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The combined teaching of pathophysiology and physiology to medical students at the university of Gent, Belgium
WS4-K-2-05 THE PATHOPHYSIOLOGYOF OSTEOLYSIS IN TOTAL JOINT ARTHROPLASTY Thomas W. Bauer, M.D. PH.D. Departments of Pathology and Orthopedic Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio, USA. The long term results of total joint arthroplasty are excellent, but osteolysis may be associated with implant loosening a n d failure. Hypotheses concerning the pathogenesis of osteolysis include: 1) bone resorption related to altered transfer of mechanical loads ("stress shielding"), 2) immune-mediated inflammation initiated by "allergy" to metal ions, 3) osteonecrosis secondary to mechanical or hydrodynamic factors, and 4) bone resorption stimulated by the non-immune phagocytosis of debris particles by macrophages. Osteolysis may represent a combination of factors, but several lines of evidence now support the stimulation of osteoclasts by macrophages activated during the course of debris phagocytosis. This hypothesis is supported by the following observations: 1) biopsies of osteolytic lesions and of fibrous membranes a r o u n d loose total joint implants contain macrophages associated with small particles of wear debris, including polyethylene, methylmethacrylate bone cement and metal alloys, 2) digested samples from periprosthetic tissue contain billions of particles of wear debris per gram (dry weight), and these particles are small enough (0.5 um diameter) to be phagocytosed by macrophages, 3) macrophages in vitro have been shown to release cytokines, especially IL-6 in response to phagocytosis of polyethylene, methacrylate, or metal particles, 4) fibrous membranes adjacent to loose implants contain high concentrations of IL-6. Although controversial, the following observations suggest that this response is not immune mediated: 1) most patients with osteolysis lack antibodies directed against metal alloys, while some patients with circulating antibodies to metal ions do not develop osteolysis, 2) osteolytic lesions rarely contain prominent lymphocytes, and 3) T lymphocytes are not necessary for the macrophage response to wear debris. Similar to the pneumoconioses in which pulmonary fibrosis is stimulated by inhaled f o r e i g n particles, it appears that osteolysis and perhaps orthopedic implant loosening in general is the result of osteoclastic stimulation by macrophages activated by the phagocytosis of wear debris particles. The most prevalent type of debris is polyethylene, so limiting the amount of polyethylene debris should be important in improving the results of total joint arthroplasty.
WS4-K-3-01 THE COMBINED TEACHINGOF PATHOPHYSIOLOGYAND PHYSIOLOGYTO MEDICAL STUDENTS AT THE UNIVERSITY OF GENT, BELGIUM. J. Weyne and E. l.,aernix Laboratory of Normal and Pathological Physiology, University of Gent, Gent, Belgium. The purpose of pathophysiology is to present a mechanistic view of pathology in order to underscore the disturbances of the normal physiological mechanisms which lead to different diseases and the rationale of their therapeutic approach. In the academic training of a medical student the course of physiopathology is a link between the courses of physiology (and biochemist~) and medecine. Two different approaches therefore exist concerning the way of teaching pathophysiology, which can be presented either as a part of the course medecine, or as an extension of the courses physiology and biochemistry. Clearly, there is a fundamental difference between these two approaches since the clinician, whose medical thinking marts with symptoms to come to a diagnosis, usually has a deductive way of reasoning and an analytical view on pathophysiology, while the physiologist and biochemist, who first develop relevant experimental models to study the effect of a variable parameter, usually have an inductive way of reasoning and a holistio view on pathophysioiogy. Also, from a pedagogical point of view, teaching imthophysioiogy by *looking forward" into mechanisms of disease during the lectures of physiology, is more exciting than teaching mechanisms of disease during the lectures of medecine by "going backward" into basic sciences. That pathophysioiogy and physiology are indeed intermingled is also the view of the Federation of European Physiological Societies (FEPS) since most of the sessions of its 1st congress (to be hold in 1995 in Maastricht, The Netherlands) are planned to cover physiology and
pathophysiology. At the University of Gent, patliophysioiogy is being teached for more than 50 years by not-ciinicians: up to about 1980 as a separate course in the 1st clinical grade, but later in combination with the course of physiology in the 2nd and 3rd preclinical grade. By integrating the pathophysioiogy in the course of physiology, the latter becomes more practically relevant to the medical student. As an example the pathophysiology of pstroduodenal ulcer is reached in connection with the physiology of normal gastric secretion. Also, in the course of the lectures physiology a few seleclml patients are presented, whose symtoms, the pathophysioiogy of their disease, and the principles of its treatment arc discussed by tho (patho)physiologist and thc clinician. In the practical course of physiology, observations on humans (own body or fellow students) arc a substitution for experiments on animal preparations, as an cxamplc, in addition to the classical spirometric measurements of the lung volumes, the single breath nitrogen test is performed, with discussion of uncvcn ventilation, possible air way closure and calculation of residual volume, and eloclrical stimulation of the ulnar nerve with recording of the EldO of the hypothenar muscles is performed as a substitute for the animal nerve-muscle preparation. The combined teaching of physiology and Imthophyeiulogy, of course, assumes a medical training of the teacher of physiology, which poses the problem of recruiting new physiologists among the young M.D.'s,
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WS4-K-3-01 THE COMBINED TEACHINGOF PATHOPHYSIOLOGYAND PHYSIOLOGYTO MEDICAL STUDENTS AT THE UNIVERSITY OF GENT, BELGIUM. J. Weyne and E. l.,aernix Laboratory of Normal and Pathological Physiology, University of Gent, Gent, Belgium. The purpose of pathophysiology is to present a mechanistic view of pathology in order to underscore the disturbances of the normal physiological mechanisms which lead to different diseases and the rationale of their therapeutic approach. In the academic training of a medical student the course of physiopathology is a link between the courses of physiology (and biochemist~) and medecine. Two different approaches therefore exist concerning the way of teaching pathophysiology, which can be presented either as a part of the course medecine, or as an extension of the courses physiology and biochemistry. Clearly, there is a fundamental difference between these two approaches since the clinician, whose medical thinking marts with symptoms to come to a diagnosis, usually has a deductive way of reasoning and an analytical view on pathophysiology, while the physiologist and biochemist, who first develop relevant experimental models to study the effect of a variable parameter, usually have an inductive way of reasoning and a holistio view on pathophysioiogy. Also, from a pedagogical point of view, teaching imthophysioiogy by *looking forward" into mechanisms of disease during the lectures of physiology, is more exciting than teaching mechanisms of disease during the lectures of medecine by "going backward" into basic sciences. That pathophysioiogy and physiology are indeed intermingled is also the view of the Federation of European Physiological Societies (FEPS) since most of the sessions of its 1st congress (to be hold in 1995 in Maastricht, The Netherlands) are planned to cover physiology and
pathophysiology. At the University of Gent, patliophysioiogy is being teached for more than 50 years by not-ciinicians: up to about 1980 as a separate course in the 1st clinical grade, but later in combination with the course of physiology in the 2nd and 3rd preclinical grade. By integrating the pathophysioiogy in the course of physiology, the latter becomes more practically relevant to the medical student. As an example the pathophysiology of pstroduodenal ulcer is reached in connection with the physiology of normal gastric secretion. Also, in the course of the lectures physiology a few seleclml patients are presented, whose symtoms, the pathophysioiogy of their disease, and the principles of its treatment arc discussed by tho (patho)physiologist and thc clinician. In the practical course of physiology, observations on humans (own body or fellow students) arc a substitution for experiments on animal preparations, as an cxamplc, in addition to the classical spirometric measurements of the lung volumes, the single breath nitrogen test is performed, with discussion of uncvcn ventilation, possible air way closure and calculation of residual volume, and eloclrical stimulation of the ulnar nerve with recording of the EldO of the hypothenar muscles is performed as a substitute for the animal nerve-muscle preparation. The combined teaching of physiology and Imthophyeiulogy, of course, assumes a medical training of the teacher of physiology, which poses the problem of recruiting new physiologists among the young M.D.'s,
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