Comparative Study For The Effects Of Three Orthopedics On Femoral Fracture Healing In Canine

Orthopedic diseases account for about 70 % of surgical diseases in small animals,while femur fracture accounts for about 30 % of that.There are many reasons that cause fractures,90 % of them are caused by external forces,including traffic accidents,falling from higher positions,being rolled over by vehicles,pressed by heavy objects.Surgical treatment can reduce pain and restore motor function in a short time.Bone plate,Intramedullary nail(IMN)and External skeletal fixator(ESF)are common orthopedics in veterinary clinic,but each of them has its own advantages and disadvantages.The aim of this study was to establish a canine femoral fracture model,then treated respectively by Dynamic compression plate(DCP),IMN plus ESF,and trans-interlocking intramedullary nail(TIIMN).After operation,X-ray imaging analysis,determination of inflammatory factors and bone healing cytokines,bone biomechanical test and bone histology analysis were used to comprehensively evaluate the effects of the three orthopedics on fracture healing,so as to provide valuable reference for the clinical treatment of canine femoral shaft fracture.Twelve dogs aged about 1.5 years and about 15 kg weight were randomly divided into 3 groups with 4 dogs in each group.Group A designed for DCP,group B for the combination of IMN and ESF,and group C for TIIMN.The operative duration,intraoperative blood loss,incision size,time to begin weight bearing and complication rate in the three orthopedics were compared.Blood cell counts and biochemical tests were performed before and at 1,2,4,7,9 and11 weeks postoperatively.Peripheral blood mononuclear cells(PBMCs)were prepared at 2,4,7 and 11 weeks postoperatively,and m RNA levels of inflammatory factors(including IL-6,IL-8,IFN-β and TNF-α),and those of the bone-healing relate cytokines such as TGF-β,BMP-7,VEGF,FGF-2 and OCN were detected by real-time PCR.X-ray films were taken at 1,2,3,5,7,9,and11 weeks postoperatively to continuously monitor fracture healing.The progress of fracture healing was evaluated by Modified radiographic union scale for tibia(m RUST).Three groups of experimental dogs were euthanized 15 weeks after the operation.The femur of the right hind limb was taken for three-point bending test,and bone tissue around the fracture line was taken for histological examination.The results showed that:(1)The group of IMN plus ESF had the shortest operative time(52.25±8.07 min),the smallest intraoperative blood loss(31.07±5.45 m L)and the smallest incision(3.97±0.49 cm).The group of DCP has the shortest time to start bearing weight(2.75±0.43 d).(2)The general trend of postoperative blood cell counts and biochemical indexes in the three groups was similar without characteristic changes.(3)Continuous X-ray imaging monitoring after orthopedics showed that the healing time of femur in the group of IMN plus ESF was the shortest(64.66±2.88 d),followed by the group of TIIMN(72.66±3.21 d).(4)Nail hole infection,fixation failure and delayed healing are potential complications for IMN plus ESF,TIIMN and DCP respectively.(5)Real-time PCR tests showed that the m RNA expression levels of inflammatory factors IL-6,IL-8,TNF-α and IFN-β,TGF-β,FGF-2,and bone healing related cytokines TGF-β,FGF-2 and OCN in the three experimental groups increased first and then decreased,and reached the peak at 4 weeks after orthopedics.The m RNA expression levels of bone healing related cytokines BMP-7 and VEGF in the three experimental groups reached the peak at week 2and then showed a downward trend.These trends are consistent with the physiological characteristics of fracture healing.(6)Biomechanical analysis of femur based on three-point bending test showed that the load in IMN plus ESF was significantly higher than that of DCP(P<0.05).(7)HE staining of femur sections showed that the bone histological structure of IMN plus ESF has nearly full recovered and the recovery process was earlier than the other two groups.In conclusion,IMN plus ESF was more beneficial to femoral fracture healing than DCP and TIIMN.This study provides valuable reference for the clinical treatment of canine femoral shaft fracture.