Gabriel F. Santiago

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

IntroductionFacial 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. MethodsWe 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. ResultsPlastic 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. ConclusionsThe 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.

Soft tissue injury management with a continuous external tissue expander

BackgroundBlast exposure is a common cause of soft tissue injury within the battlefield setting, with the extremities often critically involved. The resulting injury pattern presents with massive soft tissue defects that may be further complicated by varying degrees of accompanying orthopedic and peripheral nerve damage. To address the severe soft tissue defect, various combinations of advanced reconstructive methods are typically required to achieve definitive wound coverage. Continuous external tissue expansion has been used by our institution to significantly reduce wound burden and provide for definitive wound closure in certain blast-injured patients. MethodsThe authors present an early series of 14 patients who suffered massive extremity soft tissue injuries and were treated with an external tissue expansion system (DermaClose RC). Outcome measurements included time to definitive closure and method of definitive wound closure. A 5-patient subset of this group was prospectively analyzed to determine measurements including initial wound surface area (WSA), percentage reduction in WSA, and related complications. ResultsOverall time to wound coverage ranged from 1 to 6 days, with mean time to wound coverage being 4.4 days. Of the 14 patients included in the series, 12 (85.7%) were able to undergo delayed primary closure, whereas 2 required split thickness skin grafting. In the 5-patient subgroup, WSA initially ranged from 20.25 to 1031.25 cm2. Mean wound size was 262.7 cm2. Decrease in WSA ranged from 44% to 93% of the initial WSA, with mean decrease being 74.3% (95% confidence interval, 57.33–91.3). ConclusionsIn the management of large complex wounds, external tissue expansion has proven to be a valuable adjunct in achieving definitive wound closure. It can often aid in successful delayed primary closure of certain soft tissue wounds, has low associated morbidities, and can reduce the need for more complex or morbid procedures when used properly. The authors propose an algorithm for the use of continuous external tissue expansion system to achieve effective and successful wound closure, while potentially reducing the need for increased donor-site morbidities associated with more complex or larger reconstruction measures.

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

BackgroundSex-specific anthropometrics, skin texture/adnexae mismatch, and social apprehension have prevented cross-gender facial transplantation from evolving. However, the scarce donor pool and extreme waitlist times are currently suboptimal. Our objective was to (1) perform and assess cadaveric facial transplantation for each sex-mismatched scenario using virtual planning with cutting guide fabrication and (2) review the advantages/disadvantages of cross-gender facial transplantation. MethodsCross-gender facial transplantation feasibility was evaluated through 2 mock, double-jaw, Le Fort–based cadaveric allotransplants, including female donor-to-male recipient and male donor-to-female recipient. Hybrid facial-skeletal relationships were investigated using cephalometric measurements, including sellion-nasion-A point and sellion-nasion-B point angles, and lower-anterior-facial-height to total-anterior-facial-height ratio. Donor and recipient cutting guides were designed with virtual planning based on our team’s experience in swine dissections and used to optimize the results. ResultsSkeletal proportions and facial-aesthetic harmony of the transplants (n = 2) were found to be equivalent to all reported experimental/clinical sex-matched cases by using custom guides and Mimics technology. Cephalometric measurements relative to Eastman Normal Values are shown. ConclusionsOn the basis of our results, we believe that cross-gender facial transplantation can offer equivalent, anatomical skeletal outcomes to those of sex-matched pairs using preoperative planning and custom guides for execution. Lack of literature discussion of cross-gender facial transplantation highlights the general stigmata encompassing the subject. We hypothesize that concerns over sex-specific anthropometrics, skin texture/adnexae disparity, and increased immunological resistance have prevented full acceptance thus far. Advantages include an increased donor pool with expedited reconstruction, as well as size-matched donors.

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.

IntroductionCurrent 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. MethodsDuring 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. ResultsThe 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. ConclusionsSeveral 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.

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.

Algorithmic Approach to Overcome Scalp Deficiency in the Setting of Secondary Cranial Reconstruction

Background:Multidisciplinary approaches have shown improved outcomes in secondary cranial reconstruction, however, scalp deficiency remains a common obstacle for tension-free scalp closure during cranioplasty. Therefore, our objective was to create an algorithmic approach using a novel concept of “component separation” to help minimize potential complications. Methods:The authors tested the hypothesis of achieving greater scalp mobility by way of “component separation” in a half-scalp, bilateral cadaver study, and describe within 2 clinical examples. Pterional-sized (N = 2) and hemicraniectomy-sized (N = 2) scalp flaps were dissected on 2 cadaveric heads using an internal control for each scenario. All flaps (N = 4) were created with (experimental group) and without (control group) “retaining ligament release.” Total amounts of scalp mobility were measured bilaterally and compared accordingly. Results:Scalp flap mobility was calculated from the sagittal midline using identical arcs of rotation. With zero tension, we observed an increased distance of movement equaling 1 cm for the “experimental” pterional flap, compared with the contralateral “control.” Similarly, we found an increase of additional 2 cm in scalp mobility for the “experimental” hemicraniectomy-sized flap. Conclusions:Tension free scalp closure is most critical for achieving improved outcomes in secondary cranial reconstruction. In this study, we show that a range of 1 to 2 additional centimeters may be gained through a component separation, which is of critical value during scalp closure following cranioplasty. Therefore, based on our high volume cranioplasty experience and cadaver study presented, we offer some new insight on methods to overcome scalp deficiency accompanying secondary cranial reconstruction.

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.

Comparative Cost Analysis of Single and Mutli-Stage Temporal Deformity Correction Following Neurosurgical Procedures

Purpose: Temporal hollowing deformity (THD) is a visible concavity/convexity in the temporal fossa; a complication often seen following neurosurgical/craniofacial procedures. Although numerous techniques have been described, no study to date has shown the healthcare costs associated with temporal hollowing correction surgery. Thus, the purpose here is to compare and contrast the direct costs related to temporal cranioplasty using various methods including: liquid poly-methyl-methacrylate (PMMA) implants with screw fixation, prebent, modified titanium mesh implants, and customized cranial implants (CCIs) with dual-purpose design. Understanding the financial implications related to this frequently encountered complication will help to motivate surgeons/healthcare facilities to better prevent and manage THD. Methods: This is a single-surgeon, single-institution retrospective review of 23 THD patients randomly selected from between 2008 and 2015. Cost analysis variables include length of hospital stay, facility/professional fees, implant material fees, payer information, reimbursement rate, and net revenue. Results: Of the 23 patients, ages ranged from 23 to 68 years with a mean of 48.3 years (SD 11.6). Within this cohort, 39.1% received dual-purpose PMMA CCIs (CCI PLUS), 17.4% received modified titanium mesh implants, and 43.5% received hand-molded, liquid PMMA implants with screw fixation. Total facility and/or professional charges ranged from

Abstract P30: Complex Surgical Cutting Guides for Le Fort-Based, Maxillofacial Transplantation Developed through Preclinical, Orthotopic Swine Transplants and Human Cadaver Surgeries

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