Effect And Mechanism Of Fracture Healing By The Novel Dynamic Compressive Interlocking Intramedullary Nail

BackgroundFracture healing is the eternal topic in the basic research of orthopedic trauma.According to reports, the5%-10%of the incidence of postoperative nonunion or delayedunion fracture patients. Their reasons, not just because of the complexity involved in thisprocess of tissue biology, more about the repair process influenced by many factors, andinternal interactions between these factors jointly regulate the process of fracture healing.In recent years, with the deepening and development of biochemistry and biomechanicsresearch, most scholars share the view that the participation of stress is one of the importantfactors affect fracture healing process. Favorable stress loading will actively promotefracture healing process, to the contrary, it may cause nonunion or delayed union, and evencause new bone damage. Experimental studies have shown that applied parallel to the longaxis of the axial compressive axial stress and stump micro conducive to fracture healingbetween the fracture fragments. However, how to achieve bone healing process in theaxial compressive stress and micro-fracture model and how to optimize the combination oftwo favorable factors, or even be after loading fracture tissue healing and what impact isthe current clinical orthopedic applications the focus of basic research. To this end, ourgroup is based on many years of orthopedic trauma treatment experience, on the basis toovercome the the traditional interlocking intramedullary nail long-term static fixedshortcomings, designed and developed with independent intellectual property rights can berealized the automatic compression fracture fragments and axial micro dynamic newautomatic pressurized interlocking intramedullary nail, by the finite element methodanalysis of the mechanical properties and applied clinical animal studies, in order tounderstand its impact on fracture healing, thereby analysis of dynamic axial compressivestress on fracture healing the process may affect the mechanism. ObjectiveRetrospective study of clinical cases, it is one of the important reasons of nonunion ordelayed union of the traditional interlocking intramedullary nail postoperative separationbetween the fracture fragments. Has confirmed the novel automatic pressure interlockingintramedullary nail bridging the fracture gap and achieve the function of the axialcompressive stress fracture fragments. Compared with the traditional interlockingintramedullary nail has a promote fracture healing effect. And thus Preliminary Analysis ofthe dynamic axial compressive stress on the impact and possible mechanisms of fracturehealing process mechanics theoretical basis and practical foundation for the clinicaltreatment of long bone fractures.MethodCollect17cases of patients with postoperative nonunion, which treated by interlockingintramedullary nail during the period from August2005to May2008, retrospective studyto analyze the postoperative bone nonunion complications possible reasons. According tothe above reasons, combined with years of experience in the treatment of fractures traumaof the unit, design and R&D to achieve automatic compression fracture fragments andmicro interlocking intramedullary nail, and finite element analysis to demonstrate its abilityto achieve fracture fragments axis to jog the compressive stress and the function of reducingthe fracture gap. Finally, apply clinical animal studies with this pressure interlockingintramedullary nail, through the settings pressurized group and the control group comparedto observe and detect five different fracture healing phases, fractures callus histology andfactor expression change into bone cells, new automatic pressurized interlockingintramedullary nail further confirmed by increased cytokine release into bone cells, affectfracture healing process. The typical picture used to represent the qualitative results,application SPSS15.0software to do statistical analysis, P <0.05was consideredstatistically significant.Result1. The clinical retrospective study on the traditional interlocking intramedullary nailtreatment of long bone fractures occured postoperative nonunion or delayed fracture healing complications cases, suggesting that the fracture stress absorption, hardening andseparation phenomena, may lead to local bone tissue contact the area is reduced, hinder theestablishment of micro-circulation and other issues to reduce the fracture gap distance,through the replacement of internal fixation devices, supplemented by local add intoosteoinductive factors to improve the adverse conditions, and be able to get the bonehealing.2. The research group to design and research and development of the novel automaticpressure interlocking intramedullary nail finite element modeling and analysis, proven tobe effective to shorten the gap distance of the fracture fragments and the pressure generatedby the spring axis through the proximal locking nail conduction to the compressive stress tothe fracture stress of excessive concentration of local stress concentration, and can reducethe main nail and the distal locking screw, axial micro fracture fragments at the same time.traditional interlocking intramedullary nail does not has such mechanical properties.3. The comparison of histological observation, confirmed by the novel automaticcompression interlocking intramedullary nail axial compressive stress earliest postoperative14d endochondral bone, and the pressure group the number of early and mid callus,interim good quality and late callus high degree of maturity, bone trabeculae more rules,the Haversian system structure is relatively complete.4. The markers extracellular matrix of osteoblast--type I collagen and osteocalcinexpression were detected, confirmed that both mRNA and protein secretion and expressionin fracture surgery increased,14d,30d after phase point reaches its peak, the pressuregroup was significantly higher than that in the control group, a statistically significant (P<0.05).Conclusion1. Traditional interlocking intramedullary nail for femoral shaft fractures postoperativestress bone resorption separation caused stump, lead to a decrease in the contact area of thefracture may be one of the important reason for nonunion or delayed union.2. The novel automatic pressure interlocking intramedullary nail can effectively reducethe fractures gap at both ends, and in the formation of axial compressive stress fracture, re- allocation of the physiological load stress, to achieve axial fretting between the fracturefragments.3. The novel automatic pressure interlocking intramedullary nail can significantlypromote cartilage the callus matrix of calcification in the fracture gap,endochondral bone,and the preparation of bone remodeling, to promote osteoblast extracellular matrixsynthesis, secretion and endochondral bone, effectively accelerate fracture healing process,improve the rate of bone healing.4. Axial compressive stress applied to the fracture fragments and Micro movement，can generate, deformate and conducte a biomechanical environment in the fracture stressloading locally, also Chemoattracte and promote the osteogenic effect cells involved in therepair process of fractures.