Failure of humeral shaft fixation: construct characteristics.

Purpose: Fixation failure following open reduction and internal fixation (ORIF) of humeral shaft fractures can be a challenging complication. We aimed to identify the modes of failure and characteristics of failed fixation constructs.

Methods: We queried our institutional database for patients > 18 years old with fixation failure after ORIF with single plate and screw constructs of humeral shaft fractures from 2006 to 2017. Demographics, fracture characteristics, fixation construct design and mode of failure were recorded.

Results: Twenty-three failures were identified. Mean age was 55.9 years (SD 19.2 years) with 15 (65%) women. Twelve patients (52%) had midshaft fractures; the remainder had distal-third shaft (8 pts, 35%) or proximal-third shaft (3 pts, 13%) fractures. Midshaft fractures were most commonly fixed through an anterolateral approach with plates and all non-locking screws (83%), while distal-third shaft fractures were fixed with a combination of locking and non-locking screws from a posterior approach. Distal-third shaft fractures failed by plate breakage (63%) or screw pullout (38%) and all midshaft failures occurred by screw pullout proximal (92%) or distal (8%) to the fracture. Resultant varus deformity occurred in 20 (87%) fractures.

Conclusion: Screw pullout in midshaft fractures suggests that fixation to bone was insufficient or biomechanically disadvantageous. Varus moments contribute significantly to the failure of humeral shaft fracture ORIF. Plate breakage in distal fractures suggests high concentrations of stress over a narrow working length of constructs with inadequate plate strength. Recognizing how these constructs fail can aid proper implant selection and application for humeral shaft fracture.

Level Of Evidence: Treatment level IV.