ABSTRACT
Objective To provide anatomic evidence for chock-block technique used for acromioplasty.Methods Thirty cadaveric specimens of intact shoulder fixed by formaldehyde solution were used for this anatomic study.They were chosen from 15 males and 15 females and from 17 left and 13 right sides.First the specimens were dissected for observation of general morphology of the acromion.According to the Bigliani's classification,the acromions were sorted in morphology as type Ⅰ (flat),type Ⅱ (curved) and type Ⅲ (hooked).The shortest distance from the acromion to the humeral head (A-H) was measured.Then the location of subacromial impingement was observed and the thickness of the anterolateral angle was measured preoperatively.At last,acromioplasty using the chock-block technique was performed in the acromions of types Ⅱ and Ⅲ.Postoperatively,the distance A-H and the thickness of the anterolateral angle were measured again for comparison with the preoperative values.Results According to the Bigliani's classification,7 acromions were type Ⅰ,13 type Ⅱ and 10 type Ⅲ.Subacromial impact occurred only in the anterior acromions of types Ⅱ and Ⅲ.The distance A-H was 0.670 ± 0.035 cm in type Ⅰ acromions,significantly longer than the preoperative values of type Ⅱ (0.506 ±0.029 cm) and type Ⅲ (0.334 ±0.023 cm) (P ＜ 0.05),but showed no significant differences from the postoperative values of type Ⅱ (0.692 ±0.025 cm) and type Ⅲ (0.699 ±0.024 cm) (P ＞ 0.05).The anterolateral angular thickness of type Ⅰ acromions was O.413 ± 0.015 cm,significantly thinner than the preoperative values of type Ⅱ (0.607 ±0.014 cm) and type Ⅲ (0.623 ±0.025 cm) (P ＜ 0.05),but showed no significant differences from the postoperative values of type Ⅱ (0.414±0.035 cm) and type Ⅲ (0.412±0.033 cm) (P＞ 0.05).Conclusion The chock-block technique used for acromioplasty is effective because it can enlarge the supraspinatus outlet and deter impingement.