Experiment Study Of Repairing Comminuted Fracture With Bone Particles Made From Free Avascular Cortical Autograft And Deproteined Xenogeneic Cancellous Bone

Objective: To disucss the effect of repairing comminuted fracture with bone particles madefrom free avascular cortical autograft and deproteined xenogeneic cancellous bone(DXCB)primarily, at the same time, to observe the biologic and mechanics changes of free avascularcortical autograft in different replantation ways, and effect on bone healing.Methods: 18 goats (total 36 tibiae), 12-month-old,no limit on male or female, 15～18kg, weredivided into threes groups: experimental group(free cortical bone particles with diameter0.5～1mm+DXCB),control group A (only DXCB after taking out the local free avascularcortical bone),and control group B(local free avascular cortical autograft). Then thecomminuted fracture associated with local free avascular cortical bone animal models weremade, and grafting and internal fixation were carrying out in the middle part of bilateral tibiaeunder general anesthesia according to the groups. The goats were breed and observedfreely, treated with antibiotics and examed by X-ray postoperatively. At 4, 8, 12 weeks, 2 goatsof each group were killed,and investigations of the fractures healing were made by means ofgross obsvernation, X-ray examination,biomechanics exam by carrying out axialcompression, torsion testing in Biomix MTX858, and histopathology observation. The scoreof X-ray examination and histology observations were graded according to Lane standard.The statistical analysis were carried out by SPSS13.0 finally.Results: All wounds of animal cured primarily. Study of X-ray have shown: at 4 weeks,obvious bony callus image and fuzzy fracture lines appears in experimental group, while thebony callus is more less,fracture lines are clear in control group A, and little callus, corticalfragment still existing in control group B. At 8 weeks, bony callus increased obveriouslyand bony union were observed in experimental group, bony callus increased in control groupB too, but density is inhomogenous, high-density image of cortical fragment still existing. At12 weeks newborn cortex bone structure appeared and linked with host cortical bone, themedullary cavity appeared again, fracture area repaired completely. Much bone callus wereobserved in control group A, but no cortex bone structure; It can be seen that a little callusgrowth in control group B, border were more blurred, cortex bone transplanting area density is still high. The score of X-ray examination at all times were graded according to Lanestandard, and the result showed that the quality and quantity of new bone formation werestatistical different bewteen the experiment, the control group A and B(P＜0.05).The stiffnessof fracture healing was detected by biomechanics. Among experiment group, control group Aand B, distinct difference (P＜0.05) were found in hardscale of vertical compression, torsionat post-operatively immediately4, 8 and 12 weeks,and it were showed: experiment group＞control group A＞control group B. The histopathology observation: at 4 weeks,fibrous,obvious vascular proliferation and chondrocyte, mesenchymal cell, much callus were found inexperiment group; much fibrous tissue and little callus in control group A; sequestrum fromfree avascular cortical autograft and Absorption phenomenon were found in control group B.At 8 weeks, woven bone and lamellar bone appeared while bone particles and DXCBdegraded partly in experiment group; much fibrous tissue and little callus in group A;sequestrum, distinct bone absorption and little callus still observed in group B. At 12weeks, much lamellar bone, cortical bone and bone marrow were found in experiment group;immature new bone increased and little DXCB still existed in group A; some callus and smallsequestrum can be observed in group B. Distinct difference among three groups were found inhistopathology according to Lane standard (P＜0.05), the order showed: experiment group＞control group A＞control group B.Conclusions: Bone particles made from free avascular cortical autograft (diameter 0.5～1mm)have functions of direct osteogenesis and inducing osteogenesis, can boost fracture healing.The compound transplantation of them can efficiently repair bone defect or comminutedfractures, and its repair capability is better than DXCB or free avascular cortical autograftalone both in quantity, quality and mechanical strength of bone formation. Replantentaion offree avascular cortical autograft bring bone healing adverse effect.