The effect of Poller screw or monocortical plate augmentation on the stability of intramedullary nailing in proximal extra-articular tibial fractures: a biomechanical study.

backgroundProximal extra-articular tibial fractures present considerable biomechanical and technical challenges due to the short proximal fragment, the wide metaphyseal canal, and the deforming forces acting around the knee. These factors predispose isolated intramedullary (IM) nailing to malalignment, prompting the use of adjunct reduction aids such as Poller screws or supplemental plates. This study aimed to compare the mechanical behavior of IM nailing alone with that augmented by Poller screws or a monocortical plate in a standardized proximal tibia fracture model.

methodsFifteen synthetic tibiae with an AO/OTA 41-A2.3 extra-articular proximal fracture model were randomized into three groups (n = 5 each): IM nailing alone, IM nailing plus two Poller screws, and IM nailing plus a four-hole medial monocortical plate. All specimens were instrumented with a 10 × 340-mm titanium nail and two proximal and two distal locking screws. Mechanical testing included axial compression to 800 N, axial loading to failure, and torsion at a rate of 25°/min. Displacement, stiffness, maximum load, and torque parameters were compared across groups.

resultsUnder 800 N axial load, the plate-augmented group showed the lowest displacement and highest stiffness (2.40 ± 0.22 mm; 332.4 ± 21.7 N/mm), followed by the Poller screw group (2.48 ± 0.25 mm; 321.6 ± 19.4 N/mm) and the IM-only group (3.45 ± 0.31 mm; 231.8 ± 18.9 N/mm) (p < 0.001). In axial load-to-failure testing, the plate group reached the machine limit (4500 N), while the Poller screw and IM-only groups demonstrated lower capacities (4318 ± 210 N and 3906 ± 265 N, respectively; p = 0.012). Torsional stiffness was likewise highest with plate augmentation (0.30 ± 0.04 Nm/°) and lowest in the IM-only constructs (p = 0.021).

conclusionBoth Poller screw and monocortical plate augmentation improved the initial mechanical stability of IM-nailed proximal tibial constructs, with the plate configuration yielding the highest stiffness values. However, the absolute displacement differences under physiologic axial loads were modest, and the primary clinical role of these adjuncts is reduction control rather than pure stiffness enhancement. Accordingly, the choice between Poller screws and supplemental plating should be individualized based on the fracture pattern, soft-tissue considerations, implant availability, and the surgeon's experience.