Design Of Limited Contact Femoral Supracondylar Interlocking Intramedullary Nail And Study On Mechanism Of Fixation

Skeletal allograft is now widely used to restore bone stock especially during joint reconstruction and for limb salvage after tumour resection. Despite this popularity, a number of issues regarding its biology, processing and safety remain unresolved.The allograft-host bone junction heals slowly and formation of new bone mainly comes from host bone. Thus.methods of fixation are required which provide the stability what bone union needed and the durability to withstand complex load forces over the longer healing time,and blood supply as well as biomechanical characteristics must be highly concerned. It is the objective of this research that to diminish distinction to blood supply of bone and search a better method of fixation that may be more suitable to bony biomechanical characteristics.In this research.we have carried out three experiment: l)Newly designed femoral supracondylar interlocking intramedullary nail were performed which is solid center rod with clover leaf cross-section and can be connected with artifical cartilages of femoral condyles designed before through Moser's cone angles which can be self-locked.There are a few helix-shaped chutes along its surface.This design is regarded to decrease the area between nail and internal surface of bone and enlarge the intramedullary volume. The axial direction and curvature were fixed on by means of CAD system in order to adapt to biomechanical characteristics of bone. 2) Finite Element Method(FEM) were performed to analysis the stress of bolts .intramedullary nails and bone while the bolts were implanted in different angulations-0?15?30?45及? 60?3) An massive allograft transplantation model of pigs wre established with supracondylar interlocking intramedullary nails fixation.Affection to allgraft-host healing and microcirculation of bone were measured dynamically by using X-ray films,prepared Chinese ink microarteriography and tissure slice examination.4) Obique insertion of bolt and limited contact nails were applicated in clinical patients to test its superiority during the processing of massive allograft healing.The results of FEA show that the stress of bolts ,bone and nails with 15?insertion angles of bolt is the tiniest and well distributed. Stress of bone with 0癷nsertion angles is more obvious than 15?30癮nd 45?The more the angles ,the stress of proximal bolt became more obvious and the stress of distal bolt decreasing.X-ray films,prepared Chinese ink microarteriography and tissure slice examination show that affection of limeted contact nails to allograft-host healing and revascularization of bone is smaller than non-chuted nails.Healing of allograft-host with limited contact nails fixation is faster than non-chuted nails,and the density of bony callus is higher than that of non-chuted nails.After analysising the results ,we consider:l)Definiteing the axial direction and curvature of intramedullary nails by means of CAD system during designing the shape of nails is coincident with bony biomechanical characteristics and adapted to the requirement that custom-made needed.2)When inserting the bolts,the stress with 15癷nsertion angles is the tiniest and well-distributed.3)Obique insertion of bolt may be better choice in massive allograft transplantation fixed with intramedullary nailing.4)The femoral suprocondylar intramedullary interlocking nail decreased the area between nail and the internal surface so as to minish the destruction of blood supply of bone and be advantageous to allograft-host healing.