Magnetic Resonance Imaging Assessment of Acromion Morphology and Superior Displacement of the Humeral Head in the Impingement Syndrome

충돌 증후군에서 견봉 형태 및 상완골 두 상방 전위의 자기공명영상 분석

Purpose: We studied magnetic resonance imaging of acromion morphology and superior displacement of the humeral head in the patients with diagnosis of rotator cuff impingement syndrome, and also documented the relationship of type Ⅲ acromion to the rotator cuff tear. Materials and Methods: We reviewed retrospectively 40 patients(40 shoulders) who had arthroscopic treatment for the diagnosis of stage II impingement or rotator cuff partial tear and did not have other risk lesions except acromion factor. The mean age was 48.7 years at operation. 21 men(2l shoulders), mean age of 26 years, were used as controls. Acromial type, tilt, and superior displacement of humeral head in sagittal plane, and acromial lateral angulation in coronal plane were measured. Four parameters of the patients were compared with those of control group. And then, the data were subdivided and analyzed with respect to acromial type and patient age in the impingement group. Student t test and multi-way ANOVA were used. Results: In impingement group, Farley's type I acromion, 33%, type Ⅱ, 38%, type Ⅲ, 27% and type Ⅳ, 2%. Superior displacement of humeral head( 4.8mm) were characteristic in the impingement group compared with the control group(1.3mm)(p<0.05). But acromial tilt and lateral angulation were not statistically different. In the analysis of the impingement group, the change of 4 parameters was not significant with respect to age(p>0.05), but lateral angulation in type I acromion(18 degree) and superior displacement of humeral head in type Ⅲ acromion(6.3mm) were significantly increased(p<0.05). All 4 parameters were not different between two subdivided types of type Ⅲ acromion. Conclusion: All types of acromian and large lateral angulatian cauld develop impingement syndrame, but acromial tilt was nat risk factar. Appearance of type Ⅲ acromian and increased superiar displacement of humeral head were characteristic findings in the impingement syndrame. Superiar displacement of humeral head as a result of degenerative change of rotatar cuff was probably primary cause far impingement. The type Ⅲ acromian might be an acquired farm, which cauld be expected to accelerate the tear of rotatar cuff as a cansequence.