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Biomedical subjects

H G Schmidt

Publications and source records attributed to H G Schmidt.

At least 19 recordsLinked to original sources

The psychological basis of problem-based learning: a review of the evidence.

Several potential advantages for students' learning are claimed for problem-based learning (PBL). Students in PBL curricula may be more highly motivated; they may be better problem solvers and self-directed learners; they may be better able to learn and recall information; and they may be better able to integrate basic science knowledge into the solutions of clinical problems. Although some of these claims find theoretical support from the literature on the psychology of learning, to date there has been no review of the experimental evidence supporting the possible differences in students' learning that can be attributed to PBL. In this review article, the authors examine each claim critically in light of that evidence. They conclude that (1) there is no evidence that PBL curricula result in any improvement in general, content-free problem-solving skills; (2) learning in a PBL format may initially reduce levels of learning but may foster, over periods up to several years, increased retention of knowledge; (3) some preliminary evidence suggests that PBL curricula may enhance both transfer of concepts to new problems and integration of basic science concepts into clinical problems; (4) PBL enhances intrinsic interest in the subject matter; and (5) PBL appears to enhance self-directed learning skills, and this enhancement may be maintained.

Curriculum

[Ilisarov ring fixation and its technical application].

The Ilisarov ring fixator is an extremely versatile external fixation device. There is a wide range of indications for its use, e.g. fractures, pseudarthroses and non-unions, large defects, deformities and limb shortening. The device consists of rings or half-rings, which are connected to each other by threaded rods or plates and to the bone by wires under tension. This design allows neutral fixation, compression or distraction of the bone fragments. Because of its low axial stiffness at low loads and increased stiffness at higher loads, this fixator promotes osteogenesis and reduces strain on the tissues in functional treatment. Surgical intervention for its application is minimally invasive. This is a useful addition to the orthopaedic surgeon's armamentarium, providing proper attention is paid to preoperative planning, the principle rules of frame design and wire insertion technique, and postoperative management.

Biomechanical Phenomena

[Treatment of chronic osteitis of the femur].

Since May 1990, we have treated seven patients with chronic osteomyelitis of the femur. The Ilisarov apparatus was used in three of these cases for fixation and in four cases for segment transport. The treatment of four patients is now complete. We have not found any problems in bone regeneration. The use of pins in the proximal and middle thirds of the femur has proved problematic due to the soft tissue damage. Instead of this, we recommend using Schanz screws, which can be fixed to the arch with the AO lock. Moreover, it is easier to shorten the 180 degrees arch to 90 degrees or 120 degrees using the Schanz screws. To prevent problems, it is better to assemble the apparatus before use and to take into consideration the anatomical and functional situation.

Adult

[Treatment of chronic osteitis of the tibia].

Since the beginning of May 1990, we have been using the original Ilisarov apparatus in our treatment of osteomyelitis. It has been used both statically and dynamically after corticotomy for segment transport and lengthening. So far we have treated 24 patients, of whom 13 had defect osteomyelitis, 9 had unstable infections and 2 had stable osteomyelitis with deformities. On average the bone defects measured 7.6 cm, and nine patients had soft tissue defects larger than 6 cm2. The Ilisarov apparatus performed a holding function in seven cases after defect grafting using autogeneic spongiosa. It was used in four cases for gradual compression, in seven cases for segment or fragment transport, in three cases for secondary lengthening and in three cases for correction. In all cases the infections were eliminated and stability was obtained. The duration of segment transport corresponded to the defect size, with a daily lengthening of approximately 1 mm. The fixation times ranged from 112 to 483 days (mean: 240 days). Apart from one special situation, no bone regeneration problems were observed. Some of the complications we encountered must be regarded as beginners' mistakes. We observed problems with segment transport (early corticotomy healing, deformity, non-union at the docking site) and problems with equipment, which has now been improved. For closure of the soft tissue defects it was sufficient to use mesh grafting. Its versatility and advantages as a stabilizing apparatus have made the Ilisarov fixator the instrument of our choice, especially in the treatment of circular infected defects larger than 3 cm.

Adult

[Biomechanics of the ring fixator--contributions of individual structural elements].

The mechanical behaviour of the circular external fixation device using thin, pre-tensioned wires is difficult to predict, because the individual elements, such as rings, rods and wires, can be assembled in a large variety of configurations. This behaviour is of particular importance in the treatment of large segmental defects and in bone lengthening, because most of the load is transmitted through the fixator. In this study, the mathematical basis of the widely varying definitions of stiffness under axial, bending and torsional loads is presented. The principal variables influencing a particular configuration and their effects are indicated. Particular consideration must be given to the fact that the wires under tension generate a non-linear behaviour of the frame. The information needed for reporting on different fixator systems is indicated. Finally, the effect of individual structural elements, such as number, direction and tension of the wires, number of threaded rods and distance between the planes of the rings on the different stiffnesses, is presented and discussed with respect to clinical significance.

Biomechanical Phenomena

[Initial modifications of the ring fixator apparatus].

To increase the practicability of Ilisarov's ring fixation apparatus, we introduced the following modifications: Clamping of the fixation wires using a quick collet with a force indicator, which enables reproducibly preuse and rapid clamping. Hardened screws to maintain the tension longer. Production of the olive wire from homogeneous implant steel by the cold-press method. Optimization of the cutting edge at the wire tip. Measurement of tension in the fixation wire. A distractor incorporating a clock and a device showing the distraction achieved so that doctor and patient can better supervise the distraction procedure. Simplifications of the wound dressing.

Biomechanical Phenomena

A cognitive perspective on medical expertise: theory and implication.

A new theory of the development of expertise in medicine is outlined. Contrary to existing views, this theory assumes that expertise is not so much a matter of superior reasoning skills or in-depth knowledge of pathophysiological states as it is based on cognitive structures that describe the features of prototypical or even actual patients. These cognitive structures, referred to as "illness scripts," contain relatively little knowledge about pathophysiological causes of symptoms and complaints but a wealth of clinically relevant information about disease, its consequences, and the context under which illness develops. By contrast, intermediate-level students without clinical experience typically use pathophysiological, causal models of disease when solving problems. The authors review evidence supporting the theory and discuss its implications for the understanding of five phenomena extensively documented in the clinical-reasoning literature: (1) content specificity in diagnostic performance; (2) typical differences in data-gathering techniques between medical students and physicians; (3) difficulties involved in setting standards; (4) a decline in performance on certain measures of clinical reasoning with increasing expertise; and (5) a paradoxical association between errors and longer response times in visual diagnosis.

Clinical Competence

[The classification of osteomyelitis].

The article presents the classification of osteomyelitis commonly used by us, where the four typical characteristics are described by means of figure codes: Cause of infection (A), duration of infection (D), bone findings (K) and soft part findings (W) at the beginning of osteomyelitis therapy. The characteristics are represented by different figure combinations, single-digit figures being sufficient for description, whereas multiple-digit figures (maximum: 4) are required for more exact typing. Each characteristic is coded separate from the others, thus making it possible to communicate individual characteristics. --Our findings are always based on simple measurement data. Bone defects are calculated approximately spatially by means of transformation. The concepts and definitions are explained. --Classification is intended to be helpful when compiling differentiated statistics and to enable a comparison in case of diagnostic or therapeutic studies on osteomyelitis.

Humans

[Late results of arthrodeses of the upper ankle joint].

Arthrodesis may be mandatory after destruction or painful arthrosis of the ankle joint. The time at which this should be performed, as well as the technique to be employed, are both judged differently by various writers. We used exclusively the fixateur externe for stabilisation with 44 arthrodeses of the ankle joint, since this ensures stability during exercise and partial load. The complications recorded were two aseptic necroses of the talus and dysostosis in two cases which required corrective surgery. The results obtained by use lead us to the following conclusions: More than one-half of the examined subjects wore the orthopaedic made-to-measure shoes for longer than one year compensating the leg shortening by an average of 1.0 cm. The intraoperatively attempted repositioning of the talus in relation to the axis of the tibia tended to have a rather negative effect in our patients. The at least equal long-term results of early and late arthrodeses indicate that early arthrodeses are preferable, seeing that 55.8% of the followed-up persons were able to resume their professional activities relatively quickly.

Adult

Comparing the effects of problem-based and conventional curricula in an international sample.

In this article, the authors review 15 studies that compare various educational outcomes of problem-based, community-oriented medical curricula with those of conventional programs. The data suggest that problem-based curricula provide a student-centered learning environment and encourage an inquisitive style of learning in their students as opposed to the rote memorization and short-term learning strategies induced by conventional medical education. In addition, community-oriented schools appear to influence the career preferences of their students. The few data available show that significantly larger proportions of graduates from these schools seek careers in primary care. Some of the studies reviewed suggest that students in conventional programs perform somewhat better on traditional measures of academic achievement than do students in problem-based curricula. However, these differences, if any, tend to be very small. Data with respect to performance on instruments measuring clinical competence are inconclusive. Finally, the authors discuss the difficulties involved in carrying out comparative research at the curriculum level.

Achievement

Contextual factors in the activation of first diagnostic hypotheses: expert-novice differences.

According to Feltovich & Barrows (1984), the general frame used by medical experts to construct a mental representation of a particular patient problem contains a component part for those illness features that are associated with the acquisition of the illness. These 'enabling conditions' are related in several ways to the patient's disease. Examples are conditions like sex and age, or risk factors originating from work, behaviour and hereditary taint. Because of the sequential nature by which patient data become available during a clinical interview, contextual information is expected to play an important role in the generation of initial diagnostic hypotheses. To investigate the hypothesis that experienced doctors better utilize this kind of information, a group of 18 experts and 17 novices was confronted with 32 short case histories each presented on three slides: a portrait of the patient, the patient chart containing previous disease history, and a slide with the presenting complaint. It was hypothesized that differences in the number of correct diagnoses would emerge between the two groups, because the experts would use the contextual information, implicitly provided by picture and patient chart, in a more extensive way. If so, this would show in the amount of information that is explicitly recalled later. The data confirmed these predictions. The experts produced almost 50% more correct hypotheses as compared to the novices and were able to reproduce a larger amount of contextual information in particular information that was directly relevant to the patient's problem. Only the expert group showed a high correlation between accuracy of diagnoses and recall measures.

Adult

[Reconstruction of tangential and circular infected bone defects].

In the treatment of bone infections the reconstruction and rehabilitation of bone defects is a problem that often requires treatment secondary to curative treatment of the infection. For the reconstruction of smaller and more extensive defects we used predominantly (92.7%) autogenous (autologous) untreated spongiosa and in only 7% of the cases allogenic (homologous) spongiosa from an organ bank, this being added if necessary. Recently the additionally introduced vascularized bone chip has become a useful extension of the therapy concept. The problems and complications of defect reconstruction are demonstrated for 705 cases of bone infection with 472 defects of different sizes, based on a comprehensive classification with defect calculation. Surgical technical approach and special aspects of after-treatment are described, as well as the results for every group of cases. We achieved stability and freedom from infection in a total of 93.7% of the patients. As was to be expected, the problems grow with the size of the defect. Particularly problematic are joint infections with adjacent extensive circular defect.

Bone Transplantation