The relationship between acromion thickness and body habitus. Practical implications in subacromial decompression procedures

Introduction The bone amount that should be removed during an acromioplasty has always been a challenge for the surgeon. Our aim was to verify the reliability of the existing data, to assess the differences between the two genders, to verify the existing to verify the exsisting correlation between scapular dimensions and acromial thickness and to investigate the relationship between acromial type and thickness Materials and methods We examined 500dried scapulae, measuring three distances for each one referring to the scapular body and acromial thickness; they were also catalogued according to gender. Acromial shape was classified according to Bigliani ‘s methtod. Chi square lest was used to evaluate the association between variables; t test and ANOVA to evaluate the differences between groups. Pearson's correlation was also calculated. Results The frequencies were: Type I 38.9 %, Type II 39.4 % and Type III 21,7 %, the mean of the acromial thickness was 0.85 cm; differences due to gender were stated. The correlation indexes showed a direct linear relationship between scapular dimensions and acromial thickness. While analyzing the acromial thickness, we found a statistical significant difference between hooked and flat acromion as well as between hooked and curved acromion. Discussion The average value and the range of the acromial thickness proved to be wider than previously reported in literature. Because of the thicker acromion, male patients can have a more extended subacromial decompression, with a lower risk of fracture. The same reasoning applies to Type III acromia, which are averagely thicker (O.1 cm) and they also own a wider range of thickness with respect to the others Types. Acromial thickness proved to be correlated to the body habitus of the patient, Conclusions While planning an acromioplasty, we should be aware that gender, specific scapular dimensions and acromial shape should be evaluated preoperatively since they influence the acromial thickness, in order to decide the amount of bone removal.