Marco Caversaccio

A New System for Computer-Aided Preoperative Planning and Intraoperative Navigation During Corrective Jaw Surgery

A new system for computer-aided corrective surgery of the jaws has been developed and introduced clinically. It combines three-dimensional (3-D) surgical planning with conventional dental occlusion planning. The developed software allows simulating the surgical correction on virtual 3-D models of the facial skeleton generated from computed tomography (CT) scans. Surgery planning and simulation include dynamic cephalometry, semi-automatic mirroring, interactive cutting of bone and segment repositioning. By coupling the software with a tracking system and with the help of a special registration procedure, we are able to acquire dental occlusion plans from plaster model mounts. Upon completion of the surgical plan, the setup is used to manufacture positioning splints for intraoperative guidance. The system provides further intraoperative assistance with the help of a display showing jaw positions and 3-D positioning guides updated in real time during the surgical procedure. The proposed approach offers the advantages of 3-D visualization and tracking technology without sacrificing long-proven cast-based techniques for dental occlusion evaluation. The system has been applied on one patient. Throughout this procedure, we have experienced improved assessment of pathology, increased precision, and augmented control

Descending necrotizing mediastinitis: surgical treatment via clamshell approach.

BACKGROUND Descending necrotizing mediastinitis requires an early and aggressive surgical approach to reduce the high morbidity and mortality associated with this disease. The clamshell incision has provided excellent exposure of the entire mediastinum and both pleural cavities and was assessed in patients suffering from descending necrotizing mediastinitis. METHODS Three patients with descending necrotizing mediastinitis and bilateral pleural empyema due to invasive streptococcal infections were operated on with this method. Radical debridement of the mediastinum and bilateral decortication was performed through a clamshell incision, including pericardiectomy in 2 patients. All patients received initially a high dose of antibiotic regimen, 2 had bilateral chest tube drainage, and 1 had mediastinal drainage and pleural debridement via cervical mediastinotomy and thoracoscopy, respectively. All these measures alone, however, failed to control the disease. RESULTS The clamshell incision offered an excellent exposure for bilateral decortication and debridement of the entire mediastinum including pericardiectomy. One patient, who was referred in critically ill condition, died of multiorgan failure in the postoperative period. The remaining 2 patients recovered without further interventions and without evidence of phrenic nerve palsy, sternum osteomyelitis, or sternal override. CONCLUSIONS The clamshell approach offers an excellent exposure for a complete one-stage surgical treatment with mediastinal debridement and bilateral decortication in patients suffering from descending necrotizing mediastinitis in the absence of profound septic shock.

Characteristics and dimensions of the Schneiderian membrane: a radiographic analysis using cone beam computed tomography in patients referred for dental implant surgery in the posterior maxilla.

OBJECTIVES To determine the dimensions of the Schneiderian membrane using limited cone beam computed tomography (CBCT) in individuals referred for dental implant surgery, and to determine factors influencing the mucosal thickness. MATERIAL AND METHODS The study included 143 consecutive patients referred for dental implant placement in the posterior maxilla. A total of 168 CBCT images were taken using a limited field of view of 4 × 4 cm, 6 × 6 cm, or 8 × 8 cm. Reformatted coronal CBCT slices were analyzed with regard to the thickness and characteristics of the Schneiderian membrane in nine standardized points of reference. Factors such as age, gender, or status of the remaining dentition that could influence the dimensions of the Schneiderian membrane were evaluated using univariate and multivariate linear regression models. RESULTS The thickness of the Schneiderian membrane exhibited a wide range, with a minimum value of 0.16 mm and a maximum value of 34.61 mm. The highest mean values, ranging from 2.16 to 3.11 mm, were found for the mucosa located in the mid-sagittal regions of the maxillary sinus. The most frequent mucosal findings diagnosed were flat thickenings of the Schneiderian membrane (62 positive findings, 37%). For the multivariate linear regression model, only gender had a statistically significant influence on the mean overall and mid-sagittal thickness of the sinus mucosa. CONCLUSION There is great interindividual variability in the thickness of the Schneiderian membrane. Gender seems to be the most important parameter influencing mucosal thickness in asymptomatic patients. Future studies are needed to assess the therapeutic and prognostic consequences of mucosal alterations in the maxillary sinus.

Carcinoma ex pleomorphic adenoma: diagnostic difficulty and outcome

Objective To analyze a series of carcinoma ex pleomorphic adenoma (CXPA) and to assess the diagnostic difficulties. Study Design The clinical presentation of 24 CXPAs was compared with 300 pleomorphic adenomas (PAs). Furthermore, pathohistological findings and follow-up results of CXPAs were evaluated. Results Eight of 24 (33%) CXPAs versus 41 of 300 (14%) PAs were localized in the deep lobe (P < 0.05). Forty-two percent of CXPAs versus 6 percent of PAs, respectively, were greater than 4 cm (P < 0.05). The sensitivity in detecting CXPA by fine-needle aspiration cytology (FNAC) was 47 percent. The tumor was known to be malignant preoperatively in 10 (42%) patients. Six of 24 (25%) patients with CXPA developed a tumor recurrence. The overall 5-year survival rate of CXPA was 76 percent. Conclusion CXPAs are difficult to identify preoperatively. FNAC has a low accuracy and sensitivity. CXPAs versus PAs are significantly more frequently localized in the deep lobe and are significantly greater in size.

A self-developed and constructed robot for minimally invasive cochlear implantation

Abstract Conclusion: A robot built specifically for stereotactic cochlear implantation provides equal or better accuracy levels together with a better integration into a clinical environment, when compared with existing approaches based on industrial robots. Objectives: To evaluate the technical accuracy of a robotic system developed specifically for lateral skull base surgery in an experimental set-up reflecting the intended clinical application. The invasiveness of cochlear electrode implantation procedures may be reduced by replacing the traditional mastoidectomy with a small tunnel slightly larger in diameter than the electrode itself. Methods: The end-to-end accuracy of the robot system and associated image-guided procedure was evaluated on 15 temporal bones of whole head cadaver specimens. The main components of the procedure were as follows: reference screw placement, cone beam CT scan, computer-aided planning, pair-point matching of the surgical plan, robotic drilling of the direct access tunnel, and postoperative cone beam CT scan for accuracy assessment. Results: The mean accuracy at the target point (round window) was 0.56 ± 0.41 mm with an angular misalignment of 0.88 ± 0.40°. The procedural time for the registration process through the completion of the drilling procedure was 25 ± 11 min. The robot was fully operational in a clinical environment.

Frameless Computer-Aided Surgery System for Revision Endoscopic Sinus Surgery

To increase the intraoperative safety factor and to acquire anatomic assistance during revision endoscopic sinus surgery (RESS), we used an optical computer-aided surgery (CAS) system that we developed collaboratively in Bern, Switzerland. During 1 year, 25 RESSs were performed with CAS: recurrent polyposis (n = 20), recurrent frontal recess stenosis (n = 3), and recurrent frontal recess stenosis with mucocele (n = 2). These patients were compared with a control group of 10 patients undergoing RESS without CAS. The same surgeon (M.C.) performed all operations, and there were no minor or major complications in either group. The clinical inaccuracy of our system is between 0.5 and 2 mm with paired-point and surface matching. The navigation system is an important aid to surgeons in identifying anatomic landmarks that are typically difficult to visualize in this type of surgery, thus reducing the stress placed on the surgeon.

Esthesioneuroblastoma: irradiation alone and surgery alone are not enough

PURPOSE To evaluate the long-term outcome of patients with esthesioneuroblastoma treated with neoadjuvant or definitive radiotherapy (RT). METHODS AND MATERIALS Between 1980 and 2001, 28 patients with histologically confirmed esthesioneuroblastoma underwent RT, with a median dose of 60 Gy (range 38-73). The median age was 58 years (range 16-85). According to the Kadish classification, 4 patients had Stage A, 8 Stage B, and 16 Stage C tumors. Radical resection was performed in 13 cases, in 9 before RT and in 4 after RT because of stable or progressive disease. The outcome analyses included the median age (58 years), Kadish stage, skull base penetration, intraorbital extension, resection status, and total dose (<or=60 vs. >60 Gy). RESULTS After a mean follow-up of 68 months, 54% of patients were free of tumor progression. The 5- and 10-year local progression-free survival rate was 81% and 51%, respectively, and the disease-free survival rate was 70% and 25%, respectively. Four of ten deaths (4/10) were intercurrent, resulting in a cause-specific survival of 77% and 69% at 5 and 10 years, respectively. Radical resection offered significantly better local progression-free survival and disease-free survival (p <0.02). Skull base penetration (p <0.04), intraorbital extension (p <0.04), and Kadish C stage (p <0.06) were important for impaired disease-free survival. CONCLUSION Despite doses up to 73 Gy, radical RT cannot replace radical resection, which classifies esthesioneuroblastoma as rather radioresistant. Because of its biology and the high rates of late recurrence, we recommend a radical strategy with resection, high-dose RT, and simultaneous chemotherapy. We are aware that some tumors qualify for palliative treatment only.

Radionecrosis or tumor recurrence after radiation of laryngeal and hypopharyngeal carcinomas

OBJECTIVE: To analyze the incidence and diagnostic difficulties of radionecrosis vs tumor recurrence of laryngeal and hypopharyngeal carcinomas. STUDY DESIGN AND SETTING: Retrospective study on 341 patients treated by radiation alone or radiochemotherapy. The clinicopathologic findings, work-up, treatment, and follow-up of 20 patients with symptoms suggestive but negative for tumor recurrence on initial imaging studies and endoscopy were analyzed. RESULTS: The incidence of chondroradionecrosis in 341 irradiated patients was 5%. Ten of 20 patients initially negative for tumor recurrence were treated by total laryngectomy; in all laryngectomy specimens, chondroradionecrosis was present, in six specimens associated with tumor recurrence. Ten patients were treated by tracheotomy and tumor recurrence was detected in one patient during follow-up. CONCLUSION: Chondroradionecrosis is a relatively rare treatment complication. Typical imaging findings suggestive of radionecrosis are often missing. Tumor recurrence may be present beneath an intact mucosa and missed by endoscopy.

Virtual simulator as a training tool for endonasal surgery

Background Virtual simulation could be an important tool for medical and surgical training as well as education. The efficacy of a simulator for endoscopic nasal procedures in a training program was evaluated. Methods The simulator is a medical and scientific tool for visualizing and interacting with three-dimensional volumetric data. Twenty endonasal operations with chronic rhinosinusitis were simulated by two 3rd-year residents and proctored by the senior surgeon 1 day before the actual surgery was performed with an endoscope and computer-aided surgery. A questionnaire was established. Results The surgical simulator may provide a better understanding of the morphology of the paranasal sinuses with a minor impact on performance of endoscopy by junior residents. Disadvantages identified were time consumption, absence of force feedback, and subtle handling of the joysticks. Conclusion The virtual simulator allows the nonendoscopically nasal trained surgeon to understand and practice endonasal surgery using real-patient data but failed to make an impact on operating room performance. Furthermore, the simulators effectiveness was limited by the absence of force feedback, subtle handling of the joysticks, and considerable time consumption.

In vitro accuracy evaluation of image-guided robot system for direct cochlear access

Hypothesis A previously developed image-guided robot system can safely drill a tunnel from the lateral mastoid surface, through the facial recess, to the middle ear, as a viable alternative to conventional mastoidectomy for cochlear electrode insertion. Background Direct cochlear access (DCA) provides a minimally invasive tunnel from the lateral surface of the mastoid through the facial recess to the middle ear for cochlear electrode insertion. A safe and effective tunnel drilled through the narrow facial recess requires a highly accurate image-guided surgical system. Previous attempts have relied on patient-specific templates and robotic systems to guide drilling tools. In this study, we report on improvements made to an image-guided surgical robot system developed specifically for this purpose and the resulting accuracy achieved in vitro. Materials and Methods The proposed image-guided robotic DCA procedure was carried out bilaterally on 4 whole head cadaver specimens. Specimens were implanted with titanium fiducial markers and imaged with cone-beam CT. A preoperative plan was created using a custom software package wherein relevant anatomical structures of the facial recess were segmented, and a drill trajectory targeting the round window was defined. Patient-to-image registration was performed with the custom robot system to reference the preoperative plan, and the DCA tunnel was drilled in 3 stages with progressively longer drill bits. The position of the drilled tunnel was defined as a line fitted to a point cloud of the segmented tunnel using principle component analysis (PCA function in MatLab). The accuracy of the DCA was then assessed by coregistering preoperative and postoperative image data and measuring the deviation of the drilled tunnel from the plan. The final step of electrode insertion was also performed through the DCA tunnel after manual removal of the promontory through the external auditory canal. Results Drilling error was defined as the lateral deviation of the tool in the plane perpendicular to the drill axis (excluding depth error). Errors of 0.08 ± 0.05 mm and 0.15 ± 0.08 mm were measured on the lateral mastoid surface and at the target on the round window, respectively (n =8). Full electrode insertion was possible for 7 cases. In 1 case, the electrode was partially inserted with 1 contact pair external to the cochlea. Conclusion The purpose-built robot system was able to perform a safe and reliable DCA for cochlear implantation. The workflow implemented in this study mimics the envisioned clinical procedure showing the feasibility of future clinical implementation.