Fig 1.
AB The acromion was divided into two equal parts illustrated on the upper surface. CD Spur located in the lateral region of the subacromial surface. EF Spurs located in the medial region of the subacromial surface. GH Spurs were located in the A+B region.
Fig 2.
A 3D image obtained from Mimics. B The image was first divided using the rectangular patch tool in 3-matic software. C The clavicle was hidden, and the scapula was separated. D The body of the scapula was hidden, and the acromion was rotated. E The lasso area marking tool was used to demonstrate the subacromial region. F The smooth marking border function was then utilized to smooth the border of the segmented subacromial region. G Curvature analysis was conducted to assess the relative flatness of the inferior surface of the acromion (mesh type: Noisy, fitting radius: 8). H The lasso area marking tool and smooth marking border function were used again to obtain the spur border. I The area of the spur was obtained and calculated. J The last image obtained after a series of procedures in Mimics software.
Fig 3.
An L-shaped acromial angle: The lateral border of the acromion showed a bony protuberance, similar in shape to the letter L.
B C-shaped acromial angle: The lateral border of the acromion had a curved arc shape. C Double angle-shaped acromial angle: The lateral border of the acromion showed two bony protuberances.
Fig 4.
A Type I (flat) acromion. B Type II (curved) acromion. C Type III (hooked) acromion.
Fig 5.
The acromial type in different sex and age groups.
There were no significant differences in the acromial classification among the three different age groups.
Fig 6.
The number of acromial spurs in different sex and age groups.
Males in group I were more prone to have subacromial spurs than females in the left and right shoulders (P = 0.003, P = 0.014), and a significant increase in the occurrence of spurs was also found in males compared with females in the right shoulder (P = 0.014).
Table 1.
The distribution character of all subacromial spur.
Table 2.
The area of subacromial surface and total spur area.
Fig 7.
The acromial angle type in different sex and age groups.
There were no significant differences in the acromial angle in males compared with females among the three different age groups. More L- or double angle-shaped acromial angles were found in the left shoulder in females than in males in group III (≥61 years).
Table 3.
The association between the acromion classification and acromial angle.
Table 4.
The association between the acromion classification and subacromial spurs.