Using 3D computer planning for complex reconstruction of mandibular defects

The Role of Imaging in Mandibular Reconstruction with Microvascular Surgery

Imaging plays a critical role in the diagnosis, staging, and management of segmental mandibular defects. Imaging allows mandibular defects to be classified which aids in microvascular free flap reconstruction. This review serves to complement the surgeon's clinical experience with image-based examples of mandibular pathology, defect classification systems, reconstruction options, treatment complications, and Virtual Surgical Planning.

Practice patterns of virtual surgical planning: Survey of the reconstructive section of the American Head and Neck Society

PURPOSE

Virtual surgical planning (VSP), with custom made implants and guides represents a recent major advance. Nonetheless, knowledge related to practice patterns is limited. The purpose of this study was to provide data from the AHNS Reconstruction Section related to practice patterns, perceived value of VSP, as well as elucidate specific situations which represent high value for the application of VSP.

MATERIALS AND METHODS

A multi-center web-based survey consisting of 30 questions regarding practice patterns related to VSP practices delivered via email to 203 members of the AHNS Reconstructive Surgery Section at institutions across North America.

RESULTS

There was a 34% response rate (70/203). A majority of the respondents (96%) used VSP in approximately 50% of their mandibular reconstruction cases, and in 42% of maxillary cases. 46% reported using patient specific implants >75% of cases. Respondents estimated that ~17% of patients received dental implant reconstruction. The majority of respondents (71.0%) did not know the cost of VSP at their institution. The remaining respondents indicated the average cost was $6680 per case. VSP was felt to be necessary as a teaching tool by 55.9%.

CONCLUSIONS

Our results demonstrate that a majority of respondents frequently utilize VSP in their practice for head and neck reconstruction. Complex, multi-unit reconstructions were felt to offer the greatest value when utilizing VSP. Future work should focus on increasing the rates of dental implant reconstruction in this population, optimizing value of VSP with careful case selection, and understanding the educational value and costs of these platforms.

Procedure Increasing the Accuracy of Modelling and the Manufacturing of Surgical Templates with the Use of 3D Printing Techniques, Applied in Planning the Procedures of Reconstruction of the Mandible

The application of anatomical models and surgical templates in maxillofacial surgery allows, among other benefits, the increase of precision and the shortening of the operation time. Insufficiently precise anastomosis of the broken parts of the mandible may adversely affect the functioning of this organ. Applying the modern mechanical engineering methods, including computer-aided design methods (CAD), reverse engineering (RE), and rapid prototyping (RP), a procedure used to shorten the data processing time and increase the accuracy of modelling anatomical structures and the surgical templates with the use of 3D printing techniques was developed. The basis for developing and testing this procedure was the medical imaging data DICOM of patients treated at the Maxillofacial Surgery Clinic of the Fryderyk Chopin Provincial Clinical Hospital in Rzeszów. The patients were operated on because of malignant tumours of the floor of the oral cavity and the necrosis of the mandibular corpus, requiring an extensive resection of the soft tissues and resection of the mandible. Familiarity with and the implementation of the developed procedure allowed doctors to plan the operation precisely and prepare the surgical templates and tools in terms of the expected accuracy of the procedures. The models obtained based on this procedure shortened the operation time and increased the accuracy of performance, which accelerated the patient’s rehabilitation in the further course of events.

3D-printed PEEK implant for mandibular defects repair - a new method

Functional reconstruction of large-size mandibular continuity defect is still a major challenge in the oral and maxillofacial surgery due to the unsatisfactory repair effects and various complications. This study aimed to develop a new functional repair method for mandibular defects combined with 3D-printed polyetheretherketone (PEEK) implant and the free vascularized fibula graft, and evaluated the service performance of the implant under whole masticatory motion. The design criteria and workflows of the mandibular reconstruction were established based on the requirements of safety, functionality, and shape consistency. Both the biomechanical behavior and the mechanobiological property of mandibular reconstruction under various masticatory motion were investigated by the finite element analysis. The maximum von Mises stress of each component was lower than the yield strength of the corresponding material and the safety factor was more than 2.3 times, which indicated the security of the repair method can be guaranteed. Moreover, the actual deformation of the reconstruction model was lower than that of the normal mandible under most clenching tasks, which assured the primary stability. More than 80% of the volume elements in the bone graft can obtain effective mechanical stimulation, which benefited to reduce the risks of bone resorption. Finally, the novel repair method was applied in clinic and good clinical performances have been achieved. Compared with the conventional fibular bone graft for surgical mandibular reconstruction, this study provides excellent safety and stability to accomplish the functional reconstruction and aesthetic restoration of the mandible defect.

Patient-Specific Surgical Implant Using Cavity-Filled Approach for Precise and Functional Mandible Reconstruction

Mandibular reconstruction is a complicated task because of the complex nature of the regional anatomy. Computer-assisted tools are a promising means of improving the precision and safety of such complex surgeries. The digital techniques utilized in the reconstruction of mandibular defects based on medical data, computer-aided-design approaches, and three-dimensional (3D) printing are widely used to improve the patient’s aesthetic appearance and function, as well as the accuracy and quality of diagnosis, and surgical outcomes. Nevertheless, to ensure an acceptable aesthetical appearance and functional outcomes, the design must be based on proper anatomical reconstruction, mostly done in a virtual environment by skilled design engineers. Mirroring is one of the widely used techniques in the surgical navigation and reconstruction of mandibular defects. However, there are some discrepancies and mismatches in the mirrored anatomical models. Hence, in order to overcome these limitations in the mirroring technique, a novel approach called the cavity-filled technique was introduced. The objective of this study was to compare the accuracy of the newly recommended cavity-filled technique with the widely used mirror reconstruction technique in restoring mandibular defects. A prominent 3D comparison technique was employed in this work, where the resected and the reconstructed mandibles were superimposed to quantify the accuracy of the two techniques. From the analysis, it can be inferred that the cavity-filled technique with a root-mean-square value of 1.1019 mm produced better accuracy in contrast to the mirroring approach, which resulted in an error of 1.2683 mm. Consequently, by using the proposed cavity-filled design, the discrepancy between the reconstruction plate and the bone contour was mitigated. This method, owing to its high precision, can decrease the number of adjustments and the time of surgery, as well as ensure a quick recovery time with better implant tissue in-growth.

Assessment of the Learning Curve for Virtual Surgical Planning in Orbital Fractures

Virtual surgical planning (VSP) is becoming more widely used in maxillofacial reconstruction and can be surgeon-based or industry-based. Surgeon-based models require software training but allow surgeon autonomy. We evaluate the learning curve for VSP through a prospective cohort study in which planning times and accuracy of 7 otolaryngology residents with no prior VSP experience were compared to that of a proficient user after a single training protocol and 6 planning sessions for orbital fractures. The average planning time for the first session was 21 minutes 41 seconds ± 6 minutes 11 seconds with an average maximum deviation of 2.5 ± 0.8 mm in the lateral orbit and 2.3 ± 0.6 mm in the superior orbit. The average planning time for the last session was 13 minutes 5 seconds ± 10 minutes and 7 seconds with an average maximum deviation of 1.4 ± 0.5 mm in the lateral orbit and 1.3 ± 0.4 mm in the superior orbit. Novice users reduced planning time by 40% and decreased maximum deviation of plans by 44% and 43% in the lateral and superior orbits, respectively, approaching that of the proficient user. Virtual surgical planning has a quick learning curve and may be incorporated into surgical training.

Predictive factors for prolonged operative time in head and neck patients undergoing free flap reconstruction

PURPOSE

Defining the predictive factors associated with prolonged operative time may reduce post-operative complications, improve patient outcomes, and decrease cost of care. The aims of this study are to 1) analyze risk factors associated with prolonged operative time in head and neck free flap patients and 2) determine the impact of lengthier operative time on surgical outcomes.

METHODS

This retrospective cohort study evaluated 282 head and neck free flap reconstruction patients between 2011 and 2013 at a tertiary care center. Perioperative factors investigated by multivariate analyses included gender, age, American Society of Anesthesiologists class, tumor subsite, stage, flap type, preoperative comorbidities, and perioperative hematocrit nadir. Association was explored between operative times and complications including flap take back, flap survival, transfusion requirement, flap site hematoma, and surgical site infection.

RESULTS

Mean operative time was 418.2 ± 88.4 (185-670) minutes. Multivariate analyses identified that ASA class III (beta coefficient + 24.5, p = .043), stage IV tumors (+34.8, p = .013), fibular free flaps (-44.8, p = .033 for RFFF vs. FFF and - 67.7, p = .023 for ALT vs FFF) and COPD (+36.0, p = .041) were associated with prolonged operative time. History of CAD (-43.5, p = .010) was associated with shorter operative time. There was no statistically significant association between longer operative time and adverse flap outcomes or complications.

CONCLUSION

As expected, patients who were medically complex, had advanced cancer, or underwent complex flap reconstruction had longer operative times. Surgical planning should pay special attention to certain co-morbidities such as COPD, and explore innovative ways to minimize operative time. Future research is needed to evaluate how these factors can help guide planning algorithms for head and neck patients.

Assessing the Role of Virtual Surgical Planning in Mandibular Reconstruction With Free Fibula Osteocutaneous Graft

BACKGROUND

The role of virtual surgical planning and three-dimensional printing in improving the accuracy, precision, functional and aesthetic outcomes have been demonstrated in the literature; however, there is a dearth of studies evaluating these parameters.

OBJECTIVE

This study was carried out at a tertiary care center in North India to assess the accuracy of virtual surgical planning in mandibular reconstruction.

METHOD

All the included patients were preoperatively assessed with a contrast enhanced computed tomography (CECT) of head and neck. Based on the dimensions a patient-specific fibula cutting guide was fabricated by three-dimensional printing. All patients were evaluated with a postoperative CECT at 6 months of follow-up. The precision outcomes were measured by comparing surgical results with the images of the preoperative virtual planning based on several measurements on the reconstructed mandible such as anteroposterior measurement, transverse measurement, height of the mandible, angle of the mandible, and lateral tilt.The secondary outcomes analyzed were the mean total operative time, mean ischemia time, and morbidity parameters.

RESULT

Twelve consecutive patients (6 male, 6 female) with mean age of 33.1 ± 11 years who underwent free fibula graft mandibular reconstruction were included in the study. The mean difference in the anteroposterior, transverse, and height dimensions were 0.87 ± 0.43 mm (P = 0.24), 2.43 ± 3.72 mm (P = 0.64), and 1.08 ± 0.67 (P = 0.88), respectively. The difference in the angles of the reconstructed mandible was 2.37 ± 3.92 degrees (P = 0.51) and of lateral tilt was 1.57 ± 1.5 degrees (P = 0.54). The mean total operative time was 639 ± 27.2 minutes and mean ischemia time was 88.4 ± 8.6 minutes.

CONCLUSION

All the patients had satisfactory aesthetic results and good oral function at 6 months postoperative period.