Risk factors for loss of reduction following locked plate fixation of proximal humerus fractures in older adults.

Purpose: To identify characteristics associated with loss of reduction following open reduction and locked plate fixation (ORIF) of proximal humerus fractures in older adults and determine if loss of reduction affects patient reported outcomes (PROs), range of motion (ROM), and complication rates during the first postoperative year.

Methods: Patients >55 years old who underwent proximal humerus ORIF were reviewed. Patient and fracture characteristics were recorded. Fixation characteristics were measured on the initial postoperative AP radiograph including humeral head height (HHH) relative to the greater tuberosity (GT), head shaft angle (HSA), screw-calcar distance, and screw tip-joint surface distance. Loss of reduction was defined as GT displacement >5 mm or HSA displacement >10° on final follow up radiographs. Patient, fracture, and fixation characteristics were tested for association with loss of reduction. Outcomes including ROM, visual analog scale pain and PROMIS scores, and complication/reoperation rates during the first postoperative year were compared between those with or without loss of reduction.

Results: A total of 79 patients were identified, 23 (29.1%) of which had a loss of reduction. Calcar comminution (relative risk [RR]=2.5, 95% Confidence Interval [CI]=1.3-5.0, p<0.01), HHH <5 mm above GT (RR=2.0, CI=1.0-3.9, p = 0.048), and screw-calcar distance ≥12 mm (RR=2.1, CI=1.1-4.1, p = 0.03) were risk factors for loss of reduction. Upon multivariate analysis, calcar comminution was determined to be an independent risk factor for loss of reduction (RR=2.4, CI=1.2-4.7, p = 0.01). Loss of reduction led to higher complication (44% vs 13%, p<0.01) and reoperation rates (30% vs 7%, p<0.01), and decreased achievement of satisfactory ROM (>90° active forward flexion, 57% vs 82%, p = 0.02) compared to maintained reduction, but similar PROs.

Conclusions: Calcar comminution, decreased HHH, and increased screw-calcar distance are risk factors for loss of reduction following ORIF of proximal humerus fractures. These morphologic and technical factors are important considerations for prolonged reduction maintenance.