The Biomechanical Study Of Arthroscopic Acromioplasty Standard

Objective:Acromion impingement syndrome was first put forward byNeer CS in1972. It is a common disease that leads to the shoulder pain anddysfunction in the elderly population. According to the study of cadaverspecimens of the acromion morphology, Bigliani divided the acromions intothree types: flat acromion, curved acromion and the hooked acromion. At thesame time,he found the hooked acromion is more likely than the others tocause the impingement and rotator cuff injury. Accompanied by thedevelopment of the arthroscopic techniques, arthroscopic subacromialdecompression(ASD) has become the fist clinical treatment of acromionimpingement syndrome. Removal of excess subacromial bone is the key to theoperation, too little bone removal, can not effectively relieve the impingementsymptoms;and too much, easily to cause the acromion fracture. At present,thewidely accepted standard is grinding the curved or hooked acromion into flatone. By measuring the distance and pressure between the acromion androtator cuff in normal pepole and acromion impingement syndrome patientswith shoulder joint movement,this experiment wants to analyze if they havestatistical differences;By imitating the arthroscopic subacromialdecompression and observing the changes of the distance and pressurebetween the acromion and rotator cuff,this experiment wants to find the beststandard of the acromion grinding.Methods:7cadavers,provided by HeBei Medical University AnatomyDepartment (there are4hooked acromions in14of the shoulderjoints),planing tool cleared up the subacromial space arthroscopic and removalof the subacromial bursa and coracoacromial ligament. Measured respectivelythe distance between anterior acromion and rotator cuff of the hookedacromion group and normal group in neutral position. Using the pressure sensitive film to measure the maximal pressure between acromion and rotatorcuff of every shoulder joint by Neer test.Using the grinding drill grinded thesubacromial bone by5times arthroscopic(about1mm every time),after everytime of grinding,measured the distance and pressure between acromion androtator cuff. when the pressure reached the one in normal population,comparing the distance between acromion and rotator cuff with grinding flat,looking for the best standard of the acromion grinding.Result: During the Neer test examination, Whether normal acromion orhooked acromion, both have pressure between acromion and rotator cuff.Inhooked acromion group,the pressure was significantly greater than normalacromion group(P<0.01),but the distance between acromion and rotator cuffwas significantly less than normal acromion group(P<0.01);During thearthroscopic subacromial decompression, after the first and the secondgrinding, the pressure in hooked acromion group was still significantly greaterthan normal acromion group(P<0.01);after the third grinding,the pressure inthe two groups has no significantly statistical difference(P>0.05) and thedistance between acromion and rotator cuff was significantly less than the onewhich grinded flat (P=0.002<0.01);after the forth and fifth grinding, thepressure was less than normal acromion group and has the statisticalsignificance (P<0.01).Conclusion: In hooked acromion people, the subacromial space wasnarrower while the pressure between acromion and rotator cuff was greaterwhich explains why hooked acromion easily caused impingement and rotatorcuff injury. When grinding the subacromial bone, the pressure betweenacromion and rotator cuff has reached the numerical value that in normalpopulation before the hooked acromion become flat. So we can say that it isno necessary to grind the hooked acromion into flat while in the ASD, then itcan not only relieve the impingement symptoms but also largely reduce therisk of acromion fracture.