Postoperative dorsal step-off predicts olecranon osteotomy union: a retrospective cohort study.

Purpose: Olecranon osteotomy has been associated with loss of reduction, nonunion, implant failure, and migration of wires. We aim to evaluate quality of reduction of the osteotomy site as a predictor of olecranon osteotomy nonunion.

Methods: One hundred and twenty-five distal humerus fractures that underwent open reduction internal fixation (ORIF) were reviewed. Amount of dorsal step-off was measured from the lateral radiograph from the second postoperative visit. A receiver operating curve (ROC) analysis was used to assess the predictability of nonunion based on dorsal displacement of the olecranon osteotomy.

Results: Between 2014 and 2022, 36 patients underwent a chevron olecranon osteotomy (29%). Of the 36 patients, 7 (19%) failed to successfully unite at the osteotomy site. Two experienced aseptic nonunion, 2 were malreduced leading to nonunion, 2 malunited, and 1 had persistent fracture lines following poor osteotomy cut. Patients that developed nonunion had a mean dorsal displacement of 3.87 mm versus 1.15 mm (p < 0.001). The ROC demonstrated excellent prediction for nonunion based on displacement (AUC = 0.896, p = 0.002). Youden's index was determined at a sensitivity of 86% and a specificity of 73% corresponding to a dorsal step-off of 2.07 mm. This finding was confirmed on multivariate logistic regression showing a step-off over 2.07 mm is an independent predictor of olecranon osteotomy nonunion (p = 0.021).

Conclusion: A malreduction resulting in a dorsal step-off larger than 2.07 mm is predictive of olecranon osteotomy nonunion or malreduction. Therefore, the success of the olecranon osteotomy approach is directly dependent on quality of anatomic reduction.

Level of evidence: III; Retrospective Cohort Study.