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Biomedical subjects

R Putz

Publications and source records attributed to R Putz.

At least 91 records · Page 5Linked to original sources
PubMed1995

[Anatomy and biomechanics of the knee joint].

The morphology of the components of the knee joint is reviewed, with particular reference to the ever-widening range of technical representation offered by modern imaging procedures. The morphological parameters of cartilage thickness, thickness of the subchondral zone of mineralization and subchondral X-ray density (assessed by CT osteoabsorptiometry) are depicted, and the various parts of the capsular ligamentous apparatus are described, with particular attention to the cruciate ligaments and menisci. The periarticular topography is also dealt with briefly. An attempt is made to elucidate with diagrams the essential basis of the static stress acting on the joint. The kinematics and dynamics are examined with particular reference to new theories about control of the position of the joint as a result of sensory functioning of the cruciate ligaments.

Anterior Cruciate Ligament↗
PubMed1995

[Knee joint cartilage in magnetic resonance tomography. MR chondrovolumetry (MR-CVM) using fat-suppressed FLASH 3D sequence].

UNLABELLED: The objective of this study was to optimize the demonstration of articular cartilage with magnetic resonance tomography (MRT) and to assess its accuracy in determining the articular cartilage volume of the knee joint. METHODS: A fat-suppressed FLASH-3D sequence was optimized on healthy volunteers. A fresh cardaveric knee joint was removed from a 82-year-old man and immediately imaged without being frozen or fixed. MRT was carried out at 1.5 T and 25 mT/m (Vision, Siemens, Erlangen, Germany) with a conventional CP knee coil. Sagittal and transverse sections were acquired perpendicular to the articular surfaces, and then, parallel to these imaging planes, anatomical sections were obtained with a diamond band saw. The volumes of the patellar, tibial and femoral cartilages were determined from both the images and the sections, using an image analysing system. RESULTS: Signal intensities and contrast-to-noise ratios depend on the parameters used. The highest contrast between the cartilage and the periarticular tissues was obtained at a flip angle of 30 degrees (TR = 60 ms, TE = 11 ms). However, a flip angle of 60 degrees was judged to provide optimal subjective image quality. Using these parameters, the deviations between the radiological and the anatomical cartilage volumes were -4.7% in the patella, -3.1% in the tibial plateau and -4.2% in the femur. CONCLUSIONS: The volumes of the knee-joint cartilages may be accurately determined with MRT if an appropriate pulse sequence is chosen. From a clinical point of view the differences between MR images and anatomical sections can be considered negligible. These differences may be explained on the basis that MRT delineates uncalcified cartilage only and that the calcified layer is demonstrated as part of the subchondral bone plate. However, close correlation of the thicknesses of the uncalcified and the calcified layer has been reported in the literature, so the relative distribution of articular cartilage should be accurately reflected in MR images.

Aged↗
PubMed1994

The influence of geometry on the stress distribution in joints--a finite element analysis.

The incongruity of human joints is a phenomenon which has long been recognized, and recent CT-osteoabsorptiometric findings suggest that this incongruity influences the distribution of stress in joints during their normal physiological use. The finite element method (FEM) was therefore applied to five different geometric configurations consistent with the anatomy of articular surfaces, and a program with variable contact areas (Marc) was used to calculate the stress distribution for loads of 100 to 6,900 N. The assumption of congruity between head and socket results in a "bell-shaped" distribution of stress with a maximum value of 61.5 N/mm2 in the depths of the socket, decreasing towards zero at its edges. In the model with a flatter socket the von Mises stresses are higher (max. 101.3 N/mm2); with a deeper socket, lower (max. 53.0 N/mm2). If the diameter of the head is greater, the stresses build up from the periphery of the socket and move towards its depths as the load increases. The combination of an oversized head and a deeper socket results in the most satisfactory stress distribution (max. 43.2 N/mm2). These results extend previous photoelastic findings with incongruous joint surfaces. The calculated mechanical conditions show a relationship to the location of osteoarthritic changes, and are reflected by the distribution pattern of subchondral bone density. A more satisfactory stress distribution is found with functionally advantageous, incongruous joint surfaces (oversized head and deepened socket) than in the congruous joint, and a better nutritive situation for the articular cartilage seems likely.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1994

The morphology of articular cartilage assessed by magnetic resonance imaging (MRI). Reproducibility and anatomical correlation.

Quantitative assessment of cartilage volume and thickness in a formalin-alcohol fixed specimen of a human patella was conducted with magnetic resonance imaging (MRI), as it is still unclear whether the morphology of normal and damaged cartilage can be accurately demonstrated with this technique. MR imaging was carried out at 1.0 T (section thickness 2 mm, in-plane-resolution 0.39-0.58 mm) with the following pulse sequences: 1) T1-weighted spin-echo, 2) 3D-MPRAGE, 3) 3D-FISP, 4) 3D-MTC-FISP, 5) 3D-DESS, 6) 3D-FLASH. Following imaging, the patella was sectioned perpendicular to the articular surface at intervals of 2 mm with a diamond band-saw. The volume of its cartilage was determined from the anatomical sections and the MR images, using a Vidas IPS 10 image analysing system (Kontron). Measurements were carried out with and without the low-signal layer in the transitional zone between the articular cartilage and the subchondral bone. If the low-signal layer was included, the volume was overestimated with MRI by 16 to 19%. Without the low-signal layer the volumes were less than those determined from the anatomical sections: T1-SE-18.2%, MPRAGE -22.6%, FISP -17.1%, MTC-FISP -9.5%, DESS -9.3% and FLASH -6.1%. The coefficient of variation for a 6-fold determination of the volume amounted to between 6.2% (T1-SE) and 2.6% (FLASH). The FLASH sequence allowed the most valid and reproducible assessment of the cartilage morphology. The remaining difference from the real volume of the cartilage may be due to the fact that the calcified zone of the cartilage is not delineated by MRI.

Aged↗
PubMed1994

Quantitative morphology of the subchondral plate of the tibial plateau.

The object of the present investigation was to measure the thickness distribution of the subchondral plate of the tibial plateau. The data were obtained by computerised image analysis of serial sections. The measured values revealed a marked difference in the thickness between the various regions of the joint surface. Thinner zones (100-300 microns) are found in the peripheral region near the margin of the tibial plateau. Thickness maxima (up to 1500 microns and more) are to be seen at the centres of the joint surfaces. The relationship between the thickness distribution of the subchondral plate and information about the stress distribution of this particular joint surface support the conclusion that the morphology of the subchondral plate of the tibial plateau is determined by the function of the joint.

Cartilage, Articular↗
PubMed1994

[Change in subchondral mineralization after reconstruction of the anterior cruciate ligament of the sheep].

The cruciate ligaments are generally regarded as regulators of the joint kinematics, but also increasingly as a "Sensory organ" regulating the periarticular musculature, which influences the position of the contact surfaces and the direction and magnitude of the resultant forces. Indirectly, therefore, they influence the long-term stress distribution, which is itself reflected in the distribution of the subchondral mineralisation. An experimental investigation was therefore undertaken to see whether, in terms of this distribution, the distribution of the stress alters postoperatively, since this could be regarded as an early cause of degenerative change. We examined the distribution of the subchondral mineralisation of six tibiae from six adult Merino sheep 1 year after anterior cruciate ligament reconstruction with patellar tendon. The contralateral tibia we used as controls. Maximum subchondral mineralisation of both the medial and the lateral joint surfaces in all the control joints was found to be central. In the treated knees, however, the medial joint surface maxima were found to have been displaced towards the dorsomedial edge of the surface in every case. If the density pattern on the control side is accepted as the expression of a normal stress distribution, the distribution patterns on the treated side must indicate a pathologic distribution of stress. Reconstruction of the anterior cruciate ligament is therefore--at least in the animal model--not able to prevent the development of a pathologic stress distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Stress on the ligamentum transversum acetabuli in physiological stress on the hip joint].

We investigated the strain on the transverse acetabular ligament (TAL) and the labrum close to the anterior and posterior horn of the lunate surface using Omega strain gauges [5] while increasing loads were applied to the hip joint. Two fresh hip joint specimens and four specimens fixed in 3.7% formalin were examined. The two components of the joint were disarticulated and soaked in physiological saline and then placed in a material-testing machine (Zwick) in the neutral position of the joint. The strain on the TAL and the labrum was measured at loads of 10 N, 350 N, 700 N, 1050 N, 1400 N, 2100 N and 2800 N. Finally, the contact areas were measured at a load of 350 N using a polyether casting method. Depending on load, the length of the TAL increased by up to about 3.2% at a load of 2800 N, but the length of the labrum increased by only 0.5% at the same load. Following rotation of the femoral head to positions corresponding to 15 degrees extension and 15 degrees and 30 degrees flexion, only slight differences of about 0.2% for the TAL and even less for the labrum were measured. The contact areas are all located in the anterior and posterior horn of the lunate surface. The measured changes in strain on the TAL confirm the widening of the acetabular notch and a subsequent stretching of the TAL as the load on the hip joint increases.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetabulum↗
PubMed1994

Stress distribution in the trochlear notch. A model of bicentric load transmission through joints.

In 16 cadaver humeroulnar joints, the distribution of subchondral mineralisation was assessed by CT osteoabsorptiometry and the position and size of the contact areas by polyether casting under loads of 10 N to 1280 N. Ulnas with separate olecranon and coronoid cartilaginous surfaces showed matching bicentric patterns of mineralisation. Under small loads there were separate contact areas on the olecranon and coronoid surfaces; these areas merged centrally as the load increased. They occupied as little as 9% of the total articular surface at 10 N and up to 73% at 1280 N. Ulnas with continuous cartilaginous surfaces also had density patterns with two maxima but those were less prominent, and in these specimens the separate contact areas merged at lower loads. The findings indicate a physiological incongruity of the articular surfaces which may serve to optimise the distribution of stress.

Aged↗
PubMed1993

Physiological incongruity of the humero-ulnar joint: a functional principle of optimized stress distribution acting upon articulating surfaces?

Investigations into the distribution of subchondral bone density in the human elbow have suggested that the geometry of the trochlear notch deviates from a perfect fit with the trochlea, and that the load is transmitted ventrally and dorsally rather than through the centre of the humero-ulnar joint. We therefore decided to make a quantitative assessment of the degree of incongruity between the two components in 15 human specimens (age distribution 60 to 93 years) with different types of joint surface. Polyether casts of the joint cavity were prepared under loads of 10, 40, 160 and 640 N. The thickness of the casts was then measured at 50 predetermined points, and an area distribution of the width of the joint space represented in a two-dimensional template of the trochlear notch. The reproducibility of this procedure was tested by image analysis. At a load of 10 N, only a narrow space was present ventrally and dorsally in the joint, but in the depths of the trochlear notch a width of 0.5 to 1 mm was recorded in the centre, and up to 3 mm as its medial and lateral edges. Specimens with continuous articular cartilage showed a lower degree of incongruity than those with a divided articular surface. As the load was increased to 640 N, however, the original incongruity between the articular surfaces disappeared almost completely.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Cartilage degeneration in the human patellae and its relationship to the mineralisation of the underlying bone: a key to the understanding of chondromalacia patellae and femoropatellar arthrosis?

According to the literature subchondral bone plays a significant role in the transmission of load through joints and in the pathogenesis of osteoarthrosis. Therefore the degeneration of the articular cartilage was investigated in the patellae from 30 dissecting-room specimens and of 20 patients, previously submitted to arthroscopy, and subchondral mineralisation of their underlying bone was at the same time assessed by means of CT osteoabsorptiometry. Lateral cartilage lesions were localised over highly mineralised subchondral bone; these appear to be due to long-term stress. They were mainly found in the older specimens and showed a high rate of progression with increasing age. Medially localised cartilage lesions, on the other hand, were situated in a transitional region between moderate and slight subchondral mineralisation; they may be caused by infrequent stress peaks and by shear stress in the articular cartilage, the very medial part of the joint being deprived of mechanical stimulation for much of the time. These lesions were to be found predominantly in the younger specimens and showed little progress with advancing age. Patients with lateral cartilage degeneration exhibited higher, patients with medial chondromalacia patellae lower mineralisation than normals. Their density patterns therefore indicate a different mechanical pathogenesis of the cartilage lesions in the lateral and medial facet. It could be shown that CT osteoabsorptiometry allows an assessment of the mechanical situation, present in individual femoro-patellar joints, and that this situation is highly relevant for the pathogenesis of patellar cartilage degeneration.

Absorptiometry, Photon↗
PubMed1993

[Function-related morphology of the intervertebral disks].

The intervertebral discs contribute to shock absorption only to a limited degree; they are important however, for efficient orientation of axial pressure transmission to the entire surface of the contiguous vertebral bodies. So long as there is sufficient distension of the nuclei pulposi, the annuli fibrosi (particularly those of the lumbar vertebral column) play a part in the ligamentous control of the motion segment. From the 20th year of life onwards the discs are completely avascular, although they show high metabolic turnover. Their water content decreases with advancing age. As early as the first decade of life, beginning in the lateral, uncovertebral zones, clefts appear in the cervical intervertebral discs. These clefts frequently progress to tears involving the whole of the intervertebral disc.

Adolescent↗
PubMed1993

[Areas of contact in human humero-ulnar joints as a function of pressure, their connection through subchondral mineralization and joint surface morphology of the incisura trochlearis].

Evaluation of the stress distribution in joints can be obtained directly from contact areas and pressure forces, and also indirectly from the functional adaptation of the connective tissues. Therefore 8 human humero-ulnar joints, fixed in formalin, were examined for size and position of contact areas (polyether casting/Vidas image analyser) and their dependence upon the joint forces (Zwick material testing machine). The distribution of subchondral mineralisation was assessed, using CT osteoabsorptiometry. Depending on the joint force, the contact areas increase from about 10% of the total surface (20 N) to approximately 60% (1280 N). With weak forces they are localised ventrally and dorsally in the joint, with more powerful forces they run together centrally. With a divided articular surface they join at about 160-640 N, with a continuous surface, at about 40-80 N. Divided joint surfaces show a bicentric mineralisation pattern of the subchondral bone with ventral and dorsal maxima. Continuous surfaces, on the other hand, usually show central maxima. Both the mineralisation pattern and the position of the contact areas suggest a physiological incongruity of the humero-ulnar joint surfaces, which vanishes with increasing pressure due to viscoelastic deformation of articular cartilage and subchondral bone. More marked incongruity is postulated for the divided surfaces than for the others. The consequent peripheral transmission of pressure seems to involve a functional principle, which, present in several human joints, leads to both optimal distribution of the stress and better nutrition of the articular cartilage.

Aged↗
PubMed1993

[Mechanical stress and subchondral mineralization of the human elbow joint. A CT-osteoabsorptiometric study].

We examined 21 elbow joints (age 60-97 years; mean 79 years) that had been fixed in 3.7% formalin. The articular surface of the trochlear notch was completely divided in 10 cases, undivided in 5, and only partially divided in the medial aspect of the joint surface in 6. Subchondral mineralisation was investigated by means of CT osteoabsorptiometry (Müller-Gerbl et al. 1989) on sections 2 mm apart with a Siemens Somatom SF CT scanner. Two-dimensional reconstruction of the surface distribution was achieved by dividing it into 8 Hounsfield ranges (< 300 HU > 900 HU) and using a joint template. Higher values for the subchondral mineralisation are usually found in the distal and medial parts of the joint, indicating greater stress there. Whereas the radial head and the capitulum show a distribution pattern with mineralisation falling off more or less concentrically from the centre outwards, the trochlea and trochlear notch are often poorly mineralised in the centre. There is one maximum on the proximal and one on the distal aspect of the joint surface. Such "two-peak" distribution patterns are more often found when there is complete central division of the articular cartilage of the trochlear notch than when it is continuous. In the latter case, a more central localisation of higher subchondral density is common. In the humero-radial part of the joint, the mineralisation pattern suggests central pressure transmission, probably a result of the fovea capitis radii being slightly less curved than the opposing capitulum.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1992

Demonstration of subchondral bone density patterns by three-dimensional CT osteoabsorptiometry as a noninvasive method for in vivo assessment of individual long-term stresses in joints.

Since the work of Pauwels and his successors, it has been possible to use the distribution of subchondral bone density within a joint surface as a metric parameter that can reflect the principal long-term stress acting upon a joint. However, the x-ray densitometry method he employed cannot be applied to living people. A procedure was therefore developed whereby CT osteoabsorptiometry (CT OAM), based on the use of computed tomography, allows the distribution pattern of the density to be demonstrated in living subjects. This method has now been further developed, so that the form of the individual joint surfaces can be included by means of a three-dimensional reconstruction program. This method is presented here. In addition, selected representative examples of various joints from normal people, athletes, and patients are used to demonstrate the use of CT OAM. In these examples from living subjects, regularly occurring, reproducible distribution patterns of subchondral bone density can be recorded, reflecting changes in mechanical stresses on a joint (increased stress, reduced stress, and disorders of joint mechanics). CT osteoabsorptiometry is demonstrated as a suitable noninvasive technique for investigating the individual long-term stresses (loading history) acting on a living joint.

Absorptiometry, Photon↗
PubMed1992

Direct and CT measurements of canals and foramina of the skull base.

This investigation is based on measurements of 60 macerated adult European skulls from the Alexander-Ecker Collection at the Anatomy Department of the University of Freiburg. Computer tomographical (CT) and anatomical measurements were compared to assess the accuracy of the CT representation of osseous structures. Nine structures were examined: the optic canal; the superior orbital fissure; the foramen rotundum; the foramen ovale; the foramen spinosum; the foramen Vesalii (venosum); the carotid canal; the internal auditory canal, and the hypoglossal canal. The results show a good and even excellent correlation if the cranial opening is approximately at a right angle to the scanline. For this reason, the results of the coronal examination of the internal auditory canal are less satisfactory, and the coronal and axial measurements of the hypoglossal canal show only a moderately good correlation.

Cephalometry↗