| Background: Two factors have been proposed as contributors to the development of shoulder impingement syndrome.“Intrinsic mechanisms” means that SIS is ca used by the degeneration of supraspinatus tendons which caused by long-term over use and excessive tension loading.“Entrinsic mechanisms” suggests that SIS is re lated to the direct mechanical compression due to tissue structure changes out of the supraspinatus tendon itself.Objective:To explore the pathogenic mechanism of subacromial impingement synd rome by Evaluatiung acromiohumeral distance(AHD),supraspinatus tendond thickne ss and shoulder-neck posture(forward head posture and forward shoulder posture)in patients with/without subacromial impingement syndrome.Method: 20 patients with subacromial impingement syndrome assigned to observa tion group.20 healthy person matched observation group in age,gender and weight assigned to control group(both groups are right handness).Ultrasound images w ere collected using a 5–12-MHz linear transducer in B-mode.Participant seated fee t flat on the floor,neutral trunk posture,head straight,and arm resting at the side.The ultrasound transducer was placed on the midpoint of acromion with the long axis of the transducer placed in the plane of the scapula and parallel to the flat surface of the acromion.The acromiohumeral distance(AHD)defined by the inferio r acromion and superior humeral head.Participants seated,feet flat on the floor,neutral trunk posture,and head facing forward.Participants were then asked to pla ce their hand on the ipsilateral posterior hip with the humerus in extension elbo w in flexion.The supraspinatus tendon was measured at anterior aspect of acromio n in the transverse(short axis).Using image callipers,measurements of tendon thi ckness were taken at 3 points along the tendon and averaged for a single thicknes s measure.The occupation ratio was calculated as the tendon thickness as a perc entage of AHD.Evaluated shoulder-neck posture with Global Posture System(GPS)by measuring craniovertebral angle(CA)and forward shoulder angle(FSA).The C A was identified at the intersection of a horizontal line passing through the C7 sp inous process and a line joining the tragus of the ear to the skin overlying the C7 spinous process.The FSA was identified at the intersection of a horizontal line passing through the C7 spinous process and a line joining the midpoint of the a cromion to the skin overlying the C7 spinous process.Statistic difference was assi gned at P<0.05Result:The observation group(supraspinatus tendon thickness:6.6±0.5mm,occupatio n: 61.2%±8.3%)had a significantly thicker tendon(p<0.01)and a greater tendon occupation ratio(p<0.01)compared to matched controls(supraspinatus tendon thickness:5.8±0.6mm;occupation: 49.3%±7.2%).There were no AHD(observation group :10.9±1.2mm;control group :11.4±0.9mm)group differences(p>0.05).The observation group had a significantly smaller forward shoulder angle(observation group :46.8°±15.4°;control group :58.4°±8.6°,p<0.01).There were no cranioverte bral angle(observation group :49.1°±7.2°,control group :51.2°±4.5°,p>0.05)grou p differences.There is a moderate correlation between AHD and FSA in observation group(P<0.001,R=0.62),but no correlation between AHD and CA in observation gr oup(P>0.05,R=0.18).No correlation between AHD and CA(P>0.05,R=0.20),A HD and FSA(P>0.05 R=0.12)in control group(P>0.05).Conclusion:Both “intrinsic mechanism”and “extrinsic mechanism” were involved i n the pathogenesis of the SIS.Among them,the “intrinsic mechanism” takes the leading position. |
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