RESUMO
BACKGROUND: Complications following locking plate fixation in proximal humeral fractures often related to malposition plates and inadequate screw fixation. However, literature did not define the best anatomical reference point for plate positioning. We conducted a study to assess the occurrence of subacromial impingement and screw perforation with two anatomical reference points for proximal humeral plate positioning. METHOD: Sixty shoulders of 30 cadavers were dissected, and proximal humeral locking plate was placed in two different levels in the coronal plane of the upper tip of plate: (1) the proximal portion of bicipital groove group and (2) the most prominent of lesser tuberosity group. Subacromial impingement during passive forward elevation and screw perforation were assessed in relation to the plate positioning. RESULTS: No subacromial impingement during passive motion contacted to the plate in both groups. The calcar screw perforation rate was significantly lower in the proximal portion of the bicipital groove group (2 of 60 specimens, 3.33%) than the most prominent of lesser tuberosity group (52 of 60 specimens, 86.67%). The most proximal screws of the plate were no humeral head perforation in all specimens. CONCLUSION: Our study would suggest that two anatomical reference points could be used to be the landmark to avoid the subacromial impingement and the most proximal screw perforation. However, the placement of the locking plate using the proximal portion of bicipital groove reference is better for calcar screw insertion.