| Object: Impaction bone grafting is used to fill bone defects in the clinical, but theamount of filled bone is decided by qualitative judgment, not having a quantitativeindicator. In this study, three different tightness graftings, compared with the densityof cortical bone and cancellous bone, have been done and we expect to get aquantitative indicator of impaction bone grafting, which can provide experimentalbasis for quantitative criteria of bone graft in clinical application.Materials and Method: the first step: three healthy New Zealand white rabbits,weighting2.5~3kg. The average cortical bone density and cancellous bone densitywas measured. Allogeneic cancellous bone, taken from the iliac, femoral condyle andhumeral head, been decellularized and degreased, disinfected by iodophor, wascryopreserved for two weeks. The second step:27New Zealand white rabbits werecompletely randomly divided into A, B, C three groups (n=9). Ringlike bone defect Vwas constructed by trephine at the distal femoral condyle for each rabbit left hind leg.Group A: the degree of grafting tightness is equivalent to the cancellous bone density,that is, of ρ1=1.0ρcancellous bone=0.63ρcortical bone,of bone graft amountm1=0.2225g. Group B: as much as possible bone grafting but for fractures, that is, ofρ2=1.34ρ cancellous bone=0.85ρ cortical bone, of bone graft amountm2=0.3000g. Group C: the tightness between A and B, that is, of ρ3=0.75ρcortical bone,of bone graft amount m3=0.2649g. The third step: Three rabbits ineach group were sacrificed for X-ray photography, Dual-energy x-ray absorptiometrytesting, general observation and histopathology observation at the4th,8th,12th week.The state of bone absorption, new bone trabecula formation and bone-bone graftinginterface was observed by X-ray photography. The gross anatomy observationincludes the amount of sequestrums, the continuity situation of bone graft interface and the texture of the bone graft region. Histopathology observed: the continuity ofbone grafting; the situation of fiber formation, new bone trabecula, inflammatory cellinfiltration; the amount of osteocyte and osteoblast.Rusults: General observation:12weeks after operation. In group A: There isn'tapparent transitional zone between bone grafting area and the surrounding normalbone area. The cut surface of bone grafting area, presents yellow color like the fattissue, mixed with a little grey texture. In group B: The section surface of thegrafting region, with gray texture and yellow texture interlaced, presents grayishyellow. In group C: What present is like group B.Histopathological observation:4weeks after operation.In group A: in the centralbone graft area we observed a large number of atrophic necrotic trabecular boneenclosed with proliferous fibrous tissue and fat necrosis with numerous vacuolus. Ingroup B and C: in the central bone graft region, atrophy trabecular bone, osteoclastreaction, and partial bone and fat necrosis were observed. In peripheral region, there isa large number of newly formed bone trabecula with proliferous fiber tissue,surrounded by numerous osteoblast.8weeks after operation. In group A: in the centralbone graft region, multifocal fat necrosis can be seen; partial filled trabecula atrophyand be broken, at the edge of which fibrous tissue proliferate. In the peripheral area,new bone trabecula accompanying with a few osteoblast was seen. In group B: in thecentral bone graft area, we can see a small amount of atrophy bone trabeculasurrounding by proliferating fiber tissue and new bone trabecula crossing fiber tissue.New bone trabeculas were partial surrounded by osteoblast. In group C: in the centralbone graft area, some remnants of the atrophy trabecular bone, fat limitation necrosisand fibrous tissue hyperplasia were seen, with a few inflammatory reaction.12weeksafter operation. In group A: in the central bone graft region, partial fibrous tissueproliferation, the outline of multifocal fat necrosis and the remnants of atrophy filledtrabecula can be seen, at the edge of which new bone trabecula be transitional tofibrous tissue. In the peripheral area, new bone trabecula accompanying with a fewosteoblast was seen. In group B and C: in the central region of bone graft, a smallamount of atrophy trabecular bone surrounding by hyperplasia fibrous tissue was seen. In the peripheral region, new trabecular bone was significant proliferationsurrounding by reactive new bone trabecula with numerous osteocyte.X ray photography:4weeks after operation. A distinct boundary line was seenbetween peripheral normal bone and the bone graft region of which density was lessthan normal bone. In group B, there isn't a apparent boundary line between peripheralnormal bone and the bone graft region of which partial high density area can be seen.In group C, a boundary can be seen.8weeks after operation. In group A: An apparentboundary line was seen between peripheral normal bone and the bone graft region ofwhich density was slight less than normal bone. In group B and C: the density of bonegraft region is similar with the normal bone and there isn't an apparent boundary linebetween them.12weeks after operation. In group A: An apparent boundary line can beseen between peripheral normal bone and the bone graft region of which density wasslight less than normal. In group B and C: the density of bone graft region is similar tothe normal bone and the trabecular line is continuous to the normal.Dural energy X-ray absorptiometry observation: At the4thweek: A, B, Cpairwise comparisons, P value<0.05, indicating that there are significant differences.At the8th,12th, week: Between group A and group B, C, P value<0.05, difference issignificant; between B and C, P value>0.05, showing that B, C group have nosignificant differences.Conclusions:1) close impaction bone grafting and closer impaction bone grafting arebetter than no-close impaction bone grafting in histological and photography findings.2) when the tightness degree ρ=1.34ρcancellous bone=0.85ρcortical bone, we can achieve close impaction bone grafting.3) According to the report of literature combined the experimentalobservations, closely impaction bone grafting can provide better inntial mechanicalstability. |
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