Study Between Acromion Morphology And Lateral Extension Of Acromion In Three-dimensional Computed Tomography

ObjectiveMorphological variations of the acromion and lateral extension of the acromion(LEA)may be the causes of rotator cuff tears(RCT).The purpose of this study was to evaluate the relationship between acromion morphology and the variation of the LEA by three-dimensional computed tomography(3D-CT)reconstruction,and to determine whether there are differences in LEA parameters based on gender,profile,and age.To provide anatomical basis for the pathogenesis of the RCT and the clinical acromioplasty.MethodsA total of 120 patients with a bilateral shoulder in the radiology department of our affiliated hospital from January 2021 to May 2021 were collected.Mimics 21.0 software was used to construct the 3D model of the scapula.Subjects were divided into 6 groups based on age(group 1:20-30 years,group 2:31-40 years,group 3:41-50 years,group 4:51-60 years,group 5:61-70 years,and group 6:71-80 years).The anatomical morphology of acromion was observed to analyze the differences of acromion morphology between different sexes and ages.The morphological parameters of LEA were measured and its anatomical morphology was determined.The differences of the LEA parameters between different age group were compared.At the same time,the LEA parameters between different sexes and sides were analyzed.Then compare the LEA parameters in different acromial morphology to determine the correlation between them.ResultsThere were three anatomical morphology of acromion,type Ⅰ was "flat shape",type Ⅱ was "curved shape",and type Ⅲ was“hooked shape".The proportion of the acromion in male and female subjects was 62(51.7%)and 58(48.3%),respectively.The mean ages of acromial subjects of type Ⅰ,type Ⅱ,and type Ⅲ were 48.81 years,49.64 years,and 55.96 years,respectively.There were two different types of LEA in the population,large acromial lateralization(31.43 ±0.18 mm)and short acromial lateralization(27.48±0.24 mm).There were no statistically significant differences in LEA among different ages and genders(P>0.05).The mean LEA of males was 30.03±0.30 mm and that of females was 29.21±0.35 mm.There was no difference in LEA length between the sexes(P=0.075).The average LEA measured on the right side(30.46±0.25 mm)was significantly higher than that on the left side(28.81±0.21 mm)(P<0.05).The LEA parameters were positively correlated on both sides of subjects of different genders(male:R2=0.850;Female:R2=0.779).The LEA value for type Ⅲ(32.81±0.22 mm)was significantly higher than that for type Ⅰ(26.38±0.28 mm)and type Ⅱ(29.74±0.15 mm)(P<0.05).It was a significant positive correlation between the left and the right side of the LEA in different acromial morphology(R2=0.904,P<0.001).ConclusionsIn this study,based on 3D-CT reconstruction,three different anatomical types("flat shape","curved shape",and "hooked shape")were found in the acromion,and two types of LEA were found in anatomical morphology,namely,large acromial lateralization and short acromial lateralization.There was no difference between sex and age in the parameters of the LEA,and the LEA parameters on the right side were significantly higher than those on the left side.The LEA measurement of type Ⅲ was the largest,type Ⅱ was the second,and type Ⅰ was the smallest.