Overcoming cross-gender differences and challenges in Le Fort-based, craniomaxillofacial transplantation with enhanced computer-assisted technology

Immunologic Outcomes in Cross-Sex Solid Organ Transplants: A Systematic Review and Meta-Analysis to Inform Vascularized Composite Allotransplantation

BACKGROUND

Of nearly 90 hand and 50 face transplant recipients, only five have received a cross-sex vascularized composite allotransplantation (CS-VCA). CS-VCA has the potential to expand the donor pool and has been proven anatomically feasible and ethically acceptable in previous studies. However, there is a lack of immunologic data. This study evaluated the immunologic feasibility of CS-VCA through analysis of the solid organ transplant literature, given the paucity of CS-VCA data. The authors hypothesize that rates of acute rejection (AR) and graft survival (GS) in CS versus same-sex (SS) solid organ transplantation are similar.

METHODS

A systematic review and meta-analysis were performed. Studies comparing GS or AR episodes in CS and SS adult kidney (KT) and liver transplant (LT) populations were included. Odds ratios were calculated for overall GS and AR for all SS and CS transplant combinations [male-to-female (MTF), female-to-male, and overall].

RESULTS

A total of 693 articles were initially identified with 25 included in the meta-analysis. No significant difference in GS was noted between SS-KT versus CS-KT [OR, 1.04 (95% CI, 1.00 to 1.07); P = 0.07), SS-KT versus MTF-KT [OR, 0.97 (95% CI, 0.90 to 1.04); P = 0.41), and SS-LT versus MTF-LT [OR, 0.95 (95% CI, 0.91 to 1.00); P = 0.05). No significant difference in AR was noted between SS-KT versus MTF-KT [OR, 0.99 (95% CI, 0.96 to 1.02); P = 0.57), SS-LT versus CS-LT [OR, 0.78 (95% CI, 0.53 to 1.16); P = 0.22], or SS-LT versus female-to-male LT [OR, 1.03 (95% CI, 0.95 to 1.12); P = 0.47]. For the remaining pairings, GS was significantly increased and AR was significantly decreased in the SS transplants.

CONCLUSIONS

Published data suggest immunologic feasibility of CS-KT and CS-LT with the potential for generalization to the VCA population.

CLINICAL RELEVANCE STATEMENT

In theory, CS-VCA could expand the potential donor pool, ultimately leading to decreased wait times for recipients and improve the likelihood of establishing a immunologically favorable donor-recipient match.

Maxillary and Mandibular Healing After Facial Allotransplantation

INTRODUCTION

Facial transplantation has emerged as a viable option in treating devastating facial injuries.Despite the high healing rate of Le Fort III and bilateral sagittal split osteotomies (BSSO) in nontransplant patients, few studies have reported assessment of maxillary and mandibular healing in face transplant patients compared with nontransplant patients. The aim of this study was to examine differences in bone healing in our patients.

PATIENTS AND METHODS

A retrospective chart review was conducted of facial allotransplantation patients at the Cleveland Clinic from December 2008 to inception. Demographics such as age, date of birth, and sex were recorded. Additional variables included procedures, revisions, reoperations, medications, and bone stability and healing. Computed tomography (CT) images assessed the alignment of skeletal components, bony union quality, and stability of fixation.

RESULTS

Three patients were included: 2 had Le Fort III segment transplantation, and 1 had transplantation of both a Le Fort III segment and mandibular BSSO. The Le Fort III segment in all patients exhibited mobility and fibrous union at the Le Fort III osteotomy on CT. In contrast, the BSSO healed uneventfully after transplantation and revision surgery, with bony union confirmed by both CT and histology of the fixation area between the donor and recipient mandible bilaterally. No patients with midfacial fibrous union required revision of the nonunion as they were clinically asymptomatic.

CONCLUSION

Le Fort osteotomy demonstrates inferior healing in facial transplantation compared with the nontransplant population. In contrast, the successful healing in the mandible is likely owing to the high density of rich cancellous bone.

Public Perceptions of Cross-Sex Vascularized Composite Allotransplantation

BACKGROUND

Cross-sex vascularized composite allotransplantation has been performed in cadaveric facial transplantation and clinical extremity transplantation. Understanding the challenge of appropriate donor-recipient matching, this study sought to characterize the public's perception of cross-sex vascularized composite allotransplantation.

METHODS

Participants were surveyed in New York City. Data collected included demographics and willingness to donate vascularized composite allografts (VCAs) of various types. Similar questions were asked in the context of same-sex and cross-sex donation.

RESULTS

A total of 101 participants (male: 56.4%; age ≤35 years: 62.4%) were surveyed. The majority expressed willingness to donate to recipients of a different sex (hand: 78.2%, face: 56.4%, penis or uterus: 69.3%, lower limb: 81.2%, abdominal wall: 80.2%, larynx: 81.2%, and solid organs: 85.2%). Among VCAs, willingness to donate facial allografts was significantly different in same-sex versus cross-sex contexts (64.4% vs 56.4%; P = 0.008). Participants were also significantly more likely to donate VCAs to same-sex recipients on behalf of themselves versus loved ones (P < 0.05). There was significantly lower willingness to receive cross-sex versus same-sex facial (P = 0.022) and genital allografts (P = 0.022). Education on the preservation of recipient masculinity or femininity in cross-sex facial transplantation increased participants' willingness to receive a cross-sex face transplant from 56.4% to 71.3% (P = 0.001).

CONCLUSIONS

This study highlights the urban public's acceptance of VCA donation or reception regardless of sex mismatch. There is increased willingness to receive a cross-sex face transplant after education, highlighting opportunities for future focused interventions to increase public awareness and ultimately the donor pool.

Equity in access to facial transplantation

We examine ethical considerations in access to facial transplantation (FT), with implications for promoting health equity. As a form of vascularised composite allotransplantation, FT is still considered innovative with a relatively low volume of procedures performed to date by a small number of active FT programmes worldwide. However, as numbers continue to increase and institutions look to establish new FT programmes, we anticipate that attention will shift from feasibility towards ensuring the benefits of FT are equitably available to those in need. This manuscript assesses barriers to care and their ethical implications across a number of considerations, with the intent of mapping various factors relating to health equity and fair access to FT. Evidence is drawn from an evolving clinical experience as well as published scholarship addressing several dimensions of access to FT. We also explore novel concerns that have yet to be mentioned in the literature.

Feasibility and Perception of Cross-sex Face Transplantation to Expand the Donor Pool

Background:

A major challenge in face transplantation (FT) is the limited donor allograft pool. This study aimed to investigate the feasibility of cross-sex FT (CSFT) for donor pool expansion by: (1) comparing craniomaxillofacial metrics following CSFT versus same-sex FT (SSFT); and (2) evaluating the public and medical professionals’ perception of CSFT.

Methods:

Seven cadaveric FTs were performed, resulting in both CSFT and SSFT. Precision of bony and soft tissue inset was evaluated by comparing pre- versus post-operative cephalometric and anthropometric measurements. Fidelity of the FT compared to the virtual plan was assessed by imaging overlay techniques. Surveys were administered to medical professionals, medical students, and general population to evaluate opinions regarding CSFT.

Results:

Five CSFTs and 2 SSFTs were performed. Comparison of recipients versus post-transplant outcomes showed that only the bigonial and medial intercanthal distances were statistically different between CSFT and SSFT (P = 0.012 and P = 0.010, respectively). Of the 213 survey participants, more were willing to donate for and undergo SSFT, compared with CSFT (donate: 59.6% versus 53.0%, P = 0.001; receive: 79.5% versus 52.3%, P < 0.001). If supported by research, willingness to receive a CSFT significantly increased to 65.6% (P < 0.001). On non-blinded and blinded assessments, 62.9% and 79% of responses rated the CSFT superior or equal to SSFT, respectively.

Conclusions:

Our study demonstrates similar anthropometric and cephalometric outcomes for CSFT and SSFT. Participants were more reticent to undergo CSFT, with increased willingness if supported by research. CSFT may represent a viable option for expansion of the donor pool in future patients prepared to undergo transplantation.

Ethicists' Opinions Regarding the Permissibility of Face Transplant

BACKGROUND

Face transplantation can offer functional and aesthetic restoration to patients who have exhausted their reconstructive options, improving quality of life and psychosocial integration. Ethical issues in face transplantation abound, including questions of patient selection and evaluation before transplantation. To date, there has been no study of ethicists' opinions regarding face transplantation.

METHODS

An online survey of attendees of the 2015 International Conference on Clinical Ethics Consultation (n = 401) assessed ethicists' opinions about face transplantation. Questions examined the risk-to-benefit ratio of immunosuppression; permissibility of face transplantation in subpopulations (including children and blind patients); donor-recipient age, sex, and ethnicity mismatches; and ethical oversight.

RESULTS

Most ethicists (84 percent) agreed that it is permissible to perform a face transplantation on an adult in the absence of clear medical contraindications. Most respondents also agreed that it is permissible to perform a face transplantation on a child (62 percent) or a blind patient (61 percent), yet demonstrated less consensus regarding the permissibility of performing a face transplantation on patients with an increased risk of immune rejection. Respondents were generally supportive of age, sex, and ethnicity mismatches, with 43 percent indicating that it is permissible to have a sex mismatch. The majority answered that face transplantation should be covered by federal insurance (74 percent).

CONCLUSIONS

This study provides insight into clinical ethicists' views regarding face transplantation. Most ethicists support the ethical permissibility of face transplantation, and did not have concerns about age, sex, and ethnicity mismatches. These findings highlight emerging areas of consensus regarding the ethical permissibility of face transplantation.

Experimental Design for Composite Face Transplantation

Face allotransplantation represents a novel frontier in complex human facial defect reconstruction. To develop more refined surgical techniques and yield fine results, it is first imperative to make a suitable animal model. The development of a composite facial allograft model in swine is more appealing: the facial anatomy, including facial nerve and vascular anatomy, is similar to that of humans. Two operative teams performed simultaneously, one assigned to harvest the donor and the other to prepare the recipient in efforts to shorten operative time. The flap was harvested with the common carotid artery and external jugular vein, and it was transferred to the recipient. After insetting the maxilla, mandible, muscles, and skins, the anastomosis of the external jugular vein, external carotid artery, and facial nerve were performed. The total mean time of transplantation was 7 hours, and most allografts survived without vascular problems. The authors documented that this model is well qualified to be used as a standard transplantation training model and future research work, in every aspect.

Ancillary procedures necessary for translational research in experimental craniomaxillofacial surgery

INTRODUCTION

Swine are often regarded as having analogous facial skeletons to humans and therefore serve as an ideal animal model for translational investigation. However, there is a dearth of literature describing the pertinent ancillary procedures required for craniomaxillofacial research. With this in mind, our objective was to evaluate all necessary procedures required for perioperative management and animal safety related to experimental craniomaxillofacial surgical procedures such as orthotopic, maxillofacial transplantation.

METHODS

Miniature swine (n = 9) were used to investigate perioperative airway management, methods for providing nutrition, and long-dwelling intravenous access. Flap perfusion using near-infrared laser angiography and facial nerve assessment with electromyoneurography were explored.

RESULTS

Bivona tracheostomy was deemed appropriate versus Shiley because soft, wire-reinforced tubing reduced the incidence of tracheal necrosis. Percutaneous endoscopic gastrostomy tube, as opposed to esophagostomy, provided a reliable route for postoperative feeding. Femoral venous access with dorsal tunneling proved to be an ideal option being far from pertinent neck vessels. Laser angiography was beneficial for real-time evaluation of graft perfusion. Facial electromyoneurography techniques for tracing capture were found most optimal using percutaneous leads near the oral commissure.Experience shows that ancillary procedures are critical, and malpositioning of devices may lead to irreversible sequelae with premature animal death.

CONCLUSIONS

Face-jaw-teeth transplantation in swine is a complicated procedure that demands special attention to airway, feeding, and intravascular access. It is critical that each ancillary procedure be performed by a dedicated team familiar with relevant anatomy and protocol. Emphasis should be placed on secure skin-level fixation for all tube/lines to minimize risk for dislodgement. A reliable veterinarian team is invaluable and critical for long-term success.

Optimizing Hybrid Occlusion in Face-Jaw-Teeth Transplantation: A Preliminary Assessment of Real-Time Cephalometry as Part of the Computer-Assisted Planning and Execution Workstation for Craniomaxillofacial Surgery

BACKGROUND

The aesthetic and functional outcomes surrounding Le Fort-based, face-jaw-teeth transplantation have been suboptimal, often leading to posttransplant class II/III skeletal profiles, palatal defects, and "hybrid malocclusion." Therefore, a novel technology-real-time cephalometry-was developed to provide the surgical team instantaneous, intraoperative knowledge of three-dimensional dentoskeletal parameters.

METHODS

Mock face-jaw-teeth transplantation operations were performed on plastic and cadaveric human donor/recipient pairs (n = 2). Preoperatively, cephalometric landmarks were identified on donor/recipient skeletons using segmented computed tomographic scans. The computer-assisted planning and execution workstation tracked the position of the donor face-jaw-teeth segment in real time during the placement/inset onto recipient, reporting pertinent hybrid cephalometric parameters from any movement of donor tissue. The intraoperative data measured through real-time cephalometry were compared to posttransplant measurements for accuracy assessment. In addition, posttransplant cephalometric relationships were compared to planned outcomes to determine face-jaw-teeth transplantation success.

RESULTS

Compared with postoperative data, the real-time cephalometry-calculated intraoperative measurement errors were 1.37 ± 1.11 mm and 0.45 ± 0.28 degrees for the plastic skull and 2.99 ± 2.24 mm and 2.63 ± 1.33 degrees for the human cadaver experiments. These results were comparable to the posttransplant relations to planned outcome (human cadaver experiment, 1.39 ± 1.81 mm and 2.18 ± 1.88 degrees; plastic skull experiment, 1.06 ± 0.63 mm and 0.53 ± 0.39 degrees).

CONCLUSION

Based on this preliminary testing, real-time cephalometry may be a valuable adjunct for adjusting and measuring "hybrid occlusion" in face-jaw-teeth transplantation and other orthognathic surgical procedures.

Restoration of the donor face after facial allotransplantation: digital manufacturing techniques

INTRODUCTION

Current protocols for facial transplantation include the mandatory fabrication of an alloplastic "mask" to restore the congruency of the donor site in the setting of "open casket" burial. However, there is currently a paucity of literature describing the current state-of-the-art and available options.

METHODS

During this study, we identified that most of donor masks are fabricated using conventional methods of impression, molds, silicone, and/or acrylic application by an experienced anaplastologist or maxillofacial prosthetics technician. However, with the recent introduction of several enhanced computer-assisted technologies, our facial transplant team hypothesized that there were areas for improvement with respect to cost and preparation time.

RESULTS

The use of digital imaging for virtual surgical manipulation, computer-assisted planning, and prefabricated surgical cutting guides-in the setting of facial transplantation-provided us a novel opportunity for digital design and fabrication of a donor mask. The results shown here demonstrate an acceptable appearance for "open-casket" burial while maintaining donor identity after facial organ recovery.

CONCLUSIONS

Several newer techniques for fabrication of facial transplant donor masks exist currently and are described within the article. These encompass digital impression, digital design, and additive manufacturing technology.

Computer-assisted, Le Fort-based, face-jaw-teeth transplantation: a pilot study on system feasiblity and translational assessment

PURPOSE

Le Fort-based face-jaw-teeth transplantation (FJTT) attempts to marry bone and teeth geometry of size-mismatched face-jaw-teeth segments to restore function and form due to severe mid-facial trauma. Recent development of a computer-assisted planning and execution (CAPE) system for Le Fort-based FJTT in a pre-clinical swine model offers preoperative planning, and intraoperative navigation. This paper addresses the translation of the CAPE system to human anatomy and presents accuracy results.

METHODS

Single-jaw, Le Fort-based FJTTs were performed on plastic models, one swine and one human, and on a human cadaver. Preoperative planning defined the goal placement of the donor's Le Fort-based FJTT segment on the recipient. Patient-specific navigated cutting guides helped achieve planned osteotomies. Intraoperative cutting guide and donor fragment placement were compared with postoperative computed tomography (CT) data and the preoperative plan.

RESULTS

Intraoperative measurement error with respect to postoperative CT was less than 1.25 mm for both mock transplants and 3.59 mm for the human cadaver scenario. Donor fragment placement (as compared to the planned position) was less accurate for the human model test case (2.91 mm) compared with the swine test (2.25 mm) and human cadaver (2.26 mm).

CONCLUSION

The results indicate the viability of the CAPE system for assisting with Le Fort-based FJTT and demonstrate the potential in human surgery. This system offers a new path forward to achieving improved outcomes in Le Fort-based FJTT and can be modified to assist with a variety of other surgeries involving the head, neck, face, jaws and teeth.

Establishing cephalometric landmarks for the translational study of Le Fort-based facial transplantation in Swine: enhanced applications using computer-assisted surgery and custom cutting guides

BACKGROUND

Le Fort-based, maxillofacial allotransplantation is a reconstructive alternative gaining clinical acceptance. However, the vast majority of single-jaw transplant recipients demonstrate less-than-ideal skeletal and dental relationships, with suboptimal aesthetic harmony. The purpose of this study was to investigate reproducible cephalometric landmarks in a large-animal model, where refinement of computer-assisted planning, intraoperative navigational guidance, translational bone osteotomies, and comparative surgical techniques could be performed.

METHODS

Cephalometric landmarks that could be translated into the human craniomaxillofacial skeleton, and that would remain reliable following maxillofacial osteotomies with midfacial alloflap inset, were sought on six miniature swine. Le Fort I- and Le Fort III-based alloflaps were harvested in swine with osteotomies, and all alloflaps were either autoreplanted or transplanted. Cephalometric analyses were performed on lateral cephalograms preoperatively and postoperatively. Critical cephalometric data sets were identified with the assistance of surgical planning and virtual prediction software and evaluated for reliability and translational predictability.

RESULTS

Several pertinent landmarks and human analogues were identified, including pronasale, zygion, parietale, gonion, gnathion, lower incisor base, and alveolare. Parietale-pronasale-alveolare and parietale-pronasale-lower incisor base were found to be reliable correlates of sellion-nasion-A point angle and sellion-nasion-B point angle measurements in humans, respectively.

CONCLUSIONS

There is a set of reliable cephalometric landmarks and measurement angles pertinent for use within a translational large-animal model. These craniomaxillofacial landmarks will enable development of novel navigational software technology, improve cutting guide designs, and facilitate exploration of new avenues for investigation and collaboration.

Modeling the biomechanics of swine mastication--an inverse dynamics approach

A novel reconstructive alternative for patients with severe facial structural deformity is Le Fort-based, face-jaw-teeth transplantation (FJTT). To date, however, only ten surgeries have included underlying skeletal and jaw-teeth components, all yielding sub-optimal results and a need for a subsequent revision surgery, due to size mismatch and lack of precise planning. Numerous studies have proven swine to be appropriate candidates for translational studies including pre-operative planning of transplantation. An important aspect of planning FJTT is determining the optimal muscle attachment sites on the recipient's jaw, which requires a clear understanding of mastication and bite mechanics in relation to the new donated upper and/or lower jaw. A segmented CT scan coupled with data taken from literature defined a biomechanical model of mandible and jaw muscles of a swine. The model was driven using tracked motion and external force data of one cycle of chewing published earlier, and predicted the muscle activation patterns as well as temporomandibular joint (TMJ) reaction forces and condylar motions. Two methods, polynomial and min/max optimization, were used for solving the muscle recruitment problem. Similar performances were observed between the two methods. On average, there was a mean absolute error (MAE) of <0.08 between the predicted and measured activation levels of all muscles, and an MAE of <7 N for TMJ reaction forces. Simulated activations qualitatively followed the same patterns as the reference data and there was very good agreement for simulated TMJ forces. The polynomial optimization produced a smoother output, suggesting that it is more suitable for studying such motions. Average MAE for condylar motion was 1.2mm, which reduced to 0.37 mm when the input incisor motion was scaled to reflect the possible size mismatch between the current and original swine models. Results support the hypothesis that the model can be used for planning of facial transplantation.

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.