| Popis: |
The utilization of electrical energy in the treatment of orthopaedic disorders such as fracture non-union is becoming established, and the use of pulsed magnetic fields (PMF's) to induce current in the required region is increasingly popular since it is electrically 'safe' and surgically non-invasive. Paradoxically, to date, this technique remains the least researched on a biological basis. Consequently, the effects of PMF's on embryonic-chick bone rudiments and adult human fracture non-union callus in vitro were studied. Using 7-d embryonic tibiae cultured for 7-days, it was shown that PMF's (applied continuously), significantly reduced 3H-proline incorporation whilst h droxyproline (collagen) levels were unaltered as was the incorporation of 3'b5O. PMF's also reduced cAMP levels but the incorporation of H-thymidine was unaffected. It was concluded that experimental treatment selectively inhibited chondrogenesis, and electron microscope observations supported this view. Osteotomised 12-d embryonic-chick tibiae were also used to study osteogenesis and bone repair. It was found that continuous exposure to PMF's for 18 days in vitro, significantly increased the lengths of experimental rudiments. However, there were no marked differences in the rate or pattern of repair. Incorporation of labelled proline, and its conversion to collagen specific hydroxyproline in the chondrogenic epiphyses was unaffected. However, the experimental groups showed markedly reduced levels of hydrolytic enzyme activity and hence presumably, less catabolic label release into the medium. PMF's significantly stimulated non-specific protein synthesis in the osteogenic diaphyses and this was tentatively linked to the stimulation of mineralization which was found in 15-d embryonic-chick mandibular rami exposed to PMF's for 6 days in vitro. Cartilage from adult human fracture non-union callus was cultured successfully, and in vitro differentiation observed. It was also shown, histochemically, that PMF's enhanced calcification of both hypertrophic and fibrocartilaginous callus samples. The biological and clinical implications of the results, and, in particular, the chondrogenic suppression and stimulation of mineralization/calcification processes by PMF's, are discussed. |
