We report here the biochemistry of fusion mass consolidation in sheep spines during a 1-year period following autogenous cortical-cancellous bone grafting and stabilization with Harrington distraction rods. Biochemical analysis of vertebral fusion mass included determination of wet weight and dry weight and quantification of glycosaminoglycan, collagen, calcium, and phosphate following extraction with neutral EDTA and proteolytic hydrolysis with papain. Our results showed that at 1 week after surgery, the fusion mass consisted of original cortical and cancellous bone graft material. The cortical bone graft was partially resistant to EDTA-papain treatment, resulting in a residue containing hydroxyproline and mineral. At 12 weeks after surgery, the fusion mass had become a homogeneous material, which, like cancellous bone graft, was completely susceptible to treatment by EDTA-papain. Collagen content of consolidating fusion mass was highest at 16 weeks after surgery when normalized to dry weight; glycosaminoglycan content was highest within 6 weeks after surgery. Mineral content was lowest at the 6-week stage but by 12 weeks after surgery, it was comparable with original bone grafting material. At 24 and 52 weeks after surgery, fusion mass consolidation was characterized by an increase in the proportion of organic and mineral components resistant to EDTA-papain. The appearance of the EDTA-papain-resistant material in the fusion mass coincided with formation of lamellar bone and successful consolidation.

The incorporation of calcium, phosphate, and zinc into the callus of closed tibial fractures was studied in adult rats fed a standard diet. Low doses (60 ng/kg per day) of 1,25(OH)2D3 5 days a week greatly increased early callus mineralization. This was not related to an increased serum calcium-phosphate molar product but rather to a decreased ratio. The incorporation of zinc into callus seemed to be correlated to the mineralization process but not to the 1,25(OH)2D3 administration as such. The question of a direct, indirect, or a complex role of 1,25(OH)2D3 in bone formation and mineralization is discussed.

Thirty-six young rats were used to determine the effect of the fluoride on collagen synthesis in healing of fracture. Eighteen rats received 100 ppm fluoride per day, the other 18 were not given fluoride and were used as controls. Then the tibiae of the 36 rats were successively fractured and the animals killed. That is, the first 14 animals of either group were killed one a day, and then the remaining four animals were killed on days 21, 28, 35, and 45 as the tibiae were fractured. Collagen synthesis of the callus was examined histochemically and histologically. In the fluoride-treated group, collagen synthesis was found to be defective, while it was normal in the controls.

Unilateral tibial fractures were produced in adult, 1-year-old, male Sprague-Dawley rats. The animals were then treated for 6 weeks with daily doses of 2.5 micrograms, 1.25 micrograms or 0.125 microgram 1alpha-hydroxycholecalciferol (1alpha-OH-D3). The aim of the investigation was to study the effect of this treatment on the healing process of the fracture and on the composition of the fractured bone. The general effect of 2.5 micrograms of 1alpha-OH-D3 was a significant loss of body weight (20 per cent) and hypercalcaemia. The lower dose levels, however, did not affect the body weight, and with a dose of 0.125 microgram the serum calcium level did not increase significantly. The healing rate of the fractures increased in all treatment groups as compared with the controls. The water content of the fractured tibias increased in the rats treated with 2.5 micrograms doses but decreased in the other groups. On the other hand the mineral content increased in the groups treated with 1.25 micrograms and 0.125 microgram doses and decreased in the largest dose group. Furthermore the amount of organic material per wet weight increased with the 2.5 micrograms dose and was mainly unchanged in the other groups. The hydrated bone density and the cortical thickness of the tibia increased most significantly in the group treated with 0.125 microgram but the trabecular bone area of the periosteal callus did not increase significantly. The conclusion is drawn that treatment with small doses of 1alpha-OH-D3 has a beneficial effect on the healing rate and on the mineralization of the fracture callus, and on cortical bone formation.

The effect of local application of low fluoride concentrations on the healing of experimental bone-radii fractures in 20 rabbits was examined. No external fixation was required after the osteotomy and gelfoam being used as a medium for fluoride application. Histologic mineral and mechanical strength measurements were carried out on the healing callus. There were no significant changes in the ashpercentage and the fluoride concentration of the ash between the experimental and control callus. A significantly higher percentage of ossified tissue was found in the fluoride treated callus. The breaking strength was found to be significantly higher in the bone fractures treated with fluoride, whereas there was no notable difference between the surface areas. It is postulated that the greater amount of ossified tissues, the differences in organization of the bone trabecules, and/or an improved mineral crystallinity may be responsible for this result.