Analysis Of Risk Factors For Loss Of Reduction After Acute Acromioclavicular Joint Dislocation Treated With The Suture-button And Biomechanical Verification Of Related Risk Factors

PurposeThe objective of this retrospective study is to analyze the risk factors causing loss of reduction after acute acromioclavicular(AC)joint dislocation treated with the Suture-button deviceand further use biomechanical methods to analyze and verify the relevant risk factors.A method for simply determining the position of clavicle tunnel and the button plate under the coracoid through imaging measurementis proposed and proven by biomechanical experiment.MethodsOne hundred and thirty-eight patients with AC joint dislocation who were surgically treated the Suture-button in our hospital from February 2009 to February 2015,were recorded their age,sex,BMI,Rockwood's classification,with or without osteoporosis,Double or Triple Suture-button,coracoid button position,alignment of the button,position of the clavicle tunnel and diameter of the coracoid tunnel,and so on.Mean comparisons or chi-square test was used for univariate analysis of the above factors,and then multivariate logistic regression analysis was performed to predict risk factors.The relevant risk factors obtained were verified by biomechanical experiments on acromioclavicular joint specimens of fresh cadavers.Different tunnels were constructed on the coracoid based on different entry and exit points in the coracoid process:center-center,center-medial(to tilt 10°,20°,and 30° medially)and center-lateral(to tilt 10°,20°,and 30° laterally).The different tunnel specimens were loaded on the biomechanical machine until they were destroyed.The degree of displacements and rotations were measured,and the failure load and failure mode were evaluated.In the same manner as above,the failure load and failure mode of the non-osteoporotic group and the osteoporosis grouptunnels,and the failure load and failure mode of specimens using the relative proportional method,the specific digital method and imaging measurementto determine the position of the clavicular tunnel were evaluated.ResultsReduction was lost in 23.1%of the patients.Univariate analysis showed that button alignment,double or triple Suture-button,coracoid button position,position of the clavicle tunnel,osteoporosis and osteolysis had statistically significant association with loss of reduction for AC joint(P=0.031,0.034,0.000,0.023,0.000 and 0.000 respectively).Multivariate logistic regression analysis demonstrated that osteoporosis(P=0.013),position of the clavicle tunnel(P=0.034),coracoid button position(P=0.018),and osteolysis(P=0.008)were the risk factors that significantly associated with the loss of reduction after AC joint dislocation treated with the Suture-button.The biomechanical study further confirmed that the center-center tunnel had the highest failure load(536.5±142.0N).There was no significant difference in the peak values of failure load between the center-medial 10° type and center-lateral 10° type tunnel(P>0.05),but there was a significant difference between the three tunnels and the other four tunnels(P<0.05).When the direction of the tunnel was deflected inward or outward by more than 20° and above,the peak value of the maximum failure load would be significantly reduced.Moreover,the peak value of failure load in the non-osteoporotic tunnels was significantly higher than that of the osteoporotic tunnels(P<0.05).Compared with the relative proportional methodand imaging measurement,the specific digital method to determine the position of the clavicular tunnel resulted in a significant decrease in the peak value of the failure load(P<0.05).ConclusionsAccuracy of clavicular tunnel location,accurate placement of button plate under coracoid process(inside or outside deviation<20°),more stable fixation for patients with osteoporosis,and correct surgical procedure are important factors in preventing loss of reduction.The imaging measurement method can better locate the position of the clavicular tunnel and determine whether the position of the plate under the coracoid process is correct.The method is simple and practical,and is consistent with the biomechanical results.