High-frequency jet ventilation for endolaryngotracheal surgery--chart review and procedure analysis from the surgeon's and the anaesthesiologist's point of view.

OBJECTIVE: High-frequency jet ventilation (HFJV) arose as a ventilation alternative in laryngotracheal surgery as it offers the surgeon a better overview and more space for microsurgical manipulations. On the contrary, anaesthesiologic monitoring is limited and (relative) contraindications exist. The aim of this study was to evaluate the procedure. Contraindications and limitations are discussed from the surgeon's and the anaesthesiologist's point of view, and relevant aspects of oncologic surgery are identified. DESIGN: Retrospective chart review and analysis of clinical experiences. SETTING: University Teaching hospital. PATIENTS AND MAIN OUTCOME MEASURES: Eighty adult patients (97 cases) treated at our institution between June 2012 and September 2013 were included. HFJV was performed using thin, subglottically placed catheters. The analysis focuses on complications and practical steps. RESULTS: Indications were benign (63%) and malignant pathologies (37%). The CO2 laser was used in 34 cases (35%). The mean operating time averaged 53 min (3-404 min) and the mean duration of anaesthesia was 81 min (16-438 min). Two thirds of the operated patients had a body mass index higher than 25 kg/m(2) . Eighty-four per cent were classified as ASA I and II according to the American Society of Anesthesiologists. All pathologies could well be exposed by the surgeon. Two reversible desaturations to 70% were documented. In another case, emergency re-intubation was necessary as the saturation dropped below 50%. In 8 (8%) cases, elective re-intubation to conventional tubes was performed during the course of the operation as HFJV did not establish optimal oxygenation conditions. No severe intra-operative bleeding was observed. CONCLUSIONS: High-frequency jet ventilation represents a safe ventilation approach for laryngotracheal surgery in experienced hands. Due to the better overview, it offers a better orientation on anatomical structures and on the pathology. Special attention has to be laid on obesity, reflux and cardiopulmonary diseases. However, individual decisions can be made under consideration of all co-morbidities. A close pre- and intra-operative interdisciplinary work up is required.

[Reconstruction of complex midfacial defects with individualized titanium implants]. / Rekonstruktion komplexer Mittelgesichtsdefekte durch individualisierte Titanimplantate.

BACKGROUND: Loss of hard and soft tissue structures of the midface due to resection or trauma is associated with substancial functional and aesthetic deficits. Besides reconstruction of bony contours for preservation of orbit position and facial symmetry, reconstruction often requires simultaneous transplantation of soft tissue flaps for separation of nasal and oral cavities and refilling of soft tissue volume deficits. PATIENTS AND METHODS: A well-established procedure of our institution will be demonstrated in 10 exemplary patients, in which titanium meshes are customized for individual defect situations using computer-assisted techniques in combination with soft tissue transfer if required. RESULTS: According to our experience, this procedure provides satisfactory results in functional as well as in aesthetic respects. Especially in patients with loss of bony structures of the orbit and preservation of orbital contents, this procedure forms optimal preconditions for prevention of enophthalmos and diplopia by preservation of the original orbital volume. CONCLUSION: Individualized titanium implants should be used more frequently in clinical routine for reconstruction of complex midfacial defects.

Temporal bone imaging: comparison of flat panel volume CT and multisection CT.

BACKGROUND AND PURPOSE: A recent development in radiology is the use of flat panel detectors in CT to obtain higher-resolution images. This technique is known as flat panel volume CT (fpVCT). We sought to compare the image quality and diagnostic value of 2 different flat panel detector-equipped scanners: one is a prototype fpVCT scanner, and the other is a so-called flat panel digital volume tomography (fpDVT) scanner, which is routinely used in clinical setup with current state-of-the-art multisection CT (MSCT) scanners. MATERIALS AND METHODS: Five explanted temporal bones and 2 whole-head cadaveric specimens were scanned with fpVCT, fpDVT, and MSCT scanners. The image series were blindly evaluated by 3 trained observers who rated 38 anatomic structures with regard to their delineation/appearance. RESULTS: Although the image quality obtained with fpVCT and fpDVT was rated significantly better compared with MSCT on isolated temporal bones, the differences were not significant when whole cadaveric heads were scanned. CONCLUSIONS: Theoretic and practical advantages exist for flat panel detector-equipped scanners, including improved image quality. However, when imaging whole cadaveric heads, no significant difference could be demonstrated between them and standard-of-care MSCT.

Neuronavigational guidance in craniofacial approaches for large (para)nasal tumors involving the anterior skull base and upper clival lesions.

OBJECTIVE: Due to the destruction of osseous landmarks of the skull base or paranasal sinuses, the anatomical orientation during surgery of frontobasal or clival tumors with (para)nasal extension is often challenging. In this relation computer assisted surgical (CAS) guidance might be a useful tool. Here, we explored the use of CAS in an interdisciplinary setting. METHODS: The surgical series consists of 13 patients who underwent a lateral rhinotomy combined with a subfrontal craniotomy in case of significant intracranial tumor extension. The procedures were planned and assisted by advanced CAS techniques with image fusion of CT and MRI. Tumors included carcinomas (one case associated with an olfactory groove meningioma), esthesioneuroblastoma, chordoma, chondrosarcoma and ganglioglioma. RESULTS: The application of CAS in the combined approaches was both safe and reliable for delineation of tumors and identification of vital structures hidden or encased by the tumors. There was no perioperative 30-day mortality; however two patients died 5 weeks and 5 months after craniofacial tumor resection due to worsening medical conditions. The most common perioperative morbidity was postoperative wound complication in two cases. Tumors were either removed completely, or subtotal resection was achieved allowing targeted postoperative radiotherapy. CONCLUSION: Craniofacial approaches with intraoperative neuronavigational guidance in a multidisciplinary setting allow safe resection of large tumors of the upper clivus and the paranasal sinuses involving the anterior skull base. Complex skull base surgery with the involvement of bony structures appears to be an ideal field for advanced navigation techniques given the lack of intraoperative shift of relevant structures.

Cone beam CT imaging of airgun injuries to the craniomaxillofacial region.

In airgun injuries, the removal of the projectile is often recommended. The material properties of airgun projectiles make it difficult to determine their precise anatomical location using conventional radiological techniques. Conventional X-rays give only a two-dimensional representation of projectiles and do not allow a foreign object to be located precisely. Multi-slice computed tomography (CT) has become a standard tool in diagnosis. Metal objects can cause artefacts in CT scans and make it difficult to identify adjacent anatomical structures. By contrast, cone-beam CT (CBCT) provides three-dimensional images largely free from metal artefacts. The authors present three cases of airgun injuries and discuss the diagnostic and treatment approaches used. CBCT has proved to be a useful diagnostic tool in planning the treatment of craniofacial airgun injuries. It is superior to CT in detecting hard-tissue structural damage in the immediate vicinity of high-density metal projectiles.

[Update on computer- and mechatronic-assisted head and neck surgery in Germany]. / Update in der navigiert kontrollierten und mechatronisch assistierten Kopf-Hals-Chirurgie in Deutschland.

A consequence of the ongoing advances in medical navigation is the development of so-called mechatronic assistant systems. Up to now, medical navigation had been used only for additional intrasurgical orientation. But improvements in accuracy in imaging and medical navigation can exceed the surgeon's possible manual accuracy of surgical manipulation. In such cases, mechatronic assistant systems can supplement certain surgical procedures in order to obtain the required precision, such as for positioning of implants. The development and possible use of such mechatronic assistant systems in the head and neck, as well as improvements in the accuracy of medical navigation, are the focus of several working groups. For coordinating and adapting the various research projects, different research groups were called to present their current projects and results in the context of ASKRA (working group for skull-base and craniofacial surgery of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery) workshops at the German Society for Computer- and Robot-Assisted Surgery (CURAC) convention on 14 October 2006 in Hanover. Different projects were presented, with topics including navigated controlled assistant systems for the frontal and lateral skull base, possibilities for sonographic-induced bone measurement, and requirements for high-precision surgery of the skull base.

[Image-guided minimal-invasive cochlear implantation--experiments on cadavers]. / Navigationsgeführte minimal-invasive Cochlea-Implantation--Untersuchungen am humanen Felsenbein.

BACKGROUND: The accuracy of navigation systems can be improved significantly by using high-resolution flat panel-based Volume Computed Tomography (fpVCT) so that new surgical therapeutic concepts become feasible. A navigation-guided minimally-invasive cochleostomy places highest requirements on the accuracy of intraoperative navigation. METHODS: A flat-panel Volume Computed Tomograph (fpVCT) was used to scan four human temporal bones. The isometric voxel size was 200 microm. The preoperative planning was used to define an optimized drilling channel from the mastoid surface to the round window niche and the scala tympani providing a safety margin to critical anatomical structures such as facial nerve, chorda tympani, sigmoid sinus and posterior wall of auditory canal. The canal was drilled hand-operated with a navigated drill following the previously planned trajectory. Afterwards the drilled canal was imaged by fpVCT. Conventional dissection including mastoidectomy and posterior tympanotomy assured correct localization of the cochleostomy. RESULTS: Path planning took an average of 54 minutes (range 35-85 minutes). Installation took an average of 16 minutes (range 14-19 minutes). The drilling procedure itself took an average of 7.75 min (range 5-12 minutes.) The RMSE-values varied between 0.1 and 0.2 mm (Table 1). All four specimens showed a cochleostomy located at the scala tympani anterior inferior to the round window. The chorda tympani was damaged in one specimen--this was preoperatively planned as a narrow facial recess was encountered. The time needed for planning and system-installation could be reduced continuously. CONCLUSIONS: This feasibility study demonstrates that using current image-guided surgery technology in combination with fpVCT allows drilling of a minimally invasive channel to the cochlea with loco typico cochleostomy. The necessary accuracy of intraoperative navigation can be achieved by use of fpVCT (technical accuracy between 0.1 and 0.2 mm). Our results demonstrate the feasibility of a navigation-guided minimally-invasive cochleostomy loco typico. While we are enthused by this preliminary work, we recognize the barriers which exist in translation to clinical application. These include surgical issues (e.g. control of unexpected bleeding) and electrode issues (e.g. development of insertion tools).

Large scan field, high spatial resolution flat-panel detector based volumetric CT of the whole human skull base and for maxillofacial imaging.

OBJECTIVES: To assess the feasibility of flat-panel detector based volumetric CT (fpVCT) scanning of the whole human skull base and maxillofacial region, which has thus far only been demonstrated on small, excised specimens. Flat-panel detectors offer more favourable imaging properties than image intensifiers. It is therefore likely that they will replace them in cone-beam CT scanners that are currently used to scan parts of the skull base and maxillofacial region. Furthermore, the resolution of current CT imaging limits diagnosis, surgical planning and intraoperative navigation within these regions. fpVCT might overcome these limitations because it offers higher resolution of high contrast structures than current CT. METHODS: Three embalmed cadaver heads were scanned in two scanners: an experimental fpVCT that offers a scan field large enough for a whole human head, and in a current multislice CT (MSCT). 28 structures were compared. RESULTS: Both scanners produced bone images of diagnostic quality. Small high contrast structures such as parts of the ossicular chain and thin bony laminas were better delineated in fpVCT than in MSCT. fpVCT of maxillofacial region and skull base was rated superior to MSCT (P=0.002) as found in this limited, experimental study. CONCLUSIONS: High spatial resolution fpVCT scanning of both regions in a whole human head is feasible and might be slightly superior to MSCT. fpVCT could improve diagnostic accuracy in selected cases, as well as surgical planning and intraoperative navigation accuracy.

[Expansion of an ceruminous adenoma into the middle ear]. / Ausbreitung eines Zeruminaldrüsenadenoms in das Mittelohr.

A 37-year-old female presented for surgery with central perforation of the eardrum with granulation. Mastoidectomy had been performed 18 years ago following chronic mastoiditis. As the clinical picture now suggested a suspected cholesteatoma, radiological imaging was performed. The CT scan revealed specification of the mastoid and the tympanic cavity. In addition, MRI scan showed signal enhancement in the same areas. However, the suspected cholesteatoma could not be confirmed intraoperatively. Pathohistology revealed a ceruminal gland adenoma. They are a rare phenomenon and should be distinguished from middle ear adenomas, pleomorph ceruminal gland adenomas, ceruminal gland adenocarcinomas and cylindromas of the ceruminal glands. Owing to a high recurrence rate, complete surgical removal is necessary. Despite its rare occurrence, a ceruminal gland adenoma must be taken into consideration in the differential diagnosis of individual cholesteatoma cases.

Evaluation of surface and volume rendering in 3D-CT of facial fractures.

OBJECTIVES: Three-dimensional computed tomography (3D-CT) of facial fractures has been reported as beneficial using surface (SR) and volume rendering (VR). There are controversial statements concerning the preferable algorithm. The purpose of this study was to evaluate and compare SR and VR for clinical 3D-CT in facial fractures on an experimental basis. METHODS: Multislice CT was obtained in 22 patients with facial fractures using two data acquisition protocols. Five SR and VR post-processing protocols were applied. Five assessors independently evaluated the quality of visualization of the fracture gap and dislocated fragments as well as the overall image quality using a five-point rating scale. The potential benefit of the 3D-images for radiological diagnosis and presentation was evaluated. The influence of the data acquisition protocol was analysed. RESULTS: SR in general achieved better evaluation scores than VR at corresponding thresholds. Variation of evaluation scores for all criteria was found for SR and VR depending on the segmentation threshold. Apart from the overall image quality no significant influence of the data acquisition technique was found for the evaluated criteria. CONCLUSIONS: SR provided sufficient and time efficient means for 3D-visualization of facial fractures in this study. No diagnostic benefit of VR over SR was found.

[Navigation-supported surgery in the head and neck region]. / Navigationsgestützte Chirurgie im Kopf- und Hals-Bereich.

Few of the pioneering manufacturers who attempted to develop navigation systems have been able to establish themselves within the market long-term. The same applies to the technological basis of these systems which aid intraoperative anatomical orientation. The first few systems registered the mechanical displacement of the navigational instrument's axes. Optoelectronic and electromagnetic methods are now prevalent. In contrast to electromagnetic systems, the "line of sight" between the camera system, the reference markers placed on the patient's head and the navigation instruments must remain unobstructed during the navigation process when using electrooptical navigation systems. Whereas, in the past, only preoperative CT scans were used for navigation, the integration of MRI and sonography--whose images can now be fused with each other and with those provided by other intraoperative imaging techniques such as fluoroscopy and endosonography--has become increasingly popular. Navigation systems require input of information about spatial conditions. This is carried out via procedures of registration and referencing, by means of which the relative position of reference markers at the head of the patient is correlated with the image data. The equipment is calibrated in the same way. Headsets, headbands and bone-anchored adapters are available for the fixation of the markers in the patient's head. Whereas the use of a headband or headset requires considerably less time, bone-anchored referencing increases the precision of the navigation system. The surgeon must be able to manage the different methods. In order to reduce the time required for preoperative preparation and to enhance the handling of the navigation processor for the surgeon, it is essential to have a clear menu. The surgeon is able to plan the steps involved in the surgery using the processor, define the access to the surgical site and control the surgery intraoperatively. Preoperative segmentation of functionally and clinically relevant structures enables minimally invasive surgery to be carried out, such as procedures with the aim of acquiring biopsy tissue and the search for foreign bodies. Following the technical development of the systems, the manufacturers are endeavouring to simplify their handling in close coordination with the users. The next step has to be the clinical evaluation of the navigation systems in accordance with the EBM standard, in order to establish this assistive method as routine clinical practice while applying meaningful medical criteria.