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P Mayrhofer

Publications and source records attributed to P Mayrhofer.

16 recordsLinked to original sources
PubMed2001

Evaluation of accuracy and precision of bone markers for the measurement of migration of hip prostheses. A comparison of conventional measurements.

Our aim was to determine whether tantalum m arkers improved the accuracy and/or precision of methods for the measurement of migration in total hip replacement based on conventional measurements without mathematical correction of the data, and with Ein Bild Roentgen Analyse - Femoral Component Analysis (EBRA-FCA) which allows a computerised correction. Three observers independently analysed 13 series of roentgen-stereophotogrammetric-analysis (RSA)-compatible radiographs (88). Data were obtained from conventional measurements, EBRA-FCA and the RSA method and all the results were compared with the RSA data. Radiological evaluation was also used to quantify in how many radiographs the intraosseous position of the bone markers had been simulated. The results showed that tantalum markers improve reliability whereas they do not affect accuracy for conventional measurements and for EBRA-FCA. Because of the danger of third-body wear their implantation should be avoided unless they are an integral part of the method.

Computer Simulation↗
PubMed1999

Extended recombinant bacterial ghost system.

Controlled expression of cloned PhiX174 gene E in Gram-negative bacteria results in lysis of the bacteria by formation of an E-specific transmembrane tunnel structure built through the cell envelope complex. Bacterial ghosts from a variety of bacteria are used as non-living candidate vaccines. In the recombinant ghost system, foreign proteins are attached on the inside of the inner membrane as fusions with specific anchor sequences. Ghosts have a sealed periplasmic space and the export of proteins into this space vastly extends the capacity of ghosts or recombinant ghosts to function as carriers of foreign antigens. In addition, S-layer proteins forming shell-like self assembly structures can be expressed in candidate vaccine strains prior to E-mediated lysis. Such recombinant S-layer proteins carrying foreign epitopes further extend the possibilities of ghosts as carriers of foreign epitopes. As ghosts have inherent adjuvant properties, they can be used as adjuvants in combination with subunit vaccines. Subunits or other ligands can also be coupled to matrixes like dextran which are used to fill the internal lumen of ghosts. Oral, aerogenic or parenteral immunization of experimental animals with recombinant ghosts induced specific humoral and cellular immune responses against bacterial and target components including protective mucosal immunity. The most relevant advantage of recombinant bacterial ghosts as immunogens is that no inactivation procedures that denature relevant immunogenic determinants are employed in this production. This fact explains the superior quality of ghosts when compared to other inactivated vaccines. The endotoxic component of the outer membrane does not limit the use of ghosts as vaccine candidates but triggers the release of several potent immunoregulatory cytokines. As carriers, there is no limitation in the size of foreign antigens that can be inserted in the membrane and the capacity of all spaces including the membranes, peri-plasma and internal lumen of the ghosts can be fully utilized. This extended recombinant ghost system represents a new strategy for adjuvant free combination vaccines.

Adjuvants, Immunologic↗
PubMed1999

Accuracy of EBRA-FCA in the measurement of migration of femoral components of total hip replacement. Einzel-Bild-Röntgen-Analyse-femoral component analysis.

Several methods of measuring the migration of the femoral component after total hip replacement have been described, but they use different reference lines, and have differing accuracies, some unproven. Statistical comparison of different studies is rarely possible. We report a study of the EBRA-FCA method (femoral component analysis using Einzel-Bild-Röntgen-Analyse) to determine its accuracy using three independent assessments, including a direct comparison with the results of roentgen stereophotogrammetric analysis (RSA). The accuracy of EBRA-FCA was better than +/- 1.5 mm (95% percentile) with a Cronbach's coefficient alpha for interobserver reliability of 0.84; a very good result. The method had a specificity of 100% and a sensitivity of 78% compared with RSA for the detection of migration of over 1 mm. This is accurate enough to assess the stability of a prosthesis within a relatively limited period. The best reference line for downward migration is between the greater trochanter and the shoulder of the stem, as confirmed by two experimental analyses and a computer-assisted design.

Acetabulum↗
PubMed1998

Mutations in cell division proteins FtsZ and FtsA inhibit phiX174 protein-E-mediated lysis of Escherichia coli.

Electron microscopic studies emphasized that the protein-E-specific transmembrane tunnel structure, which permeabilizes Escherichia coli, is not randomly distributed over the cell envelope but is restricted to areas of potential division sites. These sites were located predominantly in the middle of the cell, but approximately one-third of these structures are found at the polar sites. Therefore, E. coli mutant strains with defects in cell division components were tested for their sensitivity to protein-E-mediated lysis. The ftsZ84 and the ftsA12 cell division mutant strains of E. coli were tolerant to protein-E-mediated lysis, whereas the ftsA3 mutant strain was lysed by protein E under conditions nonpermissive for division. The protein-E-tolerant phenotype of ftsZ84 and ftsA12 and the lysis-sensitive phenotype of other components of the septosome (e.g., ftsA3, ftsQ, and ftsI) suggest that initiation of cell division - rather than specific functions of cell division - plays an essential role in protein-E-mediated lysis. SulA-overproducing cells had a lysis-positive phenotype, the ring structure - but not the GTPase function - of FtsZ was impaired.

Animals↗
PubMed1998

[Measurement of migration of acetabular components in cementless hip replacement].

PURPOSE: Migration measurements of acetabular components using a special computer aided method (EBRA = abbreviation for the German term "Ein-Bild-Röntgenanalyse") were performed to evaluate early results of the implants and predict aseptic loosening. METHODS: Standard ap-radiographs of the pelvis were marked, specific points were digitised. Simulating the spatial situation the programme computes longitudinal and vertical migration of the cup. 74 acetabular components in 71 patients could be studied by migration measurements. RESULTS: 14 patients showed migration of more than 1 mm, which is the confidence limit of this method. Each of these patients showed diverse reasons for the migration, i.e. osteoporosis of the acetabular bone stock or problems concerning the surgical technique which means malposition of the cup or insufficient reaming of the bone. There were some patients with severe congenital dysplasia of the hip and in some cases the inclination angle of the cup was too great. CONCLUSION: The technique applied for measuring migration of acetabular components can be useful for evaluating early instability of the implant and can be helpful in detecting problems concerning the surgical technique.

Acetabulum↗
PubMed1997

[Single-image roentgen analysis for the measurement of hip endoprosthesis migration].

A method to determine migration of hip endoprostheses is described. Migration is measured by means of standard AP radiographs and therefore can also be evaluated in retrospective studies. Measurement is conducted in X-ray studies displayed on a computer screen. Enhancement of bony structures by application of filters is available. The developed software can be used with common commercially available computers and X-ray scanners, and does not require special hardware. Several methods to determine accuracy are described. The accuracy of the described method is about 1 mm (95% confidence limit), which compares favourably with other methods, but is less accurate than roentgen stereophotogrammetry. For other methods, accuracy was not determined adequately. Two years after implantation, revision within the first 10 years of follow-up can be predicted with a sensitivity and specificity of more than 80%.

Acetabulum↗
PubMed1996

Early migration predicts late aseptic failure of hip sockets.

We report a prospective, stratified study of 60 PCA-cups and 60 RM-polyethylene cups which have been followed for a median time of 90 months, with annual radiography. The radiological migration of cups was measured by the computer-assisted EBRA method. A number of threshold migration rates from 1 mm in the first year to 1 mm in five years have been assessed and related to clinically determined revision rates. A total of 28 cups showed a total migration of 1 mm or more within the first two years; 13 of these cups have required revision and been exchanged. The survival curves of cups which had previously shown early migration were considerably different from those without early migration. For cups with a migration of less than 1 mm within the first two years the mean survival at 96 months was 0.96 +/- 0.02; for migrating cups, it was 0.63 +/- 0.11 (log-rank test, p=0.0001; chi-square value=39.4). Early migration is a good predictor for late loosening of hip sockets.

Aged↗
PubMed1995

EBRA: a method to measure migration of acetabular components.

In orthopedics there is a demand for determining migration of hip sockets by evaluation of standard radiographs. In this case problems are caused mainly by changing pelvis positions on the X-ray table at successive exposures. A method (EBRA) is described that evaluates standard AP radiographs without requiring additional means at exposure (e.g. ball markers). Simulating the spatial situation it computes parameters of longitudinal and transverse migration of prosthetic cup and femoral head. A comparability algorithm using a grid of transverse and longitudinal tangents of the pelvis contour divides serial radiographs into sets of comparable ones. Comparability of serial radiographs takes place if the distances of corresponding grid lines do not transcend a given limit L. Migration is measured only between comparable radiographs. Different studies are described concerning the interdependence of pelvis rotations and changes of the grid lines, the degree of pelvis rotations appearing in practice, the choice of the limit L, the properties of the comparability algorithm and the accuracy of EBRA. The 95% confidence limits for EBRA results are 1.0 mm for longitudinal and 0.8 mm for transverse migration.

Arthrography↗
PubMed1994

A prospective study of the migration of two acetabular components. PCA versus RM cups.

Fifty-nine PCA cups and 61 hydroxyapatite-coated RM cups were included in a prospective randomised study with a mean follow up of 5.2 years. Clinical evaluation revealed better results with the RM cup. Radiological criteria of loosening could be applied only with considerable restrictions as different parameters were assessed: progressively loosened beads in PCA cups and faded contour in RM cups. Migration was measured by a computer assisted method (EBRA). PCA cups showed significantly more longitudinal migration 2 years after operation and subsequently. High migration values correlated with a limp. Loosening as defined by migration was of clinical relevance, could be measured early and predicted the survival rate.

Activities of Daily Living↗
PubMed1975

[Idiopathic, muscular, hypertrophic, sub-aortic stenosis].

The authors have seen 14 cases of idiopathic, hypertrophic, subaortic stenosis and they describe the pathology, the clinical and radiological diagnosis and the differential diagnosis of this condition. Their own findings are compared with those in the literature and substantial agreement is found. Some uncharacteristic clinical and radiological findings are associated with typical pressure curves in the left ventricle and marked abnormalities in the laevocardiogram. Variations in ventricular filling due to the difference in severity of the disease are discussed. The importance of a correct diagnosis is stressed, since the use of inotropic substance is this condition is contra-indicated.

Adolescent↗
PubMed1975

[Pulmonary perfusion, ventilation, and gas exchange during modified cobalt-60 teletherapy of operated on breast carcinomas].

Post ablationem mammae, 22 patients were exposed to a modified telecobalt-irradiation because of mammary carcinoma. (Tangential pendulum irradiation of the thoracic wall with deflection of the central beam off the pendulum axis, parasternal irradiation with pendulum fields, irradiation of the supraclavicular and axillar area with deflection of the central beam to lateral and cranial directions.) During radiation therapy and up to six months after its termination, periodical pulmonary function tests were accomplished, consisting in a radiogram of the thorax, in spirometric check-up and blood gas analysis, and in an examination of pulmonary perfusion and ventilation using radionuclide techniques. In one patient with metastases to the ribs, the spirographic and nulear-medical ventilatory results changed for the worse in the course of time, whereas the other 21 patients did not show any significantly abnormal alterations at follow-up examinations.

Adult↗
PubMedDate not supplied

[Analysis of migration of screwed acetabular components following revision arthroplasty of the hip joint. Results of single-image roentgen analysis].

Out of 57 revised acetabular components, which were regularly checked, 47 had been replaced by a cemented Müller's acetabular reinforcement ring resp. a cementless Müller's Sl-shell with flange. Both types of cups are anchored in the acetabular roof with cancellous bone screws (tab. 1). 42 cases with radiograph series permitted a detailed analysis with the EBRA-method, a computer aided method for the evaluation of acetabular spatial migration based on standard radiographs of the pelvis. The clinical results were very satisfying (tab. 6). The screwed acetabular components migrated little, although, some essential displacements of the center of rotation (in relation to the anatomical position) had to be accepted. As was recognizable with today's inaccurate methods of measuring the center of the head, the displacement too far towards cranial influenced the migration tendency less than an excessive lateralisation. Especially satisfying is the fact, that no increased migration was observed after reconstruction bone grafting of severe acetabular defects, provided that at least a partly direct contact between the acetabular component and the original bone stock was obtained. For the first time EBRA shall be introduced here as a method which shows the migration and the spatial inclination of the acetabular cup in a vector chart.

Acetabulum↗