD) in a layer-by-layer manner. The early adopters in clinical practice have embraced the medical imaging-guided 3D-printed biomodels for their ability to provide tactile feedback and a superior appreciation of visuospatial relationship between anatomical structures. With increasing accessibility, investigators are able to convert standard imaging data into a CAD file using various 3D reconstruction softwares and ultimately fabricate 3D models using 3D printing techniques, such as stereolithography, multijet modeling, selective laser sintering, binder jet technique, and fused deposition modeling. However, many clinicians have questioned whether the cost-to-benefit ratio justifies its ongoing use. The cost and size of 3D printers have rapidly decreased over the past decade in parallel with the expiration of key 3D printing patents. Significant improvements in clinical imaging and user-friendly 3D software have permitted computer-aided 3D modeling of anatomical structures and implants without outsourcing in many cases. These developments offer immense potential for the application of 3D printing at the bedside for a variety of clinical applications. In this review, existing uses of 3D printing in plastic surgery practice spanning the spectrum from templates for facial transplantation surgery through to the formation of bespoke craniofacial implants to optimize post-operative esthetics are described. Furthermore, we discuss the potential of 3D printing to become an essential office-based tool in plastic surgery to assist in preoperative planning, developing intraoperative guidance tools, teaching patients and surgical trainees, and producing patient-specific prosthetics in everyday surgical practice.

Bone and Skin-Supported Stereolithographic Surgical Guides for Cranio-Facial Implant Placement.

Osseointegrated skin-penetrating implants enhance the retention and stability of the craniofacial prostheses and provide the long-term comfort. However, to determine the implant locations is a great challenge facing the surgeon. Implants may either be located in conventional manner or by STL generated surgical guides. Present study reports the CT based 3D virtual modeling, preoperative virtual planning and the implant placement by using a STL surgical guide, in an anotia case. Employed materials and the methods facilitated the implant surgery while improving the operational security. CT based 3D virtual modeling of the surgical site, determining the implant locations virtually and the STL guided placement of the craniofacial implants, were found useful applications in order to facilitating the surgical intervention and providing prevention from complications.

Implant-retained nasal prosthesis

Malignant tumors of the nose occasionally require rhinectomy. Facial defects can cause not only functional problems but also some serious physchological problems that could cause the individual to avoid social contact. In view of this, the first aim of maxillofacial rehabilitation should be solving esthetic problems. Implant retained prostheses can give good esthetic results. Predictable biomechanical retention of nasal prostheses can be achieved using osseointegrated implants and intra-oral and craniofacial implants have been used previously. These prostheses are tissue compatible, simple in design and easy to place, can be worn independently of spectacles and in the majority of cases can be provided soon after surgical excision. In this case report, a nasal prosthesis was fabricated for a patient who lost his nose due to the basal cell carcinoma. Extra-oral implants and magnet retention for the proper connection of the nasal prosthesis were used. This prosthesis was acceptable for the patient because of excellent support, retentive abilities and the patient's appearance.

Bone defects and future regenerative nanomedicine approach using stem cells in the mutant Tabby mouse model.

X-linked Hypohidrotic Ectodermal Dysplasia (XLHED) is associated to a large spectrum of ectodermal and extra-ectodermal symptoms, especially craniofacial bone morphological, structural and metabolic anomalies. This skeletal phenotype described in affected patients and in the Ta mutant mouse model leads to craniofacial dysmorphies, endosseous implants and jaw bone grafts complications. Bone tissue bioengineering based on the use of PCL synthetic nanofibrous membrane and BMP nanoreservoirs appears as an original and promising approach to prevent such complications in the context of dysfunctional bone. Use of osteoblasts or stem cells seeded biomembranes appears as another strategy developed on the Tabby (Ta) model of XLHED. The Ta mouse experimental model is used to study the jaw bone response during the post-operative period after bone lesion and placement of synthetic PCL membrane functionalized with nanoreservoirs embedding different BMPs dimers or seeded with living cells.

Craniofacial reconstruction with poly(methyl methacrylate) customized cranial implants.

Secondary cranioplasty with customized craniofacial implants (CCIs) are often used to restore cerebral protection and reverse syndromes of the trephined, and for reconstruction of acquired cranial deformities. The 2 most widely used implant materials are polyetheretherketone and poly(methylmethacrylate) (PMMA). Previous series with CCIs report several major complications, including implant infection leading to removal, extended hospital stays, and surgical revisions. With this in mind, we chose to review our large case series of 22 consecutive PMMA CCI cranioplasties treated by a single craniofacial surgeon. A cohort of 20 consecutive patients receiving 22 PMMA implants during a 2-year period was identified and outcomes reviewed. The mechanism of initial insult, time from craniectomy to cranioplasty, anesthesia time, major and minor postoperative complications, radiation history, and length of follow-up were statistically analyzed. There were no complications related to infection, hematoma/seroma, or cerebrospinal fluid leak (0/22, 0%). Two patients experienced major complications related to persistent temporal hollowing (PTH) following standard CCI cranioplasty, which required revision surgery with modified implants (2/22, 9%). One minor complication of self-resolving transient diplopia was noted (1/22, 5%). In this consecutive series, PMMA CCIs were associated with a very low complication rate, suggesting that PMMA may be a preferred material for CCI fabrication. However, with 10% (2/20) of patients experiencing PTH and dissatisfaction related to asymmetry, future research must be directed at modifying CCI shape, to address the overlying soft-tissue deformity. If successful, this may increase patient satisfaction, prevent PTH, and avoid additional costs of revision surgery.

Three week loading for the Baha BI-300® implant system

PurposeThe timing of loading of titanium craniofacial implants is dependent upon implant characteristics, host factors, and the bonding of titanium oxide and bone referred to as osseointegration. The purpose of this feasibility study seeks to determine the safety of early loading of the Baha BI-300 implant system (Cochlear Limited, Englewood, CO), which has been modified with novel surface texture and geometric design. Subjects and methodsThis prospective study measures implant stability as determined by clinical evaluation and resonance frequency analysis at implantation and at 1, 3, 6, 12, 24 and 52weeks post-op in 20 patients who underwent single-stage implantation and exteriorization of the BI-300. The processor was loaded at 3weeks post-operatively. A modified Holger’s classification system was used to evaluate skin reactions. ResultsThere was a positive linear trend in mean implant stability scores from implantation to 52weeks. Only one subject (5%) had a mild local soft tissue Holger’s grade 1 score at 24weeks. No implant loss or postoperative complications were encountered as a result of the 3-week loading. ConclusionThree-week loading of the BI-300 implant did not result in any implant loss or failure of osseointegration. Earlier activation of the external processor with earlier hearing rehabilitation resulted in improved patient satisfaction. Further studies are needed to confirm these results for more universal adoption of early loading in adults.

Soft Tissue Response and Survival of Extraoral Implants: A Long-Term Follow-up

Maxillofacial defects may be reconstructed by plastic surgery or treated by prosthetic mean rehabilitation. In case of large defects, prosthetic rehabilitation rather than surgical reconstruction is preferred due to the insufficient esthetic results of surgical interventions. However, retention of the craniofacial prosthesis is a great problem despite the satisfactory esthetic results. With the presentation of extraoral implants, the retention of maxillofacial prostheses was improved, and osseointegrated craniofacial implants have become indispensable for retention and stability. However, there are conflicting results regarding the success rates of osseointegrated implants used at the craniofacial region. A total of 24 patients with 64 implants (30 in auricular region of 13 patients, 24 in nasal region of 8 patients, and 10 in orbital region of 3 patients) ranging in age from 16 to 83 years (mean age = 45.45 years) were evaluated. One patient among 13 patients (1/13) has lost his implants in the auricular area, 1 patient among 8 patients (1/8) lost his implants, and 1 patient among 3 patients (1/3) has lost all of her implants. Peri-implant soft tissue response was evaluated for a 60-month period and a total of 654 visits/sites recorded. Grade 0 (no irritation) was present in 72.8% (476/654) of the visits/sites. Grade 1 (slight redness) was observed for 18.8% (123/654). Grade 2 (red and slightly moist tissue) was scored in 6.9% (45/654). Grade 3 (red and slightly moist tissue with granulation) was noted in 1.5% (10/654) and grade 4 (infection) could not be found. Ossseointegrated implants provide reasonable support and show successful results when used with maxillofacial prostheses.

Experimental validation of 3D printed patient-specific implants using digital image correlation and finite element analysis

With the dawn of 3D printing technology, patient-specific implant designs are set to have a paradigm shift. A topology optimization method in designing patient-specific craniofacial implants has been developed to ensure adequate load transfer mechanism and restore the form and function of the mid-face. Patient-specific finite element models are used to design these implants and to validate whether they are viable for physiological loading such as mastication. Validation of these topology optimized finite element models using mechanical testing is a critical step. Instead of inserting the implants into a cadaver or patient, we embed the implants into the computer-aided skull model of a patient and, fuse them together to 3D print the complete skull model with the implant. Masticatory forces are applied in the molar region to simulate chewing and measure the stress–strain trajectory. Until recently, strain gages have been used to measure strains for validation. Digital Image Correlation (DIC) method is a relatively new technique for full-field strain measurement which provides a continuous deformation field data. The main objective of this study is to validate the finite element model of patient-specific craniofacial implants against the strain data from the DIC obtained during the mastication simulation and show that the optimized shapes provide adequate load-transfer mechanism. Patient-specific models are obtained from CT scans. The principal maximum and minimum strains are compared. The computational and experimental approach to designing patient-specific implants proved to be a viable technique for mid-face craniofacial reconstruction.

Development of oral and extra-oral endosseous craniofacial implants by using a mesh structure for connective tissue attachment.

Connective tissue attachment to a mesh structure incorporated on the surface of oral implants and extra-oral endosseous craniofacial implants (EOECI) was investigated. Two types of implants were prepared: TI and TI-Mesh. TI was composed of an upper and a lower component, both comprised of a titanium cylinder, which could be connected using a titanium screw. The composition of the TIMesh was similar, but the lower cylinder had a lateral groove that was covered with a titanium mesh. In animal experiments performed using rat calvaria, the lower component was first implanted and was left submerged for 3 weeks, then the upper component was mounted percutaneously. After an additional 2 weeks, each implant and the surrounding tissues were harvested and evaluated. Histological observations revealed collagen fibers originating from surrounding hypodermal tissues anchored to the mesh structures of the TI-Mesh whereas no such collagen fibers were observed around TI. Significantly greater values of the attachment strength, the thickness of the dermal tissue, the thickness of hypodermal tissue, and the attachment lengths were observed in TI-Mesh than those of TI. Thus connective tissue attachment with collagen fibers anchored to the mesh was achieved by incorporating mesh structures into the percutaneously placed implants.

The development, fabrication, and material characterization of polypropylene composites reinforced with carbon nanofiber and hydroxyapatite nanorod hybrid fillers

This study focuses on the design, fabrication, microstructural and property characterization, and biocompatibility evaluation of polypropylene (PP) reinforced with carbon nanofiber (CNF) and hydroxyapatite nanorod (HANR) fillers. The purpose is to develop advanced PP/CNF–HANR hybrids with good mechanical behavior, thermal stability, and excellent biocompatibility for use as craniofacial implants in orthopedics. Several material-examination techniques, including X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, tensile tests, and impact measurement are used to characterize the microstructural, mechanical, and thermal properties of the hybrids. Furthermore, osteoblastic cell cultivation and colorimetric assay are also employed for assessing their viability on the composites. The CNF and HANR filler hybridization yields an improvement in Young’s modulus, impact strength, thermal stability, and biocompatibility of PP. The PP/2% CNF–20% HANR hybrid composite is found to exhibit the highest elastic modulus, tensile strength, thermal stability, and biocompatibility.

Electroconvulsive Therapy After Maxillofacial Metallic Implants

A growing body of literature suggests that electroconvulsive therapy (ECT) can be safely utilized in patients with craniofacial metallic implants. Here we provide radiographic images and the clinical course of a 49-year-old woman with both maxillary and mandibular metallic implants who safely received ECT.

Stability and survival of bone-anchored hearing aid implant systems in post-irradiated patients

Bone-anchored hearing aids (BAHAs) are based on the principle of osseointegration, which is fundamental to implant stability and survival. Previous exposure to ionising radiation may compromise this, as evidenced in relation to dental and craniofacial implants. There is a dearth of data, however, regarding BAHA implant systems in patients with previously irradiated implant sites. We sought, therefore, to investigate implant stability and survival in such patients. Patients were identified retrospectively from our electronic BAHA database. Hospital records were reviewed for demographics; operative technique; complications; and details regarding previous irradiation. Implant stability was assessed by resonance frequency analysis (RFA), generating a numerical value-implant stability quotient (ISQ). Extrapolating from dental studies, successfully loaded implants typically have ISQs of ≥60. Readings were, therefore, interpreted with respect to this. Seven patients were identified for inclusion. Mean time between irradiation and implant insertion was 33 months (range 16-72 months), and mean time from implant insertion to RFA measurement was 41 months (range 3-96 months). Operatively, all patients underwent single-stage procedures under local anaesthesia. One patient suffered a Holger's grade 2 skin reaction, while two suffered significant skin flap failure, requiring revision procedures. The implant survival rate was 100 %. All ISQ values were >60, with a mean of 66.9 (95 % confidence interval 63.1-70.6). Our data support sufficient osseointegration of BAHA implant systems in post-irradiated patients, but highlight issues with wound healing. Contemporary soft tissue preservation operative techniques will likely overcome this, facilitating safe and efficacious BAHA insertion in this ever-increasing group of patients.

An overview of recent advances in designing orthopedic and craniofacial implants.

Great deal of research is still going on in the field of orthopedic and craniofacial implant development to resolve various issues being faced by the industry today. Despite several disadvantages of the metallic implants, they continue to be used, primarily because of their superior mechanical properties. In order to minimize the harmful effects of the metallic implants and its by-products, several modifications are being made to these materials, for instance nickel-free stainless steel, cobalt-chromium and titanium alloys are being introduced to eliminate the toxic effects of nickel being released from the alloys, introduce metallic implants with lower modulus, reduce the cost of these alloys by replacing rare elements with less expensive elements etc. New alloys like tantalum, niobium, zirconium, and magnesium are receiving attention given their satisfying mechanical and biological properties. Non-oxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation. Recent advances in orthobiologics are proving interesting as well. This paper thus deals with the latest improvements being made to the existing implant materials and includes new materials being introduced in the field of biomaterials.

Manufacture of Accurate Titanium Cranio-Facial Implants with High Forming Angle Using Single Point Incremental Forming

One of the key application areas of Single Point Incremental Forming is in the manufacture of parts for bio-medical applications. This paper discusses the challenges associated with the manufacture of cranio-facial implants with extreme forming angles using medical grade titanium sheets. While on one hand, the failure wall angle is an issue of concern, the parts also need to be manufactured with accuracy at the edges where the implants fit into the human body. Systematic steps taken to overcome these challenges, using intelligent intermediate part design, feature analysis and compensation, are discussed. A number of case studies illustrating the manufacture of accurate parts in aluminium, stainless steel and titanium grade-2 alloy are discussed.

Extraoral implants in irradiated pacients

The aim of this study is to analyze the success of extraoral osseointegrated implants used to support and contain prosthesis designed to rehabilitate craniofacial deformities. MethodThis study was based on the retrospective assessment of charts from 59 patients submitted to cancer surgery and who received 164 extraoral implants to contain facial prosthesis. ResultsAmong 164 implants, 42 were fixed in previously irradiated regions. Eight of the implants did not have osseointegration; and from these, 2 were fixed in irradiated bone. The result show 116 (95.1%) successfully osseointegrated implants in non-irradiated sites. The success rate among 42 implants fixed in previously irradiated bones was 40 (95.3%) osseointegrated implants. ConclusionThe use of extraoral craniofacial implants represents a safe and effective approach to treat facial deformities as a support for the rehabilitation prosthesis. Radiotherapy treatment does not prevent osseointegration.