Abstract
Purpose
Locking plate constructs for proximal humerus fractures can fail due to varus collapse, especially in the presence of osteoporosis and comminution of the medial cortex. Augmentation using a fibular allograft as an intramedullary bone peg may strengthen fixation preventing varus collapse. This study compared the ability of the augmented locking plate construct to withstand repetitive varus stresses relative to the non-augmented construct in cadaveric specimens.
Method
Proximal humerus fractures with medial comminution were simulated by performing wedge-shaped osteotomies at the surgical neck in cadaveric specimens. For each cadaver (n=8), one humeral fracture was fixated with the locking plate construct alone and the other with the locking plate construct plus ipsilateral fibular autograft augmentation. The humeral head was immobilized and a repetitive, medially-directed load was applied to the humeral shaft until failure (significant construct loosening or humeral head screw pull-out).
Results
No augmented construct failed, withstanding either 20 000 cycles or five times the cycles of the contralateral non-augmented construct [average (standard deviation) = 27958 (4633) cycles], while six of the eight non-augmented constructs failed (p=0.007). Failure in the six non-augmented constructs occurred after an average of 5928 (2543) cycles.
Conclusion
Fibular allograft augmentation increased the ability of the locking plate construct to withstand repetitive varus loading. Clinically, this may assist proximal humerus fracture fixation in osteoporotic bone with medial cortex comminution.
