Biomedical Engineering Reference
In-Depth Information
the presence of TCP at the site of the fracture appeared to favor the
union [189]. Furthermore, Key [191] suggested that “if a defect in
bone could be filled by a non-irritating, slowly soluble mass, which
was porous and which contained calcium phosphate and carbonate
in a form in which they could be resorbed, it would be reasonable to
expect osteoblasts to invade the mass, utilize the calcium, and build
new bone which would replace the mass of calcium and cause the
bone to be restored to its original form. The ideal material would
appear to be rather dense cancellous bone from which a large
percentage of the organic material had been removed.” (p. 176).
However, Key found that “Neither calcium phosphate and carbonate
in the proportions in which they occur in bone, nor bone powder,
made by removing the organic matter from bone, appear to stimulate
osteogenesis of bone when implanted in a bone defect.” (p. 184).
Stewart [190] concluded that “1. Lime salts and boiled bone when
placed into a bone defect with either traumatized muscle or fascia do
not serve as a source of available calcium resulting in supersaturation
of connective tissue and regeneration of missing bone. 2. Live bone
chips placed in bone defects regenerate the missing bone.” (p.871).
Shands [192] also reported conflicting effects of several calcium salts
(calcium glycerophosphate, a mixture of TCP (3 parts) and CaCO
(1
part), bone ash and calcium gluconate) on bone repair. Namely, in
defects in the ulna of dogs, the investigated calcium salts appeared
to stimulate bone formation, while in operations upon the spine,
calcium glycerophosphate did not stimulate bone formation and
appeared rather to exert an inhibiting influence. In 1948, Schram
and Fosdick confirmed the fact that only certain types of calcium
orthophosphates influence the bone healing process [193]. Similar
conclusions were obtained in 1951 by Ray and Ward [194].
In 1950, the history of calcium orthophosphate cements was
started [195]. The author of that important publication investigated
mixtures of both oxides and hydroxides of various metals with
aqueous solutions of orthophosphoric acid and discovered a number
of cold-setting formulations. For example, he found that CaO, sintered
at 1100°C, did not set in H
3
, while that in liquid containing 9.6%
CaO was found to set after ~ 12 h in presence of H
PO
3
4
[195]. The
latter mixture might be considered as the first prototype of self-
setting calcium orthophosphate cements (Chapter 5); however, the
real history of this subject started in 1982.
PO
3
4
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