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Biomedical subjects

E Hierholzer

Publications and source records attributed to E Hierholzer.

At least 19 recordsLinked to original sources
PubMed2002

3-D back surface analysis of severe idiopathic scoliosis by rasterstereography: comparison of rasterstereographic and digitized radiometric data.

Rasterstereography has been shown to be a reliable method for three-dimensional surface measurement of idiopathic scoliosis with Cobb angles up to 50 degrees. In this study, 25 patients with severe idiopathic scolioses (Cobb angles 47 degrees-92 degrees) were examined before and after operation (VDS instrumentation). The a.p. radiographs were digitized according to the Drerup method. The similarity of rasterstereographic and radiometric data was quantified by the rms. differences between the rasterstereographic and radiographic curves of lateral deviation and vertebral or surface rotation. The average rms. differences were 5.8 mm for lateral deviation and 4.4 degrees for vertebral and surface rotation, which is about 40% higher than for mild to medium scolioses.

Humans↗
PubMed2001

[Functional rasterstereographic images. A new method for biomechanical analysis of skeletal geometry].

Video rasterstereography has been developed for optical back shape measurement and for biomechanical analysis of spinal and pelvic geometry. Analysis of one single measurement permits 3-dimensional reconstruction of the back surface and calculation of shape parameters including pelvis tilt and torsion. In addition, estimates of the lateral deviation of the spinal midline and of vertebral rotation are provided. Its extended analytic potential makes rasterstereography a very appropriate tool for functional examinations. The term "functional examinations" refers in this context to biomechanical analysis of functional movements of the spine and pelvis caused by quasi-continuous changes of posture, if these can be observed as changes in back shape. Two examples are given to illustrate the aim and performance of functional examinations. Shoe elevation is used to correct leg-length discrepancy and is therefore prescribed for prevention and correction of scoliosis produced by pelvic obliquity. In a previous study it was shown that simulating leg-length discrepancy by raising a foot causes the pelvis to perform a torsional movement about the transverse axis. In effect, this movement reduces to some extent the effect of shoe elevation; thus a larger elevation might give better results. 42 scoliotic patients underwent functional examination. Leg-length discrepancies were simulated in 7 steps, and the resulting back shape was analysed by rasterstereography. The measurements were corrected for pelvic torsion. This method provided satisfactory correspondence with radiographically recorded leg-length discrepancies, i.e. 0.7 mm +/- 11.2 mm. One specific advantage of this procedure is that it covers aspects relating to spinal lateral deviation and vertebral rotation. It is concluded, however, that the 7 measurements used are hardly sufficient for this application and that better results are therefore to be expected from extended series. Kyphosis and lordosis clearly depend on posture. This is confirmed in a functional examination where these angles are measured under voluntary changes of posture. In forward bending, the trunk straightens and kyphosis and lordosis angles decrease. The reverse case applies to backward bending. If this effect is taken into quantitative consideration, an improved accuracy of measurements is obtained by reference to a standardised, mathematically defined posture. The resulting rms-error of kyphosis/lordosis measurement is then reduced from 3.10 degrees/2.95 degrees to 1.65 degrees/1.40 degrees. These figures open up new applications in the follow-up of kyphotic and lordotic deformities.

Biomechanical Phenomena↗
PubMed1996

Assessment of scoliotic deformity from back shape asymmetry using an improved mathematical model.

OBJECTIVE: The objective of the study was to improve with respect to accuracy and smoothness the three-dimensional model of the spinal midline which has been calculated from rasterstereographic back surface data. DESIGN: A new mathematical model using frequency-modulated sine curves has been applied to existing rasterstereographic and radiographic data in an in vivo study. BACKGROUND: Analysis of back shape (measured by rasterstereography) enables a three-dimensional model of the spinal midline to be calculated. The model is based on the so-called symmetry line which coincides approximately with the line of the spinous processes. In addition the surface rotation on the symmetry line is taken as an estimate for vertebral axial rotation in scoliosis. METHODS: Four hundred and seventy-eight pairs of radiographs and rasterstereographs of scoliotic patients have been evaluated and compared using the new model. The radiographs were digitized manually, delivering curves of lateral deviation and vertebral rotation. Analysis of back shape from the rasterstereographs delivers a three-dimensional model of the spinal midline, the frontal projection of which is to be compared with the radiographic curve. Likewise, vertebral rotation and surface rotation are compared. RESULTS: The use of frequency-modulated sine curves improved the results as compared to the existing procedure with respect to prediction accuracy of lateral deviation (typically from sigma(x) = 4.6 mm to sigma(x) = 4.0 mm, P < 10(-10)). The prediction of axial rotation was not significantly improved (sigma(varrho) thick approximate 3.8 degrees ). In addition, the smoothness of the curves is considerably improved. The prediction accuracy proved to be independent of the scoliosis type as represented by apex height (r = -0.09 ellipsis + 0.03). CONCLUSION: The use of frequency-modulated sine curves improves significantly the accuracy and smoothness of the spinal model curves.

Journal Article↗
PubMed1992

Evaluation of frontal radiographs of scoliotic spines--Part II. Relations between lateral deviation, lateral tilt and axial rotation of vertebrae.

The shape of scoliotic spines as measured from frontal radiographs (see Part I of this paper) is analysed with respect to interrelations between lateral deviation, lateral tilt and axial rotation of the vertebrae. These parameters are represented by sinusoidal functions of the longitudinal coordinate. The interrelations can, therefore, be expressed in terms of amplitude and phase relations. Two additional functions--'spinal tilt' and (local) curvature--are calculated from the first and second derivatives of lateral deviation. The method has been applied to three patient groups with different aetiology: 113 patients with idiopathic scoliosis (478 radiographs, partially follow-up examinations), 23 patients with scoliosis secondary to Wilms' tumour irradiation and 18 patients with scoliosis secondary to poliomyelitis. The amplitude and phase relations of all functions reveal a characteristic pattern which is apparently independent of the specific aetiology. The results show that the available biomechanic explanations of coupling of vertebral motions are questionable.

Adolescent↗
PubMed1992

Evaluation of frontal radiographs of scoliotic spines--Part I. Measurement of position and orientation of vertebrae and assessment of clinical shape parameters.

A new method largely exploiting the shape information which may be obtained from frontal radiographs of scoliotic patients is presented. For a complete description of spinal deformity, six position parameters are needed for each vertebra. From a strictly mathematical point of view, none of them can be determined from a single standard radiograph. However, the four most important parameters can be measured if some reasonable assumptions are made. For a better interpretation, three of these parameters (lateral coordinate x, lateral tilt alpha and axial rotation rho) are plotted as a function of the fourth parameter, the longitudinal coordinate y. These functions may well be approximated by sinusoidal curves (or possibly by Fourier series). The data smoothing implied by this procedure improves the reliability of the data. The method has been tested with 478 radiographs of 113 patients (Cobb angles up to 52 degrees). The results are compared with scoliosis parameters which have been determined according to the conventional clinical rules. A particular advantage of approximation by a sinusoidal function lies in the direct relation of the curve parameters to common scoliosis parameters. Moreover, a mathematical analysis of the interrelations between different parameters--for example, between lateral deviation and axial rotation--is possible in this case.

Adolescent↗
PubMed1988

Age-associated T-lymphocyte activation through mitogens in patients with multiple sclerosis and blood donors.

In 128 patients with multiple sclerosis (MS) and 204 blood donors (control persons) the in vitro activation of 'Ficoll-purified' peripheral blood T lymphocytes was measured using the 3H-thymidine incorporation rate without (spontaneous proliferation) and with mitogen addition (concanavalin A, phytohemagglutinin). Mitogen responsiveness in control persons and MS patients decreased with age, reflecting a T-lymphocyte inherent mechanism for the diminution of responsiveness. The MS patients, ranging in age between 20 and 30 years, showed decreased mitogen responsiveness and a tendency to increased spontaneous proliferation compared to the control persons. These results could be an expression of a viral infection.

Adolescent↗
PubMed1987

Automatic localization of anatomical landmarks on the back surface and construction of a body-fixed coordinate system.

A method for automatic measurement of anatomical landmarks on the back surface is presented. The landmarks correspond to the verteba prominens, the dimples of the posterior superior iliac spines and the sacrum point (beginning of rima ani), which are characterized by distinct surface curvature. The surface curvatures are calculated from rasterstereographic surface measurements. The procedure of isolating a region of interest for each landmark (surface segmentation) and the calculation of the landmark coordinates are described in detail. The accuracy of landmark localization was tested with serial rasterstereographs of 28 patients (with moderate idiopathic scoliosis). From the results the intrinsic accuracy of the method is estimated to be little more than 1 mm (depending on the sampling density of the surface measurement). Therefore, the landmarks may well be used for the objective definition of a body-fixed reference coordinate system. The accuracy is, however, dependent on the specific landmark and a minor influence of posture variations is observed.

Back↗
PubMed1987

Movement of the human pelvis and displacement of related anatomical landmarks on the body surface.

Anatomical landmarks on the body surface can be measured with high accuracy by using rasterstereography and surface curvature analysis. The present study shows that the lumbar dimples can be localized with a statistical error of about 1 mm. It is generally assumed that the dimples are in close relation to the pelvis (in particular to the PSISs) and may thus be taken as indicators for pelvis movements. By introducing an artificial pelvis tilt of up to +/- 10 degrees this relation was examined. In fact, a nearly perfect correlation (r approximately equal to 0.99) between landmark and pelvis movements was observed. Asymmetries of pelvis motion due to scoliotic deformity were not observed. There was, however, a systematic lag of the dimple movements, resulting in a displacement of the dimples of up to +/- 1.5 mm relative to the pelvis (for +/- 10 degrees pelvis tilt). Either a soft tissue effect or a torsion of the pelvis may be responsible for this behaviour. The theory of pelvis torsion is confirmed by the fact that the orientation of the back surface at the locus of the dimples reveals a corresponding torsion of similar magnitude and sign. A torsion angle of about +/- 1.5 degrees in either sacro-iliac joint is sufficient to explain the observed dimple lag and the surface torsion. An independent measurement (e.g. using roentgenphotogrammetry) would be desirable to further validate this theory. According to our measurements the dimples of the PSISs cannot be taken as exact indicators for orientation and movement of the pelvis.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1986

Rasterstereography in the measurement and postoperative follow-up of anterior chest wall deformities.

Rasterstereography is a contact-free photogrammetric method for the measurement of body surfaces. As such it is particularly suited for the objective documentation of anterior chest wall deformities and the results of surgery. An example of its application and first results are presented. The possibilities of a thorough data analysis with regard to diagnosis and therapy control are outlined.

Adolescent↗
PubMed1985

Objective determination of anatomical landmarks on the body surface: measurement of the vertebra prominens from surface curvature.

A method for the objective detection of anatomical landmarks on the body surface is presented. The method is based on an analysis of local surface shape which is described in terms of surface curvature. The curvature is calculated from the surface coordinates as measured by optical methods such as moiré topography or rasterstereography. As an example, the location of the vertebra prominens is determined. In order to assess the accuracy and reliability of the procedure, the results are compared with the conventional method of palpation and marking. The measured deviations are in the order of a few millimeters.

Anthropometry↗
PubMed1982

[Bone marrow transplantation for aplastic anaemia and acute leukaemia (author's transl)].

Twenty-six bone marrow transplantations were performed at the West Germany Tumour Centre at Essen between December 1975 and December 1981. Three patients had aplastic anaemia, 23 acute leukaemia. Of the leukaemia patients 13 had a recurrence and ten were in full remission at the time of the transplantation. Two of the patients with a recurrence received deep-frozen autologous marrow from the remission phase. One patient with aplastic anaemia had an identical twin as donour, while all other patients received allogeneic marrow from histocompatible family members. Eleven patients are still alive, all three of those with aplastic anaemia, one of those with leukaemia in a recurrence, and seven of those with acute leukaemia in full remission. Two of the survivors have a chronic graft-host reaction, but the others are symptom-free, after an observation period of up to four years. Main causes of death were leukemic recurrence (6), infection (5), and graft-host reaction (2). It would seem that at present bone marrow transplantation offers the best chance of a cure for severe aplastic anaemic and acute leukaemia in adults, but only if transplantation is undertaken early and not in the end-stage of the disease.

Acute Disease↗