Is there any advantage in placing an additional calcar screw in locked nailing of proximal humeral fractures?

Background: The objective of this study was to evaluate the biomechanical effect of an additional unlocked calcar screw compared to a standard setting with three proximal humeral head screws alone for fixation of an unstable 2-part fracture of the surgical neck.

Objective: The additional calcar screw improves stiffness and failure load.

Methods: Fourteen fresh frozen humeri were randomized into two equal sized groups. An unstable 2-part fracture of the surgical neck was simulated and all specimens were fixed with the MultiLoc(®)-nail. Group I represented a basic screw setup, with three locked head screws and two unlocked shaft screws. Group II was identical with a supplemental unlocked calcar screw (CS). Stiffness tests were performed in torsional loading, as well as in axial and in 20° abduction/20° adduction modes. Subsequently cyclic loading and load-to-failure tests were performed. Resulting stiffness, displacement under cyclic load and ultimate load were compared between groups using the t-test for independent variables (α=0.05).

Results: No significant differences were observed between the groups in any of the biomechanical parameters. Backing out of the CS was observed in three cases.

Conclusions: The use of an additional unlocked calcar screw does not provide mechanical benefit in locked nailing of an unstable 2-part fracture of the surgical neck.