Peri-prosthetic fractures (PPFs) are steadily rising in number due to population ageing and increased performance of joint replacement procedures. Although PPFs without implant loosening are usually managed by internal fixation, no consensus exists regarding the optimal construct. The primary objective of this study was to compare five constructs, and the secondary objective was to compare sub-groups of mono-cortical screw constructs, with the goal of identifying the method most appropriate for diaphyseal fracture fixation when prosthetic material is present within the intra-medullary canal.

The primary hypothesis was that fixation using bi-cortical screws, i.e., the current reference standard, was superior over other fixation methods. The secondary hypothesis was that adding double cerclage to mono-cortical screw fixation provided the greatest mechanical strength.

Synthetic osteoporotic bone was used to compare five methods for locking-screw fixation of a femoral diaphyseal plate. One method involved bi-cortical screws and four methods mono-cortical screws, with no cerclage wire, a single cerclage wire on either side positioned near or at a distance from the fracture, and two cerclage wires on both sides of the fracture. A complex fracture was simulated by creating a 2-cm diaphyseal gap. Load-to-failure was determined by applying compression loading along the anatomical axis of the femur.

Bi-cortical screw fixation provided greater mechanical strength than did three of the four mono-cortical screw constructs. The exception was the mono-cortical-screw and double-cerclage construct, for which no significant difference was found compared to bi-cortical screw fixation. Thus, mono-cortical screw fixation with double cerclage may be the best alternative when presence of an implant in the intra-medullary canal precludes bi-cortical screw fixation.

The findings from this study have clear implications for clinical practice. The study hypotheses were partly confirmed. The absence of a significant difference between the reference-standard bi-cortical screw fixation method and mono-cortical screw fixation with double cerclage, combined with the results regarding the secondary objective, suggest that mono-cortical screws plus double cerclage deserve preference in patients with an intra-medullary implant. Clinical studies are needed to assess the results of this bench study.

IV, bench study.