Biomedical subjects

Frank Langlotz

Publications and source records attributed to Frank Langlotz.

5 recordsLinked to original sources

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↗