Biomedical subjects

O Ploder

Publications and source records attributed to O Ploder.

13 recordsLinked to original sources

PubMed2005

[Isolated fractures of the orbital floor].

BACKGROUND: The goal of this retrospective study was quantitative calculation of area and volume of isolated orbital floor fractures from computed tomography (CT) and correlation of these data with post-traumatic ophthalmologic findings. PATIENTS AND METHODS: A total of 76 patients with isolated orbital floor fractures were evaluated radiologically and clinically. CT scanning was performed in coronal sections (1.5-mm to 3.0-mm slice thickness) with contiguous table feed. Orbital floor and fracture area as well as volume of displaced tissue were measured and calculated from the CT dataset. The relation of quantitative CT data to ophthalmologic findings (motility, diplopia, and globe position) was assessed statistically. RESULTS: Calculation of the CT dataset revealed a mean orbital floor area of 6.33+/-1.05 cm(2), a mean fracture area of 2.60+/-1.14 cm(2), and a mean volume of displaced tissue of 1.16+/-0.80 cm(3). Volume of displaced tissue correlated significantly with ophthalmologic findings (p< or =0.01). Fracture area correlated significantly with globe position (p< or =0.01) and was less associated with diplopia and motility disturbances (p<0.10). CONCLUSION: Efficient evaluation of two-dimensional CT data enables quantitative assessment of orbital floor fractures. Position and function of the globe are mainly affected by the volume of displaced periorbital tissue.

Adult↗

PubMed2005

Preoperative radiochemotherapy and radical resection for stages II to IV oral and oropharyngeal cancer: grade of regression as crucial prognostic factor.

The purpose of this study was to assess the prognostic value of histological response to preoperative radiochemotherapy in an established multimodal therapy concept for advanced oral and oropharyngeal cancer. Two hundred and twenty-two patients who underwent preoperative radiochemotherapy (RCT: 50 Gy, mitomycin C and fluorouracil) and radical surgery were retrospectively evaluated. Resected tumours of all patients were histologically analysed and response to RCT was classified in histopathological grades of regression (RG). In a multivariate statistical analysis, RG was compared with established factors regarding their predictive value for overall and disease-specific survival. The 5-year overall survival probability in the different groups of histopathological regression grades were: RG1 (no vital tumour): 73.4%, RG2 (minimal tumour remnants encompassing less than 5%): 72.1%, RG3 (5-50% vital tumour cells): 41.9%, RG4 (more than 50% vital tumour): 37.9%. For disease-specific survival probability no significant differences were found between both groups of "responders" (RG1 and RG2) nor between "non-responders" (RG3 and RG4), whereas responders and non-responders differed significantly from each other (log-rank test; p < 0.001). T-classification, N-classification and disease stage, histological grading, tumour site, age, and sex had less prognostic value than RG in a Cox regression model. In the neoadjuvant multimodal therapy concept, histological response to preoperative RCT is a crucial prognostic factor even when surgical R0-resection is accomplished. Thus, non-responders have to be regarded as high-risk patients for recurrence and may benefit from further therapy.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2003

Follow-up study of treatment of orbital floor fractures: relation of clinical data and software-based CT-analysis.

This retrospective study quantifies isolated orbital floor fractures using software-based CT-analysis and compares the clinical outcome across surgical and non-surgical treatment groups. Depending on the surgeon's interpretation of the clinical and radiological appearance, 10 fractures were treated non-surgically and 20 fractures surgically, either with antral balloon catheter alone or in combination with an orbital implant. Ophthalmologic findings were evaluated until 12 weeks after injury. Fracture area, and volume of displaced tissue (VDT) were assessed by software-based CT-analysis. VDT was marginally significantly smaller in non-surgically than in surgically-treated patients (P=0.08). Ophthalmologic findings improved in all groups during follow-up and no statistical difference was found between the groups. Diplopia remained moderate in three patients with balloon catheter alone, and minimal in four patients in both surgical groups. In one patient with non-surgical treatment, diplopia remained minimal after 12 weeks. Although CT-analysis revealed no significant difference between both surgical groups, patients treated with balloon catheter alone presented more diplopia after 12 weeks. Using balloon catheters for fracture repair a combined approach should be performed when large fractures involve the orbital floor to achieve sufficient reduction of orbital content and placement of an orbital implant. Software-based CT-analysis is helpful for objective interpretation in managing of orbital fractures.

Adult↗

PubMed2001

A computer-based method for calculation of orbital floor fractures from coronal computed tomography scans.

PURPOSE: A computer program recently developed for the calculation of the orbital floor and fracture areas from coronal computed tomography (CT) scans was used in a study to evaluate the accuracy and ability of this new method. MATERIAL AND METHODS: The size of orbital floors and fabricated fractures in 14 dried, anatomic specimens were measured in coronal CT scans by 3 independent observers. Based on this data set, the orbital floor and fracture regions were calculated with the newly developed computer program. These calculated regions were then compared with a direct measurement of the specimens that had been obtained by digital photography. The accuracy of the computer-based calculations was assessed using Lin's concordance correlation coefficient. RESULTS: The size of the orbital floor (mean +/- SD) was found to be 5.21 +/- 0.39 cm(2) by direct measurement of the specimens and 5.30 +/- 0.52 cm(2) by calculation with the computer program. The region of the fracture (mean +/- SD) was 1.05 +/- 0.64 cm(2) by direct measurement and 1.01 +/- 0.62 cm(2) by computer calculation. The between-method mean difference (direct measurement minus computer based calculation) was -0.09 cm(2) (or 1.7% of mean orbital floor region) for orbital floor region and 0.04 cm(2) (or 3.8% of mean fracture region) for fracture region. CONCLUSIONS: This accurate and time-saving method is practicable for determining the size and location of orbital floor fractures. This calculation program can be advantageously applied in the clinical management of blowout fractures of the orbit.

Algorithms↗

PubMed2001

Reperfusion of autotransplanted teeth--comparison of clinical measurements by means of dental magnetic resonance imaging.

OBJECTIVE: Dental magnetic resonance imaging (dMRI) with administration of contrast material is one method of assessing pulpal perfusion. The purpose of this study was to evaluate the level of contrast enhancement displayed by means of dMRI after transplantation of teeth and to compare these findings with the results of tooth mobility, pocket depth, cold, and electrical tests. STUDY DESIGN: Twenty-three teeth with either complete root formation or incomplete root formation (IRF) were investigated by using dMRI and were clinically examined at intervals of 2, 4, 8, and 12 weeks, as well as 6 months and 12 months after transplantation. RESULTS: An analysis of the enhancement in the dental images revealed a significant difference between teeth with IRF and teeth with complete root formation. In addition, the time to occurrence of a positive reaction to the cold test was significantly longer for teeth with IRF. CONCLUSIONS: The findings of this study indicate that transplanted IRF teeth are associated with reperfusion seen by means of dMRI as well as with delayed occurrence of a positive cold test.

Adolescent↗

PubMed1999

[Distraction osteogenesis with a fully implantable system. Experimental study].

Distraction osteogenesis using external or intraoral devices is an established method for lengthening the human mandible. In this preliminary study on sheep, a completely implanted device for mandibular lengthening is presented. After osteotomy of the mandible, the electromechanical device was fixed to the mandible and the power and control unit were inserted subcutaneously in the neck region. After a healing period of 5 days, the device was activated magnetically and allowed calibrated distraction steps of 0.04 mm/h, achieving a total of 1.0 mm per day. With this method, it was possible to lengthen the mandible automatically over a period of 14 days without transmucosal activation. In our study, this newly designed internal device was successfully used for distraction osteogenesis, and a maximum mandibular lengthening of 13.6 mm was achieved. Further research is necessary to achieve progression to human clinical application in the near future.

Animals↗

PubMed1999

Mandibular lengthening with an implanted motor-driven device: preliminary study in sheep.

Distraction osteogenesis with external or intraoral devices is an established method for lengthening human mandibles. In this preliminary study in three sheep a newly designed, fully implantable electromechanical device for mandibular lengthening was used. After osteotomy, the device was screw fixed to the mandible, and the power and control unit was inserted subcutaneously in the neck region. After a healing period of five days, the device was activated magnetically, allowing calibrated distraction steps of 0.04 mm/h, resulting in a total of 1.0 mm/day. Over a period of 14 days, a maximum mandibular lengthening of 13.6 mm could be achieved without transmucosal activation. Depending on stability of the screw fixation, membranous and/or cartilaginous bone formation was observed in the callus by radiological and histological evaluation. Further experimental research is ongoing to prove the clinical usefulness of this device.

Animals↗

PubMed1997

Computed intraoperative navigation guidance--a preliminary report on a new technique.

OBJECTIVE: To assess the value of a computer-assisted three-dimensional guidance system (Virtual Patient System) in maxillofacial operations. DESIGN: Laboratory and open clinical study. SETTING: Teaching Hospital, Austria. SUBJECTS: 6 patients undergoing various procedures including removal of foreign body (n=3) and biopsy, maxillary advancement, and insertion of implants (n=1 each). INTERVENTIONS: Storage of computed tomographic (CT) pictures on an optical disc, and imposition of intraoperative video images on to these. The resulting display is shown to the surgeon on a micromonitor in his head-up display for guidance during the operations. MAIN OUTCOME MEASURES: To improve orientation during complex or minimally invasive maxillofacial procedures and to make such operations easier and less traumatic. RESULTS: Successful transferral of computed navigation technology into an operation room environment and positive evaluation of the method by the surgeons involved. CONCLUSIONS: Computer-assisted three-dimensional guidance systems have the potential for making complex or minimally invasive procedures easier to do, thereby reducing postoperative morbidity.

Adult↗

PubMed1996

Image-guided surgery.

Interventional video tomography (IVT), a new imaging modality, achieves virtual visualization of anatomic structures in three dimensions for intraoperative stereotactic navigation. Partial immersion into a virtual data space, which is orthotopically coregistered to the surgical field, enhances, by means of a see-through head-mounted display (HMD), the surgeon's visual perception and technique by providing visual access to nonvisual data of anatomy, physiology, and function. The presented cases document the potential of augmented reality environments in maxillofacial surgery.

Foreign Bodies↗

PubMed1996

[Experiences and results in management of mandibular fractures with the modified Krenkel lag screw--a retrospective study].

The stable osteosynthesis of mandibular fractures with the modified lag screw (Krenkel) has proven superior to conventional lag screws in theoretical models and clinical use. Compared to osteosynthesis with plate systems, the lag screw technique is more difficult to learn for the unexperienced, but the reduction of fragments under compression with a lag screw and the stabilisation of lower jaw rotation with an additional short miniplate in our experience has proven successful in clinical use.

Adolescent↗

PubMed1996

Augmented reality environment for temporomandibular joint motion analysis.

The principles of interventional video tomography were applied for the real-time visualization of temporomandibular joint movements in an augmented reality environment. Anatomic structures were extracted in three dimensions from planar cephalometric radiographic images. The live-image fusion of these graphic anatomic structures with real-time position data of the mandible and the articular fossa was performed with a see-through, head-mounted display and an electromagnetic tracking system. The dynamic fusion of radiographic images of the temporomandibular joint to anatomic temporomandibular joint structures in motion created a new modality for temporomandibular joint motion analysis. The advantages of the method are its ability to accurately examine the motion of the temporomandibular joint in three dimensions without restraining the subject and its ability to simultaneously determine the relationship of the bony temporomandibular joint and supporting structures (ie, occlusion, muscle function, etc) during movement before and after treatment.

Adult↗

PubMed1995

Virtual image guided navigation in tumor surgery--technical innovation.

We present a new visualization system for image-guided stereotactic navigation in tumor surgery. The combination of frameless stereotactic localization technology with real-time video processing permits the visualization of medical imaging data as a video overlay during the actual surgical procedure. Virtual computer-generated anatomical structures are displayed intraoperatively in a semi-immersive head-up display. This results in surgical navigation assistance without limiting the judgement of the physician based on the continuous observation of the operating field. The case presented documents the potential of augmented reality visualization concepts in tumor surgery of the head.

Computer Simulation↗

PubMed1995

[Computer-assisted intraoperative visualization of dental implants. Augmented reality in medicine].

In this paper, a recently developed computer-based dental implant positioning system with an image-to-tissue interface is presented. On a computer monitor or in a head-up display, planned implant positions and the implant drill are graphically superimposed on the patient's anatomy. Electromagnetic 3D sensors track all skull and jaw movements; their signal feedback to the workstation induces permanent real-time updating of the virtual graphics' position. An experimental study and a clinical case demonstrates the concept of the augmented reality environment--the physician can see the operating field and superimposed virtual structures, such as dental implants and surgical instruments, without loosing visual control of the operating field. Therefore, the operation system allows visualization of CT planned implantposition and the implementation of important anatomical structures. The presented method for the first time links preoperatively acquired radiologic data, planned implant location and intraoperative navigation assistance for orthotopic positioning of dental implants.

Computer Graphics↗