The influence of local application of haemostasis, peripheral blood, autologous bone marrow and Fibrin Adhesive System (FAS) on bone formation rate in osseointegrated titanium implants, were studied. The Bone Harvest Chamber (BHC) implant utilized has a penetrating canal, enabling osseous ingrowth in situ. After integration of one implant into the cortex of the proximal tibial metaphysis of a rabbit, newly formed bone was harvested in repetitive three-week periods. The specimens were quantified by microradiography-videodensitometry and subjected to further histological examination. The amounts of bone formed in two equally treated chambers in the same animal were compared. It was concluded, that the conditions for bone regeneration in an osseointegrated titanium implant are excellent, minimally influenced by locally applied haemostasis, peripheral blood and autologous bone marrow. FAS pretreatment on the other hand was found to impair bone formation.
The delrin Bone Growth Chamber (BGC) which is a dividable implant, was inserted in its assembled form in the tibial metaphysis of the rabbit. The BGC allows a numerical estimation of the bone growth into the implant, based on microradiography and microdensitometry that permits evaluation of direct current (DC) effects on bone regeneration. A test chamber was inserted in one tibia and was stimulated with either 5, 20 or 50 microA for three weeks, while on the contralateral side of the same animal, a control implant was inserted under identical conditions as the test, but was not stimulated. The results showed a significant increase of bone growth with 20 and 50 microA and a tendency towards more bone formation with 5 microA.
Electrical stimulation with a DC of 5 microA was found to result in macromolecular leakages in the microcirculation of rabbit metaphyseal bone. The blood flow rate of living bone did not change during 2.5 hours of electrical stimulation. Over a follow-up time of up to 11 weeks it was observed that vessels close to bone borders increased in size and that the number of bone capillaries increased, simultaneous with an increase in bone formation.
Vital microscopy during electrical stimulation was performed in the hamster cheek pouch and the rabbit tibia. Stimulation with DC of 5,20 or 50 microA or AC of 20 microA was demonstrated to cause macromolecular capillary leakage as evidenced by FITC-dextran fluorescence and histological demonstration of extravasated white blood cells. It was further demonstrated that the vascular leakage was blocked by administration of indomethacin. Pulsed electromagnetical fields did not visibly affect the vascular permeability within 3 h. As the same DC electrical stimulator has been demonstrated to increase the osteogenic capacity in similar titanium implants in the rabbit tibia, it is suggested that the observation of macromolecular leakage may predict a positive osteogenic response.
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