David L. Hirsch

Accuracy of a computer-aided surgical simulation protocol for orthognathic surgery: A prospective multicenter study

PURPOSE The purpose of this prospective multicenter study was to assess the accuracy of a computer-aided surgical simulation (CASS) protocol for orthognathic surgery. MATERIALS AND METHODS The accuracy of the CASS protocol was assessed by comparing planned outcomes with postoperative outcomes of 65 consecutive patients enrolled from 3 centers. Computer-generated surgical splints were used for all patients. For the genioplasty, 1 center used computer-generated chin templates to reposition the chin segment only for patients with asymmetry. Standard intraoperative measurements were used without the chin templates for the remaining patients. The primary outcome measurements were the linear and angular differences for the maxilla, mandible, and chin when the planned and postoperative models were registered at the cranium. The secondary outcome measurements were the maxillary dental midline difference between the planned and postoperative positions and the linear and angular differences of the chin segment between the groups with and without the use of the template. The latter were measured when the planned and postoperative models were registered at the mandibular body. Statistical analyses were performed, and the accuracy was reported using root mean square deviation (RMSD) and the Bland-Altman method for assessing measurement agreement. RESULTS In the primary outcome measurements, there was no statistically significant difference among the 3 centers for the maxilla and mandible. The largest RMSDs were 1.0 mm and 1.5° for the maxilla and 1.1 mm and 1.8° for the mandible. For the chin, there was a statistically significant difference between the groups with and without the use of the chin template. The chin template group showed excellent accuracy, with the largest positional RMSD of 1.0 mm and the largest orientation RMSD of 2.2°. However, larger variances were observed in the group not using the chin template. This was significant in the anteroposterior and superoinferior directions and the in pitch and yaw orientations. In the secondary outcome measurements, the RMSD of the maxillary dental midline positions was 0.9 mm. When registered at the body of the mandible, the linear and angular differences of the chin segment between the groups with and without the use of the chin template were consistent with the results found in the primary outcome measurements. CONCLUSIONS Using this computer-aided surgical simulation protocol, the computerized plan can be transferred accurately and consistently to the patient to position the maxilla and mandible at the time of surgery. The computer-generated chin template provides greater accuracy in repositioning the chin segment than the intraoperative measurements.

Computer-aided design and manufacturing in craniomaxillofacial surgery: the new state of the art.

Abstract The goal of this article was to illustrate the ease in which virtual surgery and computer-aided design and manufacturing can be used by the craniomaxillofacial surgeon to create tremendously accurate postoperative results and provide confidence with even the most complex three-dimensional bony reconstructions. With advancements in software technology and three-dimensional printing, our ability to plan and execute precise bony reconstruction has become a reality. With this technology, guides can be made to ensure exact bony repositioning or replacement. These guides can help guide cutting of the bone and can act as splints to precisely reposition the bone and direct plate placement. With use of these computer-aided design and manufacturing guides and the addition of guidance technology, the position of the bone can be guaranteed intraoperatively. We review our unique and advanced method in approaching some of these problems and illustrate the application of these techniques in mandibular reconstruction, orthognathic surgery, maxillofacial trauma, and temporomandibular joint reconstruction. This technology continues to evolve, and our indications for its application continue to grow. This article represents only a small portion of the types of cases in which these techniques have already been applied.

Jaw in a day: total maxillofacial reconstruction using digital technology.

Background: Tumors of the mandible are complex, often requiring replacement of bone, soft tissue, and teeth. The fibula flap has become a routine procedure in large tumors of the jaw, providing bone and soft tissue at the time of the resection. In current practice, dental reconstruction is delayed for 3 to 6 months, leaving the patient without teeth in the interim. This can be disfiguring and anxiety provoking for the patient. Methods: In this article, the authors present three patients with benign tumors of the mandible who underwent virtually guided resection, fibula reconstruction, and insertion of an implant-retained dental prosthesis in one operation. In addition, the authors report their early experience using this technique in the maxilla. Results: The authors present a case series of three patients with benign mandibular tumors and one patient with a benign maxillary tumor who underwent total reconstruction using computer-aided design and computer-aided manufacturing technology in a single stage. Conclusions: In the right situation, total mandibular reconstruction is possible in a single stage. This is demonstrated by the successful outcomes of these patients. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

Importance of computer-aided design and manufacturing technology in the multidisciplinary approach to head and neck reconstruction.

Head and neck reconstruction is a multidisciplinary field, requiring communication among various surgical and dental specialists. The free fibular flap is the standard method for reconstructing large mandibular defects after benign or malignant tumor ablation. The graft has to be precisely contoured to fit the three-dimensional defect to meet the functional and aesthetic goals.Virtual surgical planning using computed tomographic imaging and computer-aided design and manufacturing technology allows the surgeons to perform virtual surgery and generates templates and cutting guides that allow for the precise and expedient recreation of the plan in the operating room. The authors describe 2 cases where virtual planning was used for the extirpative and reconstruction phases to achieve precise reconstruction and decreased time under anesthesia.

Functional outcomes of virtually planned free fibula flap reconstruction of the mandible.

Background: The free fibula osteocutaneous flap has become the criterion standard for reconstruction of complex mandibular defects. The authors present their institutional experience with optimization of flap contouring and inset using virtual planning and prefabricated cutting jigs. Methods: All free fibula–based mandible reconstructions performed at the authors’ institution using virtual planning technology between 2009 and 2012 were retrospectively analyzed. The authors evaluated a variety of patient and procedural variables and outcomes. A series of cases performed before virtual planning was reviewed for comparison purposes. Results: Fifty-four reconstructions were performed in 52 patients. Patients were divided evenly between a private university-affiliated medical center and a large county hospital. The most common indications were malignancy (43 percent), ameloblastoma (26 percent), and osteonecrosis/osteomyelitis (23 percent). Thirty percent of patients had irradiation of the recipient site and 38 percent had previous surgery. Sixty-three percent of patients received dental implants, with 47 percent achieving functional dentition. Twenty-five percent of patients had immediate dental implant placement, and 9 percent had immediate dental restoration. Postoperative imaging demonstrated excellent precision and accuracy of flap positioning. Comparison with cases performed before virtual planning demonstrated increased complexity of flap design along with reduced operative time in the virtually planned group. Conclusions: Preoperative virtual planning along with use of prefabricated cutting jigs allows for precise contouring and positioning of microvascular fibula free flaps in mandibular reconstruction. Using this technique, the authors have achieved unprecedented rates of dental rehabilitation along with reduced operative times. The authors believe that virtual planning technologies are an emerging criterion standard in mandible reconstruction. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Congenital Neck Masses

Congenital neck lesions reflect abnormal embryogenesis in head and neck development. A thorough knowledge of embryology and anatomy is critical in the diagnosis and treatment of these lesions. The appropriate diagnosis of these lesions is necessary to provide appropriate treatment and long-term follow up, because some of these lesions may undergo malignant transformation or be harbingers of malignant disease.

Increasing bony contact and overlap with computer-designed offset cuts in free fibula mandible reconstruction.

Background The free fibula flap is the standard of care in mandibular reconstruction; however, procedural nuances continue to optimize results. More accurate and efficient osteotomies for graft insetting can be envisioned, which address the difficulty in obtaining a perfect match between the cut ends of the fibula and the mandible and the subsequent giving up of maximal bone contact. We propose a method of complementary offset osteotomies. The angled cuts were virtually planned using three-dimensional computed tomographic images. Optimal offset cuts maximized surface area contact and facilitated intraoperative repositioning in the setting of additional native bone margin requirement. Methods Using previously described protocols, three-dimensional virtual reconstructions of the facial skeleton and the fibula (average, series of five) were used to simulate osteotomies at 25, 30, 45, 60, 75, and 90 degrees to the long axis of the fibula. Complementary osteotomies were then simulated at the mandibular body just distal to the first molar in simulated free fibula reconstructions. Total area of apposing surfaces was calculated using computer-aided design. The results from the 25-, 30-, 45-, 60-, and 75-degree cuts were compared with the conventional 90-degree cut. Resin-based mandibular osteotomy guides and a complementary fibula jig were manufactured using computer-aided design. Two representative clinical cases were presented to illustrate proof of principle and benefits. Results The total surface area of apposing fibula and mandible surfaces in a conventional 90-degree cut was 103.8 ± 2.05 mm2. Decreasing this angle to 75, 60, 45, 30, and 25 degrees yielded increased surface areas of 0.86%, 10.3%, 35.3%, 136.7%, and 194.3%, respectively. Cuts of 25 degrees also allowed for adequate bony contact in the setting of additional margin requirements up to 2.77 cm. Complementary 45-degree cuts provided excellent bone-to-bone contact in a free fibula reconstruction using resin guides and a jig. This angle also facilitated access of the saw to the distal mandible. Conclusions Virtual surgical planning is an increasingly recognized technology for optimizing surgical outcomes and minimizing operative time. We present a technique that takes advantage of the precision complementary osteotomies that this technology affords. By creating offset cuts, we can maximize bony contact and ensure adequate contact should additional margins or intraoperative adjustments be required. This flexibility maximizes the precision of premanufactured cutting guides, mitigates the constraints of sometimes unpredictable intraoperative environments, and maximizes bony contact.

3D Volume Assessment Techniques and Computer-Aided Design and Manufacturing for Preoperative Fabrication of Implants in Head and Neck Reconstruction

Cases in subdisciplines of craniomaxillofacial surgery--corrective jaw surgery, maxillofacial trauma, temporomandibular joint/skull base, jaw reconstruction, and postablative reconstruction-illustrate the ease of use, cost effectiveness, and superior results that can be achieved when using computer-assisted design and 3D volumetric analysis in preoperative surgical planning. This article discusses the materials and methods needed to plan cases, illustrates implementation of guides and implants, and describes postoperative analysis in relation to the virtually planned surgery.

Plating in microvascular reconstruction of the mandible: can fixation be too rigid?

Objective: Determine long-term loss of mandible height with use of stress-shielding reconstruction plates for free fibula flap mandible reconstruction. Design: Retrospective single-blinded medical record review. Subjects: Seventy patients who had fibula free flap mandible reconstructions performed for 10 years. Patients who underwent radiotherapy were excluded. Methods: Review of 70 fibula free flap mandible reconstructions performed for the last 10 years in a city hospital revealed 7 patients (10%) who had resections for benign odontogenic diseases. All had a three-dimensional cast model made, on which the reconstruction plate was bent to the desired shape preoperatively. Free fibula height on panoramic x-ray images taken preoperatively and at 2 and 12 months postoperatively. Results: Seven (10%) patients met criteria for the study. Bone height was maintained at 2 months postoperatively, but at 12 months, there was a statistically significant loss of fibular bone height averaging 20% in the anterior, body, and ramus areas (P < 0.05). Despite this, all patients were considered eligible for dental rehabilitation, and 4 of 7 patients have had osseointegrated implants placed. Conclusions: As opposed to miniplates, increased resorption may have been due to the stress-shielding phenomenon unique to a reconstruction plates. However, this did not seem to affect the ability to place osseointegrated implants.

Ten-year evolution utilizing computer-assisted reconstruction for giant ameloblastoma.

BACKGROUND The authors describe our current practice of computer-aided virtual planned and pre-executed surgeries using microvascular free tissue transfer with immediate placement of implants and dental prosthetics. METHODS All patients with ameloblastomas treated at New York University (NYU) Medical Center during a 10-year period from September 2001 to December 2011 were identified. Of the 38 (36 mandible/2 maxilla) patients that were treated in this time period, 20 were identified with advanced disease (giant ameloblastoma) requiring aggressive resection. Reconstruction of the resultant defects utilized microvascular free tissue transfer with an osseocutaneous fibular flap in all 20 of these patients. RESULTS Of the patients reconstructed with free vascularized tissue transfer, 35% (7/20) developed complications. There were two complete flap failures with consequent contralateral fibula flap placement. Sixteen patients to date have undergone placement of endosteal implants for complete dental rehabilitation, nine of which received immediate placement of the implants at the time of the free flap reconstruction. The three most recent patients received immediate placement of dental implants at the time of microvascular free tissue transfer as well as concurrent placement of dental prosthesis. CONCLUSIONS To our knowledge, this patient cohort represents the largest series of comprehensive computer aided free-flap reconstruction with dental restoration for giant type ameloblastoma.