Bioactive glasses form a surface apatite layer in vivo that enhances the formation and attachment of bone. Sol-gel Bioglass graft material provides greater nanoscale porosity than bioactive glass (on the order of 50-200 A), greater particle surface area, and improved resorbability, while maintaining bioactivity. This study histologically and biomechanically evaluated, in a rabbit model, bone formed within critical-sized distal femoral cancellous bone defects filled with 45S5 Bioglass particulates, 77S sol-gel Bioglass, or 58S sol-gel Bioglass and compared the bone in these defects with normal, intact, untreated cancellous bone and with unfilled defects at 4, 8, and 12 weeks. All grafted defects had more bone within the area than did unfilled controls (p < 0.05). The percentage of bone within the defect was significantly greater for the 45S5 material than for the 58S or 77S material at 4 and 8 weeks (p < 0.05), yet by 12 weeks equivalent amounts of bone were observed for all materials. By 12 weeks, all grafted defects were equivalent to the normal untreated bone. The resorption of 77S and 58S particles was significantly greater than that of 45S5 particles (p < 0.05). Mechanically, the grafted defects had compressive stiffness equivalent to that of normal bone at 4 and 8 weeks. At 12 weeks, 45S5-grafted defects had significantly greater stiffness (p < 0.05). At 8 and 12 weeks, all grafted defects had significantly greater stiffness than unfilled control defects (p < 0.05). In general, the 45S5-filled defects exhibited greater early bone ingrowth than did those filled with 58S or 77S. However, by 12 weeks, the bone ingrowth in each defect was equivalent to each other and to normal bone. The 58S and 77S materials resorbed faster than the 45S5 materials. Mechanically, the compressive characteristics of all grafted defects were equivalent or greater than those of normal bone at all time points.

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Unilateral, 11 mm diameter, 25 mm deep cylindrical defects were created in tibial subchondral bone of anesthetized goats (n = 16) and filled with autograft or beta-tricalcium phosphate particles. The contralateral limbs served as internal controls. Goats were killed at 3 months and both tibiae harvested. Molds made of the tibial plateau surface were used to create positive casts from which medial and lateral tibial plateau surfaces of both experimental (beta-tricalcium phosphate particles, autograft) and control limbs were digitized in 3 dimensions. Mirror images of the medial condyle surface contours from the controls were superimposed onto the experimental surfaces and deviations were compared using a Student t test (alpha = 0.05). Tibiae were then cut sagittally into medial (biomechanics) and lateral (histology) halves. Compressive modulus within the defect area was assessed by indentation to 2.0 mm at 0.2 mm per second using a 6-mm diameter pin. Specimens from the lateral tibial plateau were processed for undecalcified histology and the area of bone within the defect region measured. The articular surface of 86% of the autograft and 0% of the beta-tricalcium phosphate particles group had degenerative changes, with 29% of autograft goats exhibiting large-scale plateau collapse. Mean surface deviation for autograft was significantly greater than for beta-tricalcium phosphate particles (2.19 +/- 1.49 mm versus 0.78 +/- 0.19 mm), as was maximum surface deviation (11.19 +/- 8.02 mm versus 4.39 +/- 1.33 mm) (P < 0.05). The compressive modulus within the defect area for control animals was significantly higher than the experimental groups (P < 0.05). Significantly more bone was regenerated within beta-tricalcium phosphate particle-grafted defects compared to autograft (P < 0.05). These results indicated that beta-tricalcium phosphate particles might be a useful graft material for local repair of load bearing skeletal sites such as depressed tibial plateau fractures.

Summary:Bioactive glasses form a surface apatite layer in uivo that enhances the formation and attachment of bone. Sol-gel Bioglass graft material provides greater nanoscale porosity than bioactive glass (on the order of 50-200 A), greater particle surface area, and improved resorbability. while maintaining bioactivity. This study histologically and biomechanically evaluated, in a rabbit model. bone formed within critical-sized distal femoral cancellous bone defects filled with 4SS5 Bioglass particulates, 77s sol-gel Bioglass. or 58s sol-gel Bioglass and compared the bone in these defects with normal. intact, untreated cancellous bone and with unfilled defects at 4, 8. and 12 weeks. All grafted defects had more bone within the area than did unfilled controls (p < 0.05). The percentage of bone within the defect was significantly greater for the 4585 material than for the 58s or 77s material at 4 and 8 weeks (p < 0.05), yet by 12 weeks equivalent amounts of bone were observed for all materials. By 12 weeks, all grafted defects were equivalent to the normal untreated bone. The resorption of 77s and 58s particles was significantly greater than that of 4585 particles (p < 0.05). Mechanically, the grafted defects had compressive stiffness equivalent to that of normal bone at 4 and 8 weeks. At 12 weeks, 45SS-grafted defects had significantly greater stiffness (p < 0.05). At 8 and 12 weeks, all grafted defects had significantly greater stiffness than unfilled control defects (p < 0.05). In general, the 45S5-filled defects exhibited greater early bone ingrowth than did those filled with 585 or 77s. However, by 12 weeks, the bone ingrowth in each defect was equivalent to each other and to normal bone. The 58s and 77s materials resorbed faster than the 45S5 materials. Mechanically, the compressive characteristics of all grafted defects were equivalent or greater than those of normal bone at all time points.Some osseous defects and fractures may require supplementation to support and promote healing. An assortment of animal models has been used to investigate many biomaterials as potential bone grafts, with varying success.Autograft is clearly the gold standard; however, the limited graft supply and postoperative donor site morbidity are problematic (15,39). Allografts and freshfrozen and demineralized bone matrix have proved effective (9,15,30,35) yet carry the theoretical risk of disease transmission (1,37). Many synthetic materials have been investigated for the regeperation of skeletal tissue, including hydroxyapatite (3,4,18,26), tricalcium phosphates (4,18,26), calcium sulfate (2,24), polymers (14,20,27), bioactive glass (12,28,31,38,40), and collagen sponges impregnated with growth factors (6,44). Each graft material has been shown to have advantages and disadvantages.Bioactive glasses are of particular interest due to their unique capacity to form a thick apatite gel layer on the particle surfaces that attracts osteoprogenitor cells and osteoblasts (19). A very strong bond is formed between the bone tissue and the gl...

OVX is known to reduce cancellous bone mass and strength, but the effect of OVX on healing of fractures in cortical bone is controversial. This study, using a delayed-union model, found no significant differences between OVX and SHAM animals in the breaking strength of healing fractures.