Osteoarticular Allgraft With Distal Segment Partial Demineralized For Repairing Large Osteoarticular Defects

Objective : It remains a difficulty to repair the osteoarticular defects after the tumor resection. Though the defects can be repaired by several methods ( including arthrodesis , prosthesis , osteoarticular allograft , etc.) ,all the methods have advantages and disadvantages . Nowadays , massive osteoarticular allografts are used commonly ,but they have been found to incorporate slowly into host bone thus are subject to complications such as nonunion ,delayed union, and fatigue . Demineralized bone has already been found that it can improve the osteoinduction of bone allografts, but it could not be applied to the osteoarticular defects because of the reduction of mechanical property .To improve the process of osteoinduction of osteoarticular allograft , a new experimental model was developed with use of frozen osteoarticular allograft with thedistal segment partial demineralized from New Zealand white rabbits'radius. Two types of osteoarticular allograft were analyzed : Type I , frozen osteoarticular allograft with the distal segment partial demineralized ; Type II , frozen osteoarticular allograft . The two type of osteoarticular allografts were fixed with Kirschner wire used as an intramedullary nail to repair the massive osteoarticular defects . The results was evaluated with plain films , gross specimen, histological examination and bone scintigraphy at the 4,8,12 weeks postoperatively . This study is to explore the difference of incorpration of the two types of osteoarticular allografts. to find a better way of ostearticular allograft.Materials and Methods : 48 mature New Zealand white rabbits were selected as the animal model . The osteoarticular allograft about 20 mm long was excised by hacksaw from the proximal portion of radius obtained from other 24 rabbits of the same strain.( from the SHANDONG ACADEMY OF AGRICULTURL SCIENCES ). The grafts were procured aseptically and stripped of atached soft tissues, including theperiosteum and ligaments and muscles. The marrow was removed by repeated washings of the intramedullary canal with saline.The two types of osteoarticular allograft were implanted in osteoarticular defect : Type I --The left osteoarticular allografts were demineralized at the distal end about 5 mm long by 0.6 M HCL at 4°C about 4 hours, then cryopreserved(-80 °C )for at least 2 weeks. Type II --not demineralized , merely cryopreserved for at least 2 weeks.Then the two type of osteoarticular allograft were implanted orthotopically in another 24 New Zealand white rabbits after removal of a 20 mm long segment from the proximal radius. Fixation of the osteoarticular allograft was achieved with Kirschner wire used as an intramedullary nail and two piece of thread. The results was evaluated with plain films , gross specimen, histological examination and bone scintigraphy at the 4, 8, 12 weeks postoperatively .Results: The scoring outcome of radiological and histological analysis between the experimental and control side at the 4 , 8 , 12 weeks shows that the process of parialdemineralization at the distal segment of the osteoarticular allograft was significant in enhancing bone incorporation at the sites of graft-host bone junction.ECT showed that bone metabolism was more active in the 4 weeks and became stable in the 8 and 12 weeks postoperative. The bone metabolism of distal segment of the osteoarticular allograft of experimental side was more active than that of control side.Conclusions: 1. Partial demineralization at the distal segment of the osteoarticular allograft can accelerate the incorporation of the graft-host junction and reduce the complications such as nonunion , delayed union.2. The massive frozen osteoarticular allograft with distal segment partial demineralized has highly osteoinductive properties and low antigenicity and maintenance of mechanical properties. It is fit to repair the massive osteoarticular defect.