Proximal humeral fracture fixation: locking plate construct ± intramedullary fibular allograft.

BACKGROUND

Locking plate constructs for proximal humeral fractures can fail due to varus collapse, especially in osteoporotic bone with medial cortex comminution. Augmentation, using a fibular allograft as an intramedullary bone peg, may strengthen fixation preventing varus collapse. This study investigated the ability of the augmented locking plate construct to withstand repetitive varus stresses relative to the nonaugmented construct.

MATERIALS AND METHODS

Proximal humeral fractures with medial comminution were simulated by performing wedge-shaped osteotomies at the surgical neck in cadaveric specimens. For each cadaver (n = 8), 1 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 construct collapse or until 25000 cycles were completed.

RESULTS

No augmented construct collapsed. In comparison, 6 of 8 nonaugmented constructs collapsed (P < .05). Collapse in the 6 nonaugmented constructs occurred after an average ±SD of 6604 ± 1984 cycles. Screw penetration of the articular surface was found in only 1 of the nonaugmented constructs.

CONCLUSION

Fibular allograft augmentation increased the ability of the locking plate to withstand repetitive varus loading. Clinically, this may assist proximal humeral fracture fixation in osteoporotic bone with medial cortex comminution.