Novel Technical Factors Affecting Proximal Humerus Fixation Stability

OBJECTIVES:Intra-articular screw cut-out is a common complication following proximal humerus fracture (PHF) fixation using locking plate. This study investigates novel technical factors associated with mechanical failures and complications in PHF fixation. DESIGN:Retrospective radiological study. SETTING:Level 1 trauma centerPatients/ParticipantsClinical and radiological data from consecutive PHF patients treated between January 2007 and December 2013 were reviewed INTERVENTION:ORIF 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 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 females (71%), follow up 2.5 years) and the following factors were associated with worse outcome. Screws >45mm in proximal rows (Odds Ratio (OR) =5.3 for screw cut-out); Lateral translation of the humeral diaphysis over 6mm (OR=2.7 for loss of reduction); Lack in medial support by bone contact (OR=4.9 for screw cut-out); Varus reduction increased 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 attentionavoid varus reduction, maximize medial support, avoid screws longer than 45mm in the proximal rows and restore the humeral offset within 6mm or less. LEVEL OF EVIDENCE:Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence