Impact of a self-developed planning and self-constructed navigation system on skull base surgery: 10 years experience

CONCLUSION: Our self-developed planning and navigation system has proven its capacity for accurate surgery on the anterior and lateral skull base. With the incorporation of augmented reality, image-guided surgery will evolve into 'information-guided surgery'. OBJECTIVE: Microscopic or endoscopic skull base surgery is technically demanding and its outcome has a great impact on a patient's quality of life. The goal of the project was aimed at developing and evaluating enabling navigation surgery tools for simulation, planning, training, education, and performance. This clinically applied technological research was complemented by a series of patients (n=406) who were treated by anterior and lateral skull base procedures between 1997 and 2006. MATERIALS AND METHODS: Optical tracking technology was used for positional sensing of instruments. A newly designed dynamic reference base with specific registration techniques using fine needle pointer or ultrasound enables the surgeon to work with a target error of < 1 mm. An automatic registration assessment method, which provides the user with a color-coded fused representation of CT and MR images, indicates to the surgeon the location and extent of registration (in)accuracy. Integration of a small tracker camera mounted directly on the microscope permits an advantageous ergonomic way of working in the operating room. Additionally, guidance information (augmented reality) from multimodal datasets (CT, MRI, angiography) can be overlaid directly onto the surgical microscope view. The virtual simulator as a training tool in endonasal and otological skull base surgery provides an understanding of the anatomy as well as preoperative practice using real patient data. RESULTS: Using our navigation system, no major complications occurred in spite of the fact that the series included difficult skull base procedures. An improved quality in the surgical outcome was identified compared with our control group without navigation and compared with the literature. The surgical time consumption was reduced and more minimally invasive approaches were possible. According to the participants' questionnaires, the educational effect of the virtual simulator in our residency program received a high ranking.

Virtual autopsy using imaging: bridging radiologic and forensic sciences. A review of the Virtopsy and similar projects

The transdisciplinary research project Virtopsy is dedicated to implementing modern imaging techniques into forensic medicine and pathology in order to augment current examination techniques or even to offer alternative methods. Our project relies on three pillars: three-dimensional (3D) surface scanning for the documentation of body surfaces, and both multislice computed tomography (MSCT) and magnetic resonance imaging (MRI) to visualise the internal body. Three-dimensional surface scanning has delivered remarkable results in the past in the 3D documentation of patterned injuries and of objects of forensic interest as well as whole crime scenes. Imaging of the interior of corpses is performed using MSCT and/or MRI. MRI, in addition, is also well suited to the examination of surviving victims of assault, especially choking, and helps visualise internal injuries not seen at external examination of the victim. Apart from the accuracy and three-dimensionality that conventional documentations lack, these techniques allow for the re-examination of the corpse and the crime scene even decades later, after burial of the corpse and liberation of the crime scene. We believe that this virtual, non-invasive or minimally invasive approach will improve forensic medicine in the near future.

Radiation exposure to the surgeon during fluoroscopically assisted percutaneous vertebroplasty: a prospective study

STUDY DESIGN: A prospective case control study design was conducted. OBJECTIVES: The purpose of the current study was to determine the intraoperative radiation hazard to spine surgeons by occupational radiation exposure during percutaneous vertebroplasty and possible consequences with respect to radiation protection. SUMMARY OF BACKGROUND DATA: The development of minimally invasive surgery techniques has led to an increasing number of fluoroscopically guided procedures being done percutaneously such as vertebroplasty, which is the percutaneous cement augmentation of vertebral bodies. METHODS: Three months of occupational dose data for two spine surgeons was evaluated measuring the radiation doses to the thyroid gland, the upper extremities, and the eyes during vertebroplasty. RESULTS: The annual risk of developing a fatal cancer of the thyroid is 0.0025%, which means a very small to small risk. The annual morbidity (the risk of developing a cancer including nonfatal ones) is 0.025%, which already means a small to medium risk. The dose for the eye lens was about 8% of the threshold dose to develop a radiation induced cataract (150 mSv); therefore, the risk is very low but not negligible. The doses measured for the skin are 10% of the annual effective dose limit (500 mSv) recommended by the ICRP (International Commission on Radiologic Protection); therefore, the annual risk for developing a fatal skin cancer is very low. CONCLUSION: While performing percutaneous vertebroplasty, the surgeon is exposed to a significant amount of radiation. Proper surgical technique and shielding devices to decrease potentially high morbidity are mandatory. Training in radiation protection should be an integral part of the education for all surgeons using minimally invasive radiologic-guided interventional techniques.

Percutaneous autologous venous valve transplantation: short-term feasibility study in an ovine model

BACKGROUND: Limited experience with bioprosthetic venous valve percutaneously inserted into femoral veins in 15 patients has been promising in short-term results only to show disappointing long-term results. Percutaneous autogenous venous valve (PAVV) transplantation was explored in an ovine model as a possible alternative treatment. METHODS: PAVV consisted of a vein segment containing a valve that was attached to a stent template. The stent templates (n = 9) were designed and hand made in our research laboratory. They consist of two stainless steel square stents 13 or 15 mm in diameter to fit the ovine jugular veins (JV), which ranges from 10 to 15 mm in diameter. A valve-containing segment of JV was harvested and attached with sutures and barbs inside the stent template (n = 9). The valve devices were then manually folded and front loaded inside the 4 cm chamber of the 13F delivery sheath and delivered into the contralateral JV by femoral vein approach. Transplanted PAVVs were studied by immediate and 3 months venograms. Animals were euthanized at 3 months, and jugular veins harvested to perform angioscopic evaluations in vitro. RESULTS: PAVV transplantation was successful in all nine animals. Good valve function with no reflux was observed on immediate and 3 months venograms in eight valves. The transplanted maximal JV diameter ranged from 10.2 mm to 15.4 mm (mean 13.1 +/- 1.5 mm). Venoscopic examination revealed intact, flexible, nonthickened valve leaflets in eight specimens. One PAVV exhibited normal function of one leaflet only; the other cusp was accidentally cut during the transplantation procedure. All transplanted autologous valves were free of thrombus and incorporated into the vein wall of the host vessel. CONCLUSION: This study demonstrated that autogenous valve transplants remained patent and competent without long-term anticoagulation for up to 3 months. The percutaneous autogenous venous valve may provide in future minimally invasive treatment for patients with chronic deep venous insufficiency, but long-term studies need to be done to document its continued patency and function.

CT data-based navigation for post-mortem biopsy-a feasibility study

INTRODUCTION: Recent advances in medical imaging have brought post-mortem minimally invasive computed tomography (CT) guided percutaneous biopsy to public attention. AIMS: The goal of the following study was to facilitate and automate post-mortem biopsy, to suppress radiation exposure to the investigator, as may occur when tissue sampling under computer tomographic guidance, and to minimize the number of needle insertion attempts for each target for a single puncture. METHODS AND MATERIALS: Clinically approved and post-mortem tested ACN-III biopsy core needles (14 gauge x 160 mm) with an automatic pistol device (Bard Magnum, Medical Device Technologies, Denmark) were used for probe sampling. The needles were navigated in gelatine/peas phantom, ex vivo porcine model and subsequently in two human bodies using a navigation system (MEM centre/ISTB Medical Application Framework, Marvin, Bern, Switzerland) with guidance frame and a CT (Emotion 6, Siemens, Germany). RESULTS: Biopsy of all peas could be performed within a single attempt. The average distance between the inserted needle tip and the pea centre was 1.4mm (n=10; SD 0.065 mm; range 0-2.3 mm). The targets in the porcine liver were also accurately punctured. The average of the distance between the needle tip and the target was 0.5 mm (range 0-1 mm). Biopsies of brain, heart, lung, liver, pancreas, spleen, and kidney were performed on human corpses. For each target the biopsy needle was only inserted once. The examination of one body with sampling of tissue probes at the above-mentioned locations took approximately 45 min. CONCLUSIONS: Post-mortem navigated biopsy can reliably provide tissue samples from different body locations. Since the continuous update of positional data of the body and the biopsy needle is performed using optical tracking, no control CT images verifying the positional data are necessary and no radiation exposure to the investigator need be taken into account. Furthermore, the number of needle insertions for each target can be minimized to a single one with the ex vivo proven adequate accuracy and, in contrast to conventional CT guided biopsy, the insertion angle may be oblique. Navigation for minimally invasive tissue sampling is a useful addition to post-mortem CT guided biopsy.

Postmortem whole-body CT angiography: evaluation of two contrast media solutions

OBJECTIVE: The objective of our study was to establish a standardized procedure for postmortem whole-body CT-based angiography with lipophilic and hydrophilic contrast media solutions and to compare the results of these two methods. MATERIALS AND METHODS: Minimally invasive postmortem CT angiography was performed on 10 human cadavers via access to the femoral blood vessels. Separate perfusion of the arterial and venous systems was established with a modified heart-lung machine using a mixture of an oily contrast medium and paraffin (five cases) and a mixture of a water-soluble contrast medium with polyethylene glycol (PEG) 200 in the other five cases. Imaging was executed with an MDCT scanner. RESULTS: The minimally invasive femoral approach to the vascular system provided a good depiction of lesions of the complete vascular system down to the level of the small supplying vessels. Because of the enhancement of well-vascularized tissues, angiography with the PEG-mixed contrast medium allowed the detection of tissue lesions and the depiction of vascular abnormalities such as pulmonary embolisms or ruptures of the vessel wall. CONCLUSION: The angiographic method with a water-soluble contrast medium and PEG as a contrast-agent dissolver showed a clearly superior quality due to the lack of extravasation through the gastrointestinal vascular bed and the enhancement of soft tissues (cerebral cortex, myocardium, and parenchymal abdominal organs). The diagnostic possibilities of these findings in cases of antemortem ischemia of these tissues are not yet fully understood.

Two-step postmortem angiography with a modified heart-lung machine: preliminary results

OBJECTIVE: The purpose of this study was to adapt and improve a minimally invasive two-step postmortem angiographic technique for use on human cadavers. Detailed mapping of the entire vascular system is almost impossible with conventional autopsy tools. The technique described should be valuable in the diagnosis of vascular abnormalities. MATERIALS AND METHODS: Postmortem perfusion with an oily liquid is established with a circulation machine. An oily contrast agent is introduced as a bolus injection, and radiographic imaging is performed. In this pilot study, the upper or lower extremities of four human cadavers were perfused. In two cases, the vascular system of a lower extremity was visualized with anterograde perfusion of the arteries. In the other two cases, in which the suspected cause of death was drug intoxication, the veins of an upper extremity were visualized with retrograde perfusion of the venous system. RESULTS: In each case, the vascular system was visualized up to the level of the small supplying and draining vessels. In three of the four cases, vascular abnormalities were found. In one instance, a venous injection mark engendered by the self-administration of drugs was rendered visible by exudation of the contrast agent. In the other two cases, occlusion of the arteries and veins was apparent. CONCLUSION: The method described is readily applicable to human cadavers. After establishment of postmortem perfusion with paraffin oil and injection of the oily contrast agent, the vascular system can be investigated in detail and vascular abnormalities rendered visible.

Percutaneous vertebroplasty, kyphoplasty and lordoplasty: implications for the anesthesiologist

PURPOSE OF REVIEW: Vertebroplasty, kyphoplasty and lordoplasty are minimally invasive procedures mainly performed for refractory pain due to osteoporotic vertebral body fractures. This review summarizes recent findings on outcome, complications and their impact on anesthetic management. RECENT FINDINGS: Despite an increasing number of publications on surgical technique, therapeutic efficacy and side effects of these interventions, anesthetic management per se is hardly investigated. All three treatments provide similar pain relief. Adverse effects include local cement leakage and new fractures adjacent to augmented vertebrae. Asymptomatic pulmonary cement embolism occurs in 4.6-6.8% of patients depending on cement viscosity, injection pressure and number of injected vertebrae. Potentially life-threatening embolism of cement or fat may occur. Kyphoplasty and lordoplasty aim at correcting vertebral deformity and are equally effective; lordoplasty is substantially less expensive, however. The incidence of systemic cement or fat embolism is similar to that in vertebroplasty. Whereas vertebroplasty is mostly performed under local anesthesia and sedation, general anesthesia is required for kyphoplasty and lordoplasty. The anesthetic regimen follows the principles of anesthesia in the elderly population. SUMMARY: Vertebroplasty, kyphoplasty and lordoplasty are effective minimally invasive treatments for stable vertebral compression fractures without compression of the spinal canal. The anesthesiologist must be prepared to manage systemic cement or fat embolism.

Serum lipoproteins during treatment with the antihypertensive agent indapamide

Considering the documented, potentially undesirable influence of various thiazide-type or loop diuretics on serum lipoproteins, we prospectively investigated in 69 men (mean age +/- SEM, 32 +/- 1 years) the metabolic effects of the new diuretic-antihypertensive compound indapamide. Compared to placebo, indapamide (2.5 mg/day) given for 6 to 8 weeks lowered (p less than 0.02 to less than 0.001) blood pressure (supine values from 148/98 +/- 3/2 to 137/93 +/- 3/2) in 29 men with mild to moderate essential hypertension, but not in 40 healthy men. In both groups, significant (p less than 0.05 to less than 0.001) decreases in body weight (-0.8 kg) and plasma potassium (-0.6 mmol/L), and increases in plasma uric acid (+20%), renin activity (+200%), and aldosterone documented good compliance. There were no significant changes in total cholesterol (in all subjects, from 208 +/- 6 to 213 +/- 6 mg/dl), low- or very low-density lipoprotein (VLDL) cholesterol (127 +/- 6 to 129 +/- 6 and 21 +/- 1 to 21 +/- 2 respectively), high-density lipoprotein cholesterol (50 +/- 1 to 51 +/- 1 mg/dl), total triglycerides (Tg) (108 +/- 5 to 112 +/- 6 mg/dl), VLDL-Tg, apoproteins A1 and A2, plasma glucose, epinephrine, norepinephrine, sodium, calcium, magnesium, and creatinine; apoprotein B (84 +/- 2 to 88 +/- 3 mg/dl) and plasma insulin after glucose loading dose tended to be increased minimally. The absence of distinct lipoprotein alterations after short-term indapamide treatment may be of clinical and epidemiological interest.

Fenestrated and branched endografts: why we need them now

Standard endovascular repair of abdominal aortic aneurysm (AAA) has been shown to be associated with significant advantages compared with conventional surgery in the perioperative time frame related to the minimally invasive nature of the procedure. Given the encouraging long-term results of endovascular AAA repair, this method is increasingly applied to patients with complex AAA anatomies. The present article reviews the indications for branched and fenestrated endografts in various aortic pathologic processes.

Comparative study of anchorage strengths of epoxy coated hooked bars

Hooked reinforcing bars (rebar) are used frequently to carry the tension forces developed in beams and transferred to columns. Research into epoxy coated hooked bars has only been minimally performed and no research has been carried out incorporating the coating process found in ASTM A934. This research program compares hooked rebar that are uncoated, coated by ASTM A775, and coated by ASTM A934. In total, forty-two full size beam-column specimens were created, instrumented and tested to failure. The program was carried out in three phases. The first phase was used to refine the test setup and procedures. Phase two explored the spacing of column ties within the joint region. Phase three explored the three coating types found above. Each specimen included two hooked rebar which were loaded and measured independently for relative rebar slip. The load and displacement of the hooked rebar were analyzed, focusing on behavior at the levels of 30 ksi, 42 ksi and 60 ksi of rebar stress. Statistical and general comparisons were made using the coating types, tie spacing, and rebar stress level. Many of the parameters composing the rebar and concrete were also tested to characterize the components and specimens. All rebar tested met ASTM standards for tensile strength, but the newer ASTM A934 method seemed to produce slightly lower yield strengths. The A934 method also produced coating thicknesses that were very inconsistent and were higher than ASTM maximum limits in many locations. Continuity of coating surfaces was found to be less than 100% for both A775 and A934 rebar, but for different reasons. The many comparisons made did not always produce clear conclusions. The data suggests that the ACI Code (318-05) parameter of 1.2 for including epoxy coating on hooked rebar may need to be raised, possibly to 2.5, but more testing needs to be performed before such a large value change is set forth. This is particularly important as variables were identified which may have a larger influence on rebar capacity than the Development Length, of which the current 1.2 factor modifies. Many suggestions for future work are included throughout the thesis to help guide other researchers in carrying out successful and productive programs which will further the highly understudied topic of hooked rebar.

[Computer-aided surgery of the paranasal sinuses and the anterior skull base]

Endoscopic or microscopic surgery for chronic rhinosinusitis with or without nasal polyps is a routine intervention in daily practice. It is often a delicate and difficult minimally invasive intervention in a narrow space, with a tunnel view of 4 mm in the case of endoscopy and frequent bleeding in chronically inflamed tissue. Therefore, orientation in such a "labyrinth" is often difficult. In the case of polyp recurrence or tumors, the normal anatomical landmarks are often missing, which renders orientation even more difficult. In such cases, computer-aided navigation together with images such as those from computed tomography or magnetic resonance imaging can support the surgeon to make the operation more accurate and, in some cases, faster. Computer-aided surgery also has great potential for education.

A diagnostically challenging case of ureterovaginal fistula after laparoscopic hysterectomy

A complicated case of iatrogenic ureterovaginal fistula in a 56-year-old woman after laparoscopic-assisted vaginal hysterectomy, which persisted after several attempts of repair including ureterocystoneostomy, is presented. Accurate radiologic work-up enabled us to identify a refluxing ureteral stump, which was not ligated at the time of ureterocystoneostomy, as the origin of urinary leakage. Surgical principles that should be adhered to when managing such complex cases to obtain successful long-lasting outcome are described.

A safe and simple solution for intravesical tension-free vaginal tape erosion: removal by standard transurethral resection

OBJECTIVE: To report our experience with the successful removal of visible tension-free vaginal tape (TVT) by standard transurethral electroresection, as intravesical tape erosion after TVT is a rare complication, and removal can be challenging, with few cases reported. PATIENTS AND METHODS: Five patients presenting with TVT erosion into the bladder were treated at our institutions from December 2004 to July 2007; all had standard transurethral electroresection. Their records were reviewed retrospectively to retrieve data on presenting symptoms, diagnostic tests, surgical procedures and outcomes. RESULTS: The median (range) interval between the TVT procedure and the onset of symptoms was 17 (1-32) months. The predominant symptoms were painful micturition, recurrent urinary tract infection (UTI), urgency and urge incontinence. There were no complications during surgery. The storage symptoms and UTI resolved completely after removing the eroded mesh in all but one patient. Cystoscopy at 1 month after surgery showed complete healing of the bladder mucosa. CONCLUSION: Although TVT erosion into the bladder is rare, persistent symptoms, particularly recurrent UTIs, must raise some suspicion for this condition. Standard transurethral electroresection seems to be a safe, simple, minimally invasive and successful treatment option for TVT removal.

Accuracy of navigated surgery of the pelvis after surface matching with an a-mode ultrasound probe

Computer-aided surgery (CAS) allows for real-time intraoperative feedback resulting in increased accuracy, while reducing intraoperative radiation. CAS is especially useful for the treatment of certain pelvic ring fractures, which necessitate the precise placement of screws. Flouroscopy-based CAS modules have been developed for many orthopedic applications. The integration of the isocentric flouroscope even enables navigation using intraoperatively acquired three-dimensional (3D) data, though the scan volume and imaging quality are limited. Complicated and comprehensive pathologies in regions like the pelvis can necessitate a CT-based navigation system because of its larger field of view. To be accurate, the patient's anatomy must be registered and matched with the virtual object (CT data). The actual precision within the region of interest depends on the area of the bone where surface matching is performed. Conventional surface matching with a solid pointer requires extensive soft tissue dissection. This contradicts the primary purpose of CAS as a minimally invasive alternative to conventional surgical techniques. We therefore integrated an a-mode ultrasound pointer into the process of surface matching for pelvic surgery and compared it to the conventional method. Accuracy measurements were made in two pelvic models: a foam model submerged in water and one with attached porcine muscle tissue. Three different tissue depths were selected based on CT scans of 30 human pelves. The ultrasound pointer allowed for registration of virtually any point on the pelvis. This method of surface matching could be successfully integrated into CAS of the pelvis.