The Effect Of Stimulation With Pulsating Pressure Of Different Intensity On The Repairing Of Bone Defect

With the development of society, the trauma transforms in the form of low-energy traumapast into today’s high-energy injury, it brings unprecedented challenges to treat fractures.How to promote fracture healing, and reduce the incidence of delayed fracture healing ornonunion of bone fracture become a hot research field. Studies have found that bonetissue mechanical adaptability, appropriate mechanical stimuli has obviously osteogeniceffect, however, its mechanical adaptation mechanisms are not yet fully undstand,currently the theory of Interstitial fluid flow-induced fluid shear stress in thelacunar-canalicular system (LCS) is widely accepted.Through the studies of normalphysiological on human motor system shows that when exercising, the pumping actionof skeletal muscle can improve the hydrostatic pressure of the bone’s capillary, therebyenhancing the Interstitial fluid filtration in LCS and then improving bone tissueInterstitial fluid flow-induced fluid shear stress. How to make skeletal muscle continueto play its role as muscle pump in the state of fractures to achieve the purpose ofpromoting fracture healing becomes a new idea of studying fracture physical therapies. Based on the above theory we developed a device of pulsating pressure stimulation invitro, and through the study to confirm that the device can improve the arterial bloodpressure on partial forelimb, and by comparing The effect of stimulation with pulsatingpressure of different intensity on the repairing of rabbit radial defect, and to provideexperimental basis for selection of appropriate pressure intensity. The study is dividedinto two parts:Experimental1: Study of the mechanisms of pulsating pressure of different intensityObjective To validate the effect of pulsating pressure stimulation in vitro with differentintensity on arterial blood pressure of pig’s partial forelimb, then indirectly infer theimpact of the device on the Interstitial fluid flow in LCS. Methods Mature white pigs6,Using the method of invasive arterial blood pressure monitoring on the porcine radial artery, afterpuncturing under direct vision successfully, connected the needle with fluid-filled system andelectronic system of the invasive arterial blood pressure monitoring system, recorded themean arterial pressure and waveform on the state of resting. Then given5~7Kpa,8~10Kpa,11~13Kpa pulsating pressure stimulation in the proximal forelimb, while thepressure is stable, it was continued to be given5minutes and recorded the mean arterialpressure and waveform every1minutes. Results The mean arterial blood pressure of theexperimental group increased with different gradients, the difference was statisticallysignificant (P<0.05). Conclusion The divice of pulsating pressure stimulation In vitrohas a significant impact on the local pig’s forelimb radial arterial blood pressure levels.Experimental2: The effect of stimulation with pulsating pressure of different intensityon the repairing of rabbit radial defectObjective To compare The effect of stimulation with pulsating pressure of differentintensity on the repairing of rabbit radial defect, and to provide experimental basis forselection of appropriate pressure intensity. Methods A total of64New Zealand rabbits were selected to build radial defect model with a length of5mm, and randomlydivided into4groups (n=16). In the control group, the defects were repaired naturally,the others received the pulsating pressure stimulation with different intensity30minuteseach day on the4th day after the surgery, the frequency of the stimulation was15Hz, andaccording to the intensity the experimental groups were settled as: group5～7KPa;group8～10KPa; group11～13KPa. The drawn points were settled at2weeks and4weeks,8rabbits were killed each group at every drawn point. After2weeks and4weeks,each rabbits was examined by X-ray radiography, each rabbits was tested by Tetracycline-calcein fluorescence double labeling after4weeks. New bone formation was testedamong the4groups by gross observation, micro-CT analysis and Histological staining.Results General observation of the specimens both at2weeks and4weeks aftersurgery: there was more new bony callus filled with the defects of group8～10KPa thanthat of the other three groups. X-ray radiography at2weeks after surgery showed that thebone defects of each group were still visible, but there was a mass of lamellarhigh-density shadow in the bone defects of group8～10KPa, the other three groupshave no or only a little lamellar high-density shadow in the bone defects; X-rayradiography at4weeks after surgery showed the bone defects of each group were filledwith a large number of high-density shadow, the two ends of the bone defect in group8～10KPa had almost connected completely by new formed bone, but there were acertain of low-density gaps among the bone defects in the other three groups. TheLane-Sandhu X-ray scores were the highest in group8～10KPa, with a significantdifference among the4groups (P＜0.05). The analysis of X-ray grayscale value ofDICOM data showed that the X-ray grayscale value of the bone defect in group8～10KPa is the highest, and there was statistically significant difference compared with theother three groups (P＜0.05). Micro-CT analysis: After2weeks the bone defects of eachgroup only formed a small amount of newborn callus, new bone formation at8~10Kpagroup was obviously more than the other three groups; after4weeks, the defects of eachgroup were filled with a large number of new bone callus, newborn callus has almostcompletely filled the defects of8~10Kpa group, the two ends were not connected completely in the other three groups. Bone morphogenetic analysis after2weeks and4weeks showed: BMD, Tb.N of new bone callus in the8~10Kpa group weresignificantly higher than the other three groups, the difference was statistically significant(P <0.05), The Tb.Sp of8~10Kpa group were significantly lower than the other threegroups, the difference was statistically significant (P <0.05). Van Gieson staining:2weeks after surgery, bone defects in each group were formed fiber connection, there werea little more new trabecular bone in the defects of8~10Kpa group, surrounded bycartilage tissue and fibrous tissue;4weeks after surgery the defects in group8～10KPawere filled with a large number of trabecular bone newly formed, the two ends of bonedefect had been almost connected completely by trabecular bone newly formed; althoughthere was a lot of new bone in the defects of the other three groups, there still exist manyfibrous cartilage, and the two ends of the bone defect were not fully connected either.4weeks after surgery, the calculation of the rate of bone newly formed according to thetetracycline-calcein fluorescence double labeling showed bone defects of8~10Kpagroup repairing rate was significantly faster than the other three groups, the differencewas statistically significant (P <0.05). Bone morphogenetic protein2(BMP-2)immunohistochemical staining of the bone newly formed4weeks after surgery showed,8~10Kpa group was strongly positive, the other three groups were positive or weaklypositive. Vascular endothelial growth factor (VEGF) immunofluorescence staining4weeks after surgery showed,8~10Kpa group was strongly positive, the other threegroups were positive or weakly positive.Conclusion The stimulation of pulsatingpressure in vitro at the range of8～10KPa pressure intensity can significantly promotethe repairing of rabbit radial defect.