Correlation Between Radiology And Histological Appearance Of Porous β-tricalcium Phosphate Implanted In Ovine Lacunar Bone Defects

Backgrounds and Objective: Bone grafting is often necessary when loss of bone stock resulting from trauma, excision of bone tumor, infection or other pathology. Autograft, allograft and bone graft substitute are commonly used to repair osseous defects. Although autogenous bone is considered the gold standard, to which other methods are compared, autograft has significant limitations, including donor site morbidity, inadequate availability in inappropriate form. Allograft bone has been widely used, which of course have several problems encountered when used, including immunogenicity and disease transmission such as hepatitis and HIV, loss of biologic and mechanical properties secondary to its processing and increased cost. Consequently significant strides have been made to search ideal bone graft substitutes. Various synthetic materials have been developed as bone substitute which include synthetic polymers,inorganic materials and some composites. Beta-tricalcium phosphate has the similar chemical composition with inorganic ingredient of bone tissue and offers excellent biodegradation and biocompatible properties. The small particle size and interconnected microporosity are believed to improve osteoconductive properties of material and promote timely resorption concomitant with the process of remodeling.β-TCP has been researched more and more in vivo of animals and in vitro , but we still do not know its efficacy in bone healing compared with allograft which used commonly in orthopeadics, and the correlation between its radiological appearance and histological appearance in bone repair. Otherwise, researches on repair of osseous defects were concentrated on the repair of segmental osseous defects, lacunar bone defects were ignored. Researchers have found the healing of cancellous bone does not have the same biological behaviour with cortical bone, the defects of cancellous bone are healed through bone trabeculae ingrowths, but not osteogenesis intramembrane or osteogenesis in cartilage which appears in cortical bone healing. The present study wants to: (1)investigate variance of efficacy between porousβ-TCP and freeze-dried bone allograft in bone healing, (2)investigate the correlation between radiological appearance and histological appearance of porousβ-TCP in repair of lacunar cancellous bone defects.Methods and Results:PartⅠ: Lacunar osseous defects which owe diameter of 10 millimeters and depth of 20 millimeters were established at metaphysis, and which owe diameter of 10 millimeters and depth of 10 millimeters were established at diaphysis of long bone in goats'hind limbs. Porousβ-TCP particle(group A), porousβ-TCP powder(group B) and freeze-dried particulate bone allograft(group C) were impacted in the defects, there was also a blank control with nothing impacted(group D). X-ray, CT and histology were made at 4th, 12th and 24th week postoperative. Degradation of the materials used and healing of the bone defects were observed and assessed, then we could compare the efficacy of facilitating bone healing between porousβ-TCP and freeze-dried particulate bone allograft. Radiological photos showed blank group D could not heal spontaneous, group A, group B and group C could get synostosis in X-ray and CT photos. Histological sections showed new bone started grow into the defects at 4th week postoperative and the defects of group A, group B and group C got well healed at 24th week postoperative. Histomorphometry showed percent of newly formed bone was higher in group C than that of group A and group B(P<0.05, with statistic analysis), percent of newly formed bone in group A and group B did not differ from each other(P > 0.05, with statistic analysis). The efficacy of freeze-dried bone allograft is better than that of porousβ-TCP in our study.PartⅡ: The photos of lacunar cancellous osseous defects at metaphysis were taken for another part in our study. Radiological density was measured in each X-ray and CT photo of 4th, 12th and 24th week postoperative. Also percents of new bone formation were taken at each histological section. The results showed radiographic diagnoses of a healed fracture correlated with histological finding of bone healing.Conclusion:In conclusion, lacunar osseous defects with diameter of 10mm and depth of 20mm at metaphysis and defects with diameter of 10mm and depth of 20mm at diaphysis in long bone of goats could not heal spontaneous. The results mentioned above showed that porousβ-TCP could facilitate new bone formation and bone defects healing but its efficacy was not as good as that of freeze-dried bone allograft used in our study. In advanced study,we found radiological appearance correlated with histological finding of bone healing.