Studies of flexible plates made of plastic have shown that less
osteoporosis develops beneath them than beneath rigid metal plates.
However, to date plastic plates of appropriate physical properties and
biocompatibility are not available for use in humans. To determine if a
similar beneficial effect could be obtained using metal plates, the effects
of thick chromium cobalt plates were contrasted in experiments in dogs with
the effects of thinner plates of similar design made of titanium,
6-aluminum, 4-vandium. A significant reduction in the osteoporosis was
obtained by use of the more flexible plates. Following plate application a
delayed, massive, transient stimulus to bone formation occurred
endosteally, periosteally, and intracortically. Despite this, a substantial
decrease in bone mass occurred, primarily mediated by endosteal bone
resorption. Intracortical porosity played little or no role in net bone
loss. The major effects subsided by six months. Recovery after plate
removal was predominantly the result of endosteal new-bone formation.