Based On The Theory Of "Positive Buttress" To Discuss The Clinical Efficacy And Related Biomechanical Analysis Of Cannulated Nail Fixation In The Treatment Of Young And Middle-aged Femoral Neck Fracture

Objective:To evaluate the effect of three reduction results of "positive buttress","anatomical reduction" and "negative buttress" proposed by Gotfried on the clinical efficacy of cannulated nail fixation of femoral neck fracture in young and middle-aged patients through clinical retrospective analysis,and to explore the difference of efficacy of the three results in different Pauwels types of femoral neck fracture.The reduction model of femoral neck fracture with different Pauwels classification was reconstructed by CT data to investigate whether "positive buttress" has more mechanical advantages than "anatomical reduction" and "negative buttress" and whether the advantages are related to the Pauwels classification.Methods:1.Based on the theory of "positive buttress" to discuss the clinical efficacy of cannulated nail fixation in the treatment of young and middle-aged femoral neck fracture: Data of patients with femoral neck fracture treated in the First Affiliated Hospital of Guangzhou University of Chinese Medicine from January 2010 to December 2019 were retrospectively analyzed.Patients were identified according to inclusion and exclusion criteria and all patients according to the preoperative fracture pauwels Angle size are divided into pauwels Ⅰ group(group A),pauwels Ⅱ type(group B),pauwels Ⅲ type(group C).According to the postoperative reduction results,each group was further divided into anatomic reduction group(A1 group,B1 group,C1 group),positive buttress group(A2 group,B2 group,C2 group),and negative buttress group(A3 group,B3 group,C3 group),and a total of 9 subgroups were obtained.To compare the differences among patients with "anatomical reduction","positive buttress" and "negative buttress" under different Pauwels classification groups in terms of postoperative femoral neck shorteness,hip varus,bone nonunion,refracture,incidence of avascular necrosis of femoral head and postoperative Harris score of hip joint.To evaluate whether "positive buttress" has better clinical efficacy than "negative buttress" and "anatomical reduction" in the treatment of young and middle-aged femoral neck fracture among different Pauwels classification types,and whether its efficacy advantage is related to the Pauwels classification.2.A biomechanical study of "positive buttress" combined with cannulated nail in the treatment of femoral neck fracture in middle-aged and young adults:Through collecting a healthy patients with hip spiral CT scan data and taking the data into the relevant biomechanics of finite element analysis software,rebuild pauwels Ⅰ type,pauwels Ⅱ type,pauwels Ⅲ type model of the femoral neck fracture.The proximal end of the fracture was translated 2mm up and 2mm down along the fracture face,and the positive buttress,negative buttress and anatomical reduction model were obtained.Finally get 3 model of pauwels Ⅰ(positive buttress anatomical repositioning,negative buttress,each one),three model of pauwels Ⅱ(positive buttress anatomical repositioning,negative buttress,each one),three model of pauwels Ⅲ(positive buttress anatomical repositioning,negative buttress,each one),a total of nine models.By applying load and constraint to simulate the normal human standing model,the differences of global displacement,maximum stress of screw,maximum displacement at fracture site and average stress of medial bone cortex at fracture site were observed.assess whether "positive buttress" had a biomechanical advantage over the other two reduction outcomes and its correlation with Pauwels typing.results:1.Based on the theory of " positive buttress " to discuss the clinical efficacy of cannulated nail fixation in the treatment of young and middle-aged femoral neck fracture:A total of 170 patients were included,including 41 patients in group A(12 in group A1,14 in group A2,and 15 in group A3),82 patients in group B(36 in group B1,24 in group B2,and 22 in group B3),and47 patients in group C(24 in group C1,14 in group C2,and 9 in group C3).The average follow-up time of group A was 28.9±10.5 months,group B was 29.7±17.0 months,and group C was 25.1±12.5 months.There were no significant differences in age,gender,injured side,garden type,and follow-up time among subgroups A,B,and C.In group A,there were no significant differences in the occurrence of femoral head necrosis,shortening of femoral neck and Harris score at the last follow-up among the three reduction results(P > 0.05).In group B,the anatomical reduction(group B1)and the positive buttress group(group B2)had the same incidence of femoral head necrosis,and both were significantly lower than the negative buttress group(group B3)(P<0.05).The Harris score of the positive brace group(group B2)at the last follow-up was higher than that of the negative brace group(group B3),and there was no significant difference in the occurrence of femoral neck shortening among the three.In group C: the incidence of femoral head necrosis in the anatomical reduction group(C1 group)was lower than that of the positive buttress(C2group)and negative buttress group(C3 group)(P < 0.05).There was no significant difference between positive buttress(C2 group)and negative buttress(C3 group)in the occurrence of femoral head necrosis and femoral neck shortening(P>0.05).The incidence of femoral neck shortening in the anatomical reduction group(C1 group)was lower than that in the negative buttress group(C3 group)(P<0.05),and there was no significant difference in Harris scores between the three at the last follow-up(P>0.05).Harris score of the three groups at the last follow-up showed no significant difference(P > 0.05).2.A biomechanical study of "positive buttress" combined with cannulated nail in the treatment of femoral neck fracture in young and middle-aged adults:In the pauwels type I fracture model,the overall displacement of the positively buttressed model is 0.39 mm,the maximum stress of the hollow screw is 33.26 MPa,the maximum displacement of the fracture is 0.24 mm,and the average stress of the medial cortical bone at the fracture is 6.26 MPa,which are lower than the anatomical reduction and the negative Buttress,negative buttress is the worst performer.In the pauwels type II fracture model,the maximum stress of the positive buttress and the anatomical buttress screw and the average stress of the medial cortical bone at the fracture are equal,41.17 MP,42.76 MP,6.69 MP,6.64 MP,respectively,which are lower than the negative buttress。In pauwels type III,there is no obvious advantage in positive buttress.conclusion:1.In terms of clinical efficacy,the clinical efficacy of anatomical reduction,positive buttress and negative buttress in pauwels type I are equivalent.In pauwels type II,positive buttress has the same effect as anatomical reduction,which can reduce the incidence of postoperative femoral head necrosis and improve postoperative hip joint function,while the effect of negative buttress is poor.In pauwels type III,there is no obvious advantage in positive buttress.2.In pauwels I,the mechanical stability of the positive buttress is significantly better than the anatomical reduction and the negative buttress,and the negative buttress has the worst stability after fixation.In pauwelsⅡ,the mechanical stability of the positive buttress and anatomical reduction is equivalent,but both are better than the negative buttress.In pauwels Ⅲ,the anatomical reduction is better than the positive buttress and the negative buttress,and the positive buttress is equivalent to the negative buttress.It can be inferred that the biomechanical advantage of positive buttress is related to the pauwels classification,which is gradually lost as the pauwels angle increases.3.Part of the clinical research results of this study are inconsistent with the results of finite element analysis,which may be due to the small number of included cases and greater bias.However,based on the results of this study,we believe that the clinical efficacy and mechanical advantage of positive buttresss are related to the size of the pauwels angle.In pauwelsⅠ and pauwels Ⅱ,the effect of positive buttress is equivalent to that of anatomical reduction and fixation,and negative buttress should be avoided under any circumstances.The results of the study have guiding significance for the micro dialectical treatment of Chinese medicine.