The safe zone for avoiding suprascapular nerve injury: an anatomical study on 500 dry scapulae

Purpose Suprascapular nerve injury may be a complication during shoulder arthroscopy. Our aim was to verify the reliability of the existing data, assess the differences between scapulae in the two genders and in the same subject, obtain a safe zone useful to avoid iatrogenic nerve lesions, and analyze the existing correlations between the scapular dimensions and the safe zone. Material and Methods We examined five hundred dried scapulae, measuring six distances for each one, referring to the scapular body, glenoid and the course of the suprascapular nerve, also catalogued according to gender and side. Differences due to gender were assessed comparing mean ± sd of each distance in males and females ; paired t-test was used to compare distances deriving from each couple. Successively we calculated our safe zone and Pearson's correlation. Results We found non-significant differences between the right and left distances deriving from each couple ; differences due to gender were stated. We defined three kinds of safe zones referring to : 500 scapulae ; males (139 scapulae) and females (147 scapulae). The correlation indexes calculated between the axis of the scapular body and glenoid and the posterosuperior distance (referring to the suprascapular nerve) were0.624,0.694,0.675, 0.638 ; while those with the posterior distance were0.230,0.294,0.232,0.284. Discussion Knowledge of the safe zone, for avoiding suprascapular nerve injury, is important ; gender and specific scapular dimensions should be evaluated since they influence the dimensions of the safe zone. The linear predictors should be used to obtain specific values of the posterosuperior limit in each patient.