3D Printing Applications for Craniomaxillofacial Reconstruction: A Sweeping Review

The field of craniomaxillofacial (CMF) surgery is rich in pathological diversity and broad in the ages that it treats. Moreover, the CMF skeleton is a complex confluence of sensory organs and hard and soft tissue with load-bearing demands that can change within millimeters. Computer-aided design (CAD) and additive manufacturing (AM) create extraordinary opportunities to repair the infinite array of craniomaxillofacial defects that exist because of the aforementioned circumstances. 3D printed scaffolds have the potential to serve as a comparable if not superior alternative to the "gold standard" autologous graft. In vitro and in vivo studies continue to investigate the optimal 3D printed scaffold design and composition to foster bone regeneration that is suited to the unique biological and mechanical environment of each CMF defect. Furthermore, 3D printed fixation devices serve as a patient-specific alternative to those that are available off-the-shelf with an opportunity to reduce operative time and optimize fit. Similar benefits have been found to apply to 3D printed anatomical models and surgical guides for preoperative or intraoperative use. Creation and implementation of these devices requires extensive preclinical and clinical research, novel manufacturing capabilities, and strict regulatory oversight. Researchers, manufacturers, CMF surgeons, and the United States Food and Drug Administration (FDA) are working in tandem to further the development of such technology within their respective domains, all with a mutual goal to deliver safe, effective, cost-efficient, and patient-specific CMF care. This manuscript reviews FDA regulatory status, 3D printing techniques, biomaterials, and sterilization procedures suitable for 3D printed devices of the craniomaxillofacial skeleton. It also seeks to discuss recent clinical applications, economic feasibility, and future directions of this novel technology. By reviewing the current state of 3D printing in CMF surgery, we hope to gain a better understanding of its impact and in turn identify opportunities to further the development of patient-specific surgical care.

Treatment of traumatic cranial fracture with sonic activated polymer pins and plates resorbable implants in a dog

INTRODUCTION

The case report describes the use of ultrasound-activated resorbable implants for surgical repair of comminuted cranial fractures in a 10 years old medium sized mix-breed dog being injured from a horse kick.

Molybdenum as a Potential Biocompatible and Resorbable Material for Osteosynthesis in Craniomaxillofacial Surgery-An In Vitro Study

Titanium and stainless steel are commonly known as osteosynthesis materials with high strength and good biocompatibility. However, they have the big disadvantage that a second operation for hardware removal is necessary. Although resorbable systems made of polymers or magnesium are increasingly used, they show some severe adverse foreign body reactions or unsatisfying degradation behavior. Therefore, we started to investigate molybdenum as a potential new biodegradable material for osteosynthesis in craniomaxillofacial surgery. To characterize molybdenum as a biocompatible material, we performed in vitro assays in accordance with ISO Norm 10993-5. In four different experimental setups, we showed that pure molybdenum and molybdenum rhenium alloys do not lead to cytotoxicity in human and mouse fibroblasts. We also examined the degradation behavior of molybdenum by carrying out long-term immersion tests (up to 6 months) with molybdenum sheet metal. We showed that molybdenum has sufficient mechanical stability over at least 6 months for implants on the one hand and is subject to very uniform degradation on the other. The results of our experiments are very promising for the development of new resorbable osteosynthesis materials for craniomaxillofacial surgery based on molybdenum.

Virtual Surgical Planning and 3D-Printed Surgical Guides in Facial Allotransplantation

The complex three-dimensional (3D) anatomy in facial allotransplantation creates a unique challenge for surgical reconstruction. Evolution of virtual surgical planning (VSP) through computer-aided design and computer-aided manufacturing has advanced reconstructive outcomes for many craniomaxillofacial indications. Surgeons use VSP, 3D models, and surgical guides to analyze and to trial surgical approaches even prior to entering the operating room. This workflow allows the surgeon to plan osteotomies and to anticipate challenges, which improves surgical precision and accuracy, optimizes outcomes, and should reduce operating room time. We present the development, evolution, and utilization of VSP and 3D-printed guides in facial allotransplantation at our institution, from guide conception to first clinical case.

Black Bone MRI for Virtual Surgical Planning in Craniomaxillofacial Surgery

Advances in computer-aided design and computer-aided manufacturing software have improved translational applications of virtual surgical planning (VSP) in craniomaxillofacial surgery, allowing for precise and accurate fabrication of cutting guides, stereolithographic models, and custom implants. High-resolution computed tomography (CT) imaging has traditionally been the gold standard imaging modality for VSP in craniomaxillofacial surgery but delivers ionizing radiation. Black bone magnetic resonance imaging (MRI) reduces the risks related to radiation exposure and has comparable functionality when compared with CT for VSP. Our group has studied the accuracy of utilizing black bone MRI in planning and executing several types of craniofacial surgeries, including cranial vault remodeling, maxillary advancement, and mandibular reconstruction using fibular bone. Here, we review clinical applications of black bone MRI pertaining to VSP and three-dimensional (3D)-printed guide creation for craniomaxillofacial surgery. Herein, we review the existing literature and our institutional experience comparing black bone MRI and CT in VSP-generated 3D model creation in cadaveric craniofacial surgeries including cranial vault reconstruction, maxillary advancement, and mandibular reconstruction with fibular free flap. Cadaver studies have demonstrated the ability to perform VSP and execute the procedure based on black bone MRI data and achieve outcomes similar to CT when performed for cranial vault reshaping, maxillary advancement, and mandibular reconstruction with free fibula. Limitations of the technology include increased time and costs of the MRI compared with CT and the possible need for general anesthesia or sedation in the pediatric population. VSP and 3D surgical guide creation can be performed using black bone MRI with comparable accuracy to high-resolution CT scans in a wide variety of craniofacial reconstructions. Successful segmentation, VSP, and 3D printing of accurate guides from black bone MRI demonstrate potential to change the preoperative planning standard of care. Black bone MRI also reduces exposure to ionizing radiation, which is of particular concern for the pediatric population or patients undergoing multiple scans.

Application of mixed reality-based surgical navigation system in craniomaxillofacial trauma bone reconstruction

OBJECTIVES

This study aimed to build a surgical navigation system based on mixed reality (MR) and optical positioning technique and evaluate its clinical applicability in craniomaxillofacial trauma bone reconstruction. Me-thods We first integrated the software and hardware platforms of the MR-based surgical navigation system and explored the system workflow. The systematic error, target registration error, and osteotomy application error of the system were then analyzed via 3D printed skull model experiment. The feasibility of the MR-based surgical navigation system in craniomaxillofacial trauma bone reconstruction was verified via zygomatico-maxillary complex (ZMC) reduction experiment of the skull model and preliminary clinical study.

RESULTS

The system error of this MR-based surgical navigation system was 1.23 mm±0.52 mm, the target registration error was 2.83 mm±1.18 mm, and the osteotomy application error was 3.13 mm±1.66 mm. Virtual surgical planning and the reduction of the ZMC model were successfully conducted. In addition, with the guidance of the MR-based navigation system, the frontal bone defect was successfully reconstructed, and the clinical outcome was satisfactory.

CONCLUSIONS

The MR-based surgical navigation system has its advantages in virtual reality fusion effect and dynamic navigation stability. It provides a new method for doctor-patient communications, education, preoperative planning, and intraoperative navigation in craniomaxillofacial surgery.

Geometric accuracy of magnetic resonance imaging-derived virtual 3-dimensional bone surface models of the mandible in comparison to computed tomography and cone beam computed tomography: A porcine cadaver study

BACKGROUND

Providing accurate 3-dimensional virtual bone surface models is a prerequisite for virtual surgical planning and additive manufacturing in craniomaxillofacial surgery. For this purpose, magnetic resonance imaging (MRI) may be a radiation-free alternative to computed tomography (CT) and cone beam computed tomography (CBCT).

PURPOSE

The aim of this study was to assess the geometric accuracy of 3-dimensional T1-weighted MRI-derived virtual bone surface models of the mandible in comparison to CT and CBCT.

MATERIALS AND METHODS

Specimens of the mandible from porcine cadavers were scanned with (1) a 3-dimensional T1-weighted MRI sequence (0.6 mm isotropic voxel) optimized for bone imaging, (2) CT, and (3) CBCT. Cortical mandibular structures (n = 10) were segmented using semiautomated and manual techniques. Imaging-based virtual 3-dimensional models were aligned with a high-resolution optical 3-dimensional surface scan of the dissected bone (=ground truth) and global geometric deviations were calculated (mean surface distance [MSD]/root-mean-square distance [RMSD]). Agreement between the imaging modalities was assessed by equivalence testing and Bland-Altman analysis.

RESULTS

Intra- and inter-rater agreement was on a high level for all modalities. Global geometric deviations (MSD/RMSD) between optical scans and imaging modalities were 0.225 ± 0.020 mm/0.345 ± 0.074 mm for CT, 0.280 ± 0.067 mm/0.371 ± 0.074 mm for MRI, and 0.352 ± 0.076 mm/0.454 ± 0.071 mm for CBCT. All imaging modalities were statistically equivalent within an equivalence margin of ±0.3 mm, and Bland-Altman analysis indicated high agreement as well.

CONCLUSIONS

The results of this study indicate that the accuracy and reliability of MRI-derived virtual 3-dimensional bone surface models is equal to CT and CBCT. MRI may be considered as a reliable alternative to CT and CBCT in computer-assisted craniomaxillofacial surgery.

Maxillary Sinus Floor Infiltration: Results From a Series of 118 Maxillary Sinus Cancers

OBJECTIVES/HYPOTHESIS

Maxillary cancers are rare and aggressive tumors, which can spread beyond the sinus bony walls. Preoperative assessment of infiltration of maxillary sinus floor (MSF) is paramount for surgical planning, as palatomaxillary demolition significantly impacts patients' quality of life. This study investigates the challenges involved in the preoperative and intraoperative evaluation of MSF infiltration and analyzes its prognostic relevance.

STUDY DESIGN

Retrospective case series.

METHODS

A retrospective review of patients treated for sinonasal malignancies at a single Institution was performed. Patients receiving surgical-based treatment with curative intent for primary maxillary sinus cancers, between January 2000 and November 2019, were included.

RESULTS

A cohort of 118 patients was analyzed. By comparing intraoperative findings (endoscopic assessment and frozen sections) with preoperative radiological assessment, diagnostic changes with regard to MSF infiltration were found in 27.1% (32/118 cases). MSF infiltration negatively affected the prognosis in both univariate and multivariate analyses in the overall population. In the subgroup of pT1-T3 tumors, MSF infiltration was significantly associated with reduced overall (P = .012), disease-free (P = .011), and distant recurrence-free (P = .002) survival rates. Conversely, pT classification was not able to stratify patients according to prognosis, mainly because early-staged cancers (pT1-T2) with MSF infiltration showed reduced survival rates, similar to those observed in pT3 cancers.

CONCLUSIONS

Preoperative imaging should be integrated with intraoperative findings based on endoscopic inspection and frozen sections. Future studies are required to investigate the opportunity to incorporate MSF infiltration in the TNM staging system, considering its crucial role in defining the extent of surgery and its potential as prognosticator.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

Venous superdrainage using superficial circumflex iliac vein in deep circumflex iliac artery perforator flap with iliac crest for oromandibular reconstruction

The deep circumflex iliac artery perforator flap with iliac crest (DCIAPF) is considered a favourable single-flap option for oromandibular reconstruction. The aim of this study was to evaluate the effectiveness of venous superdrainage using the superficial circumflex iliac vein (SCIV) in the DCIAPF for oromandibular reconstruction. The data of 22 patients (12 female, 10 male) aged 10-76 years (median 53 years) who underwent simultaneous oromandibular reconstruction with a DCIAPF were reviewed retrospectively. Eleven patients received the DCIAPF with SCIV for superdrainage (group A) and another 11 patients received the conventional single-pedicled DCIAPF flap (group B). No flap loss occurred in either group. Venous congestion due to relative venous insufficiency was significantly more frequent in group B (P=0.045). There was no significant difference in the incidence of partial flap necrosis and wound dehiscence, or in the total operation time between the two groups. Superdrainage using the SCIV has the potential to reduce the incidence of venous congestion due to relative venous insufficiency in DCIAPF used for oromandibular reconstruction.

Craniomaxillofacial Trauma Experience in Otolaryngology Residency: A National Survey of Program Directors

This article aimed to assess the depth and volume of craniomaxillofacial (CMF) trauma exposure and education in otolaryngology residency training in the United States. This is a cross-sectional survey. A 15-question web-based survey was distributed to program directors of 106 Accreditation Council for Graduate Medical Education (ACGME)-approved otolaryngology residency programs to inquire about program size and demographics, trauma coverage, case volume, and education. Responses were collected anonymously. A total of 77 responses were received, representing 73% of residency programs. Seventy-five programs (97%) reported that their residents rotated at a level 1 trauma center, and 72 (94%) covered CMF trauma. Sixty-one programs (79%) included pediatric CMF trauma. The majority of programs (76%) allocated less than 10% of residency-dedicated didactic lecture time to CMF trauma. Residents in all programs typically logged at least 11 to 20 cases before graduation with 24% of programs averaging more than 50 cases per resident. Ninety percent of respondents described the training as "somewhat" to "very adequate." CMF coverage by the otolaryngology department, number of cases, and dedicated didactic lecture time to CMF trauma were significant factors on the perception of adequate training. The majority of program directors felt that the training in CMF trauma was adequate. Reasons for this may include that most residents rotate at level 1 trauma centers, have exposure to pediatric trauma, encounter an adequate volume of cases, and have dedicated didactic time to CMF education.

Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties

Understanding the function of oral mucosal epithelial barriers is essential for a plethora of research fields such as tumor biology, inflammation and infection diseases, microbiomics, pharmacology, drug delivery, dental and biomarker research. The barrier properties are comprised by a physical, a transport and a metabolic barrier, and all these barrier components play pivotal roles in the communication between saliva and blood. The sum of all epithelia of the oral cavity and salivary glands is defined as the blood-saliva barrier. The functionality of the barrier is regulated by its microenvironment and often altered during diseases. A huge array of cell culture models have been developed to mimic specific parts of the blood-saliva barrier, but no ultimate standard in vitro models have been established. This review provides a comprehensive overview about developed in vitro models of oral mucosal barriers, their applications, various cultivation protocols and corresponding barrier properties.

Penetrating Foreign Bodies in Head and Neck Trauma: A Surgical Challenge

Penetrating foreign bodies of different origins in the head and neck are rare and potentially dangerous injuries, which might pose problems for their detection, primary care, and final treatment. Depending on the severity of the underlying trauma, some injuries present a higher risk for the presence of foreign bodies. Minor wounds, including common lacerations, are likely to be contaminated with loose gravel debris or dental fragments, and need to be distinguished from severe wounds caused by impalement, shootings, stabbings, and explosions. Blast injuries resulting from terror attacks are challenging recent therapeutic concepts. Even though these injury patterns are uncommon, they carry the risk of impacted objects with dramatic consequences. Despite improving medical imaging techniques, detection remains a challenge as it is dependent on the material of the foreign body, the affected anatomical site, and the injury severity. Therefore, a detailed history of the circumstances leading to trauma is essential when foreign objects are not visible during clinical examination. Precise detection of the foreign body, its anatomical position, and the affected surrounding structures are vital, especially for impalement injuries of the head and neck area. Therefore, an interdisciplinary planning approach is essential prior to removal of the foreign object. Finally, tension-free anatomical adaptation of the corresponding structures is crucial for maintaining and restoring aesthetic and function. Here, we give an overview of the diagnosis and treatment of cases of foreign body injuries encountered in our department.

[Application and development of surgical robot systems in craniomaxillofacial surgery]

Traditional craniomaxillofacial surgery significantly affects aesthetic appreciation. In contrast to traditional methods, robot-assisted surgery has been extensively investigated because it is microinvasive, precise, and safe. With robot-assisted surgery, operational vision and manipulation space become extended. As a result, operational quality and patient's postoperative life are improved. This article reviewed the development of surgical robot systems and their applications in craniomaxillofacial surgery.

Surgical treatment of polyostotic craniomaxillofacial fibrous dysplasia in adult: a case report and review of the literature

The lesions of fibrous dysplasia usually stabilize after adolescence, and the surgical treatment of adult patient remains the mainstay. However, the surgical treatment alone may be not enough for patient with polyostotic fibrous dysplasia. We present the case of a surgically treated 36-year-old man with a diagnosis of progressive polyostotic fibrous dysplasia in the craniomaxillofacial region. The patients presented the swelling symptoms originally in the parietal bone at the age of 8 years, and extended gradually to almost all of the craniomaxillofacial bones during the following 28 years without specific treatment for socio-economic reasons. The symptom impelled the patient visit our department in 2009 was the rapidly progressive swelling in the chin during the last 3 years, which severely impacted his speech and feeding. The radiographs showed the typical intramedullary located and ill-defined lesions. The patient was treated with segmental mandibulectomy and reconstruction with vascularized fibular myocutaneous flap; the deformities in other craniomaxillofacial bones were not treated simultaneously. The local recurrence was not present in the chin. The visual acuity of right eye severely deteriorated and the left mandibular ramus continued expanding gradually when the patient was followed up through telephone 5 years later. A combination of surgical and medical treatment may be considered for patients with polyostotic craniomaxillofacial fibrous dysplasia.

In vivo bioreactors for mandibular reconstruction

Large mandibular defects are difficult to reconstruct with good functional and aesthetic outcomes because of the complex geometry of craniofacial bone. While the current gold standard is free tissue flap transfer, this treatment is limited in fidelity by the shape of the harvested tissue and can result in significant donor site morbidity. To address these problems, in vivo bioreactors have been explored as an approach to generate autologous prefabricated tissue flaps. These bioreactors are implanted in an ectopic site in the body, where ossified tissue grows into the bioreactor in predefined geometries and local vessels are recruited to vascularize the developing construct. The prefabricated flap can then be harvested with vessels and transferred to a mandibular defect for optimal reconstruction. The objective of this review article is to introduce the concept of the in vivo bioreactor, describe important preclinical models in the field, summarize the human cases that have been reported through this strategy, and offer future directions for this exciting approach.

Preliminary development of a workstation for craniomaxillofacial surgical procedures: introducing a computer-assisted planning and execution system

INTRODUCTION

Facial transplantation represents one of the most complicated scenarios in craniofacial surgery because of skeletal, aesthetic, and dental discrepancies between donor and recipient. However, standard off-the-shelf vendor computer-assisted surgery systems may not provide custom features to mitigate the increased complexity of this particular procedure. We propose to develop a computer-assisted surgery solution customized for preoperative planning, intraoperative navigation including cutting guides, and dynamic, instantaneous feedback of cephalometric measurements/angles as needed for facial transplantation and other related craniomaxillofacial procedures.

METHODS

We developed the Computer-Assisted Planning and Execution (CAPE) workstation to assist with planning and execution of facial transplantation. Preoperative maxillofacial computed tomography (CT) scans were obtained on 4 size-mismatched miniature swine encompassing 2 live face-jaw-teeth transplants. The system was tested in a laboratory setting using plastic models of mismatched swine, after which the system was used in 2 live swine transplants. Postoperative CT imaging was obtained and compared with the preoperative plan and intraoperative measures from the CAPE workstation for both transplants.

RESULTS

Plastic model tests familiarized the team with the CAPE workstation and identified several defects in the workflow. Live swine surgeries demonstrated utility of the CAPE system in the operating room, showing submillimeter registration error of 0.6 ± 0.24 mm and promising qualitative comparisons between intraoperative data and postoperative CT imaging.

CONCLUSIONS

The initial development of the CAPE workstation demonstrated that integration of computer planning and intraoperative navigation for facial transplantation are possible with submillimeter accuracy. This approach can potentially improve preoperative planning, allowing ideal donor-recipient matching despite significant size mismatch, and accurate surgical execution for numerous types of craniofacial and orthognathic surgical procedures.