Study On The Mechanism Of Different Kinematic Patterns Of Shoulder Joint Caused By Rotator Cuff Tears

Objectives:1.To evaluate the rotator cuff function(RCF)and glenohumeral joint function(GHF)and define new types of shoulder kinematic patterns based on the radiographic characteristics.2.To explore the effect of rotator cuff above the rotation center of humeral head on maintaining the stability of humeral head during shoulder abduction,and to propose a new concept of superior rotator cuff.3.To analyze the difference of soft tissue and bony structure in patients with different kinematic patterns.Methods:1.118 patients with RCT were included.The proximal humeral migration(PHM)and glenohumeral abduction angle in scaption were measured.According to the RCF and glenohumeral joint,all patients were classified into different kinematic patterns of the shoulder joint.2.To analyze the effect of residual rotator cuff above the rotation center of the humeral head on RCF and to discuss the effect of the rotator cable on the stability of the humeral head.3.To evaluate the soft tissue and bony factors influencing the function of the glenohumeral joint in patients with dysfunctional rotator cuff.Result:1.According to the activity of glenohumeral joint and PHM,the kinematic patterns of the patients with RCT are divided into three types:type I: primary supporting point;type II: functional secondary supporting point;Type III: dysfunctional secondary supporting point.2.The PHM in patients without residual rotator cuff tissue above the rotator center of humeral head was significantly higher than that of patients with residual rotator cuff tissue above the rotator center of humeral head(2.87 ± 1.21 mm vs 0.86 ± 1.44 mm,P < 0.001).The ratio of patients without residual rotator cuff tissue above the rotator center of humerus with secondary supporting point(85%)was significantly higher than that of patients with residual rotator cuff tissue(4%,P < 0.001).When there was residual rotator cuff above the rotation center of humeral head,no significant difference was observed on PHM no matter the rotator cable was intact or disrupted(0.75 ± 1.48 vs 1.29 ± 1.31,P = 0.294).3.In patients with dysfunctional rotator cuff(secondary supporting point),soft tissue had no significant effect on the function of glenohumeral joint(P > 0.05).The anterior coverage(20.88 ± 17.99 vs-1.19 ± 13.03,P =0.012)and the acromial slope(33.44 ± 6.42 vs 25.91 ± 5.74,P = 0.027)of the patients with functional secondary supporting point were significantly higher than those with dysfunctional secondary supporting point.Conclusion:1.The kinematic patterns of the shoulder in patients with RCT can be divided into three types: primary supporting point,functional secondary supporting point and dysfunctional secondary supporting point.2.Supraspinatus,infraspinatus and superior parts of the subscapularis tendon and the teres minor above the rotation center of the humeral head can depress the humeral head.There is a closing relationship between the PHM and residual rotator cuff above the rotation center of humeral head,while no significant correlation was observed between rotator cable and PHM.3.Soft tissue factors have no significant effect on GHF in patients with dysfunctional rotator cuff.Acromial anterior coverage and acromial slope are the critical bony factors influencing the function of glenohumeral joint in patients with dysfunctional rotator cuff.