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The antigenic characterization of IBDV, a virus that causes an immunosuppressive disease in young chickens, has been historically addressed using cross virus neutralization (VN) assay and antigen-capture enzyme-linked immunosorbent (AC-ELISA). However, VN assay has been usually carried out either in specific antibody negative embryonated eggs, for non-cell culture adapted strains, which is tedious, or on chicken embryo fibroblasts (CEF), which requires virus adaptation to cell culture. AC-ELISA has provided crucial information about IBDV antigenicity, but this information is limited to the epitopes included in the tested panel with a lack of information of overall antigenic view. The present work aimed at overcoming those technical limitations and providing an extensive antigenic landscape based on original cross VN assays employing primary chicken B cells, where no previous IBDV adaptation is required. Sixteen serotype 1 IBDV viruses, comprising both reference strains and documented antigenic variants were tested against eleven chicken post-infectious sera. The VN data were analysed by antigenic cartography, a method which enables reliable high-resolution quantitative and visual interpretation of large binding assay datasets. The resulting antigenic cartography revealed i) the existence of several antigenic clusters of IBDV, ii) high antigenic relatedness between some genetically unrelated viruses, iii) a highly variable contribution to global antigenicity of previously identified individual epitopes and iv) broad reactivity of chicken sera raised against antigenic variants. This study provides an overall view of IBDV antigenic diversity. Implementing this approach will be instrumental to follow the evolution of IBDV antigenicity and control the disease., Competing Interests: Declaration of Competing Interests The authors declare no conflict of interest., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Day-old chick quality is an essential element for the overall profitability of the broiler productive cycle and has been associated with the growth performance and feed conversion rate. An effect on the development of the immune system was also reported, which could likely account for reduced susceptibility to infectious diseases and improved animal welfare parameters. Besides direct cost reduction, lower antimicrobial use and improved animal welfare are crucial in the directive of European Union legislation and are at the forefront of customer choices. Several factors contribute to determining the chick quality. Breeder flocks genetics, health, and management affect the egg features, quality, and bacterial load. However, hatchery practices play a pivotal role, since adequate hygiene and handling are fundamental in reducing egg contamination and cross-contamination. The presence of rotten eggs is often regarded as a major risk, since the internal bacterial load can contaminate the needle used for in-ovo vaccination, the nearby eggs, and the whole incubator/hatching room when broken. In the present multicentric study, representative of 40 hatcheries located in 11 European countries, a remarkable impact of the rotten egg percentage on the hatchery productive parameters, representative of the hatchability, embryo mortality, and level of contamination, was demonstrated. Efficient rotten egg removal and the application of appropriate detection and removal tools should thus provide remarkable benefits for hatchery performance and indirectly for downstream poultry production.

Bone mineralisation during and after limb lengthening procedures on the femur or tibia using unilateral fixators has been monitored quantitatively using dual energy X-ray absorptiometry (DEXA). We measured the bone mineral density (BMD) prospectively in the newly formed callus, in the bone adjacent to the callus and in the proximal femur. In twenty-one patients we showed a typical course with a peak value at 4-6 weeks after beginning distraction and a minimum value at maximum distraction. In the consolidation period the BMD in the distraction gap increased until the fixator was removed. The BMD in the regenerated bone increased faster in the regions of interest (ROI) opposite the fixator compared to those near it. Dynamisation caused more homogeneous regeneration equalising VBMD in the different ROIs. The BMD in the proximal femur of the leg which was operated on decreased to 67% and in the opposite leg to 87% of the preoperative value. DEXA provides a precise and quantitative assessment of callus and bone mineralisation during limb lengthening and helps in understanding what is happening during these procedures.

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.

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.

With dual-energy X-ray absorptiometry (DEXA), bone mineralization during and after limb-lengthening procedures with unilateral fixators can be monitored quantitatively and precisely with low radiation exposure. We measured prospectively the bone mineral density (BMD) in the newly formed callus, in the bone adjacent to the callus and in the proximal femur in 21 patients with leg lengthening of the femur and/or tibia with unilateral external fixators. Mineralization showed a typical course with a peak value of 0.365 +/- 0.196 g/cm2 (30.9% of the first value) at 6-8 weeks after the beginning of distraction and a minimum value at the time of maximum distraction. In the consolidation period BMD in the distraction gap increased to 1.020 +/- 0.234 g/cm2 (87%) at the time of fixation removal. BMD in the regenerated bone increased faster in regions of interest (ROIs) opposite the fixator compared to ROIs near it. Dynamization of the fixation device led to a 13% increase in mineralization velocity (VBMD). On the other hand, dynamization caused more homogeneous regeneration equalizing VBMD in the different ROIs as well. BMD in the proximal femur of the leg operated on decreased to 67% and in the contralateral leg to 87% of the preoperative value. We consider DEXA to provide a precise and quantitative assessment of callus and bone mineralization during limb lengthening with unilateral fixators. Since we are well aware of the limitation of the technique. DEXA helps to understand what is happening in limb-lengthening procedures by providing quantitative values.

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.

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.

In 80 patients with primary traumatic shoulder dislocation treated at the Heidelberg Orthopaedic University Hospital we had a follow-up examination. We wanted to know about age and sex of the patients, the number of redislocations in correlation to time and way of fixation. We had 70% male and 30% female patients with 97.5% of anterior dislocation. The minimum age was 16 and the maximum 87 years with an average of 44 years. 48 patients had a Desault bandage for 2 weeks and 32 had a shoulder-arm plaster cast for 3 weeks. There was no difference between both ways of fixation. We also could not see any better results after more than a 3 weeks' fixation. The most important fact for redislocation is the age and activity of the patients. A young man has a very high risk of redislocation within the first year.

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.

High tibial wedge osteotomies are often followed by transient neurological complications. From a retrospective study of 132 patients it appears that the incidence of this troublesome complication can be reduced after osteotomy with external fixation by using a technique of making consecutive drill holes of increasing diameter followed by osteoclasis. This reduction of neurological complications was most marked when a less extensive surgical approach was used.

The recent experiences which the university hospital in Heidelberg has made with the spherical Mecring must be valued positively. Clinical, radiological and subjective dates from 147 patients were worked up retrospectively. Indeed, the positive results must be considered as relative because of the short respectively medium-term period of control. Nevertheless, the repeated improvement in the second group after a period of postexamination on a average of 3.05 years lets hope for positive long-term results. In the period between 1985 and 1990 three sockets had to be changed. The reasons that the sockets loosened were not specific for the screwing but depending on the individual patients or on the implantations and technical circumstances. The negative results achieved by Engh et al. 1990 could not be recognized (8). He measured a radiological instability of 18% and a technical instability of 28%. What Engh did was measuring simple review photographs and extracting valuable material from them while using geometrical methods. This method shows various measuring mistakes. Therefore Engh's conclusion that the screwing should not be used for implantation because of its displacement in the bones is doubtful. The doubts seem to be supported by the results of our comparison of two series of X-ray photographs with defined different pelvis positions of the same patient. The screwing seemed to be significantly displaced in cranio-medial direction. This was proved by experimental photographs with a pelvis raised to 6 cm in contralateral direction. But the results were a matter of radiological illusion. Radiological migration of the screwing is only provable by complicated X-ray analyses steered with the computer. These big X-ray series are not accessible at the time.

The chondromyxoid fibroma as a benign bone tumour is described. The difficult but extremely important differential diagnosis from chondrosarcoma is discussed, and the question of the existence of malignant chondromyxoid fibroma is examined. Cases of malignant chondromyxoid fibroma that have been reported in the literature are described and critically analysed. Experience with seven chondromyxoid fibromas and two tumours misdiagnosed as malignant chondromyxoid fibromas are described. In view of the clear definition of chondromyxoid fibroma and chondrosarcoma the term malignant chondromyxoid fibroma is not justified and should no longer be used.

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.

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.

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.

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.

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.

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.

There is a tendency for malunion to occur in fractures of the knee region in children because the growth plates are often affected. Leg length discrepancies are reported in more than 50% of the children and axis deviations in 20-40%. The prognostic significance of epiphyseal lesions is described (not always accurately) by the classifications of Salter and Harris or Aitken. Treatment is mostly directed at leg-length discrepancies and axis deviations by resection of callus formations, epiphysiodeses and osteotomies. A complete bone growth history is necessary to plan the operative procedure.

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.

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").

A 48-year-old patient sustained depressed fracture dislocations of both shoulder joints during a grand mal epileptic seizure. Surgical treatment consisting of implantation of two Neer total replacements was successful: the functional result was good, and within 12 weeks the patient was free of pain and able to resume work.

It is the aim of this paper to draw attention to the problems facing the clinician when he tries to find a suitable nomenclature and classification of congenital malformations of the forearm and hand. The classification presented here takes into consideration the so-called Paris Nomenclature of 1969, as well as the systematisation of limb defects of the Working Group of the International Society for Prosthetics and Orthetics (commented upon by Henkel and al 1979), as well as the systematic organisation of malformations of the forearm and hand by Müller (1937), Werthemann (1952), Hopf (1959) and Witt, Cotta, Jäger (1966). On no account may this be regarded as a rigid and final setup. Efforts to achieve greater precision are still under way as before, with special emphasis on significant information supplied by teratology, embryology, genetics and biochemistry.

Part of the patella ligament was resected in rabbits and replaced by carbon fibre implants. After 1, 2, 3, 6 weeks, 3 and 12 months carbon implants with surrounding tissues as well as iliac lymph nodes were removed and examined by light- and transmission electron microscopy. Of special interest were the questions whether the carbon fibre implant, will be removed by phagocytosis and substituted by a new ligament or a adequate repair tissue? Our light- and transmission electron microscopic studies give no indication of successful removal of carbon fibres by phagocytosis. The carbon fibre implant was surrounded by dense connective tissue like a scar. In deep layers of the carbon implant was no vital dense or regular connective tissue, even not after 3 and 12 months. There is no replacement of the carbon fibre implant by a new ligament or tendon but a persistent foreign body reaction. With regard to these results it is very doubtful if good late results with ligament and tendon replacement by carbon fibre implants can be expected in patients.

Knowledge of the physiology of the epiphyseal cartilage, respectively epiphyseal plate, is essential for an understanding of defective growth and abnormal modeling of the long bones. The epiphyseal cartilage develops from the embryonal, cartilaginous long bone structure. The histology of the epiphyseal cartilage is characterised by definable zones representing the individual differentiation steps from the reformation of cartilage to chondrolysis. Modeling of the ends of the long bones is also influenced by a transversal and longitudinal direction of growth in the epiphyseal cartilage. The intercellular substance mainly contains collagin, proteoglycanes and non-collagenic proteins. These macromolecules are compounded by means of physicochemical bonds and are responsible for the special mechanical qualities of the hyaline cartilage. The process of mineralisation at the base of the epiphyseal cartilage is an essential differentiating step for the ossification processes which take place in the metaphysis. Two pathogenetic principles at the epiphyseal cartilage appear to be important for the defective growth of the long bones. On the one hand, the flowing equilibrium between the differentiation steps of cartilage reformation, transformation of the hyaline cartilage into a mineralised cartilaginous tissue and chondrolysis is changed, whereas on the other hand the turnover of these differentiation steps is retarded or accelerated.

The postoperative fracture of the femur following total hip arthroplasty ranks third in occurring complications and the number of such cases is increasing. Most of the patients are elderly and multi-morbid and the fractured femur had undergone previous operations. Using the literature our own experience in 15 cases and applying a fracture classification we make suggestions for treatment of the different fracture types. Considering the patients overall health it's possible to obtain good results in the operative therapy which was necessary in most cases of these femur fractures.

Cross-plate arthrodesis produces a problem of incongruence which cannot be solved by surgical skill Mechanical factors, not foreseeable before operation, produce an inevitable divergence of pulling and torsion forces with a high risk of losening of the implant and pseudarthrosis, particularly when the acetabulum is degenerated. The mechanical forces are shown in Fig. 6. The review of our cases shows that healing after cross-plate arthrodesis may follow three pathways.

The post-traumatic frozen shoulder is a sickness which develops relatively frequently following even small injuries of the shoulder joint. The particular anatomic conditions of this joint are the cause of its frequent lesions. After an injury typical pathological changes in function are observed. Most common injuries are distorsions, contusions, luxations and especially in increasing age the subcapital fractures of the humerus. Other injuries as there are rupture of the acromio-clavicular joint, fractures of the clavicle or scapula may also cause a frozen shoulder. The clinical examination is most important as it is the basis of the therapy. The current procedure consists of intensive physical therapy. If this treatment is not successful other ways must be discussed, e.g. mobilisation under anaesthesia. Operative treatment has a very strict indication. Medico-legal points of view of the frozen shoulder are difficult but a connection between injury and degenerative changes ought not to be denied in clear cases.

Clinical and x-ray criteria for bone tumors should be analyzed very carefully. It is demonstrated that especially periosteal reactions are nor characteristic of any specific tumor but only of a certain type of stimulus upon the periost, which may be provoked by different agents such as tumor, pus, subperiosteal hematoma and others.

This article surveys the update knowledge of diagnosis and treatment of damage to the cartilage with particular reference to the femoropatellar joint. Complementary to this the biomechanical fundamentals and special anatomic features are explained, the knowledge of which is imperative for an understanding of the complex linkups and interconnections.

The presence of an hemarthrosis generally is a sign of a particularly severe joint lesion. Arthrous alterations appearing post-traumatically can therefore be due to the extent of the joint lesion as well as to the accompanying hemarthrosis. A group of 24 young adult rabbits was submitted to morphologic examinations in order to find out in which way an isolated hemarthrosis can be responsible of degenerative cartilage alterations. At intervals of eight days each, 3 cm3 of their own blood were injected into both knee joints of the rabbits. One knee joint was immobilized, the other was mobile. The results prove that the hemarthrosis represents a considerable risk with regard to the trophism of the concerned joint. A direct enzymatic damage to the joint cartilage alone or in combination with trophical alterations appearing later on can lead to a formation and aggravation of arthrosis. The degenerative alterations are increased in an immobilized joint. Bearing in mind these alterations, the conclusion is drawn for clinical practice that the hemarthrosis has to be considered when establishing both diagnosis and therapy plan (punction, joint lavage, drainage, immobilization as early as possible).

Regenerating synovium from seven patients was examined by light- and transmission electron microscopy. Superficial layers of the "neosynovium" are composed of histocytes, fibroblasts and intermedium cells, developing out of undifferentiated mesenchymal perivascular connective tissue cells. There is no closed cell-layer, as known from mesothelia, endothelia and epithelia. Our results are similar to those of normal synovium and the so-called "pseudo-synovium" of pseudarthroses. So superficial layers of these tissues are comparable specialized connective tissues. According to experimental results in animals, in patients there will develop a "neosynovium" comparable to the original synovium in structure and function. These results confirm synovectomy as a possible operative treatment in patients.

Wrist-joint instability can be caused by injuries to ligaments or bones, it can be intermittent or permanent. Clinical symptoms and pain sensations are non-characteristic. The X-ray findings are the clue to the diagnosis. In this article recommendations are given for exact X-ray positions of the hand and their evaluation. The classification of instability is corresponding to the X-ray findings. Further investigations like radiographs under stress, dynamic investigations or the arthrography of the wrist-joint can be helpful to find out the exact pathologic changes. They are variable and are ranging from dysharmonic movement to a complete destruction of the carpal bones. Treatment is according to the pathologic changes and their causes. Fresh ligamentous injuries (e.g. additional injuries to a Colles' fracture or a perilunate luxation) should not be discarded lightly. Most cases we saw presented very late, the patients showed already osteoarthritic changes of the carpal bones with destruction of the cartilage. The late results of ligamentous reconstructions have not fulfilled their expectations, the current trend is towards a partial arthrodesis of the carpal joints in order to reconstruct the joint stability under preservation of partial mobility. This method of treatment has certain disadvantages: Pathologic wrist-joint movements, impingement syndromes and undue stress reactions within the neighbouring joints. Recommendations for the different indications are given.

"Pathologic fracture" is understood as a discontinuity of pathologic bone caused by normal mechanical stress without adequate trauma. The pathologic condition of bone causing mechanical instability may be a general osteopathia (osteoporosis, osteomalacia, fibrous dysplasia, Paget's disease) or as well a localized one (primary or secondary bone tumors, tumor-like lesions, osteomyelitis). Following "pathologic fracture" pain and functional deficiency are severe, so besides diagnosis and treatment of basic disease conservative and often operative treatment of the pathologic fracture are necessary. The different procedures are discussed in relation localisation of pathologic fracture, basic disease and age of patient.

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.

Total hip and knee replacement is one of the most successful operative procedures in orthopaedic surgery. With respect to greater life expectancy, however, loosening of the implant and revision surgery with all its sequelae must be taken into account. Therefore joint preserving procedures resp. arthrodesis of the hip and knee joint are still of great importance. The best long term results can be achieved by operations which can improve the biomechanics of the joint. Operative procedures which aim at the biology of the joint only lead to temporary pain relief. Arthrodesis of the hip and knee joint should always be considered in young patients with no possibility for joint preserving techniques.

62 children with spondylolisthesis were examined. Functional anatomical studies on 25 growing human spines were performed to analyse their macro morphological behavior before and after spondylolisthesis. The progression of spondylolisthesis is explained as growth disturbance. The high incidence of spina bifida occulta in spondylolisthesis is a mechanical induced osteochondrosis of the dorsal arc. The different morphology of the spondylolisthesis in children depends mostly of the age of the beginning of this disease. The differentiation between the dysplastic and spondylolytic isthmic type of spondylolisthesis is not indicated. Pour prognosis is expected in young children with kyphosis and high ventral dislocation in the involved segment.

Emphasis is placed on the etiology of posttraumatic cartilage damage based on recent experimental findings. The latter suggest that postinjury cartilage impairment cannot only be regarded as a consequence of incongruity of the joint surfaces after intraarticular fractures but that immobilization, primary lesions of the joint surface caused by synovial enzymes, and hemorrhagic effusion are also pathogenetically significant. Furthermore posttraumatic synovitis with its faulty composition of the synovial fluid plays an equally important role in this context. Finally, in summarizing therapeutic recommendations are presented.