Application Of Three-Dimensional Printing Technique In Surgical Treatment Of Sinonasal Malignancies

Background:Nasal sinuses are located in maxillofacial region,adjoining important structures such as skull base,brain and orbit.They have anatomical features of complicated structures and profuse neurovascular supply,and are closely related to physical functions including respiration,mastication,deglutition and phonation.Sinonasal malignancies are common tumors of the head and neck,accounting for 1% of all malignancies and 5% of head and neck malignancies.Patients often present with atypical unilateral symptoms which are similar to those of inflammatory diseases.The early diagnosis of sinonasal malignancy is usually difficult until presentation of typical clinical symptoms indicating involvement of nearby structures such as the brain,orbit,or cranial nerves.Treatment is based on multimodality therapy,primarily surgical excision.Maxillofacial tissue defects after radical resection of sinonasal malignancy will result in severe facial deformity and functional disorders,and therefore seriously affect the psychological health and quality of life of patients.From the perspective of bio-psycho-social medical model,radical resection of sinonasal malignancy should follow the principle of preservation of the vital structures such as eye if possible on premise of complete resection of malignant lesions.Meanwhile,structural repair and functional reconstruction should be critically considered.As a whole,accurate preoperative evaluation,proper choice of surgical procedures with preservation of the vital structures,and repair of structural defects are keys to successful surgical treatment of sinonasal malignancies.Imageological examinations are very important for the precise identification of primary site,tumor size and invaded extension in sinonasal malignancy.X radiography has been eliminated due to its limitations.Magnetic resonance imaging(MRI)can not only observe the invasion of soft tissues such as optic nerve and brain,but also identify early signal changes in neighbor fat tissue out of walls.MIR plays an important role in the differential diagnosis of sinonasal malignancy.With advantages of high sensitivity and specificity,computed tomography(CT)has become a routine imageological examinationmethod for sinonasal malignancy.The tumor presents as solid lesions of unilateral nose or one-sinus-centered.CT can also find bone erosion,soft tissue mass outside the sinus and changes of neighbor fat spaces.With the daily improvement of multi-slice computed tomography and widespread application of computer image processing technology in the medical imageology,three dimensional reconstruction of medial image has been carried out,which facilitated the establishment of three-dimensional model and quantitative measurements of anatomic structures.Three-dimensional(3D)printing technology is also referred to as rapid prototyping method.The philosophy of this technology is to create three-dimensional object by depositing successive layers of material in layer-by-layer manner(also called additive manufacturing,AM).In biomedical field,recent advances in AM technology,computed tomographic reconstruction,and numerical modeling methods have allowed surgeons to properly select reasonable operation scheme via acquiring a deeper understanding and more detailed knowledge of focus and nearby structures.This technology has brought virtual surgery simulation to reality.Simulated surgical operations such as excision of lesions,implantation and retention of repair material can be performed on the three-dimensional model,which contributed to increasing surgical precision and minimal invasion,accuracy of implantation and avoidance of postoperative displacement of implants.For the difficult cases,surgeons can design and improve their operationschemesvia simulated operations.The manufacture of individual repair materials which perfectlymatch human body anatomic structures can effectively shorten time ofoperationand satisfactorily meet requirements of individual defect repair.Maxillary malignancies are the most common tumors of the sinuses,accounting for60%~80% of sinonasal malignancies,and accompany malignancies of ethmoidal sinus in one third of these patients.Radical operation of maxillary malignancy usually incision of maxilla and orbital walls which results in defects of maxilla,medial wall and floor of orbit.These defects may cause maxillofacial malformation andseriouslyimpactfunctionsof optesthesia,mastication,phonation,deglutition and respiration.Therefore,defect repairand reconstruction of maxillofacial bone and orbital walls is essential for deformity correction and function restoration in maxillary malignancy patients receiving radical operations.Objectives:This study aims to acquire anatomic parameters related to total resection of maxillarybone and defect repair and reconstruction via three-dimensional reconstruction of maxillarysinus and nearby structures,establishment and printing of three-dimensional model,therefore to provide anatomic basis and technical support for defects repair of bone scaffold after radical operation of maxillary malignancy with 3D printing technology.The study also aims to explore effectiveness and safety of 3D printing technology via its clinical applications in repair and reconstruction of defects of maxillofacial bone and orbital walls.Methods:1.Reconstruction of three-dimensional image of maxillary sinus,establishment and printing of three-dimensional model of maxillary sinus.Multi-slice spiral CT scans were performed to 11 patients suffering from sinonasal malignancies.All the patients had no history of previous sinonasal surgery.Canthomeatal line as baseline,CT scan was performed with scanning scope of full head and scanning thickness of 0.75 mm.The imagine data were saved to compact disc in DICOM format.The software Mimics 15.0 was used to read,convert and direct the original data.Maxillary sinus and surrounding structures were segmented,masks were generated with final establishment of three-dimensional model of maxillary sinus.On the models,anatomic parameters related to radical incision of maxillary sinus and defect repair and reconstruction of maxillofacial bone and orbital walls were quantitatively measured.The data were processed and transmitted to a three-dimensional printer to create a resin three-dimensional model of maxillary sinus.Using unaffected maxillary sinus as a template,the affected maxillary sinus was remodeled with software Geomagic Studio 12.0,mirroring technology and reverse engineering.The remodeled model was compared with the original.Resection of maxillawas simulated on the resin three-dimensionalmodel to design individual operative scheme.Repair material was printed and prefabricatedaccording to the simulated operation.2.Application of three-dimensional printing technology in maxillofacial bone defect repair and reconstruction after maxillectomy in sinonasal malignanciesFive patients suffering from malignant tumors of maxillary sinus received total maxillectomy were included.Before operation,a three-dimensional individual stereo-maxillary model based on mirror images of the unaffected maxilla was obtained to fabricate an anatomically adapted titanium mesh using computer-assisted design and manufacturing.The individual titanium mesh was inserted into the maxillary after total maxillectomy.Facial appearance and function were evaluated by clinical and CT examinations.3.Application of three-dimensional printing technology in orbital wall defect repair and reconstruction after maxillectomy in sinonasal malignanciesSixpatients suffering from malignant tumors of maxillary sinus with destruction of orbital walls and received total maxillectomy were included.Before operation,computed tomography(CT)was performed to all patients.A resin stereo model of the affected orbital wall was printed with three-dimentional printing technique.A titanium mesh was modeled based on the resin model,and the preformed titanium mesh was then implanted into the defect area of orbital wall for reconstruction.For assessing recovery of orbital walls,orbital volumes and globe projections were evaluated by clinical and CT examinations.Results:1.Three-dimensional images maxillary sinus and surrounding structures were successfully reconstructed and the models were printed.The anatomic parameters were obtained from quantitative measurements.Data of images were consistent with those of models.Using unaffected maxillary sinus as a template,the remodeled model of the affected maxillary sinus was established with mirroring technology and reverse engineering.The remodeled model was highly consistent with the original.Repairmaterialswere printed and prefabricated based on the simulated operation.2.All patients were satisfied with their postoperative facial symmetry and did not develop diplopia or endophthalmos.During the operation procedure,the pre-bent titanium mesh did not require reshaping and pruning.The implanted titanium mesh fit bone bed surrounding the defect closely.Clinical and CT examinations showed recurrence in none during the follow-up of 12 to 36 months.3.All the 6 cases came through the operation successfully.During operation,the preformed titanium mesh did not require reshaping and pruning.The implanted titanium mesh fit bone bed surrounding the defect closely.Clinical examinations and CT scan3 months after surgery showed successful reconstruction of orbital wall in all cases without serious complications.All the patients were followed up for 12 to 36 monthspostoperatively,and no recurrence occurred.Enophthalmos was corrected back to less than 3mm.No clinical enophthalmos could be observed in all the patients.Singlequadrant diplopia occurred in one patient.The differences of orbital volumes,globe projections betweenthe affected andunaffected orbits were both statistically insignificant(both P>0.05).Conclusions:1.The three-dimensional images and models can offer unparalleled stereoscopic glimpses of maxillary sinus and surrounding structures.Anatomic data obtained from quantitative measurements of individual model are available for delineation of tumor extent,decision of surgical plans,print and prefabrication of repair materials via simulated surgical procedures.2.With good feasibility and reliability,3-dimensional printing technique is suitable for the surgical treatment of maxillary sinus malignant tumors,and can significantly improve the clinical outcome.With exactly reconstruction of anatomic shape and orbital volumes,three-dimensional preformed titanium mesh is suitable for repair of surgical defects of maxillofacial bone and orbital walls in sinus malignant tumors.3.In conclusion,applications of three-dimensional reconstruction and printing inthe surgical treatment of sinonasal malignancies can effectively shorten operation time,significantlyreduce surgical complications,perfectly reconstruct bone scaffold,and restore the physiological function.These techniques are conducive to sophisticated preoperative design,accurate intraoperative control and adjustment as well as reliable prognosis,are therefore worth to be applied in clinical.