A new paradigm for complex midface reconstruction: a reversed approach

Digital planning and individual implants for secondary reconstruction of midfacial deformities: A pilot study

Objective

To evaluate the feasibility and accuracy of implementing three‐dimensional virtual surgical planning (VSP) and subsequent transfer by additive manufactured tools in the secondary reconstruction of residual post‐traumatic deformities in the midface.

Methods

Patients after secondary reconstruction of post‐traumatic midfacial deformities were included in this case series. The metrical deviation between the virtually planned and postoperative position of patient‐specific implants (PSI) and bone segments was measured at corresponding reference points. Further information collected included demographic data, post‐traumatic symptoms, and type of transfer tools.

Results

Eight consecutive patients were enrolled in the study. In five patients, VSP with subsequent manufacturing of combined predrilling/osteotomy guides and PSI was performed. In three patients, osteotomy guides, repositioning guides, and individually prebent plates were used following VSP. The median distances between the virtually planned and the postoperative position of the PSI were 2.01 mm (n = 18) compared to a median distance concerning the bone segments of 3.05 mm (n = 12). In patients where PSI were used, the median displacement of the bone segments was lower (n = 7, median 2.77 mm) than in the group with prebent plates (n = 5, 3.28 mm).

Conclusion

This study demonstrated the feasibility of VSP and transfer by additive manufactured tools for the secondary reconstruction of complex residual post‐traumatic deformities in the midface. However, the median deviations observed in this case series were unexpectedly high. The use of navigational systems may further improve the level of accuracy.

To evaluate the feasibility and accuracy of implementing three‐dimensional virtual surgical planning (VSP) and subsequent transfer by additive manufactured tools in the secondary reconstruction of residual post‐traumatic deformities in the midface. This study demonstrated the feasibility of VSP and transfer by additive manufactured tools for the secondary reconstruction of complex residual post‐traumatic deformities in the midface. However, the median deviations observed in this case series were unexpectedly high. The use of navigational systems may further improve the level of accuracy.

Estimating Reference Shape Model for Personalized Surgical Reconstruction of Craniomaxillofacial Defects

OBJECTIVE

To estimate a patient-specific reference bone shape model for a patient with craniomaxillofacial (CMF) defects due to facial trauma.

METHODS

We proposed an automatic facial bone shape estimation framework using pre-traumatic conventional portrait photos and post-traumatic head computed tomography (CT) scans via a 3D face reconstruction and a deformable shape model. Specifically, a three-dimensional (3D) face was first reconstructed from the patient's pre-traumatic portrait photos. Second, a correlation model between the skin and bone surfaces was constructed using a sparse representation based on the CT images of training normal subjects. Third, by feeding the reconstructed 3D face into the correlation model, an initial reference shape model was generated. In addition, we refined the initial estimation by applying non-rigid surface matching between the initially estimated shape and the patient's post-traumatic bone based on the adaptive-focus deformable shape model (AFDSM). Furthermore, a statistical shape model, built from the training normal subjects, was utilized to constrain the deformation process to avoid overfitting.

RESULTS AND CONCLUSION

The proposed method was evaluated using both synthetic and real patient data. Experimental results show that the patient's abnormal facial bony structure can be recovered using our method, and the estimated reference shape model is considered clinically acceptable by an experienced CMF surgeon.

SIGNIFICANCE

The proposed method is more suitable to the complex CMF defects for CMF reconstructive surgical planning.

Is Zygomatic Osteotomy a Viable Option to Achieve Symmetry and Stability in Post-traumatic Residual Deformity of the Zygomaticomaxillary Complex?

PURPOSE

In residual deformity cases, it is difficult to reposition the zygomaticomaxillary-complex (ZMC) intraoperatively, due to resorbed fracture edges, and lack of zygoma analysis to 3-dimensionally quantify the deformity. Instability after zygomatic osteotomy and miniplate fixation (ZOMF) due to the gap between osteotomized segments, scar tissue, muscle pull, and other factors is also unknown. The study aims to evaluate symmetry and stability after ZOMF.

MATERIALS AND METHODS

In this prospective study, a ZMC analysis was designed and patients with unilateral post-traumatic residual deformity (>10 weeks) of ZMC were treated with ZOMF. Measurements were evaluated on affected and unaffected sides at preoperatively, immediately, and 6 months postoperatively using MIMICS software. The primary outcome variable was the symmetry and stability of ZMC. Secondary parameters were changes in orbital volume, diplopia, ocular motility, mouth opening, and patient satisfaction. P < .05 was considered statistically significant. The continuous variables were compared by paired t-test. The change within the continuous variable with time was assessed by repeated measure ANOVA, followed by multiple comparisons using the Bonferroni test. The changes within the categorical variable were assessed by the McNemar test.

RESULTS

Ten patients were enrolled (mean age = 29.2 ± 9.97 years; male:female = 9:1; right:left = 4:6). The mean duration from trauma to surgery was 34.84 ± 31.35 weeks. There was an improvement in the symmetry in anteroposteriorly (P = .005), mediolaterally (P = .001), and at the arch (P = .011) postoperatively. All parameters remained stable at 6 months postoperatively (difference not significant, P > .05); with the median satisfaction score of 4 of 5. Significant improvement in mouth opening (P = .014) and orbital volume (P = .001) was noted.

CONCLUSIONS

Virtual measurements as per the proposed protocol helped in communication and quantifying ZMC. Four-point fixation with miniplates provided enough stability over the 6-month follow-up period.

The accuracy and stability of the maxillary position after orthognathic surgery using a novel computer-aided surgical simulation system

Background

Many reports have been published on orthognathic surgery (OGS) using computer-aided surgical simulation (CASS). The purpose of this study was to evaluate the accuracy of the maxillary repositioning and the stability of the maxilla in patients who underwent OGS using a newly developed CASS program, a customized osteotomy guide, and a customized miniplate.

Methods

Thirteen patients who underwent OGS from 2015 to 2017 were included. All patients underwent a bimaxillary operation. First, a skull-dentition hybrid 3D image was rendered by merging the cone beam computed tomography (CBCT) images with the dentition scan file. After virtual surgery (VS) using the FaceGide® program, patient-customized osteotomy guides and miniplates were then fabricated and used in the actual operation. To compare the VS with the actual surgery and postoperative skeletal changes, each reference point marked on the image was compared before the operation (T0) and three days (T1), four months (T2), and a year (T3) after the operation, and with the VS (Tv). The differences between ΔTv (Tv-T0) and ΔT1 (T1-T0) were statistically compared using tooth-based reference points. The superimposed images of Tv and T1 were also investigated at eight bone-based reference points. The differences between the reference points of the bone surface were examined to evaluate the stability of the miniplate on the maxilla over time.

Results

None of the patients experienced complications. There were no significant differences between the reference points based on the cusp tip between ΔTv and ΔT1 (p > 0.01). Additionally, there were no significant differences between the Tv and T1 values of the bone surface (p > 0.01). The mean difference in the bone surface between Tv and T1 was 1.01 ± 0.3 mm. Regarding the stability of the miniplate, there were no significant differences between the groups. The difference in the bone surface between T1 and T3 was − 0.37 ± 0.29 mm.

Conclusions

VS was performed using the FaceGide® program, and customized materials produced based on the VS were applied in actual OGS. The maxilla was repositioned in almost the same manner as in the VSP plan, and the maxillary position remained stable for a year.

Surgical navigation improves reductions accuracy of unilateral complicated zygomaticomaxillary complex fractures: a randomized controlled trial

Accurate reduction is the key to successful treatment of bone fractures. Complicated zygomaticomaxillary complex fracture, known as one of the most challenging facial bone fractures, is often hard to achieve an accurate reduction, thus leading to facial deformity. In this study, twenty patients with unilateral complicated zygomaticomaxillary complex fractures were included and randomly divided into experimental and control groups, which is with and without the aid of surgical navigation, respectively. The pre- and postoperative imaging data were collected and then analysed using Geomagic Studio 11 software and Brainlab iPlan CMF 3.0. A more precise reduction was showed in the experimental group according to the measurement results of both software programmes than in the control group. In conclusion, surgical navigation showed great value in performing accurate reductions of complicated zygomaticomaxillary complex fractures and restoring facial contour.

Development of a novel anatomical thin titanium mesh plate with reduction guidance and fixation function for Asian zygomatic-orbitomaxillary complex fracture

For this study we developed an anatomical thin titanium mesh (ATTM) plate for Asian zygomaticomaxillary complex (ZMC) fracture repair with reduction guidance and fixation function. The ATTM plate profile was designed as an L-shape to fix at the anterior maxilla and lateral buttress of the ZMC. Computer-aided stamping analysis was performed on four screw-hole patterns in the ATTM plate - a control without screw-holes, square screw-holes, double screw-holes, and large-diameter, double screw-holes - using upper/lower dies of averaged ZMC reconstruction models. A regular ATTM plate of 0.6 mm thickness was manufactured and pre-bent using a patient-matched stamping process to verify its feasibility on three ZMC fracture models with one, two, and three fracture segments. The stamping analysis found that the double screw-holes design resulted in the most favorable performance among all the designs because of maximum von Mises stress (408 MPa) under the ultimate tensile strength. Positioning practice showed that the stamped, pre-bent ATTM plate can be used as a reduction guide to provide precise ZMC segment fixation in a completely passive fashion while limiting redundant rotation/micromovement between the separate bones in all directions. This study concluded that the ATTM plate with double screw-hole pattern design, using a patient-matched, pre-bent technique, can fit the ATTM plate/ZMC interface well, decrease mobility of unstable fracture segments, and provide good original facial contour recovery, while improving reduction efficiency.

Surgical Navigation: A Systematic Review of Indications, Treatments, and Outcomes in Oral and Maxillofacial Surgery

PURPOSE

This systematic review investigates the most common indications, treatments, and outcomes of surgical navigation (SN) published from 2010 to 2015. The evolution of SN and its application in oral and maxillofacial surgery have rapidly developed over recent years, and therapeutic indications are discussed.

MATERIALS AND METHODS

A systematic search in relevant electronic databases, journals, and bibliographies of the included articles was carried out. Clinical studies with 5 or more patients published between 2010 and 2015 were included. Traumatology, orthognathic surgery, cancer and reconstruction surgery, skull-base surgery, and foreign body removal were the areas of interests.

RESULTS

The search generated 13 articles dealing with traumatology; 5, 6, 2, and 0 studies were found that dealt with the topics of orthognathic surgery, cancer and reconstruction surgery, skull-base surgery, and foreign body removal, respectively. The average technical system accuracy and intraoperative precision reported were less than 1 mm and 1 to 2 mm, respectively. In general, SN is reported to be a useful tool for surgical planning, execution, evaluation, and research. The largest numbers of studies and patients were identified in the field of traumatology. Treatment of complex orbital fractures was considerably improved by the use of SN compared with traditionally treated control groups.

CONCLUSIONS

SN seems to be a very promising addition to the surgical toolkit. Planning details of the surgical procedure in a 3-dimensional virtual environment and execution with real-time guidance can significantly improve precision. Among factors to be considered are the financial investments necessary and the learning curve.

Algorithm for planning a double-jaw orthognathic surgery using a computer-aided surgical simulation (CASS) protocol. Part 1: planning sequence

The success of craniomaxillofacial (CMF) surgery depends not only on the surgical techniques, but also on an accurate surgical plan. The adoption of computer-aided surgical simulation (CASS) has created a paradigm shift in surgical planning. However, planning an orthognathic operation using CASS differs fundamentally from planning using traditional methods. With this in mind, the Surgical Planning Laboratory of Houston Methodist Research Institute has developed a CASS protocol designed specifically for orthognathic surgery. The purpose of this article is to present an algorithm using virtual tools for planning a double-jaw orthognathic operation. This paper will serve as an operation manual for surgeons wanting to incorporate CASS into their clinical practice.

Using Free Navigation Reference Points and Prefabricated Bone Plates for Zygoma Fracture Model Surgeries

Surgical navigation systems have been an important tool in maxillofacial surgery, helping surgeons create a presurgical plan, locate lesions, and provide guidance. For secondary facial bone reductions, a good presurgical plan and proper execution are the key to success. Previous studies used predetermined markers and screw holes as navigation references; however, unexpected situations may occur, making the predetermined surgical plan unreliable. Instead of determining positions preoperatively, this study proposes a method that surgeons can use intraoperatively to choose surface markers in a more flexible manner. Eight zygomatic fractures were created in four skull models, and preoperative computed tomography (CT) image data were imported into a self-developed navigation program for presurgical planning. This program also calculates the ideal positions of navigation references points for screw holes. During reduction surgery, markers on fractured bone are selected, registered, and calculated as free navigation reference points (FNRPs). The surface markers and FNRPs are used to monitor the position of the dislocated bone. Titanium bone plates were prefabricated on stereolithography models for osteosynthesis. Two reductions with only FNRPs, as well as six reductions with FNRPs and prefabricated bone plates, were successfully performed. Postoperative CT data were obtained, and surgical errors in the six-reduction group were evaluated. The average deviation from the screw hole drilling positions was 0.92 ± 0.38 mm. The average deviation included displacement and rotation of the zygomas. The mean displacement was 0.83 ± 0.38 mm, and the average rotations around the x, y, and z axes were 0.66 ± 0.59°, 0.77 ± 0.54°, and 0.79 ± 0.42°, respectively. The results show that combining presurgical planning and the developed navigation program to generate FNRPs for assisting in secondary zygoma reduction is an accurate and practical method. Further study is necessary to prove its clinical value.

A new design of CAD/CAM surgical template system for two-piece narrowing genioplasty

The purpose of this study was to develop and validate a new chin template system for a two-piece narrowing genioplasty. Nine patients with wide chin deformities were enrolled. Surgeries were planned with the computer-aided surgical simulation (CASS) planning method. Surgical splints and chin templates were designed in a computer and fabricated using a three-dimensional printing technique. The chin template system included a cutting guide and a repositioning guide for a two-piece narrowing genioplasty. These guides were also designed to avoid the mental foramen area and inferior alveolar nerve loops during the osteotomy, for nerve protection. After surgery, the outcome evaluation was completed by first superimposing the postoperative computed tomography model onto the planned model, and then measuring the differences between the planned and actual outcomes. All surgeries were completed successfully using the chin template system. No inferior alveolar nerve damage was seen in this study. With the use of the chin templates, the largest linear root mean square deviation (RMSD) between the planned and the postoperative chin segments was 0.7mm and the largest angular RMSD was 4.5°. The results showed that the chin template system provides a reliable method of transfer for two-piece osseous narrowing genioplasty planning.

An eFace-Template Method for Efficiently Generating Patient-Specific Anatomically-Detailed Facial Soft Tissue FE Models for Craniomaxillofacial Surgery Simulation

Accurate surgical planning and prediction of craniomaxillofacial surgery outcome requires simulation of soft-tissue changes following osteotomy. This can only be accomplished on an anatomically-detailed facial soft tissue model. However, current anatomically-detailed facial soft tissue model generation is not appropriate for clinical applications due to the time intensive nature of manual segmentation and volumetric mesh generation. This paper presents a novel semi-automatic approach, named eFace-template method, for efficiently and accurately generating a patient-specific facial soft tissue model. Our novel approach is based on the volumetric deformation of an anatomically-detailed template to be fitted to the shape of each individual patient. The adaptation of the template is achieved by using a hybrid landmark-based morphing and dense surface fitting approach followed by a thin-plate spline interpolation. This methodology was validated using 4 visible human datasets (regarded as gold standards) and 30 patient models. The results indicated that our approach can accurately preserve the internal anatomical correspondence (i.e., muscles) for finite element modeling. Additionally, our hybrid approach was able to achieve an optimal balance among the patient shape fitting accuracy, anatomical correspondence and mesh quality. Furthermore, the statistical analysis showed that our hybrid approach was superior to two previously published methods: mesh-matching and landmark-based transformation. Ultimately, our eFace-template method can be directly and effectively used clinically to simulate the facial soft tissue changes in the clinical application.

Development of customized positioning guides using computer-aided design and manufacturing technology for orthognathic surgery

PURPOSE

The purpose of this study was to devise a method for producing customized positioning guides for translating virtual plans to actual orthognathic surgery, and evaluation of the feasibility and validity of the devised method.

METHODS

Patients requiring two-jaw orthognathic surgery were enrolled and consented before operation. Two types of positioning guides were designed and fabricated using computer-aided design and manufacturing technology: One of the guides was used for the LeFort I osteotomy, and the other guide was used for positioning the maxillomandibular complex. The guides were fixed to the medial side of maxilla. For validation, the simulation images and postoperative cone beam computed tomography images were superimposed using surface registration to quantify the difference between the images. The data were presented in root-mean-square difference (RMSD) values.

RESULTS

Both sets of guides were experienced to provide ideal fit and maximal contact to the maxillary surface to facilitate their accurate management in clinical applications. The validation results indicated that RMSD values between the images ranged from 0.18 to 0.33 mm in the maxilla and from 0.99 to 1.56 mm in the mandible. The patients were followed up for 6 months or more, and all of them were satisfied with the results.

CONCLUSION

The proposed customized positioning guides are practical and reliable for translation of virtual plans to actual surgery. Furthermore, these guides improved the efficiency and outcome of surgery. This approach is uncomplicated in design, cost-effective in fabrication, and particularly convenient to use.

Digital design and individually fabricated titanium implants for the reconstruction of traumatic zygomatico-orbital defects

Autogenous bone graft is the preferred method for the reconstruction of maxillofacial defects. As an additional choice, the aim of this study was to develop and test the application of individual digital planning, rapid prototyping titanium implants, and functional long-term results in the reconstruction of traumatic zygomatico-orbital defects. Six patients were treated with 3-dimensional digital surgery designs, digital locating template, and individually fabricated titanium implants. All patients were followed for a minimum of 18 months with a mean of 51.8 months. The recovery of facial contour and function was satisfactory in 4 patients. In the other 2 patients, 1 implant was removed after implant exposure caused by infection, and the other implant was removed because of persistent diplopia. Although the risk of implant exposure exists, individual digital planning procedures, rapid prototyping, digital locating templates, and titanium implants are still effective methods for reconstructing traumatic zygomatico-orbital defects. We believe that the appropriate choice of surgical cases is of great importance when using individually designed titanium implants to restore maxillofacial defects. The patient's age, health, medical history, local infection, location and extent of the bony defect, and remaining soft tissue volume should all be taken into consideration.

Outcome study of computer-aided surgical simulation in the treatment of patients with craniomaxillofacial deformities

PURPOSE

The purpose of this study was to determine whether the surgical outcomes achieved with computer-aided surgical simulation (CASS) are better than those achieved with traditional methods.

MATERIALS AND METHODS

Twelve consecutive patients with craniomaxillofacial (CMF) deformities were enrolled. According to the CASS clinical protocol, a 3-dimensional computer composite skull model for each patient was generated and reoriented to the neutral head posture. These models underwent 2 virtual surgeries: 1 was based on CASS (experimental group) and the other was based on traditional methods 1 year later (control group). Once the 2 virtual surgeries were completed, 2 experienced oral and maxillofacial surgeons at 2 different settings evaluated the 2 surgical outcomes. They were blinded to the planning method used on the virtual models and each other's evaluation results. The primary outcome was overall CMF skeletal harmony. The secondary outcomes were individual maxillary, mandibular, and chin harmonies. Statistical analyses were performed.

RESULTS

Overall CMF skeletal harmony achieved with CASS was statistically significantly better than that achieved with traditional methods. In addition, the maxillary and mandibular surgical outcomes achieved with CASS were significantly better. Furthermore, although not included in the statistical model, the chin symmetry achieved by CASS tended to be better. A regression model was established between mandibular symmetry and overall CMF skeletal harmony.

CONCLUSION

The surgical outcomes achieved with CASS are significantly better than those achieved with traditional planning methods. In addition, CASS enables the surgeon to better correct maxillary yaw deformity, better place proximal/distal segments, and better restore mandibular symmetry. The critical step in achieving better overall CMF skeletal harmony is to restore mandibular symmetry.

Reoperative mandibular trauma: management of posttraumatic mandibular deformities

Mandibular fractures are one the most common maxillofacial injuries. Diagnostic errors, poor surgical technique, healing disorders, or complications may lead to the establishment of posttraumatic mandibular deformities. Nonunion, malunion/malocclusion, or facial asymmetry can be found early during the healing process or as long-term sequelae after the initial mandibular fracture repair. Although occasionally these problems can be solved in a nonsurgical manner, reoperations play an important role in the management of these untoward outcomes. This article discusses the reoperative techniques used for the management of these deformities.