Kirschner wire placement in scaphoid bones using intraoperative CT-guided stereotaxy.

BACKGROUND: Minimally invasive ostesynthesis of scaphoid fractures may reduce the risk of fracture non-union and shorten the duration of illness. The aim of this study was to analyze the technical feasibility and targeting accuracy of computed tomography (CT) - guided stereotactic Kirschner (K)-wire positioning in the scaphoid. METHODS: Nineteen Formalin preserved cadaveric upper extremities (10 right, 9 left) were fixed in 90 degree dorsal extension for percutaneous access from palmar. An ideal central position of the K-wire was planned on the computer adapted from intraoperative CT data. A 3D navigation system and stereotactic targeting device were used for K-wire placement. Target positioning errors were evaluated by fusion of the control CT with the K-wire in place with the planning CT. RESULTS: The procedure allowed for an easy and rigid wrist fixation. K-wire placement showed mean ± SD lateral targeting errors of 0.9 ± 0.5 mm at the scaphoid bone entry and 1.2 ± 0.7 mm at the K-wire tip. The mean angular error was 1.3° ± 1.1° . Total duration of the intervention ranged between 19 and 23 min. CONCLUSION: CT-guided stereotactic K-wire placement in scaphoid bones is highly accurate. The technique may guide minimally invasive screw-osteosynthesis of scaphoid fractures.

The Aouda.X space suit simulator and its applications to astrobiology.

We have developed the space suit simulator Aouda.X, which is capable of reproducing the physical and sensory limitations a flight-worthy suit would have on Mars. Based upon a Hard-Upper-Torso design, it has an advanced human-machine interface and a sensory network connected to an On-Board Data Handling system to increase the situational awareness in the field. Although the suit simulator is not pressurized, the physical forces that lead to a reduced working envelope and physical performance are reproduced with a calibrated exoskeleton. This allows us to simulate various pressure regimes from 0.3-1 bar. Aouda.X has been tested in several laboratory and field settings, including sterile sampling at 2800 m altitude inside a glacial ice cave and a cryochamber at -110°C, and subsurface tests in connection with geophysical instrumentation relevant to astrobiology, including ground-penetrating radar, geoacoustics, and drilling. The communication subsystem allows for a direct interaction with remote science teams via telemetry from a mission control center. Aouda.X as such is a versatile experimental platform for studying Mars exploration activities in a high-fidelity Mars analog environment with a focus on astrobiology and operations research that has been optimized to reduce the amount of biological cross contamination. We report on the performance envelope of the Aouda.X system and its operational limitations.

Accuracy and diagnostic yield of CT-guided stereotactic liver biopsy of primary and secondary liver tumors.

OBJECTIVE: CT-guided biopsy still plays a decisive role in the management of liver tumors, especially if the lesions are not visible or accessible by ultrasound. As CT-guided stereotaxy appears to be a very accurate targeting technique, the aim of this study was to evaluate the targeting accuracy, diagnostic yield, and complications of CT-guided stereotactic liver biopsy of primary and secondary liver tumors. METHODS AND MATERIALS: Prior to stereotactic liver biopsy, patients under general anesthesia were immobilized using a vacuum cushion. Respiratory motion was controlled by temporary disconnections of the endotracheal tube. An optical-based navigation system was used for 3D trajectory planning and placement of a 15-G coaxial needle via a stereotactic aiming device. The histological samples were obtained using a 16-G Tru-Cut(™) biopsy needle system. For evaluation of targeting accuracy the control CT image with the needles in place was fused with the planning CT image. The lateral error at the tip and skin entry point and the angular error were calculated. In addition, the skin-to-liver-surface (SL) distance, the needle-to-liver-surface (NL) angle, and the presence of liver cirrhosis were evaluated. The diagnostic yield was evaluated by histological reports from the institutional pathologists. RESULTS: The median lateral error was 2.5 mm (range: 0-6.5 mm) at the needle entry point and 3.2 mm (range: 0.01-9.4 mm) at the needle tip. The median angular error was 1.06° (range: 0-6.64°). Liver cirrhosis, NL angle and SL distance showed no significant impact on the targeting accuracy. Forty-five of the 46 liver biopsies (97.8%) were diagnostic according to the histological reports. No puncture-related complications such as bleeding or perforation of intestinal organs or lung tissue were recorded.

Two-dimensional fluoroscopic navigation in posterior cruciate ligament reconstruction: a preclinical cadaver study.

OBJECTIVES: To assess the feasibility and accuracy of frameless stereotactic two-dimensional fluoroscopy-assisted guide pin (GP) placement in posterior cruciate ligament (PCL) reconstruction in human cadavers. MATERIALS AND METHODS: A total of 13 pins were placed in 7 cadaver specimens, using a fluoroscopic-based navigation technique. The knees were fixed noninvasively on a carbon baseplate. Interventions were planned on intraoperatively acquired perpendicular fluoroscopic images. A stereotactic aiming device was mounted to the carbon baseplate and adjusted according to the planned trajectories. GPs were advanced through the aiming device to the precalculated depth. GP positions were verified by image fusion of the fluoroscopic planning and control data, respectively. Measurements were scored on three occasions by one independent observer. In order to assess interobserver reliability, measurements were scored by two further independent observers on one occasion. RESULTS: The femoral cohort included seven GP placements in seven cadavers. Mean GP placement accuracy according to plan was 1.3 mm (SD 0.9 mm, range 0.3-3.8 mm) at the target point. The recorded femoral angular misalignment of GPs was 1.1 degrees (SD 0.9 degrees , range 0.2 degrees -3.3 degrees ). The tibial cohort included six GP placements in six cadavers. Mean GP placement accuracy according to the plan was 1.8 mm (SD 2.1 mm, range 0.3-9.5 mm). The recorded tibial angular misalignment of GPs was 1.4 degrees (SD 1.1 degrees , range 0.1 degrees -5 degrees ). Navigated GP implantation, as planned, was optimal in six out of seven cases in the femoral cohort and in four out of six cases in the tibial cohort. CONCLUSION: Our preliminary cadaver study suggests that the use of fluoroscopic-based navigation combined with a stereotactic targeting device may be a helpful tool to improve PCL reconstruction. In addition, this method may also be used for other minimal invasive skeletal interventions.