| Objective The aim of this study was to explore micromovement and stress in fracture site through finite element,providing theory for delayed union and nonunion of extremity long bone fractures by the dynamization with LCP.And investigate the clinical efficacy of dynamization/dynamization combined with bone grafting for delayed union/nonunion,which provide an alternative treatment options for delayed union and nonunion of extremity long bone fractures with LCP.Methods Part One: Finite element modeling software was used to build three internal fixation models for treating tibia transverse fracture,the fracture was fixed with common screws in compression holes in proximal and locking screws fixation at distal(A Group),common screws in locking holes in proximal and locking screws fixation at distal(B Group),all locking screws(C Group).Compressive stress tests were applied in each group with 1/6,2/6,3/6,4/6,5/6 and 1 times of the weight values(100N,200 N,300N,400 N,500N,600N).(1)The maximal stress of the tibia and internal fixation,the stress of fracture site were measured when the fracture was contacted.(2)The axial micromovement was measured when the fracture gap was 2mm,5mm and 10 mm respectively.Part Two: From May 2008 to May 2016,41 delayed union patients were treated at our department,they were divided into dynamization and conservative groups.14 patients were received operation with dynamization of LCP,9 males and 5 females,6 cases of femur,8 cases of tibia.27 patients were received conservative treatment with fixed,taking promoting bone formation drugs,regular observation,16 males and 11 females,13 cases of femur,14 cases of tibia.The two groups were compared in terms of union time and the rates of union.Part Three: From May 2008 to May 2016,53 nonunion patients were treated at our department.17 patients were received operation with dynamization of LCP combined with bone grafting(dynamization combined with bone grafting group).7 cases of femur,10 cases of tibia.12 of them were atrophic nonunion,5 malnutrition nonunion.36 patients were received operation with simple bone grafting(bone grafting group).17 cases of femur,19 cases of tibia.21 of them were atrophic nonunion,15 malnutrition nonunion.The two groups were compared in terms of operation time,intraoperative bleeding,X-ray grayscale values in bone grafting area at one month,three month,six month and the moment when the fracture got healed after surgery,union time,the score of joint functional.Results Part One: Under the same axial stress load,(1)The max stress of tibia when the fracture site was contacted: A>B>C,the max stress of internal fixation: A<B<C,the stress in fracture site: A>B>C,it was significantly different among those groups(P<0.05).(2)the micromovement in fracture site when the fracture gap was 2mm,5mm and 10mm: A>B>C,it was significantly different among those groups(P<0.05).C groups could not reach effective values,but the two kinds(A,B)of internal fixation could generate effective micromovement.Part Two: The dynamization group and conservative group obtained(14.76 ± 4.34)months and(13.83 ± 4.00)months respectively.The healing time and the rates of union were [(4.67± 0.78)months,(6.14 ± 1.23)months] and [85.71%(12/14),51.85%(14/27)],all of them had statistical difference(P<0.05).Part Three: The dynamization combined with bone grafting group and bone grafting group obtained [(17.50±4.00)] months and [(18.06±3.46)] months respectively.The length of incision,the operation time and the intraoperative bleeding had no statistical difference(P>0.05).The X-ray grayscale values in bone grafting area: there was no significantly difference at one month and the moment when the fracture got healed(P>0.05),but significantly difference at three month and six month(P<0.05).The healing time and joint function score of two groups were [(6.57±0.85)months,(8.48±1.34)months],[(84.65±7.32),(75.87±9.01)],[(89.42±11.34),(74.79±10.56)],all of them had statistical difference(P<0.05).3 cases donor site pain in dynamization combined with bone grafting group,7 cases in bone grafting group,all relieved in two month.3 and 9 cases graft failure in two groups.3 and 7 cases fat liquefaction occurred and got healed with dressing.Conclusion The A and B two kinds of internal fixation could generate effective micromovement,reduce stress in the fixed device and increase stress in fracture site,but the C groups could not reach effective values.In case of delayed nonunion of extremity long bone fractures treated by LCP,simple conservative treatment effect was poor,the dynamization of LCP could significantly shorten the time of union and reduce the risk of nonunion.Compared with simple bone grafting,dynamization of LCP combined with bone grafting could shorten the healing time of fracture nonunion,and it was simple,safe and effective,worth to be applied. |
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