Novel Technical Factors Affecting Proximal Humerus Fixation Stability.

OBJECTIVES:Intra-articular screw cut-out is a common complication after proximal humerus fracture (PHF) fixation using a locking plate. This study investigates novel technical factors associated with mechanical failures and complications in PHF fixation. DESIGN:A retrospective radiological study. SETTING:Level 1 trauma center. PATIENTS/PARTICIPANTS:Clinical and radiological data from consecutive PHF patients treated between January 2007 and December 2013 were reviewed. INTERVENTION:Open reduction and internal fixation with the Synthes Philos locking plate. MAIN OUTCOME MEASUREMENTS:Postoperative radiographs were assessed for quality of initial reduction, humeral head offset, screw length, number and position, restoration of medial calcar support or the presence of calcar screws, and intra-articular screw perforations. Using SliceOMatic software, we validated a method to accurately identify screws of 45 mm or longer on AP radiographs. Follow-up radiographs were reviewed for complications. RESULTS:Among 110 patients included [mean age 60 years, 78 women (71%), follow-up 2.5 years] and the following factors were associated with a worse outcome. (1) Screws >45 mm in proximal rows [Odds Ratio (OR) = 5.3 for screw cut-out); (2) lateral translation of the humeral diaphysis over 6 mm (OR = 2.7 for loss of reduction); (3) lack in medial support by bone contact (OR = 4.9 for screw cut-out); (4) varus reduction increased the risk of complications (OR = 4.3). CONCLUSION:The importance of reduction and calcar support in PHF fixation is critical. This study highlights some technical factors to which the surgeon must pay attention: avoid varus reduction, maximize medial support, avoid screws longer than 45 mm in the proximal rows, and restore the humeral offset within 6 mm or less. LEVEL OF EVIDENCE:Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence. LEVEL OF EVIDENCE:Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.