Biomedical subjects

Frank Langlotz

Publications and source records attributed to Frank Langlotz.

11 recordsLinked to original sources

PubMed2007

Noninvasive three-dimensional assessment of femoroacetabular impingement.

A CT-based method ("HipMotion") for the noninvasive three-dimensional assessment of femoroacetabular impingement (FAI) was developed, validated, and applied in a clinical pilot study. The method allows for the anatomically based calculation of hip range of motion (ROM), the exact location of the impingement zone, and the simulation of quantified surgical maneuvers for FAI. The accuracy of HipMotion was 0.7 +/- 3.1 degrees in a plastic bone setup and -5.0 +/- 5.6 degrees in a cadaver setup. Reliability and reproducibility were excellent [intraclass correlation coefficient (ICC) > 0.87] for all measures except external rotation (ICC = 0.48). The normal ROM was determined from a cohort of 150 patients and was compared to 31 consecutive hips with FAI. Patients with FAI had a significantly decreased flexion, internal rotation, and abduction in comparison to normal hips (p < 0.001). Normal hip flexion and internal rotation are generally overestimated in a number of orthopedic textbooks. HipMotion is a useful tool for further assessment of impinging hips and for appropriate planning of the necessary amount of surgical intervention, which represents the basis for future computer-assisted treatment of FAI with less invasive surgical approaches, such as hip arthroscopy.

Acetabulum↗

PubMed2006

Assessment of spline-based 2D-3D registration for image-guided spine surgery.

2D-3D registration of pre-operative 3D volumetric data with a series of calibrated and undistorted intra-operative 2D projection images has shown great potential in CT-based surgical navigation because it obviates the invasive procedure of the conventional registration methods. In this study, a recently introduced spline-based multi-resolution 2D-3D image registration algorithm has been adapted together with a novel least-squares normalized pattern intensity (LSNPI) similarity measure for image guided minimally invasive spine surgery. A phantom and a cadaver together with their respective ground truths were specially designed to experimentally assess possible factors that may affect the robustness, accuracy, or efficiency of the registration. Our experiments have shown that it is feasible for the assessed 2D-3D registration algorithm to achieve sub-millimeter accuracy in a realistic setup in less than one minute.

Algorithms↗

PubMed2006

Augmenting the effective field of view of optical tracking cameras--a way to overcome difficulties during intraoperative camera alignment.

An Internet survey demonstrated the existence of problems related to intraoperative tracking camera set-up and alignment. It is hypothesized that these problems are a result of the limited field of view of today's optoelectronic camera systems, which is usually insufficiently large to keep the entire site of surgical action in view during an intervention. A method is proposed to augment a camera's field of view by actively controlling camera orientation, enabling it to track instruments as they are used intraoperatively. In an experimental study, an increase of almost 300% was found in the effective volume in which instruments could be tracked.

Equipment Design↗

PubMed2006

Zero-dose fluoroscopy-based close reduction and osteosynthesis of diaphyseal fracture of femurs.

This paper presents a novel technique to create a computerized fluoroscopy with zero-dose image updates for computer-assisted fluoroscopy-based close reduction and osteosynthesis of diaphyseal fracture of femurs. With the novel technique, repositioning of bone fragments during close fracture reduction will lead to image updates in each acquired imaging plane, which is equivalent to using several fluoroscopes simultaneously from different directions but without any X-ray radiation. Its application facilitates the whole fracture reduction and osteosynthesis procedure when combining with the existing leg length and antetorsion restoration methods and may result in great reduction of the X-ray radiation to the patient and to the surgical team. In this paper, we present the approach for achieving such a technique and the experimental results with plastic bones.

Algorithms↗

PubMed2005

Anatomic referencing of cup orientation in total hip arthroplasty.

UNLABELLED: Pelvic tilt and rotation can drastically affect the apparent cup orientation on conventional anteroposterior pelvic radiographs. It was hypothesized that nonstandardized radiographic cup version and abduction can differ significantly from the corresponding anatomic angles if not measured to the anterior pelvic plane, defined by the pubic tubercles and the anterior superior iliac spine. Differences in preoperative and postoperative pelvic orientation and their influence on radiographic measurements of the two angles were analyzed. Conventional radiographs and preoperative and postoperative computed tomography scans of 37 total hip arthroplasties were compared. Calculations were made with the preoperative planning station of a computer navigation system. Significantly smaller values of cup version were seen on nonstandardized radiographs, whereas abduction could be measured reliably when referenced to horizontal pelvic landmarks seen on radiographs. The underlying cause for this difference was the variation of pelvic tilt that ranged 27 degrees (range, -7 degrees -20 degrees). Influence of pelvic tilt on the apparent cup orientation can be seen with simple nomograms. The orientation of the anterior pelvic plane before and after surgery did not differ. We think that version measurement on nonstandardized radiographs without anatomic referencing is highly inaccurate. LEVEL OF EVIDENCE: Diagnostic study, Level II-1 (development of diagnostic criteria on basis of consecutive patients--with universally applied reference "gold" standard). See Guidelines for Authors for a complete description of levels of evidence.

Acetabulum↗

PubMed2005

Computer-assisted LISS plate osteosynthesis of proximal tibia fractures: feasibility study and first clinical results.

Fluoroscopy is the most common tool for the intraoperative control of long-bone fracture reduction. Limitations of this technology include high radiation exposure for the patient and the surgical team, limited visual field, distorted images, and cumbersome verification of image updating. Fluoroscopy-based navigation systems partially address these limitations by allowing fluoroscopic images to be used for real-time surgical localization and instrument tracking. Existing fluoroscopy-based navigation systems are still limited as far as the virtual representation of true surgical reality is concerned. This article, for the first time, presents a reality-enhanced virtual fluoroscopy with radiation-free updates of in situ surgical fluoroscopic images to control metaphyseal fracture reduction. A virtual fluoroscopy is created using the projection properties of the fluoroscope; it allows the display of detailed three-dimensional (3D) geometric models of surgical tools and implants superimposed on the X-ray images. Starting from multiple registered fluoroscopy images, a virtual 3D cylinder model for each principal bone fragment is constructed. This spatial cylinder model not only supplies a 3D image of the fracture, but also allows effective fragment projection recovery from the fluoroscopic images and enables radiation-free updates of in situ surgical fluoroscopic images by non-linear interpolation and warping algorithms. Initial clinical experience was gained during four tibia fracture fixations that were treated by LISS (Less Invasive Stabilization System) osteosynthesis. In the cases operated on, after primary image acquisition, the image intensifier was replaced by the virtual reality system. In all cases, the procedure including fracture reduction and LISS osteosynthesis was performed entirely in virtual reality. A significant disadvantage was the unfamiliar operation of this prototype software and the need for an additional operator for the navigation system.

Adult↗

PubMed2004

Potential pitfalls of computer aided orthopedic surgery.

Computer aided orthopedic surgery (CAOS) systems are becoming more and more frequently used in operating rooms all over the world. While their clinical benefit is no longer doubted, there is considerable potential for using these devices incorrectly At best, mishandling of a CAOS system may lead to prolonged operating times. In the worst case scenario, incorrect navigational feedback is provided, which carries the potential risk of endangering the patient or resulting in an unacceptable surgical outcome. From an economical point of view only the optimal performance of a navigation system will probably justify its significant investment costs. This article summarizes some of the major pitfalls that may occur during surgical navigation. It is structured to reflect different types of CAOS systems, and it presents guidelines on how to avoid most of the problems. In general, a surgeon who wants to apply this technology needs to be very familiar with the system that is used. It is essential to know the basics and the limitations of the underlying technical principles. Otherwise, the large potential that modern CAOS systems make available cannot be exploited effectively for the benefit of the patient.

Fluoroscopy↗

PubMed2004

Computer aided reduction and imaging.

Reduction is one of the key procedures in orthopedic trauma surgery and has been acknowledged as one of the conditions for a good outcome in intraarticular and extra-articular fractures. The information available to the surgeon during the reduction maneuver can be divided into visual and tactile information. The optimal implementation of these parameters, combined with the surgeon's individual experience, will significantly affect the results of the operation. Anatomical regions where a limited direct view through the approach is supported by intraoperative imaging are intra-articular fractures of the elbow, forearm, acetabulum, proximal tibia, pilon, and hindfoot, and extra-articular fractures of the spine, pelvis, femur, and tibial shaft. Surgery in these regions is demanding since the approaches limit the visual control of the axes and also the anatomical reduction within the joint. Computer aided orthopedic surgery (CAOS) was introduced to increase the accuracy of selected procedures in orthopedic surgery. One of the most frequently applied applications is pedicle screw insertion in posterior spinal surgery. The current working group has identified computer aided reduction and implant positioning as an unresolved area of CAOS that would be highly relevant to the operative treatment of fractures. The development of tools for computer aided reduction is of major importance and is much desired by the orthopedic community. Such a reduction tool would be a significant step forward in the development of orthopedic trauma care. It would facilitate new procedures and new operations and also help to attain a completely new level with regard to what we can achieve in terms of minimal invasiveness and increased precision. The synergies of the expert group are deployed to develop the required software modules and hardware. Other areas of computer aided orthopedic surgery will certainly benefit from the integration of this technology as well.

Bone Screws↗

PubMed2004

Assessment of video tracking usability for training simulators.

OBJECTIVE: A simulator was developed to mimic commercial CAS systems in implementing most tasks required to carry out a surgical operation. As tracking systems are generally expensive components, an alternative solution based on low-cost video-based tracking was used. Video tracking accuracy was assessed to determine whether or not this kind of approach was suitable for use in the training domain. Ultimately, video-based tracking should enable sufficiently accurate registration between a bony model and its virtual 3D representation. MATERIALS AND METHODS: Video tracking was assessed using two types of camera. For each one, common accuracy tests were realized as a series of 10 trials at ranges of 0.5-1.0 m from the camera lens. The pointer used as a digitizer was equipped with tracked video markers. Three sizes of marker were evaluated to estimate the impact of marker size on accuracy. RESULTS: For the better of the two cameras tested, results were encouraging. Results are presented as rounded whole-number values in millimeters. The noise test gave accuracies of 2 mm for the 80-mm marker, 3 mm for the 60-mm marker and 5 mm for the 40-mm marker. Relative accuracies, as evaluated on a grid of equally spaced dots, were 4 mm with the 80-mm marker, 7 mm with the 60-mm marker and 12 mm with the 40-mm marker. A pivoting test around the pointer tip gave 3 mm of accuracy for the 80-mm marker, 5 mm for the 60-mm marker and 11 mm for the 40-mm marker. An additional pivoting test was completed on increasing the distance of the marker from the pointer tip, giving accuracies of 5 mm for the 80-mm marker, 6 mm for the 60-mm marker and 13 mm for the 40-mm marker. The registration test gave accuracies of 8 mm for the 80-mm marker, 9 mm for the 60-mm marker and 11 mm for the 40-mm marker. CONCLUSIONS: The video-based approach offers sufficient accuracy to achieve registration in the domain of CAS training.

Arthroplasty, Replacement, Hip↗

PubMedDate not supplied

Accuracy and potential pitfalls of fluoroscopy-guided acetabular cup placement.

Using a total of 30 cadaveric hips, the accuracy of a fluoroscopy-based computer navigation system for cup placement in total hip arthroplasty (THA) was investigated and an error analysis was carried out. The accuracy of placing the acetabular component within a predefined safe zone using computer guidance was compared to the precision that could be achieved with a freehand approach. Accurate control measurements of the implanted cup were obtained using fiducial-based matching to a pre-operative CT scan with respect to the anterior pelvic plane. A significantly higher number of cups were placed in the safe zone with the help of the navigation system. The variability of cup placement could be reduced for cup abduction but not substantially for cup version. An error analysis of inaccurate landmark reconstruction revealed that the registration of the mid-pubic point with fluoroscopy was a potential source of error. Keeping this pitfall in mind, fluoroscopy-based navigation in THA is a useful tool for registration of the pelvic coordinate system, particularly those points that cannot be reached by direct pointer digitization with the patient in the lateral decubitus position.

Acetabulum↗

PubMedDate not supplied

Endoscope-based hybrid navigation system for minimally invasive ventral spine surgeries.

The availability of high-resolution, magnified, and relatively noise-free endoscopic images in a small workspace, 4-10 cm from the endoscope tip, opens up the possibility of using the endoscope as a tracking tool. We are developing a hybrid navigation system in which image-analysis-based 2D-3D tracking is combined with optoelectronic tracking (Optotrak) for computer-assisted navigation in laparoscopic ventral spine surgeries. Initial results are encouraging and confirm the ability of the endoscope to serve as a tracking tool in surgical navigation where sub-millimetric accuracy is mandatory.

Endoscopes↗