Biomedical subjects

T Hüfner

Publications and source records attributed to T Hüfner.

39 records · Page 3Linked to original sources

PubMed1996

[Screw arthrodesis of the ankle joint. Technique and outcome].

In ankle arthrodeses several clinical and biomechanical studies have shown the superiority of the screw technique over external fixation. As a maximum of stability is a major goal, especially for functional after-treatment or in patients with poor bone stock, the arthrodeses technique at Hannover Medical School is performed with four screws. Two parallel anterior/posterior screws are placed from the tibia to the talus, providing anterior stabilization. One screw posteriomedial has a posterior tension-wiring effect and one screw placed through the fibula to the talus acts against rotational and sagittal translation. From May 1975 to May 1995, 225 ankle arthrodeses with internal or external fixation technique were performed. Complications were found in 47% in the external fixation treatment group (n = 44) and in 10% the patients stabilized with the screw technique (n = 181). Fifty of these 225 patients had a follow-up evaluation after an average of 7.4 years (external fixation, n = 22; screw fixation, n = 28). All patients were examined and scored with three different scoring systems: (1) MHH Score, (2) Clinical Rating System according to Kitaoka et al. (1994) and (3) Outcome Questionnaire for evaluating the overall outcome. The results from the questionnaire were compared to the clinical scores. Retrospective analysis revealed a higher rate of complications for arthrodeses performed by external fixation. The overall results of all three different scoring systems showed a trend in favor of the screw-fixation technique without reaching statistical significance (P > 0.05). The results of the Outcome Questionnaire are statistically as valid as the two clinical scoring systems.

Ankle Joint↗

PubMed1996

[The pelvic digital image data bank. Experiences after 18 months in clinical practice].

The simultaneous availability of clinical data and radiographs for orthopedic or traumatology studies is still unsatisfactory. The retrieval of radiological files is especially time-consuming and costly. An existing database holding clinical data for about 2200 consecutive patients after pelvic or acetabular fractures (1972-1995) was supplemented by integration of a commercially available picture database. Data acquisition is performed by a digital photo camera, which is easy to use and provides sufficient resolution (1524 x 1012 pixels). The picture data are optimized but not compressed and, for example, an a.p. pelvic view requires only between 800 KB and 1.5 MB of storage room. Mass storage is performed first on magneto-optical discs and later for permanent storage on CD-ROM. "Clinical" and picture databases are linked by a macro, so the search functions of both databases are available. Thus the clinical data for single patients or group of patients can be analyzed parallel to the corresponding radiographs. By the use of a CD changer, more than 4200 radiographs remain in immediate access. So far more than 3000 radiographs for 350 patients have been acquired. The quality was sufficient for even detailed subclassification and reclassification procedures in over 95% of the cases. Using standard formats and interfaces, the pictures can be either printed in photographic quality or processed as slides for presentation. Using a standard format they have complete access to electronic publishing and mailing. The relatively low price (20,000-30,000 DM) for the complete system and the exclusive use of standard, commercially available hard and software components provide an excellent price/quality relationship and make digital radiograph storage now available for smaller working groups and institutions.

Acetabulum↗

PubMedDate not supplied

Accuracy study of computer-assisted drilling: the effect of bone density, drill bit characteristics, and use of a mechanical guide.

OBJECTIVE: This study was designed to determine the clinical relevant accuracy of CT-based navigation for drilling. DESIGN: Experimental model. SETTING: Laboratory. METHODS: Twelve drills of varying lengths and diameters were tested with 2 different set-ups. Group 1 used free-hand navigated drilling technique with foam blocks equipped with titanium target points. Group 2 (control) used a newly developed 3-dimensional measurement device equipped with titanium target points with a fixed entry for the navigated drill to minimize bending forces. One examiner performed 690 navigated drillings using solely the monitor screen for control in both groups. The difference between the planned and the actual starting and target point (up to 150 mm distance) was measured (mm). STATISTICS: Levene test and a nonpaired t test. Significance level was set as P < 0.05. RESULTS: The core accuracy of the navigation system measured with the 3-dimensional device was 0.5 mm. The mean distance from planned to actual entry points in group 1 was 1.3 (range, 0.6-3.4 mm). The mean distance between planned and actual target point was 3.4 (range, 1.7-5.8 mm). Free-hand navigated drilling showed an increased difference with increased length of the drill bits as well as with increased drilling channel for drill bits 2.5 and 3.2 mm and not for 3.5 and 4.5 mm (P < 0.05). CONCLUSIONS: The core accuracy of the navigation system is high. Compared with the navigated free-hand technique, the results suggest that drill bit deflection interferes directly with the precision. The precision is decreased when using small diameter and longer drill bits.

Bone Density↗