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Biomedical subjects

H Cotta

Publications and source records attributed to H Cotta.

At least 91 records · Page 5Linked to original sources
PubMedDate not supplied

[Survey of materials in hip endoprosthesis].

While bone cement debris has been recognised as an important factor in aseptic loosening of prosthetic components, the interest is now focused on the impact of debris and wear-off particles from polyethylene and metal alloys. As an optimal lubrication cannot be generated yet, direct contact between the components produces wear particles, depending on the materials used. The materials reported on include alloys based on iron, cobalt, titanium and polyethylene, bone cement and ceramics. These all show the problem of debris, friction, corrosion (except ceramics) and load failure, related to the work up process. The practitioner is given an overview and tables are presented to compare the used material.

Alloys↗
PubMedDate not supplied

[The Göttinger minipig as an animal model in hip endoprosthesis. Anatomy, anesthesia, operation results].

The Göttingen mini swine is a good experimental animal. The electrolytes and the bone healing rate is comparable to human. The weight of the animals should be 30-45 kg. All surgery is performed under endotracheal general anaesthesia without any complication. There is minimal blood loss because blood pressure is only 40/80 mmHg. We used the anterolateral approach. The feature peculiarity of this animal model are: 1. Skin incision should start 10 cm cranial to the tail and should be curved. 2. The osteotomy of the head is V-shaped in maximal external rotation. 3. The acetabulum is prepared with a 23.5 mm reamer. 4. The stem should be implanted first. After completion of the preliminary test operations, 10 animals were operated in the described standard manner. During one year follow-up there was only one radiological cup-loosening.

Acetabulum↗
PubMedDate not supplied

[Deformation in conservative treatment of vertebral fractures].

The indication for functional or operative treatment of fractures of a vertebral body depend on the additional injury, on the stability of the fracture and on the amount of deformity. In a retrospective radiological study on 74 patients we analysed the behavior of secondary deformation in stabile fractures of thoraco-lumbal vertebral bodies under treatment with a 3-Points-Corset. The average initial sagittal deformity was 12.5 degrees. After three months an average increase of 1.5 degrees was measured resulting in an average increase of total kyphosis of 2.5 degrees during fracture consolidation. No further secondary changes were seen after a period of three months following the injury.

Adolescent↗
PubMedDate not supplied

[Measuring spatial micro-movement of the femur shaft of endoprostheses in relation to the spatial force system].

A precision measurement method (resolution: 0.1 micron) is described that simultaneously tracks spatial movement of the prosthesis and its bending as a function of the spatial force system (three force and three torque components). With this technique, we examined the effects of complete separation between shaft and cement on bending and micromovement. With regard to mechanical stability a completely tied and a loosened prosthesis differ only in respect to torsional load: the loosened prosthesis bears a 2.5-fold larger torsion flexibility. In both cases the shaft does not move like a rigid body: it bends up or down depending on the way the torque acts. It is the torques (that are produced by the forces) rather than the forces themselves that are responsible for the extent of micromovement and bending. In the completely loosened shaft, the shaft's apex only moves either intrusively or extrusively according to the directions of the torque vector: the horizontal movement cannot be resolved. The data suggest that shafts that are freely mounted into its cement quiver load the cement layer in a less damaging fashion than tied shafts.

Adult↗
PubMedDate not supplied

[Are pathohistological studies helpful in the clinical differential diagnosis of chronic arthritis?].

We have evaluated the diagnostic and therapeutic consequences of histopathological examinations of knee synovium from 216 patients with chronic arthropathies. We were able to differentiate between non-rheumatic etiologies, such as tuberculous arthritis, villonodular synovitis, crystal arthropathies and chondromatosis. This resulted in the establishment of a diagnosis and often a guide to therapy as well. It is rarely possible however to conclusively differentiate among the different inflammatory rheumatic diseases or osteo-arthroses by the histopathology of the joint lesions seen.

Arthritis↗
PubMedDate not supplied

[Biomechanical principles in diarthroses and synarthroses. I: Basic concepts in diarthroses].

The incongruity of the articulating surfaces is one of the main constructional characteristics of human joints. Unfortunately, this has virtually been neglected in studying of the mechanism of joints. Only in incongruent articulating surfaces does the force locking, which is permanently produced by gravity and/or compressively acting muscular forces (muscular tonus), engender mechanically stable states of balance of the connected limbs. From the incongruity one can conclude that the dimeric link chain represents the most simple constructional element of the human joints. They are force locked, constrained gear systems composed by dimeric link chains. In this context the overlapped dimeric link chain deserves special attention since it is the only mechanically stable device in the presence of compressive forces. We present fundamental terms and characteristics of the gear mechanisms of human joints.

Biomechanical Phenomena↗
PubMedDate not supplied

[Biomechanical principles in diarthroses and synarthroses. IV: the mechanics of lumbar vertebrae. A pilot study].

UNLABELLED: Theoretical considerations help define the requirements for an apparatus that is to localize the instantaneous helical axes (IHA) of axial rotations of lumbar segments. RESULT: Since the range of axial rotation of an L3/4 segment is in only approximately +/- 1.5 degrees the rotational angle intervals have to be smaller than 0.3 degree with an resolution less than 0.03 degree in order to be able to determine the loci of the IHAs. For the first time in vitro measurements are presented that satisfy this requirement. The data prove that the guidance by the artt. zygapophysiales critically influence the possible positions of the IHA. Comparatively, ligaments and intervertebral disk play a marginally role. During axial torques Tz the IHAs lie dorsal to the intervertebral disk and migrate from one joint to the other depending on axial rotation (length of migration: approximately 3-4 cm). The IHAs lie almost parallel to the axial torque vector. When the joints are removed the IHA is stationary and almost perpendicular to the intervertebral disk and intersects the disk's central region. The screw inclination (pitch) of the instantaneous screw movement is proportional to the rotational angle. Therefore, depending on the direction of rotation, one obtains left or right handed screw movements. This means: axial torsional load leads to an increase in thickness of the intervertebral disk. During preloads that produces extensions the fixed centrodes (paths of axis migration) of intact segments are dorsally beaten out, whereas during flexional loads they are ventrally beaten out. Then, the IHAs migrate through the canalis vertebralis. By the concept "dimeric link chain" the different shapes of the fixed centrode are traced back to the morphology of curvature of the articulating surfaces. The measurements suggest the hypothesis that the distinct nonlinearity of the load displacement curves (s-shape of alpha = alpha (Tz) funktion is an affection of IHA migration. Comparatively, the influence of ligaments can be neglected. The measurements suggest the hypothesis that the hysteresis of the load displacement curves (neutral zone) is an artefact that does not appear in vivo. Altogether, the experiments prove that the loci of the IHAs are determined by the interplay of preload, structure of the applied force system and morphology of curvature of the articulating surfaces. By that the possibility is clinically given to calculate the multitude of possible movements as function of muscle activity when in the individual the shape and the position of the articulating surfaces are measured in vivo (by NMR-methods e.g.). A physically based classification of pathological cases seems to be possible.

Biomechanical Phenomena↗
PubMedDate not supplied

[Cementless cup anchorage in hip endoprostheses. Comparative study of 3 cup systems with titanium surface].

A wealth of commercially available hip endoprotheses makes it difficult for the practitioner to choose the best implant for each individual case. In a multi-centre study, in which 22 hospitals took part, a cementless stem was used 1172 times and was combined with 3 different cementless cup components. The follow up period ranged from 1-8 years. In 321 cases the spherical Mecring cup, in 208 cases the spherical CLS-expansion cup and in 643 cases the conical Weill-ring was implanted. The predominant indication for the THR was primary coxarthrosis (767 patients). Evaluation of clinical results was based on the Merle d'Aubigné score. Good or excellent results were found in 82% for the Mercring, in 85% for the Weill-ring and in 91% when the CLS-expansion cup was used. Whereas 88% of the patients with the Mecring or Weill-ring had minimal or no pain, 94% of the patients had minimal or no pain when the CLS-expansion cup was implanted. Aseptic loosening was found in 1.25% for the Mecring and 1.5% with the Weill-ring. In the CLS-expansion cup group, 2 cases with radiological signs of loosening were seen, but neither patient required revision. The CLS-expansion-cup with the press fit system shows better medium follow-up results in this study, than the Mecring or Weill-ring systems.

Acetabulum↗
PubMedDate not supplied

[Definition of patellar chondropathy and patellar chondromalacia].

In the course of a review of the literature the definition, etiology, diagnosis and treatment of the disease entities chondropathy and patellar chondromalacia are compared. Without exception, the descriptions found are inconsistent and inaccurate. A new classification--chondromalacia, patellar and peripatellar syndrome--is proposed. Possible causes of these diseases in the subchrondral vascular system are mentioned explicitly ("patellar migraine", "patellar claudication").

Cartilage Diseases↗
PubMedDate not supplied

[Fractures and epiphyseal injuries in children with myelomeningocele].

Between February 1971 and February 1988, 947 children with myelomeningocele were treated at the Model Center of Heidelberg University Orthopedic Clinic. In 82 of these children, a total of 224 osseous lesions were seen. Metaphyseal and diaphyseal fractures were far more common than epiphyseal lesions, among which epiphysiolysis dominated. Diagnostically important symptoms included swelling, local hyperthermia, and high temperature. Owing to the paralysis, pain is of no value in diagnosing fractures. Protruding periosteal detachments are a common feature of lesions, and if this special form of healing of such fractures is unknown they may cause problems in differential diagnosis. Fractures in children with spina bifida should be treated conservatively, except for fractures of the femoral neck and epiphyseal lesions, which are treated with transcutaneous Kirschner wiring. Immobilization in plaster, postoperatively and during treatment of the injury, is the most common cause of osseous lesions in spina bifida children. Immobilization in plaster should therefore be minimized.

Adolescent↗
PubMedDate not supplied

[Biomechanical principles in diarthroses and synarthroses. II: The humerus articulation as a ball-and-socket joint].

The shoulder joint does not represent a simple ball-and-socket joint with three degrees of freedom unlike widely believed. Series of X-ray pictures show that in abduction the momentary rotational axis does not meet the center of the humerus. Morphological measurements yield the result that the radius of curvature of the cavitas is slightly greater (2 mm) than the humeral one. This physiological incongruity of the articulating surfaces is functionally necessary. Thus, the shoulder joint represents a force-locked dimeric ball-and-socket joint. In abduction e.g. the humerus simultaneously rotates around the humeral center and around the cavitas center in opposite direction. The resultant momentary rotational axis is therefore shifted towards the scapula as in vivo measurements confirm. Fundamental kinematical and statical properties of the joint are derived which explain substantial experimental finding in literature.

Biomechanical Phenomena↗
PubMedDate not supplied

[Biomechanical principles of diarthroses and synarthroses. III: Mechanical aspects of the tibiofemoral joint and role of the cruciate ligaments].

The tibiofemoral joint (TFJ) is force-locked. It takes its function as it is compressively loaded. The geometrical shape of the articulating surfaces and the acting force system (given by muscles and gravity) determine the kinematics as well as the quality and extent of static stability of the knee. The mechanism of the TFJ is derived from the anatomical shape of the articulating surfaces. In antero-posterior direction the joint guidance is structurally given by a stretched and overlapped dimeric link chain in lateral and medial region, respectively. Altogether, the two chains are linked up to a four-bar-chain (link quadrangle) that solely allows the tibia to strike backwards. The extent of individual extension can be rejected to morphological data of the femoral condylus. In squat position the extent of mechanical stability of the joint can be changed and even reversed to instability by a rotation of the resulting compressive joint force around the momentary rotational axis of the gear system while the joint position remains unaltered. Thus e.g. the process of straightening up is structurally explained. The cruciate ligaments do not bear any direct mechanical guiding function. They represent a sensor system which structurally resembles a mechanical bridge circuit. Beside detecting the degree of flexion it is able to monitor the indispensable contacting of the articulating surfaces. The menisci represent an additional, similarly working sensor system. At first approximation these two sensor systems are aligned in two planes which are perpendicular. Therefore they form a spatial sensor system. The presented theory is derived from mechanical, morphological, and physiological findings and gets evidence by measurements on knee loads during seated cycling.

Anterior Cruciate Ligament↗
PubMedDate not supplied

[CLS multicenter study--8-year results].

The principles of proximal fixation of cementless endoprostheses is established already. This theory was the subject of the present multi-center study of 22 clinics. Between 1984 and 1992 all 1830 patients with an uncemented CLS press-fit stem had a clinical and radiological follow-up examination and computer documentation. The evaluation of the clinical results are based on the Merle d'Aubigné score. In 91% we found a good or excellent result. For the remainder of patients (9%) with a score less than 14 each case has been especially analysed. The incidence of femor component loosening was less than 1% within the average follow-up time of 2.5 years. The medium-term results with the uncemented CLS press-fit stem confirmed the idea of proximal load induction on the femur.

Adult↗
PubMedDate not supplied

[Limb-saving resection procedures in primary malignant bone tumors].

Thoroughly indicated and performed limb salvaging resections of primary malignant bone tumors can be as well affective as amputations and disarticulations. Possible limb salvaging operative procedures are described with regard to histodiagnosis grading, localisation, expansion of neoplasma as well as to the personality of the patient.

Adolescent↗