Accuracy of a Modern Intraoperative Navigation System for Temporal Bone Surgery in a Cadaveric Model

Objectives

To determine the accuracy of a modern navigation system in temporal bone surgery. While routine in other specialties, navigation has had limited use in the temporal bone due to issues of accuracy, perceived impracticality, and value.

Study Design

Prospective observational study.

Setting

Temporal bone laboratory.

Subjects and Methods

Eighteen cadaveric specimens were dissected after rigid fiducials were implanted and computed tomography scans were obtained. Target registration and target localization errors were then measured at various points.

Results

The mean overall target registration error was 0.48 ± 0.29 mm. The mean target localization error was 0.54 mm at the sinodural angle, 0.48 mm at the lateral semicircular canal, 0.55 mm at the round window, 0.39 mm at the oval window, and 0.52 mm at the second genu of the facial nerve.

Conclusion

A modern navigation system demonstrated submillimeter accuracy for all points of interest. Its use in clinical as well as training settings has yet to be fully elucidated.

Endoscopic Transethmosphenoidal Approach for Pituitary Tumors with Image Guidance

The advantages of endoscopic transethmosphenoidal surgery for pituitary tumors using a navigation system were reported. The surgical technique was as follows. First, sphenoidal sinuses were opened via the bilateral ethmoidal sinuses and the olfactory clefts. Then the septum of the sphenoidal sinuses was resected. Next, an endoscope was inserted via the left nasal cavity and fixed in place. The tumor was then removed via the right nasal cavity. Our approach for pituitary tumors provided sufficient working space and permitted the surgeon to carry out the procedure using both hands. In addition, use of the InstaTrak System made it possible to recognize the orientation of the surgical field in the sella turcica. Thus, the tumor could be resected more easily and safely. It is concluded that this approach will be particularly useful for patients with narrow nasal cavities or poor development of the paranasal sinuses.

Endoscopic Transnasal Pituitary Surgery: Report on 180 Cases

The endoscopic transnasal approach is an evolving technique for treating lesions in the sella turcica. Since this method was introduced at our institution 4 years ago, the majority of transsphenoidal procedures are performed with it. The records of all patients having endoscopic transnasal hypophysectomy at the Mayo Clinic during the last 4 years were reviewed retrospectively. The criteria analyzed were safety, functional and cosmetic outcome, and complications. During the 4-year period, the operative procedure was modified to improve operative exposure and safety. The results of our review showed a significant decrease in length of hospital stay, reduced operative time, reduced need for nasal packing, and elimination of a sublabial incision. The complication rate was equivalent to that reported for the traditional transseptal transsphenoidal approach. As the neurosurgeons at our institution gained experience with this approach, an increasing number of pituitary microadenomas were resected safely and successfully. In addition, because of the limited septal dissection, this approach is particularly helpful for revision operations. This approach also can be used for the full range of pituitary lesions and in conjunction with adjunctive techniques, including frontal craniotomy and -knife irradiation. Currently, the endoscopic transsphenoidal approach is the method preferred for surgically treating pituitary lesions in adults at our institution.

Image-guidance in endoscopic sinus surgery: is it associated with decreased medicolegal liability?

BACKGROUND

The use of image-guidance (IG) in endoscopic sinus surgery (ESS) has escalated over the last decade despite a lack of consensus that its use improves outcomes or decreases complications. One theoretical reason for using IG in ESS is its potential to minimize legal liability should an adverse outcome occur. In this study, we aimed to characterize the role of IG in ESS litigation, and further detail other factors in pertinent cases. A secondary objective was to characterize recent malpractice litigation for other relevant factors.

METHODS

Relevant cases from Westlaw were examined to determine whether the use of IG played a role in initiating litigation in ESS malpractice suits. Factors such as patient demographics and alleged cause(s) of malpractice litigation were examined.

RESULTS

Out of 30 malpractice cases from 2004 to April 2013, 4 (13.3%) mentioned the use of IG during ESS, although this did not appear to be a factor affecting the plaintiff's decision to initiate litigation, nor the case outcomes. In the 26 cases (86.7%) in which IG was not used, its non-use was not specified as an alleged cause of negligence. Eleven (36.7%) cases were resolved in the defendant's favor. Frequently-cited factors included iatrogenic injury (83.3%), permanent deficits (66.7%), needing additional surgery (63.3%), orbital and intracranial injury, and perceived deficits in informed consent (40.0%).

CONCLUSION

The use of IG was not found to be a factor in ESS litigation. This suggests that not using IG does not necessarily make one more vulnerable to malpractice litigation.

Use of real‐time magnetic resonance image guidance in endoscopic sinus surgery

We evaluated the effectiveness of magnetic resonance image (MRI) guidance using an optical tracking system (MRI-guided therapy: MRT) in performing endoscopic sinus surgery (ESS). The profiles of the fourteen patients in the present study were as follows: eleven with mucocele in the paranasal sinus, one with recurrent chronic sinusitis, one with maxillary cancer, and one with Graves' ophthalmopathy. Preparation of the MRT system required an additional 54 min in cases involving general anesthesia, and an additional 17 min in cases involving local anesthesia, in comparison with corresponding control groups undergoing ESS in a traditional operating room. We developed nonmetal probes that were visualized in a real-time mode and assistive devices for the optical tracking system that were equipped to avoid obstruction caused by surgical instruments as well as by the hands of surgeons. Using these unique devices, anatomic landmarks were visualized using the present MRT system. The prognosis of patients was favorable, and in particular, no patients with sinus mucocele showed a recurrence of their lesions. We concluded that the MRT system used here for performing ESS was beneficial, especially in terms of the intranasal marsupialization of sinus mucoceles and for the verification of orbital contents.

[Evaluation of force data with a force/torque sensor during FESS. A step towards robot-assisted surgery]

BACKGROUND

To relieve the surgeon during functional endoscopic endonasal sinus surgery (FESS), the endoscope should be guided by autonomous robot assistance. The surgeon will thus have two hands free for suctioning and manipulation during FESS.

PATIENTS/METHODS

With a force/torque sensor mounted on the endoscope, we measured forces in six degrees of freedom in five cadaver heads and in 20 actual endoscopic sinus procedures. On the cadaver heads we performed complete endoscopic endonasal dissection of all paranasal sinuses. All forces at the endoscope were monitored continuously.

RESULTS

The mean forces occurring at the endoscope were 3.2 N. There were only slight differences between the in vivo and ex vivo data. We measured peak forces up to 25.2 N. In 95% of all cases, forces were lower than 7 N.

CONCLUSION

Forces up to 7 N are sufficient for endoscopic guidance during FESS. Peak forces are distinctive for endoscopic guidance by humans and could be optimised by sensor-based intraoperative robot guidance. Higher forces are required for surgical endoscopy of the frontal and maxillary sinuses compared with the ethmoid sinuses.

Experimental image-guided endoscopic pituitary surgery: a useful learning model

OBJECTIVES

The purpose of this study, which combined image guidance and endocscopic pituitary surgery (EPS), was to test its practicability as a learning tool to acquire the necessary skills in an experimental setting.

METHODS

Ten cadaver-heads were explored using a standard endoscopic transsphenoidal surgical technique combined with the InstaTrak 3500 (GE Medical Systems, Lawrence, MA, USA) image guidance system. The time taken for the experimental setup and the optic-radiologic correlations of topographic landmarks were recorded and photographed.

RESULTS

The average time for setting up the system was 11.9 min+/-2.0, which included head fixation, headset positioning, registration, calibration and verification of the system. With the guidance of the navigation system, the ostium, sellar floor and adjacent structures encountered during EPS could be identified easily and were reflected on the 3D-CT images accurately.

CONCLUSION

The experimental model validated the practicability of image guidance combined with EPS. The non-invasive interactive computer-assisted CT-guided navigational system facilitated the surgical procedure by providing precise spatial relationship between instrument position and adjacent structures. This combination is a useful teaching and learning tool in the cadaver and in patients will be useful, particularly for complex cases and redo-surgery.

[The use of the BrainLAB Kolibri navigation system in endoscopic paranasal sinus surgery under local anaesthesia. An analysis of 35 cases]

BACKGROUND

As a result of technological advances, 3D-navigation systems are playing an increasingly important role in paranasal sinus and anterior skull base surgery.

PATIENTS AND METHODS

The BrainLAB Kolibri navigation system (BrainLAB, Heimstetten, Germany) was used in the surgical management of chronic sinusitis and nasal polyposis in 35 patients. Surgery was performed under local anaesthesia. In order to compare this technique with traditional methods, 35 additional patients underwent conventional surgery. A clinical plausibility test using specific anatomical landmarks was performed to evaluate intraoperative navigation accuracy. In addition, a standardised questionnaire was used to document setup and registration times. Standardised rating scales helped assess whether the system can make surgery safer.

RESULTS

It took approximately 5.8 min to set up the navigation system. The time required for system and patient positioning, including the attachment of the headband, was 4.2 min on average. Patient registration with the z-touch system was completed after an average of 4.2 min. It took an average of approximately 8.1 min to register a patient using the soft-touch system. The use of the navigation system increased the total time for preparation and surgery by approximately 50% in comparison to the conventional technique. An average accuracy of 1.5-2.3 mm in all three planes was measured. Participating surgeons felt that the system made surgery considerably safer.

CONCLUSIONS

The BrainLAB Kolibri navigation system offers good accuracy, a short setup time and an easy registration technique. The combination of these qualities and intuitive operation make this system a suitable option for routine use in paranasal sinus surgery. As a result of its compactness, the BrainLAB Kolibri navigation system can be moved easily between different operating rooms and can also be used in small facilities (e.g. container operating theatres in field hospitals).

Computers in Otorhinolaryngology : New horizons

There has been an explosion in the computers and information technology in the past couple of years. Otorhinolaryngology has also seen a number of new applications of computers. This article aims to familiarize the reader with different uses of computers as applied to the field of Otorhinolaryngology. It deals with the role in medical literature search, patient and doctor education, medical record Keeping, telemedicine, internet and E-mail. creating virtual environments and its role in FESS, skull base tumors and plastic surgery.

Efficacy of computed tomographic image--guided endoscopic sinus surgery in residency training programs

OBJECTIVE

To determine the efficacy of computed tomographic image-guided endoscopic surgery in the hands of inexperienced surgeons.

STUDY DESIGN

Four second-year otolaryngology residents, with no prior experience performing ethmoidectomies, performed endoscopic sinus surgery (ESS) on formalin-fixed human cadaveric specimens with and without the aid of computer-assisted surgery (CAS).

METHODS

Each resident was asked to identify critical sinus, orbital, and skull base structures while performing a total ethmoidectomy and multiple sinusotomies. Their surgical accuracy (percentage of correctly identified structures), total operative time, and incidence of major complications were recorded for each side. A total of 16 sides were evaluated (8 with and 8 without CAS). Statistical significance between groups was determined by means of Pearson's chi2 analysis.

RESULTS

Statistical analysis showed a significant difference (P = .001) in the mean accuracy of identifying critical anatomical landmarks between the CAS (97%) and non-CAS (76.8%) groups. Although not statistically significant, operative time appeared to be longer in the group using CAS (average of 67 vs. 80 min). Three major intracranial complications were documented only in the group not using CAS.

CONCLUSIONS

Although, unquestionably, a thorough knowledge of the anatomy remains essential for performing ESS, CAS improves surgical accuracy and reduces the risk of major intracranial or intraorbital complications for residents. In additional, our data suggest that this technology may enhance surgical efficiency and improve the learning curve by reducing operative time (below one's normal baseline) while maintaining a greater than 90% accuracy in identifying critical anatomical landmarks.

Computers in otorhinolaryngology; new horizons

There has been an explosion in the computers and information technology in the past couple of years. Otorhinolaryngology has also seen a number of new applications of computers. This article aims to familiarize the reader with different uses of computers as applied to the field of Otorhinolaryngology. It deals with the role in medical literature search, patient and doctor education, medical record keeping telemedicine, internet and E-mail, creating virtual environments and its role in FESS. skull base tumours and plastic surgery.

A combined, minimally invasive transnasal approach to the sella turcica

The increasing use of endonasal techniques and a new 3-dimensional CT-guided imaging system have allowed us to develop a combined, minimally invasive endonasal approach to the pituitary gland. Thus far, more than 30 patients have undergone an endonasal transsphenoidal approach to the sella using a combined endoscopic approach, with additional selective use of the Instatrak CT-guided imaging system for real-time imaging. Our current technique involves obtaining a preoperative CT using a plastic head frame with registration markers. By using this head frame intraoperatively, real-time localization with CT images in axial, coronal, and sagittal planes can be performed. Using endoscopic techniques and a Papavero-Caspar speculum, the sella is exposed. A combined approach using endoscopes, the operating microscope, and real-time localization is undertaken to expose and resect tumors. We have encountered minimal associated complications in our series, and this method has been progressively modified to improve exposure and safety. Because we are able to visualize the sella without a sublabial incision or septal resection, we have nearly eliminated the need for nasal packing, reduced the average hospital stay to 2.5 days, and improved patient satisfaction.

Endoscopic sinus surgery with magnetic resonance imaging guidance: initial patient experience

We report the first endoscopic surgeries performed with patients under general anesthesia using intraoperative guidance with MRI. The procedures were experimental and intended to test (1) the unusual working environment of a unique new "open-configuration" MRI unit for head and neck surgery, and (2) real-time image guidance. Twelve patients underwent endoscopic sinus surgery while under general anesthesia in a new open MRI unit that provides the surgeon with access to the patient while imaging is performed. Eleven patients had chronic sinusitis (eight of them had bilateral disease), and one had a right nasoethmoid and antral tumor. All 12 surgeries were performed without complications. Both the endoscopic view and the MRI scans were available at the surgical field. The image plane was surgeon controlled, and the MRI updated images in as little as 14 seconds. MRI provided adequate visualization of both the disease and the related anatomy and allowed the surgeon to navigate during the procedure. The intraoperative data reflect the tissue changes during surgery and provide optimum feedback for surgical guidance. Although the operating environment poses some limitations, it has become apparent that intraoperative MRI has a role in the treatment of head and neck disorders and warrants further study.

Computer-augmented endoscopic sinus surgery

Review of current literature on computer-augmented endoscopic sinus surgery reflects a sustained interest in developing a role for available frameless stereotactic technologies to provide image guidance for the surgeon. The interest is motivated by the prospect of increased intraoperative patient safety in that image guidance assists the surgeon in navigating through diseased or surgically revised complex anatomy. The authors feel that in time the technique will enable a new level of efficiency in endoscopic sinus surgery.