Application Of CAD And β-TCP Scaffold In The Repair Of Canine Segmental Bone Defect

Background and AimSegmental bone defects due to reasons such as trauma,inflammation and tumors are becoming increasingly common.Presently the accepted treatment of choice for segmental bone defects is bone transplantation.But the limited amount of implant resource,implant rejection and an unmatched shape affects the treatment results.CAD/3D printing and bone tissue engineering have provided new insights in the repair of critical bone defects.This study explores the personalization of the bone defect repair upon establishing a large animal model using beagles,and explores the osteogenesis patterns and efficacy of using a β-TCP scaffold,to provide technical guidance and experimental basis in the clinical treatment of bone defects.Methods1.Three 1 year old male beagles were CT-scanned and analyzed digitally.With CAD,a bone defect model as well as the treatment method plan including a set of personized instruments were designed and then printed.A comparative study with and without the personalized instruments was performed.By recording the surgical time and accuracy of the locking nails,the precision of CAD was verified.A segmental bone defect model and internal fixation was performed.Postoperative signs and radiology were recorded to evaluate the efficacy of the treatment method.2.A CAD-modified β-TCP scaffold was manufactured using 3D printing.Twenty-seven1 year old male beagles were divided into three groups and underwent regeneration-repair study:the control group(negative/positive)and the study group(β-TCP scaffold).Vital signs,biomarkers,radiological studies and tissue histology were recorded up to 24 weeks postoperatively and analyzed.Results1.The mean operated bone length,mean diameter of the medullary cavity and midfemoral cortical length were 135.39±6.09 mm,5.15±0.34 mm,13.65±1.67 mm respectively.The length of the personalized intramedullary nail in the study was 120 mm,and the diameter of the distal portion were separate into two groups of 5mm or 5.5mm.During the surgical emulation,the surgical time and accuracy of the locking nails with and without the personalized instruments were 26±4.6min/40.6±14.1min and 98.3±5.37%/71.6±23.6% respectively,and was statistically significant(P<0.05).Construction of the bone defect model and fixation was performed effectively.2.There were no fatalities in the twenty-seven beagles and they resumed ambulation after4 weeks.Postoperative radiographs showed stable intramedullary nails without loosening or malpositioning.Inflammatory indices,cardiac,renal and liver functions returned to normal levels after 1 week.Bone markers showed significantly increased osteogenesis from weeks 4to 12,and osteolysis most evident in the autologous bone implant group(P<0.05).The anatomical observation of all three groups showed a normal line of gravity and no evidence of implant rejection.CT,micro-CT and tissue sections showed a progressive increase of osteogenesis from 4 to 24 weeks,most evident in the autologous bone(P<0.05).Osteogenesis was most prominent on the surface of the autologous bone and proximal osteotomy site.The β-TCP group showed more osteogenesis compared to the negative control group(P<0.005).Osteogenesis of the β-TCP group was abundant in the porous layer and most prominent in the distal osteotomy site.The scaffold degraded at a rate corresponding to osteogenesis.Osteotomy of the negative control group was blocked by fibrous tissue,and was most prominent in the distal osteotomy site,showing the poorest repair among three groups.Conclusion1.The use of CAD in establishing a beagle critical bone defect animal model was more evidence-based and showed better repeatability.This provided a basis of a stable repair method,for the clinical treatment of critical bone defects.2.The porous β-TCP scaffold showed potential as an alternative material in the treatment of critical bone defects though osteo-conductive.3.Distribution of stress in bone defects may stimulate regional osteogenesis.